# C3 Corvette with Tesla LDU, Need Help!!!



## Maverick 44 (Oct 12, 2019)

Dear DIY ECar Community,

I have been slowly working on my Tesla LDU - C3 Corvette since early this year. My plan is to swap out the rear end, use the Daimen board as motor controller, make a battery box in the front where the engine and transmission used to be, and make a custom control panel in the dash for all the new electronics. Goal is to have this up and running as barebone with 150mil range in 2 years time. I am not making a race car for the track, I just want to build my dream car with electric and I think anything less than a Tesla LDU will be an insult to this beautiful body!
Something like this:








I also have to mention that I only have novel experience on fixing cars, you know like changing oil, sparks plug, mostly hardware... I work on some electronics before like soldering components on circuit boards and troublshooting with a multi-meter. I am pretty hands on so I think I can do it with the DIY & Youtube community (like Electric Supercar & Roadcycler). 
So, I started with a CAD drawing match up of the frame with the Tesla Model-S subframe. Looks like its not to far apart, need to relocate a cross member and make a few mounting points and the real thing is pretty close.















Next on the list is suspension, plan:

Model-S width ~77" and the C3 is 69", this thing is going to be a wide body, which is what I like anyway. And I would like to lower it by a couple of inches too.
tires: copy C6 corvette, F: 245/40R18, R: 285/35R19
coilover for front and back, likely QA1s, adjustable, because I have no idea where the final height is going to be.
need custom shock mounts for the rear, and this is the part I will need help on.
totally no idea on the spring rate... for what I gathered on weight:
 Factory C3 front ~1750lb, rear~1782lb (3550lb total). Engine and Trans ~650lb
If I swap out the Engine+Trans and replace with 14 Tesla battery module (~1000lb), the car would be ~4000lb. 
Front spring like 550lb? rear like 350lb?
- I need to figure out what spring rate I should use for the coilovers... help!!!

I also need to figure out where to weld on the rear suspension mount on the frame.









I have a cardboard cut out of the wheel well space available, and with a paper roll I can estimate that I barely have the space for a 12 inch shock. However, because there is no weight on the suspension, it is very difficult to tell where the "natural" position of the wheel / rotor going to be for me to decide on a ride height.
For those who have done a Tesla LDU swap, what shock / spring / combination did you use? I really need some help to get the right shock / spring combo to begin with. 

Thanks in advance!

Mike


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## ev-swap (Jan 31, 2020)

Hi Mike,
What an exciting project! I love the look of the C3. 
As a kinda/sorta answer to your question about coil overs, have you considered using rockers and mounting the coil overs horizontally? That solves your short height problem (12.5 inches) and allows you a lot of room to play with different coil over lengths and spring rates once you get the batteries installed. There is a guy converting a 72 plymouth Satellite and has the same issue as you. With these older suspensions that used trailing arms and springs, there just isn't much room for a vertically mounted coil over. (I know your C3 uses a horizontal leaf spring instead of coil springs, but the space challenge is the same. So they guy went the rocker route. If you watch his youtube videos, he does a great job of documenting how he built the rear coilover system. Check it out and keep us posted!

Mike






1972 Plymouth Satellite with a Tesla Model S Motor – Engine Swap Depot







engineswapdepot.com


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## MattsAwesomeStuff (Aug 10, 2017)

I missed this somehow from earlier.

Your work looks great.

I haven't seen a lot of people doing suspension modifications on their vehicles around here, so, might not be the best place for advice. 

Please keep us posted!


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## Maverick 44 (Oct 12, 2019)

ev-swap said:


> Hi Mike,
> What an exciting project! I love the look of the C3.
> As a kinda/sorta answer to your question about coil overs, have you considered using rockers and mounting the coil overs horizontally? That solves your short height problem (12.5 inches) and allows you a lot of room to play with different coil over lengths and spring rates once you get the batteries installed. There is a guy converting a 72 plymouth Satellite and has the same issue as you. With these older suspensions that used trailing arms and springs, there just isn't much room for a vertically mounted coil over. (I know your C3 uses a horizontal leaf spring instead of coil springs, but the space challenge is the same. So they guy went the rocker route. If you watch his youtube videos, he does a great job of documenting how he built the rear coilover system. Check it out and keep us posted!
> 
> ...


Thank you Mike, I got the 12inch coilovers from QA1 and a bracket from Ridetech, looks like it may work. The rocker idea is interesting, but will need more work and more room inside the car. I will update later when I got the shocks install. More work on getting a set of wheels with correct offset not to obstruct the shock.


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## DANTM (Feb 4, 2019)

Hi Maverick. I like the idea! Reminds me of starting my own project a couple of years ago only a C5. Looks like using the rear subframe is the way to go on a C3. Good Luck!
I also used the Tesla LDU but was able to separate it from the gearbox and mount it in the subframe. I made a long video if you have time. Search for "The Corsla" on you tube.


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## Maverick 44 (Oct 12, 2019)

Hello Dan, I saw your Youtube video. It was great. What a good idea to split the LDU into 2 and getting it fit onto the original subframe. 
I finally got the suspension bracket welded in and powder coated the frame. I am going to need a wheel with an offset of ~22 to get enough clearance.









Got a question from your video: you mention you used the LG Chem battery and had to reconfigure the small battery packs' series / parallel combination to increase capacity. My understanding is that it will be fix, mixing the series / parallel can change the Voltage and Current, but capacity remain the same. Were you able to see the change?

You also mention you are in the LA area, I am in Ventura, just an hour North. If you don't mind, I may pay you a visit some day!


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## DANTM (Feb 4, 2019)

Nice shocks. I have the same ones up front. As far as spring rate, as long as you have coilovers, you should be in good shape. Springs are easy to change out. For my battery pack I put two of the cells in parallel then put 96 in series. They were about 40-45 AH each so now I have about 80/90 AH cells. Parallel increases capacity with same voltage. BMS just thinks one cell is actually two cells in parallel. 
Question, I know this is the least of your concerns right now, but how are you controlling the Tesla parking brakes? 
I am located out near Murrieta. So a bit outside of the greater LA area to the East. Shoot me an IM if you want to meet up.


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## Maverick 44 (Oct 12, 2019)

I plan to use the e-brake controller by Pantera Electronics.

www.pantera-electronics.com/epbcontroller.htm

I saw this on Roadstercycler on Youtube.


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## DANTM (Feb 4, 2019)

Maverick 44 said:


> I plan to use the e-brake controller by Pantera Electronics.
> 
> www.pantera-electronics.com/epbcontroller.htm
> 
> I saw this on Roadstercycler on Youtube.


I figured. I fabricated a dropout to add Tesla Calipers on my rear hubs. Barely fit but the Pantera controller works great.


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## kstegath (Nov 4, 2008)

*I converted this C3 about ten-years ago.* 
1,200 lb of lead; 600lbs front, 600lbs rear. I used QA1 coil-overs in the front (QA now has springs that fit the upper spring pocket.)








Used lead-acid because it was much cheaper. And I wanted the challenge of cramming 24 batteries in a C3 Corvette.
































*The lead was dead so I started upgrading everything for racing*.
But it didn't feel right hauling an electric race-car to the track with a diesel or gas truck; 
So decided I needed to build an electric tow vehicle
*This 1962 Mack B-46.*


















*The Corvette and Mack are on hold because... *
I got side tracked restoring and converting a clients 1976 Alfa Romeo Spider.
















Flickr pics
Some more Corvette pics


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## Maverick 44 (Oct 12, 2019)

kstegath, that is really great! I saw your Yellow C3 on the web and just love it. One of reason I started my build. 

Great to hear you are planning to upgrade the C3. What's your plan? be interested to hear and learn a bit more. I am in the research phase on the charging and battery system, so it will be great to know what experts are doing.

The Mack looks awesome, it will be quite a sight to see both together. 

Its a funny thing you are working on an Alfa. I used to have a 82 Spider. It was a really fun car to drive. I was thinking to convert one when I am done with the C3, but my wife loves the Karmann Ghia, so it will be the VW next.


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## dallas_ (Oct 23, 2017)

Kstegaath, love the C3 conversion. 
Maverick, I'll be watching your build. I think the C3 is a good option for a conversion. Looks like you're doing it the hard way.


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## joekitch (Sep 13, 2013)

I was originally on the train of using the entire model s subframe but I've since been warned away from that by michael breme of ev west, who said, essentially;
"The model s rear is designed for an almost 5000 pound luxury sedan. Meanwhile, the c3 has a ton of aftermarket for rear suspension handling, and it's not that difficult to weld on some mount points for the model s motor"

So yeah that'll be my approach

That said, I wish I had your CAD and fabrication skills....

Are you going to scan or recreate the underbody fiberglass? It'd be worried about the motor slamming into stuff if all your modeling uses the frame only


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## JJanavs (Sep 6, 2021)

joekitch said:


> I was originally on the train of using the entire model s subframe but I've since been warned away from that by michael breme of ev west, who said, essentially;
> "The model s rear is designed for an almost 5000 pound luxury sedan. Meanwhile, the c3 has a ton of aftermarket for rear suspension handling, and it's not that difficult to weld on some mount points for the model s motor"
> 
> So yeah that'll be my approach
> ...



I'm in the middle of mounting a small Tesla rear drive in a C3 without the subframe. I dropped the leaf spring for a VanSteel coil over set up to make it an easier install and allow for ride height adjustment. The diff mount frame crossmember moved 4" back to be able to raise the motor up to align the Telsa diff as closely as possible to the original half shaft location. That made for a really short rear motor mount, with the front mount close to the original front differential mount. Working out that bracket and the side mount now. The biggest challenge may be the camber strut mount that will need to go under the tesla motor and mount to something...


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## Maverick 44 (Oct 12, 2019)

Hello Janvas,
Are you working on a C3 also? I do have to come up with my subframe mounting points. The ride height is a guess-estimate, especially with the coil over, very likely have to use an adjustable chamber link to get the alignment close. Send some pictures and we can trade notes on the project, still have a lot to do.


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## brian_ (Feb 7, 2017)

Maverick 44 said:


> Hello Janvas,
> Are you working on a C3 also?


Didn't he explicitly say that? Here:


JJanavs said:


> I'm in the middle of mounting a small Tesla rear drive in a C3...


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## brian_ (Feb 7, 2017)

Maverick 44 said:


> I do have to come up with my subframe mounting points. The ride height is a guess-estimate, especially with the coil over, very likely have to use an adjustable chamber link to get the alignment close.


Why is anything about the height uncertain? You know the height above ground of the frame and the hub centres in stock form, and there's no need to change that. The mount design then become an exercise in connecting the drive unit (at the height determined by the axle height) mounting points to the structure (at the stock height)... and moving bits of structure to avoid interference and finding a way to mount the inboard end of the suspension links as required, as JJanavs explained. Well that... and doing something about the axle shafts which are suspension links.


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## brian_ (Feb 7, 2017)

joekitch said:


> I was originally on the train of using the entire model s subframe but I've since been warned away from that by michael breme of ev west, who said, essentially;
> "The model s rear is designed for an almost 5000 pound luxury sedan. Meanwhile, the c3 has a ton of aftermarket for rear suspension handling, and it's not that difficult to weld on some mount points for the model s motor"


That's valid, although the C3 rear suspension is a notoriously poor design. Fortunately, while it's not possible to make a silk purse out of a sow's ear, it is possible to make pretty nice leather purse. 

But then there are the axle shafts...



JJanavs said:


> I'm in the middle of mounting a small Tesla rear drive in a C3 without the subframe. I dropped the leaf spring for a VanSteel coil over set up to make it an easier install and allow for ride height adjustment. The diff mount frame crossmember moved 4" back to be able to raise the motor up to align the Telsa diff as closely as possible to the original half shaft location. That made for a really short rear motor mount, with the front mount close to the original front differential mount. Working out that bracket and the side mount now. The biggest challenge may be the camber strut mount that will need to go under the tesla motor and mount to something...


That all makes sense, but what about the axle shafts? In the C3 design, the axle shafts are suspension links, taking a large portion of the lateral force when cornering. This force is taken by the differential output bearings, something which the Tesla drive unit is not intended to do (no modern final drive or transaxle does this). Are you adding upper links to take this force (using axles with plunge as normal for modern vehicles), or are you using U-jointed axles and expecting the Tesla drive unit to take this force?


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## Maverick 44 (Oct 12, 2019)

brian_ said:


> Why is anything about the height uncertain? You know the height above ground of the frame and the hub centres in stock form, and there's no need to change that. The mount design then become an exercise in connecting the drive unit (at the height determined by the axle height) mounting points to the structure (at the stock height)... and moving bits of structure to avoid interference and finding a way to mount the inboard end of the suspension links as required, as JJanavs explained. Well that... and doing something about the axle shafts which are suspension links.


The ride height uncertainty is mainly from the difference I found in the CAD model I downloaded from the subframe and how to chose the rear coil-over spring force (the whole back end weight is different now and I don't even know what it would be...) and finally, I want to lower the car to have a more aggressive stance.


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## Maverick 44 (Oct 12, 2019)

brian_ said:


> That's valid, although the C3 rear suspension is a notoriously poor design. Fortunately, while it's not possible to make a silk purse out of a sow's ear, it is possible to make pretty nice leather purse.
> 
> But then there are the axle shafts...
> 
> ...


My knowledge on handling is limited. I don't plan on taking the car to the track, just normal highway driving, doing anything the Model-S can do. So, I think installing the whole Model-S subframe with all the suspension is the best bet, there's shouldn't be too much difference besides the weight and distribution. Something similar to what Roadstercycle had done on his Tesla swap Mustang on Youtube did: (1) Roadstercycle - YouTube


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## JJanavs (Sep 6, 2021)

brian_ said:


> That's valid, although the C3 rear suspension is a notoriously poor design. Fortunately, while it's not possible to make a silk purse out of a sow's ear, it is possible to make pretty nice leather purse.
> 
> But then there are the axle shafts...
> 
> ...



I'm no engineer, and this is my first vette... I've read similar concerns in threads about changing the half shafts to CV shafts since they have a lot more axial play, but VanSteel said there wouldn't be any issues changing to CVs and using their coil-over rear. I'm not quite sure. Racevette makes a bolt in 6 link that, of course is fitted to a standard diff, but could be potentially adapted to work idependantly from the Tesla unit. Although it looks tough, I'm not sure I want to try to make the Tesla case a structural component of the suspension.


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## brian_ (Feb 7, 2017)

Maverick 44 said:


> The ride height uncertainty is mainly from the difference I found in the CAD model I downloaded from the subframe and how to chose the rear coil-over spring force (the whole back end weight is different now and I don't even know what it would be...) and finally, I want to lower the car to have a more aggressive stance.


I would think of that as choosing coils (length and stiffness) can be a challenge, rather than choosing ride height. You might need to wait until very late in the build to finalize the coil choice, or to be prepared to buy a second set at the end to get it right.

There will be a range of height that works for suspension geometry; as soon as the appearance of the "stance" becomes a factor I think good design goes out the window, and you're making a sculpture instead of an automobile... but to some people that is what they want to do, which is their choice.


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## brian_ (Feb 7, 2017)

JJanavs said:


> I'm no engineer, and this is my first vette... I've read similar concerns in threads about changing the half shafts to CV shafts since they have a lot more axial play, but VanSteel said there wouldn't be any issues changing to CVs and using their coil-over rear.


That's complete nonsense, unless the Van Steel kit changes more than the springs and shocks. There is zero axial play permissible in a suspension like this that uses the shafts as control links, and even with no play the parts (of the axle shafts and the differential and its case and mounts) need to take about half the weight of the car in axial force, not to just have no play.

Van Steel has various coil-over conversion kits, but they don't change the lateral location design so they would not be workable with CV joints. They were probably referring to their Six Link Suspension Kit, which adds top links to replace the locating function of the axle shafts, and would be needed in addition to a coil-over conversion.



JJanavs said:


> Racevette makes a bolt in 6 link that, of course is fitted to a standard diff, but could be potentially adapted to work idependantly from the Tesla unit. Although it looks tough, I'm not sure I want to try to make the Tesla case a structural component of the suspension.


I wouldn't want to use the Tesla drive unit case structurally, either... both because the case is not designed to do that, and because the Tesla mounting bushings are completely wrong for taking lateral force (because in the Tesla they take none of the lateral force required to push the rest of the vehicle around a corner). A complete suspension system replacing the stock design is certainly a solution - we discussed one of these systems in another C3 conversion thread:
_Rate my build plan (c3 corvette)_
Detroit Speed DECAlink IRS

The Dragvette 6-Link and the similar Van Steel kit make sense to relieve the axle shafts of suspension load, except that of course they still use the final drive case structurally... and the name doesn't make sense (an IRS is described by the number of links _per side_, not in total - these are three-links, more conventionally described as a multi-link with trailing arms and lateral control links). You could custom-build something that adds top links like this system, but anchors them (and the stock lower links) on a custom subframe.


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## remy_martian (Feb 4, 2019)

To further Brian's point, the only thing holding a Tesla half-shaft in the housing is a spring loaded snap ring. A gentle whack with a slide hammer pulls the shaft out of the case. 

There is NO way you'd make it around the first corner, with the way the Tesla axles are retained, using a C3 suspension that uses its halfshafts to locate the spindle.


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## JJanavs (Sep 6, 2021)

brian_ said:


> That's complete nonsense, unless the Van Steel kit changes more than the springs and shocks. There is zero axial play permissible in a suspension like this that uses the shafts as control links, and even with no play the parts (of the axle shafts and the differential and its case and mounts) need to take about half the weight of the car in axial force, not to just have no play.
> 
> Van Steel has various coil-over conversion kits, but they don't change the lateral location design so they would not be workable with CV joints. They were probably referring to their Six Link Suspension Kit, which adds top links to replace the locating function of the axle shafts, and would be needed in addition to a coil-over conversion.
> 
> ...


Brian, Thanks for the reference to the earlier thread. I had looked at Detroit Speed's DECAlink as well as Ridetechs rear upgrade. Both mount right where the Tesla motor needs to be, so any way you go about it, this has to be a one off solution that allows for top links. I knew this wasn't going to be easy...


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## joekitch (Sep 13, 2013)

the ridtech rear strongarm setup along with some custom work for mounting the cross links is in my particular future (both top and bottom not mounted to the motor casing, more likely a bit of frame surrounding it)









RideTech 11537199 Rear Strongarm System, 68-79 Corvette


RideTech C2/C3 Rear StrongArm SystemThe rear suspension system utilizes an offset trailing arm with a "trussed" design which allows maximum tire width while providing the utmost in strength. The rear trailing arm is outfitted with a rubber bushing in the standard configuration to mitigate NVH...




www.speedwaymotors.com














the decalink rear is probably a better move but it's far more expensive and also seems to have a lot more going on, aka, less room for the motor to fit inside it all


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## JJanavs (Sep 6, 2021)

joekitch said:


> the ridtech rear strongarm setup along with some custom work for mounting the cross links is in my particular future (both top and bottom not mounted to the motor casing, more likely a bit of frame surrounding it)
> 
> 
> 
> ...


I had considered this set up also, but decided against it because the top cross bar and coil-over support, installs on the old differential top mounts which is right where you want to tuck the motor up as high as possible for alignment with the spindles. I don't think this set up provides the top link for the suspension that is originally provided by the half shafts in the stock rear end, so that needs to be worked into the installation as well. I used Racevette's 6 link, actually a 4 link as Brian noted, and mounted it on a removable cross bar for the upper struts. Now I need to fabricate a support structure for the original bottom struts. I'd love to see install photos if you go this way.


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## joekitch (Sep 13, 2013)

keep forgetting this thread exists

but I'm into way more uncertainty in suspension land, turns out getting rid of the c3 suspension's tendency to plunge the axel shafts is insanely difficult
and doing some more cad modeling, I'm realizing that yes this thing needs to be tucked way the hell up into the car in order to align with the axels, meaning there's almost no room above for a top link

i got a thread over on the c3 forums about this
Redesigning the rear suspension; making the half shafts NOT a control element? - CorvetteForum - Chevrolet Corvette Forum Discussion 

also, the plymouth electrolite solved the shock mounting problem by going with a cantilevered spring. According to him it's way easier than he expected, he just needs to keep all the lengths consistent and make the hardware beefy enough









edit: nevermind this is literally the second post in this thread
cantilever for the win?


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## brian_ (Feb 7, 2017)

joekitch said:


> ...
> also, the plymouth electrolite solved the shock mounting problem by going with a cantilevered spring. According to him it's way easier than he expected, he just needs to keep all the lengths consistent and make the hardware beefy enough
> 
> 
> ...


I think most rocker suspensions are built because they look cool, not for any valid technical reason... but yes, they work. Wouldn't the hardware that is in the trunk of the "plymouth electrolite" be in the interior of the Corvette?


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## joekitch (Sep 13, 2013)

yeah, that's the rub, right above the rear diff is essentially the interior of the car, the cargo area letterbox thing, since the vette doesn't have a trunk
on the subject of strange coilover geometries, the sharkbite rear does some wacky stuff with the extremely tight space



https://www.speedshopstore.com/speed-direct-780-86557-shark-bite-corvette-1963-1977-rear-coil-over-suspension.html












also, on the subject of the dragvette 6 link (really 3 link) using the diff casing as a major member, this fellow over on vettemod developed a setup which uses the diff carrier cross beam thing instead, which is potentially very relevant
http://www.vettemod.com/forum/showthread.php?t=7705











also, random ancient video of the 6 link going through its range of motion


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## joekitch (Sep 13, 2013)

Random brainstorm but rocker suspension might solve the short shock and weird shock tower problem;

If, op, you essentially replace the shock there with a shorter pushrod, and weld a rocker right to the top of the frame rail, then have the shocks facing eachother going across the frame, you get way more possible coilover length but the ability to adjust them goes way down since they'll be sitting above the subframe...

Hopefully I'm describing that alright


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## JJanavs (Sep 6, 2021)

joekitch said:


> Random brainstorm but rocker suspension might solve the short shock and weird shock tower problem;
> 
> If, op, you essentially replace the shock there with a shorter pushrod, and weld a rocker right to the top of the frame rail, then have the shocks facing eachother going across the frame, you get way more possible coilover length but the ability to adjust them goes way down since they'll be sitting above the subframe...
> 
> Hopefully I'm describing that alright


I'm addressing the Corvette rear suspension issue by combining Racevette's 6 (4) link set up with a bottom link support similar to Detroit Speed's Deca link. The attached pictures are just a tack welded mock up, nearing completion. My concern at this point is the range of motion for upward travel in the suspension. The crossbar that carries the upper link is 1/2" shorter than the old bump stop on the frame so any bump stop I put in will have limited cushion. The frame bolts to the front motor mount at the original front diff mount location and the rear to the cross frame. I am slowly posting progress on all aspects of the build on instagram @electricc3 Would love to get your thoughts on the solution.


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## joekitch (Sep 13, 2013)

Man, the electric C3's are comin' out of the woodwork here, thought I was the only one six months ago.

Is that the small rear drive unit by the way? I'm now wondering how well or poorly an LDU would fit with that setup, but that's a really slick design.


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## JJanavs (Sep 6, 2021)

joekitch said:


> Man, the electric C3's are comin' out of the woodwork here, thought I was the only one six months ago.
> 
> Is that the small rear drive unit by the way? I'm now wondering how well or poorly an LDU would fit with that setup, but that's a really slick design.


That is a small drive unit. I think the LDU would fit fine. It has the same mounting points as the small drive. In fact, it might work better since one problem with the small drive is that the differential oil heat exchanger hangs over the left side output shaft and interferes with the top link on the left side. So I'm making adapter plates with hose fittings to move the heat exchanger to a remote location on the right side.


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## joekitch (Sep 13, 2013)

I keep coming back to the ridetech solution....









1968-1979 C3 Corvette - Rear StrongArm System


Our rear StrongArms system uses fabricated trailing arms and new crossmember to both strengthen the rear suspension and provide mounts for the Coil-Overs and MuscleBar.



www.ridetech.com





But, to confirm, you'd need to fab up an extra top link and an extra arm going over the axels right? Like the dragvette system does? To prevent any lateral play in the half shafts? Or is that unnecessary with this geometry?

It just seems like you can skip the diff cross beam problem by welding something way up in there as a rigid beam for the top of the shocks to mount to, I don't think the shocks need to be mounted to something with a bushing on it? 

Here's a post of this system installed, I would be a little concerned about the LDU hitting the coil springs since it's so dang wide






New Project: Dropping the Rear Suspension and Installing the Ridetech System - CorvetteForum - Chevrolet Corvette Forum Discussion


C3 Tech/Performance - New Project: Dropping the Rear Suspension and Installing the Ridetech System - After coming to the realization that the 700-horse Vortec Supercharged engine that we built needs more rear tire than the stock Vette suspension will allow, we decided to drop the rear suspension...



www.corvetteforum.com


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## brian_ (Feb 7, 2017)

joekitch said:


> I keep coming back to the ridetech solution....
> 
> 
> 
> ...


Correct - that setup provides only the trailing arms, lower lateral links, and coil/shock mounting structure; it still depends on the half-shafts to work with the lower lateral links for both lateral location and camber control. It does not change the stock geometry.

To relieve the half-shafts of any locating function, upper lateral arms would be required.



joekitch said:


> It just seems like you can skip the diff cross beam problem by welding something way up in there as a rigid beam for the top of the shocks to mount to, I don't think the shocks need to be mounted to something with a bushing on it?


Right - you just need strong enough fixed structure, which can be solidly mounted to the frame.



joekitch said:


> Here's a post of this system installed, I would be a little concerned about the LDU hitting the coil springs since it's so dang wide
> 
> 
> 
> ...


Yes, the shocks lean in enough to be a concern. I'm guessing that there isn't enough height available to stand them upright.


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## JJanavs (Sep 6, 2021)

joekitch said:


> I keep coming back to the ridetech solution....
> 
> 
> 
> ...



Joe,
The reason I don't think the Ridetech works is because it mounts on existing differential top mounts and the frame cross member with those mounts already needs to move backwards about 4" to provide clearance for the motor to mount as far up as possible. You can see just how little clearance there is in my install in every direction. I used the VanSteel coil-over set up because it used the stock shock mounts not the top crossbar that RideTech uses.

Aside from the possible clearance issues from the coil-overs leaning in, you'd have the Tesla motor some 4" lower than what I show in my pictures. That would lower the cradle that carries the bottom struts too. I don't know offhand what the ground clearance of the Vette frame is at the differential front mount, but right now my rig, with the motor up within 1" of the body, is even with the lowest point in the frame. I don't think you can give up 4" of ground clearance.


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## joekitch (Sep 13, 2013)

Oh, thing I only just realized reading that, need to get the dragvette 6 link AND the ridetech coilover trailing arms, for some reason I thought the dragvette thing came with coilovers but obviously that is not a thing

On the plus side this is the kind of upgrade I can do while it's still a gas car, hopefully making the rear end nicer on the street.

Just wish there was a multi link rear setup which was really great at performance street driving (dragvette isn't really designed for this) that removed the half shafts from being suspension members and didn't cost freaking $5k plus


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## remy_martian (Feb 4, 2019)

C5 cradle with a yoke on the diff...


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## joekitch (Sep 13, 2013)

Maverick 44 said:


> Dear DIY ECar Community,
> View attachment 120546


im not sure how i missed this several times but, where did you get this tesla suspension model from? i'd very much like a copy of that (i assume its an stl)


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## joekitch (Sep 13, 2013)

As for the pushrod suspension idea, I've found a few examples of linear mounting, I'm thinking of mounting something to the frame rails going towards the rear of the car (there's a decent bit of room back there).
that should give you full suspension travel but also allow for much better, longer coilovers


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## remy_martian (Feb 4, 2019)

Now, what would be really interesting is to pushrod the Tesla air suspension....

Kevin Erickson (Project "Electrollite") on Youtube goes into his pushrod setup for the electric Plymouth Satellite he's built:


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## joekitch (Sep 13, 2013)

Oh shit, looks like EV west is making a bolt in rear subframe for the c2 Corvette which is almost identical rear end to the c3

Apparently it'll have mounting points for upper and lower control arms so it gives the c3 a true multilink rear in addition to holding the drive unit 


__
http://instagr.am/p/CcNFOe5hGe9/


__
http://instagr.am/p/Cb0yhzwvanC/

However it seems to only support the small rear drive unit, on the c2 the LDU is too big and may need the rear body area cut up (bad). But I'm pretty sure the c3 has more vertical cavity than the c2 back there so LDU may not need cutting....?

Also their design is bolt in only, no welds or cuts, which I don't have qualms about tbh.

Honestly if I could just get a camera fly around of their design I could probably make something in CAD for c3 and get it cnc'd, probably not as good as theirs but it'll at least put me in the right direction


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## kstuck (May 1, 2014)

Great project!

Love the C3 Corvettes.

Any chance you would share your CAD model of the cradle, LDU etc?

Thanks and I will be following your progress.


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## JJanavs (Sep 6, 2021)

joekitch said:


> Oh shit, looks like EV west is making a bolt in rear subframe for the c2 Corvette which is almost identical rear end to the c3
> 
> Apparently it'll have mounting points for upper and lower control arms so it gives the c3 a true multilink rear in addition to holding the drive unit
> 
> ...


Looks like it hangs really low. I'd like to see how they addressed the strut mounts on the other side.


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## remy_martian (Feb 4, 2019)

Don't think it's low at all. Look at the drum relative to the front wheel. Also appears to be compressing the left rear with the jackstand and the coilovers are clearly not attached as yet.










I think the suspension is bottomed out and the clearance is adequate for a blown out tire, riding on rims.


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## UglyCarFan (8 mo ago)

joekitch: after having done your C3, what would you do differently if you were to do another? I'm curious about your impressions of how suitable the C3 is for EV conversion. I've owned small and big block versions of them back in the 70's. Also had some 63's. My 68 would probably seem really crude by today's standards, but might the EV conversion alter that impression?
My buddy has a 68 big block/4speed sitting in the corner of his shop that hasn't moved in years. Convertible. What scares me about a project like that is that around here, there is almost no one who will do the bodywork. I'm not interested in learning how to do fiberglass. This particular one has the typical hairline cracks at the bonding point on top of the right fender. But no frame rust.

It seems to me a Lexus gs450h would be perfect for this. Sell off the big block, and the removable hardtop. Or a Leaf with an adapter to a TorqueTrend box. (sp?)


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## Roadstercycle (Jun 26, 2019)

HI guy's, I thought I would pop into this for a quick minute. I'm looking at 1973 Corvette to do a LDU conversion and I am definitely going to go with a Model S sport rear full suspension. Although someone mentioned that the rear of a Tesla Model S was built for a 5000 pound car. It's still all aluminum and very up to the task of being a daily street machine or a track car. You just have to use the right coil overs and tune for the ride you want. The sway bar is good. It may be 10 pounds more than a custom built or bought suspension but a Model S motor will not care in the least. The Mustang GT that I built has the whole Model S suspension with a couple of adjustable rods for rear wheel alignment. The next big thing I would suggest is NOT using Tesla batteries. They are way too heavy when you put 400 volts worth in a sports/small car. A 42 Kwh battery is half the weight and gives you over 100 miles of range. Plenty for melting tires or weekend fun. My other Musktang with the M3 motor gets me about 140 miles. If I remember correctly a full set of Tesla batteries is about 850 lbs. (Correct me if I'm wrong). No reason to have all that weight being dragged along in a fun car. There's no trophy for mileage unless your a car manufacturer. Keep them light and keep them fun. This is just my 2 cents after building a few.


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## UglyCarFan (8 mo ago)

Roadstercycle: interesting comments. The Tesla rear seems to be a well designed package, and would no doubt be far better than the C3 suspension. Personally, I don't want to do a Tesla, mainly because I'd like to be able to change up the design later if I wasn't happy with what was installed. Or, a future owner might want to put back the original type engine. (Doubtful) I agree with you regarding the batteries.


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## joekitch (Sep 13, 2013)

EV west is making a c2 Corvette multilink rear suspension and model s small rear drive unit mount that's bolt-in. I'll be buying that and adapting it for the c3, that's probably going to be the best solution out there.

Right now I'm stuck on the battery problem. Turns out getting to 400v with less than 500lbs of pure battery, but still having a high C rating for high horsepower, is hard. 
Volt gen 2 modules are pretty heavy (800lbs for 36kwh)
Chrysler Pacifica hybrid batteries are now too rare and too expensive for what you get
Oxdrive Power batteries will cost $14000 for like 42kwh although they are relatively light
There just isn't a good solution right now. Maybe those BMW hybrid batteries....?


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## remy_martian (Feb 4, 2019)

What do you want out of the car? Speed or acceleration? 

A street sports car can easily get by on ~500lb of battery. imo, the reality is you don't need more than 90-100MPH in a street car.


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## joekitch (Sep 13, 2013)

Yes but the problem is getting to 400v with only 500lbs of battery, the vast majority of junkyard batteries are designed to only hit 400v with the entire pack in series (meaning, 800+ lbs, before even accounting for cooling), so using half of that means not enough voltage


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## remy_martian (Feb 4, 2019)

Your brain is stuck in a box, which keeps you from thinking outside one.

You avoided my questions with 400V blah blah blah which is irrelevant. What is the car for? How will it be used 95% of the time? What motor is in it?


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## joekitch (Sep 13, 2013)

Oh! Tesla large drive unit, high horsepower and don't really need range (100 miles is fine), might even throw it onto autocross. So my goal is high voltage high C rating with as little weight as possible but still getting to like 36kwh capacity, but it being not crazy expensive would be nice


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## remy_martian (Feb 4, 2019)

Blah blah blah again.

95% of the time, what do you expect out of the car? "Might throw into" is not a grownup way to spec a project.

Track car?

Street car?

Acceleration?

Speed?

You can't have "all of the above", which is why you have no hair left searching for a battery.

Time to face reality...to build a P100D you need to build a 5000lb car.


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## UglyCarFan (8 mo ago)

joekitch said:


> Oh! Tesla large drive unit, high horsepower and don't really need range (100 miles is fine), might even throw it onto autocross. So my goal is high voltage high C rating with as little weight as possible but still getting to like 36kwh capacity, but it being not crazy expensive would be nice


 joekitch: The BMW modules I've purchased tend to be 33v or 66v fully charged, about 33#, net around 2 kwh each. They have those un-obtainium connectors. Or, more correctly, I should say that none of mine came with them...darn. I do have a few larger units that are 12s, but they are really heavy. About 2.7 kwh if I remember correctly. Those did have the connectors. I missed out on buying a complete battery pack of those a year ago, literally as I was a few seconds away from hitting the "place order" button.

Have you looked at the modules Battery Hookup is selling now? The Ford LG units? Those are powerful, and reasonably priced. They still have the 8S4P and the 10S3P. I have no idea how those would fit in a Corvette, but would like to know that answer.


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## floydr (Jun 21, 2021)

The 10s4p 11.95kWh SK Innovation looks interesting too. if you could reconfigure the battery pack to 20S2p or 40s1p
5 modules needed if configured to 20s2p 100S2p 360V nominal 55.75kWh . Dimensions 24" x 15" x 5". 3 modules 120s1P 432Vnominal 35.85kWh.
Later floyd


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## Roadstercycle (Jun 26, 2019)

Look at Electric GT batteries. I'm running 400 volts, about 450 lbs. 16 modules about 42 Kwh. They drain like a firehouse, Tesla batteries drain like a 3/4" garden house. That's how I explain C rating by the way.


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## joekitch (Sep 13, 2013)

Oh damn that sounds about perfect for my use case actually. I'm guessing you get away with it because the nominal on the gt is 800v so you just use half the pack. Do those play nice with an Orion BMS?

Actually, where did you even find those batteries? Off eBay or a wrecking yard?


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## Roadstercycle (Jun 26, 2019)

OK, I meant the company Electric GT in Huntington Ca. Electric GT - Electric Vehicle Systems and Components. You can configure what you need. Like I said, I have 16 modules in series. I use the AEM BMS because I'm a dealer for them and we set up my car with them. They are not yet available to the public yet from what I understand. The Orion is also a great way to go, just lots of long wiring.


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## joekitch (Sep 13, 2013)

Ah damnit, of course.
The problem with those is you need 8 of the big 5.33kwh power modules for 980 peak amps, and each of those is $1900 each. Meaning a $16000 pack that only has 42kwh in it which is....... extremely steep. Unless I'm reading these charts wrong. This is even before any battery chill plates or enclosure costs


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## Roadstercycle (Jun 26, 2019)

I didn't say they were cheap, I just said they work and much lighter than a 400 volt Tesla pack and they are new and they fit in tight places much better. Tesla packs are just so darn big and heavy. So right now used Tesla packs are about $1100 each and I believe 16 are in order which is $17,600. Yes you get about 40 extra Kwh and 400 lbs of weight to lug around. If you are a building something for long range I agree with the Tesla thought. If you are building a tiring burning weekend warrior well you have to weigh the options. Just throwing options out there.


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## joekitch (Sep 13, 2013)

There's a few other potential options but they have question marks

The big one being those BMW hybrid batteries. Presumably they have a high C rating and instant peak amp discharge because, well, 400v hybrid, but it's hard to say until someone does real testing with them behind a performance drive unit


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## remy_martian (Feb 4, 2019)

The BMW batteries are refrigerant-loop cooled...


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## UglyCarFan (8 mo ago)

This is a great example of the effects of making specific choices. Speaking only for my situation, I would never buy a Corvette coupe, unless it was a 63 or 67. I've owned a total of 4 Corvettes, and never burnt up any tracks with them, even when I was in my early 20's. A/C? bah......put the top down. Rain? Put the top up and go home. Removable hardtop option? For what? I drove mine in the snow too.

Now, I'm trying to decide what to build for my use. We have so many pot holes and crappy roads here that you cannot drive 20' anywhere without hitting one. Although I've owned 6 motorcycles, you couldn't give me one now for that reason. I WOULD use my car for cruising, going out for a leisurely drive, and stop at a favorite burger place with my lovely wife. If that was in a Corvette, it would be a convertible. (She hates Corvettes) But now, I'd want a/c even with top down. You know, global warming?

I like those BMW batteries, and if I had to choose between a refrigerant based cooling system, or pumping fluid...I'd be torn. I have tons of experience with pumping, so that would be easy for me. But I suspect I'd like the BMW approach better. I'm trying to get educated on electric compressors right now.

It is really interesting to read about all the work to put a Tesla "anything" under the rear of a C3 or similar car. I especially like the ingenuity of how some people have built modified suspension like that one in the Satellite. Wow, very clever. But would I use them? No. I had to laugh when I read the joekitch comment about 300 not being enough for a proper American sports car. I get pissed off just driving to the hardware store a few blocks away due to road conditions, and drivers who are texting, or watching movies. I cannot risk driving over 35 to do that.

What I would like to see/read about is a sensible conversion that deals with some of the C3's problems, especially those related to age, frame flex, etc. Maybe some alternatives, like putting a Lexus 450h unit in there, for those of us who don't want to race. I liked Brian's comment about the Bolt motor being a possibility. How about a TorqueBox? Selfishly, I'd like to know more because I can pick up a '68 rag-top with big block and 4 speed, and removable hardtop. It is parked in one of my best friends shop, in his way. I could own it today if I chose to. Last night, I was thinking about the 63 split window, and roadster I used to own..I was on the lookout for years for the rare optional 36 (?) gallon gas tank that took up the storage area in the back. Only saw one, ever. At the annual Bloomington show and swap meet. And that was in a car I could never afford. The point being, that space was worthless to me then, and even worthless today. I would not hesitate for a minute to sell off even the rag-top frame, and use all the space behind the seat in a C3. In fact, the very point being that if I sold off a lot of the 68 parts, I'd drive cost of the car down to a very low level. Then it would be easier to think about things like $4k suspensions mods. 

Please everyone, don't take offense to any of my comments. I think most of these projects are truly great, and are very entertaining to read about.


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## joekitch (Sep 13, 2013)

The EV west c2 Corvette they're building for Tony hawk kind of does that, they're using a small rear drive unit that's good for ~300 hp

Also, if you want something cool but comfortable on bad roads, you could look into the so called "safari" approach. Check out a safari 911 and you'll see what I mean. The goal with those is to make something with a lot of suspension give and meaty tires ostensibly for rally stage but it also works great on crappy pavement. Also it looks cool


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## UglyCarFan (8 mo ago)

joekitch: thanks for the great suggestion! That was very interesting reading, and it makes a lot of sense. Practical. I'm not at all exaggerating about how bad the roads are here. I've traveled all over the world, and have been in very few places where the roads as so consistently bad. I've put 200,000 miles on a lot of cars, and in many never had to do any serious suspension work. Now, it is every 2-3 years. The components are worse quality, and they take a constant beating. 

By the way, I made an offer on the 68 C3 today. We will see what comes of it.


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## joekitch (Sep 13, 2013)

Basically, do this, but with a c3 Corvette






Here's some inspo









1969 Corvette Beach Buggy Hides a First-Gen Hemi Surprise


Daily Slideshow: One part Chrysler, one part Caddy, and two parts C3 Corvette, this 4WD beach buggy gets it done....



www.corvetteforum.com


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## UglyCarFan (8 mo ago)

That Corvette is bizarre. Can't say I like it. But the concept of raising a vehicle a bit and putting a more rugged suspension and wheels etc in it is great. Like the 911 you linked to before. A lot of people would just comment to go buy a Subaru, a Meyers Manx, what-ever. For me, the attraction is modifying a car whose design you already like. The Honda Element would be an obvious candidate for this.


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## JJanavs (Sep 6, 2021)

While on the subject of C3 Vette batteries, I went through all these debates and ended up coming back to Tesla modules. I just finished roughing out most of the high voltage side of things. I'd love to have some thoughts from our experienced moderators on the wiring and layout. Don't really know what gauge wire to use for each segment and what else I might be missing. I've seen so many variations on how things are wired for different cars. I built this as a 3D model so I could really know how things fit since the Vette is a super tight package, which doesn't make for easy sharing of a wiring diagram, but makes more sense in my head. Not pictured is the charger which I'm thinking will be at the back of the car. I'd appreciate any insight on how to do this, do it better, etc. Thanks!


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## joekitch (Sep 13, 2013)

I am.... extremely impressed you managed to packaged that many tesla batteries into the engine bay, that's 14 modules right? Doesn't that only get you 320 volts? Is that enough to drive a small drive unit?

Don't forget to account for cooling routing/manifolds btw


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## JJanavs (Sep 6, 2021)

joekitch said:


> I am.... extremely impressed you managed to packaged that many tesla batteries into the engine bay, that's 14 modules right? Doesn't that only get you 320 volts? Is that enough to drive a small drive unit?
> 
> Don't forget to account for cooling routing/manifolds btw


14 modules between front and back. Took lots of foam core tests. I could put two more in the rear but was staying away from the extra weight since I'm told we can run with 320v. I'm thinking I'll cool the front pack off a large stock front radiator, and the motor, charger and small rear pack off a second rear mounted unit. There are effectively three packs in this set up. I broke the front into two for handling reasons.


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## remy_martian (Feb 4, 2019)

Good weight distribution, though the 7 wide (375lb) seems to be riding a bit high for cg.

But, with steering box etc, you can't have everything.

Nicely done.

I'd consider a second pre-wired "expansion" pack of two more series modules that quick-mount and quick connect in the trunk when you don't need the space for golf clubs or the six bags of groceries you can get into a stock 'vette trunk.

Depending where you live you may need module warming more the cooling...


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## UglyCarFan (8 mo ago)

Janavs: Nice work, looks good.

I'm looking at the Ford/LG batteries currently still being offered at Battery Hookup. I'm wondering if they can be mounted on edge, or if that might affect their performance.


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## remy_martian (Feb 4, 2019)

As long as the cells are not horizontal, bearing each others' weight, it shouldn't matter.

The problem with edge, though, is you don't get chiller plate clamping force assist by gravity.


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## brian_ (Feb 7, 2017)

joekitch said:


> .... that's 14 modules right? Doesn't that only get you 320 volts? Is that enough to drive a small drive unit?


All Tesla configurations were 14 of these 6S modules for the first few versions - they only went to 16 modules to fit in more capacity.


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## JJanavs (Sep 6, 2021)

remy_martian said:


> Good weight distribution, though the 7 wide (375lb) seems to be riding a bit high for cg.
> 
> But, with steering box etc, you can't have everything.
> 
> ...


It's as low as I could package in this tight frame. I'm in LA, so warming is automatic. If you really want to make a C3 corvette a great conversion, I think you'd want to make a custom frame so you could do a flat pack underneath for at least 8 of the battery requirement and address the rear suspension at the same time. Next time...


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## UglyCarFan (8 mo ago)

joekitch: I'm back on this again. Have a complete BMW battery coming tomorrow. The aluminum cased, 21 kwh version with the (8) 2.7 kw 60ah modules,and the cooling tray on the bottom. I happen to have a couple matching, spare modules too. Probably not enough to do a decent C3, but could be a start. I also bought the pack because they do make good solar backup cells, and if I went that way, I already the 12s BMS'es.

I have to make a decision ASAP on the '68 here Vette roadster, 427, 4 speed) It has been offered to me for a fair price. I like your comment about the small Tesla unit, and the EV West kit. Looks promising.

In other news, a neighbor who unfortunately has advanced cancer has offered me a cute little '48 Crosley sedan on a stretched Model A frame. No motor, no tranny. Ford 9" rear. $1200. Can't beat that, and the thing probably weighs 700 pounds right now. Thought about getting an electric axle set up from a Toyota, and doing something simple and very, very light. My wife saw a picture, and said "what a cute clown car"! I took that to be a positive...


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## UglyCarFan (8 mo ago)

floydr said:


> The 10s4p 11.95kWh SK Innovation looks interesting too. if you could reconfigure the battery pack to 20S2p or 40s1p
> 5 modules needed if configured to 20s2p 100S2p 360V nominal 55.75kWh . Dimensions 24" x 15" x 5". 3 modules 120s1P 432Vnominal 35.85kWh.
> Later floyd


Floyd have you seen the 6kwh VW modules they have right now at Battery Hookup? Very interesting.


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## joekitch (Sep 13, 2013)

Could do a budget conversion on the second car, slap a cheap motor on the transmission and scrounge up some cheap batteries

As for those BMW batteries I no longer need em, got a set of 18 Pacifica modules sitting on a plywood slab in my garage


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## UglyCarFan (8 mo ago)

joekitch said:


> Could do a budget conversion on the second car, slap a cheap motor on the transmission and scrounge up some cheap batteries
> 
> As for those BMW batteries I no longer need em, got a set of 18 Pacifica modules sitting on a plywood slab in my garage


Yeah, that is the attraction for the Crosley. I already have many, many batteries that would work just fine for that car. Would probably use my A123 7s military batteries, or maybe some BMZ. (Not BMW) The most attractive thing about it is that it already looks like a ratrod, so what the heck. Do what you like. I'm still hoping my buddy sells me the 59 El Camino for a fair price, in which case I'd forget the Vette completely. Probably..


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