# Help with calculations on modest requirement build



## cyberpine (Mar 25, 2010)

I've been talking the gear heads on a Chevy forums they feel flipping the rear axle would have some serious challenges. I still want to go without a transmission and have some support that my 8.5 to 1 ratio Rear end might not need to shift if the motor is a high RPM motor. I guess I am wondering if I go with an 11 inch diameter used DC forklift motor direct drive right in front of the rear differential on my S10 Blazer, Can I fit enough Lithium batteries in the engine bay to get my modest 40 mph/ 40 mile range requirement?

check this out: 

YouTube search "Torquetrends 2:1 Direct Drive for EVs" (and skip to 17:41)

https://youtu.be/WX6Xhl-SP9Q?t=1044


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## Duncan (Dec 8, 2008)

Hi No Sun

11 inch forklift motor driving the diff and Chevy Volt battery pack
That is what I have on my "Device"

https://www.diyelectriccar.com/foru...dubious-device-44370p15.html?highlight=duncan


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## cyberpine (Mar 25, 2010)

Duncan said:


> Hi No Sun
> 
> 11 inch forklift motor driving the diff and Chevy Volt battery pack
> That is what I have on my "Device"
> ...


your rig looks very light though. what it weigh? Have specs on your motor and battery?


Im wondering if that motor with 10wkh pack can push 3000lbs for 40 miles and do 40mph?

BTW, anybody know what 10kwh of lion weighs?


Thanks.


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## jonescg (Nov 3, 2010)

That Blazer is a lightweight rig for its age. 

10 kWh of Li-ion can weigh anywhere from as high as 115 kg and as light as 55 kg. By the time you add all the framework, enclosure, conductors and contactors it might be as much as 10 or 15% heavier.


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## brian_ (Feb 7, 2017)

NoSunBeach said:


> Shell No ICE weight = ~2000lb


That seems unbelievably light - did the engine and transmission really weigh 1600 pounds? The curb weight of a 2WD 2002 Blazer is about 3600 pounds.


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## brian_ (Feb 7, 2017)

NoSunBeach said:


> YouTube search "Torquetrends 2:1 Direct Drive for EVs" (and skip to 17:41)
> 
> https://youtu.be/WX6Xhl-SP9Q?t=1044


There might be some useful comment in there, but I can't imagne listening for an hour in hope that there might be, and I couldn't be bothered to dig out the headphones to listen to whatever is said that he couldn't be bothered to type. This is the product:
ev-TorqueBox


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## brian_ (Feb 7, 2017)

NoSunBeach said:


> Rear Ratio 8.75





NoSunBeach said:


> I still want to go without a transmission and have some support that my 8.5 to 1 ratio Rear end might not need to shift if the motor is a high RPM motor.


Something is strange there, too - I can't believe that any Blazer has a 8.75:1 final drive ratio - that's insanely extreme. Do you mean that it has a GM rear axle with an 8.75" diameter ring gear (known by terms such as "8.75 rear axle")? Even that would be strange, as this is an obscure axle, which does not appear to have been used near the time of this Blazer. Perhaps the second post has it right, and this is the common 8.5" 10-bolt corporate GM axle; that would explain where "8.5" value came from, but the axle ratio is unknown.


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## brian_ (Feb 7, 2017)

NoSunBeach said:


> I hope to remove the transmission, flip the rear differential to face the back and install a cheap used (<$500) DC motor direct where the gas tank was.
> ...
> Several mechanics feel the flip will be possible and not present issue with rear drum breaks.





NoSunBeach said:


> I've been talking the gear heads on a Chevy forums they feel flipping the rear axle would have some serious challenges


It should be reasonably straightforward to turn the axle around and mount it that way, and the brakes can likely be flipped around to work properly. As you probably already know, the issue is not with the brakes, it is with running the ring and pinion gears in the opposite to the normal rotation. I suspect that you would need a new ring-and-pinion set, or perhaps a set from a front final drive unit, but I haven't done this, and others have.

This configuration, with the shaft coming into the rear axle from the rear, is normal for rear-engine buses and motorhomes... but they are built from the beginning that way, they don't take a used axle and turn it around.

This configuration was also used by Solectria for the E-10, which was an EV version of the S-10 pickup (which was related to the S-10 Blazer). In that case, two motors were mounted behind the axle and between the frame rails, one on each side of the shaft, with their outputs facing rearward and belt drives from the motors to the shaft.


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## jbman (Oct 26, 2017)

brian_ said:


> There might be some useful comment in there, but I can't imagne listening for an hour in hope that there might be, and I couldn't be bothered to dig out the headphones to listen to whatever is said that he couldn't be bothered to type. This is the product:
> ev-TorqueBox


That thing is absurdly expensive. Just use a normal transmission and spend the 3k you saved on more batteries instead.

Additionally, why are you flipping the axle?

I didn't realize that you were ditching the transmission - there's no way you have an 8.75:1 rear end there. Keep the stock transmission if it's a manual. Your requirements are not that crazy.

Sent from my SM-N960U using Tapatalk


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## brian_ (Feb 7, 2017)

jbman said:


> That thing is absurdly expensive. Just use a normal transmission and spend the 3k you saved on more batteries instead.


It is very expensive for what it is, mostly because it is a very low production product. It is much smaller than a whole transmission, and more efficient and much simpler than an automatic transmission, so it has its uses.


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## brian_ (Feb 7, 2017)

jbman said:


> Additionally, why are you flipping the axle?


I thought that part was relatively obvious: put the motor behind the axle, and leave a much more usable space ahead of the axle, without the shaft down the middle. Solectria obviously had the same idea.



jbman said:


> ... there's no way you have an 8.75:1 rear end there.


I agree ; we're just waiting for clarification.


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## cyberpine (Mar 25, 2010)

It's a 2002 2door 2wd curb weight 3500. My mechanic said it would lose 1200 with all the Gas parts out including the transmission. did a partial interior redesign removing the spair tire, passenger seat, entire dash (radio, airbags)… not sure maybe 2300lb - 2500lb clean?

Yes, sorry for confusion, seems rear end ratio can't be 8.75, that appears to be the size of the ring (not sure where I got that). Not sure exactly what it is but likely around 3.4 (my bad).

The video was to support the idea of direct drive on 8.75 rear end ratio... yeah product is way too expensive, but still wondering about direct drive options on a RWD and getting to around 9:1 which is what Tesla uses.


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## jbman (Oct 26, 2017)

brian_ said:


> I thought that part was relatively obvious: put the motor behind the axle, and leave a much more usable space ahead of the axle, without the shaft down the middle. Solectria obviously had the same idea.
> 
> 
> 
> ...


It's a needless complication for this build. His requirements are not very high.

Sent from my SM-N960U using Tapatalk


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## jbman (Oct 26, 2017)

NoSunBeach said:


> It's a 2002 2door 2wd curb weight 3500. My mechanic said it would lose 1200 with all the Gas parts out including the transmission. did a partial interior redesign removing the spair tire, passenger seat, entire dash (radio, airbags)… not sure maybe 2300lb - 2500lb clean?
> 
> 
> 
> ...


You are going to need some kind of gearbox to reach that ratio. Why not just use the transmission you already have, even if you never actually change gears? 

Sent from my SM-N960U using Tapatalk


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## cyberpine (Mar 25, 2010)

jbman said:


> You are going to need some kind of gearbox to reach that ratio. Why not just use the transmission you already have, even if you never actually change gears?
> 
> Sent from my SM-N960U using Tapatalk


Well.. Can I mount a 250 lb motor in front of the transmission and store 20kwh of LiIon and all other components in the front engine bay? (nothing in the back)?

One other question, when they remove the engine, does the transmission have to come out to move/roll the truck?


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## jbman (Oct 26, 2017)

NoSunBeach said:


> Well.. Can I mount a 250 lb motor in front of the transmission and store 20kwh of LiIon and all other components in the front engine bay? (nothing in the back)?
> 
> One other question, when they remove the engine, does the transmission have to come out to move/roll the truck?


I just read that you have an automatic. It can be made to work, but a manual will be easier and more efficient.

Theres more room than just the back cab area and engine bay for batteries. You could split up the pack and have some in the original gas tank location. There's probably more room available than you think.

The transmission doesn't technically have to come out to move the vehicle. It'll probably be wobbly if the engine isn't there, though, being supported by just the crossmember.

Sent from my SM-N960U using Tapatalk


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## cyberpine (Mar 25, 2010)

jbman said:


> I just read that you have an automatic. It can be made to work, but a manual will be easier and more efficient.
> 
> Theres more room than just the back cab area and engine bay for batteries. You could split up the pack and have some in the original gas tank location. There's probably more room available than you think.
> 
> ...


These trucks have decent and deep engine bay. Seems it would be clean and elegant to have all the batteries in the front . Is it a space or weight issue? Is there a safe height for the pack in the engine bay or if we could , would it make sense to rack them on an encloser as low as chassis level?


So no known cheap (cost and space) way to do a 2:1 ratio reduction inline without a full transmission like that Torquetrends 2:1 adapter product is doing? Seems like such great product idea, baring the crazy cost. Not sure why but rotating the rear axle and direct drive sounds so elegant given the great space gained from the gas tank.


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## cyberpine (Mar 25, 2010)

brian_ said:


> I thought that part was relatively obvious: put the motor behind the axle, and leave a much more usable space ahead of the axle, without the shaft down the middle. Solectria obviously had the same idea.


Do you have more information on the Solectria project .. is that the Sunrise Solectria?


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## cyberpine (Mar 25, 2010)

I am wondering if a 2:1 inline gear reducer product like this could handle the rigors of an EV car and 60HP 5000 RPMs?

https://www.ebay.com/itm/21E-N180TC...h=item3b1da97f7f:g:MC4AAOSw0G9brUl3:rk:1:pf:0


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## brian_ (Feb 7, 2017)

NoSunBeach said:


> Do you have more information on the Solectria project .. is that the Sunrise Solectria?


No, the Sunrise was a car project. The E-10 was a straightforward EV built on an S-10 "glider" (vehicle complete except for powertrain). WolfTronix has a web page about his 1996 E-10 restoration, which shows the design.


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## cyberpine (Mar 25, 2010)

NoSunBeach said:


> I am wondering if a 2:1 inline gear reducer product like this could handle the rigors of an EV car and 60HP 5000 RPMs?
> 
> https://www.ebay.com/itm/21E-N180TC...h=item3b1da97f7f:g:MC4AAOSw0G9brUl3:rk:1:pf:0


Additionally, I was talking to somebody on the Chevy forums and he said rather than a mechanical gear reduction that I should look into a *very high wattage variable potentiometer foot throttle control to control motor speed
* … Anybody know how this works or ever try this? Would reducing speed of the motor this way increase torque?


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## brian_ (Feb 7, 2017)

NoSunBeach said:


> Additionally, I was talking to somebody on the Chevy forums and he said rather than a mechanical gear reduction that I should look into a *very high wattage variable potentiometer foot throttle control to control motor speed
> *


This person apparently knows nothing at all about how an electric motor for a vehicle is controlled. While I assume that the suggestion was sincere, I suggest just completely ignoring anything they say about electricity.



NoSunBeach said:


> Anybody know how this works or ever try this?


Yes, it works horribly. No, no one who has any clue what they are doing would try this on a vehicle in the last half century or so.



NoSunBeach said:


> Would reducing speed of the motor this way increase torque?


No.


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## cyberpine (Mar 25, 2010)

brian_ said:


> This person apparently knows nothing at all about how an electric motor for a vehicle is controlled.


LOL.. I now believe he was screwing with me... That thing is bigger than the engine and battery pack. Ha


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## brian_ (Feb 7, 2017)

NoSunBeach said:


> LOL.. I now believe he was screwing with me... That thing is bigger than the engine and battery pack. Ha


This comment didn't make sense until I realized that the big-resistor idea was also discussed in its own thread:
high wattage variable potentiometer foot throttle?

The person making the suggestion may not have realized how wildly unreasonable it was - he may have been serious, and not thinking that the potentiometer would be a huge device such as illustrated in the other thread.


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## cyberpine (Mar 25, 2010)

I've been watching some youtube videos on modest 36v DC Motor + led acid builds and am always surprised to see 50mph/20 mile range builds on shoe string budgets and many seem to not even be changing gears..

It's naïve of me to think this will just work and sorry this thread has jumped around some.. I'm still wondering what to expect if I boldly try this TEST:


* 2500 dry weight with 28 inch wheels
* RWD 3.4:1 rear end ratio
* scrapyard 36v 400amp DC forklift motor direct drive mounted to rear end (no transmission or gearbox)
* Three 12 v deep cycle 200AH Led Acid batteries in series
* ideal controller?

*POSSBILE TO CALCULATE/ESTIMATE?*

WHAT WILL EXPECTED TIME FOR 0-10? LIVABLE? 
WHAT WILL EXPECTED MAX SPEED BE?
WHAT WILL MAX MILE RANGE BE?
WILL ANYTHING GET REALLY HOT AND BLOW UP?
IS THERE AN IDEAL GEAR RATIO FOR THIS CONFIGURATION?


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## Duncan (Dec 8, 2008)

Hi
Forget the lead - and ignore the claims of 20 miles range

The motor/drive/controller layout is what I'm using 

I have a motor that is rated at 48v and 200 amps - but I'm feeding it 1200 amps and 340 volts 

That shifts my 800 kg machine like a scalded cat


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