# 1979 Triumph Spitfire Conversion



## Wut (Nov 12, 2017)

Just struck a deal for a 1979 Spitfire and will be towing it to the shop this weekend to begin my conversion adventure (will post pictures).

Car is in decent shape. About 100k miles, one tiny spot of pitting on the left rear wheel well. Doesn't run only because the owner was replacing the starter (but not a problem for me!). Transmission seems to be functional.

I want to make this a really fun-to-drive car. Hoping to get a top speed of at least 80 MPH (for freeway driving), 0-60s in under 8s (the quicker the better), and somewhere between 80-100 mile range.

I am looking for feedback/recommendations on battery/motor selection. I'd say my top options at the moment are Tesla Smart batteries (aiming for 20 kWh pack) powering an AC 34 or 35 dual motor. At first glance, it looks like the Tesla batteries will fit nicely where the gas tank is.

Do the dual motors make a noticeable difference in performance or would single AC-50/51 be sufficient for a sporty-feel? 

I've also heard that the Spitfire transmission doesn't handle electric motors well in EV conversions. I'm considering going no transmission (just straight to a diff). Not too picky on this, but was hoping to get some advice.

Anyways, thanks in advance. Really excited to get working on the car!


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## Baratong (Nov 29, 2012)

Hey, nice to see another Spitfire conversion. There's nearly a dozen in the 'Garage'. I converted a 1979 Spitfire Build thread is here Unfortunately these forums 'lost' most of my build pictures..

While I was doing mine, Moltenmetal converted his 1975 Spitfire Build thread here

I've been up to 85mph in mine (in 5th gear). I haven't timed 0 to 60, but I'm sure I'm not under 8seconds. I used a Warp9 DC motor -- which has a lot of torque. 

With your performance goals, you will need a transmission. Going transmission-less would definitely not get your 8s 0-60mph goal, and might not get you to 80mph either. I needed the overdrive gear for that, but the AC motors do have higher RPM ratings than my DC motor -- which is whey I say 'might'.

I would highly recommend not to use the original transmission. It can't handle the torque of the electric motor. I've seen a couple of conversions where the original tranny didn't survive long. I used a T5/World Class transmission in mine. Moltenmetal had a Toyota transmission.

The Tesla cells are certainly a good choice for weight to performance. They weren't readily available when I did my conversion.

I'm looking forward to seeing your conversion progress!


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## Kevin Sharpe (Jul 4, 2011)

Wut said:


> I want to make this a really fun-to-drive car. Hoping to get a top speed of at least 80 MPH (for freeway driving), 0-60s in under 8s (the quicker the better), and somewhere between 80-100 mile range.


I'd take a look at using a Nissan Leaf as a donor car. If you keep your build under 3,300 lbs you can expect 0-60 mph in ~9 seconds, 93 mph top speed, 80 miles range, and rapid charging. Cost for a reasonable 2013 Leaf wreck is ~2,500 USD.

I would dump the transmission to save weight.

If in the future you want more range I'd suggest using 8 Tesla modules (reworked for ~50V), and if you want more performance then the open source inverter should deliver ~300HP 

See here for useful thread on reusing the complete Nissan Leaf system.


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## Baratong (Nov 29, 2012)

Thinking through what I would to if I was starting my Spitfire conversion today, here's what I'd look into:

-- Use Tesla motor mounted in rear. The Spit has independent suspension, so shouldn't be too hard with custom/modified half shafts to use it this way. Won't need a transmission.

-- Put the Tesla packs up front. Without a motor there is plenty of room up front for a decent pack.


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## Wut (Nov 12, 2017)

Thanks for the advice guys.

@Baratong I am interested in the tesla motor idea. Would the "small" Tesla motor work well rear-mounted? Also, do you think I'd have to swap out the forward suspension or just tune it accordingly?

@Kevin Sharpe I'll definitely look into the Nissan parts option. Gotta do more research to see how that can fit into the engine bay.

Do you think the Tesla Smart batteries can put out sufficient power for the performance I am aiming for?

Sent from my SM-G935V using Tapatalk


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## brian_ (Feb 7, 2017)

Baratong said:


> -- Use Tesla motor mounted in rear. The Spit has independent suspension, so shouldn't be too hard with custom/modified half shafts to use it this way. Won't need a transmission.


It would need a transmission, but would be using the one which comes as part of the Tesla drive unit (which is an inverter, motor, single-ratio transmission, final drive gear reduction, and differential as one assembly).

Just replacing the Spitfire differential with a Tesla drive unit (or any other common motor+transaxle unit, such as from a Leaf) seems unlikely to work without problems. The axle shafts in a Spitfire are part of the Spitfire's swing-axle suspension, taking all of the lateral loads. The outputs of any modern transaxle are not designed or intended to take any axial loads at all, let alone the entire lateral force on the rear axle in a turn.

You can completely replace the Spitfire's rear suspension, but at some point I think it's time to ask why any part of the Spitfire chassis is being used at all, since all of it is either unsuitable or being replaced. 



Wut said:


> I am interested in the tesla motor idea. Would the "small" Tesla motor work well rear-mounted?


I can't imagine why anyone would want a Spitfire frame and chassis with more power than one of the "small" Tesla motors (from either rear or front of a Model S).



Wut said:


> Also, do you think I'd have to swap out the forward suspension or just tune it accordingly?


This implies that you think the front will be substantially lighter. With a big pile of battery up front, that might not be true.

Even if the front does end up lighter, I don't see any reason to change anything other than springs and shocks.


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## brian_ (Feb 7, 2017)

Wut said:


> Car is in decent shape. About 100k miles, one tiny spot of pitting on the left rear wheel well. Doesn't run only because the owner was replacing the starter (but not a problem for me!). Transmission seems to be functional.


This may not matter, but this situation sounds like a scam to me. If I had no ethics and wanted to sell a car with a completely dead engine, pulling the starter off and claiming that the engine is fine but just can't be demonstrated would be a great scheme.  I would not budget for any significant recovery of purchase cost by selling the engine.



Wut said:


> I've also heard that the Spitfire transmission doesn't handle electric motors well in EV conversions.


I suspect that the reason is simply that people are fitting motors with higher torque output than the wimpy little engine which they are replacing. If you're doing that, then you likely need a stronger transmission... and you should calculate what the torque input to the final drive (diff) will be (compared to the stock engine output multiplied by the stock first gear ratio), to see if you should be concerned about blowing that up as well.



Wut said:


> I'm considering going no transmission (just straight to a diff). Not too picky on this, but was hoping to get some advice.


If you don't use a transmission of some sort between the motor and the final drive (differential), you only have less than 4:1 speed reduction (and torque multiplication) from motor to axles. The motor will always run relatively slowly, so if you use a typical modern production EV motor the motor will always be in bottom half of its operating speed range, and unable to produce anything close to peak power at most road speeds.

The solution to such tall gearing is a suitable motor. Duncan used an unusually large "forklift" motor in his "Dubious Device" to handle similar gearing; General Motors used an unusually high-torque/low-speed motor (otherwise technically similar to their other AC PM high-voltage motors) in the Spark EV to go with unusually tall (3.17:1 initially, 3.87:1 later) gearing.

To me it seems that a significant advantage of connecting the motor directly to the final drive is that the motor can sit in the original transmission space, leaving the original engine compartment for batteries and reducing the packaging problems that are otherwise encountered. The problem is that a big motor won't fit properly in the transmission tunnel. It is common to see builders cutting out and replacing the entire transmission tunnel; I'm not interested in that level of sheet metal fabrication, or cramping my right leg even more than the stock car. (Note: Duncan's car is custom-built, and accommodates the big motor... even further back than would be possible in a Spitfire frame.)


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## brian_ (Feb 7, 2017)

Wut said:


> I'd say my top options at the moment are Tesla Smart batteries (aiming for 20 kWh pack) ...
> At first glance, it looks like the Tesla batteries will fit nicely where the gas tank is.


That seems like an extraordinarily small space for 20 kWh of battery. Have you compared dimensions of the Tesla Smart pack or its component modules to the available space?

Baratong's conversion of a 1979 Spitfire put 16 of the 45 large prismatic cells (CALB CA100) in the fuel tank space, which is only 5.4 kWh in 32 litres of cell volume plus support structure, etc. I realize that the Smart EV cells have higher energy density, but still...

The images are no longer visible in Baratong's thread (post #198 had photos) but my notes say that the cells in the fuel tank space were arranged as a 4X4 block with the cells vertical (terminals on top), so that would be a 560 mm (side-to-side) by 268 mm (front-to-back) by 216 mm (tall) block. This is a very tidy installation, with little wasted space.

EV West's listing for _Tesla Smart Lithium Ion Battery 18650 EV Module - 57 Volt, 3kWh_ includes these specs for each module:

Capacity: 57Ah, 3kWh
Height: 7.25 Inches
Width: 2.875 Inches
Length: 39.0 Inches
Weight: 42 Pounds
Bolt Size: M6 
Voltage nominal: 3.8V/Cell, 57.0V/Module
Charge voltage cut-off: 4.2V/Cell, 63.0V/Module
Discharging cut-off: 3.3V/Cell, 50V/Module
Maximum Discharging Current (10 sec.):150 Amps
That's 13 litres of volume per module, so at least three modules would fit on a simple volume basis; however, I don't think there's any way to put a metre-long (39") module across the fuel tank space. Even if the length works, only one module could be placed standing up normally in that space, and there's nothing like six or seven times the module width available front-to-back.

EV West says 


> A preferred configuration for a typical AC50 application is 4p2s for a total of 24kWh of energy with a total of 8 modules.


That's 336 pounds (152 kg) of modules, not counting supporting structure, wiring, outer housing, and cooling provisions. It would be a 114 volt, 228 Ah pack, with a maximum discharge rate of 600 amps, and performance limited by cooling.

Even up front, a Smart EV module would extend from the firewall right up to the original radiator location. Several of them side-by-side would fit there, and two layers would fit fine... as long as the motor isn't occupying much of the space. For instance, two layers of four modules wide, all upright, would be
Height: 2 x 7.25 Inches (15.5" or 40 cm)
Width: 4 x 2.875 Inches (11.5" or 30 cm)
Length: 39.0 Inches (99 cm)
... plus support structure, space between modules, outer case, etc.


While I haven't looked at it in detail, it _may_ be possible to place some of the pack in the bottom of the space behind the seats, without preventing the convertible top from folding down. It's probably worth looking at, especially with a front motor configuration, to keep the mass of the components added to the car from making it front-heavy; a Spitfire should be roughly neutral (50:50 load distribution between the axles) with a driver and passenger.


The small size of the Spitfire's tank is a running joke between my wife (the actual owner of our Spitfire) and myself, although published specs say that if you fill it as much as possible it holds 37.6 litres (9.9 US gallons). Between the relatively small tank and the high fuel consumption of our Weber DCOE equipped engine, this car has a shorter range than anything else we've ever owned.


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## Wut (Nov 12, 2017)

Appreciate all the input.

I will be getting to work on the car tomorrow. Planning on removing the engine, fuel tank, etc. and taking measurements to figure out what dimensions I have to work with. 

As far as the motor/transmission, I'm thinking the Nissan Leaf Motor hooked up to a transmission is the way to go. Still looking into replacement transmissions that can handle the high torque (definitely not sticking with the stock transmission). @Baratong How has the T5 held up for you? I am also considering a custom 2-speed as an option. Anyone have advice or experience with this? I definitely want some form of transmission for good performance.

@brian Good call on battery space. I do think there is room behind the seats for some, but I'll probably end up placing some in the engine bay (unless I absolutely need more weight back for distribution).


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## hondarider90 (Jan 14, 2018)

If you're doing a Leaf motor why not go with the whole drive unit? It has gear reduction in it already that should be suitable unless you're wanting to go really fast.


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## Moltenmetal (Mar 20, 2014)

First of all, welcome- and congrats on your great choice of conversion target! Spitfires are a lot of fun!

My AC50 converted Spitfire is a riot- but it doesn't do 0-60 in under 8 seconds. It'll do 100 miles an hour, but not 0-60 in under 8. A big DC motor like Baratong's, or a dual AC35 setup might get you there.

As to re-purposing OEM parts- it's the only way to fly these days. Batteries for sure- Chevy Volt, Nissan Leaf etc. are the only ones worth considering. Forget the LiFePO4 bricks that Baratong and I used- they're too low in energy density and too expensive. OEM batteries are the only way to fly!

As to conversion strategy: the AC50 is far too gutless to use without a transmission- and the existing Triumph transmission is far too wimpy to use with any electric motor. It might survive but won't survive long term.

Mine has chewed up universal joints, but they should have all been replaced when I did the resto anyway. I've been through one differential and the 2nd one is making noise so I have it in to be rebuilt. The existing diff is up to what an AC50 can put out because the same basic diff, half shafts etc. were used in the 6 cyl 120 ft-lbs GT6.

If you can fit a Tesla "small" drive unit in there, that would be ideal- but I caution you that the car is narrow and its existing rear suspension design relies on using the half shafts as one of the control arms found in a modern independent suspension. Loadings on the rear wheels when cornering are transmitted THROUGH the half shafts and their u joints into the bearings in the differential, which perhaps explains somewhat why the car seems to chew up u joints and diffs (not just mine- if you go to the Triumph Experience, next to rear spring buttons and "bachelor's lean" (the tendency of the car to sag to the driver's side over time), you'll find more issues about UJs and the diff than about anything other than the (horrible!) original 1493 cc 4 banger in the car. Differentials usually are a bomb-proof component in cars in my experience, but not so with this one!

Oh, and before someone convinces you otherwise: safe use of Li ion batteries requires the use of a BMS. It's an essential part of your project- don't leave it out. Fortunately others here have built devices which can read various OEM BMSs so you can re-use them, so you don't have to go the home-made or low volume route the rest of us went. Just don't skip the BMS, OK? You might be lucky like some here, who seem to act as their own BMS- but you only have to be unlucky once and your whole project- and maybe your garage and house- will pay the price. Not a gamble I'm willing to take- others are free to make their own choices.

Find the E-Fire in the Garage and click on the link- you will see my suffering in detail- but I don't regret a minute of it- if I knew how well this would turn out, I would have thrown away my car and bought a New Mexico/Arizona/California car in better shape- fighting car cancer is not fun! 15,000 fossl-free miles so far, and my face is still sore from the EV grin! Can't wait until spring to drive it again!

Baratong's build is a lot prettier and better laid out, and he built his own kit DC controller which is the way to go if you decide on DC- it still gives you the most performance per dollar invested, short of a Tesla drivetrain I guess. CurtK's Bumblebee Spitfire is also a nice project to look through. Most of the older ones are "lead sleds"- lead-acid batteries are ancient history now.


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## brian_ (Feb 7, 2017)

hondarider90 said:


> If you're doing a Leaf motor why not go with the whole drive unit?


How would you mount that in a Spitfire? I mean, short of completely replacing the rear suspension and cutting out the insides of the rear body and changing the rear structure?

The Leaf gearbox is a transaxle, which means it includes the differential. It is not suitable for taking the suspension load which the Spitfire's swing-axle suspension needs the final drive unit to take. Suspension conversions have been done on Spitfires which remove the axle loading, but the only ones which are reasonably workable with the frame and body adapt the TR6 design, and still leave structure and spring which would not likely be compatible with the drive unit.

I did see a "bolt on" conversion of a Spitfire to a more modern rear suspension; however, the installation method was to entirely cut off the Spitfire frame well ahead of the axle line, discard the entire rear frame and suspension, and bolt on a new system! Sure, if you want to build a new chassis for the Spitfire body, you can certainly use a Leaf, Tesla, or Smart ED drive unit... and custom suspension or suspension from the drive unit donor. While you're at it, I suggest a Miata front suspension for better handling and reliability. For that matter, just buy a Miata.


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## brian_ (Feb 7, 2017)

*Compact transmission?*



Wut said:


> I am also considering a custom 2-speed as an option. Anyone have advice or experience with this? I definitely want some form of transmission for good performance.


It would be nice to have a very compact two-speed transmission which would mount directly to the motor, and output to a splined shaft (for a slip joint) or flange (for a bolt-on U-joint), and allow the motor to be placed into the transmission tunnel. I haven't seen one.

I haven't seen a reasonably-priced and available two-speed transmission with either two reduction gears or one reduction and one direct. There are still separate overdrive units, but they are getting rare and are neither reasonably priced nor equipped with a useful ratio (you need reduction, not overdrive). The similar separate underdrive units seem to have disappeared; it seems that people just use a transmission with a suitable number of ratios now, instead of tacking on more boxes. 

I spent some time looking at Lenco's drag racing transmissions (which are modular, built up of one reduction stage per module); however, they are expensive and do not back-drive in the reduction ratio (which would mean regenerative braking would always be in direct). 

I also haven't seen any transmission which can readily be mounted to a Leaf motor, other than the Leaf's transmission (which is normal: these motors are configured to drive specific gearboxes, without a clutch, so they are not set up like typical engines with a flywheel flange).


I did find one interesting possibility. It is only a single-speed box, but that's all that most production EVs (such as the Leaf and Teslas) have, and it does provide reduction, which is needed to get the motor into a suitable operating speed range.
*ev-Torque Box*

This thing is massive (it is "specifically for the electric conversion of late model Ford F-Series trucks"), large for what it does, stupidly expensive (US$3495), and is not set up to attach to a Leaf motor... but it is a reduction box to use between a motor and a driveshaft. They also used it in a 1999 Miata conversion, with a "AC Propulsion 13,000RPM 150kW AC Motor". They even used it in a Triumph GT6 conversion! I don't know what the output shaft and mounting face look like of the UQM motor that they use for the F-150, or the motor in the Miata, and I don't even know what motor is in the GT6, so I don't know how close it is to working with any other motor, such as the one from the Leaf.


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## Baratong (Nov 29, 2012)

Moltenmetal said:


> Mine has chewed up universal joints, but they should have all been replaced when I did the resto anyway. I've been through one differential and the 2nd one is making noise so I have it in to be rebuilt. The existing diff is up to what an AC50 can put out because the same basic diff, half shafts etc. were used in the 6 cyl 120 ft-lbs GT6.


My Spitfire's differential is making a progressively increasing racket. I'm going to have to rebuild/replace it sometime soon. I think the instant torque from the DC motor is pushing it beyond what it can bear.


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## brian_ (Feb 7, 2017)

Moltenmetal said:


> If you can fit a Tesla "small" drive unit in there, that would be ideal- but I caution you that the car is narrow and its existing rear suspension design relies on using the half shafts as one of the control arms found in a modern independent suspension. Loadings on the rear wheels when cornering are transmitted THROUGH the half shafts and their u joints into the bearings in the differential, which perhaps explains somewhat why the car seems to chew up u joints and diffs...


Not only that, but below an excellent photo of yours of the Spitfire chassis from behind (from your E-Fire build thread). I took the liberty of downloading and re-uploading this image, so it would display here in a small version.

All of that structure between the frame rails would be in the way of a Tesla drive unit. It could be replaced by something fabricated to arch over the drive unit, but with the spring attached only to the differential, in the conversion this arch would also need to pass directly over the axle line and carry the load of the rear of the vehicle... while fitting in the non-existent space between the drive unit's differential housing (likely bigger than the Triumph housing) and the spring. In the stock configuration, the spring carries the weight of the car through the diff housing, and the diff carries the car by bolts in the middle at the rear (to that box of crossmember) and by a mount that spans across the frame rails at the front.

For those considering a complete Leaf drive unit, I'll note that where those white frame rails start to converge around the front of the final drive unit (diff) is where the Leaf motor would need to sit. 


I would use my own Spitfire (actually my wife's) for illustration, but being lazy compared to all of these fine DIY builders, ours still has the body on it... and a dead engine in it.  Thanks to those who have shared their build experience!


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## Baratong (Nov 29, 2012)

brian_ said:


> Not only that, but below an excellent photo of yours of the Spitfire chassis from behind (from your E-Fire build thread). I took the liberty of downloading and re-uploading this image, so it would display here in a small version.
> 
> All of that structure between the frame rails would be in the way of a Tesla drive unit. It could be replaced by something fabricated to arch over the drive unit, but with the spring attached only to the differential, in the conversion this arch would also need to pass directly over the axle line and carry the load of the rear of the vehicle... while fitting in the non-existent space between the drive unit's differential housing (likely bigger than the Triumph housing) and the spring. In the stock configuration, the spring carries the weight of the car through the diff housing, and the diff carries the car by bolts in the middle at the rear (to that box of crossmember) and by a mount that spans across the frame rails at the front.
> 
> ...


Making that type of a modification would be a fair amount of work... which is not something unheard of in the EV conversion world.

Example of a gent who converted a Spit to use a Miata rear end. Some fabrication for sure, not easy, but not impossible either. Balancing the weakness of the Spit diff when driven by an electric motor, this might overall be a better approach. I'm seriously considering re-working my Spitfire to something like this.... but nobody has ever accused me of doing anything the easy way...


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## brian_ (Feb 7, 2017)

Baratong said:


> Example of a gent who converted a Spit to use a Miata rear end. Some fabrication for sure, not easy, but not impossible either. Balancing the weakness of the Spit diff when driven by an electric motor, this might overall be a better approach. I'm seriously considering re-working my Spitfire to something like this.... but nobody has ever accused me of doing anything the easy way...


Interesting photo - thanks! 
This is NA/NB Miata hardware (not the later NC or current ND), as with almost all custom use of Miata components. Upper structure has been added to the frame to carry the upper arms; lower arm mounts are bracketed right onto the frame. The upper arms look like OEM units, radically modified; the lower arms are obviously custom-fabricated. The odd frame-under-axle configuration of the Spitfire works well for this conversion. The general design is NA/NB Miata but with geometry compromised by available mounting space, while only the hub carriers and outboard are actually stock Mazda parts. I'm sure it works better than the stock Spitfire suspension.

There's no problem with the spring, because this replaces the transverse leaf spring with coil-over shocks. The roll stiffness will be higher (it is deliberately low in the later Spitfires to minimize swing-axle geometry problems).

The Miata diff is a nice fit in there... much easier than either of the EV drive units mentioned (Leaf or Tesla). As is common in mods using Miata bits, the PowerPlant Frame has been abandoned, and a mount to the frame for the front of the diff housing has been added; the Spitfire has a front diff mount anyway, so that's not a problem.

While not as severe as some chassis modifications - and keeping the whole stock frame intact - this still makes me wonder why anyone would do this, rather than just go with the whole Miata? Yes, the Spitfire is even shorter (for those like me who like small cars), but with excessive front weight bias (the result of most conversions), decades-older front suspension, and a relatively flexible structure (even by 1980 standards), the FrankenSpit won't handle as well. 

I think the weird old swing-axle and swing-spring Spitfire is a blast to drive; I also think any Miata is a great sports car. I wouldn't want to make a Spitfire into a half-Miata... but it's good that people can do what they want.


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## Wut (Nov 12, 2017)

Moved the car into the shop today. Stored a bunch of random extra parts (neatly!), took off the top, and removed the gas tank. 

Recorded dimensions of the mid/rear section of the car, but haven't yet calculated the total space available. For the batteries, it looks like I can get a good amount of space behind the seats and possibly even in the most forward part of the trunk (but this will require me to get rid of the spare tire post).

Next step is taking out the engine and its associated components. I may not finish it tomorrow as I want to be cautious as to not damage any parts.

On the topic of motors, is it not possible to remove a Leaf motor's gear reduction and couple it's shaft to a transmission (like a general purpose motor)?


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## brian_ (Feb 7, 2017)

Wut said:


> On the topic of motors, is it not possible to remove a Leaf motor's gear reduction and couple it's shaft to a transmission (like a general purpose motor)?


Yes, but there are challenges...

A relatively minor challenge is that the face of the motor does not match any of the standards for industrial motors, so it won't fit the adapter plates which are available to match up an electric motor with a transmission.

The bigger challenge is that available adapter parts for the shaft assume that the shaft has a plain end - a fitting is clamped to that to provide a flange, to which either

a flywheel is attached, then a normal clutch which accepts the transmission input shaft, or
a coupler is attached which directly accepts the transmission input shaft
The Leaf motor has a splined end, since it is designed to fit into the a female spline in the transaxle input shaft. Custom fabrication of a female-female spline-to-spline adapter with two different splines is thus required, and for common longitudinal transmissions it has the additional challenge that the motor shaft must locate and support the front of the transmission input shaft

In an ideal world, someone would sell a reduction gearbox with

an input side housing designed to bolt to the Leaf motor, 
an output side housing with a place to bolt a support bracket,
an input side shaft with splined socket to match the Leaf motor, and
an output side shaft to accept a traditional propeller shaft (driveshaft).
In the real world if we want this one of us would need to make it.


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## rbzig (Oct 15, 2015)

Hi, Brian, I'm working on a 1970 Spitfire. If I had to do it again I would look real hard at grafting on the whole rear ( or front ) suspension/motor setup from a modern car. Especially after two great builds, Baratong and Moltonmetal, report the sane week link. The REAR END. The real problem is Spitfires are 48" wide. The Tesla 66 wide the Prius is 60 and the Fiat is 55


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## brian_ (Feb 7, 2017)

rbzig said:


> If I had to do it again I would look real hard at grafting on the whole rear ( or front ) suspension/motor setup from a modern car. Especially after two great builds, Baratong and Moltonmetal, report the sane week link. The REAR END.


I understand the logic, but no modern suspension is likely to fit in the rear without cutting out the trunk floor, the floor behind the seats, or both. Triumph's swing axle and transverse leaf suspension design is obsolete, but brilliantly compact, occupying only a narrow tunnel across the car, plus some space very low ahead of the axle for trailing rods.

The custom Miata NA/NB-based suspension shown earlier doesn't look like it fits the floor: the floor's drop into the trunk would likely interfere with the upper control arms, unless they have an unreasonably narrow base.

The front is comparatively easy, as there's nothing but a pair of frame rails to work around.



rbzig said:


> The real problem is Spitfires are 48" wide. The Tesla 66 wide the Prius is 60 and the Fiat is 55


Those are track widths (rather than body widths), and one source shows rear track up to 50" depending on vintage; yes, that's a problem. The first-generation Miata (common chassis for kits and conversions) has about 55" track width as well, which would be one reason that the custom Spitfire rear suspension shown earlier using NA/NB Miata bits has custom control arms.

I'm guess I'm just not enough of a fan of the Spitfire body to want to build a whole new custom car - powertrain, suspension, structure, and floor - and fit half-century-old bodywork to it.

I don't think Spitfires with original engines (or even modified engines) blow up rear ends very frequently. Maybe the solution is just to manage the motor's torque output?


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## Moltenmetal (Mar 20, 2014)

I'm not jumping to the conclusion that the rear ends are no good- not yet, anyway. They are Leyland pieces of garbage, built at the lowest ebb of carmaking in history in my opinion, and the rear suspension design is problematic (trying to put thrusts on shafts containing U joints is just plain stupid in my opinion)- I don't deny any of that. But the same rear end, all except for ratio, was used in the 6cyl GT6 version of the Spitfire and didn't blow up routinely. 

I'm chalking my experience up to bad luck and old parts so far. My first differential was the original one I had in the car- it never had the oil changed in it, ever, and it did sit unused for about 18 years before I did the conversion. I figured it was very likely to come to a bad end- and it did, tearing a tooth out of the crown pinion.

The 2nd was just one I had laying around, which I popped in when the 1st one failed. Again, with no drain plug in the bottom of the casting, there was no way to change the oil in it- the idea was that you just topped it up whenever it got low, which they did a lot because the oil seals usually leaked pretty badly. The diff design with no ability to change the oil in it was probably fine for the low torque of the original engine, but likely not a good strategy for long term survival with electric drive and all the extra torque. 

My second unit was most likely just an original used diff, not one that had been re-built. 

The noise I was experiencing was likely NOT my diff, but rather the diff end of the propshaft, which had a very bad U joint that is next to impossible to detect while the propshaft is still in the car...I was lucky I didn't blow the thing up and lose my propshaft on the way to work one day. The bad joint plus the poor balance of my home-made Toyota-Triumph driveshaft may have killed the differential input shaft bearing, and the gearing in the diff is likely worn and noisy too- but I don't have a report back from the shop yet as to the condition of the thing and what needs doing to it. 

I know a guy who has a 400+hp Nissan drift car engine in a Spitfire, and as far as I know, he didn't change out the diff. He did reinforce its mounts though,as it does have a tendency for the pinion end to tip downward when the torque gets high, given the squishy rubber mounts holding the front of the unit to the frame.

It's a bear of a thing to replace. There's apparently a Subaru diff conversion that you can do, but I think that's limited to the earlier marks. And it's not a pleasant conversion either.

I'll keep you guys updated with my progress. But I"m not panicking, yet. And if I had gone direct drive, I wouldn't be as worried about torque- remember I still have a tranny, and always "launch" in 2nd gear...that, plus the heavy regen settings I have, are likely to blame for whatever longevity problems I'm having with the diff, and fair enough- it's worth it for the fun factor!


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## brian_ (Feb 7, 2017)

Moltenmetal said:


> There's apparently a Subaru diff conversion that you can do, but I think that's limited to the earlier marks.


A Google search for "Spitfire Subaru diff conversion" produces quite a few interesting projects, and even some commercial products.

Themes that I see among these:

most relieve the axle shafts of their suspension function, but some appear to add parts to retain bearings at the diff outputs to allow continued use of the axles as suspension links
conversions using the Subaru diff typically keep the axles as suspension, applying forces to it for which it is presumably not designed; there have been commercially-produced kits for this
suspension changes generally include using coil-over shocks mounted to the stock shock mounts, and upper control arms mounted in place of the transverse leaf
production suspensions (from other vehicles) are not used, because they don't fit
some custom suspensions are mechanically unsound, but most make reasonable sense
The "Subaru" final drive unit (diff) is typically the Hitachi R160 or similar, also used by Datsun for the 510 and Z-cars (yes, it's that old).


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## Karter2 (Nov 17, 2011)

I suspect that any EV transmission component,..gearbox, couplings , diff, UJ's, etc will all suffer a much shorter life than when used in an ICE power train.
Those high torque, low rpm, starts with no clutch are never seen with an ice, and unless care is taken , some massive shock loads can be generated also.


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## Wut (Nov 12, 2017)

Hey all, been awhile since my last update.

Pulled the engine and transmission. Currently working on cleaning up parts and will check out the diff this week. Ordered new LED lights as well. 

Decided to go with the Hyper9 motor. Still in the hunt for a transmission since I won't be using the original.

Gonna check out some OEM batteries this weekend. Although I'd like to use the Tesla Smart batteries, the dimensions won't seem to fit too well in the fuel tank/cargo space (I will double check again). I want to be able to put part of the battery pack there for weight distribution.



Sent from my SM-G935V using Tapatalk


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## Wiggybum (Aug 15, 2017)

You could go direct drive with a lower ratio diff. Triumph used lower ones in Herald cars:

https://www.canleyclassics.com/technical-archive/different-differentials/

Maybe a 4.875 : 1 instead of 3.89 ring and pinion from the UK could save you a pile of work?


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## EVSpitfire (Feb 28, 2014)

The Subaru Diff conversion is a good solution if concerned about high torque from Electric motor. I will (when finished) have UQM PP100 direct drive to 4.44:1 Subby diff. (theoretically 6.7 sec 0-100 klm) 

However as indicated by others, to use the Subaru diff the lower wish bones need to be added hence change of half shafts ++. this can be done by converting to GT6 Rotoflex system. all parts are easily available depending on how far you want to go.. 

To use the swing spring system in the spitfire 1500 and earlier designs, the only option is to use the 510 Diff from datsun. as these have securing bolts for axles to secure to. these are theoretically less changes, i have drawings for adapter plates from original shaft to Diff stub-axle.
Subby R160 diffs only use Snap ring to retain stub axles and can not take any cornering load without the lower-wishbone .

Any one interested in the conversion, i have access to kits to attach the diff without modification to frame.

other drawings i can help with for those brave enough!

PM if any interest / steve


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## EVSpitfire (Feb 28, 2014)

The Subby Diff conversion is a great option for those concerned about high Torque from Electric motor.
My Spitfire 1500 build will have Direct Drive UQM PP100 to Subby 4.44:1 LSD with GT6 (rotoflex) lower wish bones and CV Joints with MGF bearing conversion.
Theoretical 0-100 klm/h 6.7 Sec.
The Swing spring can also be converted, but as indicated the Datsun 510 Diff is required as it has stub axles bolted into Diff as opposed to R160 which is only held in by Snap ring. 
I do have kits available from a manufacture-batch of conversion kits which includes front support plate, Spring plate and Rear plate. Conversion requires no modification to chassis. I can supply advise and drawings for other parts if anyone is interested / brave enough.
steve.


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## Wut (Nov 12, 2017)

Update:

All LED lights arrived and thankfully all fit nicely (the old bulbs were a pain to remove though...). Going to replace the old wiring and some rotted gaskets for the taillights.

I also got my Tesla Model S batteries today. Unfortunately, they got a little dinged up in transit. A couple of them had some damage on the plastic frame at the corners. 

All of the the thin plastic layers that go on top and on the bottom of the modules were torn slightly also. Does anyone know how crucial this outer plastic film is to the entire module? To me, it seems that they serves as a protective boundary to the cells (maybe just for shipping?). They still fit over the modules as intended. The cells, terminals, etc. of each module are in good shape.


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## Marshenz1! (Mar 16, 2019)

The transmission tunnel ion your spitfire is cardboard, takethe radio bracket/cash support out and pull the carpet, I remade one in HS of papier-mâché.It makes adjusting the transmission tunnel very simple


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## Wut (Nov 12, 2017)

Marshenz1! said:


> The transmission tunnel ion your spitfire is cardboard, takethe radio bracket/cash support out and pull the carpet, I remade one in HS of papier-mâché.It makes adjusting the transmission tunnel very simple


Hey thanks for the reply. Been a long time since I posted in this forum. 

Project has been really slow, but I am finally working on the custom mount for the transmission and will be installing a new aluminum tunnel to replace the old one. Hoping to have the whole drivetrain and motor installed within the next few weeks.

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## brian_ (Feb 7, 2017)

Baratong said:


> Example of a gent who converted a Spit to use a Miata rear end...


I recently stumbled across the discussion (in another forum) in which this was originally posted:
_Forums_ » _Grassroots Motorsports_ » _Triumph GT6_

As the builder explains in that discussion, there was a significant amount of fabrication involved, and the geometry still isn't right... and would be substantially more work to fix.



brian_ said:


> I understand the logic, but no modern suspension is likely to fit in the rear without cutting out the trunk floor, the floor behind the seats, or both. Triumph's swing axle and transverse leaf suspension design is obsolete, but brilliantly compact, occupying only a narrow tunnel across the car, plus some space very low ahead of the axle for trailing rods.
> 
> The custom Miata NA/NB-based suspension shown earlier doesn't look like it fits the floor: the floor's drop into the trunk would likely interfere with the upper control arms, unless they have an unreasonably narrow base.


It turns out that the upper arms - which are stock Mazda arms cut apart and re-joined to make them shorter - do fit. Because of all the custom fabrication (not using any of the Miata suspension arms in their original form, and not using the subframe), it does apparently all go under the body: the builder says that "All this fits under a Spitfire body with minimal hammering."


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