DIY Electric Car Forums banner
21 - 32 of 32 Posts

·
Registered
Joined
·
7,970 Posts
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 Triumph's swing axle and transverse leaf suspension design is obsolete, but brilliantly compact, occupying only a narrow tunnel across the car, plus some space very low ahead of the axle for trailing rods.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.

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?
 

·
Registered
Joined
·
1,469 Posts
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!
 

·
Registered
Joined
·
7,970 Posts
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).
 

·
Registered
Joined
·
1,664 Posts
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.
 

·
Registered
Joined
·
12 Posts
Discussion Starter · #25 ·
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
 

·
Registered
Joined
·
29 Posts
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
 

Attachments

·
Registered
Joined
·
29 Posts
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.
 

Attachments

·
Registered
Joined
·
12 Posts
Discussion Starter · #29 ·
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.
 

·
Registered
Joined
·
12 Posts
Discussion Starter · #31 ·


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.

Sent from my SM-N960U1 using Tapatalk
 

·
Registered
Joined
·
7,970 Posts
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.

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."
 
21 - 32 of 32 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top