Hello BEC Locosters!

I am working on something pretty different, but it shares a lot in common with your mid-engined BEC builds.

Starting with a $5k 2013 Nissan leaf with a pretty sad battery (~40 miles range), I'm keeping all the EV componentry in place while adding a little ICE boost in the form of a 2009 ZX10R engine powering the rear wheels, creating a 300hp AWD DIY hybrid with a 13K redline and sequential box of course. I completely understand that this isn't to everyone's taste and the Nissan Leaf is objectively an ugly non-performance car. But this is being done as a proof of concept build for future projects using a similar hybrid drivetrain and MAY be one of the easiest ways to get a BEC on the road (in California at least). Reverse: solved (via EV powertrain), no need for a big bore 'busa motor or off the line torque/clutch torture (again because EV), emissions (what emissions?), quiet when you're driving through neighbourhoods (nice!).

To make this work mechanically, I'm taking a complete Gen2 Lexus IS rear subframe, and will be mounting the engine on it directly above a Quaife chain drive differential (using a Honda Civic based one). Because of this arrangement the chainline is more complex than your average BEC build.

To help with the design I followed the lead of one of my favorite youtubers and fellow mechanical egineering & BEC enthusiast Superfastmatt and started with 3D scans of all the components. This has been a revelation and has allowed me to spend a bunch of time figuring out things in advance before cutting any metal.

I've designed a cradle from laser cut 3/8" 6061 that supports the front corner of the engine and manages the chainline and supports the differential. This will bolt up to the rear subframe that will have welded structure to support the engine in 3 other spots. I've run FEA based on expected peak chain loads and everything is looking pretty good with >4X factors of safety and minimal deflection.

The output sprocket is a 5/8" offset 15T, the idler is 18T with dual 25mm bore bearings riding on a hollow 25mm shaft, the output sprocket is and aluminum 56T and rides on 40mm bore 80mm bearings which are in machined bearing mounts that are spaced out from the main plates. The final sprocket is a tensioner to take up slack -- 15T on single 17mm ID bearings cantilevered off an idler mount made of a pair of 3/8" 6061 plates.

https://imgur.com/6vbZ6NQ

https://imgur.com/h89xlyg

https://imgur.com/OkZc9XW

Now on with the questions:

1) Any glaring gotchas from this design?

2) The 5/8" offset sprocket has me a little worried about loads on the engine output shaft, although the vendor (PBI sprockets) didn't seem to think I should be worried. I considered designing a support bearing, but as I'm trying to make it easy on my self, the car probably won't see a ton of miles (and have a spare engine available if things go really wrong), I'm currently feeling like taking the risk.

3) Hybrid halfshafts -- is there a way around having scratch built custom axles made? Have people successfully cut-and-welded two different CV halfshafts together (in this case Lexus outer + honda inner) in 1000cc bike engine applications? The internet has mixed feelings on this. I'm almost willing to risk it, but I'd have to have someone do the welding anyway so maybe I should just do it right the first time with custom splined axles.

I will be posting more about this project as things develop, but I'd love to hear experienced peoples thoughts on what I'm up to! Happy to answer other questions about the build as well, as this ICE engine driveline portion is just a small part of it!

If you want to see it all, I have an active google photos album that I just dump everything relevant into as I go along.

https://photos.app.goo.gl/hBUezQtiCVuvTPQ99

That is certainly different.

I like the design before cut approach.

My questions would be how far back does the ev battery pack go and will the subframe need more space than the previous rear arms?

Otherwise... Good luck and welcome to the home of some really knowledgeable people.

quote:

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Originally posted by HowardB
That is certainly different.

I like the design before cut approach.

My questions would be how far back does the ev battery pack go and will the subframe need more space than the previous rear arms?

Otherwise... Good luck and welcome to the home of some really knowledgeable people.

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Welcome to LCB. I love your ideas and it's great to see. Like the old good days when people were mad haters in their sheds. I hope you keep up the enthusiasm to the end!

Most kit cars have some sort of cut down or hybrid half shafts. Mine for example are shortened stock Ford ones.

I broke one of them on a track day. While in the pits I took the car apart to get the shaft out, took it to a local agricultural welder and for £10 he welded it back together on a bench the best he could. It's been fine since.

I would say to give it a go on the cheap. Keep the budget and head ache for somewhere else in your project. If you get everything going and working with just your half shafts to be remade more sturdy, you have done bloody well!

Sleeve and cross pins are the way to go, that way if they do break they dont cause lots of damage.

Interesting project. How are you planning to tie in the bike engine throttle to the Leaf/EV controls?

A couple of negative comments, intended to be constructive - not criticism!

The height of the bike engine is going to give a higher CoG, whether it's enough to affect handling significantly I don't know & from experience with chain drives the relatively complex setup you have with idler etc. may give you grief, only one way to find out really! I doubt the 5/8 on the output will give too much problem as you'll be reducing torque on that from the electric launch - once the battery has gone flat don't be brutal with standing starts!

I made my own driveshafts on my original twin engined Furore build, cut the driveshafts to length, set them up between centres on a lathe with some larger dia tube already slid over the shaft, tacked it up & checked for out of line rotation, once happy with that continued to weld opposite sides until the vee I'd created was weld filled, then slid the tube over & seamed up each end - never damaged a shaft done that way & that was using 2 x ZX10 1000cc engines one on each wheel (I did twist up an early shaft I'd used a kart axle on, the keyway was an obvious weak spot allowing it to twist). The way I did it cost next to nothing & a few hours work, if you're paying someone else to do the setup & welding it may not be much cheaper than custom shafts? Worth investigating?

Good luck with the project, will be interesting to see how it turns out

Great idea, love to see different ideas, like some of the others have said, best of luck.

One other concern might be the current Leaf wiring. I assume it has ECUs everywhere, might it not have a sensor on the rear wheels (wheel speed, ABS, etc) and if you take all that out and replace with a whole new end, that might cause an error or warning in the Leaf electronics, might be hard to solve...

Related - I assume you'll have your own 12v battery to start the bike engine, so hopefully no issue there of 'contamination' between the 2 systems, and like the earlier question - how do you synchronise throttle pedal(s) etc?

I'll watch this one!

Ad

Your going to chain drive a leaf? That's a lot of weight. Plus a bike engine, rad, new subframe etc. Jeez the things going to weight at least 2 tonnes. Can't help thinking you have been better buying a Prius and tuning it.

How are you going to deal with the throttle? The leaf just has a electronic one, I'm assuming the bike engine is cable. This definitely a completely mad project which I can't see any benefit from but whatever floats your boat. Yeah the back of the leaf is very empty (spare wheel well would have been nice) so loads of room to fit another power plant. You could even charge the battery pushing it along with the engine while the motors on regen... See what explodes first lol

Btw I like the styling, it's novel and functional.

You could just buy a second hand later battery and swap it out. You'd end up with a good EV that's worth something.

[Edited on 15/9/21 by Mr Whippy]

quote:

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Originally posted by adampage
Great idea, love to see different ideas, like some of the others have said, best of luck.

One other concern might be the current Leaf wiring. I assume it has ECUs everywhere, might it not have a sensor on the rear wheels (wheel speed, ABS, etc) and if you take all that out and replace with a whole new end, that might cause an error or warning in the Leaf electronics, might be hard to solve...

Related - I assume you'll have your own 12v battery to start the bike engine, so hopefully no issue there of 'contamination' between the 2 systems, and like the earlier question - how do you synchronise throttle pedal(s) etc?

I'll watch this one!

Ad

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Hmm I wouldn't describe the leaf as an automatic. It is in a way like driving one but it brakes using regen, holds on hills with the motor. Keep in mind too that the motor is always engaged, if the front wheels turn so does it. Push it along and it's going to generate electricity and that's got to go somewhere, like into your dodgy battery. This is what happens when you brake or go down hills. It's just a rolling computer and how would it react to being shoved along by a 200bhp engine in the back it doesn't know about, well the results could be interesting, maybe even with lots of flames.

However the main reason i wouldn't take on a project like this is that after all the time, effort and at least 6k, the car would be completely worthless.

But hell if you want to do it, go for it. It will be very educational.


[Edited on 15/9/21 by Mr Whippy]

Good point on the syncing throttles, "like driving down a hill", of course...

Thanks for the feedback russbot -- exactly what I'm after!

Regarding the CoG -- totally get that the engine placement is not ideal, but keep in mind there's an 640lb battery pack inches off the ground in this car, and in the spirit of the build I'm trying to 1) not let perfect be the enemy of good enough, and 2) and use as many of the bike parts as possible, so no low profile sumps or side exit exhausts for now that would allow me to lower the engine more. I'm willing to accept some hits in the driving dynamics area here -- as mentioned this car will weigh close to 4000lbs (blasphemy in these circles I know). It'll be like driving with two large dogs in the boot

Great ideas on the half shafts. That process is similar to others I've read about but feel more confident having heard it done successfully. I'd love to do it without having to disassemble the CV joints, but that may be a bridge too far. I'm a competent machinist but a very novice welder, so I will likely do all the fab work short of final welding. I was thinking of adding an additional non-structural thin outer sleeve to act as a retention loop if the half shaft breaks in half to stop it from flailing around, but maybe I'm over thinking it.

Thank you for the reassurance on the 5/8" offset. I agree that it's the least weird thing about the chainline. I am a little concerned with the chain angle over the single shear single bearing tensioner sprocket causing too much load on it under engine braking, but I don't know what sort of negative torque I'll be dealing with to do any analysis.


As for the questions:

The only electrical interfaces to the leaf will be tapping off of it's 12V system and the throttle.

The bike's battery and alternator connection will be eliminated and the system will be supplied power directly from the leaf's 12V battery through an 80A contactor. The leaf 12V is charged by an onboard DC-DC converter that uses the HV battery. The starter motor will be retained, but eventually I'd like to do stop-start bump starting so it doesn't idle at zero speed. Digging through leaf forums this set up is electrically similar to jump starting another ICE with your Leaf which people have done without issue.

The leaf throttle is a modern electronic dual analog signal hall effect unit, and I will be intercepting these two signals with an Arduino micro controller, which will then process them (along with signals from the bike ECU) and depending on the driving mode (full EV, full power, charge) it will decide what analog values to send along to the leaf ECU, and what to ask the ICE to do. The ICE throttle is run by a 1/4 scale hobby servo. You can see that in action here:

https://photos.app.goo.gl/butgdaMgYsyXqD2X9

I also hope to use this electronic throttle control to pull back on upshifts so that I can do flat footed quickshifting.

The "Charge" mode would have the leaf throttle fully cut out once the car is rolling and have ICE pushing the car along while the front EV performs regenerative braking (as if it was coasting down a hill). Not terribly efficient (going through 2 drivetrains and 2 sets of tires!), but it'll get the job done. OEM vehicles with similar layouts (BMW i8, Acura NSX) have a starter-generator on the ICE doing direct energy production to recharge the hybrid pack, and only do the road-coupled regen in edge cases, but that would be a huge technology lift for me to perform. The leaf has 3 settings, Neutral (0 kw regen), D (15kw) and B (30kw) so there are some options.

Great note about the speed sensors too adampage. I'm going to be looking into the ABS tone rings in the Lexus hubs to see what I have to do to get that to talk to the leaf -- may require another micro controller to spoof the signal to look more leaf-like.


As for the motivation for this project, I totally understand that few people would take something like this on. And I definitely get the appeal of super light sports cars -- in the 1990s my father built a Caterham 7 which he still owns. I've both tracked it and rode as navigator in at Targa Newfoundland (scary!), so I see how a 4000lb hybrid doesn't exactly fit with the spirit of this community. I myself have done a few car projects in the past (built a Datsun 510 rally car and couple of circuit racing Hondas for the 24h or Lemons), but what I was really after was a project to satisfy a few of my desires:

1) a bike engine powered car -- something I've always wanted, the sound, the shifting, something we can all agree on
2) a technology and design focused build. I love solving novel problems and this is full of them. I pretty much do the same thing at work all day building robots, but apparently I can't get enough.
3) creative re-use of old EVs -- California will be full of outdated low-range EVs very soon and creative reuse of them is something that people aren't really thinking about yet -- I am hoping to have it drivable in December to take it to an EV car show in Los Angeles (stretch goal!). I think I might get some emotional responses there
4) a small enough scoped project to actually complete. I'm not building a bespoke car here. In fact, as long as the rear wheels can roll, the car should be able to drive around -- with air conditioning, Bluetooth and the whole bit. I have a 1 car garage that is also my wife's COVID gym so I'm trying to do as much pre-building and then do the install into the car as quickly as possible in another location (likely a friend's shop with a lift). This is another reason the engine is directly on top of the subframe -- trying to build as much as possible into that one unit.
5) something I can park on the street -- again, I have 1 car garage/gym, so this car is going to live on the street. Starting with a very normal car makes this easier
6) something weird enough to be a conversation piece for any sort of car gathering, meet like minded people for professional networking and other future fun.


If this project goes well, I will look to building a similar system into a lighter more performance focused base car with a bespoke battery pack and more custom EV stuff. That said, I've worked in the EV space before and know how much work it is to build a safe and reliable system, hence starting with a stock EV. Mostly I'm just trying to keep focused on my current project.

I've also done non-car projects that are even dumber -- I am a former competitor on Battlebots (American version of Robotwars). I am lucky enough to have a supportive spouse and the funds to complete this. Worst case the whole thing gets parted out (including the battery -- which even at reduced capacity has value in other applications) and the hacked Leaf shell gets scrapped.

The process is really the point here, using cool technology and my skills to build something novel.

And if it is successful in some regards, I don't know about it being worthless -- that all depends on the buyer! I've seen a youtube of an admittedly crude (no firewall!) moto-engine SmartCar where the current owner showing the car didn't build it, so there's a lid for every pot.

[Edited on 15/9/21 by derekbruceyoung]

I'm loving the concept and enthusiasm and the skill and design going into this and the fact that its very different and a brilliant engineering and elctricalling project.

I just worry its going to make all the right BEC noises , but be disappointing,on performance or range or both

Looking forward to seeing the progress

Maybe lower it too as despite the battery weight it's hardly a great handling car, maybe the roof is very heavy. It's a bit of a boat compared to my Fiesta. I don't know why they made the ride height so high.

Range will be limited by tank size -- it'll be short initially as I plan on using the stock bike tank, but fuel refilling is faster (and more accessible) than recharging. Performance wise, some very basic analysis makes it look like it should accelerate like a WRX STI with a ~5s 0-60. Not a 7 for sure, but it shouldn't be slow. Handling will likely be "interesting" with the stock suspension front and IS rear bits. Again, something to address once it's up and running.

Ok here's another couple BEC questions for my new friends here:

What is your shifter lever throw? What is too short? Where's the right balance for stiffness and feel? For the design I'm pursuing for the shift lever, I'm trying to have the mechanism exit through the change dish and make its way forward via a 4-bar linkage to position the shift knob in a pleasing location. My current design has ~35mm of travel from center in either direction, that drives a M6 threaded push-pull cable rearwards towards the engine.

https://photos.app.goo.gl/3J4gh8s4M883krvC8

You can also see the (adjustable) location of the micro swift as an upshift sensor for the quickshifter. I know the $$ commercial ones use a load cell, but I've read of DIY moto builds with switches. Any experience in this regard?

BTW, I just scanned through the users commenting on my thread and noticed how long you've all been here. I thank you for being welcoming to this newb and his weird project.

[Edited on 16/9/21 by derekbruceyoung]

Thats not a design, its a masterpiece of engineering and manufacturing!
Mines a bit of steel pipe welded to a steel pivot tube with a bit of flat bar underneath that the cable clevis slots on to!

TBH 35mm from centre seems a bit long, I recon mine is probably 20-25mm at the top of the knob!
To get the best you need to be able to shift fast for smooth clutchless changes

"Thats not a design, its a masterpiece of engineering and manufacturing!" - or, looked at another way, it's massive overkill for what is a very simple job. Mine is a simple lever on a pivot, with the cable operation taken between the top & the pivot

This is mine
[img]
Description [/img]

What's important is the ratio of the 2 parts above & below the cable, I'd say once my lever knob is in place that's around 2:1 which gives adequate leverage & a short throw, I've never measured it but I'd guess it's aroun 40 - 50mm at the top of the lever

No doubt there is some mechanical wankery going on here -- I will not deny it, but that's where much of the fun of this build lies for me. The reality is that the leaf does not have space where a simple pivot should exist (the stock shift blob and supporting structure are there) and placing the pivot elsewhere but keeping the knob where I want it gives the shifter too much up and down motion.

One of my design philosophies is that CAD time is essentially free and I would rather spend a few hours at the screen on my couch making things able to bolt-in rather than bodging stuff in the car. I'm also trying to retain the finish quality of the interior in the front of the car (which is actually in very nice shape) -- keeping as much stock as possible and making the integration require the fewest modifications. Having the shift mech exit through an existing hole above existing sturdy mounting points (in this case the airbag modules 3x M8). Fabrication is also trivial (aside from extra $$) as it's all laser cut plate again.

Now back the the actual question -- the shift lever on the bike is a Qa after market part that's 38mm long and the short end of the shifter is 37mm -- the long end is 190 giving a 5:1 ratio, with the 71mm total travel creating the 12.5mm travel at the bike. Sounds like I can shorten that up which is good news -- I can make the lower pivot adjustable to tune it for the right feel.

Thanks guys, very helpful!

You go for it man!
i raise you my bent metal

Rescued attachment g2.JPG

Hi guys -- I made my major laser cut part order and parts landing tomorrow -- exciting times! Photos of everything are being stuck in my Google Photos album here -- which I have also annotated if you're unsure as to what you're looking at.

https://photos.app.goo.gl/hBUezQtiCVuvTPQ99

Now, a BEC question -- I'm using a sealed Quaife unit for a Honda which uses special M10X1 left hand threaded bolts which I have. Honda says to torque them to 101Nm, but that's on a hardened steel ring gear and not an aluminium alloy sprocket. A regular coarse thread 12.9 M10 torque specs is more like 65Nm. I started to tighten these up last night and even 65Nm felt like a lot. Anything more than that and I am afraid of yielding the underlying aluminum. I'm leaning towards leaving them at 65Nm. I also used loctite 243 and can paint mark and inspect them regularly (unlike a sealed diff).

I've contacted Quaife to ask them but I'd love to hear your opinions.

[Edited on 29/9/21 by derekbruceyoung]

Race car uses the QDF7ZR, where the alloy (T6) sprocket is held on with M10 std thread 8.8 bolts with nylocs.
I just nip them up, standard length 17mm spanners. The bolts have never come loose.
The sprocket gets changed regularly for different circuits, the nylocs get changed infrequently.
Thing is, where can the sprocket go? If you had a split sprocket I'd be more concerned, but it's solid as pictured. Those K-nuts won't move...

BEC locosters!

I thought I'd give you guys an update -- I've been doing a photo dump of everything related to this project which can be found here: https://photos.app.goo.gl/hBUezQtiCVuvTPQ99


All functionally required systems are in the car -- and I drove it for the first time today under full hybrid power! I did a short 3 mile loop on a divided 4 lane road near my house, where I got into full throttle for the first time. I don't think I made it to redline (but def in the 10K+ rpm range) and I touched 70mph indicated. The power was great the sound was insane. Still lots to do -- getting air to the radiator, filling in the firewall, alignment, etc -- but today was a triumph for me in this project.

https://photos.app.goo.gl/h6wa9XdfgcnNYRgw8


Air intake mocked up in the passenger rear window -- this will feed the radiator

https://photos.app.goo.gl/2qw9Avy1DSCoN5rJ9

The hatch is heavily vented -- bit of a rally-cross feel to it.

https://photos.app.goo.gl/rqfcq3BVHBV3QWi99

Interior has a simple switch panel along with a video feed of the bike gauge from the hatch

https://photos.app.goo.gl/VBdFajceKUtAQBQo9

[Edited on 28/12/21 by derekbruceyoung]

Useless without video, right? I managed to revive my old gopro to get highway onramp footage. You can see I'm ready to short shift -- I need to get used to that 13k redline.

https://photos.app.goo.gl/xLqRKXPUne53TWjTA

Wow that’s looking good. Some tidy engineering in the trunk/frunk boot/froot too!


[Edited on 28/12/21 by ReMan]

quote:

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Originally posted by ReMan
Wow that’s looking good. Some tidy engineering in the trunk/frunk boot/froot too!


[Edited on 28/12/21 by ReMan]

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That is exactly the kind of crazy but well executed idea I love. Definitely seems to work! Does it still have electric drive too?

quote:

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Originally posted by Sanzomat
That is exactly the kind of crazy but well executed idea I love. Definitely seems to work! Does it still have electric drive too?

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After a couple of slow months fixing some problems with the chain line and radiator ducting, the car is reliably on the road!

I've replaced the ball bearings in both the idler and tensioner sprockets with needle bearings which should hopefully help their longevity. I had to increase the size of my window scoop to get enough air into the radiator to be able to run on ICE power only on the highway, so longer distances are now possible.

And while I hesitate to call them finishing touches, I have the interior back together, and the firewall is 95% there. Need to have it fully sealed before I start trying to tackle the interior noise issue, which is crazy loud.

Outside the car, it's not so nuts -- it's the stock muffler after all. I roped a friend into filming a drive-by yesterday, so you can hear for yourself:

https://youtu.be/SxuFXTIhT8I

All the details of this work and more can be found in my photo dump: https://photos.app.goo.gl/hBUezQtiCVuvTPQ99

Love it. That is bat-shit crazy. Could be the only way to convert us petrol heads to volt heads 😆.
Can’t believe how quick that went from idea to execution. Well done.

This is amazing work - well done!

Are there any tax implications with an engine change like this?

Can I ask why you used a camera to film the bike clocks to then display on a monitor rather than relocating the bike clocks onto the dash?

Brilliant job - really is! I'm so impressed the Leaf was that cheap in the first place too, what a steal!

Thanks for the kind words -- I'm a mechanical engineer who works on robots by trade, so this type of work is in my wheel house. I leveraged 3D scanning, CAD, laser cutting and 3D printing (and $$ when needed) to make it happen so quickly and with few errors and issues.

I don't plan on reporting the change to anyone until I'm forced to. EVs don't do smog checks in California for obvious reasons, and that's the only time anyone "official" ever looks at a car here, there's no other additional inspections ever (crazy, but true).

The camera was so I didn't need to extend a 14 conductor cable 15' or so, route it through the firewall and to the dash and then come up with an nicely integrated mounting method. The back up camera was $40 and the mount in the trunk is a touch crude, but no one sees it.

The purchase timing was good, as Leafs with similarly poor condition batteries are going for $8K+ these days.


[Edited on 4/3/22 by derekbruceyoung]

So the car has been going pretty well -- I've kept tweaking and upgrading as I go along and have run a few group rallies (not competitive) with the car and have surprised people with its pace. I also got some attention at Monterey Car Week and an article was written up on myself and the car here: https://www.theautopian.com/how-an-engineer-built-a-nissan-leaf-with-electric-power-up-front-and-a-fire-breathing-motorcycle-engine-in-back />

If you want to see some action photos, they can be seen on my Instagram: https://www.instagram.com/p/CjZmpXNLAKy/?utm_source=ig_web_copy_link

Edit: Made a new thread to talk about same-link same-tooth chain considerations

[Edited on 11/10/22 by derekbruceyoung]

The car has been running great -- and after a chain and sprocket swap for fresh units (an oiler is coming next), and some big brakes (14" rotors!) I am feeling more confident in the car doing canyon runs. Here's a quick one from a couple weekends ago down in Southern California: https://youtube.com/shorts/wwRIiZlr7qw?feature=share

Love it! Amazingly quick work too to go from planning through to completion. Good stuff!

Finally got an oil pressure gauge installed so it was time to hit the track! The bike engine held up great and even with an unbaffled, unmodified oil pan the pressure was rock solid under high lateral G loads. I stuck a camera in the engine area for the last session and can't say the same for my motor mounts - one of the mounting bolts backed off! Only a small amount of damage done to a shear panel. Time to bolt check the whole system.

I clipped together all my camera angles to make a full lap -- check it out:

https://www.youtube.com/watch?v=UgoxhiMSIHA&lc=UgyeHPkCq0bDTJxLlMF4AaABAg&ab_channel=DerekYoung

Sadly had a catastrophic failure of a bearing on the idler sprocket -- the second time this has happened (the first was due to a short cut by me though), so it is time for a redesign to make the chainline more conventional.

The idea is to extend the output shaft via a flex disc (BMW Guibo?) to a short double bearing supported drive shaft to hang a standard (non-offset) sprocket on. This would be done to allow the chain to run forward and clear the alternator cover and water pump and hoses.

I need to move the diff over to the left 100mm or so, which will require new custom axles. Big job and a bunch of $$, but these are experimental car problems, right?