VW Bug conversion thoughts: mating to the transmission/transaxle

harrisonpatm

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I crossed paths with someone near me who, for reasons unknown, likes to collect, store, and resell old VW bugs and other VW vehicles. Don't know why, he just likes to. But when he found out that I have a pipe dream of converting an old VW to electric, he basically offered me to come pick one out (not for free, that'd be too good. But for cheap enough that my pipe dream might not be a pipe dream). Even has a couple with the IC motors already removed.

Therefore I'm actually looking at the specifics of how to go about this. There's decent info out there for converting these. Just thinking for now. But I wanted to gather opinions on one specific item that the internet isn't solid on.

The Bug's motor mates with the transaxle, which has a splined shaft. The clutch plate and flywheel fit over the splined transmission shaft
Google images, transmission input:
3855.jpeg
Clutch/flywheel assembly:
710895.jpeg

My question is this. If I can locate a motor of a suitable power, and mount it in the engine bay. Can I do it with simply a coupler from the new electric motor shaft to the input shaft of the transaxle? Or do I need to preserve the flywheel/clutch from the original motor?

If you google VW bug electric conversions, 75% of the results use the Hyper9 motor with a shaft-to-shaft. So in theory I don't really need the flywheel setup, which is just there to smooth the IC engine's output.

I realize that there's a ton of variables. Just wondering what obvious things I'm missing regarding clutch vs no clutch. Thanks for looking!

(Here's a link to the expensive EVWest bolt-on kit, where it seems like it's just a shaft-to-shaft connection)
 
Edit: it seems like there's 50-50 on the different approaches out there, to either retain the flywheel/clutch, or mate directly to the transmission input. Theoretically you can still retain the gearbox and shift gears even without a clutch and flywheel, but some people like to retain the ability to mechanically separate the motor output from the transmission, using an original clutch. That's valid. Wondering what other people think.
 
I used to work on bug motors way back in the day. My friends dad was a body and fender man for a local VW dealership and they had VW's coming in and out of their garage all the time. I would go over to my friends house and work on his baja-bug and other bugs pretty much every week. They were easy to get in and out. One floor jack, a few bolts (8 maybe?) some wiring removed and out they came. Between me and my friend we would lift the motors up off the jack and park them on the work bench. 💪💪

I used to drive them mostly with the clutch, but from time to time just to prove it could be done I would shift without the clutch. It would grind the gears a little bit but it worked.

IMO, I would go with the clutch setup if you can. It will be more effort to get it right. A fair bit of machining and expert welding involved to get everything precisely lined-up, but it will save wear on my transaxle. (unless you can find someone who sells coupling kits that you can buy.)

If you go without a clutch you will find yourself leaving it in a chosen gear most of the time which may or may not be what you want for higher speeds. Unless, your motor can handle the torque needed to get your bug going up a freeway on-ramp or other hill while in third or fourth gear.
 
If your motor is torquey enough, you might cook the clutch if you get hooked on the EV grin.
 
If you go without a clutch you will find yourself leaving it in a chosen gear most of the time which may or may not be what you want for higher speeds.
Theoretically, because it's an electric motor that can't stall, shouldn't I still be able to shift gears even if the motor output is coupled to the transaxle input? Surely I would need to be careful about it, because as you said, a powerful enough motor might strip the trans if I'm throttling while shifting. So I would need to at the very least stop accelerating during a shift.

If your motor is torquey enough, you might cook the clutch if you get hooked on the EV grin.
Not sure exactly what you mean, but are you saying, if I retain the clutch with an strong enough electric motor, I could damage the clutch?

See, this is why I wanted to take a poll. Mechanically I can see how it can work either way, but I'm not sure what the right way is, because the opinions seem to be split down the middle.
 
Not sure exactly what you mean, but are you saying, if I retain the clutch with an strong enough electric motor, I could damage the clutch?

A stock clutch has only so much holding torque, depending on the condition of the spring plate and the friction plate. If your e-bike motor exceeds that holding torque, then every time you mash the accelerator from a dead stop, you will slip the clutch under full pressure. Enough of that action could glaze, burn, or wear away the friction plate until it slips more (or all) of the time.

You could mitigate or avoid this problem with controller programming, by limiting current until RPMs rise and torque decreases.
 
They do sell performance clutches for bugs that can handle higher torque. My guess is that if you accelerate normally through the gears, you won't over-torque it. If you abuse it, you can damage it like anything else. I miss having a manual transmission, but my wife can't drive a stick.
 
I miss having a manual transmission, but my wife can't drive a stick.
Same. I was thinking that I couple shafts, it would retain the option to shift gears if I need/want to. But also, with the right motor with the right torque curve, my wife who also can't drive a stick has the option to just stay in first. Or second, whatever it ends up being.
 
Theoretically, because it's an electric motor that can't stall, shouldn't I still be able to shift gears even if the motor output is coupled to the transaxle input? Surely I would need to be careful about it, because as you said, a powerful enough motor might strip the trans if I'm throttling while shifting. So I would need to at the very least stop accelerating during a shift.
I used to keep the RPM steady while pulling the shift stick out of a gear, remove my foot from the pedal and then gently find the next gear being ready to accelerate so you don't lose momentum from a taller gear engagement. It took a little practice but it is possible. Done too much though you could round the corners off your gears teeth and end up with a sloppy gear box.

As for the clutch, Chalo is correct. It you have too much torque for the condition and /or spring tension of the clutch an excessively torquey motor could spin the clutch plate and fry your clutch. "Heavy Duty" clutches used to be available, I don't know about now.

My friend used to have what are called "cutting breaks" on his baja bug. They are a lever system that will lock up one of the rear wheels at a time when pushed. It would allow his bug to pivot on one rear wheel. If you locked up one wheel and hit the gas pedal you could do a u-turn on a very narrow street. However to do that you would need a heavy duty clutch to keep the inertia of the bug moving while one of the rear wheels was fully stopped.
 
Alright, hear me out @e-beach (or anyone else with more knowledge than me of the older VW transaxles)...

If you have the motor removed, and you're in gear, and you spin the rear wheel, the transaxle input shaft also turns, right? Meaning that when in gear, the drive force is coupled with the transaxle. When shifting, you have to pass through neutral, but when you do so while driving, the transaxle input shaft is still rotating from its momentum. Then shifting into a different gear engages gear teeth that are moving at a different speed. The reason why we disengage the clutch while shifting in an ICE, is because the rotational torque of the gas engine and its inertially large flywheel would otherwise strip the gear teeth, fry the clutch plate, or both. You disengage the clutch, shift, and gradually give it more throttle to slowly re-engage the motor's clutch plate with the transaxle, which are moving at two different speeds because you switched gears. As far as I can tell from online pictures and diagrams, this is done via brass forks and rings that gradually bring together the teeth of two gears moving at different speeds. As mentioned above, you can technically do this without using the clutch, but you have to do so carefully and it's hard on the gearbox, because you're engaging higher gear teeth while keeping the motor's flywheel's momentum constant, while the motor's flywheel/output and transmission are still coupled.

Now, if I were to directly mate an electric motor shaft to the transaxle input, without a clutch, switching gears would still happen the same way, and there's no rotational momentum of a gas motor's flywheel that would engage the teeth of the next gear at too fast or too slow of a speed. As long as the motor is not under load, switching gears should almost happen the same way as it did in the original build, even without a clutch. Because removing the motor's load (cutting throttle) effectively disengages drive power from the transmission, almost the same way as disengaging the clutch.

It won't be exactly the same. Because when coupled directly to the shaft of an electric motor, the transaxle input shaft now had the additional rotational momentum of a free-spinning stator, and however heavy that would be. This will be much less than that of the gas motor's flywheel, and if the motor's bearings are good it'll speed up or slow down more easily. So the gear teeth should still be able to mesh without much issue. But 5000rpm is still 5000rpm, and that would need to be taken under consideration with motor choice. I would also need to be very careful about the strength of the shaft coupler I use, because when changing gears, the transaxle shaft and the motor shaft will momentarily have two different velocities, and the coupler is going to take the brunt of their stress. Like two divorced parents fighting and taking it out on their kids suffering in silence until they crack... woah that got dark.

Anyway. This is how it would work as I understand it. As @e-beach pointed out, mounting a motor and coupling two shafts is a mechanically easier job than precisely mating and lining up everything to retain the clutch and pressure plate, so I'd consider the project more possibly if I could just drive the transmission input directly. And I could even keep the clutch pedal and have it trigger a switch to cut throttle power, to keep the manual transmission driving experience the same and prevent the motor from throttling while shifting gears. Like an electronic clutch. And as pointed out earlier, depending on motor choice, it's possible that it'd be a moot point anyway, if I find a motor with the right torque curve and keep it in 2nd, 3rd or 4th at all times, depending on my speed requirements.
 
The answer is probably here :


From experience, on a bicycle, when using an internal gear hub combined with a mid-drive motor a momentary motor cutout is necessary in order to shift gears.

like this :

 
As far as I can tell from online pictures and diagrams, this is done via brass forks and rings that gradually bring together the teeth of two gears moving at different speeds.
Those are synchronizers or "synchro". They are in effect like little wet clutches that spin mating parts up to the same RPM so they can mesh smoothly.
 
The answer is probably here :

Sure, and I'm looking there as well, but I haven't dived too deep in there yet, whereas I'm more familiar with this forum and community. I'll probably end up there soon enough.

The first impression opinion I have of that forum is that most of the advice tends to be "just buy the kit"
 
Those are synchronizers or "synchro". They are in effect like little wet clutches that spin mating parts up to the same RPM so they can mesh smoothly.
Thanks for the info. Does this mesh with what I was understanding, that smooth transition from gear to gear is done in the transmission, under little to no load while the clutch is disengaged? Some VW forums are suggestions that transmission wear and tear is due to shifting between gears too quickly, regardless of clutch.
 
Does this mesh with what I was understanding, that smooth transition from gear to gear is done in the transmission, under little to no load while the clutch is disengaged?
Yes, the pressure that causes synchronizers to engage comes from the shift lever. It's by definition something that happens when the clutch is disengaged.
 
the pressure that causes synchronizers to engage comes from the shift lever.
I'll take that under consideration if I ever get the gearbox in my yard, to make sure that I don't disengage the levers from the clutch pedal. Thank you
 
I'll take that under consideration if I ever get the gearbox in my yard, to make sure that I don't disengage the levers from the clutch pedal. Thank you
By "shift lever" I mean the stick that pokes up into the car and has a knob on it.
 
By "shift lever" I mean the stick that pokes up into the car and has a knob on it.
Oh that thing? I thought that's just what the car enthusiast guys like to use during their special one-on-one times with their precious baby vehicles...
 
Back in the day I had a 69 bug with stick shift auto. Basically the manual trans with 1st gear removed & a torque converter between the clutch & gearbox. 2nd, 3rd & 4th became L, 1 & 2. The owners manual stated use 1 around town & 2 on the highway. L just for heavy going. Single gear driving. Worked pretty well. I reckon you'll only need 3rd & 4th.

AussieRider
 
It was a long time since I worked on a beetle, but I think there is decent amount of room under the floor over the transmission?
Wouldnt it be possible to mount a whole electric transaxle instead of the old transmission?
Then you dont have to worry about if it can take the torque etc.
 
It was a long time since I worked on a beetle, but I think there is decent amount of room under the floor over the transmission?
Wouldnt it be possible to mount a whole electric transaxle instead of the old transmission?
Then you dont have to worry about if it can take the torque etc.
Are you referring to a product like this:

Though in the power range that would drive a car (15-35kw is what I'm aiming for)?

It would be true, I'm sure, but that would require the purchase of a rather specific piece for rather expensive. Whereas if I can find a suitable powered motor for cheap, and mate it with the existing transaxle, that would be quite a bit cheaper and require much less custom work. In addition, the VW bug is such a common car that one can find every part needed for it in case of failure, including an entire new transaxle. I'd rather keep a bunch of the original parts, for that reason.

I don't have the car to work on now, this isn't something I need to get done in a hurry. Just a pipe dream that I'm getting closer to, so now I'm thinking about specific elements on the build and what would be needed
 
Before the advent of the modern electric cars a DIY VW conversion was fairly common way to go electric.
Guys like Peter Oliver used to take a VW chassis and bolt on fiberglass body kits. His company is mostly training these days.
Make Mine Electric™ | Convert your Car to EV | EV Technician Training & Referral
Really, the only custom part is the adapter plate and if your a machinist and can make your own parts, poke about the internet you'll find the drawings to adapt a variety of motors.
Some projects are done for just the fun or challenge of it.
Bearing in mind a secondhand Nissan Leaf could be purchased for about the same money as all the parts needed to build up a DIY VW.
Our 2011 Leaf is down to 40 range but it is still the most often use vehicle in our household.

Portland craigslist
 
Really, the only custom part is the adapter plate and if your a machinist and can make your own parts, poke about the internet you'll find the drawings to adapt a variety of motors.
Some projects are done for just the fun or challenge of it.
Bearing in mind a secondhand Nissan Leaf could be purchased for about the same money as all the parts needed to build up a DIY VW.
This sums it up right here. A purchased secondhand Leaf would have more range, more reliability, better charging, higher top speed... The biggest reasons for wanting to convert an old car are 1, funsies, and 2, aesthetic.

I think perhaps one of the only mechanical/ functional advantages of a beetle conversion over a leaf is the size. It's possible that it takes less energy overall to drive a bug conversion compared to a Leaf, even with a leaf being a small car. Also, my currently motorcycle conversion is going to use 28s Li-ion. 102VDC nominal is on the low side for a car, but if it works, it'd be cool to have the same battery voltage for both my motorcycle and my car. It'd then use the same DC-DC solar charging setup I have, which would be neat.
 
I think perhaps one of the only mechanical/ functional advantages of a beetle conversion over a leaf is the size. It's possible that it takes less energy overall to drive a bug conversion compared to a Leaf, even with a leaf being a small car.
Are you ignoring the importance of aerodynamics on purpose?
 
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