Type 1 trans in an electric car

Discuss VW transaxles and transmissions. Gearheads wanted!

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Bruce2
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Type 1 trans in an electric car

Post by Bruce2 » Sat Jan 07, 2017 2:23 pm

Has anyone built a trans for use in an electric car?
I received a request to build a gearbox and am looking for anyone with experience and ideas for the ideal gearbox.

Over the years I have talked to guys with electric Beetles, and they tell me they don't use all the gears. Usually they use 2nd and 4th, or 2nd and 3rd only. First is not necessary since the electric motor makes maximum torque at zero rpm.

Here's a guy driving an electric Bus:
https://www.youtube.com/watch?v=tAuP6A-pM74&t=633s
Start at 12:00 and watch to about 16-17:00

I like the idea of having a rocker switch on the dash to reverse the polarity of the motor. Then build the gearbox with no reverse parts!

If only two gears are ever used, I thought of putting in spacers for the unused gears to reduce the drag of gears through the oil. Then if you do use two gears only, buy aftermarket gears of the ratio needed, then put them in the 3rd and 4th location so shifting is just forward and back on the lever.

Ideas?

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Marc
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Re: Type 1 trans in an electric car

Post by Marc » Sat Jan 07, 2017 3:58 pm

Small world, I've just been researching what it's going to take to come up with a controller for the electric motor that came in a kit car my son recently purchased.
I planned to leave Reverse in place and skip the contactor/relay required to reverse the field. That only works with a DC motor which has a reversible field winding, so if one were to ever change to another type, Reverse would still be needed.
But it you're certain that the trans will alway be used with a reversible motor, I can see the appeal of leaving out the parasitic losses.

A typical DC EV motor is happy to run anywhere between ~1500 and ~4000 RPM, with efficiency & cooling slightly better towards the high end. It might be advantageous to have a taller gear that could be used to maintain speed on downgrades (those not steep enough to coast down).

What voltage will be used, and what's the anticipated cruising/max speeds? Evolks.com offers 4 packages from a 48V setup with a maximum speed of around 40MPH (recommended weight <2000 lbs) on up to 144V that's claimed to be capable of freeway speeds and good for up to 3500 lbs. I'm anticipating using 72V and hoping to have a 25 mile range @ 50 MPH (or 50 mile range @ 25) - they claim a maximum speed of 55 MPH for that combo, which'd be getting to nearly 3000 RPM in 4th with a typical stock VW box and normal tire size....stock 3rd ratio might be better, it'd be below 4000 at top speed and keep the RPMs up at lower speeds, which should reduce motor amps and running temp.

You need an ammeter (especially with a DC motor) and the ideal gear ratio is whatever produces the road speed you're after at the lowest motor current. For my 72V setup, an ideal 2-speed might be a stock 1.26 or 1.32 3rd and a short 4th (1.43, perhaps) but since I'm keeping Reverse I may just as well use stock 2nd & 3rd so it's questionable whether it'd be worth the effort to leave out 1st & 4th.

I had a 3-speed race trans once, just cut the teeth off of a junk fine-tooth 4th to make a spacer and put a stop into the nosecone to prevent going there...I suppose all it would take to block 1st would be to put a spacer under the end of the 1/2 rail.

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Jadewombat
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Re: Type 1 trans in an electric car

Post by Jadewombat » Sat Jan 07, 2017 9:07 pm

When I was in college back in '94 I converted '70 bus to run on electric and used all the gears. The teeth were machined off the flywheel to save weight, no clutch needed to start off in the lower gears, and I simply stepped on the brakes when stopping but didn't press the clutch in. I used all four gears, but probably could've just used 2nd-4th in hindsight. I got it up to 55-60mph around town and never took it on the highway--it was really slow with 14 lead acid batteries (12 for the main pack and 2 6V for the accessories--I had a 400W sound system :D ).

If your motor is strong enough and the battery pack not as heavy as mine was, you "may" be able to get away with starting off in 3rd, etc. since it's impossible to stall an electric motor.

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Marc
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Re: Type 1 trans in an electric car

Post by Marc » Sat Jan 07, 2017 10:25 pm

Jadewombat wrote:...it was really slow with 14 lead acid batteries (12 for the main pack)...
I'm assuming you ran 6V golf-cart batteries for a 72V system, in which case that's encouraging. If you ran 144V and couldn't manage freeway speeds, not so much...

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Re: Type 1 trans in an electric car

Post by Bruce2 » Sun Jan 08, 2017 3:32 am

Marc wrote: I planned to leave Reverse in place and skip the contactor/relay required to reverse the field. That only works with a DC motor which has a reversible field winding,
Good point on the reverse working only with a DC motor. Although if you have a 3 phase AC motor, switching two of the phases will make it go the other way. I don't know if cars run 3 phase AC motors.

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Marc
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Re: Type 1 trans in an electric car

Post by Marc » Sun Jan 08, 2017 1:02 pm

Bruce2 wrote:
Marc wrote: I planned to leave Reverse in place and skip the contactor/relay required to reverse the field. That only works with a DC motor which has a reversible field winding,
Good point on the reverse working only with a DC motor. Although if you have a 3 phase AC motor, switching two of the phases will make it go the other way. I don't know if cars run 3 phase AC motors.
Sloppy sentence structure on my part. I should have written something like "that only works with a DC motor that has a reversible field winding, or a 3-phase AC motor". AC motors are the more modern approach and rapidly gaining in popularity over the old DC golfcart & forklift motors as the price of the inverter needed to operate them is coming down.

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Re: Type 1 trans in an electric car

Post by Bruce2 » Tue Jan 10, 2017 3:23 am

I've got more info on the potential build.
They are using a 96V DC motor that produces 120ft-lbs at zero rpm, dropping to 110ft-lbs at 3500 rpm.
I will have to confirm if they like the idea of a switch for reverse.

They like the idea of a 2 speed. From all of the gears VW produced, they picked 2.06 and .93 on a 3.88 R&P. This gives a final drive ratio of 7.98 and 3.61. I'm going to suggest 1.84 and .89 on a 4.12 R&P to give 7.6 and 3.67:1.
I'm really short on 3.88s, and the .93 only comes in fine tooth. There is no easy way to get 2.06 in a 3rd gear. About the lowest 3rd that will work on a stock main shaft is the 1.84.

They will have the opportunity to make a really custom non-vw looking shifter since it will only go forward and aft. I'll leave that to them.

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Re: Type 1 trans in an electric car

Post by Casting Timmy » Thu Jan 12, 2017 3:32 pm

On using second and third gears only, I wonder if a plate on the top of the shift rods could tie them together so you only had to move the shifter forward or backwards. Be very tempting if this worked to make or think about directional splashers on 1st and 4th to help the bearings.

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Re: Type 1 trans in an electric car

Post by Casting Timmy » Thu Jan 12, 2017 3:33 pm

I do think the 3.88's are drying up, I have one in my garage from a customer as payment towards his bus transaxle I am going to keep for personal use.

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Jadewombat
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Re: Type 1 trans in an electric car

Post by Jadewombat » Thu Jan 12, 2017 9:19 pm

I don't remember the size of the motor, it was 8" I think and yes they were 6V batteries. It "could" probably have gotten up to 65 or so, but would've taken forever. Acceleration was really slow.

Again, this was mid-90s technology, no regenerative braking, and light years before anyone ever considered (that I know of) the Tesla 18650 lithium batteries, etc.

We all knew lead-acid was archaic and outdated even then (I had no power steering in my bus and my arms always hurt after a lot of driving :( ), but if we're all comparing the latest and greatest stuff--unless you're getting a good deal on all of the money you're spending on this EV conversion it'd be better to set your sights on in-wheel motors for the rear...

http://www.roadandtrack.com/motorsports ... ctric-car/

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Marc
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Re: Type 1 trans in an electric car

Post by Marc » Thu Jan 12, 2017 9:35 pm

You can have your VW converted to electric, using more modern technology. Not available as a kit, but for the low low price of $50K or so they'll do all the work. http://www.zelectricmotors.com/

Personally, if I had a car worth sinking that kind of money into I'd want to keep it original and just buy a car that was designed as an EV from the get-go.

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Re: Type 1 trans in an electric car

Post by Bruce2 » Fri Jan 13, 2017 3:41 am

Casting Timmy wrote:On using second and third gears only, I wonder if a plate on the top of the shift rods could tie them together so you only had to move the shifter forward or backwards. Be very tempting if this worked to make or think about directional splashers on 1st and 4th to help the bearings.
That's a pretty good idea to simplify the shift pattern when using only 2nd and 3rd.

I have the go-ahead! It will have the alternate gears I suggested, 1.84 & .89 on a 4.12 R&P.
When I build the pinion shaft, I will leave out 1st and 2nd gears, synchros, and the 1-2 slider. I'll likely get a 1-2 clutch gear cut down so it's just a spacer between 3rd and the 1st gear inner race.
I will remove the reverse idler shaft.
The 1-2, and R shift rod will be out. I have a gear carrier that's been rebushed on the 3-4 bore only.
I will weld a small plate on each side of the 3-4 shift rod to contain the tip of the hockey stick.

Too bad I didn't have a main shaft with 1st gear cleaned off by a drag racer. I may grind off the teeth. And half the teeth on 2nd. 3rd and 4th will be assembled like stock. The main shaft ball bearing will have all the splash lube a stock trans has. At the other end, I suspect the pinion is good enough to put lube onto the main shaft so the needle bearing gets proper lube. I might even grind off the teeth from the coupler.

My customer only buys IRS gearboxes and he's in love with the SSC case. However, I have a 73 DSC case I'm going to offer. This case is perfect except that the PO ruined it by trying to drill out the hole for the starter bushing to use it in a 6V car. I think once it's installed, it will be ok with an open hole where the starter would go, right? I might have to drill a drain hole just in case water finds it's way in.

The car will have a clutch. I think they have sourced an aluminum flywheel. It will have a Stage 1 Kennedy clutch.

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Marc
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Re: Type 1 trans in an electric car

Post by Marc » Fri Jan 13, 2017 5:53 am

Bruce2 wrote:...The car will have a clutch. I think they have sourced an aluminum flywheel. It will have a Stage 1 Kennedy clutch.
The electric motor's bearings can handle that much end-thrust? The motor I have just uses a coupler:
P1090185.JPG
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Pablo2
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Re: Type 1 trans in an electric car

Post by Pablo2 » Fri Jan 13, 2017 12:44 pm

I would be very hesitant to use any aftermarket gear (and especially such a low ratio 3rd) against a torquey electric motor. The factory 2.06 2nd would be FAR more durable.
aka Pablo, gears, Geary
9.36 @ 146 in '86

Bruce2
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Re: Type 1 trans in an electric car

Post by Bruce2 » Fri Jan 13, 2017 1:02 pm

I don't see how you could shift it without a clutch. The armature has a lot of inertia, there's no way the synchros could cope.

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