electric beetle - lose gear, keep diff?
 

Hi
I'd like to electrify a beetle. Low weight is key so I wonder
if its possible to remove the gearbox but keep the differential.
This would mean, I suppose, mounting the electric motor where the gearbox
normally is.
Does anyone have blueprints of the gearbox/other transmission parts?
What about the 3d models I have heard talk about on this site -
are they available for download ?
thx , jrr

so low wieght is your goal? funny how batteries weigh more than gas tanks ;)
there is no way to realisticly convert a bug to an electric vehicle and maintain it's weight.

electric beetle
 

The beetle is a reasonable place to start for an electric conversion
since they're cheap, rugged, and chassis is simple.
I am not claiming my result will weigh less than the ~750kg curb weight
of standard beetle. "As light as possible" is the attitude. You are
correct that even NiMh batteries do not compete with gas in terms of energy
density (or cost-yet). But the hybrid gets good results by using both the high energy density of gas
and extra savings from fixed rpm gas operation and regenerative braking.

If anyone has weights for engine, gear, diff, chassis, etc this would help me calculate my final weight beforehand.
Again my primary request of those in the forum is blueprints/diagrams with
dimensions of the beetle transmission,including gearbox and differential.

The goal is to remove as much unnecessary weight as poss, e.g. the engine and gearbox if possible.
I also need to decide how to attach electric motor - to which side (engine
side or in place of the removed gear)

pic of current design
 

attached pic of current design (3d cad file lacking exact dimensions for transmission)

red - generator
teal - elect motor
blue - controller
purple - batteries

If I remember correctly, I think I had seen someone do something similiar with bus.. could be wrong.. but putting it out as FYI..
Alex

Nice idea though..

What max rpm does your motor turn?

You are going to need to retain at least one gear since the input shaft of the trans is not connected to the output shaft. It will probably be 4th gear.

You can probably leave out the shift rod, the hockey stick, internal shift rods, forks, 1st, 2nd and 3rd gears. The trans would need 2 custom spacers to take up the distance left from leaving out those other gears.

For reverse, have a big switch on the dash to reverse the polarity of the motor instead of switching the gear. That way the trans will always be in gear. No clutch required.

Thanks Bruce2 thats exactly the kind of info I need.

My motor has 2500rpm nominal (before torque starts to fall) and 8000rpm max.
100km/hr (~60mph) corresponds to 775wheel revolutions/minute for 68cm diameter wheels.
so I should reduce by factor of ~3 or 4 to get 100km/hr before losing any torque.
If I understand right from http://www.geocities.com/vwtyp181/181_3-2.htm
the diff. has a reduction of 3.8 or 4.3 depending on year so I am ok to just connect motor straight into diff, no other gear required.

Given this and inefficiency of any gear, I'd like to avoid them altogether so I was thinking to remove the gearshift housing and gear carrier (parts 45 and 52 on the attached pic #1), and all the kishkes you mentioned, and attach the motor shaft to whatever sticks out of the differential.
(2nd attached pic)
I can make a doohickey to mount the motor onto the bolt holes that the gear carrier normally attaches to...if I had the blueprints I could plan it now before spending a dime or even a red cent

The reverse is a good idea, already built into the motor controller.

how would you stop? possibly hook up a relay from the brake light switch to kill the power to the motor? So then as soon as you hit the brake the power to the motor is shut off, and is free to be slowed down by the brakes.

New to the idea of how a elec car works. And having one always "in gear" might have some issues, or is this how it's done?

motor controller
 

The braking is taken care of by the motor controller.
When you hit the brake the motor gets rerouted as a generator,
sending power back to the batteries and back-torqueing the
wheels (slowing the car). Its called regenerative braking.
Only if you really slam on the brakes do
the mechanical brakes kick in.

I read recently that 60% of fuel used in the city is wasted on
braking. With 50% regen braking efficiency I stand to gain
30% fuel efficiency off the bat.

Anyone happen to dig up any blueprints?

The gear carrier supports the forward end of the pinion shaft, so I don't think you will be able to remove it.

The R&P reduces the speed of the pinion shaft by either 4.375:1, 4.125:1, or 3.875:1.

is it just me or is there something screwy about this blueprint?
(pic 1)
and does anyone have the full-resolution pic of the proper blueprints (pic 2)