Direct drive or transmission?

[TTmartin]

Hi All,

Im known for asking silly questions so here go's
Just started TT conversion project and find I have a physical problem retaining the gearbox, (gearbox centre to driveshaft clearance for motor) but the car is all wheel drive, with rear wheels driven through a variable haldex unit and diff.
If I can lock up the haldex to give 100% drive Could I then connect motor direct to drive shaft and drive rear wheels? Then remove front wheel drive shafts.

I know the first problem is possibly not having the optimum drive ratio, that's why most conversions retain the gearbox.
Now this is where I need help, to overcome this problem is it possible to control a DC motor similar to star/delta control on AC industrial motors, so you have, effectively two modes low speed and high speed, maybe series and parallel?
Come on people we are talking EV we shouldn't need the gearbox

I originally planned using gearbox to motor set up and removing all the rear drive parts to reduce weight/friction etc but I would achieve the same by not using gearbox and front drive shafts.

My other option is to source the 2 wheel drive gearbox option for this car which has different clearances due to not having the rear drive interface.


Measure twice cut once.

[PHEV]

THe Kostov motors come with a "series or parallel" option for the field coils which has a similar effect.

I've noticed that with this size of motor, my Mazda really doesn't need the gearbox. In fourth gear it will lose traction on a dry road if you put your foot more than 70% down.
The main reason I kept the box was so I didn't have to deal with reverse contactors in such a high power system.
Again, dropping by to try the Mazda would set your mind at rest about the amount of torque to expect.

Steve

[Peter Eggleston]

Since you already have four wheel drive, have you thought of using two motors, one driving each axle. You could then use two fork lift truck motors which individualy are not really powerful enough for a full size car. They are however much more available at a good price in this country than the bigger Netgain or Kostov motors. This could offer all sorts of possibilties such as running one motor on the flat for economy and switching in two for accelerating or hill climbing.
Peter

[TTmartin]

Hi, Steve,

I am up and down the UK with work So would like to drop in and sample the Kostov, when I'm down your way may well contact you.

Peter,
nice idea (2 motors) but not physically possible, (well not by me) also need room for batteries somewhere.

Ok as I have now realized, for a day to day on road car, some sort of gear reduction would be required if only for better range. I am now looking at various types of gearbox on eBay that will do the job, the TT box will sale no problem so alls good.
Until the next problem.

Martin

Measure twice cut once.

[Night Train]

Do you need to keep the four wheel drive?

It is easier to just make an adaptor to fit the motor to the bell housing of the transmission.
Before you order your motor though measure the available radius from the centre of the input shaft. You will need to clear the body of the transmission housing and any suspension movement in the drive shafts that will run past the body of the motor.

Have you removed the engine yet?

When you do you have a measurement to make. Measure the distance from the friction face of the flywheel to the mating face of the engine backplate. It is called the 'magic number'. You will need this when you make the adaptor plate.

You will need to decide whether or not to keep the flywheel and clutch. There are aguments on both sides.
With the clutch and flywheel you will get easier gear changes but at the expense of more weight and high rotating mass that consumes energy to spin up.
Without the clutch and flywheel you will have a simpler coupling to the motor, lower weight and rotating mass but at the cost of possibly much slower gear changes. Not all cars have this problem, some are just easier to change gear then others.

The slow gear changes may not be a problem, many are able to drive using just two gears, second and third, and you can make the change while stopped depending on the nature of the journey.

Keeping the transmission gives you a mechanical reverse. This is so much simpler then an electrical reverse using very costly dual DPDT contactors.

[Peter Eggleston]

I have found that a double electric contactor is a very easy, cheap and effective method of reversing an ev. I used this method on my truck and am using it on my trike.
Peter

[Night Train]

Have you an affordable source for some high current, high voltage DPDT contactors, Peter?
The only ones I have are only 275A @30% duty, 120V and with 48V coils.

I could do with something that would managed 500-600A @70% duty, 144V and with 12v coils.
Failing that I will make a mechanical switch.

[TTmartin]

Hi night train,

Probably did not exlain myself well in the first post.
The engine is out and box seperated, the gearbox centre to drive shaft coupling clearance was my problem, the motor diameter will not fit within, that's why I was considering not using gearbox and connecting motor to the rear drive direct.
The whole problem is because the 4 wheel drive works by connecting the the rear wheels through a prop shaft to a transfer box on the back of the main gearbox, this gearbox is special to the qwatro TT.
After some thought and looking at other possibilities I have realized I need some gear reduction ideally.
my original plan was to use the gearbox And remove all the rear drive system to reduce weight and friction, so just front wheel drive without clutch/flywheel.
I very luckily have now sourced (today actually) a 2 wheel drive gearbox (£40 quid good old ebay) suitable for this car with enough clearance for motor to fit, so first big problem fixed and back on track

[Night Train]

That makes life easier!

You still need the magic number, if you decide to use the clutch, or a close approximation if you have direct drive.

If you are going for direct drive then keep the clutch centre plate for the internal splines if you have it. You should be able to adapt it to a keyed taperlock that fits the motor shaft. Keeping the damping springs in the centre plate will make the coupler a bit more forgiving.

[Peter Eggleston]

As regards contactors, I just use a 72 volt Albright contactor but run it at 120 volts. It works fine. My current does not go above 300 amps. When changing from forward to reverse the contacts are engaged with no current flowing so there is no danger of burning out the contacts by arcing.
Peter