Yet another electric conversion

[RC-Monster Mike]

Kokam makes great cells and I don't doubt they can get the job done - just stating the absolutes regarding disharge rate, capacity, etc. - the car is small and light enough to get real speed with these batts for sure and I look forward to the result when it is all done. :)

[BrianG]

FWIW, I tried a 2 speed setup in an Ofna Ultra GTP and didn't like it. The tires would break loose when it shifted and control was difficult to say the least. Electric motors simply produce too much torque. You can try to minimize the difference in rpms when it shifts by narrowing the ratio between 1st and 2nd gears (motor rpms don't drop as much), but I still had a really hard time keeping the tires from spinning.

Personally, simply using a large motor and gearing up high enough to get your desired speed would be the way to go. However, when geared very high, startups can be rough with sensorless systems (not enough motor revs per inch of vehicle movement for the ESC to get a good feedback for commutation). It would be nice if there were large sensored motors available, and when coupled with a sensored ESC (like a Tekin RX8), startups are much smoother and controllable, yet can still spin at high rpms.

[PBO]

Originally Posted by ziggy12345

I'm sure there's a 1/8 platform under there somewhere!

[ziggy12345]

Yeah but I'll ditch the chassis and keep the back and front. I'm making the mtor mounts now. I should have something workable in a few days

Cheers

[Serum]

That's quite a bit of motor, this seems like a fun project, Keeping it on the ground might be an issue. Perhaps you could shift the motor to the front to make it more stable in the front end, in order to avoid the wind to get underneath it.

There might be better batteries out there, current/voltage wise, don't make a chassis that only fit these batteries, that's my advice.

[ziggy12345]

The chassis will be able to take 12 cells. The ESC is good for 63v so at 250 amps thats 21hp!! LOL

[ziggy12345]

I changed the chassis and installed a right andgle drive

See!







Still loads to do. The chasis needs strengthening so I'll add some angle ally along each edge. Make a motor - Gearbox coupling. Install the servos. etc.. etc...

Bloody 'ell, how long is the center belt going to be? Are you going to use multiple belts to get the power to the front? Looks insane though. Good insane, not bad insane.

[feistyacorn]

Holy crap! This looks AWESOME! Is that a custom gearbox?

[ziggy12345]

I positioned the front so the middel belt pulleys are 597mm apart. With 18/26 gears I can then use the HPC gears HTD3 3mm Pitch belt 1263mm long.

The gearbox is also from HPC gears Its the HPC-GBK-101. It came packed with grease so I washed it out and oiled it with light oil. Its only supposed to be rated to 3600 rpm and I'll be reving it to 60,000 rpm. LOL. Lets see what happens

Cheers

[devious1]

Um Wow,
Not to into speed runs but i like watching them,
Ill definitely be watching this thread...

[coolhandcountry]

Things I found to help with a multi speed electric motor driven rc.
Make the shift points lower.
It changes gear it changes a precentage.
slower speed means less rpm difference.
you only need to get the car rolling not up to 90 mph.
Motor should have plent power after going to pull 2nd with no issues.

[ziggy12345]

I connected the ESC, Motor and cells and had the car running on the bench. Just a couple of small things to do and it will be ready for a run.

Still wating for the long side belt to make it 4WD

Cheers

[ziggy12345]

Testing the MGM 25063 throttle ramp. As you can see in the video I apply full throttle and the ESC ramps from 0-100 over 30 seconds. I dont let the car get to full speed


http://www.youtube.com/watch?v=IB-1D...ature=youtu.be

Cheers