Yet another electric conversion

[ziggy12345]

Ok I got the power plant ordered so thought I'll start the car build thread. here are the specs of the electrics

MGM X Series 25063 at 360 amps
Lehner 3040/6 6000 watts
KOKAM 4100 65c 2 x 3S Cells

This is all going to be shoe horned into a Kyosho Evolva M3 to make a 6 cell speed car. Target speed is 135mph.

Due to the stresses on the ESC I will have mechanical braking and also for acceleration a mechanical 2 speed gearbox. This will soften the load during the initial phase.

I'll post some pics of the build when it gets underway

Cheers

[_paralyzed_]

people and 2 speeds

[crazyjr]

Originally Posted by ziggy12345

Ok I got the power plant ordered so thought I'll start the car build thread. here are the specs of the electrics

MGM X Series 25063 at 360 amps
Lehner 3040/6 6000 watts
KOKAM 4100 65c 2 x 3S Cells

This is all going to be shoe horned into a Kyosho Evolva M3 to make a 6 cell speed car. Target speed is 135mph.

Due to the stresses on the ESC I will have mechanical braking and also for acceleration a mechanical 2 speed gearbox. This will soften the load during the initial phase.

I'll post some pics of the build when it gets underway

Cheers

If I am reading this right, you are going to run a 3040 off 6s lipo's with an MGM 250amp esc, This is right?

Depending on the KV of the motor (?), you'd never see second gear. The gearing needed, you don't need to worry about the motor or esc, I'd worry about the batteries. Not sure the esc will even run on 6s lipo, I'd check the minimum on the esc specs. I have a 2250/10t (1184kv) motor and its an absolute beast on 6s, Strong enough to snap a Twinforce w/center diff (51 tooth gear) buggy diffs and a 19 tooth pinion with truggy tires Like it isn't even there, I imagine the 3040 will be stronger. Good Luck getting it to fit, I believe, diameter wise, its bigger than a soda can. I will watch your progress.

[ziggy12345]

1st gear gearing will be to 90 mph. I will change the internal gearing in the car so the motor will rev to 30,000 before changing to 2nd. 2nd will be geared to 165mph at 40,000 rpm.

The MGM 250 will run from 4-15 Lipo cells and will handle 360 amp burst so 6 cells no problem

The KOKAM 3S 4100 MAH cells deliver constant 150 amps each for 4 mins. These are tested prior to shipping.

Connections are 3 x 6mm 200 amp gold plated connectors with 6mm square wire each phase.

The reason for the 2 speed mechanical gearbox is that I can fry the motor if I apply too much throttle before the motor spins up. The motor is 92mm long and 60mm diameter so the same as 1/2 a can of Red Bull. The 2250 is 40mm diameter and same length so not much in it.

The Evolva drive shafts have been upgraded to sping steel and hardened and tempered myself. The belts are carbon fibre and metal pulleys all round.

The real problem I have is seeing the car when it starts it run as the run up is 1200ft and the car staying on the ground. Nic case recently ran 173mph and the next run went through the trap at 177mph 5ft off the ground. He is preparing for his 200mph run next month.

I'll post some photos when I get back to the UK and start the build

Cheers

[crazyjr]

I guess you got it covered, I was adressing a few concerns i had. I have no experience in high speed runs, so good luck. looks like you got a mean car in the future

[brainanator]

I've never examined an RC shifting transmission, but is there any slippage? I ask because you're going to get up to 90mph @ 30k rpm, and then it shifts right?...... So then you have that huge mass of a motor spinning at 30k, and now it's way too fast for the speed it's traveling, seems to me like you're going to either break something or spin out the wheels instantly.

[ziggy12345]

The 2 speed clutch is a 2 stage clutch. As the shoes fly out under spring pressure it engages the clutch bell. This rotates the shoes and engages the clutch cam locking the clutch shoes in place with no slip.

When the car changes into 2nd there will be a reduction in revs with the same throttle input resulting in a jump in amp loads. Whether this results in wheel spin or just an increase in acceleration can only be known with testing. The obvious thing to do would be to decrease throttle input but knowing when the car changes might be a problem.

The car will have a gyro so will track straight even if it spins the wheels.

[Revorocks]

Love speed build threads, will be following this one closely.

I'm not too keep on 2 speeds myself, I have a feeling with the amount or torque that motor has the second it reaches 2nd gear it will either spin the wheels or break something.

Would you not be better off going for a single speed, and making a custom motor mount so you can fit a huge pinion? You could have the pinion machined by RW..

Still, the specs look great, that ESC is a monster! I think Nick used one of those in his Slash Insanity project.

[ziggy12345]

the parts have arrive. I might have overspecified the motor...LOL







Looks like I'll need to extend the chasis about 6" to a foot.

Oh well

[ziggy12345]

Thats a 1/8th circuit car by the way, not a 1/12....LOL

[snellemin]

Man, I think just skip the 1/8 and go 1/4 scale with that motor.

[brainanator]

OH GOD! IT'S HUGE! lol....see how small of a car you can wrap around that motor... :)

[RC-Monster Mike]

Originally Posted by ziggy12345

The KOKAM 3S 4100 MAH cells deliver constant 150 amps each for 4 mins. These are tested prior to shipping.

Cheers

Who did the testing? Math doesn't lie. In order for any battery of any capacity to deliver constant current for 4 minutes, the maximum continuous discharge rate would be 15c - and this assumes you would actually get full capacity at 15c discharge, which isn't likely. 15c on a 4100mah battery is 61.5 amps. Maybe they can discharge at 150 amps, but they can't do it for 4 minutes straight unless somebody found perpetual energy and used this amazing discovery in these cells! If the cells deliver full capacity at 150 amps, they could only do so for 1.64 minutes before they were completely discharged.
Cool project, though and I look forward to its completion. :)

[ziggy12345]

A speed run takes about 20 seconds MAX and I would think 2 runs would be good enough so I can discharge the cells in less than a minute. I have 2 x 3 cell 4100 so would have thought I would have enough amps.

The idea is to make a custom chassis a lot longer than the stock one. I just put the car down to show the size of the motor. I have no doubt it will all fit in eventually

Cheers

[Savagery]

That's wicked... the motor does not seem to be too small btw :P

I'll be watching this!