Hot motor - AGAIN!?!

[Cardnim]

Morning guys,

Quick bit of history:
- racing a Cat SX2
- had 2 previous motors - both Speed Passion v3 6.5 - both bought second hand from fellow oOplers
- both previous motors eventually got so hot that the internals melted enough to ruin the smoothness.
- have tried different combos of spur / pinions and replaced every bearing and ensured no fouling on drivetrain.

So.. now to last night.
- decided not to muck around with 2nd hand motors, so bought a brand new SP v3 6.5; fitted last night for my first club meeting with it.
- after first qualifier the motor was up at 80C!
- fitted a make shift heat sink to it which seemed to bring it down a degree or two.
- but Im really scared (and bloody frustrated) that Im about to cook another (£70!) motor in the first couple of race meets.

I have checked everything that I know of - drivetrain, gearing, binding, bearings - but cannot find anything that is amiss.

The timing on the motor hasnt been touched from factory default (which seems to be in the centre of the timing adjustment ie about 5 degrees)

The ESC is a Speed Passion GT2.0 (lpf) which has its timing turned down to zero and the "DRRS" (start boost thing) down to 3 "normal" from a range of 1 - 9 (9 being max).
Tried it on 1 but still getting the heat.

Top drivers both from my club, and from Schumacher and others have offered me help, but I feel guilty constantly going back to them, (and feela bit embarrased too!) but I dont know enough.

...the SX2 just seems so complicated and Im new to this so really struggling to know what to do.

Any (and all!) advice and suggestions very gratefully recieved guys

[Cardnim]

Should just add my gearing...

Internal gearing = steel idler set = 22 / 33 (IR = 2.70)

Pinion / Spur = 24 / 80

Final Drive Ratio = 9.0

[DCM]

Not knowing the esc and motor, I can only suggest you get advice on gearing and timing settings, as they will dramatically affect heat, plus driving style. Otherwise, your looking at something binding on the car.

[Cardnim]

Really appreciate the help DCM (I wish my car was as fast as your response!! hehehe)

One of the Schumacher guys was helping me with the gearing, and Im running close to the ~8.6 FDR that he recommended so not sure its that (but will try a few different versions!)

Two things Ive thought might be coming into play but not sure:
1 - the track is high grip astro, and Im only opening the throttle fully once, for less than a second coming onto the straight. The rest of the time, Im cruising round somewhere about 50% throttle.

2 - Could the ESC software version be giving me problems. If the firware is set for a modified motor or high end timing, but Im changing the settings to turn it all off/down, then would that cook the motor?

[DCM]

to much timing can cook the motor, but I am a Tekin man, so couldn't really offer you any suggestions on the settings for a speedpassion.

[Big G]

I'd probably gear down on the pinion. It sounds like you're not using much of that top speed anyway

[Gareth J]

it sounds like something may be binding I run a 7.5 sp with sp esc with timings high in my 410 and its hardly even warm

[mattybucks]

I would put the kit spur back on the car 83 i think, and run about a 20-22 tooth pinion.

Firmware on a SP - I use the 205 mod firmware, with the standard settings out of the box settings.

Make sure nothing is binding, and that the belts are not to tight.

[Cardnim]

Cheers DCM, Gaz and Gareth.

@Gareth - thanks for that. Its helpful to hear others running the same motor. I know the SP v3 arent supposed to be a hot runner (like an LRP)

I'll check for binding again, but I build each part of the drivetrain seperately, and then test after each bit is added. It all feels pretty smooth.

[bigred5765]

the best thing to do with gearing is make sure the car is at full revs(so you here the motor scream) at 3/4 the length of the main stright. its hard to give a gear ratio as we dont no how big the track is, gear the car / motor to suit the track,ps 80 deg doesnt seem that hot to me

[Cardnim]

Cheers Matt.
Previous to this motor (i.e. the other two that I cooked) I ran the stock spur and pinion was 22
(i.e. 83 / 22)
but occasionally dropped the pinion to as low as 18.
This still was 80C+ hot!

Thats when I thought that I might have geared TOO low, but last night was high geared and still hot.
Argh.

Belts too tight - to be honest, thats one area of the Cat that I always thought was never explained well.
I have no idea what to set the eccentrics at as it doesnt mention it in the manual.
So, the rear is set so the little dimples line up, whereas the front feels too tight when I do that (and the layshaft clicks) so I slackened it off by one "click" on the eccentric.

(hope that makes sense!)

I was told by another Cat driver that if you can turn your belts over 180 by your hand (i.e. grab the front belt and twist it so the "teeth" are pointing up at you; then its too slack, but with mine you could easily do that.
So I dont think the belts are tight?

*weep* *weep*

[Cardnim]

Cheers Carl - thats good to hear
Re: gearing - Maybe 6.5t is just too much for the small, tight track? I think if I was to gear it as you suggest (for top end @ 3/4 of the str8) then Id be needing spurs that no-one makes! (I think 83T is the biggest spur that I can get for the Cat)

[bigred5765]

we've raced are cat at very small tracks using a 7.5 and a 6.5 we were running 83 x 20 22 on the 7.5, and 83 x 18 x 20 on the 6.5 yeah they get hot, if you wet your finger and put it on the motor if the water boils of straight away its to hot if it disperse slowly your OK,

[bigred5765]

Originally Posted by Cardnim

Cheers Carl - thats good to hear
Re: gearing - Maybe 6.5t is just too much for the small, tight track? I think if I was to gear it as you suggest (for top end @ 3/4 of the str8) then Id be needing spurs that no-one makes! (I think 83T is the biggest spur that I can get for the Cat)

what the size of the track?

[Cardnim]

OK, cheers Carl.
Time to spit on my car... which is just about what I want to do anyways!

@ everyone - thanks for the excellent help guys. Really good to have a sounding board like this

[Timee80]

Are the 2 idler gears the wrong way around? Not had a cat before but just thinking out loud. That would alter IR.

[Cardnim]

This is the actual track:
http://www.youtube.com/watch?v=Ns48O...eature=related

N.B. the track isnt laid out like this anymore, the str8 you see in the video is longer than what we have now, but it gives a fairly good idea.

[Cardnim]

@Timee - hmmm, damn good question mate. Im pretty sure no, as Ive rebuilt that section at least 3 times and always followed the manual - but hey, anything is possible and Im willing to try anything at this stage!
Thanks for the interesting suggestion!

EDIT - dont have the car in work today, but can remember that the 22T gear is on the layshaft with the slipper assembly; and the 33t gear is on the other layshaft (the one with the belt going to the rear diff).
Not sure if anyone on here can confirm if thats right or wrong?

[mattybucks]

I'm sure if you asked one of the schumacher drivers they will be able to advise you in regard to belt tension.

[Cardnim]

@Matty - yeah, you're probably right mate. WIll do.
I just feel a but pants asking as they have already been really helpful with other setup stuff.
I'll do it though, cheers chum. (P.S. hope the TR winter series is going well!)