18T Pinion on TT01 chassis?

[Mad Ax]

I upgraded my silvercan to a Trinity Revenge Of The Monster Pro motor for my first race evening.  Our club operates a 27T limit, and the Monster is a high RPM timed, trued and zapped motor.  The only pinion I had with me was the standard 19T pinion, although the Monster instruction sheet suggests I should be running 2-3 teeth smaller than for a standard motor.  The car was off-pace in the straights and I was a bit worried that it was going to get too hot.  However, my TT01-running buddies said that they had ran the Monster with speed tuned gears the week previous, and it overheated.

I know nothing about speed tuned gears, but I do know that some people get hideously confused when dealing with gears, and often make the mistake of fitting a bigger pinion in order to lower gearing, which of course is wrong.

Ergo, I had a root through my Big Box of Bit tonight and found an 18T pinion.  However, I notice that the standard TT01 only allows fitment of a minimum of 19 teeth.  I tried the 18T and it actually seems to fit and mesh OK, and on a full-throttle acceleration and foot-test it doesn't slip at all, and shoots across my living room like a scolded cat.

Am I safe to run my car like this at the next meet, or will I ruin the spur?  Should I be investing in a speed-tuned gear set to lower my gearing?  Will I kill my tasty Monster if I continue to race on 19T? It was OK this week but very hot after each race, and next week I'll be running a heatsink and fan.

I don't really want to have to spend out on a speed-tuned gear set as I'll probably move up to a Corrally RDX in a month or two - I'm only sticking with the TT until I've got the hang of racing accurately, but I don't want to fry the brand new motor as I'll be using that in the Corrally.  OTOH, I don't want to swap back to the silvercan if it's going to put me way off the pace...

Any advice gratefully received, thanks []

[rhenbelz]

I bashed for a while with a Revenge Of The Monster. It killed itself. I raced with an Epic Stock (same motor basically) and it burned up. A friend on another racing team raced with a Revenge and it burned up. You just can't keep those motors cool no matter what gearing, it seems.

Don't worry about the spur if your mesh is good. As long as your motor isn't overheating, stick with what works. On the heatsink note, make sure that you have enough airflow to make the sink worthwhile. It certainly didn't help my Epic!

[rhenbelz]

By the way, the car I used those motors with was my Yokomo MR-4TC.

On the Speed Tuned gears issue, I don't know about the other chasses but I think it would be similar to the TL-01's Speed Tuned Gears option. I tried that back when I gave racing a TL-01 a try, and it turned out that there weren't any 27t motors that put out enough torque to properly run Speed Tuned gears even with the smallest pinion choice. I ended going back to stock gearing with the largest pinion choice, and it worked perfectly.

[sosidge]

The 18T pinion will actually make your car slower than it was with the 19T pinion. Unless your track is super-small you should be OK to run the Monster on a bigger pinion than that.

I usually start a monster on about 7.5:1 - 8.0:1 overall in a touring car. In a TT-01 that would be a 20 or 21 pinion.

The Monster is a high RPM motor which is why it is important to let it rev. Gear too high and it will cook because it doesn't have the torque.

No need to fit the speed tuned gears in that case, all you need is the slightly bigger pinion sets, you can go up to a 22 with the standard spur.

[Mad Ax]

Thanks for the advice, Sosidge. Our track is indoors and is very

technical (it's different every week, but always in the same small

area).  I have 18, 19 and 21 tooth pinions so I'll experiment on

the next meet and see what works best.  I think I'll stick with

the 18 for better acceleration (the other cars were leaving me behind

coming out of the bends - but that might just be my driving!!) and

adjust to 19 or 21 if my car tops out too early.

My new heatsink has a fan attached which I'll hardwire to the

power so it's on all the time - hopefully that should keep it cool

enough, but I guess time will tell... 

[necronomicon]

I know nothing about speed tuned gears, but I do know that some people get hideously confused when dealing with gears, and often make the mistake of fitting a bigger pinion in order to lower gearing, which of course is wrong.

Am I safe to run my car like this at the next meet, or will I ruin the spur?  Should I be investing in a speed-tuned gear set to lower my gearing?  Will I kill my tasty Monster if I continue to race on 19T? It was OK this week but very hot after each race, and next week I'll be running a heatsink and fan.

A bigger pinion gear does lower the gearing on a TT-01, from Tamiyas own guide book the numbers are (for standard spur), 19T pinion= 8.35:1, 20T=7.93:1, 21T=7.55:1, 22T= 7.21:1.  purchasing the speed tuned gear set (2 spur gears, one at 55T, the other 58T), allows a gear ratio of from 8.35:1 right down to 5.72:1. My motors always run hotter with the speed tuned gears in.

Cant say I would recommend an 18T pinion, as i would suspect it will wear the spur gear more quickly as it is not meshing exactly, and of course, you have raised the gear ratio, making the car slower top end as someone above has said.

Hope that helped

[Mad Ax]

A bigger pinion gear does lower the gearing

on a TT-01, from Tamiyas own guide book the numbers are (for standard

spur), 19T pinion= 8.35:1, 20T=7.93:1, 21T=7.55:1, 22T= 7.21:1. 

purchasing the speed tuned gear set (2 spur gears, one at 55T, the

other 58T), allows a gear ratio of from 8.35:1 right down to 5.72:1. My

motors always run hotter with the speed tuned gears in.Cant say I

would recommend an 18T pinion, as i would suspect it will wear the spur

gear more quickly as it is not meshing exactly, and of course, you have

raised the gear ratio, making the car slower top end as someone above

has said.

Hope that helped

If I have made the car slower top-end, then I have increased its acceleration, and of course, I have lowered the gear ratio []

Low ratio = more motor revolutions per wheel revolution

High ratio = less motor revolutions per wheel revolution

i.e. by your post above, the 19T pinion gives a ratio of 8.35:1 which is lower than a ratio of 7.21:1 for the 22T pinion

Ergo,

hitherfore and thereupon, if I have a 19T pinion and my wheels are

turning at 1,000 rpm, then my motor is turning at 8,350 rpm, but if I

fit a 22T pinion then my motor is only turning at 7,210 rpm for the

same wheelspeed.  People have explained to me that high RPM motors

will overheat if they are being forced to run too low; hence, we need

to reduce the ratio by increasing the number of motor turns to wheel

turns in order to keep the motor happy.

don't make me have this argument again []  

[necronomicon]

I see what you are saying, but it is completely the opposite to what the tamiya guide book says on gear ratios, perhaps you would like to ergo, hitherto them as well!- and I wasn't looking for an argument, just trying to help you

Neil

 

[necronomicon]

I think i know what you were trying to say now, and it comes down to this:

high GEAR is a low gear RATIO, like 5th gear on a real car. Poor acceleration, good top speed.

low GEAR is a high gear RATIO. like first gear on a real car, good acceleration, poor top speed.

 

[rhenbelz]

There is probably a miscommunication over ratios and stuff.

In any gear system, no matter what it is, a smaller pinion (first gear) will result in more torque and lower RPMs. Higher is opposite. No need to bother with ratios if they are confusing, just run by that simple rule.

[Mad Ax]

I think i know what you were trying to say now, and it comes down to this:

high GEAR is a low gear RATIO, like 5th gear on a real car. Poor acceleration, good top speed.

low GEAR is a high gear RATIO. like first gear on a real car, good acceleration, poor top speed.

Hmm, maybe you are right...  I will re-consult my gearbox manuals [sticks head in book]

[]

To all above - wasn't looking for an argument / trying to put anyone down, thanks for all your help so far []