Totarx

Hi all, i am aking this post becouse there are a few things that i simply do not understand and wish to learn. I hope there is someone out there that can teach me, and maybe other who have the same question

I was running my TRF 417X the other day at my club. I geared it with a 94/64 spur, and used a 40 pinion on it. It was a Novak, Vulcan motor 13.5.
To just jump to the conclusion of that test, the motor created a small nuclear mushroom under the body of the car. The motor got fried completely.

My question is, som gearing seems to make the car cooler while other seem to make it insanely warm. Is there some sort of rule when it comes to this, spur/pinion ratio. Torque vs speed etc. I really wish to learn this, and i hope someone who understand this a lot better then me could explain this to me. There are several more people at my club who seems to have the same trouble with heat in their motors. I really wish to learn this.

It is a carpet track, not to big. We usually run it around 5ish in FDR ( this depends very much on the car ) and we run the stock class 13.5. ( we are in Norway )

thank you all for taking the time to read this.

nwagner

iTrader: (6)

Are you running blinky or boosted? What motor timing?

5 fdr sounds way too low. You can cook a motor by running at a constant high rev. I'd try a ratio closer to a 4.0 fdr to start.

Totarx

Sorry , we are all running it in blinky mode.

2uzferunner03

You need a high quality motor fan to begin with for running blinky. R1wurks and wtf fan should be available in your area.

I run 17.5 on a small carpet track and optimal gearing is typically 4.0 fdr. 13.5 shouldn't be too far off of that.

Your goal is to come off the track around 160 degrees farenheight.

Trial and error is the best way. Start with 1 minute runs then work your way upto 5 minute runs or whatever your mains are.

bertrandsv87

iTrader: (2)

All I run is Novak ballistic motors, and I had my 13.5t(12.3mm rotor) motor at N timing geared at 4.1666 fdr in my heavy tc4 FT..... Nobody caught me down the straight, and I had good punch in the infield... I have since upgraded to a 12.5mm rotor ,ceramic bearings, and all titanium screws. I gear at 3.65fdr now but I watch temps a lot more...
Novak motors only operate properly around N timing...

InspGadgt

Generally speaking....the smaller your pinion gets or larger your spur gear gets the more acceleration you get but you lose top end. Now this is really generally speaking because there is also internal ratio and tire size to factor in but...if you take the number of teeth in the spur and divide it by the number of teeth in the pinion, the larger that number is the more acceleration you get while sacrificing top end. While the smaller that number is the more top end you get at the expense of acceleration. Most times when you overheat a motor it is because you have geared too much for top end and over worked the motor. That number represents the number of times the motor rotates for each revolution of the spur gear. When the motor spins more than the spur gear it is easier on the motor to move the car. It is a lot like a lever arm lifting a heavy object. The longer the lever arm (greater gear ratio number), the easier it is to lift the object...but you will lift it for a shorter distance. While a shorter arm will lift the object farther but will take much more effort to do so.

starrx

I got a question on gearing
what the difference in
70spur..35pinion=4.0
vs
100spur..50pinion=4.0

will one give me more top or bottom
how do you chose which combo is best
thanks

Totarx

Thank you all so much for the input. So many things to try to understand
Starrx : hehe i was just about to ask a similar question

So to recap the higher the number the more torque witch again leads to less heat ? and less number, leads to more heat, but greater speed ? ( simply put )

So 48p 78/29 = 2.68 - more heat vs 78/25 = 3.12 less heat. ( just as an example. )
Then on top we have the FDR. How much does this come into the discussion when we are talking about generating heat from the motor.

example : the X-ray T4-15 has a 1.9:1
Schumacher MI5 evo 1.8:1

Thanks all for your thoughts. Really learning a lot here

s1a1om

They should give exactly the same performance. At least in terms of first order effects. It's possible that since the 70/35 ratio has smaller gears there will be less inertia in the system leading to slightly quicker acceleration for the same top speed, but this would be a 2rd or 3th order effect and may not be noticeable.

glennhl

iTrader: (16)

I've always found this very interesting and I couldn't agree with you more about 2nd and 3rd order effects. I'd say the smaller gears resulting in less rotating inertia is a 2nd order effect However, the larger gears have a higher contact ratio (more teeth in contact at any one time) making the gear mesh slightly more efficient. And I'd say the higher contact ratio is a 3rd order effect or maybe 4th or 5th order.

patorz31

the biggest effect is the smaller gears allow the motor to be at the rear of its adjustment. moving the motor back has an effect on the way some cars corner. The further back the motor the more some cars rotate.

InspGadgt

For the most part yes...though with brushless motors it is possible to overheat them by under gearing as well but that is pretty rare.

FDR numbers have the same effect. FDR is really the best number to use as that takes into account everything.

old_dude

iTrader: (1)

There is always a sweet spot when gearing any electric motor. Because an electric motor generates peak torque at stall (basically zero rpm) and falls off to near zero torque at max rpm you need to gear accordingly. Lower ratios (small pinion or bigger spur) don't automatically mean quicker acceleration as higher (bigger pinion or smaller spur) don't necessarily mean top speed. You must make the motor work it's torque/efficiency curve. With that said the real answer is not clear. Ask your friends for a starting point on your track and then test at one tooth steps up or down keeping an eye on your motor temp. If the car feels good and temps are in line, try small timing adjustments on the motor to make the final gain. Good luck but I know racers that have raced for many years that still don't understand what just I stated.