mattdc

Hi all,
I run a 1/10 touring car with 64pitch gearing. My internal ratio is 1.85.

If for example I ran:
a 100t spur and 44t pinion I would have a final drive ratio of 4.205
or
a 116t spur and 51t pinion I would have a final drive ratio of 4.208

(Putting aside the very minute difference in FDR) Obviously running option 2 above I have more teeth in my gearing over all.

Theoretically the strain on the motor would be the same.. ? I don't know

My questions are,

- would there be any difference to the drive of the car? (acceleration, speed, etc)

- and are there any advantages or disadvantages of each situation?

Many thanks for any responses!

WagwanBumba

iTrader: (1)

Not sure how you'd ever fix 116T spur with a 51T pinion but in doing so you'd move the motor more forward. It alters the weight bias in the car. I'm not a good enough driver to feel a difference so I don't worry about it too much but I know that for the Schuey Mi6Evo, they have an even larger than 116T spur to get the motor to shift further forward

mattdc

Thanks for the reply. My examples are theoretical and in the second case a rather extreme example, but they are just example to aid my question.

And you are correct, there is physically no way I could fit a 116t spur with a 51t pinion in my car.

Thanks, I hadn't thought about motor position tuning, there is only the physical possibility to shift my motor forward or back by about 7mm so tuning is that respect (wight bias) is limited in my case.

There are of course lots of spur-pinion combinations that would indeed be possible in my car and result in practically the same FDR.
For example if i wanted an FDR of 4.51 I could go with a 100t spur and 41t pinion, or, 105t spur and 43t pinion.

Any thoughts? Thanks again for any help!

gigaplex

iTrader: (2)

As WagwanBumba said, the only thing it'll change is the position of the motor. There will be no difference in acceleration or speed if the FDR is the same. The motor is pretty heavy, so even a 7mm movement will affect weight distribution.

Racermac73

iTrader: (3)

Run the biggest gears you can fit, while it may not be faster it is more efficient

glennhl

iTrader: (16)

The larger gears overall are slightly different, but most likely negligible. The larger gears have more rotational inertia, which will very slightly reduce acceleration. And the larger gears will have a slightly higher gear contact ratio. The mesh will be just slightly less efficient. Again, it's negligible. But the larger spur gear will stick down further and might get damaged more easily if you hit a rock that happens to stick into the chassis clearance hole for the spur gear.

JoshuaRC10

iTrader: (4)

If FDR remains the same after swapping pinion/spur, I would anticipate the motor position not changing.

I was wrong about this. Additionally, there is no performance difference between one pinion/spur combo and another if the FDR remains the same.

gigaplex

iTrader: (2)

What? No. FDR (final drive ratio) is the ratio, not total number of teeth. Large spur with small pinion gives a very different ratio to small spur with large pinion, even if the total tooth count is the same.

JoshuaRC10

iTrader: (4)

Ahh. You’re right. I was getting confused.

DirkW

iTrader: (1)

Same total number of teeth = same motor position - yes.
Same total number of teeth = same FDR - no.

Same FDR = different motor positions.

roosterreagan

iTrader: (16)

I'm pretty you might have that confused. 50/100 is .5:1____100/50 is 2:1____75/75 is 1:1