gear ratio vs gear size

[johnnyh66]

I know the speed is the same as long as the ratio is the same, but is there a difference to a motor (how hard it has to work), when using different toothed gears that have the same ratio?

e.g.
11t pinion/55t spur = 5:1
12t pinion/60t spur = 5:1
13t pinion/65t spur = 5:1
14t pinion/70t spur = 5:1

[reden]

How hard the motor work is determined by the ratio.
On all the motor would require the same power.
The 14T pinion setup would be the strongest.

But then!!!

Larger pinion (14T vs 11T) would give more friction.
The 11T setup would give light weight but less durability.
14T more weight but better durability.

ie: F1 car verses Indy car.

[Docwolf]

i doubt the friction would be enough to out weigh the durability. now a lighter spur would help, less mass to turn, less power to turn it. again, is it measurable, I doubt it.

[johnnyh66]

It seems to me... my pondering that is, that the 11t/55t would have more low end punch because the motor is turning smaller gears.

And the 14t/70t would have a more difficult time on the low end but work easier on the top end.

[badhoopty]

only reason i would use bigger gears is for durability. a 14t pinion is alot more friendly to a spur gear than say a 8 or 9t.

i wouldnt worry about the weight of the spur gear as much as the weight in the wheels. if you took that 8oz or whatever out of your wheels you should be able to notice a difference, i doubt that you would tell any difference at all with a slightly heavier spur and pinion.

[Docwolf]

well, when you say it like that..........then yes. I see what you getting at now. yes, the motor will not work as hard to spin a small pinion/larger spur.

[reden]

Originally Posted by johnnyh66

It seems to me... my pondering that is, that the 11t/55t would have more low end punch because the motor is turning smaller gears.

And the 14t/70t would have a more difficult time on the low end but work easier on the top end.

Low End, less inertia, weaker.
Top End, more inertia, stronger.

Engineering maths.

Bigger is stronger but difficult to turn. (accelerate)
Smaller is lighter but breaks easy.

[johnnyh66]

Originally Posted by badhoopty

only reason i would use bigger gears is for durability. a 14t pinion is alot more friendly to a spur gear than say a 8 or 9t.

I thought about that when looking at the 9t... it looks mean.

Originally Posted by badhoopty

i wouldnt worry about the weight of the spur gear as much as the weight in the wheels. if you took that 8oz or whatever out of your wheels you...

blasphemy!

Originally Posted by Docwolf

well, when you say it like that..........then yes. I see what you getting at now. yes, the motor will not work as hard to spin a small pinion/larger spur.

yeah, I'm trying to find a good combo for my 14t Puller's.

I have one mounted to an Axial trans and a 55t (32p) is about the largest spur I can fit in the Axial trans cover.

The other 14t Puller is mounted to a Summit trans and I want a little more torque in 2nd gear.

[johnnyh66]

Originally Posted by reden

Low End, less inertia, weaker.
Top End, more inertia, stronger.

Engineering maths.

Bigger is stronger but difficult to turn. (accelerate)
Smaller is lighter but breaks easy.

Sorry, but I'm having a hard time understanding what you mean.

[badhoopty]

Originally Posted by johnnyh66

Sorry, but I'm having a hard time understanding what you mean.

the more meat you have on the gears, the more durable. but its also heavier and more rotating weight.

[badhoopty]

Originally Posted by johnnyh66

blasphemy!

im just sayin...

try stopping a semi truck wheel spinning at like 100rpm, then try stopping a bicycle wheel going the same speed.

remember tuff2 bmx wheels? those were hard as hell to get cranking on compared to some nice light arayas.

[johnnyh66]

I understand this part:

Originally Posted by reden

Bigger is stronger but difficult to turn. (accelerate)
Smaller is lighter but breaks easy.

but I'm not sure this:

Originally Posted by reden

Low End, less inertia, weaker.
Top End, more inertia, stronger.

means this:

Originally Posted by badhoopty

the more meat you have on the gears, the more durable. but its also heavier and more rotating weight.

[Olle P]

Originally Posted by reden

Larger pinion (14T vs 11T) would give more friction.

I'd say that's wrong.
With low teeth count the contact between pinion and spur will be more sliding/grinding while more teeth means pushing.
Sliding adds friction (most notable in the extreme case of worm drives where the pinion has only one or two "teeth").

A good engineering rule of thumb is to avoid using cog wheels with less than 12 teeth to get a smooth run and minimize friction.
If you want a smaller cog wheel just use a higher pitch (to get the same number of teeth within a smaller diameter)!

[Charlie-III]

If the ratio is always 5:1, the load on the motor is essentially the same regardless of the spur/pinion used.

Now to add on other posts, yes, there is a diffenence in rotational inertia. Heavier gears are harder to get going (slow accel) but maintain the spin once there (flywheel effect).
Due to the small size & weight of the parts in question, I wouldn't worry about it.

Now, the larger spur/pinion will likely have more & better tooth engagement which will reduce frictional losses a bit (very little bit) as well as transfer power better without breaking/wearing gear teeth. Tooth pitch will also have an effect on this. Finner teeth will be smoother, but more prone to damage if something hard gets in the mesh.