Can someone kindly explain pinion numbers to me please?

[nohero]

Sorry if this is simple to some, but reading up on motor choices for my Lunchbox and Holiday Buggy I am becoming confused on pinion numbers. I understand that the pinion size relates to the number of teeth, but what I do not understand is why in some threads I see it is recommended to change the pinion size if the motor is upgraded. Surely if for example my Lunchbox is 17 teeth pinion, that fits the larger gear inside the gearbox and that is all I need to know. If I upgrade the motor another 17t pinion is required or the original one swapped? Some threads I see for the holiday buggy have stated if upgraded the motor go for a 17 or 15tooth pinion? Wouldn't a change in pinion size means it doesn't fit the larger gear?

 

Confused!

 

I simply plan on getting something like the Tamiya Super Stock BZ for the Lunchbox fitting the pinion from the original lunchbox motor and then using that lunchbox original motor in the Holiday Biggy buy using the Holiday Buggy original pinion. Although that one seemed to come already attached to the motor unlike the lunchbox so maybe not changeable without further inspection!

 

 

[Deafty]

Well the Lunchbox only allow for one size pinion so that s likely to be your confusion?

[Stilli]

Until someone who knows what they're talking about replies let my shed some light.
Pinion and Spur (the larger gear) are a team used in combination to give a certain gear ratio and as long as the pitch (distance between the teeth) is the same any available size pinion can be used with the same spur to give the required gearing ratio. Different sized spur gears can also be used to the same effect but it is more usual to start with changing the pinion to 'up' or 'down' gear.
I am not familiar with the specifics of your car/motor combination but if for example you fitted a motor that works at higher revs than the existing one you have then you may need to 'gear down' (by fitting a smaller pinion) as the car may not handle the way you want and the motor may overheat while under stress from a too high gear ratio.
You can try it and see, if the car lacks acceleration, has a very high top speed and the motor overheats then you need to gear down by at least two teeth on the pinion. If people are recommending a lower gear ratio then that is probably why.

[nohero]

Right so that explains a large chunk of my confusion yes, but to clarify does that mean that some models will allow for different numbers of teeth? or does that require the larger gear to be changed too?

[nohero]

Thanks Stilli that makes sense, but less teeth is an option then? 

[Cherry]

Touring cars have different recommended gearing for different uses (drift/race) and for different motor types (number of turns) but often these are provided in the manual with a table of pinion size vs spur size and a reference list for ideal ratio range.

[Noj]

Certain Tamiya stuff has a one pinny and spur option (the Lunchie, old King Blackfoot for example), some allow for two different sized pinnys on the same spur (the DT02 chassis, for example) and others allow spur and pinion changes (tt01, tt02, for example).

In essence, it comes down to the design of the RC. Move away from Tamiya and you'll find motor mounts allowing adjustment for different sized pinions and optional spur gears listed.

[Deafty]

 

Edited August 3, 2015 by Deafty

[Cherry]

I think he was commenting on his own knowledge, Deafty mate, not yours.

[nohero]

I think you posted simultaneously so wasn't directed at you.

Thanks all makes sense.

Short version for my models currently is I can stick with the same pinion regardless of motor upgrade? Obviously as long as the upgrade is sensible.

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[Noj]

Yes, provided that your ESC is capable of taking your chosen turn number or kV (if brushless). Any number quoted in terms of motor turns (T) will be the maximum number that it will safely work with under normal usage (#)

So, we run vintage Blackfoots and LBs on 15t firebolt cans with etronix ESCs, 2s only, they never overheat.

The dt02 chassis will take the 19t pinny, pretty much any brushless can and never overheat (60a ezrun ESCs)...stick a 6000mah + 2s in and the runtimes are just ridiculous...

Personally, 15t in the LB is, IMO, daft enough. You've seen what happens to HB shells when run on 3800kv four poles....

(# it is possible to exceed the specified turn limit in certain applications with precise gearing calculations, before any smart arse brings it up, thinking I forgot )

[nohero]

Thanks Noj, helpful and clear

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