Gearing & Pinions?

[The Slayer]

Hi,

Another really 'Duh' question guys and gals..... Changing motor pinions - what IS that all about [8)] Too make it run longer, faster, or is there a happy medium... [8D]

Carolyn

[stulec52]

this is quite a complicated topic.

Basically- the bigger the pinion, as well as the smaller the spur gear, the more top speed the car will have.

the smaller the pinion as well as the bigger the spur gear, the better the accelaration.

Of course, if you have a higher top speed, you will also be putting more of a drain on the batteries.

Try to think of the gearing on a mountain bike. the chain ring being like the pinion and the gears on the wheel being like the spur gear.

after that it gets complicated.... best ratios to suit each motor / battery combination.... and running surface

best bet is to follow the guidleines in the manual, then go up or down a tooth or 2 to see the difference.

[The Slayer]

Ah - i see [xx(] so the spur gear chages as well OK, so with a standard gear, bigger pinion = longer running, slower speed, smaller = less running more speed [8)] I dont have a bike (unfit) []

cheers will try it and see...

[:X]

quote:Originally posted by stulec52

this is quite a complicated topic.

Basically- the bigger the pinion, as well as the smaller the spur gear, the more top speed the car will have.

the smaller the pinion as well as the bigger the spur gear, the better the accelaration.

Of course, if you have a higher top speed, you will also be putting more of a drain on the batteries.

Try to think of the gearing on a mountain bike. the chain ring being like the pinion and the gears on the wheel being like the spur gear.

after that it gets complicated.... best ratios to suit each motor / battery combination.... and running surface

best bet is to follow the guidleines in the manual, then go up or down a tooth or 2 to see the difference.

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[stulec52]

not sure what you mean by standard gear.

I would suggest trying a tooth or 2 more ( bigger) on the PINION first, see what that does to speed and runtime, then experiment from there.

If your motor gets really hot, then you are most likely over geared ( i.e. too big of a pinion and/or too small of a spur gear)

[SJoerD]

What would happen is you put in a smaller spur AND a smaller pinion, keeping the same gear ratio? My guess is that ratio-wise this wouldn't matter (of course). But what is the advantage and what the disadvantage of bigger or smaller gears? [?]

Bigger gears:

more rotating mass (probably insignificant?)

more teeth 'hooking up' each other at the same time meaning:

more drag from bigger surface?

less likely to strip a gear, as 5 teeth are stronger than 3?

smoother running due to a more natural angle the teeth follow (ever tried making a 5 tooth gear?)

Smaller gears:

the oppposite of above?

(on a pancar/F103) More ground clearance for the gears, picking up less dirt?

What else?

And what about the 0.8, 0.6 and 0.4 module gears (smaller or bigger teeht), is this a 'toughness' vs. 'smoothness' issue or isn't that all the gist in it?

With smaller teeth, you can adjust the gear ratio in smaller 'quantums' (you can't make pinions with 15.5 teeth to to have a compromise between 15 and 16 tooth [] ) Would that be considered advantageous or rather insignificant...?

[The Slayer]

The one that comes in the kits (the spur gear) coz most kits have a postion for X number of pinions.... I liked the bigwig, coz it had a slot so in theory you could try any pinion - from memory, still at least i now have a bit more understanding of this ratio stuff - knew it 20 years ago - but have forgotten (it's me age [8)])

Thanks Guys [:X]

quote:Originally posted by stulec52

not sure what you mean by standard gear.

I would suggest trying a tooth or 2 more ( bigger) on the PINION first, see what that does to speed and runtime, then experiment from there.

If your motor gets really hot, then you are most likely over geared ( i.e. too big of a pinion and/or too small of a spur gear)

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[DJTheo]

Bigger gears:

To avoid misundestandings lets say better more teeth but same module and gear ratio.

more rotating mass (probably insignificant?)

yes, yes

more teeth 'hooking up' each other at the same time meaning:

more drag from bigger surface?

No, gears are so designed that only 1 teeth should conatc at a time, ok 2 during the transition.

less likely to strip a gear, as 5 teeth are stronger than 3?

Nope, because of above.

smoother running due to a more natural angle the teeth follow (ever tried making a 5 tooth gear?)

Correct.

Smaller gears:

the oppposite of above?

Yes

(on a pancar/F103) More ground clearance for the gears, picking up less dirt?

Yes

What else?

Guess you did a good job! []

And what about the 0.8, 0.6 and 0.4 module gears (smaller or bigger teeht), is this a 'toughness' vs. 'smoothness' issue or isn't that all the gist in it?

Exactement, smaller module, smoother run and less friction but smaller transmitable maximum torque before excessive wear or damage.

Cheers

[stulec52]

all of which goes to show what I said at the top, It's a complicated topic !!!!

[GPZ1000RX]

Electric motors like to rev hard, they draw minimum current from the battery when spinning fast.

To maximize run time, gear low (like 1st gear on a real car)use a small pinion with a large spur gear. This will give best acceleration but a low top speed.

To maximise top speed, gear high (like 5th gear) use a large pinion with a small spur. This will give a high top speed but poor acceleration and poor run time.

Always err on the side of low gearing, on most tracks the acceleration is MUCH more useful! and you are putting much less strain on the motor, speed control and batteries.

Gear to high and you will run out of batteries before your race ends and you COULD damage the motor and speedo.

If you are trying a faster motor then you MUST gear lower!!!

You have been warned

Cheers, Paul.

[mud4fun]

Hey slayer, if you're talking about the thundershot then the spur is fixed and can't be changed - however your have a good range of pinions available. If you check out the motor mounting plate it is drilled and marked up for 13-17 pinions. You'll need a smaller pinion with any modern low turn motor, I spent months testing various combinations and the T'Shot will run an 11/12 turn with the 13 pinion, 14-17 turns on the 14/15 pinion and torquey motors like the meyhem or technigold will pull the 17 pinion. I generally run a 15 pinion with the technigold cos' it gives great acceleration and allows you to do hill climbs, donuts and wheelspins with ease.

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You are unlikely to get run times of over 10 minutes from a thundershot with any motor/pinion combination, certainly not at race speeds even with a 3300NiMH.

I can squeeze 15 minutes from a 3000NiMH using a technigold and about 20 minutes using a stock 540 but at bashing speeds rather than flat out. Cheers, Ian.

[The Slayer]

So smaller is better [:I] OK so i will have to go down with the Willy 2 when i do the Wheeler conversion - due to smaller wheels? yup Thundershot only using standard pinion at the momemt, still being built [:I]

[mud4fun]

LOL, well smaller is better if you want a quick burst........of speed that is [] but in your WW2 case if you're using smaller wheels then you can actually use a bigger pinion because the overall gearing of the car will have changed. Basically the bigger the tyre for the same size motor you need a smaller pinion (this applies in full size as well) but if you already have gearing suited to large tyres and you make the tyres smaller then you need to up the pinion in size or your motor will be screaming high revs and you won't be going anywhere very quickly!!

[stulec52]

http://www.arroyoc.com/

click on utilities

then scroll down to gear ratios

works out roll out and overall ratios for you, ideal when trying to compare similar motors in different cars !

[terry.sc]

quote:Originally posted by The Slayer

OK so i will have to go down with the Willy 2 when i do the Wheeler conversion - due to smaller wheels? [:I]

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Just to make things even more complicated the overall gear ratio amongst racers is referred to as millimetres per revolution - how far the car moves for one revolution of the motor. Ignoring the complexity of it lets say you have a 15 tooth pinion in the car and the tyres are 80mm in diameter. If you change the tyres to 60mm ones the car will only travel forward for 6/8 of the distance for the same size pinion.

To get the proper gear ratio back you must change the pinion for one that is 80/60 X 15 = 20 teeth.

In the case of changing Wild Willy wheels with Wheeler ones you will need to fit a larger pinion to get the speed back.

[stulec52]

it's known as Roll Out, not MMPR this side of the Atlantic.