General Pinion gearing explanation

[stokke]

Someone explain the basics of pinion gearing for me please.

I know that the main reason for changing pinion size is to achieve a targeted headspeed. But what I don't know is; how does it affect performance? Do you get more torque from using a larger pinion? What's the most effective way to go in terms of flight time? Is it possible to take out some of the strain on a ESC by changing pinion?

 

[coolgabsi]

Someone explain the basics of pinion gearing for me please.

I know that the main reason for changing pinion size is to achieve a targeted headspeed. But what I don't know is; how does it affect performance? Do you get more torque from using a larger pinion? What's the most effective way to go in terms of flight time? Is it possible to take out some of the strain on a ESC by changing pinion?

Well the larger pinion, the torque of the motor is sitting red over a larger area prevention main gear strips.

But a larger pinion also means higher head speed.
Now to achieve the same rpm you'll be rubbing the motor slower and yes relieve the system a bit, under no load, but

The system will have to work harder when load is required .. Or power is required, because a bigger pinion is a lower gear ratio ... (Say it goes from 9.8--->9.3 somehow) so in overall performance you loose torque and introduce bog


Think of it like car gears, when you need the most power -- stop to go.. You use the first gear.. That gear think of it like the smallest pinion which giver you the lowest rpm but the highest power and maxes out soon.. But no other gear can get the car the torque it requires to nice from start to stop than that little high gear ratio'ed first gear.

Installing too large of a pinion is think of it like car with 3rd gear.. When torque is needed that car engine will have to work twice as hard as the effective torque to the tires is less.. Over time on cruise, the engine will perform better when torque is not fluctuating and engine will be able to maintain speed without a lot of stress. Then think about 4th and 5th

Because we can't Change the gearing in a heli, we always try to figure out a gear ratio that will supply the torque when your blades are at 22deg of pitch cyclic and collective combined and.. Also when Just in the hovering or even fff or so it doesn't hand to keep the motor screaming while doing those simple maneuvers.


So in affect we look for the gear with a gear ratio that can almost behave like the second gear.. (In this analogy)

Fly safe!! have fun!

 

[stokke]

Thank you Gaba

So, you'd want the smallest pinion possible - but at the same time make sure it can deliver the headspeeds you want?

 

[coolgabsi]

Thank you Gaba

So, you'd want the smallest pinion possible - but at the same time make sure it can deliver the headspeeds you want?

Roughly yes

Use mr. Mel's calculator for calculating pinion size ... You want to make side you got head room at the highest rpm.. And aren't maxing out the motor screaming at 100% of its possible rpm at all times.

Fly safe!! have fun!

 

[Slobberdog]

That's a great way to put it Gaba, I now understand more than I thought I did before,

 

[stokke]

Roughly yes

Use mr. Mel's calculator for calculating pinion size ... You want to make side you got head room at the highest rpm.. And aren't maxing out the motor screaming at 100% of its possible rpm at all times.

Fly safe!! have fun!

You see, the reason for me asking is I'm trying to figure out which pinion to go with on the Goblin. The manual states to use a 21T pinion to achieve 2300HS. But when entering the gear ratio into MrMel (or Castle Gov setup for that matter), 21T is too small to achieve this headspeed. I'm ending up with at least 22T (Castle Gov states: "too little overhead") - but I think I'll go with 23T as this gives enough "overhead" for the Castle.

It's just strange that SAB would recommend the 21T, when this would make the motor work at 110% to achieve this HS...

 

[coolgabsi]

well. is the motor spec what SAB suggested? or is a different KV motor ? In your case.. being belt I dont know if that wil be a whole lot of a problem, but on geared helis like mine.. If on my motor I go 13t pinion, the main gear can get stripped by the motor cause of the torque. while 14t works fine. .so another factor I consider..

In your case.. like Castle says. you need good amount overhead. Mr Mel's calculator I rely on a lot.. as they graph it out

what motor you have and what gearing you have on the goblin ?

 

[stokke]

Data for Mr Mel (Marius' Goblin):

65C
12S
Main gear: 204T
Pinion: 21/22/23?
560 KV
Castle Gov

- - - Updated - - -



Cut out from Goblin manual

 

[coolgabsi]

If you want I can call a friend, he has a Goblin 630 too. he sold it ((. He had HKIII- 4035-560 in it, he sold the Goblin. His Goblin motor I actually I just installed in my Whiplash last night . (I had HK 4035-560, its now HKIII) .. not the point ))

BUt I can ask him what he used as a pinion on the Goblin and did he find the manual specs to be a bit off/ intersting ...

 

[coolgabsi]

Sent him a text. will hear back soon

 

[stokke]

Sent him a text. will hear back soon

Thanks buddy

 

[coolgabsi]

Ok here is his setup : HKiii 4035-560 with 22T pinion . He did not use Castle He Used Helijive. His target speed was 2300 he was at 2350 at 62 percent (Tons of head room)

 

[stokke]

OK, thanks. I'll have to check what the Castle says again tonight. I now have a 20T, 23T and a 24T in my possession LOL I'm sort of hoping I don't have to get a 22T too

 

[coolgabsi]

whoops LOL

 

[Lee]

Castle is a bit weird with the way there Gov works. I'm using a 17T to give me 2300 on throttle curve, but it asks for a 20T to give the same HS with the Gov.

 

[stokke]

Castle is a bit weird with the way there Gov works. I'm using a 17T to give me 2300 on throttle curve, but it asks for a 20T to give the same HS with the Gov.

So you're not using GOV then?

 

[Lee]

Nope. I'm running 100% flat

 

[stokke]

I powered up my ESC and tested out some values, I ended up with the 23T as discussed. See the Goblin thread for details.

Thanks for all your input.

 

[Tony]

If you are wanting the most snap out of the bird and the longest flight times, use a smaller pinion. Takes less energy from the motor to keep the blades spinning.

 

[coolgabsi]

If you are wanting the most snap out of the bird and the longest flight times, use a smaller pinion. Takes less energy from the motor to keep the blades spinning.

True ... While keeping in check the amount of torque the main gear teeth can take. Lol

Fly safe!! have fun!