Advice on pinion gear size for hotshot 2.

[Super ally]

Hello, i am going to build my hotshot 2 kit and was wondering what is the best size pinion gear to use as it comes with 15t,16t and 17t.I want to put a steel pinion gear in it but can only find the 17t for it.Any advice would be great.Thanks.

[Guest]

No harm whatsoever in using the 17t steel pinion.

[MadAnt]

41 minutes ago, Super ally said:

Hello, i am going to build my hotshot 2 kit and was wondering what is the best size pinion gear to use as it comes with 15t,16t and 17t.I want to put a steel pinion gear in it but can only find the 17t for it.Any advice would be great.Thanks.

Robinson Racing makes steel metric 0.6 mod pinions. I think the part numbers you need are RRP1115, RRP1116 and RRP1117.

[ThunderDragonCy]

1 hour ago, MadAnt said:

Robinson Racing makes steel metric 0.6 mod pinions. I think the part numbers you need are RRP1115, RRP1116 and RRP1117.

Those are the wrong spec. Hotshots are 0.8mod or 32dp (pretty much same thing). RW Racing do steel 32dp 

[Super ally]

Thanks for your replies everyone.

[MadAnt]

4 hours ago, ThunderDragonCy said:

Those are the wrong spec. Hotshots are 0.8mod or 32dp (pretty much same thing). RW Racing do steel 32dp 

Whoops! My brain went dyslexic on that one. At least the options should be easy.

[Juggular]

7 hours ago, Super ally said:

what is the best size pinion gear

That depends on a few different things. 

1) The surface condition: You should use smaller pinion if the ground is rough.  Rough surface requires more torque, so it's better to use lower gearing (i.e. smaller pinion.)

2) Top speed: if you want faster top speed on flat surface, go with a larger pinion.  But know that larger pinion makes it weaker (i.e. it will take a bit to get to that top speed. Motor can heat up on an incline or rough ground). Hot motors get weaker over time.  

Sand, rough ground, grassy field, inclines = small pinion is better.  Flat, smooth surface for higher top speed = larger pinion is fine. 

Below doesn't apply to Hotshot family often. 

3) Larger tires work like larger pinion, so one should use smaller pinion.  Larger tires are heavier, so that also burdens the motor (needs a smaller pinion).  People get larger tires so they can go on rougher ground (needs a smaller pinion).  But swapping tires isn't easy on the Hotshot family.  

The gear ratio for buggies are generally about 7-9.  7:1 would have higher top speed, but weaker torque.  9:1 would be preferable on off-road applications.  For the Hotshot, 17t means about 7.5:1.  That's not terrible.  If you find that your motor runs hot on the surface you are using, just swap it out with a torque tuned (about 20% more torque and 10% higher RPM), or a Sport Tuned motor (about 35% more torque and 25% higher RPM).  Those motors are only about $15, so many people upgrade. 17t pinion should be perfectly fine for those motors on most surfaces.  

 

P.S.

I don't really like that manufacturers call "0.8mod = 32 pitch."  0.8mod is 31.75 pitch. Not exactly exactly 32.  If you install a 32 pitch pinion on a 0.8mod spur, you are installing 0.79375 mod.  Steel will wear less than plastic. The spur gear will wear slightly to fit the pinion, so it may work. That is a tiny difference. It's doable and many find no problem.  But I prefer to use the metric when if the gears are metric. 

For posterity, standard pitch is (T+2)/Outer Diameter.  So a 17t pinion of 32 pitch would have a diameter of 0.59375 inch = 15.08125mm. 

Metric module is Outer Diameter/(T+2).  So for a 17 pinion of 0.8 module would have a diameter of 15.2mm. I'm terrible at math, but 32 pitch 17t pinion should be 0.12mm smaller in diameter. 

That might not sound like much. But if you want to put in a M3 screw in a hole that is 0.12mm larger in diameter, you'd definitely feel that it's not biting well.  Individually, we can decide if we want to install 32 pitch on a 0.8 mod gearbox. That should be our informed decision. 

My problem is, when the manufacturers say "0.8 mod = 32 pitch" (to sell to either crowd), I cannot know they are selling 15.08125mm or 15.2mm.  I cannot make an "informed decision."  If I want to use a 0.8 mod pinion on 32 pitch gearbox, I might want to leave a bit more gap between the pinion and the spur.  If I use 32 pitch in a 0.8mod gearbox, I might reduce the gap.  I'm sure a piece paper method would work moderately well on either case (the gap should be a bit tighter than a piece of paper would allow).  But having to buy the pinion first, and then use a very precise caliper and do the calculation isn't how precise things like gears should be sold, in my opinion.  (Just to be clear, I'm not saying 0.8 and 32 shouldn't be interchangeable. That's our decision. I'm ranting about the sellers who do not indicate exactly what they are selling.)

 

[Juggular]

44 minutes ago, MadAnt said:

Whoops! My brain went dyslexic on that one. At least the options should be easy.

I respect the people who can admit the mistakes. They can learn, grow and improve anything they do. They are the real big guys in my book. 

 

[Super ally]

39 minutes ago, Juggular said:

That depends on a few different things. 

1) The surface condition: You should use smaller pinion if the ground is rough.  Rough surface requires more torque, so it's better to use lower gearing (i.e. smaller pinion.)

2) Top speed: if you want faster top speed on flat surface, go with a larger pinion.  But know that larger pinion makes it weaker (i.e. it will take a bit to get to that top speed. Motor can heat up on an incline or rough ground). Hot motors get weaker over time.  

Sand, rough ground, grassy field, inclines = small pinion is better.  Flat, smooth surface for higher top speed = larger pinion is fine. 

Below doesn't apply to Hotshot family often. 

3) Larger tires work like larger pinion, so one should use smaller pinion.  Larger tires are heavier, so that also burdens the motor (needs a smaller pinion).  People get larger tires so they can go on rougher ground (needs a smaller pinion).  But swapping tires isn't easy on the Hotshot family.  

The gear ratio for buggies are generally about 7-9.  7:1 would have higher top speed, but weaker torque.  9:1 would be preferable on off-road applications.  For the Hotshot, 17t means about 7.5:1.  That's not terrible.  If you find that your motor runs hot on the surface you are using, just swap it out with a torque tuned (about 20% more torque and 10% higher RPM), or a Sport Tuned motor (about 35% more torque and 25% higher RPM).  Those motors are only about $15, so many people upgrade. 17t pinion should be perfectly fine for those motors on most surfaces.  

 

P.S.

I don't really like that manufacturers call "0.8mod = 32 pitch."  0.8mod is 31.75 pitch. Not exactly 32.  If you install a 32 pitch pinion on a 0.8mod spur, you are installing 0.79375 mod.  Steel will wear less than plastic. The spur gear will wear slightly to fit the pinion, so it may work. That is a tiny difference. It's doable.  But I prefer to use the metric when if the gears are metric.  

For posterity, standard pitch is (T+2)/Outer Diameter.  So a 17t pinion of 32 pitch would have a diameter of 0.59375 inch = 15.08125mm. 

Metric module is Outer Diameter/(T+2).  So for a 17 pinion of 0.8 module would have a diameter of 15.2mm. I'm terrible at math, but 32 pitch 17t pinion should be 0.12mm smaller in diameter. 

That might not sound like much. But if you want to put in a M3 screw in a hole that is 0.12mm larger in diameter, you'd definitely feel that it's not biting well.  Individually, we can decide if we want to install 32 pitch on a 0.8 mod gearbox. That's our freedom.  My problem is, when the manufacturers say "0.8 mod = 32 pitch" (to sell to either crowd), I cannot know they are selling 15.08125mm or 15.2mm.  If I want to use a 0.8 mod pinion on 32 pitch gearbox, I might want to leave a bit more gap between the pinion and the spur.  If I use 32 pitch in a 0.8mod gearbox, I might reduce the gap.  I'm sure a piece paper method would work moderately well on either case (the gap should be a bit tighter than a piece of paper would allow).  But having to buy the pinion first, and then use a very precise caliper and do the calculation isn't how precise things like gears should be sold, in my opinion.  (Just to be clear, I'm not saying 0.8 and 32 shouldn't be interchangeable. That's our decision. I'm ranting about the sellers who do not indicate exactly what they are selling.)

 

Thanks for your very detailed information its very helpful.Can i ask if this pinion is ok for my hotshot 2.

[Juggular]

No, that's for a motor with a 5mm shaft (some 550 motors have 5mm shafts, but 540 motors we use have 3.175mm shafts -- yet another thing to watch out for).  

13t would give you a 10:1 ratio. Wouldn't that be too slow?  Trail rigs like CC01 or CC02 start with 10 or 11.  Buggies do fine between 7-9.  So 15t, 16t, and even 17t pinion should do fine.  

You can start with something like these, maybe?  These are 5 pinion sets, 0.8 mod for 3.175mm shafts.   Some have 3.175mm collars to fit into the 5mm hole. But I prefer pinions made for 3.175mm shafts.  

https://www.aliexpress.us/item/3256807748017246.html?spm=a2g0o.cart.0.0.523238dar8F4ZA&mp=1&pdp_npi=5%40dis!USD!USD 7.28!USD 7.28!!!!!%40210312d517450999328645360ecaf2!12000042929620910!ct!US!2630314545!!1!0&gatewayAdapt=glo2usa

 

[Super ally]

25 minutes ago, Juggular said:

No, that's for a motor with a 5mm shaft (some 550 motors have 5mm shafts, but 540 motors we use have 3.175mm shafts -- yet another thing to watch out for).  

13t would give you a 10:1 ratio. Wouldn't that be too slow?  Trail rigs like CC01 or CC02 start with 10 or 11.  Buggies do fine between 7-9.  So 15t, 16t, and even 17t pinion should do fine.  

You can start with something like these, maybe?  These are 5 pinion sets, 0.8 mod for 3.175mm shafts.   Some have 3.175mm collars to fit into the 5mm hole. But I prefer pinions made for 3.175mm shafts.  

https://www.aliexpress.us/item/3256807748017246.html?spm=a2g0o.cart.0.0.523238dar8F4ZA&mp=1&pdp_npi=5%40dis!USD!USD 7.28!USD 7.28!!!!!%40210312d517450999328645360ecaf2!12000042929620910!ct!US!2630314545!!1!0&gatewayAdapt=glo2usa

 

Thanks again.

[Super ally]

Just saw these on ebay.

[Juggular]

Sorry, I can't tell if that's 0.8 module or not.  All I could find out was that those optional pinions came out in 1990. Tamiya did prefer 0.8 module during that time. But the Manta Ray used 0.6 module.  Tamiya has been known to use all kinds; 0.6, 0.8, 32, 48, etc.  But they have not been very clear on which chassis use what. (Some of the newer chassis does mention it in the manual).  

They all look similar from the photos. But once you get them, there could be a substantial size difference.  

 

[Wooders28]

7 hours ago, Juggular said:

I'm ranting about the sellers who do not indicate exactly what they are selling

Even the reputable sellers get stuff wrong.

Modelsport have the pinions for the DF03 listed as 48dp, the DF03 is 05mod, and although close, not close enough so eats spurs...😳

 

 

[Super ally]

5 hours ago, Juggular said:

Sorry, I can't tell if that's 0.8 module or not.  All I could find out was that those optional pinions came out in 1990. Tamiya did prefer 0.8 module during that time. But the Manta Ray used 0.6 module.  Tamiya has been known to use all kinds; 0.6, 0.8, 32, 48, etc.  But they have not been very clear on which chassis use what. (Some of the newer chassis does mention it in the manual).  

They all look similar from the photos. But once you get them, there could be a substantial size difference.  

 

Ok thanks i wanted to be sure before i bought them but i will leave it in case they are not right.

[Twinfan]

9 hours ago, Super ally said:

Just saw these on ebay.

A Google suggests these are 0.6 mod, so not suitable for a Hotshot.

Unlike Juggular, I would recommend 32dp RW Racing pinions. In this instance, and in my experience, close enough is more than close enough and works perfectly well. As far as I know, Tamiya have never made steel pinions in 0.8 mod with 13/14/15/16 teeth. There is a 17T though, #54628.

[Andreas W]

If Tamico is a place you can order from they have Carson steel pinions in 08 mod.

[alvinlwh]

12 hours ago, Juggular said:

But if you want to put in a M3 screw in a hole that is 0.12mm larger in diameter, you'd definitely feel that it's not biting well.

Yes, it will feel slightly off with a M3 screw but if it is, say a M20 screw, I doubt there will be much difference 0.12mm will make. What I am saying is it is all about proportion. A 15 - 17t pinion is definitely bigger than a M3 screw and 0.12mm will be a smaller effect on something that size. On the flip side, 0.12mm will feel very wrong with a M1 screw. 

[Juggular]

16 minutes ago, alvinlwh said:

I doubt there will be much difference 0.12mm will make.

Since only one side of the diameter is touching, it will be half of that. I suspect that 0.06mm is within the envelope of mesh adjustability. Which is why most people would swap them fine, while @Wooders28 experienced 48 pitch chewing up 0.5 module spur gear (that difference is several times larger than 32 vs 0.6).  

 

[Wooders28]

21 minutes ago, Juggular said:

while @Wooders28 experienced 48 pitch chewing up 0.5 module spur gear (that difference is several times larger than 32 vs 0.6)

Moral of the story, don't just throw all your pinions into one 'pinion draw', as 48dp and 05mod are remarkable similar to the naked eye...🤦‍♂️🤣

[alvinlwh]

14 minutes ago, Wooders28 said:

Moral of the story, don't just throw all your pinions into one 'pinion draw', as 48dp and 05mod are remarkable similar to the naked eye...🤦‍♂️🤣

Which is why I prefer to get pinions with the mod/dp marked onto it. Of course storing them separately is the best practice. Failing that, I believe there are charts that you can measure and check gears to find out their pitch. For me, I try to change everything to 48dp when possible. Even when the car comes with a 64dp spur, I change it to 48dp. 

[Wooders28]

1 hour ago, alvinlwh said:

Which is why I prefer to get pinions with the mod/dp marked onto it. Of course storing them separately is the best practice. Failing that, I believe there are charts that you can measure and check gears to find out their pitch. For me, I try to change everything to 48dp when possible. Even when the car comes with a 64dp spur, I change it to 48dp. 

There are charts , but I'm way too lazy for that! 

Went with , in their own freezer bags, in said pinion draw.😎