
Super slow brushless
- Mr. ED
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Re: Super slow brushless
its a 2 1/4 in rear tire and 110-34 gearing can anyone help me with this gearing??? problem????
thanks tim
thanks tim
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Re: Super slow brushless
no mr ed it isnt its the same combo toasted coastie used in project x and he said it was almost to fast...
- Toasted Coastie
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Re: Super slow brushless
I actually pulled that 4900Kv system out of Project X and put an LRP 13.5T Eraser brushless in there instead. The 4900 was just too much for the transmission I think. Kept making messed up grinding noises....vintage88 wrote:no mr ed it isnt its the same combo toasted coastie used in project x and he said it was almost to fast...
* edited to add: I read your post too quick, I thought it said it isnt the same, that's why I had put HAHAHAHAHA.
- Toasted Coastie
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Re: Super slow brushless
AH! When I was setting up the 4900, I had to do the same thing. Switch two of the leads. If they are backwards (on the Reedy), then your forward is actually the reverse, which is really slow. Check them out.rc10johnny wrote:sometimes on new motors I have had a few that were slow so I reversed the polarity and made a 100% difference. Just a thought. JohnnySr
I had the same problem. All fixed now!
- Eau Rouge
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Re: Super slow brushless
So I see we have a lot of math geeks out here who jumped at the chance to help you figure out the rollout needed.
Ok, so it looks like you are WAY off on your gearing. The suggested starting window for a 9.5t brushless is right around 43mm of rollout.
So, rollout is the distance the car will move for each rotation of the motor. We need to get you into the 43mm range with that motor, so we'll keep the spur at 110 and the tires at 2.25" or 57.15mm.
Rollout = tire circumference (tire diameter x 3.14) by the spur and pinion gear ratio
43 = (57.15 x 3.14) ÷ (110 ÷ X) then solve for X to give you the starting point for your pinion.
43 = 179.45 ÷ 4.23
The required pinion to get you to a starting point window is a 26t pinion. You were 8 teeth off, which on a pan car is a mile! Before reversing any wires from the factory locations, try using the correct gear ratio and go from there. You should be a lot closer than you were before.
And shame on whomever sold you the new electronics for not explaining that to you in the first place.
Good grief, I'm giving math lessons. We're all fubar'd now.



Ok, so it looks like you are WAY off on your gearing. The suggested starting window for a 9.5t brushless is right around 43mm of rollout.
So, rollout is the distance the car will move for each rotation of the motor. We need to get you into the 43mm range with that motor, so we'll keep the spur at 110 and the tires at 2.25" or 57.15mm.
Rollout = tire circumference (tire diameter x 3.14) by the spur and pinion gear ratio
43 = (57.15 x 3.14) ÷ (110 ÷ X) then solve for X to give you the starting point for your pinion.
43 = 179.45 ÷ 4.23
The required pinion to get you to a starting point window is a 26t pinion. You were 8 teeth off, which on a pan car is a mile! Before reversing any wires from the factory locations, try using the correct gear ratio and go from there. You should be a lot closer than you were before.
And shame on whomever sold you the new electronics for not explaining that to you in the first place.

Good grief, I'm giving math lessons. We're all fubar'd now.

- Coelacanth
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Re: Super slow brushless
Has this move to calculating correct pinion gearing for motors in consideration of tire circumference arisen due to the predominance of truggies and "monster-truck-style" RC cars over the past decade? Tire circumference never seemed to matter that much back in the 80's; now it's a primary factor in the calculation of a 'safe' gear ratio.
It seems like every RC car I see for sale on Craigslist and Kijiji are those fugly truggies with waffle tires.
From a muscle-car lover's perspective, I can actually understand that reasoning. There are a few shameful people out there who will upsize muscle car wheels to ridiculous low-profile rims with virtually no rubber in the sidewalls--and then wonder why their speedos are reading way lower than they're actually going, and they find they're missing all their torque and low-end power!
It seems like every RC car I see for sale on Craigslist and Kijiji are those fugly truggies with waffle tires.

From a muscle-car lover's perspective, I can actually understand that reasoning. There are a few shameful people out there who will upsize muscle car wheels to ridiculous low-profile rims with virtually no rubber in the sidewalls--and then wonder why their speedos are reading way lower than they're actually going, and they find they're missing all their torque and low-end power!

Completed projects: CYANide Onroad Optima | Zebra Gold Optima | Barney Optima | OptiMutt RWD Mid
Gallery - Coel's Stalls: Marui Galaxy & Shogun Resto-Mods | FrankenBuff AYK Buffalo | 1987 Buick GNX RC12L3
Gallery - Coel's Stalls: Marui Galaxy & Shogun Resto-Mods | FrankenBuff AYK Buffalo | 1987 Buick GNX RC12L3
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Re: Super slow brushless
thank you very much doug i feel a little smarter now lol
i really appreciate the help ill let you know as soon as i get it together.
tim

tim
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Re: Super slow brushless
There's an app for that!Eau Rouge wrote:So I see we have a lot of math geeks out here who jumped at the chance to help you figure out the rollout needed.![]()
![]()
![]()
Ok, so it looks like you are WAY off on your gearing. The suggested starting window for a 9.5t brushless is right around 43mm of rollout.
So, rollout is the distance the car will move for each rotation of the motor. We need to get you into the 43mm range with that motor, so we'll keep the spur at 110 and the tires at 2.25" or 57.15mm.
Rollout = tire circumference (tire diameter x 3.14) by the spur and pinion gear ratio
43 = (57.15 x 3.14) ÷ (110 ÷ X) then solve for X to give you the starting point for your pinion.
43 = 179.45 ÷ 4.23
The required pinion to get you to a starting point window is a 26t pinion. You were 8 teeth off, which on a pan car is a mile! Before reversing any wires from the factory locations, try using the correct gear ratio and go from there. You should be a lot closer than you were before.
And shame on whomever sold you the new electronics for not explaining that to you in the first place.![]()
Good grief, I'm giving math lessons. We're all fubar'd now.
I have http://www.heizersoftware.com/?page_id=137 on my iphone. very useful at the track to compare gearing between different brands which have different trans internal ratios.
- Eau Rouge
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Re: Super slow brushless
Nope, it's always been an issue. Just not much in the old days because we all ran the same size tires.Coelacanth wrote:Has this move to calculating correct pinion gearing for motors in consideration of tire circumference arisen due to the predominance of truggies and "monster-truck-style" RC cars over the past decade? Tire circumference never seemed to matter that much back in the 80's; now it's a primary factor in the calculation of a 'safe' gear ratio.

In carpet/pan cars, or anything with foam tires where the diameter of the tires change as the tire wears (or is trued down), you have to pay attention to the rollout. With a rubber tire, the tire size is usually a constant.
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