Super slow brushless

[Mr. ED]

maybe it's a brushless crawler moter

[vintage88]

its a 2 1/4 in rear tire and 110-34 gearing can anyone help me with this gearing??? problem????



thanks tim

[vintage88]

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]

no mr ed it isnt its the same combo toasted coastie used in project x and he said it was almost to fast...

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....

* edited to add: I read your post too quick, I thought it said it isnt the same, that's why I had put HAHAHAHAHA.

[vintage88]

oh ok lol thanks for chiming in tc

[Toasted Coastie]

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

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.

I had the same problem. All fixed now!

[Eau Rouge]

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.

[Coelacanth]

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!

[vintage88]

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

[aconsola]

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.

There's an app for that!
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]

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.

Nope, it's always been an issue. Just not much in the old days because we all ran the same size tires.

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.