Brushless Gearing Guide

[Kaizen28]

I thought I would post up this very cool little brush-less gearing guide.  Nice little program takes the guessing out. 

http://www.comeseethis.com/gearing/gearing.htm

[Tom G]

Thanks for the link.

Who comes up with the "Ideal Final Drive Ratio" values?  Isn't the final drive you're looking for also based on the track layout?

For my XXX-CR, the gearing I ran last night puts me at 'Excessively over-geared 8.55% off'
For my SC10, the gearing that I've been running for awhile is 'Excessively under-geared 7% off'

[Kaizen28]

Tom,

The final drive looks to be calculated as 2.6 with the SC10.  You can custom make them as well on that program.

[Pete D]

The transmission ratio is 2.6, but the final drive takes into account spur/pinion as well.

[Bagga 44]

you must also take into consideration tire diameter.

[Mikey]

I have found in offroad. that Brushless stuff isn't as sensitive to gearing up or down for diffrent tracks I typically run the same gear everywhere with BL. its not like brushed where a couple teeth make such a large diffrence. I try to find a gear that is fast but yet keeps the system cool and stick with it everywhere I go.

Also gear charts dont always work.. your best of too just start low and work your way up in gear. until it feels fast enough. especially with all the new speedos out right know with boosts, and timing on the motor it could be completly diffrent than any chart will tell ya.

just my 02

[Mikey]

I thought I would post up this very cool little brush-less gearing guide.  Nice little program takes the guessing out. 

http://www.comeseethis.com/gearing/gearing.htm

That is deff. the best gear chart Ive seen though.

[Tom G]

The final drive looks to be calculated as 2.6 with the SC10.  You can custom make them as well on that program.

What I was asking was about the 'Ideal final drive ratio' as listed on this site.  It says for a SC10 with a 17.5 motor the ideal final drive is 7:1, where does that number come from.  I understand it's a calculation between the pinion/spur and transmission ratio, but where does that come from.   I see it also changes when I change the turns on the motor.

I'm just not understanding where they get this ideal number.  All physics I guess.  It looks like it takes into account the standard HP/Torque type numbers that a specific turn motor is supposed to produce, tire size as Greg mentions (so it's different between a buggy and truck), and transmission ratios for the specific car.   It states the ideal ratio for the B4 and the Losi 2WD car are both 8:1 with a 10.5 motor.

[Pete D]

The "Ideal" number is just what has been agreed upon by people to be a good final drive for that class and motor, final drive doesn't have anything to do with transmission/spur/pinion, it's all based on how much torque vs. speed is generally wanted for that class(taking into account tire size), and what the specified motor can do for torque/rpm. Final drive is the ratio of rpm seen at the motor compared to that seen at the wheels, so 8:1 is 1/8th the motor RPM at the axles/wheels.

                   (Spur) (Transmission ratio)
Final drive =  _______________________

                               Pinion

Most trucks and buggies have a 2.6:1 transmission ratio(Associated/Kyosho/HPI) and Losi uses 2.43.

But the charts aren't always right, it says in my T4 I should have had an 18t pinion, and it says the 16 I ran was 13% under geared, but it got hot enough after every race as it was, but never "hot", I believe the 18 would have been pushing it a bit. Anyways, thought I'd try to clear up where they get the ideal final drives from, it's nothing completely technical, mainly just what they've found tends to work good for a specific motor in a certain class.

[Weeds]

I knew of the scriptsasylum one, but this one is new. Thanks. I've had an alternative to these gearing calculators in mind. When you are gearing your rc, chances are that someone, somewhere has already found a good gearing setups for your model and track. If people reported their setup, track conditions, and how the model performed, it might give you better results.

[Traxxas fan123]

i was like 0.8% off

[Randy D.]

I second what mikey said... the onroad guys put the new tekin software update in their cars and had to change out pinions ten teeth off, just from changing the program.  These are a good guide to get you started, just know you may need to tweak the pinion a little when you get to the track depending on what you have for gear

[RCEnthusiast]

I agree as well. More importantly, asking the guy next to you what gearing he's running only helps if you're running the same motor and possibly even the same software due to the dramatic differences between versions.