Gearing a 17.5T BL

[joel45acp]

Ok, if my math is correct, my gear ratio spur/pinion is 2.86 ( 80/28). To get to a 1:1 ratio like you mentioned, I'd have to run about a 68/30 (2.27 ratio) for my 2.25 tranny in RC10 and 72/30 (2.40 ratio) in B2 with 2.40 tranny correct? Man, I really dig your help. I'm a bit lost and frustrated. thanks bro.

[JK Racing]

I was normally gearing 32/69 or 33/72 with my stealth tranny.

Give it more gear, still sounds like you are low.

General rule of thumb...3 teeth on the spur = 1 tooth on the pinion.

30/75 means you are about 4 teeth (on the pinion) lower geared than I normally ran.

In my TLR 22 (tranny @ 2.42, very close to your B2), I gear 35~37/72 for non timing 17.5.

[Charlie don't surf]

Ok, if my math is correct, my gear ratio spur/pinion is 2.86 ( 80/28). To get to a 1:1 ratio like you mentioned, I'd have to run about a 68/30 (2.27 ratio) for my 2.25 tranny in RC10 and 72/30 (2.40 ratio) in B2 with 2.40 tranny correct? Man, I really dig your help. I'm a bit lost and frustrated. thanks bro.

I meant closer to a 72/40

[joel45acp]

Reggie, could it be that this EZRun 17.5T sensorless motor just doesn't have much guts? I might consider a 13.5T motor. Hmmmmm.

[Charlie don't surf]

Yup, is a an esc/motor combo?

[joel45acp]

no, the motor and esc are not a combo. items were purchased separately. The HobbyPartz website indicates the motor is a 17.5T 2400KV, but the can is marked 17.5T 1900KV. I think the website is wrong.

[Charlie don't surf]

What speedo and battery are you using?

[joel45acp]

Reggie, I'm using the Hobbywing 35A sensorless esc set at max timing(26.25), max punch and a Gens Ace Lipo 4000mah 30C
http://www.hobbypartz.com/hobbywing-ezrun-35a-brushless-esc.html
http://www.hobbypartz.com/ezrun-sensorless-brushless-rc-motor.html
http://www.hobbypartz.com/98p-30c-4000-2s1p-hardcase.html
I truly appreciate your time and assistance bro.

[Charlie don't surf]

Not familiar with any of those parts personally- but using an LRP SXX II with a boost profile of 5 out of 8 and I set my throttle EXPO at +75% which gives me more umpf as soon as I breath on the trigger. Plus a trinity D3 17.5 and a SMC 60c pack and it will run with any unboosted 10.5 even in the long straight. If you are racing, I suggest you start with a better motor, sounds like your trouble- but the higher c in 17.5 really makes a difference

[joel45acp]

Thanks Reggie for your assistance. Hope you have a great work week.

[Charlie don't surf]

Hope you have a great work week.

I didn't know that there was such a thing

[joel45acp]

there is such a thing in my line of work. Just to let you know, I tested the motor again with 75/30 gearing. It gave me 22+mph consistently. That is up 3mph from the 80/30 gearing I tried. I know that is still slow compared to your sensored motors, but it's promising to say the least. I'll try 68/30, 70/30 next to see what I get. With the 75/30, my tranny slips if I punch it from a stand still. Thanks again for your insight.

[Charlie don't surf]

17.5 motors are all torque, no rpm. So as you start to get you gearing closer you are getting better punch, check your diff- sounds like its time to tighten or rebuild-

[RanchoJim]

Just bought some more pinions. I was running 81x21 (FDR=8.68) because I read the manual incorrectly for my setup. I'm going to try 81x30(FDR 6.08) on the next outing. Based on this thread 81x30 should get me more in the ball park of modern gearing. Glad this thread exists.

[ca-rj]

I've been running 32/81 with my 17.5 and the jellybean style wheels and it's been great. That's a 5.69 FDR. With 2.2's, I've had good luck with 30/75.