Novak brushless SS 17.5 Pro

gopher69 · #1 02-11-2008, 05:45 PM

I'm not new to racing but I am new to brushless... what I am having a problem with is what to gear the Novak brushless SS 17.5 Pro in a FT T4. The directions say gear lower than what you would a 27t brushed motor at and people have told me to gear way high... such as 84 spur 27 pinion and I just think that is insane...lol I'm used to running a 27t geared at 87/18 or 19 depending on the track... I guess what I am looking for is a good starting point that won't fry the motor. Any help from anyone that knows brushless would be great!

Rich

Demon-TC3 · #2 02-11-2008, 06:11 PM

start arround a 24 and then you will end up going up - trust me, what novak tell you in this scenario is utter garbage.

it says i need to gear lower when going from 27 turn brushed to 13.5 brushless - i ended up going up 8 or 9 teeth on the pinion!

you cant gear too low, so start at 24 and see how it goes - then you will prob end up on a 29 pinion or something silly..

take care,
Demon

wmartinlsmith · #3 02-11-2008, 07:12 PM

bl=insanity... i cant wait to put a bl system in a duratrax st.. itll be balls to the walls.. till it pops.. LOL

ElectricThunder · #4 02-11-2008, 07:15 PM

What if, by lower, they are referring to the FDR? A numerically lower FDR is faster on the top end.

FYI- The SS13.5 with the sintered rotor can pull a final drive ratio of close to 4:1 in a TC3, so I have no doubts that the 17.5 with the same sintered rotor (which I do believe is what it comes with) can pull a VERY low FDR in a truck if you're using standard size tires).

burnineyes · #5 02-11-2008, 07:30 PM

I dont have the 17.5 but I do have a few other brushless motors and I can tell you its got to be next to impossible to fry that motor with the gearing you can fit in your truck and normal batteries.

GSMnow · #6 02-11-2008, 11:05 PM

The 17.5 is only 2200 KV, so you will need to gear it pretty high to match the speed of a good 27 turn stocker. It will only rev a tick over 15,000 rpm, and you really want to top 25 mph, even for stock class. If I remember right, the T4 has a 2.6 internal trans ratio. Let's give the tires an even 1 foot per revolution, mine are a tick bigger. So you want a tire speed of 2200 rpm or so.
2200 x 2.6 = 5720 rpm at the spur gear.
15,000 / 5720 = 2.6 pinion to spur, OUCH!! that is tall.
That is a 30 to 78. With an 87 spur, you need a silly 33 or 34 tooth.
Man, that is really going to make that motor work hard.

Maybe 25 mph is too much for a 17.5?? I am sure I have hit that with my CO27 stocker

gopher69 · #7 02-12-2008, 02:11 PM

Wow... thanks for the ideas and help! I'll mess around and see what I come up with.

Thanks again,
Rich

GSMnow · #8 02-12-2008, 02:19 PM

This sorta relates.
At the paved oval track here (Hot Rod Hobbies) they just switched their spec brushless pan car class to the 21.5 motor. The idea was to make 2S LiPo run about like a 27 turn stocker on 4-Cell NiMh. I have no idea how they are gearing, but I saw the time sheets still out there and they were running seriously fast lap times. It seems you can gear these high turn brushless systems to the moon.

bigboots1302 · #9 02-12-2008, 03:34 PM

everybody on my carpet offroad track gears their 13.5's like five teeth higher. i couldnt imagine that the 17.5 would be ant different.

gopher69 · #10 02-12-2008, 04:04 PM

The series that I race in (Factory Tracks Midwest Series) loosly follows ROAR rules and since ROAR has made 17.5 legal for stock class we have been givin the ok to run them also. I ran at our local indoor offroad track this past weekend and with my T4 geared at 84/27 I was a bit slower than the fast guys so I'm thinking I'll try something like an 84/29 or 30 and just keep an eye on the motor temp. Thanks again for being helpfull

Rich