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Old 03-19-2008, 06:46 PM   #1
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Exclamation 17.5 Questions...13mm rotor? Better/worse?

how i understand it, 17.5 doesnt have as much RPMs as brushed but a ton more torque, so it can push through a really high gear ratio to make up for the difference and what ive seen is that on the pro-level, they dont have as much top-speed still as a good brushed motor (but are decently close).

so the 13mm rotors gives more torque and a little less top end (i think), so i figure more torque = more push for taller gearing to add more topspeed? Am i right or will it not work out too well?


edit: if this thread belongs in the Radio and electronics forum, can a mod please movie it there? Thanks.

Last edited by Syber Serulean; 03-19-2008 at 07:51 PM.
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Old 03-19-2008, 08:49 PM   #2
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I tried the 13mm rotor last weekend, I really didn't feel a difference.. It may make more of a difference with the lower wind motors but the 17.5 was exactly the same to me.
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Old 03-19-2008, 08:53 PM   #3
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ah...thanks

anyone else try it?

oh and Brian, hi! You race with my brother, Eric Arellano. Funny you posted here lol. I just posted in the Twister Tires forum not too long ago.
edit: noticed you saw it, im lookin at taht post now :P
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Old 03-20-2008, 07:07 AM   #4
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The bigger the rotor the more torque with less top RPM.

But if a motor only revs 20K RPm or even less i dont think you can feel it.

Also it is 12.10mm to 13.00mm, it's not that much really.

If it is Novak motor's but i asume so as no other are selling 17.5 already.
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Old 03-20-2008, 07:32 AM   #5
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Here's what I've found with the 13mm rotor.

In mod, the 13mm rotor is a great tuning aid and you can use it to move the powerband around a little. It's great for the light series motors. We gear mod closer to the peak efficiency of the motor so the motors don'e heat up as much with the lower winds (at least that's the case for me).

With the 17.5 and 13.5, I think the motor is less efficient with the 13mm rotor. It tends to heat the motor up more at the end of the run and the car falls off. Most of us club racers don't care but I don't think the 13mm rotor is ROAR legal for 17.5 or 13.5.
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Old 03-20-2008, 09:02 AM   #6
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Quote:
Originally Posted by Fred_B View Post
Most of us club racers don't care but I don't think the 13mm rotor is ROAR legal for 17.5 or 13.5.
It is not legal.

Club racers should care. Changing the rotor size is no different than changing the wire size or number of turns on a brushed stock motor.
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Old 03-20-2008, 11:32 AM   #7
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Originally Posted by Rick Hohwart View Post
It is not legal.

Club racers should care. Changing the rotor size is no different than changing the wire size or number of turns on a brushed stock motor.
Yes, that's true...it is against the rules assuming that your track specifies ROAR rules. The only problem with your analogy is that using a 13mm rotor in a 13.5 (or I assume a 17.5) Novak is that it makes them slower.

Maybe it's different with an LRP for some reason, but it's pretty obvious with the Novak...at least to me. So I guess it would be like changing the wire length...making it longer.
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Old 03-20-2008, 02:28 PM   #8
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I think Rick's point is that it might be different for some classes. Just because it's not faster for my class doesn't mean that it's slower in your class.

It's easy to tech so it's not that big of a deal.
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Old 03-20-2008, 03:12 PM   #9
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I give up. Let's turn stock class into a limited modified class with the only rule being the number of turns.
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Old 03-20-2008, 04:25 PM   #10
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Quote:
Originally Posted by Brian Bosley View Post
I tried the 13mm rotor last weekend, I really didn't feel a difference.. It may make more of a difference with the lower wind motors but the 17.5 was exactly the same to me.
Ha! I knew it....you cheater
When are you coming over again for a tail whippin'?
The track is nasty right now due to some dirty rain we had earlier this week, Ronnie and I are going to try to clean in tomorow.
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Old 03-20-2008, 04:25 PM   #11
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Originally Posted by Rick Hohwart View Post
It is not legal.

Club racers should care. Changing the rotor size is no different than changing the wire size or number of turns on a brushed stock motor.
Completely agree - it is simply "not legal"

Doing this defeats the entire purpose of the 17.5T class
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Old 03-20-2008, 05:29 PM   #12
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Quote:
Originally Posted by Fred_B View Post
Here's what I've found with the 13mm rotor.

In mod, the 13mm rotor is a great tuning aid and you can use it to move the powerband around a little. It's great for the light series motors. We gear mod closer to the peak efficiency of the motor so the motors don'e heat up as much with the lower winds (at least that's the case for me).

With the 17.5 and 13.5, I think the motor is less efficient with the 13mm rotor. It tends to heat the motor up more at the end of the run and the car falls off. Most of us club racers don't care but I don't think the 13mm rotor is ROAR legal for 17.5 or 13.5.
Hey I've got a dead wound 19 turn arm that's really a 17 turn that will make your 19 turn motor faster than a brushless 10.5. Doh ...... wait ..... that's illegal twice.

Why do people feel they need to cheat to be faster. Maybe you should put a 13.5 stator in your 17.5, that'll make it faster. Better yet, take your 13.5 and out a 17.5 lable on it. Clubs don't care when there racers stop comming because the club doesn't have the time, money our resources to tech BL motors at a club race and people are cheating. That will just go to support what the brushed guys have been saying all along, it's to easy to cheat with brushless.

Leave it to a few sour grapes to ruin it for all. You wonder why on-road is on such a decline? Go figure.
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Old 03-20-2008, 10:21 PM   #13
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seriously guys, rules are rules. run by them or don't run.

is the 13mm rotor legal in open mod?
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Old 03-20-2008, 10:42 PM   #14
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Quote:
Originally Posted by rocketron View Post
Completely agree - it is simply "not legal"

Doing this defeats the entire purpose of the 17.5T class
It's illegal...but it's slower...so I don't think it's gonna be anything that anyone needs to worry about either way. Ask the Novak guys and they'll tell you. Can't tell you about anything but a 13.5, but it's definitely way slower. Drives nice in the infield because of the drag, but it's SLLLLOOOOOOWWWW on the straights.

I can see it now..."Hey man, you're getting gapped by ten cars on the straight. We're gonna need to tech your rotor."
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Old 03-21-2008, 08:16 AM   #15
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Originally Posted by RussB View Post
seriously guys, rules are rules. run by them or don't run.

is the 13mm rotor legal in open mod?
Russ, 13mm rotors are legal in open modified.
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