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Old 08-25-2009, 07:21 AM
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Originally Posted by Danny-b23 View Post
4 Cell NiMH 4600's, 4 cell GTB, and a 60x40 track.
With your 13.5 I'd start at 70-75mm rollout and work my way up to 80-85mm paying attention to temps and lap times along the way. Our track is 65X40 so just a nick longer straight.

One of these years I have to make it up to Saskatoon and/or Regina. I know Bob has a great time racing with you guys.
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Old 08-25-2009, 07:59 AM
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while were on rollouts. what should i start with for a 10.5 brushless running 4600 4 cell batteries and a 4cell GTB. track is around 30 x 30 meters. i was thinking start around 50mm? and go from there

anyone agree/disagree?
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Old 08-25-2009, 08:40 AM
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Originally Posted by Scottrik View Post
With your 13.5 I'd start at 70-75mm rollout and work my way up to 80-85mm paying attention to temps and lap times along the way. Our track is 65X40 so just a nick longer straight.

One of these years I have to make it up to Saskatoon and/or Regina. I know Bob has a great time racing with you guys.
Ok, thanks.
Yeah, I've got to make it down to a race there. Maybe Minot.
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Old 08-25-2009, 08:48 AM
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@HaraR40: I would personally start with 45mm. Better to work your way up than the other way around. With working the roll-out up you can monitor heat better than starting high...
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Old 08-25-2009, 08:52 AM
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Originally Posted by Danny-b23 View Post
Ok, thanks.
Yeah, I've got to make it down to a race there. Maybe Minot.
As we always say, "Why not Minot?"

Their 2-day in December always has a GREAT 1/12 turnout (they're predominantly a 1/12 club).

Our own 2-day in March always has a very good 1/12 turnout. And is always a fair bit warmer.
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Old 08-25-2009, 09:03 AM
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Originally Posted by Joost K. View Post
@HaraR40: I would personally start with 45mm. Better to work your way up than the other way around. With working the roll-out up you can monitor heat better than starting high...
45mm it is. this is the first i've ever dealt with rollout since 1/10th tires dont shrink. what sort of temps is the motor allowd to reach?
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Old 08-25-2009, 09:12 AM
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Originally Posted by HaraR40 View Post
45mm it is. this is the first i've ever dealt with rollout since 1/10th tires dont shrink. what sort of temps is the motor allowd to reach?
For brushless 170*F is absolute max. Optimum is probably around 150-160.
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Old 08-25-2009, 09:42 AM
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Originally Posted by HaraR40 View Post
45mm it is. this is the first i've ever dealt with rollout since 1/10th tires dont shrink. what sort of temps is the motor allowd to reach?
I wouldn't be nervous at all starting at 60mm with a 10.5 on a 100' X 100' track and plan on working my way up to 70-75mm. Maybe stop a couple times in your first run and check the temps, but I'd say starting at 45 is a bit TOO conservative unless testing time is unlimited for you.

Originally Posted by Danny-b23 View Post
For brushless 170*F is absolute max. Optimum is probably around 150-160.
I'd certainly agree with this. The other thing I've seen is that temps creep up and creep up until you get to or past the gearing "sweet spot" at which point they seem to ramp up pretty quickly to those middle 150's and beyond. It also seems (this on medium-sized tracks anyway) that if I'm in the 150's that I'm MAYBE a bit faster, lap time wise, than at lower temps but that the acceleration has decreased enough that I'm having to really sweep my corners to make those times. That's fine on your own but leaving the inside THAT exposed when you're dicing for position is just BEGGING somebody to barge up the inside and either a) take the line away from you (best that can happen), or b) drill you in the side as you turn in.

That's where the compromises begin to creep in to setup choices.
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Old 08-25-2009, 12:21 PM
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Anybody have any idea where I can get some retardedly small 48p spur gears?
Like smaller then the Kimbrough 69T. 72mm rollout has me running a 32T pinion. I don't even think I can fit that on a 3.2R.
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Old 08-25-2009, 12:40 PM
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Originally Posted by Danny-b23 View Post
Anybody have any idea where I can get some retardedly small 48p spur gears?
Like smaller then the Kimbrough 69T. 72mm rollout has me running a 32T pinion. I don't even think I can fit that on a 3.2R.
Those SHOULD fit.

I was testing with my 3.2R over the weekend. I run 64p gears, but I had a 88T spur and 53T pinion combination in it at one point and was running pretty small tires (was down to 42.25mm at that point). The rollout I had at that combo was 79.94mm. These gears were about the absolute max that would fit and I had to clock the motor to one specific position to make that fit. One way of measuring that would be to add the pinion and spur teeth together to find a "max teeth" (not exact, but pretty close) and that is 141 teeth.

Your 69T spur (48p) would be equivalent to a 92T spur in 64p and your 32T 48p pinion is (roughly, rounding up 1/3 tooth...those 42.6666667 tooth pinions are NOISY SOB's) equivalent to a 42T pinion in 64p. That is only 134 teeth.

I think you should have a LOT of room to go. Well, a fair bit anyway.

I ultimately ended up with 78T spur, 54T pinion, (132 total teeth) and the tires were touched on the truer down to 41.5mm for a rollout of just over 90mm. Was testing 1s / 13.5 combos and it seemed like I still need to gear up a bit more but ran out of testing time.
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Old 08-25-2009, 01:08 PM
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It works. But I'm thinking the biggest I could go is maybe 34T without having the solder tabs hit the damper tube or the cross brace.
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Old 08-25-2009, 01:11 PM
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Originally Posted by Danny-b23 View Post
It works. But I'm thinking the biggest I could go is maybe 34T without having the solder tabs hit the damper tube or the cross brace.
I moved the damper tubes forward to clear the brushless. See my pics a few post back.

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Old 08-25-2009, 01:29 PM
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Originally Posted by Danny-b23 View Post
It works. But I'm thinking the biggest I could go is maybe 34T without having the solder tabs hit the damper tube or the cross brace.
With the motor THAT far forward I was able to "clock" the tabs back to where the "C" tab was actually under the top pod plate at the RR corner. This with my Novak motor which has had the fiberglass plate under the tabs trimmed so the tabs sit closer to the can. To do this (if you haven't already) straighten the tabs so they don't bend back along the can, CAREFULLY use your Dremel and cutoff wheel to trim the fiberglass backing tab so there's only about 1mm or so of fiberglass above the can even with the "B" (middle) tab. I stick a piece of servo tape to the can now to insulate the tabs from the can (leaving the backing on the other side of the tape) and carefully bend the tabs back down being careful to keep them parallel with each other.

If you similarly orient your motor you should be able to get at least a 36T pinion in there and quite possibly a 37T. That without re-locating the dampener tubes.

The key is that regardless the pitch of gears (unless I'm REALLY missing something) you SHOULD be able to get the same roll-out I'm getting.
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Old 08-25-2009, 01:56 PM
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Originally Posted by Scottrik View Post
I ultimately ended up with 78T spur, 54T pinion, (132 total teeth) and the tires were touched on the truer down to 41.5mm for a rollout of just over 90mm. Was testing 1s / 13.5 combos and it seemed like I still need to gear up a bit more but ran out of testing time.
I found that before I went to an adjustable boost/turbo esc that around 95mm rollout was best for 13.5. Now that I've switched to the Tekin I'm down to low 80's rollouts.
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Old 08-25-2009, 01:56 PM
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Originally Posted by Danny-b23 View Post
Anybody have any idea where I can get some retardedly small 48p spur gears?
Like smaller then the Kimbrough 69T. 72mm rollout has me running a 32T pinion. I don't even think I can fit that on a 3.2R.
Danny,

I just worked backwards a bit from the dimensions you've given here and find that you're talking about a 49+mm diameter tire?

69T Spur / 32T pinion gives a 2.156 gear ratio.

72mm rollout X 2.156 gear ratio = 155.232

155.232 / pi = 49.41mm tire diameter to get that rollout with that gear combo

This points to a couple problems. Firstly, "modern" tires are cut to 48mm out of the box, and most folks cut those a bit more to start out (commonly 45mm + or -). Secondly, as the tires wear you'll (obviously) need to gear up to maintain rollout.

Using the 36T pinion as the likely max you can fit in there with the 69T spur that means a minimum tire diameter of right at 44mm to maintain your targeted 72mm rollout. IF the 37T can fit you're still looking at a minimum a bit under 43mm.

You would definitely be better served with a smaller pinion because a) you can DEFINITELY run your tires smaller than that (and you want to!), and b) because I'm not convinced you won't want to be rolling out higher than 72mm once you've had the opportunity to test. If you ABSOLUTELY insist on sticking with 48p gears (64p really IS the better way to go in 1/12 for a variety of reasons) then RW Racing does offer a 58T spur gear. BMI indicates they have them in-stock http://www.bmiracing.com/webstore/ca...ee3d95a014ff99
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