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Old 03-18-2022, 05:12 AM
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You guys are going to think I am crazy but close to 120+/- rollout with that motor.
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Old 03-18-2022, 05:20 AM
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Originally Posted by MC Hamilton
For those of you running USGT fixed timing motors, do you have a suggestion for a starting point for gearing/rollout? We've been running open motor. Not sure where to start with the fixed timing stuff. Thanks.
We run the 21.5 Reedy FT with 45 pinion / 78 spur. I am told the USGT is comparable in performance.
We now run the USGT motor and open gearing.

Last edited by mrreet2001; 12-19-2022 at 05:29 AM.
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Old 03-18-2022, 11:30 AM
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Originally Posted by old_dude
You guys are going to think I am crazy but close to 120+/- rollout with that motor.
I was hearing crazy numbers like this, but didn't believe them. But from you, and now hearing it from a few sources, I need to test 100mm to 120mm. Racing in Bay City too, so the track is around 90 x 48 so let's see if this thing can push 130.

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Old 03-18-2022, 11:33 AM
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I did a few weekends of testing on 21.5 open motors. Tested from 80mm to 95mm rollout and ran the exact same lap times. At the lower end, it seemed to pull a little better in the infield, but wound out half way down the straight. At the high end, it felt good down the straight, but was flat everywhere else. Wondering if the fixed timing motors are all torque and no RPM so hanging the higher gear gets you there? I will have to run some data logging and see if I can isolate the difference.
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Old 03-18-2022, 11:47 AM
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Originally Posted by old_dude
You guys are going to think I am crazy but close to 120+/- rollout with that motor.
Yep!
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Old 03-18-2022, 01:19 PM
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120 on the rollout here also. 66/60-65 adjusted as the tire wears. Using the must run diff rule so the rings just barely clear the pinion teeth.
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Old 03-19-2022, 08:25 PM
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I tested 88 to 111. I didn't have a small enough spur gear (65 only) for the Awesomatix so max was 111. I also ran data logging and the fastest for the day was 107 rollout. It provided the fastest lap time and the maximum RPM at the end of the straights. Above 107 seemed to just lug the motor, never letting it wind out.

TQ and win today. Thanks for the starting point.
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Old 03-20-2022, 05:27 AM
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Originally Posted by MC Hamilton
I tested 88 to 111. I didn't have a small enough spur gear (65 only) for the Awesomatix so max was 111. I also ran data logging and the fastest for the day was 107 rollout. It provided the fastest lap time and the maximum RPM at the end of the straights. Above 107 seemed to just lug the motor, never letting it wind out.

TQ and win today. Thanks for the starting point.
It is very typical to not wind out a motor when geared right. If you see much over 75% of peak free rev rpm on your logger you are geared to low. PM motors drop in power dramatically after 50% of peak due to the torque characteristic. It is almost a linear curve from peak at zero to zero at peak. That is why peak power is at 50% pf peak RPM. It isn't just these spec motors. Every motor I have dynoed is that way. It is just a shift in curves based on wind, timing and the rotor characteristics. I am not a electrical motor engineer but I am sure there is some math that they know behind that that makes it predictive.
I came from big car racing and it was hard for me to learn at first how gearing works on these motors. When I try to explain it to someone new entering the hobby they face the same difficulty. I often hear that "I am going to gear down to get more punch out of the corner" I answer them with maybe you will and maybe you won't. Then enter the explanation to them about that power curve. With my racing and engineering background as well as a lot of instructing, I try to be a educator to them. I even have screen shots of dyno plots on the motors to help on my phone.
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Old 03-20-2022, 12:45 PM
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Originally Posted by old_dude
It is very typical to not wind out a motor when geared right. If you see much over 75% of peak free rev rpm on your logger you are geared to low. PM motors drop in power dramatically after 50% of peak due to the torque characteristic. It is almost a linear curve from peak at zero to zero at peak. That is why peak power is at 50% pf peak RPM. It isn't just these spec motors. Every motor I have dynoed is that way. It is just a shift in curves based on wind, timing and the rotor characteristics. I am not a electrical motor engineer but I am sure there is some math that they know behind that that makes it predictive.
I came from big car racing and it was hard for me to learn at first how gearing works on these motors. When I try to explain it to someone new entering the hobby they face the same difficulty. I often hear that "I am going to gear down to get more punch out of the corner" I answer them with maybe you will and maybe you won't. Then enter the explanation to them about that power curve. With my racing and engineering background as well as a lot of instructing, I try to be a educator to them. I even have screen shots of dyno plots on the motors to help on my phone.
To a point, yes, max RPM does not indicate max speed. There is a balance between speed and RPM efficiency. I ran six different gear ratios during the day and looked at throttle position, RPM, the RPM curve (did it climb at all in the full throttle segments of the data or did it drop off in the sweepers) and lap times. 88 mm produced the highest RPM (6500), but that's because the motor was running at top RPM around the whole track - and the slowest lap time. 107 produced the fastest lap times and a visible incline curve on the straights with very little drop off in the sweepers. Again, TQ and win so must have done something right.

The Tekin Hotwire data is useful, but could be so much better with some improvements to the interface and to the elements captured. A friend of mine was running a Hobby Wing and was able to get max RPM reading, but we could not see into the data to diagnose. Does anybody else make a better data capture setup?
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Old 03-21-2022, 05:31 AM
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Originally Posted by MC Hamilton
To a point, yes, max RPM does not indicate max speed. There is a balance between speed and RPM efficiency. I ran six different gear ratios during the day and looked at throttle position, RPM, the RPM curve (did it climb at all in the full throttle segments of the data or did it drop off in the sweepers) and lap times. 88 mm produced the highest RPM (6500), but that's because the motor was running at top RPM around the whole track - and the slowest lap time. 107 produced the fastest lap times and a visible incline curve on the straights with very little drop off in the sweepers. Again, TQ and win so must have done something right.

The Tekin Hotwire data is useful, but could be so much better with some improvements to the interface and to the elements captured. A friend of mine was running a Hobby Wing and was able to get max RPM reading, but we could not see into the data to diagnose. Does anybody else make a better data capture setup?
Yep, reading and understanding that data is the key. Tekin stuff could be great if the interface was better.
I was at at the GT challenge this past weekend and there were three nearly full heats for qualifying on a big track. Gearing had a huge range on the USGT motor but everyone was way over 100. I was to 128 but that fell in the end. My best was 121. Layout only had a couple tight turns.
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Old 03-21-2022, 05:38 AM
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Good GT12-R race this past weekend. The Von Perry GT Challenge for GT style of cars. The GT12-R class had 27 entries for a one day race and it was a good one. The A was stacked and hotly contested. The eventual winner was Brian Wynn (aka: Dumper) from CRC over Jody Flipse by .111 second. Positions 3 thru 7 were 1 lap down but only on the timer split. The racing was very close and the most important part was everyone had a blast. Thank you Scott for the tire that created a class.
Other classes running were WGT-R, FWD, GT-10 and USGT.
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Old 03-21-2022, 06:29 AM
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Originally Posted by old_dude
Other classes running were WGT-R, FWD, GT-10 and USGT.
That is GT-10? What was that? I am only seeing the rules for WGTr, GT12r, FWD and USGT.
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Old 03-21-2022, 12:41 PM
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Originally Posted by old_dude
Good GT12-R race this past weekend. The Von Perry GT Challenge for GT style of cars. The GT12-R class had 27 entries for a one day race and it was a good one. The A was stacked and hotly contested. The eventual winner was Brian Wynn (aka: Dumper) from CRC over Jody Flipse by .111 second. Positions 3 thru 7 were 1 lap down but only on the timer split. The racing was very close and the most important part was everyone had a blast. Thank you Scott for the tire that created a class.
Other classes running were WGT-R, FWD, GT-10 and USGT.
Jody and Greg Anthony race in Bay City with us. It's usually Jody, Greg, me and one other (Matt) fighting for the top spot. Always close racing and the winner is usually the one who made zero mistakes. Wish I could have made it down for Von's race. Might be able to make the Summer Classic at the Gate? Are there any other bigger events between now and then?
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Old 03-22-2022, 09:40 AM
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Originally Posted by mrreet2001
That is GT-10? What was that? I am only seeing the rules for WGTr, GT12r, FWD and USGT.
GT10 - rebirth Florida edition
It's a updated WGT, is how I look at it. I've only raced it once, but I like it a lot.
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Old 03-22-2022, 11:07 AM
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Originally Posted by mrreet2001
That is GT-10? What was that? I am only seeing the rules for WGTr, GT12r, FWD and USGT.
Last minute throw in. Didn't make his post.
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