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Old 06-14-2014, 11:52 AM   #7606
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Old 06-14-2014, 12:17 PM   #7607
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Thanks Howard BTW I like the idea of terminal resistance, just thought they were doing it already in TECH inspections (at least they should have been) but perhaps not as a design spec.

I've been dynoing several 25.5 motors and so far there is only one that comes close to the BOSS 25.5 in terms of power, torque, and acceleration at the same or less amp draw. (BTW the D3.5 25.5 isn't the one).
I know some people are already measuring resistance in tech inspections. It's great as a quick check to make sure somebody hasn't "accidentally" left off a turn on the windings. There are also some organizations (like the BRL) that have their own minimum resistance for each motor type, and enforce it rigorously. I wouldn't expect ROAR to do that, since they currently have no rules in place for it.

What dyno are you using? I'm gathering the necessary items at the moment to make my own, but I always like to use suitable (and affordable!) pre-existing items. The biggest challenge is a suitable flywheel. I have one from a Robitronic, but it seems pretty light. We'll see if it will give enough data points on a spool-up.
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Old 06-14-2014, 12:27 PM   #7608
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With lap times like that, I assume the track is not huge, but still on the larger side. I think those results so more of what the difference in weight and battery do vs motor. Especialy since a Novak won the ROAR class. I would be interested in knowing what batteries were used in the ROAR class vs the 5000mah cap in USVTA.
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Old 06-14-2014, 12:38 PM   #7609
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But you can clearly see the roar VTA was faster ...
Yes, it's amazing what a 6.9% increase in power-to-weight ratio will do for a race car (when all accomplished via weight reduction, assuming equal motor power)! Thanks for posting the results.
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Old 06-14-2014, 12:52 PM   #7610
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I know some people are already measuring resistance in tech inspections. It's great as a quick check to make sure somebody hasn't "accidentally" left off a turn on the windings. There are also some organizations (like the BRL) that have their own minimum resistance for each motor type, and enforce it rigorously. I wouldn't expect ROAR to do that, since they currently have no rules in place for it.

What dyno are you using? I'm gathering the necessary items at the moment to make my own, but I always like to use suitable (and affordable!) pre-existing items. The biggest challenge is a suitable flywheel. I have one from a Robitronic, but it seems pretty light. We'll see if it will give enough data points on a spool-up.
I knew someone was doing the resistance thing for exactly the reason you mention, but after racing for 30 years I don't remember who it was.

I'm using the Fantom or as some call it the FACTs Machine dyno. I was looking into various dynos for brushless motors and decided to get the Fantom out of my son's attic and go with something I knew instead of building one. Pretty easy to use for brushless motors. You just have to hook the dyno to an ESC then hook the ESC to the brushless motor. You power the ESC with a receiver battery pack and use your Transmitter to control the ESC. IF you locate one there are more detailed instructions on the RC Conference at the deccosoftware website. I bought the new FACT MACHINE II software that runs on Windows based computers (through Windows 7) as I no longer have a computer that runs the old DOS software that comes with the Dyno.
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Old 06-14-2014, 12:54 PM   #7611
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Yes, it's amazing what a 6.9% increase in power-to-weight ratio will do for a race car (when all accomplished via weight reduction, assuming equal motor power)! Thanks for posting the results.
Think I was the only one to run both VTA classes, my roar car was 0.746sec faster then my usvta car, thats around 5% faster. Both cars ran 5000mah batteries, roar car had reedy motor.
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Old 06-14-2014, 12:59 PM   #7612
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Think I was the only one to run both VTA classes, my roar car was 0.746sec faster then my usvta car, thats around 5% faster. Both cars ran 5000mah batteries, roar car had reedy motor.
Yup, I had already run the numbers on your lap times. Thanks for the update on the batteries!
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Old 06-14-2014, 01:21 PM   #7613
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With lap times like that, I assume the track is not huge, but still on the larger side. I think those results so more of what the difference in weight and battery do vs motor. Especialy since a Novak won the ROAR class. I would be interested in knowing what batteries were used in the ROAR class vs the 5000mah cap in USVTA.
Yep I agree, and I not surprised the Novak 25.5 motor won as it looks very good on the dyno compared to just about any other 25.5 motor I've dyno'd. It just has to be geared correctly. Now there are only two big differences between ROAR and USVTA rules for VTA (the weight and the motors). Only serious complaint I have with the USVTA version for motors is the 45 degree rule for the motor - there is no way to really enforce it and entirely too easy to bet it. My BOSS looks a lot different at 55 Degrees than at 45 degrees (at least that's the timing on my label). (Illegal tuning stators in USVTA can be detected but that requires a tear down to be sure).
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Old 06-14-2014, 01:24 PM   #7614
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roar car was easier to drive and had fresh tires, with a little more work and fresh tires the TC3 could have been a little more faster/consistent. Either way it was a awesome weekend

roar 3.17 fdr @ 30* timing
usvta 3.35 fdr @ full legal timing

both coming off around 160-170F

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Old 06-14-2014, 01:30 PM   #7615
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With lap times like that, I assume the track is not huge, but still on the larger side. I think those results so more of what the difference in weight and battery do vs motor. Especialy since a Novak won the ROAR class. I would be interested in knowing what batteries were used in the ROAR class vs the 5000mah cap in USVTA.

Lol track is large and flowing 150 x 75
I used a 7200 and had the timing past the sticker a good bit
I figured WTH anything goes in this class of VTA why not
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Old 06-14-2014, 02:06 PM   #7616
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Lol track is large and flowing 150 x 75
I used a 7200 and had the timing past the sticker a good bit
I figured WTH anything goes in this class of VTA why not
150' x 85'
But what's a couple of feet amoungst friends.

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Old 06-14-2014, 06:06 PM   #7617
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As the slowest guy on the ROAR VTA class I did not have the correct gearing for my car. I will shortly. My car was and has always been powered by Novak(boss) with a 6000mah battery for this race. Normally I run a 5000mah battery and usually more competitive(at the upcoming nationals track with the gear I ran.
Pete I'll see you July5th with the new gear ratio and set-up (at kissimmee). WGT you can follow me around Kissimmee. I'm much better with a 2wd car. but you have an Excellence car to start with, If you need anything let me know- it runs great right out of the box as they say.
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Old 06-14-2014, 08:33 PM   #7618
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[QUOTE=rcpaintinpete;13335659]Lol track is large and flowing 150 x 75 QUOTE]

Big is relative, 150 is about the length of our back straightaway here, but things here in Texas are usually bigger.
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Old 06-14-2014, 09:01 PM   #7619
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I find it interesting that with the lighter weight and allowable bigger batts that the ROAR main was 2 minutes less time than the USVTA.
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Old 06-14-2014, 09:11 PM   #7620
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I find it interesting that with the lighter weight and allowable bigger batts that the ROAR main was 2 minutes less time than the USVTA.
It can be a bit like the way 12th scale was at one time, gearing too high can make for a car that fades as the heat rises and the pack drops off.
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