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Old 04-03-2009, 11:56 PM   #1
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Default Advanced Brushless Motor Theory/Discussion/Facts

I've been wondering for a couple weeks about the topic of motor timing after I saw Trips (I think it was him at least) reference the idea of being able to determine the amount of motor timing built into various BL motors. I have also been experimenting with the rollout vs. timing and the balance between the timing in the esc vs the motor. I hear numbers tossed around about the different brand motors and how much timing each has built in (ie, I have heard either 0* or 9* for the SP and 0*, 10*, and 20* or 9*, 19*, and 29* for the Duos), but I haven't heard the information from a valid source.

I then read this post which spurred me to create this thread.

Here are a couple discussion starters . . .

1. Is there a way to, and if so, how do you, determine the amount of timing built into a BL motor? I'm not talking theory, but in practice, how can this valued be measured?

2. Are there any differences, aside from the obvious, between timing in the esc and timing in the motor? If so what are they and what are the advantages of each?

3. True or false and why: Increasing the timing the correct amount in higher wind motors used in lighter vehicles(such as 17.5 12th and the forth coming 17.5 1 cell 12th especially) is more critical than in heavier vehicles driven by lower wind motors. This is because cars in classes such as 17.5 12th scale rely on RPM more than torque to make it around the track quickly whereas the weight of a sedan requires the torque to get back up to speed out of the corners. This is somewhat analogous to the brushed days when we would have motors blueprinted and built for 12th scale differently than we would for our sedans.
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Old 04-04-2009, 12:35 AM   #2
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I think you're on to something about the heavier cars. The pan car guys seem to love the Tekin RS, but I thought it was a dog in my sedan. Now I'm running the SPX, and I'm ready to drop out of its profiles for "spec" motors and go back to how things used to be. All I'm finding with timing on my motors when they're in a sedan is that it slows down to about 80% at 4:00, runs hot no matter what, and isn't any faster up front.
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Old 04-04-2009, 11:10 AM   #3
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I have to disagree somewhat with the notion that lighter cars like pan cars benefit from high revs and heavier cars benefit from more torque.

In my opinion, regardless of the weight, a car will benefit from more POWER. Whether a particualr motor makes its best power at low or high RPM is of relatively little concern to me, as long as it makes the power sdomewhere, I'll gear the car to get into the powerband. Gears and pulleys are torque multipliers. If we had fixed gearing, or regulated gearing like VTA, then I'd re-think my attitude.

Most of the really good motor tuners I know have moved away from the tuning for torque or tuning for RPM idea and are tuning for the most power output. Sal Amato (who I have TREMENDOUS respect for, as a driver and motor builder) recently told me he tunes a motor the same for 1/12 as for touring, which had a big effect on my thinking along these lines. (That statement was regarding brushed motor tuning, but I believe it applies to brushless as well)

I was fortunate enough to race at 360 SPeedway with Sal Amato and Donny Lia and they run the Tekin RS the same in a 1/12 or touring application... motor timing as low as possible, max timinig in the ESC. There's no denying that they're VERY fast with either car.

Bottom line, give the motor with the most power output, let me know the RPM's where it makes its most torque and power, and I'll gear accordingly.

Last edited by Trips; 04-04-2009 at 12:10 PM.
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Old 04-04-2009, 12:01 PM   #4
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I have always been told that the reason for timing is that there is some lag for the magnetic field to generate so you advance the timing to start the process earlier.

As for pan vs TC, you were comparing different motors. It's the different motor winds that have different requirements, not the different cars. The only car difference would be that the lighter and lower drag pan car is putting less strain on the motor so you can put a little more timing and/or a little more gear before overheating the thing.
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