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Old 01-16-2003, 08:35 AM   #1
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Default Drive frequency importance ?

How much difference do the drive frequency make in the real world? Is it more about feel of the car, or can a lower drive freq. actually make a noticably difference in acceleration?

In other words: Is it worth to sell my LRP v7.1 (3.140 Hz) and get another ESC? I'm driving stock class on very small and technically tracks so I need all the acceleration that I can get....

Maybe someone with a Novak Dually (or similar) can tell - that would be the ultimate test (same car, batteries, motor, track...)
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Old 01-16-2003, 09:08 AM   #2
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I was talking to a friend of mine that runs a tc3 and he liked the punch of the keyence speed control more than his Novak. We looked at the drive frequency and it was set different. I think the Keyence is 1.5 so we set our Novak's to the lowest drive frequency and felt the 2 were comparable. I think the Novak was at 2, not sure what or how low the Quantum can go. Just remember, the lower the drive frequency you probably will have to do more motor maintenance.

Mod however is a different story.
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Old 01-16-2003, 11:10 AM   #3
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I use the 730 hz setting on the Novak TC2 It gives the motor a little more punch out of the corners. Lower frequencis cause no further improvement. I have noticed no increase in motor wear. For Mod I use 1400 hz in a touring car on a high grip track. The 1400 hz frequency which is fairly low for mod makes the motor run more efficiently at part throttle to prevent dumping. It also give good part throttle response on a high grip track. I ran a TC2 at 730 hz, and it had noticeably more punch than a GM V12 run at 2000 hz which is it's lowest frequency. The differences are slight, however. If you have very good traction it might be worth it to change speed controls, otherwise you might not notice a difference. Have not run the GT7 yet.
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Old 01-16-2003, 01:24 PM   #4
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I'm running carpet only. But it sounds like I should get myself a newer car first. One with a ligther transmission, than my current Sport2 with gear diffs, hardend steel out drives and relative small pulleys.
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Old 01-16-2003, 01:24 PM   #5
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One more Q, are the runtime affected significantly by drive frequency?
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Old 01-16-2003, 03:20 PM   #6
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there's a topic on the GM forum about this,

ralf hellbing said that a lower frequency results in less smooth response but more power and also increased wear on the commutator. Any lower than 2khz and you will eat the comm.

I have a GM V12 and i can't feel the difference between 2khz and 4khz?!?

sanj
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Old 01-16-2003, 10:22 PM   #7
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Cole Trickle-The efficiency of the motor is increased using a lower frequency. The motor can take better advantage of the recirculating current at part throttle if it has enough time between power pulses. A lower frequency allows this extra time. A lower frequency will improve run time in mod but not a whole lot. I have been running 19 turn class and stock with a TC2 set at 732 hz and now 19 turn with a GM V12 set at 2000 hz. Comm wear is the same. Use a higher frequency to smooth the car out. A lower frequency for more punch.
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Old 01-17-2003, 12:02 AM   #8
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Just checked out the forum on www.GM-racing.com - german. I'm not that good at german....

Have someone done a regular test on this? It could be interesting with something like a "drag race" test, that is, measuring the time from zero speed to top end at the end of the straight.
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Old 01-17-2003, 12:16 AM   #9
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Cole what have you done to your car?

I believe that car mods will make a much bigger difference in your case, however a new car would probably save more money...... The Losi TC3, and Schumacher cars will all out accelerate your car with the same equiptment, unless you have sunk a ton of money into it........
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Old 01-17-2003, 02:10 AM   #10
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Quote:
Originally posted by IMPACTPLAYR
Cole what have you done to your car?

I believe that car mods will make a much bigger difference in your case, however a new car would probably save more money...... The Losi TC3, and Schumacher cars will all out accelerate your car with the same equiptment, unless you have sunk a ton of money into it........
You couldn't be rigther ! The parts I want to replace due to wear and the parts I want to upgrade the transmission and suspension, sum it up and it will easily pay a brand new car with alu and carbon and.....

However, I'm very interested in the drive frequancy thing and would like to hear other peoples experiences. Besides, one day sooner or later, I'll get a second speedo, so I can run my new car indoor and the Sport2 outdoors....
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Old 01-17-2003, 02:50 AM   #11
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Hi guys. Greetings from Malta.

I have been following this interesting thread.

I have often wondered about all these wonderful adjustments one can do on speedos.

I run GT7s in both my son's mod TC3 and my stock (21 turn) MR4 Sp. We ran TC2s last season and TCs the previous season.

I never tried playing with my own programmes except for including a bit of drag brake, simply because I felt I did not know enough about it. Instead I always got in touch with Novak and asked for their suggestions.

On Novak's recommendation we have my son's GT7 set on programme 1 (smooth mod), and my stock on programme 6.

Interestingly the Drive Frequency on these is 15 and 2 respectively. So the 2 looks OK for stock but what about the 15 for mod.

Reading through previous threads the impression is given that a lower drive frequency improves duration, so necessary in mod. Yet the lower DF programmes for the GT7 are all for fairly wild and aggressive applications. Common sense tells me that a "smoother profile" - with a DF of 15 in this case, as in GT7 programme 1 recommended for mod - should give better duration and so be more suited for mod.

Can we have some expert views please?

Regards

Joe from sunny Malta.
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Old 01-17-2003, 07:55 AM   #12
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Joe- you are correct! Lower drive frequency is punchier and higher is more efficient.....

Think of it this way who's batteries usually last longer the guy who is smooth on the throttle or the guy that uses his throttle like an on-off switch........
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Old 01-17-2003, 09:03 AM   #13
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huh..... i run 0.7 on my keyence and it felt much punchier compared to 3.5 or more ( 22khz is max)

and i use my trottle finger as smooth as possible

unless the surface is slippery i dont go up from 0.7 - 1.5 for stock
and 1.5 - 4 for mod
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Old 01-17-2003, 09:42 AM   #14
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Default Efficiency

I did some tests on a TC2 with a stock motor at light part throttle under a heavy load to see the effect of frequency on the currents that flow in the motor. I used an oscilloscope to view the results. On the vertical or y axis of the following photo of the oscilloscope trace is the voltage at the motor. On the x axis is time.

The speed control is just a rapid on off switch. Each time the speed control is on a peak rising upwards appears on the oscillocope at battery voltage. (full scale is 8 Volts or 2 Volts/ division). When the speed control is off a recirculating current arises in the motor (free current that does not come from the battery). It is of opposite polarity and is conducted by the Schottky diode. It shows up as a small negative peak that goes below the center of the graph. (The horizontal axis is set to 5 milliseconds/division)

This trace was obtained at 122 hz. Notice that there is plenty of time before the next on pulse arrives. All of the recirculating current is conducted so the motor is efficient at part throttle.
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File Type: jpg drive frequency 122 hz.jpg (45.8 KB, 293 views)

Last edited by John Stranahan; 01-17-2003 at 09:52 AM.
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Old 01-17-2003, 09:47 AM   #15
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Default TC2 at .975 kilohertz or 975 hz

Here is a second trace this time at TC2 at .975 kilohertz or 975 hz. A much higher frequency than the previous trace. Note the same basic shape of the pulses but now the recirculating pulse which goes below the center horizontal line runs into the next on pulse. There is not quite enough time for the recirculating pulse to be conducted at this frequency. This leads to reduced punch. REDUCED efficiency, but a smoother throttle response.

(The horizontal scale is 500 microseconds per division on this trace)

A higher drive frequency creates a smoother motor by creating inefficiencies in the use of the recirculating current.
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File Type: jpg drive frequency 975 hz.jpg (59.0 KB, 275 views)

Last edited by John Stranahan; 01-21-2003 at 08:09 PM.
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