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Old 12-10-2007, 09:44 PM   #16
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Originally Posted by miller tyme View Post
Instead you have:
1) Timing
Not really. All this does is move the power band a little bit. No tuning skills, special tools, or testing equipment needed. You just find the right rollout.
2) sintered, non-sintered
Drop in replacement. No tuning skills, special tools, or testing equipment needed. Sintered is the easy choice.
3) Ceramic bearings or not
Drop in replacement. No tuning skills, special tools, or testing equipment needed.
4) Rotor Diameter
Drop in replacement. No tuning skills, special tools, or testing equipment needed.
5) sensored / Sensorless
Most everyone runs sensored. Again, this is a purchase decision. No tuning skills, special tools, or testing equipment needed.
6) Zubak speed meter (as pricey as most brushed tools combined)
When heated up, Neodymium magnets hold their strength much better than ceramic magnets. People can race competitively with almost any sintered rotor because the variance is so small.
7) Not to mention no real means of dyno-ing
If you really want to dyno, you can dyno with a Turbo Dyno 45 and a brushless speed controller.

As someone mentioned before, the fact is, brushless racing has brought the field closer and the focus on driving skills and setup. This is good news for the hobby, as new racers don't have to spend hundreds on special tuning equipment and they don't have to invest hours of reading how to tuned motors.
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Old 12-11-2007, 08:31 AM   #17
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I dont realy understand why dynoing a brushless motor is necasary..
Not much you can do to tune them. Even changing the timing from what I have seen has not had any profound effects on them.
If a brushless motor is not performing (I have only seen a couple that have had any issues one being my 13.5) then you check the rotor and the ones I have seen with issues mine included needed a rotor replaced after that they where like new. Your not working with the many brush and spring combo's and the many hours on the dyno to get the best combo for a single motor for what 2-3 runs.....versus brushless you buy a motor put it in your car and race.

Now I know I would buy at least 3-5 motors a year ($150)and 2-3 comms ($45) then factor in minimum 2 pair of brushes a week ($12) and more for a big race.

Brushless lets see I buy a motor for $80 and maybee 1 rotor a year for $35..
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Old 12-11-2007, 08:44 AM   #18
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I honestly believe that not having to invest in expensive tools like a dyno and mag zapper brushless has evened up the palying field in the motor area....
I know it more then likely has some guys mad as hell because they spent a shit load of money on brushed tools and equipment so they could have a edge over the guy that was fast but didnt have the $$$ to throw brushess and springs etc to get a killer motor..
And it has actualy made some guys faster because by not having the fastest motors they worked on CHASSIS set up to make them faster and now with the motors being equal it in some cases has given the edge to the guy that has had to use his chassis skills to be fast
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Old 12-11-2007, 08:49 AM   #19
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The way of tuning motors just changed... Thats all thats happend.. We'll be doing it via laptop withen a couple years.
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Old 12-11-2007, 11:22 AM   #20
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The way of tuning motors just changed... Thats all thats happend.. We'll be doing it via laptop withen a couple years.
It has already happened. I change setting all the time with our aircraft escs. this doesnt change the overall WATTS like said in a previous post.
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Old 12-11-2007, 11:47 AM   #21
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doesn't mean it won't make you go faster.
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Old 12-11-2007, 03:33 PM   #22
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Originally Posted by James35 View Post
When heated up, Neodymium magnets hold their strength much better than ceramic magnets. People can race competitively with almost any sintered rotor because the variance is so small.
Just a piece of information with regards to this point - variations of 7-10% are not uncommon among the neo magnets used in motors, and we've seen even more on some unstabilized magnetic rotor assemblies (a recent prototype build at work showed 20% variation among 10 samples).

Permanent magnet strength can be "knocked back" to a more stable and consistant value either through slight reverse magnetizing (good) or heating the magnet to a temp slightly higher than the maximize expected operating temp (better). I don't know if any of the RC manufacturers are doing this.

Anyways, in response to the OP - assuming that one doesn't suffer a winding short or some sort of mechanical problem, the only thing that's likely to change over time is the residual induction ("strength") of the rotor. It's easy to check for this - just spin the motor shaft at a known speed (a Dremel spins about fast enough) and measure the back EMF (voltage) across any two terminals. If the magnet is getting weaker (likely because it was overheated), then you'll see less voltage at a given speed, and you may want to think about replacing the rotor (or at least gearing down the car, although that's not really a proper fix for the problem).

smoke81 is right - there's more performance to be had by optimizing the speed control, and I haven't seen any commercially-available controls that are yet providing this functionality (although I wouldn't be surprised if they're being prototyped by pro drivers in the form of those super-trick one-off ESCs that some folks are griping about).
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Old 12-11-2007, 03:38 PM   #23
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it may be true that the motors dont really have many or no tuning options, but I think its going to move to the speed control side as far as tuning goes. I think the future will bring speedo controls with endless tuning options.
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Old 12-11-2007, 04:15 PM   #24
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Originally Posted by James35 View Post
7) Not to mention no real means of dyno-ing
If you really want to dyno, you can dyno with a Turbo Dyno 45 and a brushless speed controller.
Works on a Robitronic Dyno too
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Old 12-11-2007, 05:06 PM   #25
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Quote:
I dont realy understand why dynoing a brushless motor is necasary..
I can tell you why...

KNOWLEDGE!

With ANY motor I'm racing...I don't car if it's in a Saturday Night HOT ROD Full Size automobile or my TOY car...if I'm going to race it - I want to know what I've got, and how to get the MOST out of it.

If I have 4 10.5 Brushless Motors and the DYNO Shows a 3% variance in the WATT output, I'm going to run the one with the HIGHEST watt output (POWER)

I can personally deal with a RPM variance as long as I know how much the variance is (I'll always take the higher POWER motor though)

A dyno also helps you create a 'benchmark'. If you have a motor that performs to your liking, and you hit the right rollout/gear ratio, it can be important to be able to document the performance of this motor for future duplication...or at least to help get you closer, quicker.

For instance, I just ran the NEW 21.5 NOVAK motor on a 820 ft. velodrome last weekend... and created the benchmark for racing this motor.

I know what the motor ran for lap times with what rollout, and I know that on a turbodyno45 this motor pulls approx 8500 rpm @ the test [email protected] 20 amps. I also know how many watts it tested at.

Now if/when I have the chance to compare this motor to a couple others...I'll know how/where to gear them if they show different numbers. Then we'll put them on the track and document their performance as well, and have a larger data base.
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Old 12-12-2007, 07:52 AM   #26
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SWT you have pm.
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Old 12-12-2007, 10:27 AM   #27
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SWT - Watts are not the ultimate sign of performance. I have a 19T with a short in the arm than pulls 18A at 2v. If I tested it, it would put out a ton of watts. Unfortunatly most of those watts go up as heat and not "go".

The big picture for BL motor performce is all about a balance of RPM, Wattage, heat.

I have been reading this thread and I know of a really good method of testing BL motors. I hesitate to post what it is because it involved R/C plane propellors and I can just see some one cutting off a finger or losing eye from thrown blade.
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Old 12-12-2007, 11:05 AM   #28
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Quote:
Originally Posted by AdrianM View Post
SWT - Watts are not the ultimate sign of performance. I have a 19T with a short in the arm than pulls 18A at 2v. If I tested it, it would put out a ton of watts. Unfortunatly most of those watts go up as heat and not "go".

The big picture for BL motor performce is all about a balance of RPM, Wattage, heat.

I have been reading this thread and I know of a really good method of testing BL motors. I hesitate to post what it is because it involved R/C plane propellors and I can just see some one cutting off a finger or losing eye from thrown blade.
I agree 100%, Watts does not neccessarily mean the best motor.
I can see someone cutting off there finger soon.
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Old 12-12-2007, 01:31 PM   #29
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Quote:
Originally Posted by AdrianM View Post
SWT - Watts are not the ultimate sign of performance. I have a 19T with a short in the arm than pulls 18A at 2v. If I tested it, it would put out a ton of watts. Unfortunatly most of those watts go up as heat and not "go".
In the case you describe here, the power measurement is input power, not output power (you said "put out", when really what you meant was "pull"). Ultimately, what we want is the most output power with the least input power, and to properly measure this, we need a known load. The dyno here at work uses a servo motor and a four-quadrant controller (essentially a very fancy BL motor and ESC that costs several thousand dollars), along with a torque cell to measure speed and shaft torque (that was another few thousand bucks).
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Old 12-12-2007, 01:45 PM   #30
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Quote:
Originally Posted by AdrianM View Post
SWT - Watts are not the ultimate sign of performance. I have a 19T with a short in the arm than pulls 18A at 2v. If I tested it, it would put out a ton of watts. Unfortunatly most of those watts go up as heat and not "go".
Watts is not how much juice is used. If you dyno'ed that motor, it would not produce a ton of watts.

Eric is right. It's not about how much amps a motor pulls. It's about horsepower (Watts of power it can generate at 7.2V).

HP (Watts) = RPM x Torque
746 Watts = 1 electric horsepower

Watts does mean the best motor. It takes into account both RPM and torque and reveals efficiency.

Last edited by James35; 12-12-2007 at 01:56 PM.
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