Motor braking. - Page 6 - RC-Monster Forums

Serum · 05.20.2007, 03:02 PM

Quote:

Is it not a good idea for ppl agree with me?

If you read my post better you would not post this question.
Selective reading abilities?

zeropointbug · 05.20.2007, 03:19 PM

Quote:

Originally Posted by Serum

If you read my post better you would not post this question.
Selective reading abilities?

It just sounds like your saying it's not wise to agree with me, i read it.

zeropointbug · 05.20.2007, 03:23 PM

Brian, did you short all motor phases? I would have thought it would make more of an impact. How big was this drill anyways? :005:

I will do a few experiments myself.

Serum · 05.20.2007, 03:08 PM

That's a nice experiment Brian; i would say the drill would stop; here is my experience with shortening the wires;

shorted the wires, put the shaft in the drill, and i was able to deanodize the motorcan with schotch brite; it was allmost impossible to hold the motor by hand, while my drill was doing a good 3000rpm.

BrianG · 05.20.2007, 03:26 PM

Which motor were you using and what rpm was the drill Serum? Like I said, I had the drill geared up through the tranny and it just slowed down, but didn't stop the drill. I first started by hooking the drill directly to the motor shaft and found it fairly easy to stop just by holding the motor bare-handed. Maybe my motor was not up to par??

BrianG · 05.20.2007, 03:28 PM

Yup, made a Y adaptor out of 12GA wire and used some extra connectors and connected all three phases together. Shorting just two of them resulted in a "detented" feel to the resistance.

The drill was nothing special; just a 3/8" drill. I think it was a 3/4hp rating.

Serum · 05.20.2007, 04:00 PM

Yeah, the motor i deanodized was a 7XL as well.

BrianG · 05.20.2007, 04:18 PM

Hmmm, even geared up through the tranny, I didn't get that much resistance. My drill also stopped pretty quickly when I removed the power, but there is a lot less inertia in a drill than there is in a 10lb truck moving at 30mph. Maybe it has something to do with the fact I used a 10XL, and you guys used a 7XL.

zeropointbug · 05.20.2007, 04:37 PM

I find that strange because you would think a 10XL would have more resistance.

How exactly did you de-anodize it without getting it into the motor windings? Would i be able to do it with my 540C 7XL?

BrianG · 05.20.2007, 04:40 PM

If I read his post correctly, he was using a scotchbrite pad to hold the motor and the abrasion wore away the anodixing off...

GriffinRU · 05.20.2007, 05:13 PM

I can explain to R&D engineer how it works and why, here we have other problems...

Post the Q and I will answer! But it is very difficult to explain how it works if there such big gaps in theory...

Bring, I am sorry but while your experiment is great, but the way how you explain what happen is really bad!

Do not treat it simple and do not make as complex as it looks..

BrianG · 05.20.2007, 06:16 PM

Quote:

Originally Posted by GriffinRU

...Bring, I am sorry but while your experiment is great, but the way how you explain what happen is really bad!

Do not treat it simple and do not make as complex as it looks..

Well, sometimes the answer is simple. I mean, if the FETs short the windings, how is that different than the experiment? The experiment would display the absolute most braking ability since there are no losses in other components since the windings were simply shorted, and there was no PWM action to reduce the effect. Please forgive the ignorance, but I am trying to learn the same as many people here.

zeropointbug · 05.20.2007, 07:06 PM

I agree with you Brian, that is the most it can do when shorted.

I think a better experiment would be to bring up to speed the wheels of a MT, and have motor connected with no ESC (motor is on motor mount). And then short them out and see how fast it slows it down. Keep in mind, it doesn't take much resistance further up in the drive train to slow things down wind (wheels).

The drill experiment shows lots of resistance, but that is a drill, and a drill only puts out more torque the slower it spins.... so it doesn't show us how fast it would slow it down. I'm thinking a flywheel experiment?

Artur, is there a diagram that you have, or COULD make that would show us exactly what is going on during braking in the FET; AND/OR when the voltage is high enough to charge batts?

zeropointbug · 05.20.2007, 10:55 PM

Just a thought, another way to brake an R/C car is to use alum. disc with neo magnet (disc type) and have a servo driven actuator to bring it into very close proximity to the disc. This creates tons of shaft resistance, and would not stress motor or anything. BUT, would not be super responsive as the servo would have to move it in and out. But would always work.

Serum · 05.20.2007, 05:19 PM

Less resistance zero;

the lower the KV, the less resistance it has, and the less energy it produces when turning. The higher the KV, the less resistance it has, and the more energy it produces when it's turning.

I did sealed the motor with tape, both the front and the rear. (so the bearings etc. where well protected)