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Re: Torque vs RPM
Posted: Fri Nov 21, 2014 8:09 pm
by ALPHA
MichaelC wrote:Okay just found out that the motors I am using are 380s (?!?!) and 15,000 RPM. No torque numbers of any kind. The Brass gears are Mato 5 to 1 (?!?!?). So the question is, would I get better torque at a lower RPM if I swap out the 380s with HL stock, 400s or 480s ? (I am pretty sure the black ones I got are 400s knock offs and the red ones are 480 knock-offs).
For your Maus... I'd go with the highest torque motor you can find...not because of the weight of the tank.. but just because of the general layout of your running gear...the combination of your gears plus the motor ...will compensate for any minor deviation
Though if that tank were in my hands...I would make it work with stock everything first....because if you can run it with stock components it will run with anything
ALPHA
Re: Torque vs RPM
Posted: Fri Nov 21, 2014 8:31 pm
by MichaelC
Tankbear wrote:Another thought for Michael is have you got too small cable causing too much resistance or your battery not up to the job? Ian.
Well I went ahead and installed the 400 motors and see what happens. So funny Ian mentioned that since what I noticed is that when my old set-up get stuck, smoke start coming out of it. It is not the wiring, and I don't think it is the battery (Both pretty beefy).
Re: Torque vs RPM
Posted: Fri Nov 21, 2014 10:33 pm
by wibblywobbly
It might be an idea to check whether the gears are slipping on the shafts. I had this problem once with brass low ratio gears, I could hear the motors going but the tank would hardly move. The only way I could tell was to take the upper hull off, jack the tank up, and hold the tracks. If the gears rotate but there is little or no pressure on the sprocket then something is slipping in the transmission.
I have had, and seen, heavy tanks running without problems and using all sorts of motors and gearboxes, so it may be worth a look?
RobG
Re: Torque vs RPM
Posted: Fri Nov 21, 2014 10:37 pm
by MichaelC
wibblywobbly wrote:It might be an idea to check whether the gears are slipping on the shafts. I had this problem once with brass low ratio gears, I could hear the motors going but the tank would hardly move. The only way I could tell was to take the upper hull off, jack the tank up, and hold the tracks. If the gears rotate but there is little or no pressure on the sprocket then something is slipping in the transmission.
I have had, and seen, heavy tanks running without problems and using all sorts of motors and gearboxes, so it may be worth a look?
RobG
wibbly.......good call. That was my initial problem and I fixed it. Then it was the final drive gear slipping on the gear before which I also fixed. Now it just seems that the motors are not putting out enough torque to turn the gears. I installed the 400s today and will be trying it shortly and see what happens.
MichaelC.
Re: Torque vs RPM
Posted: Sat Nov 22, 2014 1:05 am
by tomhugill
ALPHA wrote:Tankbear wrote:Sorry Alpha more turns is higher torque and slower speed.
Ian.
Not at 12 volts lol...proved it many times...with airsoft motors...there are HT motors that did do what you say....but in those cases the windings weren't as thick and the magnets of lower quality....there is a motor made by a company SR...really lousy...the magnets no where near as strong as the JG ...and the windings poorly done...didn't reach near the rpm that the JG did
I suspect the same goes for RC cars... who's can motors aren't made half as well as an airsoft motor...
like I said... I've had this convo with a lot of "experts"...who's minds I've changed once I demoed for them
ALPHA
Ps...Explain to me why the SYSTEMA high speed motor has thinner windings ..more of them... and is not as powerful as the JG HT motor with thicker windings and less of them
....I can literally spin the SYSTEMA with my fingers... where the JG you barely can ...it's all about Magnetism...and how that is created and how that is generated into a pulse
And as I stated...in a rock crawler STOCK... the gear ratios is what affects the speed...add a speed controller and as far as slow goes...sky's the limit....airsoft guns have speed controllers too...never used them ...totally impractical
I'm confused. What do you mean by speed controller? Every electric motor is controlled by a speed controller. A speed controller can't give your motor more torque. A better quality one can give better throttle response.
I also don't understand how you can argue the motors not a factor when specific crawler motors have 1/3 rpm of a standard 540.
The lower KV (ie torquier) motors I've had always seem to have stronger magnets and therefore are harder to spin by hand.
@ Michael
Is your tank struggling in turns or straight as well? If your taking the gearboxes out it might be worth putting them back in without the motors and seeing if anythings snagging.
The Maus is pretty long and the tracks are quite close together, this will make very hard work on any rough surface.
Re: Torque vs RPM
Posted: Sat Nov 22, 2014 1:30 am
by ALPHA
tomhugill wrote:
I'm confused. What do you mean by speed controller? Every electric motor is controlled by a speed controller. A speed controller can't give your motor more torque. A better quality one can give better throttle response.
Speed Controller
....several different types for different apps ...I've seen some that look like volume controls...so you can actually dial in the resistance...any change in resistance cuts or increases current flow..so does affect the power output of any motor Ht or Hs
I also don't understand how you can argue the motors not a factor when specific crawler motors have 1/3 rpm of a standard 540.
The lower KV (ie torquier) motors I've had always seem to have stronger magnets and therefore are harder to spin by hand.
I'm not arguing anything about the motors...just defining HIGH torque vs High speed ...and how there is a myth about performance that exists
ALPHA
Re: Torque vs RPM
Posted: Sat Nov 22, 2014 2:32 am
by MichaelC
tomhugill wrote:@ Michael
Is your tank struggling in turns or straight as well? If your taking the gearboxes out it might be worth putting them back in without the motors and seeing if anythings snagging.
The Maus is pretty long and the tracks are quite close together, this will make very hard work on any rough surface.
Tom, both the Mato motors and the 400s I put in allow the gears to move while they are engaged so I did notice that one side is more snug than the others. After I put in the 400s, I definitely got more torque onto the tracks and was able to move but of course the snug side is slower on the up take given equal power.
I haven't even tried this outside, just inside on my wood floor. Can't see this baby doing much, but just want it to move okay. It appears that the 400s does have more torque at roughly the same RPM as the 380s, so looks like my problem is solved for now. Not the prettiest runner but it is moving, just like the real thing.
I am still curious to know the torque curve profiles on some of the more popular motors so that people can pick and choose. I would love to know which set has the highest torque at the lowest RPM for example. Stock HLs, 380s, 400s, 480s etc. Of course you will have to factor in the gear sets, but most folks would upgrade their motors so the gearset is the same in most cases.
MichaelC.
Re: Torque vs RPM
Posted: Sat Nov 22, 2014 6:10 am
by ALPHA
Michael...if you have a little space around your motors...and some scrap motors laying around that can be sacrificed...pull the magnets.. and glue them to the outside of the can of the ones you have installed in the gearboxes...this will increase the outer magnetic field and possibly give you that little umph you need
ALPHA
Re: Torque vs RPM
Posted: Sat Nov 22, 2014 8:48 am
by tomhugill
Can I ask what electronics your using Michael?
Re: Torque vs RPM
Posted: Sat Nov 22, 2014 9:03 am
by tomhugill
ALPHA wrote:tomhugill wrote:
I'm confused. What do you mean by speed controller? Every electric motor is controlled by a speed controller. A speed controller can't give your motor more torque. A better quality one can give better throttle response.
Speed Controller
....several different types for different apps ...I've seen some that look like volume controls...so you can actually dial in the resistance...any change in resistance cuts or increases current flow..so does affect the power output of any motor Ht or Hs
I also don't understand how you can argue the motors not a factor when specific crawler motors have 1/3 rpm of a standard 540.
The lower KV (ie torquier) motors I've had always seem to have stronger magnets and therefore are harder to spin by hand.
I'm not arguing anything about the motors...just defining HIGH torque vs High speed ...and how there is a myth about performance that exists
ALPHA
First off you can't increase flow of current, only decrease it. This will make a motor run slower at given throttle but won't increase torque (try it in your tank by wiring a resistor in series with the motor). Going back to v=ir for constant voltage increasing resistance decreases current.
Anyway back in the days of mechanical speed controllers that's how you varied speed, increase resistance and as I'm sure you know run at low throttle those things got aweful hot, I know people who had boats set fire using them.
The way an esc works now is by sending a series of pulses to the motor by varying frequency changes speed. Voltage remains the same.
Typically a motor will draw much more current when stalled than when running. This is because when running, it is also acting as a generator, creating an EMF which opposes the applied EMF and reduces the overall current. As more mechanical load is applied, the motor slows, the back emf decreases, and more current is drawn. If sufficient mechanical load is applied, the motor stalls/stops rotating, and therefore there is no back EMF at all, and the current is limited by the supply or by the resistance of the windings.