We are having problems with our elevator motor. We are using a 550 motor with a 16:1 P60 gearbox and for some reason it only spins occasionally. We are controlling it with a jaguar and whenever the operator pushes the button to activate the motor the jaguar gets signal but the motor doesn’t always move. If we get it starting by pulling the belt, the motor will start working but without that it is very inconsistent. Any ideas?
You don’t have enough torque available to the belt. That’s what is probably causing the motor to bind up before you apply a little starting pull. If that’s what the problem is, your pattern will probably be something like:
Full battery, fresh off the charger, it works.
After a couple minutes, it doesn’t work if there’s a ball in there, but runs unloaded.
A minute or two after that, it doesn’t work without the pull-start.
You’re probably going to want to add another 550, or upgrade to a 775 or one of the AM motors.
Actually I think he’ll want to swap the 16:1 gearbox for another gearbox with a higher reduction. Probably somewhere in the neighborhood of 64:1 for the RSS775-18 and 128:1 for the RS550. However that really depends on how hard it is to push up your elevator lift… IE how heavy it is.
Swapping out for a higher ratio gearbox for the 550 would probably be easiest if you had one on hand…
Like Eric said, you don’t have enough torque to move your lift. Electric motors have a “start-up current” that is higher than the normal current it draws. Since your motor is under such a high load it cannot electrically overcome the initial resistance. When you move it,physically you are physically providing the force the motor needs to startup.
It sounds like you are saying that a brushed DC motor outputs more torque when moving than when stalled. That’s not what you meant, is it?
I believe I am trying to say that there is more resistance at rest than when moving for the motor.
Correct me if I am wrong.
I think by “resistance”, he means “inertia”. The motor isn’t able to provide enough torque to overcome the inertia on startup; if an outside source provides some force to overcome some of that inertia, the motor can run the system just fine.
There is little or no resistance in the motor itself.
Are you referring to static friction in the gearbox?
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I was trying to refer to the combination little to no resistance in the non-moving motor and the friction of the system.
Three thoughts:
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inertia, unlike friction, can’t stop a force or a torque. it can only slow it down.
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inertia is constant. it doesn’t change when something is moving vs stationary
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a brushed DC motor’s torque is maximum when stalled
That seems reasonable. The motor has trouble overcoming the static friction of the load. Pulling on the belt changes to kinetic friction, which is smaller.
Don’t know whether or not that’s what’s actually going on here, but it’s a working hypothesis.
Besides the fact the a 16:2 P60 gear box is not really good for lift applications, with bag & tag / shipment on Tuesday, here are some options.
If you don’t have a higher gear ratio P60, then you need to increase the overall gear ratio. Reduce the sprocket size on the motor and increase the other.
I have assemble and disamebled thes P60s numerous times and found that ever now and then the smaller ones tend to bind up easily when tightening the screws. Make sure that the motor mount and shaft plates stay flat. Tigheten as though you were doing your car wheels in a cross pattern. Don’t tighten up in CW or CCW pattern like some do. That will bind up the gear box and prevent it from turning.
Hope this helps.
Good luck
Some suggestions:
Run the motor/transmission when disconnected from your collector. If it still behaves the same, disassemble and look for debris mixed in with the grease. We had a plastic chip get into the gearbox and made it behave similarly.
Run the motor from a bench power supply, if you have one. With a 26:1 banebots transmission and an RS550, we see about 2.8 Amps with no load. Note that it will start 1/2 to 1 amp higher, and slowly drop down as the gears wear in a bit. If you see a higher current, you may have the internal binding that someone else mentioned.
-Jeff
Burke,
The P60 gear boxes need some time to break in and run freely. If you just grease it and run it, the gearbox will bind up and take a lot of the power.
I recommend greasing up the P60, then running it for about an hour - 30 minutes in each direction. For the first few minutes, keep a watch on the temperature of the gearbox and motor, if either gets too hot to hold, stop and let it cool down.
After this break-in period, disassemble the gearbox, clean it well, and re-grease it.
A great KOP solution is the AndyMark PG71 motor that already has a 71:1 gear ratio. You just need a coupling for the 10mm out put shaft. Also, these gearboxes have mounting holes for a face mount, as opposed to the P60 that has mounting holes on the side of the gearbox. AM sells a hub that mounts directly on the output shaft or a shaft adapter for mounting into the half inch hubs or sprockets that most people have.
Beyond the immediate motor/gearbox situation, is there some way you could reduce the amount of force it takes to lift the arm? Perhaps a counter-force (spring, gas strut, etc.) to counteract the basic load. That way you could still move the arm at relatively high speed without overloading the motor/gearbox.
Thanks for the tip above (Don Rotolo) for the Banebot P60 break-in procedure - let me add some background information.
A newly shipped transmission from Banebot (or any new transmission for that matter) should have high friction (difficult to turn) until it has experienced some running time, called “break-in”. This procedure is standard in industry although may be unfamiliar to high school students.
For our “break-in” procedure for the P60 Banebot transmission we used this year for our ball roller, this is the procedure we followed:
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Disassembled P60 Banebot (64:1) trans and greased thoroughly. Reassembled. (Note: I received 2, Banebot transmissions, one labeled greased, the other needed to be greased. We disassembled both and the one labeled greased seemed to have very little or no grease).
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Place transmission into vise for support. P60 trans has keyed, 1/2 shaft. Attached hand drill with 1/2 chuck to trans shaft. Spun one direction, then reversed. Performed this procedure a number of times. Upon completion of this procedure, disassembled, greased and rerun again for very short period of time. Hand drill may add some burrs to the hardened P60 shaft that will need to be filled smooth after this procedure.
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Observation 1 - one minute of this procedure resulted in a significant decrease in friction.
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Observation 2 - if grease is overfilled in transmission by student (hint), during break-in procedure the excess grease spews out of the motor mounting holes like toothpaste.
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Observation 3 - transmission did get hot to the touch during procedure. May have been due to student running transmission too fast or the nature of the break-in procedure (not sure because limited data)