Window Motor question

[kevin.li.rit]

Question, How long before it randomly stops? If it is not too often, could you possibly cool the motor with the muffin fans?

[Grim Tuesday]

We are able to go up and down twice before it stops.

I wonder if the fans would do enough?

It's unlikely that we would ever be jumping around like that at competition, but you never know. Maybe with two motors, and a fan, it would be better.

[Ether]

Originally Posted by Grim Tuesday

the motor is only drawing 10 amps at stall, which is is a bit weird

Oh, and measure the voltage at the motor terminals when it is drawing the 10 amps.

[ipburbank]

So another thing (I'm also on this team). The arm works fine for a few times, but after some amount of time it stops once an extra load is added (the second stage starts lifting too). The normal raising runs at 7-8 amps, and the stall is 10-11. This makes me think heat. I wonder if this has nothing to do with the load, and more with the duty cycle. The jump in the load only after a few runs makes me think that it is heat and doesn't have to do with the added weight. Is this the case, or could there be another factor I'm missing?

[kevin.li.rit]

Originally Posted by ipburbank

So another thing (I'm also on this team). The arm works fine for a few times, but after some amount of time it stops once an extra load is added (the second stage starts lifting too). The normal raising runs at 7-8 amps, and the stall is 10-11. This makes me think heat. Is there any part of the motor that would react to heat, or cause the stall to lower while the motor is warm (not the internal sensor, possibly resistance increases?)

The motor has a PTC the stops the motor when it gets too hot.

Running a drum off the motor will cause a higher torque needed to move the load as the drum gets larger.

I think a second motor and some fans might get you by the match. If you are drawing 10-12 amps a second motor would drop you near or below peak efficiency for each individual motors. Coupled by fan or two and you may find that it runs well.

[ipburbank]

Sorry for the poor wording of that question the first time, What I mean to ask is: a second motor wouldn't decrease the duty cycle, and I wonder if the difference in load would be enough to decrease the heat generated. From previous discussion the 7-8 amps isn't an enormous load indication, therefore even half that with the long duty cycles might not make much of a difference?

[Mr. B]

The torque is the force x distance So 8 lb x 6 inches = 48 inlb
If you take the Banebots 550 motor and look to adapt it to the window motor gearbox I think you will solve your problem. FIRST take the window motor off--by removing 3 screws. On the end of the window motor is a plastic driver--slowly remove it.Look at the window motor shaft, there is 2 flats back to back.
Now take the 550 motor and mask/tape up all the openings. With a belt sander carefully sand the 550 shaft to match the window motor shaft. Note you will have to shorten the shaft slightly. Next make an adapter plate out of 1/8 alum bar stk. The banebots will bolt to the adapter plate and then bolt the adapter plate to the window motor gearbox. Worth a try?

[kevin.li.rit]

Originally Posted by ipburbank

Sorry for the poor wording of that question the first time, What I mean to ask is: a second motor wouldn't decrease the duty cycle, and I wonder if the difference in load would be enough to decrease the heat generated. From previous discussion the 7-8 amps isn't an enormous load indication, therefore even half that with the long duty cycles might not make much of a difference?

The heat generated in total would be cut down as you are running the motors more efficiently. With two motors ( and based on your current measurements) you'd be running a at close to 80% efficiency, with a single motor you'd be running closer to 60% efficiency. You'd also have twice the surface area to dissipate less than half the excess heat.

I don't have too much experience running these window motors to know under what loads the PTC likes to trip.

Edit: I've been reading the RPMs as %efficiency... so my figures for efficiency are off...

[Grim Tuesday]

Originally Posted by Mr. B

The torque is the force x distance So 8 lb x 6 inches = 48 inlb
If you take the Banebots 550 motor and look to adapt it to the window motor gearbox I think you will solve your problem. FIRST take the window motor off--by removing 3 screws. On the end of the window motor is a plastic driver--slowly remove it.Look at the window motor shaft, there is 2 flats back to back.
Now take the 550 motor and mask/tape up all the openings. With a belt sander carefully sand the 550 shaft to match the window motor shaft. Note you will have to shorten the shaft slightly. Next make an adapter plate out of 1/8 alum bar stk. The banebots will bolt to the adapter plate and then bolt the adapter plate to the window motor gearbox. Worth a try?

I wonder if that counts as modifying the window motor, and is therefore against the rules?

[kevin.li.rit]

Originally Posted by Grim Tuesday

I wonder if that counts as modifying the window motor, and is therefore against the rules?

I think that depends if there is a vendor for those window motors. If there is you can make modifications to the gearbox of the window motor. Otherwise...

[Grim Tuesday]

They are from Denso, and are OEM, and you cant get any availible. So I guess not?

[Ether]

Originally Posted by StevenB

In short, if you're pulling 10 amps, you're running at about 20% efficiency (based on the motor curves),

Since it's stalled it would be running at exactly 0% efficiency.

[ipburbank]

Originally Posted by Coffeeism

The heat generated in total would be cut down as you are running the motors more efficiently. With two motors ( and based on your current measurements) you'd be running a at close to 80% efficiency, with a single motor you'd be running closer to 60% efficiency. You'd also have twice the surface area to dissipate less than half the excess heat.

I don't have too much experience running these window motors to know under what loads the PTC likes to trip.

I don't understand how this works, but a 20% increase in efficiency, what does that gain us in terms of performance? Say now we can raise it twice, and it fails half way up the third time. Would this give us a real boost in a match? Would it complete a third trip up? Four?

[kevin.li.rit]

Originally Posted by ipburbank

I don't understand how this works, but a 20% increase in efficiency, what does that gain us in terms of performance? Say now we can raise it twice, and it fails half way up the third time. Would this give us a real boost in a match? Would it complete a third trip up? Four?

I apologize, but I was reading the RPMS as the efficiency...

But this would definitely give you a boost. It should keep the PTC from tripping as often as it does now. By adding a second motor it should at least operate twice as long before the PTCs trip. Instead of 12 amps across 1 motor, you'd have 12 amps total across two motors or 6 amps each.

However, I would expect even better, you will dissipate the same amount of heat faster with twice the surface area.

Perhaps someone who has used these motors can comment on where the Denso window motor can operate continuously?

[ipburbank]

Ah, explains some of my confusion

Anyhow, if one motor is slightly faster than another, does that nullify a large portion of the problems, or even make them worse for the faster motor?