Window motor for arm

[HarveyAce]

Would the denso window motors provided in the KoP handle the load of being the shoulder joint articulator for a four-bar gripper/lifter system? We are planning on using 1x1 aluminum box tubing for the structure, so how would we attatch the motor in the first place?

[Chris Fultz]

This will be a non-specific answer, but will get you started.

I would use both of the window motors. They are OK on power, but they have a thermal lock out (safety feature) that can cause them to stop if they get hot. You dont want that to happen in a match.

You can get an adapter and mount a sprocket to the motor, mount the motor to your "tower" system, and then mount a larger sprocket to the arm itself. Add a chain from the motor sprocket to the arm sprocket.

Use the JVN calcluator tool if you can, to get the right combination of torque and speed. The arm rotation speed will be relatively slow compared to what the motor RPM output will be so you cannot do a direct couple to the arm.

We did something similar to this is 2007. I will get a picture today and post our arrangement.

[Joe Schornak]

My team is considering using a window motor to actuate an arm mounted to a forklift-style lifter. During the course of our testing, we determined that the motor could lift a four pound weight mounted 13" from the motor axle on a simple aluminum arm. However, the motor does not actuate smoothly under this load, and rotates somewhat too quickly for fine control. We suspect that it will work better when mounted into a gearbox.

There are a number of ways to attach things to the motor, depending on how much machining you're comfortable with. You could mount a sprocket onto the plastic axle adapter thing and build a frame around the adapter to hold it all together. This method is relatively simple, but the frame might make the chain and sprocket difficult to access. It's also quite heavy, since you'll need to use a short axle with a bushing for proper support and rotation.

Alternatively, drill and tap a hole into the end of the axle, and use a bolt to hold the plastic adapter onto the motor. This is legal under <R47>A, and is much more compact than the first method. However, it requires a specific set of tools and skills, so you might want to have one of your machine shop sponsors do this for you for best effect.

As Chris said, you should consider the thermal safety lock when designing your arm. The worm gear will hold the arm at an angle without stalling the motor, but the window motors will overheat if you try to move something too heavy. My team reduced this problem by installing external cooling fans around our window motors, but they still locked up after prolonged use.

Best of luck with your robot-building!

[ajlapp]

They don't back drive very well either.

So if you end a match with your arm extended you'll have to roll it back to you pit that way...or tether up to let it down.

[HarveyAce]

I talked it over with my mentor, and we decided that it would probably be better to use the Banebots motor and put it on last years AM gearbox and use a chain and sprocket to lift. the question is, because we don't have a lot of materials and machines, how can we do that, because the Banebots output shaft is so tiny?

[Jeffy]

Originally Posted by HarveyAce

I talked it over with my mentor, and we decided that it would probably be better to use the Banebots motor and put it on last years AM gearbox and use a chain and sprocket to lift. the question is, because we don't have a lot of materials and machines, how can we do that, because the Banebots output shaft is so tiny?

one of these:http://banebots.com/p/S24K-C1-7
will interface a RS 775 motor to any of the am gearboxes that ussualy mount a CIM motor.

They are also availible for the rs550 motors

[wireties]

We are using 2 window motors and a 9:1 sprocket setup. Given the weight of our arm and gripper, the motor should ;o) operate right in its sweet spot. But it is not built quite yet - can't tell you if the calculations were correct yet.

Best of luck!

[G33k712]

If our team chooses to use the window motors, is there a belt and sprocket set that works with the little gear looking shaft on the said window motor? If so, where can I find it?

[Alan Anderson]

Originally Posted by G33k712

If our team chooses to use the window motors, is there a belt and sprocket set that works with the little gear looking shaft on the said window motor? If so, where can I find it?

At the top of page 16 of the Kit of Parts checklist is a picture of the Denso motor couplers you received. That's the only thing I know of that "works with" the motor output. You can bolt whatever you want to it.

[LLogan]

Originally Posted by Alan Anderson

At the top of page 16 of the Kit of Parts checklist is a picture of the Denso motor couplers you received. That's the only thing I know of that "works with" the motor output. You can bolt whatever you want to it.

Adding onto this, the coupler accepts a 5/8 keyed shaft very nicely. You can also drill custom holes onto the coupler to attach a sprocket. Our team also drills and taps two channels for set screws onto the part where the coupler mates with the motor output.

[Andy A.]

Originally Posted by LLogan

Adding onto this, the coupler accepts a 5/8 keyed shaft very nicely. You can also drill custom holes onto the coupler to attach a sprocket. Our team also drills and taps two channels for set screws onto the part where the coupler mates with the motor output.

To heap on some more detail, the 'output' shaft on the window motor doesn't rotate. That makes it pretty handy, as you can drill and tap it (carefully!) for a screw to retain the plastic coupler and whatever you attached to it to the motor. I think #10 thread works out pretty well.

Incidentally, that shaft is 8mm OD, which is close but not quite 5/16ths. Since it's advisable to avoid side loads on that shaft it's often the case that someone measures it with the intent of putting a bearing on it and finds out their brand new 5/16th ID bearing doesn't quite fit. Truly frustrating.

[Nemisis]

I actually designed an arm with a grabber that involves the window motor unit from the KOP. We're still tweeking and havent introduced programming to it however from small tests we've tried this seems to be a very good idea!

[yarden.saa]

My team is going to use all the window motors in the KoP for the arm.