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2014-05-31 - Tennis Ball Machine - Wheel Attempt 1

This is a bit out of date but this was the first attempt at the wheel rigged up for testing. The idea was to have something sufficiently heavy spun by the high speed electric motors.

Parts-wise, we have something like the following in the picture:

The tricky part ended up being how to get from the motor out to the caster wheel. Not being a mechanical engineer, this was just a bit of an adventure. Along the way, I tinkered a bit with 3D printing but unfortunately the ND 3D printer stopped working near the end. The end result was sort of a hodge podge of parts from Actobotics (bought from Sparkfun, love you guys though my credit card does not).

There were basically two problems: (1) Getting from the motor shaft to some sort of an axle and (2) Connecting the axle to the caster wheel. The rest was not too bad.

The first part seemed to have a fairly wide selection of parts and I ended up focusing on the second part, worried a bit about how to connect the 1/2 aluminum pipe to the caster wheel itself. At the time, I was trying to avoid using the custom Acotbotics wheels (though I have gone back to them for round 2). I ended settling on one of the 0.77 to 1.5 adapter plates, driving screws through the 1.5 unthreaded holes into the polyethylene of caster wheel, reasonably aligned by a shaft through the 1/2 (approximately) inner bearing on the wheel. The result was predictably a bit less than stellar. From the inside of the small pocket by the caster wheel, I took out 6-32 threaded screws into a 0.5" clamp that was then clamped onto the 1/2 shaft. This seemed to work a bit better though and seemed to be quite sturdy for keeping the caster wheel on the "axle" of the 0.5 aluminum tube.

With that part down, the next step was getting out from the motor. Seeing as how the BaneBots motor was not one of the kit motors, there were a slew of mounts. After trying three or four, I ended up going with the Actobotics one which was a bit more expensive but spot on. Now that the motor itself could be pinned down, on to transferring the power out from the motor. The guidelines on how to do this are how shall we say, just a wee bit on the unhelpful side. With a slew of axle / shaft adapters in, I whipped through a bunch. The most promising one seemed to go from the motor directly into an aluminum shaft. Bummer was that was a non-starter due to incompatible alignment holes. This is where the 3D printed part would have been excellent but alas, no luck. From there, it was on to clamps where a similar 0.5 clamp (two screw, not the single screw clamp) could adapt. A bit of masking tape to prevent slipping inside the clamp and the motor was on. Add a 0.5 pillow block or two and you see the result attached to MDF.

IMG_7765.JPG IMG_7766.JPG IMG_7767.JPG IMG_7768.JPG IMG_7769.JPG IMG_7770.JPG

The side holes are for mounting to a punched angle steel that I picked up at Home Depot (link coming). Ignore the awful interior cuts for the wheel.

The power itself is controlled by a relatively inexpensive PWM module (roughly $30 from BatterySpace). I ended up going with a 12V battery for around $20 from the same vendor (SLA).

A few thoughts from the operation and the first setup:

* The wheel is definitely heavy enough. It keeps spinning for a really, really long time. * The motor is definitely fast and powerful enough. Unconnected, it will easily flip when not attached to anything (full 12V because hey, gotta test it, right). * Probably too much vibration on this design. The pillow block alignment was not perfect and would need to be redone. * Next time, search better on Google. I ended up getting the original motor via eBay for $30 for both but could have gotten them for $6 each from RobotShop.

For round two, I will be switching over to an different frame and a direct drive to the wheel using a pair of Actobotics wheels. Should be exciting to compare the two.

May 31, 2014 - created by Aaron Striegel_

Topic attachments
I Attachment History Action Size Date Who Comment
JPEGJPG IMG_7765.JPG r1 manage 402.7 K 2014-05-31 - 17:36 AaronStriegel  
JPEGJPG IMG_7766.JPG r1 manage 377.2 K 2014-05-31 - 17:36 AaronStriegel  
JPEGJPG IMG_7767.JPG r1 manage 379.8 K 2014-05-31 - 17:36 AaronStriegel  
JPEGJPG IMG_7768.JPG r1 manage 369.2 K 2014-05-31 - 17:36 AaronStriegel  
JPEGJPG IMG_7769.JPG r1 manage 377.7 K 2014-05-31 - 17:36 AaronStriegel  
JPEGJPG IMG_7770.JPG r1 manage 473.9 K 2014-05-31 - 17:36 AaronStriegel  
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Topic revision: r1 - 2014-05-31 - AaronStriegel
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