CIM Motor Direct Drive or Supporting Axle

[loganc10]

While I have heard of FIRST Robotics and the competitions and seen designs online, I have never participated myself.

My above comment was a best guess at how I would support the otherside, however I do not believe I was very clear in describing it.

I would attach the 8mm hub to the CIM shaft, this hub would attach to the wheel previously shown. After the hub I would attach a coupler to what is remaining of the CIM shaft, allowing an additional 8mm shaft to go through the middle of the wheel to a bearing that is mounted to the frame. Maybe something like this?



Or would I be better off getting another hub and put on the other side of the wheel, which then connects the additional shaft (though not connected to the CIM shaft) to the bearing/mounting block?

Thanks for all your help, this stuff is just a little over my head. I plan to continue to do research.

Edit:

GeeTwo, thank you for a technical break down.. I kind of figured the CIM's were a tad overkill, but it was what the referenced project used with good results so I went with them. However, it is important to note that his wheels were milled from solid MDF and were pretty heavy.

Ari, I do plan on fabricated the frame myself. At my dad's work he has access to steel tubing and plate stock, figure it wouldn't be a problem for him and I to go there and throw something together. I've been looking for an excuse to learn to weld anyways.

Jman, your suggestion was what I was considering and trying to spit out. At the beginning of this post and also the prior.

I am going to continue look into possible wheels, however I'm slightly under a budget so the the possibility of lawnmower or custom plywood was taking that into consideration. However, I am still up for suggestions regarding them.

Thanks!
Logan

[MrBasse]

The CIM shaft isn't that long to begin with, it will never make it through a wheel. A hub on both sides of the wheel would be the best way to do it without some extra engineering. I would look in to a wheel with some give to absorb the ball a little and grip it well. Since you seem to have found Andymark.com, take a look at their 8" pneumatic wheel.

Alternately you could do something like this. It would give you a reduction and would allow you to use a $5-10 wheel instead of a $40 wheel. The only downside is that the bearings in those wheels are horrific at any kind of speed over a walking pace when mounted on a cart (think terrifying vibration and 2nd degree burn heat [ask me how I know about the burns]).

[akoscielski3]

As a rule: never ever side load a motor. So you should not directly drive the wheel from the CIM Motor. You should add a set of gears/belts and pulleys/sprocket and chain to each wheel

Why to not side load the motor? You will likely destroy it. The bearings will not last as long, break and then your motor will burn out. You could also bend the shaft of it or something else can happen

[Chris_Ely]

This is the shooter that my team made for the 2012 FRC game. (sorry for the big image)

The wheels are supported by one shaft, with the a belt from the motors and gearbox. You could place the motors and gearbox in between the two sets of wheels you have pictured, and use two belts; one to the upper wheel and one to the lower wheel. I would not recommend using the pneumatic wheels that were linked to above, as the valve causes the wheel to be unbalanced resulting in horrible vibration.

[jman4747]

Originally Posted by akoscielski3

As a rule: never ever side load a motor. So you should not directly drive the wheel from the CIM Motor. You should add a set of gears/belts and pulleys/sprocket and chain to each wheel

Why to not side load the motor? You will likely destroy it. The bearings will not last as long, break and then your motor will burn out. You could also bend the shaft of it or something else can happen

You are right but in 2013 we made a full court Frisbee shooter by mounting a 8mm hub to a cim and a 8" Andymark pneumatic and it survives to this day after several hours of running time since 2013 (we didn't know better). You really shouldn't do it if you can avoid it however and this is such a case.

Beware of using the pneumatic wheel at high RPM. I still remember how that max RPM warning showed up on the Andymark product page midway through the 2013 season. The primary problem was balancing it. The inlet port for air needs to be offset buy something on the other side. Also if you want to save money it's a less optimal choice. I would think andymark 6" or 8" rubber treaded wheels would do fine here and cost less.

Edit: What tools do you have access to? That can change a lot of things.

[loganc10]

Originally Posted by akoscielski3

As a rule: never ever side load a motor. So you should not directly drive the wheel from the CIM Motor. You should add a set of gears/belts and pulleys/sprocket and chain to each wheel.

Does side loading a motor mean driving the wheel directly, supported or not? I was looking to stay away from a bunch of pulleys, gears, etc. The more of those the more mechanically inclined I need to be. While I believe I could pull it off, I'm not sure I want to deal with the headache and price increase of those extra components.

What tools do you have access to? That can change a lot of things.

I have access to basic power tools. No machine shop or anything extravagant like that. I'll be utilizing my dads work for some steel stock and welding equip. for the frame. But other than that I'm not looking to do any fancy fabricating.


What are your thoughts on THESE wheels? The downside of the rubber threaded wheels on AM is that they are only an inch or so wide, potentially requiring two (side by side) to attain the required width for a tennis ball. These Vex wheels come up to 2.5", however with a lower diameter.

Can anyone comment on the bearing and housing needed on the other side of the wheel that will attach to the frame? I'm not super familiar with them, and what exactly I need. Will something like in the photo above work?

Thanks,
Logan

[philso]

Originally Posted by akoscielski3

As a rule: never ever side load a motor. So you should not directly drive the wheel from the CIM Motor. You should add a set of gears/belts and pulleys/sprocket and chain to each wheel

Why to not side load the motor? You will likely destroy it. The bearings will not last as long, break and then your motor will burn out. You could also bend the shaft of it or something else can happen

In 2013, some of our team members made prototype frisbee shooter with the wheel driven directly off the motor shaft. After several shots where the compression (= side load) was set too high, the motor bearing at the back end failed.

[asid61]

You could use that, or just drill a hole in the side and stick a ball bearing in with some locktite. That might be cheaper, although using what you show above might work too.
I would also recommend making everything out of wood instead of metal, as it is cheaper and easier to work with.

[jman4747]

You will sacrifice speed with smaller diameter wheels and they don't have to be as wide as the ball. The ball just needs to hit the center of the wheel. Two side by side would give better accuracy but this application doesn't require it so a physical constant that keeps the ball mostly centered as it hits the wheel would be enough.

My suggestion would be to mount the 8mm hub to this wheel and on the other side use a 3/8" hub with this bearing at the end of the shaft.

If I were designing an FRC robot this assembly would be totally different but this application should't require it.