Attaching sprocket to a pneumatic wheel?

[ksafin]

Hey all,

We're thinking of getting this wheel for our robot, and were wondering how we would go about attaching bearings/sprocket or whatever else we need to get this going on our robot.

Thanks!

[I LOVE ROBOTS!]

perhaps machine a hub that utilizes that 4 bolt bolt pattern, or possibly put that pattern on your sprockets and use some standoffs. and it looks like it already has bearings. the only other ideas that come to my head this late at night would be a nightmare so I'll just leave them in my head

[Mk.32]

Also know that wheel is quite heavy....

But your best bet is probably using stand offs and getting longer bolts.

[mrnoble]

We recommend milling your own hub for these wheels. Nothing from Andymark can be made to fit them.

[MrBasse]

We are using the same wheel. Saying that nothing from andymark will fit is incorrect. The kop 26 tooth sprocket has an id that fits over the hub, however it is a little oversize. We used a plasma cutter to cut some flanges that we are welding to the end of the extended hub. We will then mount the stock andymark sprocket to that new flange. Those wheels are more than robust enough to hold up too, our lead mentor used them for a go kart for his kids and they ran it with a gas engine and two kids rising it for a whole summer before it broke. As with any plan, always make spares...

[mrnoble]

I misspoke; what I should have said was, we didn't find any hubs from andymark that we could modify to attach any better than hubs that we make ourselves. The wheels are heavy, but are super cheap right now, at $3.49 each. We are going to try them out this week and see if they are "worth the weight" for getting over the bump. best of luck!

[Akash Rastogi]

I would honestly recommend this instead http://www.andymark.com/product-p/am-0970.htm

[Joe Johnson]

Originally Posted by Akash Rastogi

I would honestly recommend this instead http://www.andymark.com/product-p/am-0970.htm

Seconded.

[MrBasse]

The only issue with an 8" wheel compared to a 10" wheel is the extra force needed to climb the obstacle. An 8" wheel means you are hitting the barrier with the wheel climbing vertically due to the center of the wheel being at or slightly below the barrier's total height. The modifications necessary to make a 10" $4 wheel work took us the better part of one afternoon to complete and with a little help from local welders we can have a very simple and cheap means of handling anything that the field can throw at us.

Also, our team has a very limited budget, as I'm sure others do as well. Spending $15 per wheel is much easier to swallow with a little work than spending $60+ for one that is just a bolt on. When you look at six wheels, we save $270... that's more than we spent on all of the parts we put on our rookie year robot...

[Akash Rastogi]

Originally Posted by MrBasse

The modifications necessary to make a 10" $4 wheel work took us the better part of one afternoon to complete and with a little help from local welders we can have a very simple and cheap means of handling anything that the field can throw at us.

Do you have pictures of your modifications?

[MrBasse]

They are being welded over the weekend and we will get some up when we return to school on Tuesday. I am working on getting my students up to speed with a CAD file as well, but we only have 14 kids and only two of them have interest in CAD.

Basically picture a cheap ten inch tire like this one

the other side of the hub has a extension that spaces out the pressed in bearings. We cut a 3/16" thick ring using our CNC plasma cutter that is being welded flush with the end of that hub extension. We will drill the proper holes and bolt the andymark sprockets from the kop to that ring.

A lot of posts have come up recently about these wheels and using spacers to make use of the 4 bolts that hold the hubs together. We looked at that option but didn't like the size required and cost associated with using a sprocket that would fit around those four holes. Here is a really bad representation that I just threw together in Inventor

[Chris Fultz]

Another factor to consider is the weight impact.

The Harbor Freight wheel is 3.9 lbs. The AM wheel is 1.1.
With a 4WD this is 16 pounds compared to 5.
With a 6 WD is is 24 compared to 7.

There are many factors to consider, weight should be included.

If your are able to make the HF wheel work and manage the weight, that is cool. There is always a tradeoff of weight, cost, availability and capability.

[Mk.32]

Also look at the skywaywheels for cheap and relative light tires.
They have a 10x3 inch pneumatic wheel.
http://www.skywaywheels.com/usfirst.htm just give them a call and they will send over any info you need.

[mrnoble]

you're all going to react in horror, but we made our hubs out of quartersawn white oak, turned on the lathe and broached for the hex axle using chisels. Most of our bots for the last several years have been made of wood to some degree or other, as woodworking is the program our robotics team grew out of. We've had great results (by our standards), because wood is tough, durable, and easy to manufacture. So far they look like they will hold up well, but as has been said already, the weight may make us change our minds later. We'll see!

[JohnBoucher]

BAM Team 237 also used Skyway wheels.


BAM = Before AndyMark