Where to find wheels of the right size

DavidZemon

I'm trying to find two wheels that will fit a motor with the following dimensions:

Shaft is a D shaft
D shaft is 8mm diameter with the cutout being 7mm wide
The cutout runs 12mm down the length of the shaft
The shaft protrudes 19mm from the base of the motor

I'd like something on the order of 100mm or 4" in diameter, but I'm not real picky (nor do I have any idea what would be the "right" size for my application). The motors are 12V, 3.5A/5A+ geared for 1:131 and I'll be using them to power a balancing robot. The chassis for the robot isn't built yet (and I'd like to have the wheels in my hands before next weekend when I build the chassis), but I'm looking at between 18-24" tall made of steel. battery pack will be 8 AAs. I'm not really sure what that will mean in terms of weight, but I would bet anything on the order of 4" in diameter with an 8mm shaft will not have any problems supporting the weight.

Heater.

You mean like these:

http://shop.eaglecreek.com/70-mm-wheel-set-w-8mm-bearings/d/1192

Just gum up the bearings with some suitable glue and stick then on your shaft with loctite or some such.

Or perhaps http://www.ebay.co.uk/itm/300397444752 bit pricey.

DavidZemon

The first link is a good price at least, though significantly smaller than what I'd like. The second link would double the price of this project.

DavidZemon

Well, I'm downloading Cura 2.6 right now... going to try and build a really simple 3D model of a solid wheel with the right axle dimensions. I can wrap it in rubber bands for tread. I've never looked at the cost of 3D printing at my local Maker shed before, but I'll bet even a solid wheel will cost less than the $10-$20 I'd have to shell out for something online (not even including shipping in that).

erco

Head to harbor freight, some of their cheap dolly wheels roll on a small axle, no bearing.

Google 4" plastic wheel, lots of hits.

Here's a $1.71 plastic 5" wheel with rubber tread: https://hardwareonlinestore.com/index.php?option=com_virtuemart&view=productdetails&virtuemart_product_id=65077&virtuemart_category_id=67702&gclid=Cj0KCQjwn6DMBRC0ARIsAHZtCeMDL9AiULHtsgEyw2iMcwNzEHvqeV7DWuVlti984Mt5VCULT_-a6JUaAi0EEALw_wcB&ppcsclkid=IY7ThV0jCWcb&ppcstrkid=1332290283&ppcsu=xhg7f5djqitnahs

rosco_pc

I would look for hex connectors then you can use 1/10 rc wheels. Like these: https://www.banggood.com/3mm-4mm-5mm-6mm-7mm-Hexagonal-Copper-Coupling-Coupler-for-Robot-Car-Wheel-p-1171587.html?rmmds=detail-left-hotproducts


Edit add ebay link: http://www.ebay.com/itm/RC-1-10-8MM-Brass-Shaft-Couplings-Coupler-Motor-12MM-Hex-connector-DIY-Screws-/322639462176?hash=item4b1ecf7f20:g:6C8AAOSwdU1W~MkD

DavidZemon

Thank you guys! I'll keep this thread handy for the long run. Turns out my friend offered to design and print me some wheels, so my (short term) problem is solved!

DavidZemon

I was just reading the docs on my motor controller and noticed these on Pololu's website. Looks like that is the real solution to motor shafts that have large or odd dimensions like mine. A little "universal adapter" that mounts to any shaft with an 8mm diameter and then uses a screw to secure itself. Then it has lots of holes to mount to whatever kind of wheel you can imagine.

erco

Of course then the onus is on you to fasten it perfectly concentric!

DavidZemon

erco wrote: »

Of course then the onus is on you to fasten it perfectly concentric!

Oh yea.... I guess there is that.... how bad could it be!?!?

erco

If your wheels end up eccentric, your bot will waddle like a duck. Own it, tell 'em you meant to do that!

DavidZemon

erco wrote: »

If your wheels end up eccentric, your bot will waddle like a duck. Own it, tell 'em you meant to do that!

Perhaps eccentric wheels would be a good test for a balancing robot!

erco

Two things about wheels I've learned from my meager experiments with balancing robots:

1) The wheels' mass and moment of inertia (flywheel effect) will affect your tuning. I initially presumed that lightweight disk wheels would be superior, but that's not necessarily the case. In fact, if you want your bot to self-right, your wheels need some weight, and you need fast motors.

2) Soft tires (like pneumatic) add damping which adds stability and makes tuning the controller easier. Similarly, operating on thick carpet adds stability.