8" Pnumatic Wheels @ Andymark soldout

[MrBasse]

Originally Posted by philso

The steel hubs on the wheels from Harbor Freight are pretty heavy and are probably hard to use with the hubs and shafts we are all accustomed to using. Currently, AndyMark has the 8" plastic hubs in stock. You may want to verify that the tires from the Harbor Freight wheels will fit the AndyMark hubs.

They don't fit. Harbor freight sells mostly 10" tires but they do have an 8 inch non marring tire that is red in color. However, the andymark tire isn't really 8 inches as it is a metric tire. The HF tire is a 4x2 hub, so a totally different standard of measurement.

In the past we mounted hubs and sprockets to the steel wheels, but they are heavy heavy heavy. We are currently printing hubs for our 8" non-marring tires and tubes.

[philso]

Originally Posted by MrBasse

They don't fit. Harbor freight sells mostly 10" tires but they do have an 8 inch non marring tire that is red in color. However, the andymark tire isn't really 8 inches as it is a metric tire. The HF tire is a 4x2 hub, so a totally different standard of measurement.

In the past we mounted hubs and sprockets to the steel wheels, but they are heavy heavy heavy. We are currently printing hubs for our 8" non-marring tires and tubes.

Well, the hubs for the 8 inch wheels are out of stock at AndyMark making this moot now.

I did pick up one of the red wheels from HF the other day and had a student take it apart yesterday. We also found one half of one of the AndyMark hubs and tried to fit in the red tire. It looks a bit small, probably due to it being made to a similar but different sizing standard so it is not clear if the AndyMark hubs would grip the tires properly. The red HF tire is also a bit wider (along the axis of the axle) so people who use it should beware if they are using the AndyMark wheel in their CAD. We are looking at alternatives now. Please let us know how the printed hubs work out for you, especially how they take abuse.

I know AndyMark running out of these wheels is a great inconvenience to many teams but I feel that if FRC is to be an introduction to the world of engineering, this supply issue is not a bad thing at all. A significant portion of my work supporting existing products in my day job consists of finding alternatives for components that we are having a hard time getting enough of or the supplier cannot deliver on time or the component has gone obsolete. Not finding a replacement part usually means that the production line stops and the money stops coming in.

[MrBasse]

You might be able to get away with adding airing up the tire a lot to increase the grip on the hub, but I would have concentricity concerns using the AM hub on the Harbor Freight red tire. We're 3d printing hubs, but I wouldn't have huge concerns with wrapping the hubs in something to make it a bigger diameter (duct tape?). Due to the nature of how those wheels and tires work, the tube should help to center it a little. I would still have concerns about large impacts due to the smaller bead retainer in the bigger tire.

[BBray_T1296]

I took the CAD of the hub off of Andymark and modified it to be a bit more 3D printer friendly.
If anyone is feeling brave enough to try running a printed hub, I posted it to Thingiverse.

It should fit any 200x50mm tire and inner tube which can be found all over the place.

[MrBasse]

Originally Posted by BBray_T1296

I took the CAD of the hub off of Andymark and modified it to be a bit more 3D printer friendly.
If anyone is feeling brave enough to try running a printed hub, I posted it to Thingiverse.

It should fit any 200x50mm tire and inner tube which can be found all over the place.

Be sure that the outer diameter is thick enough, I had trouble with it not having the thickness to get three full layers in so I ended up with two layers and a hollow gap between them.

Did you remove all of the fillets? Doing that cut supports in half after I took the draft off and made my own spokes so it would be prettier.

[BBray_T1296]

Originally Posted by MrBasse

Be sure that the outer diameter is thick enough, I had trouble with it not having the thickness to get three full layers in so I ended up with two layers and a hollow gap between them.

Did you remove all of the fillets? Doing that cut supports in half after I took the draft off and made my own spokes so it would be prettier.

What diameter nozzle are you using? I have not printed it myself but Repetier says it can get 7 shells of thickness on the outer edge using a 0.4mm nozzle.

I removed the indexing holes that align the two halves so the part can lie flat on the bed. I also chamfered the outer lips (that retain the tire). Otherwise I made no visual changes.

I am not sure how removing the fillets would change anything. Do you mean the on the outside (where the inner tube would rest against)? If so, I did reduce those to being a 50deg overhang which my printer has no trouble doing without support. The outer rim that holds the tire on is the real concern with support for me.

EDIT:
I think I understand what you meant. I was intending for the one I made to be printed upside down compared to the way I believe you were printing it. Reason I chose the way I did was so that the hex pattern would come out right but to each their own.

[PowerfulKitty]

IMO the pneumatic tires are not any better than solid ones.

[Dave McLaughlin]

Originally Posted by PowerfulKitty

IMO the pneumatic tires are not any better than solid ones.

That's fantastic! Perhaps you could provide some insight as to why instead of just making an empty statement?

[BBray_T1296]

Originally Posted by PowerfulKitty

IMO the pneumatic tires are not any better than solid ones.

There is a reason that every car on the road has air* filled tires, and it is not for better traction.

*or nitrogen

[MrForbes]

gwiw, the steel hub and 10" tire on it, from Harbor Freight, weigh 3 lbs. each.

[MrBasse]

Originally Posted by BBray_T1296

What diameter nozzle are you using?

I am not sure how removing the fillets would change anything. Do you mean the on the outside (where the inner tube would rest against)? If so, I did reduce those to being a 50deg overhang which my printer has no trouble doing without support. The outer rim that holds the tire on is the real concern with support for me.

EDIT:
I think I understand what you meant. I was intending for the one I made to be printed upside down compared to the way I believe you were printing it. Reason I chose the way I did was so that the hex pattern would come out right but to each their own.

I'm printing on a Stratasys machine with soluble support.
As I don't have the freedom you do to change parts, I'm stuck at a .010" nozzle. Also, the radii in the fillets required support material to print, thus the savings in material. I always forget that not all printers work like that...

However, I did start printing 8 sets of hubs yesterday and then left school. Went back to check on them today and I only have until 10:00 and they'll be done. The saving grace of an expensive machine like a Stratasys is that it is like an appliance rather than a hobby printer. The ability to print overnight without having to babysit sure is nice when you print a 33 hour long print job...

[s_forbes]

I'm hoping that these wheels end up back in stock within a couple of weeks, since we still need to order another set. I saw the new tires (other brands) pop up on andymark and thought we could try them, but they're all sold out already as well.

Goodness, these things sure are fun to play with though.

[PowerfulKitty]

Originally Posted by Dave McLaughlin

That's fantastic! Perhaps you could provide some insight as to why instead of just making an empty statement?

I would not try to suggest that the pneumatic wheels are worse than solid ones, simply that they are not better. I was actually hoping someone would explain to me why everyone seems so convinced that pneumatic wheels are necessary for this game. I do not understand why so many people are going out of their way to try to find ways to get these wheels.

[MrForbes]

The wheels are just awesome!

[Monochron]

Originally Posted by PowerfulKitty

I would not try to suggest that the pneumatic wheels are worse than solid ones, simply that they are not better.

If you'll check what he posted again, you'll see that he was not asking about the intensity of your dislike for pneumatic wheels, but why you dislike them. For instance, what do they fail to beat solid tires at? Efficient running? Ease of use? Shock absorption? Traction?
There are many aspects to what makes a tire "good" for a certain application, and I believe Dave was trying to get you to dig into that and see what your opinion is based on.