pic: How 125 is rolling this year...

[Brandon Holley]

loading photo ...

[,4lex S.]

How are they holding up from an elasticity standpoint (meaning, do they deform under the weight of a robot by much?). They look awesome; however, if you could embed LEDs... (not so sure on how the rules would like that, but it would look cool)

[coldfusion1279]

Urethane is very stiff, and since those wheels look relatively solid, I wouldn't think there would be any deformation at all.

That is a really cool project, something that most, if not all, teams could do feasibly in a short period of time. Thanks for the post.

[Akash Rastogi]

How many of these can we expect at our doorstep on Monday?

You'd think 125 would go with red wheels though.

[Brandon Holley]

Originally Posted by coldfusion1279

Urethane is very stiff, and since those wheels look relatively solid, I wouldn't think there would be any deformation at all.

That is a really cool project, something that most, if not all, teams could do feasibly in a short period of time. Thanks for the post.

You got it right. This stuff is something like an 85 or a 90 on the Shore D scale, which is very rigid. The fiberglass adds some extra rigidity.

EVERY SINGLE TEAM IN FIRST can do this. For teams that like to use the same type of wheel from year to year this may be something to consider. If you invested in a multi cavity mold, a team could feasibly have all of their wheels for the season in a couple of hours.

Originally Posted by Akash Rastogi

How many of these can we expect at our doorstep on Monday?

You'd think 125 would go with red wheels though.

Haha, these are 4 inchers, so I don't think they'd fit what you guys are using. Someone accidentally threw out the red dye :-/. We plan on using some withholding allowance to make some red ones. Oh by the way each one weighs less than 3 ounces.

-Brando

[Akash Rastogi]

Hahaha man I knew I had seen a similar wheel before.

http://lh5.ggpht.com/_yaSezzGIV6Y/Si...ke%204inch.jpg

Really look forward to seeing these in person in a few weeks.

[V_Chip]

Less than 3 ounces?

Great idea. Kudos

[Brandon Holley]

A few hours worth of work this weekend.

-Brando

[sdcantrell56]

How durable is the urethane specifically in impact? Also was the bolt pattern molded in or was that machined separately?

[Bruceb]

Where do you get the materials? The silicone and the urethane? What do they cost? Do you cast the wheels with the bearings in the mold or do you machine the wheels later and install them?
Thanks
Bruce

[Brandon Holley]

Originally Posted by sdcantrell56

How durable is the urethane specifically in impact? Also was the bolt pattern molded in or was that machined separately?

During some pseudo-tests the wheels have performed well. One wheel was able to support 165 pounds of weight bouncing on it (me bouncing up and down). This was in the vertical (weaker) orientation. We'll be doing more testing this week. The thing the wheels have going for them is the tread will buffer some of the blunt impact force.

The hole pattern on the old wheel we used had clay partially filled in the bolt holes. This allowed for us to essentially have pilot holes that were drilled through on the drill press.

Originally Posted by Bruceb

Where do you get the materials? The silicone and the urethane? What do they cost? Do you cast the wheels with the bearings in the mold or do you machine the wheels later and install them?
Thanks
Bruce

There is a store in Boston that sells www.smoothon.com products. However, you can purchase these online and have them delivered to your shop. To make the wheels you see here it cost us 45 dollars. Silicone is capable of holding a remarkably tight tolerance when using it to create molds. We were able to use the hole in the old wheel which was designed for a press fit (~.874") as is. The bearings were then pressed into the new wheels...simple as that.

-Brando

[Andy Bradley]

Those wheels look sweet, and would be a great off-season project. I looked at the smooth-on site that you mentioned, and found a wide variety of products. Can you tell me exactly which silicone (for the mold) and which urethane (for the wheel) you used? Is it the smooth-cast 305 plastic in the 00M00 30 silicone rubber as shown in their video? Also, what type of fiberglass did you add? Thanks in advance.

[Jamie Kalb]

Hey Brandon,

How were these wheels in retrospect? Are there any changes you wish you had made, or did they perform pretty much the way you wanted? This is such a neat concept!

[Brandon Holley]

Originally Posted by Andy Bradley

Those wheels look sweet, and would be a great off-season project. I looked at the smooth-on site that you mentioned, and found a wide variety of products. Can you tell me exactly which silicone (for the mold) and which urethane (for the wheel) you used? Is it the smooth-cast 305 plastic in the 00M00 30 silicone rubber as shown in their video? Also, what type of fiberglass did you add? Thanks in advance.

The mold was made from Mold Max 30. That is the "multipurpose" silicone, that can be used for pretty much anything. I've used other varieties, but the Mold Max 30 is just awesome stuff and super simple to use. The wheel was made from task 9 urethane. I've had less experience using the rigid urethanes, like the task series, but from my experiences with it in these wheels, it is also very good stuff.

The fiberglass we used was just simple fiberglass cloth you would buy from home depot/lowe's and then chopped via scissors into ~1/2" long strands and added to the urethane.

Originally Posted by Jamie Kalb

Hey Brandon,

How were these wheels in retrospect? Are there any changes you wish you had made, or did they perform pretty much the way you wanted? This is such a neat concept!

These wheels show a lot of promise in regards to FIRST robots. There are some definite changes I would make to the wheels in regards to geometry, but thats about it. What we are going to do over the summer is machine a block of wax into a wheel with more ideal geometry. We are then going to use that wax wheel to create a new mold. We want to produce some of those wheels from the mold and put them through some tests. If they perform like we expect they will, we want to make a multi-cavity mold. This will allow us to pop out 2-4 wheels at a time and essentially make wheels a standard item for us to design around.

Let me know if you have any more questions.


-Brando

[Bruceb]

Has anyone else tried this? Any success? Brando, what mods did you come up with for this wheel? Can I get a picture of the actual mold? I don't quite get how you get the entire wheel molded on all sides without any machining.
Thanks
Bruce