Battlebots

A new forum for battlebots enthusiasts, competitors, and fans.
 
HomeCalendarFAQUsergroupsRegisterLog inBuilders DB

Share | 
 

 casting rubber wheels

View previous topic View next topic Go down 
AuthorMessage
colin



People Skills : 3051
Registration date : 2009-07-14

PostSubject: casting rubber wheels   Mon Jul 20, 2009 4:23 pm

I know it's not very common, but some teams have done it before. does anyone know what casting compounds/thermoplastic elastomers are available? not many places will sell you the compounds - most want you to buy a product made by them, so they can make more money off of you. I've casted silicone before, but don't think it'd be a good choice for wheels - too soft and brittle. I've seen a few products here and there, but right now I don't see a better option than just trying to melt down and recast colson's. has anyone seen a better option?
Back to top Go down
rdubard
mega contributor
mega contributor


People Skills : 3582
Registration date : 2009-06-10
Age : 52
Location : Ransom Everglades, Miami, FL

PostSubject: Re: casting rubber wheels   Tue Jul 21, 2009 10:42 am

I confess to total ignorance on this. . .and I mean total, because I cannot think of a good reason why you wouldn't simply buy the wheels you need.

Not to hijack the thread, but what sorts of wheel materials are considered best by our forum members in general?

I have lately been really interested in skateboard/scooter wheel material (polyurethane) for a 120lb, under the assumption that, if it's durable enough to support a person under rough conditions, it's probably great for battlebot wheels too. A quick google search returned this discussion of types, sources, and methods. It specifically mentioned BASF as a source for raw material--it might be worth a try.
Back to top Go down
colin



People Skills : 3051
Registration date : 2009-07-14

PostSubject: Re: casting rubber wheels   Tue Jul 21, 2009 11:25 am

it seems like the most popular wheels are colson performa's, or anything with around a 65 shore A hardness.

skateboard wheels wouldn't work for battlebots - they're meant to run on a really rough surface (asphalt) so the wheel material is hard. on a smoother surface (painted steel, other arenas) you need softer rubber to get the same coefficient of friction. those wheels would slip way too much.

finding the right material isn't easy, because it needs to be soft enough to grip well, but not soft enough to tear off the hub or wear too quickly, and you have to make sure it won't become brittle over time.
Back to top Go down
Cody
2000+ club
2000+ club
avatar

People Skills : 5764
Registration date : 2009-03-16

PostSubject: Re: casting rubber wheels   Tue Jul 21, 2009 1:19 pm

That is true for outdoor roller wheels, but what about an indoor wheel? They have different softness ratings. Indoor wheels are rated around 74A, theyre much softer to grip the hard slick sythetic roller surface. Trust me ive played games with outdoor wheels and indoor wheels and there is huge difference
http://www.hockeygiant.com/milinhocwhee.htmlgreat extra soft wheel
Back to top Go down
Dan Curhan
Admin
avatar

People Skills : 4012
Registration date : 2009-03-14
Age : 26
Location : Sarasota, FL

PostSubject: Re: casting rubber wheels   Tue Jul 21, 2009 7:06 pm

Copperhead pi had custom polyurethane wheels... they held up incredibly well. That stuff is amazing.

We had a company called Sunray, inc (in Rutherfordton, NC) bond the polyurethane (95A durometer) to the outside of an aluminum hoop. Then we had another company machine wheels for us. We sent them CAD files for wheels made up of two halves that pinch together on the aluminum base of the tire. I do agree with the harder durometer - higher slip statement. These 95A tires slipped a little on the arena floor...

_________________
If you like HEAVY METAL, check out my band.
Or my my other band.

-Captain of Copperheads 2 to pi, mastermind of the Dethinator, Creator of Conundrum, and Sultan of Shred. Heh. Sultan of Shred. It's kinda catchy... I like it!
Back to top Go down
http://666bots.blogspot.com/
rdubard
mega contributor
mega contributor


People Skills : 3582
Registration date : 2009-06-10
Age : 52
Location : Ransom Everglades, Miami, FL

PostSubject: Re: casting rubber wheels   Wed Jul 22, 2009 1:39 pm

Cool to hear that polyurethane not only works, but has real, high quality 'experience!' I thought there might be different grades/shores, and apparently there are differences in durability based on cast vs molded (now what's the difference between a casting and using a mold? Smile ). This does seem like a topic worth investigating.

But back to the original thread--seriously, why do you want custom wheels? Wouldn't you prefer an off-the-shelf item that's not only cheap, but quick to replace? It seems to me that something suitable must already be in production somewhere. (I'm not trying to be contrary, I promise--I'm sure you have good reasons, I just am not clever enough to think of them myself)
Back to top Go down
colin



People Skills : 3051
Registration date : 2009-07-14

PostSubject: Re: casting rubber wheels   Wed Jul 22, 2009 2:17 pm

Cody - I suppose indoor wheels are around the right hardness. they still don't seem to be a great choice, though. skateboard/longboard wheels are made to roll, not be driven. they take two bearings (of a rather large diameter) with a spacer in between. there's not much material to grab on to, and they aren't a constant bore, so it'd be a pain to machine a hub or make a keyway - and tricky to do it without wasting a lot of weight in metal. they are also wider than you need for a battlebot. it would probably be better to go with another wheel.

Dan - thanks, sunray looks like they make good products. still, I'd rather be able to cast my own, I don't want to have to pay a company to do the work for me. the capabilities page makes it look like they cast the urethane by mixing two compounds, instead of melting and injecting it. strange, because most of the rubbers that are mixed and cast seem to be mostly for "arts and crafts" mold making, while thermoplastic elastomers are used mostly for engineering applications. that's probably mostly because of the expensive equipment involved, though.

rdubard - I don't like the wheels i've seen on the market. I can make something that is stronger and faster to replace in my robot, if I do this it's something else I've learn how to do, and i'll save money while doing it. the only downside is, it's going to be a bit mind numbing to make 4 wheels and then replacements...

I've found two sites that look moderately promising for the mix and set type:

http://www.uscomposites.com/moldmaking.html
http://www.polytek.com/products/poly_mold.html
Back to top Go down
rjw
Chief Bottle Washer
Chief Bottle Washer
avatar

People Skills : 5597
Registration date : 2009-03-31
Location : Miami

PostSubject: Re: casting rubber wheels   Wed Jul 22, 2009 2:32 pm

Colin...

try this experiment before re-inventing the wheel...lol (literally)

1) take a colson performa and drill a series of holes near the ouside edges.....they become really pliable like ripple wall slicks...hre's an example



2) spray brake cleaner on them and try them out....they react with the cleaner and become soft, gummy, sticky, etc. traction is amazing..texture is like an eraser...some rubber will be left on the floor during burnouts.

don't tell anyone about this..it's top secret info

we do this and run them on a surface plate to true and flatten them out, because they are convex out of the box...try it...you might like it

everyone else, ignore the man behind the curtain
Back to top Go down
http://www.R2RCR.com
colin



People Skills : 3051
Registration date : 2009-07-14

PostSubject: Re: casting rubber wheels   Wed Jul 22, 2009 3:56 pm

thanks for the tip Smile I've heard it before though, it's out there if you look hard enough. definitely a good idea if you're really going for traction, but I don't want my wheels wearing down that quickly.
Back to top Go down
rjw
Chief Bottle Washer
Chief Bottle Washer
avatar

People Skills : 5597
Registration date : 2009-03-31
Location : Miami

PostSubject: Re: casting rubber wheels   Wed Jul 22, 2009 4:48 pm

colin wrote:
thanks for the tip Smile I've heard it before though, it's out there if you look hard enough. definitely a good idea if you're really going for traction, but I don't want my wheels wearing down that quickly.

They don't really wear that quickly....and at $2.50 a wheel, it's pretty cost effective.

Look at car tires.....if you want traction, then r rated tires have it, but they wear quicker than a 100,000 mile tire.

If you're determined to make your own, or need a totally custom size that can't be cut out of an existing wheel, then go for it.

On a side note, I guess if you don't care about height or clearance to the ground, I suppose a single size wheel could last 20 years or more. We tweak our bots for best ground clearance, etc, so once a wheel is worn 1/8", it's toast....different strokes for different folks.

All our bots are still on the same original wheels, but while some of them are several years old, they haven't fought all that much.
Back to top Go down
http://www.R2RCR.com
Cody
2000+ club
2000+ club
avatar

People Skills : 5764
Registration date : 2009-03-16

PostSubject: Re: casting rubber wheels   Wed Jul 22, 2009 9:54 pm

I know we use your cleaner trick and BCA does also.
Talking about the convex shape on several of BCA's bots, the lathe down larger colsons to the size, they are also a wider surface area, but that can also be cut down.
I wouldnt recomend using a roller wheel btw just saying, although OFLB used to friction drive maxons that were machined into his frame(Gene does a ton of innovative things) to roller wheels and they worked pretty well i think
Back to top Go down
SenaiERI
mega contributor
mega contributor
avatar

People Skills : 3590
Registration date : 2009-03-15
Location : Dallas, Tx

PostSubject: Re: casting rubber wheels   Wed Jul 22, 2009 10:18 pm

WOW! I didn't know about that cleaner trick. Thanks for the tip rjw.
Back to top Go down
http://www.SenaiEngineering.om
rjw
Chief Bottle Washer
Chief Bottle Washer
avatar

People Skills : 5597
Registration date : 2009-03-31
Location : Miami

PostSubject: Re: casting rubber wheels   Thu Jul 23, 2009 10:21 am

I haven't even looked to see what the chemical is....so there may be other stuff that works as well or better.

We just lucked into this....we drove some bots around outside and they got pretty dirty. I grabbed a left over can of the brake cleaner and sprayed some of the bot down....then noticed the reaction with the Colsons.

So, I take no credit for the discovery...well maybe a little ....lol

Try it and let us know what you think
Back to top Go down
http://www.R2RCR.com
Cody
2000+ club
2000+ club
avatar

People Skills : 5764
Registration date : 2009-03-16

PostSubject: Re: casting rubber wheels   Thu Jul 23, 2009 12:04 pm

We've used contact cleaner also
Back to top Go down
Sponsored content




PostSubject: Re: casting rubber wheels   

Back to top Go down
 
casting rubber wheels
View previous topic View next topic Back to top 
Page 1 of 1
 Similar topics
-
» Front and Rear wheels..
» 4th Gen Camaro Wheels
» Powdercoat Impala SS wheels?
» 1996 Caprice Alloy wheels CHEAP
» polished ss wheels?

Permissions in this forum:You cannot reply to topics in this forum
Battlebots :: Bots :: Fabrication-
Jump to: