Alternative materials

[Fat-Alfie]

I worked in the sign trade for several years and as an alternative to aluminium sheet for sign we started to use a material called Dibond. This is a sheet of polyethylene with a sheet of aluminium bonded on either face. It's very still, light and easy to work with.

I've just made a 4-link plate out of some, and am considering making a TVP chassis out of it next.

Anyone else use non-standard materials for stuff?

Pic of some Dibond...

[beomagi]

Wow, neat I'm going to have to try that.

I USUALLY make small fast bashers. I'm new enough to rock crawling that I barely have a foot in yet - my first machine isn't a full crawler, nor is it even done ;)

As such with speed, I need to look at high impact resistance materials. the material I used last was UHMW polyethylene (Ultra high molecular weight).

I got a board 2'x1'x0.125". To test, I beat on this with a hammer, pinched a small corner with pliers and flailed around hoping to see if it would collapse on it's own weight. NADA.

It's not being used in my crawler currently. But my rc18r/xray dohickey.



It's imo the turkey jerky of plastics.

I've been looking for something stronger, but haven't found it. I do like the idea of sandwiching it between aluminum. Metals are generally stronger in tension than compression, so a thick center of light plastic does sound interesting. How is it bonded to the aluminum? doesn't it delaminate when working with it?

I've done a little research of physical characteristics on plastics.
fyi - for dotmar, their polystone = uhmw poly.
http://www.dotmar.com.au/solutions/impact.htm

Their nylon 703xl looks good for rock crawlers that are rough on their vehicles, as it's no slip stick (static friction = dynamic friction) and overall low coefficient of friction. It's also one of the highest strength plastics they've got.

I know delrin is popular (it's one of the sheets I got in the first picture, the other is nylon) but I'm not impressed with it. It's tough, but can snap. It does have good self lubrication and I know that's why it's important, sliding on rock. But it's not as tough as nylons or polyethylenes. I also get that crawlers are slow and don't need the impact resistance.

[tomik]

Nice anti-squat setup. Have you calculated the amount of AS?

[Fat-Alfie]

No, not yet - I started to look at the 4-link calculator spreadsheet that's floating around, but I'm a total novice at r/c cars (inc. crawlers) so I'm doing lots of reading and experimenting at the moment.

My way of testing for improvements is a 2' x 1' board with coarse glasspaper bonded to it. Then I set it pretty steep (65°) then crawl up as slowly as I can. This lets me see just how much the front-right lifts off the board. I know it's hardly scientific but it's helping me learn.

I'm not sure how the ali is bonded to the PE but I do know that it doesn't delaminate when you work with it. I've cut it with a hacksaw, drilled it, filed it.. nothing.

There's a spec sheet here if anyone's interested

http://www.signforce.co.uk/Signforce...tasheet-en.pdf

[tomik]

I've messed around with a link calculation Excel sheet too. Helped a lot. At the moment I have AS value ~115%, but I don't even have a clue what's it supposed to be. Help, anyone?

How much weight are you carrying, Fat-Alfie?

[demonoid369]

you got a wierd 4 link setup whats one doing underneath and one on top!!!

[Miller Tyme]

Originally Posted by demonoid369

you got a wierd 4 link setup whats one doing underneath and one on top!!!

Raising the left rear upper link like pictured helps counter torque steer caused my motor rotation.

[Offroader5]

Originally Posted by tomik

I've messed around with a link calculation Excel sheet too. Helped a lot. At the moment I have AS value ~115%, but I don't even have a clue what's it supposed to be. Help, anyone?

How much weight are you carrying, Fat-Alfie?

That's quite a bit of AS. If you're running a sprung suspension it won't show or hurt as much as if you're running a droop setup. If you run that much AS with full droop suspension, you'll end up with a lot of unloading (shocks extend when the truck encounters resistance, instead of the power going to the ground...it transfers into the shock).

[tomik]

Originally Posted by Offroader5

That's quite a bit of AS. If you're running a sprung suspension it won't show or hurt as much as if you're running a droop setup. If you run that much AS with full droop suspension, you'll end up with a lot of unloading (shocks extend when the truck encounters resistance, instead of the power going to the ground...it transfers into the shock).

I am running AX-10 with stock springs in rear and softs in front. Left rear shock has the biggest preload-piece too (the "C"-bit). What would be the "optimal" AS value? 0%? 100%?

I've already tried the same as Fat-Alfie with the difference I had rear right (when looked from back of the car) link on top of the servoplate and left raised ~10mm. That caused the car to have way too much twist and climbing was almost impossible. Now I have both upperlinks under the servoplate with 3mm spacers and it works much better. Also the axle movement is smooth now.

[chrisjlittle]

Originally Posted by Fat-Alfie

Anyone else use non-standard materials for stuff?

I use ultra high molecular density polyethylene for skid plates instead of delrin. It's slicker, more abrasion resistant and cheaper. It's a bit more flexible and doesn't hold threads quite as well, but you can get around that by using longer screws and thicker stock. I like it, and I have a ton lying around.

[LAV25]

This looks like the same stuff I was asking about here: Aluminum Composite

Subscribing to this thread to see how it works out for you, thanks for taking the first shot at it!

[Fat-Alfie]

Well, I'm not too sure about making chassis plates from this composite material now - the 4-link servo plates I made from it have started to bend where the upper links are bolted on. Admittedly I am using spacers to move the link away from the plate, so there is added turning momentum there.

Still, it might work for chassis plates as I suspect there will be less twisting force in that application.

[Destroyer]

I had a chassis cut from that material, but traded it before I ever got to build/run it (the dimensions were slightly off and I could not use it with my setup). It seemed decently strong, and with proper bracing it should be fine for a smaller chassis such as mine. I am having a new one cut today from the same stuff; I will let you know how it works out.

I've also made a chassis with a UHMW skid and lexan sideplates, which worked fine with 2 alu braces.

Pic of that setup:


-Destroyer