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Old 02-16-2013, 08:22 PM   #22
Plaka
Brevis illi vita est
 
Joined: Jun 2010
Oddometer: 4,582
Quote:
Originally Posted by VxZeroKnots View Post
Sweet info man thanks! Looks like CF is out. I'm not making this particular skid for the engine, as I already have one of these
and it is killer. It gouges pretty easy but compared to the Aluminum skid I had on my last bike it is brilliant. It is 1/4" and the "wings" are folded up from the bottom piece and then welded at the bend so the part that sees the most abuse is all one bit. I bought a Hyde racing skid plate and was very unimpressed with the fit and quality of it given the price.

The Hyde is made from 1/8" and the parts are joined via the pop-rivet method you outlined. I ended up cutting it up to where just the pipe guard bolts to the AXP skid plate and then mounts to the pipe with the included band thingies. It has a bunch of little rubber nubbins which isolate the pipe from the skid portion and it seems like those coupled with the shape of the guard are what provide the protection more than the thickness of the material.

My plan is to build a faceted pipe guard which integrates better with the AXP plate out of 1/4" HDPE seaboard and try to use as few separate pieces as possible and weld as little as possible.I already have a rivet gun so I might make some gussets for the major seams and pop-rivet them over the seam to reinforce it, but was thinking of using 1/8" HDPE for that. My research today didn't turn up any UHMW that was black or UV resistant so if you know a source for that I'd love to hear about it. Also, I think the rubber nubbins Hyde uses are silicon rubber for heat resistance because they spend their whole life in contact with the pipe. I don't know where those are sourced from but if you have any insight for a solution there I'd appreciate it.

Thanks for all your input!
I get my plastics from the scrap bin at Tap Plastics or scrounge them (I just tore down an old wheelchair, got two nice slabs of thermoplastic, black to use in some project and a LOT of nice bushings and connectors for 1"tube.. You can sometimes get smaller pieces from McMaster Carr, (online or local depending on where you are). Also McMC on rubber bumpers. But you could also make your own. Take a short peice of pipe and lube the inside up well with vaseline. Set it on a flat surface also lubed with the vaseline. Squirt in some high temp black silicone from the auto parts place. Do not fill your mold to the top. let it set up (days). Then take a small bolt and thread on a nut so when the bolt heat reats on the top of the silicone the nut will be just above the top of the mold. Secure that nut with read locktite (stud locker). Put the bolt back in the mold and top the mold up with more silicone. When it's done Push it out of the mold. Now you have a silicone bumper with a "stud" sticking out of it and a wrench flat on the stud to hold while you tighten on another nut on the other side of whatever you are fastening to.

You can also cast in a coupling nut (Used for joining threaded rod, hardware store) and leave that sticking out just enough to get a thin wrench on (Thin wrenches from bicycle shop). Coupling nuts can be an inch long, depending on size, and you can saw or grind them to the ideal length. This gives you a bolt (A nice rounded button head rounded allen capscrew please) on the outside.

UV resistance is a non issue on something you expect to last a season, even at high altitude. 5 years in the sun and you get surface oxidation, nothing more. Spray on some 303 all or similar if you want. Has sunscreen in it.

Thermoplastic sheet will stay where you put it if you bend it hot. Polyethene is difficult to hot bend because it transmits heat poorly. Hard to get heat penetration to make a stress free bend. Not a problem with Kydex. Another resin to consider is lexan. VERY tough, Comes in smoke or you can dye it to a dark smoke (Use RIT), or just paint it. usually easy to get scraps and 1/4" is a common thickness. You can solvent weld it but the welds are weak. best simply thermoformed and let it go at that...or use mechanical fastenings. it has poor chemical resistance. Keep it away from gas, oil, sticker glue, etc.

For ease of fabrication little beats fiberglass. Use epoxy resin rather than polyester if you can (less toxic, allows you to use the lost foam technique). Invest in a couple rollers (like three for $25) because you will be thinking up more projects to do with it.if you have some part that you know will get trashed then make a regular wood mold so you can turn out more parts whenever you want.

For your particular application it sounds like you want some shock absorption behind a very rigid plate. Use the silicone bumpers.

if you work with 1/8 or even 1/4" foamcore; make a strait bend by marking your bend line then drawing the ass end of a bic pen along the line to crush the bend line on the inside. The board will then fold nicely on that line. A hot glue fun is your friend. It is well worth your time to model the part in cheap foam core before you cut costly plastic.

Plaka screwed with this post 02-16-2013 at 08:29 PM
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