How to make a plastic (UHMW) skid plate

[Muggzy]

Ok So I bought a top of the line ($130) plastic skid plate. The fit and mounting design were terrible. So after looking into the cost of materials I decided I could do better and just as nice looking for less;
1/4" x 24" x 48" Black UHMW off Amazon - $75 shipped (prime)
2 - 10pks of 1" Plastic coated loop straps off of McMaster - $14 shipped
8 low profile M8-1.25 x 20mm bolts from an old set of front rotors - free
Satisfaction of a reliable skid plate that won't fall off on the trails - priceless

(EDIT) I ended up covering the entire bottom of the quad; Belly, shock linkage, swinger, and (coming soon) A-arms with the one sheet. NOBODY makes a set (alum or plastic) to do all of that!

 

[Muggzy]

Sheet plastic:
http://www.amazon.com/dp/B0070ZAXUK/?tag=jyj356j5-20

or http://www.mcmaster.com/#4296a66/=yed8o0


Straps and hardware:

One of the screws that were recovered from two front brake rotors I had left over from this build is visible in the very top of the pic and in the strap on the package. It's got a nice low-profile head and the shoulder height is let than the 1/4" UHMW Plastic that I purchased. The nuts were also left over from the hardware kit that was bought for the build but they're same as the stock lug nuts with teeth on the bottom

 

[Charles]

No photos of the install? Or have you not yet started, and only ordered the parts?

 

[Muggzy]

Funny you should ask. I was starting to post as I went along but it was soo distracting that I just took pics as I went. As a matter of fact, I just finished (though I am missing a few screws lol). I'll post up the pics and descriptions tomorrow. I'm VERY please with how it came out. Sorry I've got to leave you hanging, but "tune in tomorrow - Same Bat channel, same Bat time". Or not

 

[Charles]

...lol

 

[Larry's Shee]

Member "Blamed" did a skid plate, might want to check his out too.

 

[Muggzy]

Stand the bike up to get measurement and test fit as you go...

 

[Muggzy]

Used the cardboard that the plastic came in to make the template. Using a sheetrock square and the pretty clean edge of the cardboard I was able to carefully transfer the frame to the cardboard. Starting at the top (front) and worked my way down noting the bend lines and critical points along the way. This part took a couple of hours.
The specs on the straps are 1" dia. x 1" screw offset, meaning the mtg screw hole is 1 inch from the center of the 1" pipe that the clamp is wrapped around. So I attempted to layout the centers lines of the frame, making a 1" line to the inside for the screw line. The 2" line around the outside is so I can (hopefully) bund the plastic up around the edges of the frame.

 

[Muggzy]

After checking and re-checking (measure twice, cut once , the template was cut out with a fresh blade. The holes were drilled after the cutout was positioned on the frame to see where the clamps would have room. I should mention that the "Tail" to cover the shock linkage was a last minute idea. After polishing it for the build I want that protected too. When I laid the uncut pattern on the plastic and saw how much extra I'd have I figured "why not?"

 

[Muggzy]

Another pic of the screws with the bits I used to drill the cardboard and plastic. The smaller drill was the size of the shoulder on the screw and the larger drill the size of the head. The larger drill was modified by grinding off the outer cutting points still visible on the small drill.

 

[Muggzy]

The plastic was marked with a sharp scratch-awl and cut with a new sharp jigsaw blade. Then the counter bore holes were cut with the modified larger bit 1st and the through holes were drilled from the opposite side so the points of the drills would both have enough material to center their points. It's this reason that I didn't go a little deeper with the counter bore as I would have liked.

WARNING: It should be noted here that the drilling was done with a drill press. Not the hand drill seen in the background.

 

[Muggzy]

A piece of scrap material was used to make a test bend on a strip heater (a heat gun and patience could do the job too). I'm no expert but I know from experience that plastics have very different behaviors when trying to heat bend them.

After seeing how much heat would be needed over long distances, I decided to bail on the idea of curling the skid plate up around the sides of the frame like the aluminum one that I had on my earlier bike. I also discovered that the material would crack if bent away from the heated side and that if I bent it back toward the heated side, the cracking "healed". Once cooled, I tried to bend it back straight to see how badly I'd damaged it, but was surprised that I couldn't get the cracks to open back up The material was heated this hot to see just how hot it would need to get a tight bend. This was a really important part of the learning process. (I'll explain more in a later pic)

 

[Muggzy]

Some of the more elaborate bends I'd planned and the excess material was trimmed off. I left a 1/4" overhang on the side and still plan on curling the front.


Here's the skid plate before bending

 

[Muggzy]

One of the nice things about working with the 1/4" thick material is even though it takes a while to heat through, it stays hot for a long time so you can get fixture on it to hold it in the shape you want once it's cooled.



I did something similar for the front curl but forgot to snap a pic.

 

[Muggzy]

The finished skid plate:

 

[Muggzy]

Straps still in place from when I test for the cardboard. And I notice that he swingarm skid needed some love too

 

[Muggzy]

I fits really well

 

[Muggzy]

For the swing arm glides that i put on that skid plate, I used counter sunk M6-1.0 x 12mm FH SS screws that my local HD happens to carry but I cleaned them out of the 12 they had on hand

 

[Muggzy]

Views from the top

 

[Muggzy]

The 1/4" overhang I left ought to do the job of protecting the sides of the frame. One thing that I hated about the curled edges of the aluminum skid plate that I had on my first bike was that you couldn't get the crud out of the edges. This design has a nice 1/8" gap all the way around that will allow me to pressure wash the mud out.