Monday, October 5, 2009

MDF Horseshoes

I've been trying to get a little side project finished up in time for R2LA. R2's horseshoes (the assemblies on the outside of the shoulders) are one of the trickiest parts to build yourself. The options out there are aluminum, or a styrene laser cut pack with layers, or build it yourself. I did a pair with PVC that had potential, but some alignment issues and glue problems didn't work out. I got the idea to do them in MDF from Jamie McShan. The problem is all the little grooves on the inside and the recessed pockets. All are hard to cut precisely. If you build up the horseshoes with layers of material there are alignment problems and lots of work.

So I've been scheming for a long time about a way to do them with a single piece of MDF and some clever cuts with the router. Here's the results. These are good. They are better than the set that I built for my own droid. I don't know if there's a need for them, but I'm going to take them to R2LA and see if people are interested in them. If so, I think I can mass produce them quite a bit cheaper than the aluminum ones. The other advantage would be that I could offer mine frequently. The machine shop runs for aluminum horseshoes in the club are relatively rare. Check it:

My digital camera doesn't do well with super closeups, but you can tell here that the grooves are all really clean. This is the pay off for using a single piece of MDF (1" thick). I don't have to stack, glue, and line up 8 pieces. I'm using a router, the router table, and a 1/8" slot cutting bit with a big roller bearing on it that limits the depth to 1/8" deep. So once the router is set up, it's easy to just ream these around against the bearing and mill the groove out. In fact, it take's longer to set the router up than to actually do the cutting. One trick for efficiency that I want to pursue is building up several slot cutters with 1/8" spacers in between them, so I can do all the grooves with one pass through the router. But that will be a refinement of the process later.

Here's the backside. On this pass through the router, you run the piece all the way around. The result is the shim that holds the horseshoe out from the shoulder.

I've made a stack of these and I'll see if there's interest in LA. I think they will all sell immediately, or they will be ignored because people really want aluminum.

It's taken a bunch of development to get to where I can make these, so I hope that it won't be wasted. I think there are going to be some builders out there who are limited on space and shop tools for building stuff like this, and who don't want to spend all the money on aluminum.

The trick on these now is painting. The MDF soaks up a lot of primer, so that takes several passes and some light sanding with 320 grit, or so. Then the order of white and silver paint matters. It's better to paint these white, or at least paint the top faces and edges white. And then it's not too hard to go back and mask all the white off leaving the soon to be silver parts exposed. Then lots of light passes with Rustoleum metallic silver gave me some good results. But it takes patience to get a good coat of it down into all the grooves, the pockets, and around the shim.

Mounting can be done in the back of the recessed pockets. There's enough room to hide a screw that goes right into the shoulder, and then the shoulder buttons or the shoulder details cover the screw head up. You can see the results in some of my earlier posts. If I start selling these to the club, I'll put up an organized post about the whole process. Email me for more details about cutting them, if you're interested.

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