12-23-2012, 11:45 AM
Joined: Sep 2010
Location: Tacoma, WA
Chain Guard Finishing Process
I gave Erik the chain guard at our little Christmas party yesterday and I think that he really likes it. It looks great on the bike as well.
Now for the finishing process as promised.
After pulling the part from the mold, I trimmed the the part, and then gave it a good sanding with 80 grit paper to smooth it out a bit. You'll notice the gaping hole in the part where the screw is supposed to hold it to the swing arm. We'll deal with this in the next steps.
With the molding process that I used for this part, it wasn't possible to mold the front and back structure of the bolt hole at the same time, which is where the next steps come in.
I placed the trimmed part back onto the mold. The focus is on the mold structure where the bolt goes. We have to build up the back part of this structure.
First, we use this little water bottle cap as a mandrel to create a little cylinder of aluminum foil.
Next, we secure our aluminum cylinder over the carbon bolt hole. The aluminum structure acts as a form that allows us to build up the back side structure.
I chopped up some left over carbon and mixed it with epoxy in order to create an epoxy based solid that is still reinforced with carbon fibers. The epoxy on its own would crack and break much more eaisly.
Next I filled the aluminum form with the epoxy carbon mixture and allowed it to cure. After the mixture cured, I ground the back side structure down to match the structure on the original part. Then I simply drilled the hole in the middle to allow the mounting bolt to pass through.
You'll notice the built up bolt structure in the following pic.
Now finishing begins. I sanded the part with 220 grit paper to get it fairly smooth.
A thin layer of epoxy was then applied in order to fill any small pinholes. This was left to cure under the heat lamps.
The part was then sanded again with 220 and sprayed with clear coat. The clear coat was then sanded with 800, 1000, 1500, and 2000 grit wet paper. The resulting surface is very smooth, but still looks flat.
Next I used buffing compound followed by polish to bring out the sheen of the clear coat. Carbon fiber looks very cool when it is shiney.
The part is finished.
Of course we use carbon fiber to make parts for a reason, right? We want a stronger part while saving weight all at the same time.
The original part weighs in at 135 grams.
The new carbon fiber part weighs in at 99 grams for a total weight savings of 36 grams, or 27% of the total part weight.
This is not a lot of weight savings compared to the total weight of the motorcycle overall, but if you can imagine having many components made out of carbon, you could have a much lighter machine if it weighed 27% less.
You gotta love that carbon!
Next up is a set of hand guard ferrings to protect inmate Zoomzu's sensitive hands from the wind. This project will be a ground up project all from scratch. We'll be building the plugs, molds, and laying up the parts. If the composites gods are shining on us, we may even use resin infusion to make the final parts.
therivermonster screwed with this post 12-23-2012 at 02:18 PM