July 16

July 16, 2005

Carbon frame starting to go together!

Since I can't cut out the outside fairing shape until I get the fairing mold, I figured there was no reason I couldn't start building the 'inside' of the bike. That is, the cutouts for the seat, wheels and components. I could even add all of my carbon reinforcement areas and inside perimeter laminations. In fact, I could even install the components and actually ride it.

I also made a list of the parts and estimated the weight. It looks like I might be very close to my goal weight of 40 lbs including the PETG plastic fairing.

So, here is what I did today:

1. I taped my pattern onto the carbon board. This is exactly the same pattern that I used when I made the plywood proof of concept prototype frame
2. Then I punched holes through the diagram on the pattern into the carbon sheet.
3. I used the pin holes as a guide for my cuts. I cut the frame out with a jig saw.
4. Just for fun, I weighed a small off-cut that was about 10" long by 4" wide. It weighed 57 grams - exactly half the weight of Kristas turtle. I know because I borrowed her scale which was sitting on her chart where she tracks Zoey's weight - about 114 grams.

5. I could stand on this small carbon sandwich board and not break it. I weigh 156 pounds and the foam board weighs 2 ounces.

But that's not so great because I also discovered that graphite golf club shafts also weigh 57 grams and they can probably take a heck of a lot more weight than 156 pounds.

The ideal sandwich frame needs to be made of a carbon honey comb - like material in the center - not Styrofoam. I've been wondering how I can make something like that... It would be extremely strong and probably wouldn't require much reinforcement for components and high stress areas.

6. This is my 6061 aluminum headset mounting bracket. I designed it with some help from Mark Stonich. Then I sent the computer files over to my brother Alan who owns AK SIGNS. They cut the shapes with their CNC router.

The headsets fit into 1/2 " thick aluminum blocks that are fastened to 1/4" thick aluminum brackets that will be bolted to the carbon board frame.

The tolerances of the CNC cuts was really, really poor - not what I had expected at all. The holes weren't even round and tolerances were all off.

So, I sent the hardware over to my friend James Kenney who is a machinist. He made everything fit nice and square, then drilled and tapped some fastener holes to hold it all together tight. The fit between the parts is now very tight and square. James says the bolts are good for about 1800 pounds each, so it should be far strong enough.

The headset in the photo is temporary. I ordered Chris King headsets, but they have not yet arrived.

The headsets don't fit with a super tight press fit, so I may think about bonding the headset cups right into the 1/2 inch plates.

The triangular piece at the top connects to the remote steering link.

7. I assembled the front for and wheel to make sure that the slot cut in the carbon board is exactly the right size. The plan.
8. The bottom bracket shell mounting plates are also cut from 1/4" aluminum plate. On the left you can see my aluminum bottom bracket shells from Nova cycle, and the plates that fit over the shells to a shoulder machined by James. The two plates sandwich the shell between then holding them in place.

I was going to weld one plate onto the bb shell, but I could only find 6061 plate and 500 series bb shells. You can't weld the two together. So, I may just bond one plate onto the shell.

Tomorrow I will lay up the perimeter laminations - probably 2 to 3 layers of unidirectional running all around the inside edges of the board. But first, I am going to route a 1/4" radius around all of the edges. Then I am going to add a few layers of the thicker weave around the component mounting cut-outs, and the high stress areas. I am also going to add a lot more carbon around the very narrow area just behind the front tire and the area just behind the seat (in front of the rear tire). I think I'll lay in a few layers of the uni tape running up and down, all around the square tubes, then wind some heavy weave around them.

I am a bit uncertain about how to vacuum bag these perimeter laminations because they run perpendicular to the flat frame. The bag will definitely wrinkle up on the edges. I may test bag it first to see what happens.

One more day, then I take a long break and a European holiday.

gk


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