July 15

July 15, 2005

A much better day!

I cut out the new chain stay dome, drilled the mounting holes and quick release drop out hole and bolted them onto the plywood prototype frame to see how strong and stiff they were.

First, I fastened them together with wood spacer blocks that were cut to my frame width and sandwiched the wheel to make sure that all of my clearances were right. As I had expected, the partially collapsed chain stay dome was rubbing against the wheel disc, so I had to remove one disc from the wheel. After that, the wheel spun perfectly.

I think I will eventually rebuild both chain stay domes with perfectly curved molds. The reason this mold dips in a bit at the top is because as the plastic cools after blow molding, it expands and the bubble gets bigger. To bring the top of the bubble back down to the correct dimension, I screw it down to a wood block which flattens out the top a bit. A perfectly evenly curved surface would be far stronger. Next time, I will spend some time making a perfect mold. I will also test and retest it to make sure that my vacuum bag is working AND that it won't collapse again!

For now - these will work just fine. They seem plenty strong enough - even though one of them has too much resin and an unsightly dip in the middle. To test the strength, I bolted them onto the plywood prototype frame and went for a quick spin.

It's hard to say for sure exactly what to look for regarding the strength of this chain stay approach. If I grab the fork of my road bike with one hand and push the tire toward the fork with the other, the wheel bends a bit because of the flex of the spokes (which is normal). The same thing happens when I do the same thing when the wheel is sandwiched in the chain stay domes - I guess the important thing is the hub doesn't move at all - it's in there pretty solid. I pushed the tire sideways and looked for any sign of flexing of the outside surface of the dome and couldn't see any movement at all.

After I had cut off the old steel chain stay tubes, the rear end was very, very wobbly. Any weight at all on the seat would cause the narrow wood area at the top of the wheel cutout to start to crack. I was very doubtful that these carbon domes would work on this woody. After I bolted them on though, it was equally as strong and stiff as it was with the previous steel structure.

I wonder if I could make the new chain stay domes without any raised strengthening ribs? Perhaps 2 or even 3 layers of the 11 oz fabric + a few layers of the 3" wide unidirectional tape is all that is required. I may test that approach and if it isn't strong enough, then I can always add the raised ribs later.


I was really pushing hard to make some serious progress on the new streamliner before Tuesday of next week because then I am gone for most of the remaining summer. I am disappointed that I didn't at least get the frame shape cut out of the carbon board. I was waiting (and am STILL waiting) for the MDF fairing mold before cutting out the frame because I want to ensure that the frame is EXACTLY the same shape as the fairing AND there are some very tight toe clearance issues I want to make absolutely certain of before committing to that bottom bracket position.

I may be able to cut out the seat hole, component mounting areas, and wheel wells without cutting out the actual fairing shape... I may look at doing that this weekend. Then at least I could start laying up the carbon reinforcement areas for the components, seat, wheel dome mounting areas, etc.

The CNC guys who are building the fairing mold are letting me down. You know, I think that is a large reason why I feel so compelled to do things myself - because you just can't count on anyone anymore. It's not like the old days where businesses would break their backs to serve the customer. Now if you aren't promising huge future contracts then they just don't care about you. I think it sucks. In my businesses, customer service was Very important The future potential of the customer was never a prerequisite to excellent service.

Oh well, I guess I just make progress as my time permits. I have until the end of Oct for my target event, but there are some friends that would like to see me compete at the World Human Powered Speed Challenge at Battle Mountain on Oct 3rd. Even if I make no further progress until the end of August, I suppose I would still have enough time to have it built by the beginning of October.

gk


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