Tom Porter LWB

Tom Porter's Finished 2010 LWB

I see that is has been too long since I posted anything. First I’ll explain what’s been happening. It took several attempts to get the Dual 700c refined. The first bike was a wet noodle that had the frame crack after about 10 weeks from all the vertical flexing. Next I built a few bikes with larger round tube diameters. This lessened the flexing, but still wasn’t what I was looking for. After talking to Mark Colliton at the 2007 Stevens Point recumbent rally, I decided to go with a teardrop shaped tube.

 I tried using pine blocks at first but these cracked easily and couldn’t handle the stress of the pressure necessary to form the tubes.

So in the spring of 2008 I got some pecan blacks from a woodworker friend. First I roughed out the shapes on a table saw, then I made a scraper of the profile I wanted and scraped the blocks to their final profile. When I tried to form the 2” x .035” 4130 tubes (Fairing Industrial seems to be the only place to buy a small amount) the pecan too eventually cracked at the thinnest point. I glued and clamped the pieces back together and when dried I inserted hardwood dowels.

This too couldn’t take the stress. My solution was to make holding blocks out of ½” 6061 Aluminum. The idea was to completely encase the wood block so it couldn’t move to crack. What a lot of work to say the least. The first photo is to show the profile of the wood block(s).

This picture is of the aluminum holder/case


 

Now the whole unit mounted in the vise for forming the tubing.

And the final shape of the formed 2" tube.

Here's the completed dual 700C high-racer.

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