Warren Beauchamp's recumbent bicycle and human powered vehicle (HPV) web site!
The (Mostly) Steel Racing Trike
Warren Beauchamp - 10/2017

Overview   Steel Racing Trike  CF Racing Trike

This web page will document building of a mostly steel recumbent racing trike.

Before I build the CF version, I want to build a version out of steel to work the bugs out of the design. I'm going to use the frame and parts from the Street racer 2 bike. I don't ride it and nobody wants it so it's now a donor bike. Front wheels will come from the tilting trike. I'll use a CF seat that is left over from another bike. I'm going to try to keep the geometry the same as the CF version. 

After a bunch of measuring, here's the 1X drawing of the kingpins. Kingpin inclination is 76 degrees, for a 406mm wheel with a medium width tire. Steerer tube is 1 1/8" OD, the head tube is 1 1/2" OD.
Here's the frame layout drawing. 44" wheelbase. 5" seat height. 14" BB height. Trying now to figure out if I can fab up CF tubes that will clamp over my 2" tubes so I don't have to use heavy 2" x .049 tubing for the boom and bottom tubes. I bought some shrink tube sleeves to compress the CF layups evenly.
It took 5 hours to cut, mitre, jig, tweak and braze this joint. And it's off. How far off? Looks like the BB will be at 10.5" now instead of 14" as planned. 6" crank length plus 7.5" of shoe = 13.5" to the ground with foot hanging straight down at the bottom of the pedal stroke.

Apparently my plastic angle measuring tool is not good for low angles.

Fortunately your foot doesn't normally hang straight down at the bottom of your pedal stroke. I measured on my bike and it looks like I need about 10" of ground clearance while pedaling normally. Hmm. I'll try it and have to tweak it a bit if it's not enough clearance.

Making the kingpins
I don't have a lathe so I had to fake it with concentric tubes. The holes in the sides of the tubes are to braze the tubes together. I was able to create the proper angle hole in the steerer tube with a 3/4" holesaw.
To make the bearing seats I used 1-1/4" x .058" tubing to fit over over the 1-1/8" steerer tube. Brazed in the bearing seats and the shims for the lower bearing race and then did a test assembly of the headset assembly. So far so good!


Made the 1X cruciform drawing. If I make the cruciform tubes straight my thighs may hit them, so I'm going to try to bend them.

Looks like I need to order some 1.5" thinwall tubing for the cruciforms. I thought I had some but it's heavy .058 wall.
The 1.5" x .035" tubing arrived, and I stuck it in the tubing bender. Here's my tube bending demo video. After some work, the tube is bent to the correct diameter, yay!

I had cut the wrong sized hole in the boom tube for the cruciform, which basically ruined that tube. That's probably a good thing because it forced me to cut it off and make a new one that is actually at the right angle. This picture shows the boom stub tube tacked onto the main frame, with the correct size hole cut into for the cruciform tube.
Here's the cruciform tube inserted into the jigged up frame to eyeball it. Looks fine.
I made the fish mouth cuts into the cruciform tube, at the correct angle of 76 degrees to match my kingpins. To provide the correct caster (trail), the cruciform will be angled backward at 12 degrees. This should look fine as it will be about 90 degrees to the boom tube.

All the tubing holes and fishmouth cuts were done in my drill press.

Yesterday I tack-brazed the kingpin head tubes and the cruciform in place. Yes, I had to do a bunch of measuring and re-measuring to make sure it was all straight, but I didn't build a special trike jig. I hope i don't regret that decision!

Today I added the wheels and eyeballed it and did some measurements to make sure all the angles are correct. It looks pretty good.  The next step will be to build the Ackerman steering and brake brackets and then add them to the kingpins.



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