T-REX – SWB – (Short Wheel Base)

My third project came about after reading so many positive comments from SWB owners about the Rans VRex. At the same time I wanted to find a better solution for a frame jig. This discarded electronics data rack was the perfect solution.

I’d been collecting several bike frames and hade already chosen and cut the pieces that would be fitted together for this project. The head and top tube are from a mountain bike to which was added about another 8” long tube of the same diameter. The down and seat tube with bottom bracket were used to create the front boom. The rear triangle is from a 24” 10 speed and the long, square ½” tubes running between bottom brackets are from Lowes. After aligning, clamping and checking over and over for straightness the frame was mig welded. This was a very easy build thanks to the frame jig.

Removing the handle bar clamp portion and grinding the stem smooth makes a cheap ‘quill’ type stem. A 16” long, 1” dia tube with a slice cut 1-1/2” straight up from one end will create a nice riser tube. Using an old style seat clamp along with a very short quick release will make a great clamp to attach the riser to the stem at the base. An uncut stem inserted at the top and tightened down holds the rotated downward cruiser handlebars. Four cable stops were arranged in a row under a simple pipe clamp and brazed to the front of the riser on each end for the brake and shifter cables.

I used an oversized AXION bike seat as a base for creating a fully adjustable recumbent seat The first pic in the panel below shows how the back connects to the bottom of the seat. The back is ¾" EMT brazed together. Small L-brackets are brazed to the cross tube to connect the seat struts. Top crosstube is ½".

The back connects to the base through ¾" EMT connectors. These connectors attach to 4" mending straps, which are bolted to the seat base and bent at a slight angle to allow the back to pivot smoothly. The second and third pic shows this in more detail.

The seat struts were made from the seat and chain stays of an old bike. They did not taper at all from one end to the other and the seat stay OD was a micron or two less than the ID of the chain stay so one slides into the other without binding. When these stays were cut off the original bike I left a small piece of the dropout connected to each one. The piece of the dropouts were shaped and had holes drilled in them where they now attach to the seat back and dropouts on the new bike. Small clamps set their adjustment.

The seatblok, fourth pic above, was a piece from an old exercise machine. I cut a piece of the pipe the block was welded to and brazed a steel tube inside the square block so it would not collapse when the seat was tightened down on it. T-Bolt band clamps hold it to the frame.

I didn't sew the seat back, just folded over the edges a few times and temporarily taped them down. Using a soldering iron holes were melted every 1-1/2" up each side and tapped in a grommet. The cord is just regular poly cord from the hardware store.

The chain idlers are completely scratch built from spare parts just hanging around the shed. (Finally replaced with Rans idlers)

After the bike was completed I found a cheap 20” Ballistic shock fork that had been on a bmx but it was obvious the springs weren’t meant for an adults weight. Sometime back, though, I read where ACE hardware had springs that would replace these and were much stiffer. It’s true except for being about an inch longer and needed a trim. Once the springs had been replaced and the fork installed on the bike they preformed like a brand new set of shocks, not too stiff or spongy.

Below is a pic of the completed bike and it rides sweet. Components used are Avid SD3 brakes, Shimano 105 front and XT rear derailleurs, Shimano 12-30 cassette and Cannondale 52/42/30 crankset.

UPDATE: Spring of 2005 Upgraded both wheels to new lighter weight Shimano rims and hubs along with 11-32 cassette. I replaced the skate wheels with Rans idlers. Added Cateye front/rear lighting and found a cheap ($3) rear rack and pack. The seat fabric was replaced with a spare I had for the BikeE.