2 x 4 Lowracer
This page shows the construction of my 2x4 lowracer and the changes I made.
Plans are available from James Robinson HERE.
As part of my job I have to maintain a CNC router. It cuts out of wood or plastic, things that have been designed on a computer. This is the sort of thing I can do to check it's accuracy.
The hardwood inlay is just a bit of showing off really
The parts cut out as per the plans.
I wanted to check how good the design was and try out some changes. As good timber and adhesives are expensive in the UK I used free softwood offcuts and PVA glue for this 'prototype'. Aircraft grade spuce and epoxy resin would build a frame half as light and twice as strong but cost about £100
I was not entirely happy with the way the head bearings were fitted into plates on the original design, so there is a headtube brazed through the steel plate that can be seen in the photo.
I added brake bosses for Vee brakes behind the forks later
These are not the sort you dunk in your tea (unless you're very peckish), but are made from beech wood and can be used to join bits of timber together. I added these to the butt joints and also drilled and dowelled through the join between the 'chainstays' and the frame.
The plate with the big hole will fit on the top of the head tube.
Dropouts are being made from chunky aluminium flat bar. They are glued and bolted into tight fitting recesses in the chainstays.
I used a FAG type sealed bottom bracket with the cups removed. The frame and strengthening plates are drilled to be a very tight fit at 29mm. Aluminuim plates with a clearance hole for the axle are added each side.
I decided to fit Vee brakes using bosses from old forks bolted through a bit of 1/2" birch ply as shown below.
I found that the cable route was important and ended up drilling a hole through the frame for the cable
The first stem I made was welded from steel but on the 'test flight' there was not enough clearance for my knees, and it would be hard to dismount with the bars any closer to my chest. The solution was to make a stem which pivoted upwards - and why not a wooden one! It is a great improvement but could look more elegant. Next time it will!
|The finished bike:
James did a really good job with the design and my choice of materials and woodworking skills do not do it justice.
As you can see I allowed enough wood for a rear mudguard integral with the frame. My method for the bottom bracket did not give enough clearance for a triple chainset and I have not fitted a front changer yet. Wherever possible I rounded the edges off with a router.
Jame's bike not only looks good it feels good too. The seat and riding position is comfy and it does not feel as low as it actually is. Although I have riden recumbents before, I expected it, being a lowracer, to be awkward to ride. I was pleasently suprised to pedal it away first try. The first test showed up some problems with the handlebar position and the chain tubes, these I hasten to add are my adaptions to James's plans.
I raced the 2x4 wooden lowracer at Herne Hill on Sept 7 2003. I was in the first race and made a slow getaway, on the outside of the grid, from the line (120" gear) but passed everybody, except Dave Hembrow, round the outside on the first lap. Much to the amusement of the spectators the wooden bike was in second place with about 50 yds gap on the rest of the field and lapping people by the third lap!
However my recent cold and the 58 miles ride the previous day had taken their toll. With a tightening chest and a dry throat (I wish I had nailed a bottle-cage on) I slowly began to drop back.
I finished the 40mins + 2 lap race at an average of 20.9MPH! The results are recorded here: http://www.btinternet.com/~John.Olson/bhpc/events03/hernehill03.html
The bike is a way of producing a raceable recumbent with limited workshop facilities. It is unlikely to be the fastest or lightest machine on the track, but it might gain the most attention.
The most important point is - It's FUN, FUN, FUN!