Short Wheel Base Recumbent Bike No 2

The bike is made mainly from 16 and 20" acquired bike parts and car exhaust tubing.

My original intention was to have just one skate wheel to route the chain but this didn't work out. Many Recumbent low-racers have the chain travelling beside the front forks - not sure how they do it as on this one the chain would run on the fork leg. Looking closely at some of the pictures it looks like they curve in the fork where the chain passes and/or offset the BB so the chain is held out off the fork more than is normal.

Seat - Tried to cut down on weight here so used thin 3 ply for the base and a camping mattress for the padding. It's deceivingly comfortable actually, fine for rides of an hour or 2 but needs a lot more thought to make it look more appealing. The metal frame is an old kitchen chair, square tubing that is quite thin.

Handling is a little quick, probably no more so than other SWB models though and still stable at speed. (at least up to 80K/hr) There's a little heel interference with the front wheel and front brake callipers at full turn but I was keen to make it as long a wheel base as I could.

Steering - The bike was first made with above seat steering. See pic 1, pic2, pic 3. There can easily be clearance problems with USS, especially when the machine is quite low but I decided this was where I was wanting to head.

Then I thought about trying out this under-seat system design - The idea is to use bike chain to connect the handlebars to the forks. A tube is welded to the top of each fork crown so that bolt can pass through it. The bolt is used to tension the closed loop system. The end of the bolt is flattened out, a hole drilled into the end so that the chain can be clamped on as they usually are using the chain pins. On the handlebar side either a lug is welded onto the bars or a metal strap wrapped around the bars with the chain clamping on again with it's own pins as usual. All of this looks like it would work but I ended up going the solid rod way.

Handlebar mount - The handlebars were mounted as described here, option 5. The difference is I added to the tube a bike steering head clamp (see another pic) but am now regretting it. I've found it places the steering rod pivot out in front of the handlebar pivot and makes the steering path non-linear. A metal strap with rubber insert (bought from a tool shop) wraps around the bars and the steering rod bolts to it. Might go back to the original design.

Gear shifting - Bar end shifters have really fascinated me and seem like the way to go but I can't afford to buy them (at $120 a piece) so I had a go at making them myself. Here are some closeups Pic 1, Pic 2- It wasn't a complete success - well there are limitations I found as I made them but I think they're better than what I had before when they were mounted on a short steering stem in the more conventional place through the forks. Check here for additional info.

The things that aren't so good are:

1. Now they're welded on it's going to be hard to get handgrips on. (I made it with them on because of this reason but they also got a bit hot when welding, had to dunk in water a few times so the rubber wouldn't melt) I didn't notice this before but the mount for the lever isn't straight up from where it is fixed to the bar end. It has to head away from the center where the cable exits if you know what I mean. For this reason I used the existing mount as it would be a little fiddly to make but it makes it hard to fit the hand grips. It doesn't make it easy to finish off the bar end so it looks great.
2. It's hard to put the cables in. They go up into the handlebars so you can't hold the inner and feed it into the outer unless the outer is in 2 pieces. (as there's a lot of inner inside the handlebar and out of reach) Still I got it in but if it was a difficult cable to get in it just wouldn't work.
3. I've made the bars so they aren't too wide but now I can get my jeans caught on the shifters on hard turns if I'm not careful.

Chain Guides - All of these straps use the same size tubing or next size up as what they're mounted on. The strap is made by cutting about a 40mm wide piece of the large tubing. Weld on a small tube along with a nut at the end of that tube. Alternatively use a long nut. Split both tubes with a hacksaw to make the clamp gap. If using the long nut, drill out the thread on the side with the longest tubing. On a few occasions I've found I needed to split the tubing first and open the gap a little before welding on the mount tube. Using 2 wheels on different sides. See pic 1, pic 2, and drawing. I mount the wheels close enough to capture the chain so it can't jump the groove. Using a mount on both sides See pic 1, pic 2 and drawing Using a single mount on one side. (Will work best if the clamp can be slid on the boom as bending it open to get on a boom may end up splitting the clamp) ) See pic and drawing Skate wheels are used, see these pic1, pic2 on how to grind the groove. These 2 wheels were made close enough together so the chain is captured in the groove. N.B. Some of these pictures are taken upside down)

Seat mount (shown upside down) The strap is made by cutting about a 40mm wide piece of tubing the same size as the boom to which it will be mounted on. Weld on a long nut each side of the tube or alternatively use a small tube and weld a nut at the end. Split both sides with a metal saw to make the clamp gap. If using the long nut, drill out the thread on one side.

Boom clamp. In the past I have used an external clamp but found this to be a lot lighter and easier to make. All the commercial ones I've seen that have this also have 2, I can see why now as it slipped with one so I've also added the extra one. A long nut is welded to the tube then both split down the centre. The thread on one side is then drilled out.

Specifications Frame Dimensions   Wheel size Front 16" Rear 20" Gears 12 speed Front 40t, 52t Back14t - 30t Seat Height 360 mm Total Length 1.73 m Boom diameter 50 mm Seat tube (Sq) 18 mm Seat dimensions Base Back 300-160 W x 220 long 300-260W x 430H Wheel Base 1.094 mm Trail 35 mm Handlebar height above neck with ASS 300 mm BB height to centre above ground 480 mm
Video Pics of the machine in action Riding away Riding around 10 sec MPEG video viewing size 320 x 200, 924k 15 sec MPEG video viewing size 160 x 112, 344k

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Friday, 30 January 2009