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Moz: The Tall Bike

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Tall bike as ridden

Completed: December 2000

Note, Feb 2002: I found a link to another tall bike in the Canberra Bicycle Museum, where there's a parade bike that's also quite tall. It's down a bit, called "Wheels".

I was riding my racing trike to work every day, which was something of a hassle. I was working in Hunter St, Wynyard, in downtown Sydney. It doesn't get much more downtown than this, in fact, and the traffic was pretty bad. Being right down low where the exhaust pipes are is not much fun. And the joy of carrying the thing up three or four floors of stairs wears off very fast. It's a bit bulky for that really.

Tall bike as Christmas treeSo I decided to build a tall bike. I wasn't sure that I would actually be able to ride it to work, but it seemed like a suitably silly idea. And it would let me see just how fast I could build something. I started planning on the weekend, went to Ken's house to see what he had lying round, and visited The Bower to check out the second hand bikes. I got a more-or-less working BMX for $15, needing only a new bottom bracket and cables and chain and a few other things.

I've drawn up dimensioned plans of the tall bike in various formats (the CAD and Windows Meta File formats are the clearest). I made these by tracing a photo in Turbo CAD so they should be reasonably accurate (and the numbers more or less match what I got using a tape measure). PNG (20kB) TCW (60kB) WMF (12kB).

sketch plan for the tall bikeBy Wednesday I had a design. The plan was to use a "ladies" 27" frame as the top seating area, cut the BMX in front of the seat tube and install more tubing to make it about 2m between axles, then go up as far as the available tubing would allow. Most of the long, straight tubes are old bike frame bits joined end to end with 20mm or so of overlap, so it's not as strong as you might guess from looking at the plan.

The red bits in the diagram are the original BMX, which was actually a tasty yellow colour. I ended up chopping off the headset complete with fork and using that as it was. I cut the handlebar stem just under the handlebar clamp and brazed a flat plate on. By brazing the extension tube (blue) on at an offset I could drill that plate to take the expansion bolt and the stem worked just as it did before. Likewise, brazing the clamp to the top of the extension reduced the hassles there, I just put the original handlebars back in.

The extension tube ran through the old headset from the 27" frame without bearings. After a bit of hammering there was very little slop and it seemed likely to work. I also steepened the angle a little to make it fit better, then cut half the headset off to make it shorter. Next I carried it up to a bike shop to have the bottom bracket retapped, because it was a bit rusty and I'd just brazed new tubes onto it. And bought a cheap cartridge BB rather than scrounge for open BB parts.

photo of tall bikeThe timing chain off my tandem was used as a donor, and ran straight from the top BB to the rear wheel. This worked, and I didn't need to bend anything to make it go, leaving the BMX rear triangle as it was. This means I could have installed a BB, pedals and seat to make this a slightly unusual tandem if I wanted to. It would have used a single chain running in a triangular path, but that would have worked I think. But I don't trust the strength of this bike enough to try it. I also only have one seat, the large donor frame lacked one so I just sleeved up the BMX one and used that.

A quick paint on Thursday night and it was all ready to go. I rode the bike to Critical Mass straight from the workshop, without having worked out how to mount the bike except by using a post or wall. But on arrival I used a grassy area to teach myself how to do it. It's basically the ordinary- style mount : push the bike, step up, step onto the pedal, and go. In my case I can hold the handlebars from the ground so it's reasonably easy. I put my inside foot onto the horizontal tube, scoot along, then step onto the near side pedal with my outside foot. And away! Excess dignity can be recovered later ;-)

Originally only the black tubing was in place, and the bike was a little scary to ride. The 27" frame was not strong enough to survive, so I added a top tube to it. Then the brazing holding the chain tube (the long one) to the top BB broke, making for an unnerving ride home. There were still three tubes brazed to it, so it was rideable. Kind of. I added two bits of galvanized square tube along the green line to strengthen that, and hopefully give it a bit more torsional rigidity. That seems to have worked so far.

photo of tall bikeI rode to work on it most days for a month, as well as using it as day to day transport. It's great in traffic, people seem to assume I'm there to entertain them, so they don't hassle me. In the CBD especially it's great to be able to see over cars, and having a very narrow footprint below roof height it can go through very narrow gaps. You just need to keep an eye out for unexpected stops, as they can be tricky. But at traffic lights there's always a pole to lean on rather than dismounting.

I fell off a couple of times, but it happens so slowly that I just jumped down and caught the bike. The pedal is only about 1m off the ground at the bottom of the stroke so it's not too bad. And by pure coincidence the bike is about 5cm lower than a standard doorway, so I could carry it into work without too much hassle.

Tanya riding the tall bike At RTS 9 a heap of people rode it, apparently without too much hassle. And again at the CANC picnic most people were able to ride it. Getting on and off was a little more tricky. Especially for those who can't get both hands on the handlebars while standing on the ground.

Tall bike as Christmas treeFor Christmas Mass I dressed it up as a Christmas tree and rode it like that. It was hot (outside was about 35°, inside add 5° or so) and a little windy. The tree caught the wind very well. As well, getting on and off was very hard work. Dismounting involved jumping down into a small gap between the bamboo and the bike, but getting back up I caught my knee every time on a cross- brace. I couldn't pedal to start, so I needed a downhill slope which made it all a bit fraught. I don't think I'll do that again.

I've now sold the bike to another CMass rider, so it will be interesting to see how he goes.

Of course, now that I no longer have the tall bike (or in fact, a bike at all) I need something to commute on... Son of Tall Bike! The plan is to make a recumbent if I can and see how that goes. Sketch plans show a few ideas.

the new plans

1 is just a slightly better version of the original with a little bigger cargo space. Then the tandem version 6, which can be higher because it could be mounted solo on the low seat, then I could climb to the high seat once I was moving (provided I can reach the top handlebars while standing on the lower pedals). The recumbent versions are more interesting, USS would let me go higher in theory, but I'm not sure of the transition from scooter mode to getting on the seat. Or back to the ground. Hmm. 5 is the compromise idea, basically just an ASS bike with a bit more seat height than usual.

Email me with ideas.