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Tall Bike Too : Even Bigger

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Moz riding the tall bike
Tall Bike 2, with some 4m long steel tubes on the load platform.
Bike completed: October 2001          More tall bikes on the net: tallbike.net
Finished bike, with dimensions
Finished bike, with dimensions
This is a rough plan with critical dimensions and angles on it. Taken from the actual bike, then the drawing made by assembling rectangles of the correct size over this photo. Download the drawings in TCW and DXF format zipped in Tall Bike 2 There's a layer with the picture in it there too, which blows the file size out a bit but makes it more obvious how it goes together.
The plan
The sketch plan
I started sketching design ideas for tall bike two a long time ago - shortly after completing tall bike one, in fact. Some of the early ideas are on the tall bike one page . After my long bike was stolen I decided to build this bike fairly quickly, to get something to ride. I sketched a little more, and decided on a few more constraints: it needed to be slightly taller (of course), the handlebars and seat need to slide down a long way, so I can fit it into a van (and through doorways), and it needed a decent rack, ideally capable of taking a Nally bin. It should also look cleaner than tall bike one.
son of tall bike
son of tall bike
To get a rigid frame I used oversize tubing - 50mm diameter, 1.2mm wall thickness. This is the first real bit of the new frame, sitting on tall bike one to show the relative sizing. The bottom tube really will sit that high off the ground. The wheelbase should end up a little shorter, but the seat will be further back, and higher up. Most of the building was done like this - hang new frame on Tall Bike, compare the two, and cut to suit.
frame 1
frame 1
Same bit. With conventional seat and head angles and the nally bin sized gap between seat tube and headset it's a little long, but not impossibly so. The length is necessary to get stability on hills, and the angles make it a little more rideable. Tall bike one also suffers horrible steering flop, so it can't be ridden hands off or wheeled without a hand on the bars, again hopefully fixed here.
frame 2
frame 2
Adding the top tube. I decided to make the two horizontal tubes parallel just because it looks nicer. Getting the frame flat was easier than I expected, I just laid it on the floor and used a level and wedges to prop it up. Then I mitered the front end once it was in place, using a spare tube through the headset to get the length right. It ended up about 5mm short, but the bike still goes together.
seatpost
seatpost
Rather than the traditional idea of a seat post fitting directly into the tube I sleeved it down to fit a bit of stainless steel pipe I found. I slit the top of the pipe and welded in the top off a spare seatpost so that I can fit most saddles.
rear fork
rear fork
I built the rear fork separately then brazed it in place as a unit. Our new toy in the workshop makes this stuff a lot easier - an oversize Dremel type tool with a filing bit in it, so all the tube mitering can be done incredibly fast.
brazing on the rear fork
brazing on the rear fork
Getting the rear fork to sit in place so I could braze it was... entertaining. I wanted it slightly back of straight along the chainstay, but couldn't get the frame to the right angle that it could sit vertically. Hence the vice grips attached to the top as a balance weight. Note that as always I'm using a magnetic level to get everything square, since I can't do it by eye (experience showed me that). This is (I think) the straightest bike I've built so far.
attaching dropouts
attaching dropouts
Ken's dropout jig in place to put my rear dropouts in place. There's a bit of 10mm threaded rod across the end of that with some nuts so you can attach the dropouts to it at the right spacing and angle, then wiggle them into the right place on the bike. By careful design the desired spacing meant they sat neatly in the ends of the fork tubes.
dropout jig
dropout jig
The jig again.
dropout jig
dropout jig
Get the idea?
rear dropouts in place
rear dropouts in place
It turns out that having the dropout slots vertical isn't quite right, due to my upward running chain. I don't get quite enough chain wrap at the bottom, so too much tension just makes the chain slip. More playing with derailleur angles and chain lengths might fix it. But this way meant it was really easy to attach the dropouts, where I should have cut the tubes at an angle and played a little more. At the time I was concerned that the wheel might pull out with the short dropout slot running horizontally.
rear dropouts in place
rear dropouts in place
...
bottom headset and collar for sleeve
bottom headset and collar for sleeve
The headset, showing the collar that bulks it out to take the sleeve that drops down and makes it all look like one tube, while still allowing me to use a standard headset and get at it to set it up. The collar is a couple of 15mm long rings, then the longer bit of 0.9mm wall tube to give a surface to grip onto (it's lighter this way ;-)
headsets and joining sleeve
headsets and joining sleeve
After I brazed in the top headset. Note that the sleeve cannot be removed now - it will not pull enough to the side to come out. With a little imagination you can see the slight mis- alignment of the top and bottom sections.
alignment (or not)
alignment (or not)
And this shows it explicitly. Note the ring on the top section that brings it up to size. With larger tubing the gaps between sizes are too large to give nice sleeving, so you end up doing this a lot.
headset detail
headset detail
The bottom headset setup. That's straight off a standard bike, I cut the head tube out and brazed it in here. By using a spare locknut I freed the cap nut at the top, so I could braze the steerer extension onto it. The bolt you can see locks that extension once it's screwed down so there's no danger of it coming undone while you're riding. The usefulness of that was clear during my first ride, when a loose sleeve further up dropped me off the bike immediately I tried to steer.
all done
all done
The sleeve in place.
cut steerer to length
cut steerer to length
Cutting the steerer extension to length after it was in place.
top headset detail
top headset detail
The top headset is actually just a plain bearing. Because of the need to be able to take it all apart as well as adjust the handlebar height by a metre I couldn't braze anything onto either of the tubes. So there's a little gadget that sleeves in between them and clamps both tubes, as well as holding the brake cable (found center pull canti brakes). I filled the gap with a couple of bits of PVC pipe, but will probably lathe up a bit of brass later.
front forks
front forks
Another set of shortened front forks. Most of these bits came from a donor bike that had 650c wheels, which we couldn't get new tyres for. So it became spare parts, including the front forks. This time I managed to cut them it the right place so that the cut off ends sleeved back into the fork, so I could braze them in place easily. I used an old front axle to get the spacing right, and it was remarkably straight forward. If you look closely you can see that the holes next to the brake posts are on the outside, so standard V brakes won't fit. When I find some new posts those ones will come off.
bottom bracket alignment
bottom bracket alignment
The bottom bracket went on quite late, after the rest of the frame was just about finished. To get it straight I bolted it to two square tubes, then spaced the frame up to get it centred on the BB. Much playing with levels and wedges later, it was just a matter of pouring bronze in to get it fixed in place.
bottom bracket bracing
bottom bracket bracing
My first attempt at bracing the BB. I cut those wee tubes out and used a junk bit of 50mmx1.2mm tube to brace it properly after a bit of thinking.
rear wheel setup
rear wheel setup
A trash rear wheel in place to set the bike up. That's a three speed hub with no shifter (so it's stuck in top gear), with a triple chainring to give me gears. Note that there's less than 180 degrees of chain wrap around the bottom cog. The only really valuable thing on my long bike when it was stolen was the rear wheel - 9 speed cluster and disk brake hub. So I have to wait for the replacement I've ordered before I have a proper wheel for the tall bike.
front derailleur
front derailleur
The "front" derailleur tube runs horizontally from the bottom bracket (it's amazing how all the bike terms don't work when you build a really odd bike like this). I added a vertical strut so that it wouldn't get bent if someone stood on it. It's also a convenient place to put a bike light. This shows where we drill the mounting holes in a Jaycar giant light (which don't come with bike mounting hardware). Normally the bolts hold it in place indirectly, but in this case it worked nicely.
test ride
test ride
Ken showing just how tall the bike is once it's all ready to go. Tall Bike in front, Tall Bike Two behind, with Ken on it.
comparison
comparison
Looks as though the pedal height is about 20cm higher on TBT, so once I get the courage to put the seat right up I might be 50cm higher on TBT than Tall Bike (which has a dismally short (non-adjustable) seatpost).