Random Tandem storms Newnham 90 - Bike Magic

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Random Tandem storms Newnham 90

This one’s a classic, we couldn’t make up any dafter story for a Friday. When two BIKEmagic members sent us these pictures we had to ask for the full story and boy, are we glad we did. Here’s the story from the creators themselves;

So what’s it made of and how?

All the stuff is of dubious, yet respectable origin! The rear
frame is a Dawes kickback mtb frame, with an ovalised headtube and is riddled with cracks, most of which have been welded in it’s long career. It just happened to be that this ovalised headtube was a near-perfect press fit with the seatpost of the front frame. The rear frame is a Barracuda Slalom, with the shock removed and the stays bent together. It has a homemade bracket holding the drop-outs onto the downtube of the rear

The remaining piece of tubing has been extracted from the framework of a plasma cutter, which proved to be of similar thickness to the scaffold-like Barracuda tubing. The forks were recovered from a river in Marsh Barton, Exeter, along with the Kawasaki motorbike front wheel. The speedo isn’t, unfortunately, original equipment, and hence runs a little fast – it seems to track in Kilometres instead of miles, although the gauge
is in mph. Apart from that it worked fine. We suffered a broken speedo cable
on the 75th kilometre, however.

Both frames used are VERY second hand – i.e.: just
about everyone we know has owned them both at sometime in the past. The barracuda was obtained
as a part exchange on a deal with a university flatmate, and the Dawes
bought for a bike to lake jump into the Quay in Totnes. Unfortunately, the
only welding equipment available to us was a 300Watt Arc welder, which
proved a might powerful for the thickness of tubing provided, but we
managed. The blowholes in the tubes left from the welder are, of course,
entirely intentional and reduce weight. The forks have an
undersized 7/8inch threaded steerer, fitted, somehow with a wedge, into a 1
1/8 headtube. No play at all, until about the 50th kilometre when the
bottom cup broke up into little pieces. Steering was more of an
approximation after that moment.

Another difficulty to overcome in the
engineering of such a beast is the chain arrangement between the front-most
‘athlete’ and the rear one without the use of eccentric bottom bracket
shells and tandem-specific cranks. We were forced to run the chain between
the two chainsets on the granny rings on the right hand side. But
the chain tension was more difficult to over come without having the
chainline upset. It was entirely intentional that the gear
hanger from the, now mis-shapen, Barracuda rear triangle lined up exactly (aided by a hammer and large adjustable spanner) with the chainline. Then we could mount a rear mech, with the top jockey-wheel removed, to pull
the lower side of the chain upwards to give much needed chain tension. Neither of the
chains came off once. This method of chainline
meant that the granny-gear was eliminated so we could use only the middle
and large rings. It was also co-incidence that the two chainsets had the
same size little rings, so that the pedalling was co-ordinated. Also, the
cables had to be extended so that the front cyclist could control the
shifting. This was done with two old cables per shifter, and some electrical
connector blocks to amalgamate the lengths. Nothing slipped, and the gears
were silky smooth throughout the event. The brakes were much easier, with a
standard Magura rim brake on the rear, being controlled by the back rider,
and the front already being supplied with a 12.5 inch rotor disk brake. The
rest of the kit was whatever we could find lying around. The rear wheel was
borrowed from a trials bike, and the chains borrowed from 3 bikes in order
to combine enough length.

Did it survive?

The actual ride was surprisingly uneventful: we didn’t break down,
let alone break up. Much to everyone’s
surprise the frame stayed in one piece. The motorbike road tyres didn’t grip
off-road. We had to wind up the pre-load of the forks using large
spacers to compensate for the load of two people. The only really
problematic piece of componentry was the rear seatpost, the clamp
slipped on hard landings. We had a significant advantage
on the downhills with superior braking provided by
the exceptional front disk, the forks, and the fact
that it’s mighty difficult to go over the bars on a tandem. You tend to
bounce out of holes and over rocks. We managed to maintain our placing
(although it wasn’t a race!) by overtaking on the steep, rocky descents. We finished after a
whopping 6 hours 15 minutes, but I’m pleased to say that we came home in
front of the only other tandem present.

We did the race for fun, thinking the evening before the race that it’d be great to ride on a tandem. We made it that evening, and the race was the maiden voyage. It’s
still in one piece so look out for us in the future. It was a great day, and our thanks go out to the organisers. I hope I’ve said
everything worth saying. I’m James Hawkins, and my bro (the one on the front of the bike in the picture) is Peter, of ScottUK.


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