Still working on ID, starting thread for an old tandem

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Jun 6, 2023
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I'll post my additional pics here, and hopefully find out where to look for the parts I need. All told, the bike is pretty complete. I looked at the old rusty chain today and it appears to be a skiptooth that would wrap socket to socket on the drivers side. It isn't completely frozen so I'm optimistic about cleaning it up (probably starting with electrolysis). The hubs aren't frozen, so tires and tubes will probably get it moving as a rear drive/front steer. My biggest issue as far as parts, is the front crank passenger side pedal arm; it's nowhere to be found. The steering rods are a mess, I don't know if I should just try to thread some steel rod or what.

ID'ing it will be helpful, but if I can't, were bikes of this era (whatever it may be) fairly compatible for pedal arms? It has a triangular-shape fitting to hold the pedal in place.


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Jul 30, 2013
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Whoa! That looks like block chain to me, which is much, much older and rare. Compare what you have to the image below. Traditional skip-tooth has rollers arranged in pairs--block chain has no rollers.

block chain.jpg

Either way, that Monark wheelset, while vintage itself, is much younger than the rest of the bike, I'd say. I didn't realize that one crank was damaged. It's possible that neither are original to the bike. The rear-steer mechanism is intriguing and I don't think would be too difficult to get functioning.

My recommendation is to not discard any item you remove from the bike, regardless of its apparent condition, until the rebuild process is complete. With a project that old, you never know what you might need and can't find.
Sep 17, 2013
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The middle of the Upper Peninsula of Michigan
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Here is one of my block chains.

Yours isn’t a block chain. Clean your chain by putting it in a jar of acetone and shake it for 5 minutes. Pour boiling water on it. Put in a jar of simple green and shake it for 5 minutes and pour boiling water on it. Cover it with Evaporust and watch it closely. Never, never use any acid on an old skip tooth chain, the steel is soft and pours and you will end out with a tank of pins, plates and rollers that have eaten striations in the softer part of the steel. As a final treatment sit around and scrub each link with a penetrating oil and a small brass brush, flexing the stuck links until the oil works in and frees them up. Clean it with a solvent and use bicycle chain oil. The chain above was basically a solid rusted rod and came out nice. On a bike this old nothing new or recent fits, except the pedal threads. Unless you have all the original parts It will be a nightmare to make it original. Missing original pedal replacement this old will cost as much as a new bike. The more original parts you have the better. If the nut from the original seat post clamp is missing, no modern nut will fit the thread size or angle. Same with the headset, it may be one inch but a one inch set won’t thread on. If you find an original crank arm that won’t fit after you clean it up. The nickel plating is part of the tolerance and it will be loose. A more modern, even skip tooth, crank and parts might fit the bottom bracket. Your rear track ends are worn out and will need to be replaced or repaired. You need to be able to weld to fix them or braze in new ones.
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