Columbia Twosome Tandem

[rickpaulos]

My wife bought this tandem for me for my birthday many years ago. A Columbia Twosome Tandem.

We did ride it around town a few times but it rode pretty bad and the seats were quite uncomfortable.

One day at a local Dairy Queen, I leaned over the bike, putting some pressure on the captains seat and I saw the connecting chain snap tight. WTH? Repeat, same. Upon closer examination I saw the boob tube sliding in and out of the rear bottom bracket shell. It was not welded or brazed at all. So when you ride, the bottom of the bike wants to expand but the connecting chain takes all the weight. As you know, chains that are too tight have all kinds of resistance. I pulled the crank and borrowed a friends oxy torch and brazed the joint back together. FYI, the entire frame was brass brazed originally but with a minimum amount of brass. It defintely doesn't have that fillet brazed look. On this and many other cheap American bikes, the bottom bracket starts as sheet medal with holes punched in to it for the tubes. It's bent in to a pipe shape for assembly. The seat tube, down tube, boob tube, chain stays all are inserted through those holes and brazed in place. This method of construction is cheap and easy but it doesn't provide for much stiffness or support. I touched up the paint and viola! Rode just as bad.

The brass brazing mess on the rear seat tube:

Here is a photo that shows how the tubes are inserted through the bb shell:

Later on I used the bike as an expiramental platform. I installed 2 Shimano FFS cranks from a couple of Schwinn Calientes. This gives the riders independent pedaling. By chance, the chain length was close so I didn't need to modify the tensioner much. The FFS cranks have welded on chain guards on both sides of the dual rings so the chain could not fall off. I used a couple of 10 speed chains (3/32") for the connecting chain so it would not catch on the 1/8" drive chain. It works! Each rider can coast or pedal as they want. The main draw back is no coaster brake anymore. The bike only had the whimpy front rim brake. Like I said, experimental. The tandem would need better brakes installed somehow. The rear seat stay bridge is not suitable for a caliper.

Next problem with the Columbia and many other tandems is the 'girl' design. There is much more weight on a tandem and it can cause the rear seat tube to bend forward. I had this happen on my Huffy Daisy Daisy and it was a problem on this Columbia. You can see the seat tube is bent compared to the straight edge. On my Huffy, I used an old car bumper jack to straighten it out again.

On this Columbia I discovered there is a steel plate inserted inside the seat tube. I don't know if it was factory installed or added later on.
On one of my old Huffys that didn't bend, I found a second seat post pushed all the way in for reinforcement.
You can see the one end in this photo.

And you can barely make out the top of the plate in this photo.

I decided it was time for a redo of the bike. The original red/gold paint wasn't looking very good.

I stripped all the paint of using one of these nasty devices. A roto stripper. I did have to weld the axle to the end plate when it spun loose.

FYI, the cheap chinese made versions don't hold up. The wires kept breaking off and go flying. Those wires are heavy enough that they will do damage to your eyes. Stick with the genuine USA made versions. I've since used a lap sand paper disk on my small angle grinder that works very well too. But it won't fit in tight corners like the roto stripper.

The serial number appears to decode to 1968.

Changed out the busted rivits on the chain guard which I had removed and saved during the FFS experiment.

I went for a USA theme on the repaint.

I also put some decent Schwinn cranks & rings on and some sturdy pedals. Another poor item in some of these cheap American tandems is the cranks that use slip on cones on the sprocket side of the bottom bracket. That means the bearing pressure has to hold the sprocket(s) straight. Not good. Most 1-piece cranks use threaded on cones that do hold the sprocket securely in place. The Schwinn 1-piece cranks are pretty good.

All this work and the bike still rides rather poorly. New tires would probably help. More comfy seats would help. Aluminum rims, new chains too. But I already put a lot of time in to the bike. I didn't want to spend $200 for parts only to find out they might not help.

I took the bike to a local show. Of course the Flying Merkel tribute bike won best of show.

I sold it via craigslist. (story there for a later time)

I don't miss it.

Rick

 

[user 135]

How was peddling it when the cranks were out of sync?

 

[rickpaulos]

Out of sync, ie in phase vs out of phase.

I have other stories about that.

My first Huffy tandem had two different size connecting rings on it. ie, variable phasing. I recall, the bigger ring in the front. I took it on the Midwest tandem Rally in Springfield Illinois in 1978 with another bike racer. Turns out we were one of the fastest tandems there despite being on a Huffy and most others were on quality tandems like Paramounts, Jack Taylors, even a Polliaghi tandem. I got stuck on the rear seat because the other rider was bigger. When we would ride at a normal speed, the variable phasing cause the bike to first bounce up and down when the cranks were in phase, then settle down for a few pedal revolutions, then the bike would snake side to side for a few more pedal revolutions, then settle down, then bounce up and down and so on and on and on. Other tandem riders were following us just to watch the phenomena. When we spun it out, I had to put my feet up on the frame as I had the lower gear and could not spin as fast as the other rider. This tandem had those lousy cranks that use slip on cones on the right side so it would toss the chain every now and then. I got good at reinstalling the chain while riding before we coasted to a stop.

Later on I made a franken quad by welding two matching Huffy tandems together end to end. My two Huffy Daisy Daisy tandems were not properly triangulated. It has two small tubes that flow in a wave for lateral and vertical stability. ie, not much support. Like a cantilever frame but extended back for the second rider. I continued the wave from one tandem to the other when I built the quad. End result is a fairly flexible quad. It was pretty obvious to not put all 4 cranks in phase with each other. I think that would have resulting in the bike collapsing pretty quick, probably at the fork. I've experimented with 1/8 turn phasing, each pedal stroke 1/8 turn behind the next. That way you only have 1 foot pushing at peak pedal pressure at a time. But that makes it hard to start up as someone's foot position is always in the wrong place every time. A more practical phasing is 1st & 3rd match up, 2nd & 4th at 90 degrees from 1 & 3.

There are lots of high end tandems that get set up 90 degrees out of phase. It does give you smoother pedaling and takes a lot of vertical stress off the bike, fork and wheels. It smooths out the power so you are less likely to break a chain or freewheel. It will put a different twist in the bottom of the tandem frame and it makes it a little harder to start. The captain has to be aware of where the stoker cranks are for starting and stopping and especially in crit racing. A good quality tandem can certainly handle the 90 degree phasing. A cheap tandem that has problems with 90 degree phase cranks will also have problems with in phase cranks.

For your basic low end tandems that are used for neighborhood riding, it really doesn't matter. Independent pedaling does make it easier for newbs.

There are high end free wheeling crank sets available for tandems which I can't remember the brands right now.

DaVinci makes a tandem with independent pedaling that is pretty slick. It uses a 3rd bottom bracket with 2 freewheels for the connecting chains and is equipped with 4 sprockets for even more gears.

Rick