[funetical]

I have a couple of bike frames sitting here at the house and I was wondering if anybody had tried to extend a frame into a tandem by merging two or more frames together? I think it's either build a tandem or a tall bike. I think the tall bike would be easy, I just won't have a use for it not needing attention and all.

[HandsomeRyan]

This is not entirely uncommon. I think the best writeup about it is by the late great Sheldon Brown...

Home-Built Tandem Bicycles

[Industry_Hack]

Building one at home sounds like fun. I contacted a frame builder that specialized in titanium, gave them my specs (17/15, disc mounts, 6 S&S couplers, etc.) and waited for a CAD drawing. Made some changes, finally approved drawing number three. Flew from Australia to the US with the family, made a trip to the wheel builder, ATC Racing, and Performance Bike Shop. Also ordered a bunch of stuff from that Nutt at MTB Tandems, Alex. After about six months of planning and collecting parts, along with about AU$8k, I had a really sweet MTB tandem. And no, that did not include airfare. The bike shop I worked at did the math, and figured I saved about AU$4k doing it myself.

Your idea sounds more practical.

[adlondon]

I looked into this process for a long time. This link
brilliantly simple tandem bike
was the simplest and cheapest way I found. It's not a traditional tandem by any means, as it has 3 wheels and is basically two working bikes put together. However, I thought about going the route you suggested and came across these plans How to build a tandem. I have no experience in welding, let alone access to a welder, so I decided to build the first one with three wheels. I bought an older Trek from goodwill, and as I was about to get started, came across a Huffy Savannah Tandem Cruiser on craigslist for $100. They run about $250-$300 new and are fairly low maintenance. I ended up getting the one of craigslist, and have been really happy with it. That being said, I would much rather have invested the time into welding two frames, especially because you can be proud of the finished product knowing that you built it.

[IanHighfield]

funetical, do something different like welding the two bikes side-by-side. Make it fairly narrow to be somewhat practical. It's been done, I'm sure, but I think it would be even cooler than an inline tandem and it might be easier to make too. Put a bunch of cross tubing pieces and X braces attached to whatever part of the bikes you think appropriate or do a Google search and find out how someone else attached it.

I've had a sidecar ride in a sidecar bicycle. That was a trip. This tandem bike could be similar.