Step 7: Fabrication - Frame Welding

At this point, you are ready to weld the bikes together. I went over to my neighbor's work shop for this step. His knowledge of welding and metal fabrication really helped me do things right the first time.

We set the two bikes up in the jig and to be completely sure everything was square we took a long straight piece of scrap steel and clamped it to each bottom bracket. Doing this ensured that once the cranks and chains were on, they would be parallel and inline with each other.

Then we welded the rear forks to the front seat stays. In between was a thin steel piece that I cut to size to obtain more welding surface. The location of this union was almost exactly where the old rear brake mount was. Only after this first weld did we proceed to cut the rear end off of the front bike. If we would have cut the bike up before welding, it might have warped due to the excessive heat introduced by the welding. 

Next we measured and cut a sturdy piece of schedule 80 pipe to span the bottom brackets. It took a fair amount of grinding and refitting to get it just right. Once we were happy with its fit, we welded it into place. My neighbor actually came up with the brilliant design to use the chain stays and their natural bends to join the seat stays and the bottom bracket support. The two chain stays were welded together resembling a "Y" and were large enough to slide right over the seat stays which added to the strength and allowed us to adjust the height before we welded it to the bottom bracket span.

Once we finished welding the frames together, I ground down the welds and used some metal filler paste to smooth it all out. Reminder: it's a good idea to ensure everything is square before each weld to avoid a misalignment.
<p>Great project, thorough I'ble. Your creation is a thing of beauty.</p><p>I take pause with the brake controls. The front and rear brakes have very different effect on the braking, and if either is applied too hard they will make the bike unstable in very different ways. If the lead rider sees a hazard s(he) might need full braking power, which one does not get with control over only one brake set. For sure, both riders need to know exactly what the effect of their brake is on the bike. And it would be good for emergencies if they have &quot;brake now&quot; word, such as &quot;brake!&quot; I am an avid cyclist, but have never ridden a &quot;bicycle built for two&quot;. I would suppose the tandem riders have the braking thing all figured out, and I suggest heartily that you spend some surfing time on tandem sites and forums to learn about this and other SAFETY ISSUES concerning tandems. Also, are the brakes good enough to stop the weight of two people.</p><p>Another concern I have is the wheels and tires. If you can find a manufacturer for the wheels, I would consult them regarding the weight restriction of the wheels. Likewise tires. If you don't know the mfr of the wheels, I would recommend taking the bike to a good bike shop, preferably one that does tandems and get advice on whether the wheels and brakes are sufficient for two people. Or probably the tandem forums could help you with this. </p><p>Can't stress safety enough when it comes to cycling.</p>
With a quick glance at that final picture, I would have never suspecting that the tandem was a one time 2 different bikes. Very nice. I also like the way you split the braking responsibilities so that the driver controls the front brake and the passenger controls the rear - an easy solution to what I suspect was an area of contention.
That's a good point. Because I used all of the original parts (including the brakes and cables) that just kinda how it worked out and then afterwards I realized that it was a benefit that both riders had the option to brake.
Lovely job, impressive.<br>I wonder at the wisdom of sharing the braking - consider this: you both see a hazard, for example a car pulling out, one of you decides to accelerate out of trouble whilst the other decides that braking is the thing to do...
This is actually how many tandems handle braking duties. Usually the person in front handles the control of the bike, and the person in back pedals for their life.
Yes, I'm in the middle of rebuilding an old tandem. It has three brakes: the two usual rim brakes, plus a rear hub brake that is controlled by a thumb lever that can be locked on to act as a 'drag' brake for descending. I put all the controls on the front handlebars.<br>Photos here.<br>https://picasaweb.google.com/110336619050074124965/Tandem<br><br>
Интересная статья! Я бы с удовольствием попробовал прокатиться на таком велосипеде! <br>Я на своем блоге тоже публикую много чего интересного! <br>http://dmitrypetlekha.ru/
The final product looks phenomenal, I'd love to hop on for a ride. If those rear hubs still worked (They look like 3 speeds, if I'm not mistaken) or you could cobble together one working one from them, they would provide some extra help going up steep hills (provided the hub survived the stress of two people pedaling).<br><br>As for the decals, I've had my best success masking anything in general by pulling the masking off very soon after painting (the trick being to remove the mask while the paint is still wet, but after it has set). That way, you can consistently get clean lines. With dark colors, this can definitely be tricky, balancing the cleanliness of the mask and thoroughly coating the other color.<br><br>Again, great job, looks fun to ride on a lazy day.
just add two jack shafts and motors and youll be all done<br>
Great instructible. The wife has been wanting a tandem bike and I choke everytime I see the $1,000 + price tags of tandem bikes in the bike shops. My son has a nice shop and all the tools needed to do this.
I am not fond of bicycles, not to speak of tandem bikes, but I must say I find your project very well done AND beautiful !!!&hellip;<br>As a matter of fact this is what caught my eye at first : I find it so nicely designed that I feel you should know &hellip;&nbsp;<br>BRAVO !!!!&hellip;
Thank you very much. The goal was to inspire!
Thanks so much. &nbsp;I've always wanted to do this.<br> <br> One hint on the degreaser, I've found &nbsp;that waterless hand cleaner made for cleaning your greasy hands will also strip the grease off nearly anything. &nbsp;I've cleaned 40 year old bell housings back to nearly new using it. &nbsp;On the tough parts I'll use a round parts cleaner brush but that's about it. &nbsp;The nice part is that you can easily contain the sludge that comes off and that makes it easier to dispose of properly.<br> <br> Start by chiseling off the really built up crud and once it gets down to a reasonable thickness ( like how dirty your hands get working on an old car or truck) then apply the degreaser. &nbsp;Using the brush, work it into the crud and then you can either wipe the part clean or you could even wash it off with water.<br> Extra Bonus? &nbsp;Smells about a quarter as bad as using solvents. &nbsp;No serious solvents to remove the original paint either. &nbsp;It's usually less expensive and when done you can use the left over cleaner on your hands instead of having a can sitting around waiting to leak.<br> <br> Thanks again for the smarts.
I'll definitely have to try that out. Thanks for the tip.
A very nicely done project and a good instructable. Anyone attempting to build their own tandem should check out Sheldon Brown's website. He created several of these one junk bike plus one junk bike equals a tandem projects and wrote about his efforts and included tips &amp; links for homebuilders.
Absolutely. That's a great resource for just about everything dealing with bikes.
This is exactly what a good instructable should include... Nice intro, clear explanations, great pics and produces something outrageously awesome at the end of it!!<br><br>This has made me feel happy :-)<br>
Nice bike. Jealous.
Great Instructable and a beautiful bike!

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Bio: I'm an engineer who loves to solve problems by creating new products or finding useful ways to improve existing products. I like working in ... More »
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