How to make a tandem bicycle from two bikes! no welding, no fancy tools needed other than a power drill.
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Step 1: Parts
you're going to need:
-crescent/ adjustable wrenches
-two bicycles, nothing fancy (possibly a smaller frame for the stoker if you'd like, and if you're picky and want certain cranks, go with frames with square/ taper BB's)
-crank puller (optional)
-basic bike tools
-probably some other stuff I can't remember right now.
Step 2: Wheelses
take the front wheel off of whatever you're going to make the rear bike, and just as well, dismount the front bike's rear wheel.
using a combination of wrenches and or pliers, do what you can to remove the axle from the front wheel that you just took off. we're discarding it, so make no special effort to keep it in great shape, though I highly recommend keeping the innermost washers in the best condition you possibly can.
we're also removing the rear wheel's axle, so once again, try your best to remove all the washers while keeping as much as you can in tact. a workbench clamp is very helpful in such removal, as sometimes certain sides get stuck. I do not at all recommend using a pair of plyers as a clamp, as you'll strip the threading on the axle easier than you can possibly imagine.
anyhoo, just make sure you have all the washers and nuts from both hubs aside from the ones that press against the bearings in the rear, because they'll probably be a bit of a different size.
the whole point of this step if you're handy enough and don't feel like reading, is that we're putting the rear axle in the front wheel. it's longer, and we need that extra bit of length.
I haven't tried this with a quick-release axle, though I'd be surprised if it didn't work. under the same token, why would you need one?
Step 3: Rear Bike
this doesn't necessarily need to be in any particular order, in when you do this, but on the rear bike, we're going to need to drill at least two holes through the headtube and through the steerer tube of the fork. drill holes corresponding with the size bolts you're going to use. I also wouldn't recommend smaller bolts, considering that we're going for strength here.
this drilling is going to prevent the frame of the rear bike from turning like the cargo of a semi-truck, which could be catastrophic if it happens on a left turn for the drivetrain.
MAKE SURE THAT WHEN YOU DRILL, THE FORK IS LINED UP PERFECTLY STRAIGHT WITH THE FRAME. I don't think I need to explain why. it might be easier to check this with a front wheel mounted, or if you particularly don't care about it, clamp it in a vice as I did.
Step 4: Attatchment
so you should have a front bike without a rear wheel, a rear bike without a steering set of handlebars and three rods bolted through its steerer tube. splendid.
take the rear bike and set it up with that front wheel with the rear axle, and using whatever combination of nuts you can get a hold of, make sure the fork tightens so that the dropouts of it are closest to the axle.
try to get the rear dropouts of the front bike on over the axle. now of course, it depends on what fork you're using, what your rear dropouts are like, etc, but if for some reason your fork doesn't fit with whatever configuration you're using, stretch it.
yes, if it's a steel fork, it should stretch pretty easy, as mine did; just put your foot on one leg and slowly bend it. make sure it fits over the rear dropouts, as opposed to inside of them now, and bolt that middle wheel on as tight as you possibly can!
Step 5: Finishing Touches
hopefully, like I suggested, you used a rear bike with at least a double crankset. that's vital.
let's get the chain on now. or two. or three actually.
yeah, you'll need three chains for this bike as well as a breaker. first off, fuse two chains together, and add or take out as many links as you'll need to get the chain to stretch from one set of cranks to the other. and make sure your pedals are set to where you want them just as well. you can do this using a chain breaker, which are about three bucks at your local walmart.
naturally, the holes in the second bike's headtube are going to stretch, and considering that, so is your chain on those nasty turns. a simple solution is taking an old deraileur and fastening it to the dropouts of the first bike, but only using the bottom pulley. this will tension the chain from the bottom up, as you see, and prevent it from falling off.
once you've routed your chain through the deraileur, connect the chain.
so that's one down. oh yeah, and you're going to want to fasten it to the top gear of the rear cranks.
the middle ring (I drilled out the little one because I'm anal), will work great for the drive ring, as you will, and operates on the same principle as a regular bike's drivetrain would.
just so the chain doesn't fall off, I took an old front deraileur and bolted it on as another safety precaution.
Step 6: Gearses and Brakeses
I figured I'd give the stoker something to do, (okay, realistically, gear cables don't run this long!), so I installed a shifter on the rear bike's set of handlebars which control the gears for the bike, though I found out that they honestly don't help so much anyway. ha haa.
and as far as brakes: if you want, you can install two, but they have to be controlled by the captain, because you don't want the stoker doing anything stupid. I highly recommend a front brake, and on the middle wheel, you can install a back brake for the front bike, or a front brake for the back bike.
bottom line is, even as heavy as the thing is, it works fine for me with just one brake.
and no bike shop would ever condone this, but if you, like myself, have a nicer deraileur and are lacking horizontal dropouts, get a cheap deraileur hanger and stick it in between the hardware and tighten the hell out of that wheel! it's proven to work fine, but looks pretty bad in my opinion.
Step 7: You're Done!
that's it? what?!
yep. it's that easy. just make sure everything's tight and the hand - controlled parts are properly tuned up, and it's ready for a ride!
so how do you ride it?
yeah, there are three wheels and it's pretty difficult to turn (I say it turns like a semi-truck going through the drive-through of mc donald's) but trust me, it's not that bad once you get the hang of making really wide turns.
I recommend having the captain get on first, support the bike completely and have the stoker mount themselves on the pedals, then take off with as little horizontal movement as possible. there might be some play in the rear bike's steering, as why I cut them down to size, considering that the stoker will have less leverage as a result, and it's proven to be effective.
I'd cross streets by walking the bike and never take turns too quickly. also, think about getting a higher pressure middle tire, just because the wheel has twice as much weight on it as it normally would.