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Picture of brilliantly simple tandem bike
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
-chain breaker
-extra chain
-electric drill
-bolts/ nuts
-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)
-allen keys
-basic bike tools
-probably some other stuff I can't remember right now.

Step 2: Wheelses

Picture of wheelses
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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

Picture of rear bike
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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

Picture of 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

Picture of finishing touches
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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

Picture of gearses and brakeses
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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!

Picture of 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.
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rickharris3 years ago
There is no reason not to keep the back wheel and have 2 separate drive systems .
msspurlock7 years ago
I love this. It really is brilliantly simple. Now can you start work on a tandem that's side-by-side? I want to put an electric motor on it. Oh, and a penny-farthing conversion. That'd be cool. I don't ask much, do I? :-)
Of course, if it's side by side then it's not in tandem. But for a realization of that concept, see this.
Look what I dug up in the old photos box, from the late 80's. After a benefit ride, Aramis and Clinique, two Estee Lauder brands, gave these away as Drawing prizes, Hope they show.
sideXside_Tandem_winners.jpgsideXside_Tandem_Riders.jpg
That's pretty ingenious in itself. Similar to the buddy configuration, but less geared to filming. Lately what I've been wishing for in my space-challenged life, is a tandem add-on, kind of like the one in this article, that's easily separable from the whole. I know they make the Third Wheel, but that's somebody leeching off the pedaller. I have a design in my head, but it would really be slow, since it involves a modified crankset. That also violates the rule of not requiring a modified mother bike.
Here you go.. just published my.Side by Side Bicycle instructable.
sidebyside.jpg
LOL! Yeah, I was searching for the right term. Then I thought, to be that technical, is a tandem cycle, usually with three or four wheels, even a bike or bicycle? "Buddy bike" does kind of say it, I suppose. I was picturing more of a four wheel configuration, but this is intriguing, too.
john33474 years ago
"Back in the day" I used to weld a washer onto the dropouts and spread the fork blades and slide one fork over the rear wheel of another bicycle and make no additional modifications. This way, the bicycle would bend in the middle in turns and not require 40 acres and skidding the tires through turns. The fork would quickly work its way out of the axle of the front bicycle without the 360 degree retention provided by the washer welded to the fork dropout. The chain that is connecting the two bicycles together in this example is completely unnecessary. It is not only not necessary to prevent the rear fork from pivoting in turns, but quite undesirable. both forks should be able to pivot.

As another poster here discusses, I used to string 3 or 4 bicycles together by this method. I never tried more than 4.

FYI: "Tandem" refers to the arrangement of one in front of another; not to quantity. Mother duck and all her little ducklings following along behind her are "in tandem".
Nkevin90 (author)  john33473 years ago
True; I know your comment is old and I hadn't really ever gotten around to replying to it, but my goal was to make a connected-drive tandem, as most real tandems are. It did take a lot more effort to set this particular version up for something that turns less efficiently than what you described, but this had more of a genuine tandem feel (minus that third wheel) than simply stretching out the fork on a beater bike and attaching it to another.

At any rate, if I build another one, it probably will have independent drivetrains!
grannyjones3 years ago
My brothers did this 50 years ago.
We laughed so hard!
alexpuffs4 years ago
Hey !
It's a very nice idea !
I'll try to make one as soon as possible,
congratulations!
O-Budd-14 years ago
If I may?

It steers like a truck because it can't flex around the middle wheel.

Back in the middle of the last century (ok, I'm an old coot ), we used to chain as many as 15 bikes together by hooking the fork of one over the axle of the bike in front, usually for parades. Watching them snake thru the floats was wild as all the riders usually dressed up as clowns.

Each bike kept it's own chain drive and coaster brake (pre-ten-speed era), but the lead guy decided where you went ... and no arguing about it.

Take the bolts out, disconnect the rear bike drive from the front bike and you'll find it works a lot better.

Budd
zogworth5 years ago
I just thought I should let you know, a side by side is usually known as a sociable, because you can chat :) 
Check out http:/TinyURL.com/TandemEquivalentTinyURL.com/TandemEquivalent
It shows another solution to the same problem which is arguably simpler and more manuverable.
The reason that you have to make really wide turns, cross streets by walking the bike, never take turns too quickly, and the whole bike is difficult to turn, is the fact that you've bolted the head tube, preventing the bike frame from pivoting in a turn. However, a bike with three (in-line) wheels MUST have a pivot point to turn properly.
While (I agree) this would be catastrophic for the drive train that you've built, it would work fine if each bike were to keep it’s own (independent) drive train.
What I mean is, why not just connect the front fork of the rear bike, to the rear axle of the front bike, and be done?..
And best of all, this way you wouldn't need to splice a super-long chain together, or deal with complications of trying to share the drive train.
Nkevin90 (author)  jalbert_designer6 years ago
oh yeah, of course I've thought of that, but it's not as tandem-esque without the synchronized drivetrain ; ) I'm not sure how the rear wheel would fasten on though without a super oversized axle though, because the fact that the rear is a front hub with a rear axle gives you enough play to fasten them together. it'd be interesting to see how a pivot bike would work though. turning would probably be wicked confusing for the stoker.
Old Man Mountain uses super long axles with their axle-mounted racks. Might be able to get some from them and perhaps use some ideas from their mounting.
Megawatt6 years ago
does it work?
SirJoey6 years ago
Pretty funny, & definitely original! Kudos! :)
Hey Kevin I didn't know you were a member of instructables though I kinda thought you were. It's Vincent from South. You know the kid who doesn't know what to cut on the frame.
this must confuse the heck out of onlookers!
Nkevin90 (author)  technodude926 years ago
oh, it does. one kid said to me "NICE BIKE!", and I say "thanks," because it is, and all borat-style or something, he comes back with "NOT!" I couldn't help but laugh. he had to be jealous.
yes, after BORAT, the world will never be the same.
I'm sure there's a way to make it bend in the middle, you just would have to have two different drivetrains. Maybe you would need to change the angle on the rear steering tube. After all, these things work fine:
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Kiteman7 years ago
I'll second uldics' comments about the too-close pictures, and isn't the join between the bikes a weak-point? Would it not be better to add some sort of cross-bracing between the two bikes? Still the pictures in steps 6 & 7 are great - it takes a double-look to be sure how many bikes you are looking at.
PKM Kiteman7 years ago
I think the advantage this way is that the bike can pivot about the... transverse axis? at the middle wheel axle, which is necessary as it has three wheels. If the frame was completely rigid imagine what would happen when you hit a speed bump. If you had some pretty serious suspension on the front fork and back frame it might not be as necessary. I'd like to see what would happen to the handling if you didn't lock the back bike's forks...
Visitor PKM7 years ago
If the middle fork was not locked, then the bikes would lean in different angles when cornering. Because the middle fork is leaning backwards, the front bike would lean more in the corner and rear bike would lean less. Handling while cornering would be tricky. All in all, this design is on a dead end track. A neat way to spend a day tinkering, but it will never produce a properly working bike. I mean trike.
Kiteman PKM7 years ago
>doh<

I was just thinking - if both riders leaned different amounts, there'd be some serious twisting stresses on that joint.

I'll never make one, but I do like the look of it.

I wonder if this would work as a modular thing - each bike powers its own back wheel, but you can fix loads together. Imagine the chaos that could be caused on one of those reclaim the streets events. Everybody arrives, takes off their front wheel and they build one single vehicle, three blocks long...

It would be the world's longest, narrowest flashmob.
Nkevin90 (author)  Kiteman7 years ago
yeah, I was thinking about that too, and in that case, you wouldn't have to make another chain. you're right, and the thing does make some awful creaking noises, but once you get the thing up to speed, those forces seem to dissipate.
Nkevin90 (author)  PKM7 years ago
well if you're an awesome rider, go completely straight and you're fine. carve it off an inch or two to the left, the chain will stretch beyond your wildest dreams and most likely explode. go off to the right, and it'll probably fall off
bumpus PKM7 years ago
Yes that would be the "Transverse Axis" why are you testing my tenth grade math skills?
Nkevin90 (author)  Kiteman7 years ago
probably wouldn't hurt, but it's been on a few rides so far, and no problems to date. the flexing actually helps with turning a little bit.
trebuchet037 years ago
Excellent execution - I've had a very similar idea on the back burner for some time now :) More along the lines of independent drive trains though :)
shooby7 years ago
Good idea. That shifter looks like a plastic artichoke.
Nkevin90 (author)  shooby7 years ago
uhhh, of course : )
really cool, although i don't know if i'd be game enough to ride it! i do have a couple of spare bikes in the shed though.... to prevent having to bend forks, have you considered staggering them? so have each side of the fork on the left (or right) of its corresponding rear dropout (assuming the same width of fork and rear dropout). I'll try to illustrate: | | ||--|| | | so the top two "|" are the rear dropout (looking down over the axle) and the bottom two are the fork, the "-" is the axle. on one side the fork will be on the outside, on the other the dropout will be on the outside :) don't know if it would foul the chain though
Nkevin90 (author)  TheScientist7 years ago
huh, that actually sounds like a pretty decent idea- I'll have to get back to you on it and tell you if it works. it's not bad to ride, I promise. or, uh, as long as I'm the captain. ha haa.
craptastic the diagram didn't workk in the post, but did in the preview. hopefully you can see what i mean!
Sweeet...I was thinking of pretty much the same idea but gave up when the forks didn't fit over the back dropouts, I didn't want to have to bend them. It looks great though, good job
Nkevin90 (author)  The Rocketizer7 years ago
yeah, that was a super last minute idea, and of course, those were some really crappy forks.
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