Strategy for Joining Two Bicycles

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I miss the days when magazines like Popular Mechanics had all sorts of DIY projects for making an...

Intro: Strategy for Joining Two Bicycles

This Instructable grew out of a response to a question by janmcevoy, who is contemplating joining two bicycles side-by-side for more riding stability when bringing home groceries by bicycle. It is really for her, but others may view and comment.

Shown is my bicycle on the left and my wife's bicycle on the right. If I were pairing two bicycles, I would pick two that are more similar, and would probably not use one with drop handlebars.

Step 1: Keep the Bikes Next to One Another

Struts or braces can be used to pair two bikes in a side-by-side configuration. The green lines represent the location of bracing to keep the two bikes abreast of one another so one does not lead or lag behind the other. The bracing together with the chain stay forms a triangle, which is very rigid and a basic component of structural engineering.

If two bikes are to be paired like this, the bracing cannot interfere with the normal movement of the pedals, the feet, and the legs. This diagram assumes the rider will ride from the bike on the left. The bracing could be flipped if the rider were to be on the right side bike.

I would remove the crank and the chain on the bike not ridden. Not only does this lighten the bike, but it also offers more places to connect things.

Step 2: Another View

This provides another view of the lateral bracing to keep the bikes abreast.

Step 3: Tie the Front Together

The front of both bikes will need to be tied together. The yellow line shows approximately where the fronts of the bikes could be joined to keep the front separation the same as that at the rear.

Step 4: Vertical Stability

The bikes need to be stable vertically as well as laterally. The green lateral brace from earlier steps is not shown in this view so it is possible to concentrate on the structure and the location of the vertical bracing. It is in an "X" pattern. It attaches below the seats and at the rear of the chain stays. Where the members of the "X" cross one another, they are fastened together to make two rigid triangles.

Step 5: Link the Steering

The handlebar stems on both bikes could be linked by means of an extension and a connecting tie rod similar to the design used on an automobile. See the blue lines. The handlebar on the bike not ridden could be removed.

Step 6: Most of Us Do Not Weld

Because most of us do not have a welder, and perhaps no welding skills, "U" bolt clamps can be used to secure the braces to the bicycles. "U" bolts come in many sizes according to each need.

Step 7: Using the "U" Bolts

Some places it may be possible to drill holes through materials used for making the braces and then insert the "U" bolts and tighten them down. In other places, the brace materials may not clear the spokes of the wheel adequately. For those locations, a steel plate with extra holes could be bolted to the end of a brace member and then clamped to a portion of the bicycle frame. The black oval represents the cross section of a frame member on the bicycle. The tan piece could be a wood 2 x 2. It would be strong enough and is very inexpensive. The black circles are holes for bolts. Angle iron could also be used for the braces. It all depends on what you have available and how much you want to pay.

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    28 Discussions

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    BibleBabe

    8 months ago

    I am impressed by this! My question is, I have two adult tricycles, and I would like to join them together so that my adult son with special needs could ride with me, and I can control the steering. I have already developed a few idea from your post, do you have any other advice to offer? Thank you in advance.

    1 reply
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    Phil BBibleBabe

    Reply 8 months ago

    Dear Bible...,

    In general, I think I would want to remove the inner two wheels and make one fixed rear axle between the two riders. That would probably involve some welding. (People who have welders are usually eager to find something to weld. If you can find a friend who welds well enough, he or she will probably be willing to help. Bicycle frames can be tricky to weld because the tubes are thin. Some prefer to braze because temperatures are lower and it is more like soldering.) I would probably yoke the headsets together at the front of the bikes. A fixed set of handlebars would give your son something to hold, but only your handlebars would move the steering. Both front wheels would be linked together so any steering movement you added would move both front wheels in unison.

    I have not examined a tricycle up close to know what problems might lurk in the deltas. I wish you well.

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    Diozark

    2 years ago

    Not a Bad Idea, I am going to attempt to build a recumbent style
    quad, using a Captains Chair I bought that doesn't fit in the van, I am
    going to let ford repo, 2015 piece o' crap. Just purchased two 20" Fat
    tire mongoose bikes from walmart, 28 good reviews The Challenge, Join
    the two bikes together using Electrical Aluminum Rigid, and at the same
    time use that pipe as a platform to mount the seat, I am considering
    using the Inside Pedals from each crank to pedal the contraption, and
    build a steering linkage to turn the front wheels.

    If anyone has an Idea on How to Join the Two Cranks into one, Let me Know !!

    Could be as simple as a couple of rod couplings and some rod, Locktite, and some jam nuts or Piece of Crank shaft, Pipe for a trike and move one crank to the center and bearing in the housing where the cranksets normally go ?

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    zymurgic

    5 years ago on Step 7

    Have you actually tried this? I would say that given that steering a bicycle is more about weight shifting than actually turning the steering column that linked parallelograms (as seen on some three-wheel motor scooters) would be better than trying to make a rigid rectangle.

    4 replies
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    Markv10zymurgic

    Reply 3 years ago on Introduction

    Someone in Bristol has apparently done this, but I haven't found any more info yet. See at the start of this video: https://youtu.be/QtGEby4ORGM

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    firewurxzymurgic

    Reply 3 years ago on Introduction

    Actually, when you connect 2 bikes side by side, you get the exact same scenario as your car. The only reason leaning comes into play on a bicycle is because you are balancing on 2 wheels.

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    jtx86zymurgic

    Reply 4 years ago on Introduction

    It's a faith-based instructible. You just have to take the author's word for it.

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    Phil Bzymurgic

    Reply 5 years ago on Step 7

    No, I have not tried it. I did this as a suggestion for the lady who wanted something like this.

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    great idea.
    i intend to join two identical dumpster BMX bikes with three transverse steel tubing rods secured by 12 "u" bolts. steering : i thought to simply drill each handle bars top at near centre and join then with a light rod. the entire arrangement will be a bit unwieldy but will provide a means for a pal to cycle with his spina bifida son

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    Phil Bjackjackboom

    Reply 6 years ago on Introduction

    Take a look at this Instructable. It will take you to all back issues of Popular Mechanics and Popular Science on-line. You can read those magazines to your heart's content.

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    teodoropires

    7 years ago on Introduction

    Thanks for your time Phil B, very nice instructable!
    I will start to build it right now.

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    Dan Marshall

    8 years ago on Introduction

    Another alternative for joining two bicycles into a Tandem Equivalent is available at: http://TinyUrl.com/TandemEquivalent 

    This solution would not work for the expressed purpose of carrying groceries, but it is good for two people who want to cycle together.  One big advantage is that it's easy to carry the two bikes and the tandem equivalent on a normal car bike rack.

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    clutz

    8 years ago on Introduction

    I have been thinking along this line also but for two riders.  I know a few people with disabillities who ride trikes in their neighborhood but aren't able to access the beautiful trails we have around here because their endurance limits their range and their trikes aren't transportable except with a truck or very expensive rack.  This is also a problem for people with traditional tandems.  By combining two normal size bikes and making them able to be seperated you can have the stability of four wheels and also allow  a stronger rider to assist a weaker friend while enjoying a change of scenery.  In my area (Seattle) the buses also have bike racks and routes connect to many trails.  It also gives you the opportunity to pick up a friend who's willing to ride but doesn't own a bike or lives/works in high theft area.  Sorry I'm rambling but anyhow I found two commercial options.  They are a little pricey but not everyone can figure this out on their own.  You can also just take a look for ideas.

    http://www.thegrannybike.com/  or

    http://gandydirect.com/products/pedal-partner-kit/

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    Lokisgodhi

    8 years ago on Introduction

    It seems to me that removing the fork off the second bicycle and using it like a sidecar would solve steering geometry problems. 

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    Phil BLokisgodhi

    Reply 8 years ago on Introduction

    That would be fine, as long as very little weight was placed toward the front of the second bicycle.  I think steering geometry problems under general use will be less than some anticipate.

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    panhead55

    9 years ago on Introduction

    In reference to jtobako's concern as to the cornering... this problem can be overcome by using 'Ackerman' steering. Basically, the tie-rod arms are attached at an angle so they both point directly towards the rear axle. This will allow the inner wheel to turn at a slightly tighter radius than the outer, thus eliminating the 'scuffing' problem. To get a better understanding, just take a look at any go-kart or riding mower.

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    parisbabe

    9 years ago on Introduction

    another cool instructable would be an attachment you could use for riding with a dog running along side