Introduction: Iron Tandem - Bicycle/Recycle Project

About: I use reclaimed materials such as wood and metal to make a variety of unique and unusual creations, from scrap metal robots to wooden tables. I am a self-taught hobbyist and have always enjoyed making stuff an…

This instructable explains how to save two old bicycles from the grave to create one immortal tandem bicycle.  

I had always fancied building something for fun and actually dedicating a bit of time to a project rather than just the odd quick fix here and there.  With a charity bike ride looming a couple of months away it seemed like a great idea to try to build a tandem and enter it just for fun.  A few friends and I had entered the event the previous year dressed as glam rockers and it got a good response so we decided to repeat it this year.  (Hence why this tandem has a bit of a Gothic look to it!)

I had never ridden a tandem before and didn't really know what I was aiming for so I looked online at some different frame designs to gain some inspiration.  I decided that I didn't want my bike to look like two bikes - I wanted it to look like a genuine tandem frame.  I also learned that having a decent spacing between the driver and passenger was essential to ensure that the passenger could actually see some scenery and not feel too cramped on the back.  Throughout this instructable I refer to the driver as the 'captain' and the passenger as the 'admiral' because this is proper tandem lingo dontcha know!

This bike cost very little to build as most of the existing components were cleaned up and reused.  The only parts bought new were bearings, chains and cables.  The only really specialist tools I used were a bicycle chain tool (cheap) and a MIG welder (err, not so cheap)

Tools you will need:
- A pair of grips
- A pair of pliers and cutters
- Allen keys and spanners (various sizes depending on your donor bikes)
- Hammer/Mallet (for persuading stubborn bike parts to come off)
- Screwdrivers
- Sandpaper
- G-clamps or large magnets (for holding the frames together when welding)
- Angle grinder (with cutting disc and grinding disc if possible)
- Metal hole cutters (you could use a hacksaw and then file the tubing to shape but this takes a LOT of time)
- A pillar drill (a pillar drill is ideal in order to cut the angles more accurately but a similar result can be achieved using a hand drill and a jig)
- Bicycle chain tool
- A MIG welder - or gas/TIG if you have one available!
- Some wood to make up a frame jig prior to welding
- Spray paint (primer and colour)

Other things you will need:
- Some old bikes! (Free)
- Piece of mild steel tube (from scrap metal yard £10 / $17)
- Paint (£25 / $40)
- Bearings and cables (£10 / $17)
- Chains (£7 / $11 each)

Step 1: Donor Bikes and Dissembling

First things first - you are going to need some donor parts.  By using some old bikes that were destined for the bin; a) they were free and b) this project incorporates recycling in its purest form  : )  

The donor bikes were sourced for free – I found two in a skip and the other in the garden of someone’s house.  (I did ask before I took them!)  I figured that the third bike would come in handy for some extra spares should I need them.  All three were in a pretty sorry state and rust had got to most of the components.

The fun begins by unbolting everything from the old bikes.  You won’t need much in the way of specialist tools for this although a chain tool is essential for breaking the chain and will come in handy later on when the new chains are to be sized and fitted.  A crank extractor tool will also make it a lot easier when removing the crank arms from the bottom bracket but this is not essential. If you've got a wooden mallet and a good shot then hit the cranks hard and they will come off eventually.  It ain't pretty and I wouldn't advise doing this on anything other than an old bike where the frame is steel and the cranks are massively over-engineered!  Basically don’t go trying this on your carbon cranks!  : )

To remove the bottom brackets I used a pair of water pump grips to get the bearing cups out of the frame.  You need to remember that one side is a normal thread (undo by turning anti-clockwise) and the other is a reverse thread (undo by turning clockwise).  This also applies to the pedals where they bolt into the crank arms but I will go in to more detail on this later.

As you can see the bearings looked like they were due a bit of a service(!!) Due to how badly corroded they were. I scrapped them in favour of some nice shiny new ones.  I also cleaned all of the cups out with sandpaper and a wire brush so that the bearings could glide around happily in some slimy new grease.

If the brake and gear cables look in good condition (shiny metal and not frayed) then you may wish to reuse some of them if you’re doing this project on a budget.  In the interests of safety and smoother braking/gear changes I’d suggest you replace them all as they are very cheap and it means you don’t have to waste time undoing the old ones – snip, snip!

To remove the forks, undo all headset bolts and the steerer tube nut (the nut at the top of the forks where they clamp onto the handlebar stem).  You will then be left with two bearing cups in the head-tube of the frame (top and bottom).  To remove these you can either use the proper tool (boring!) or get a wide bladed screwdriver and tap them out gently with a wooden mallet ensuring that you tap equally all round the bearing cup to prevent it getting stuck at an odd angle. Also be careful not to damage the surface where the bearings sit.

Everything else will unbolt from the frame with spanners and Allen keys.  Eventually you will be left with a tray full of rusty bits, a couple of old frames and some well used wheels!

Step 2: Cutting and Grinding

Now cut off the bits you don’t want with an angle grinder and use the grinder to clean up all the sharp bits.  You want to keep the rear triangle (including seat tube) from one bike and the front triangle (incuding seat tube) from the second bike.  I chose to use the bigger frame bike at the front and the smaller one at the back as this appears to be the most common way of doing it.  Also makes sense as the larger rider will tend to be at the front.

Step 3: Frame Fabrication - Planning

Now it is time to consider how to make the frame and what dimensions/angles are to be used for the frames and new tubing.  There are lots of ideas online.  Being that they were mountain bikes in a previous life I decided to keep the bottom brackets inline with the wheel axels which also meant that the top tubes across the bike would run parallel with the floor. 

I made a jig from wood for the bottom brackets to sit in.  This was used to keep the frames in alignment but also allowed the frames to slide and pivot so that I could get the frames to sit the correct distance apart from each other and at the desired angles.  I made sure the jig was completely flat using a spirit level so that the top tubes could also be aligned using the spirit level.  There are a few things to consider at this point as different frame angles will affect the riding positions of both riders.  In my opinion the most important thing to keep in mind is the distance between the captain and pillion… you don’t want to ride with someone’s chin in your back and similarly the person behind wants to see some scenery – not your sweaty back!  : P

Once you are happy with the frame positioning it is time to cut the new tubing for the frame.  I bought a 3 metre piece of steel tube from a scrap dealer which was plenty.  To cut the ends of the tubes I used hole cutters that matched the diameter of the seat tube it was being welded to give a nice flush fit.  This will make it look neat and ensure that it is a solid join once welded.  The cutting angles can be measured easily using anything that pivots – two sticks nailed together at their ends would work if you’re desperate!  As you can see I used a set of feeler gauges.  Once you have measured the angle on your frame mock-up, you can then use this to determine the cutting angle between the drill and the tube.  I found it was difficult to start the drilling at an angle as the drill bit would slide off the edge of the tube.  To overcome this I used a punch to make a small indent on the steel tube.  I then made a small hole by drilling vertically.  This provided a decent surface for the drill to bite onto once tilted at an angle. 

Step 4: Frame Fabrication - Welding

Before welding I clamped all the different pieces together to make sure they all fitted and then had a go at welding on some scrap bits of metal to get the settings right and ensuring that the weld was penetrating properly through the tubing before setting to work on the actual frame.  

Things I learnt from welding this frame:

1. Metal expands when it’s hot.  Sounds pretty obvious doesn’t it?  I didn’t appreciate that it would warp the part of the frame where the bottom bracket fits.  This made it very difficult to fit the bottom bracket back in afterwards.  I would therefore suggest welding very slowly in this area (i.e allowing time between welds to prevent overheating) or tightening the b/b shell back in the frame to stiffen the frame prior to welding.

2. The welds are a little too big – I could have probably got away with a lower wire speed on the MIG welder for a more professional looking finish.  Any pro will tell you that TIG welding is much better suited for frame building and most will tell you that frames can’t be built with a MIG welder.  I chose to ignore all of this information and use what I had!  : )

Step 5: Paint Stripping

With the frame together it was time to remove the rest of the paint.  I used Nitromors paint stripper – very aggressive with paint and with skin!!  (Keep well wrapped up when using it – hands, arms and face in particular.  Even a small spec of the stuff feels like an insect sting).  After a few minutes the paint blisters up and can then be jet washed off along with any of the remaining paint stripper residue.  For stubborn paint you can get this off with a scraper or sander.

Give it a quick sand down once dry and prepare for paint.  Stuff tissue or masking tape down any bits you don’t want painted – head tube, bottom bracket, bottle holder mounts and seat tubes.  If you do get paint on them you will be better to sand it off once its dry than trying to clean it off when it’s wet as you will end up smearing the paint or getting dust/dirt stuck in it.

Step 6: Painting

Start off by spraying with primer and make sure that the frame and forks are dry and free from dust and dirt.  I used white primer simply because it was on offer at my local hardware store!  Before spraying make sure you have access all around the frame and spray methodically – working from front to back for example. If you don’t I guarantee you will miss bits.  Spray a couple of layers of primer, leaving sufficient time between coats.  I sprayed mine with the frame resting on the floor and then, once dry, turned it over to spray from the opposite side.

Then spray the bike whatever colour you want – if you want a bright colour then I’d suggest using a light (white or grey) primer as the base coat.  For dark colour frames it makes little difference – unless you are trying to get a very specific colour match.

I liked it in white, but I needed it to be black to complete the Gothic look.

Step 7: Assembly - Drivetrain

With the frame and forks painted it is now time to decide how you want to reassemble the bike.  I decided to keep the front gears as well as the back ones to give a bit more variation for steep climbs and long descents.

To make use of gears at the rear of the bike install the drive side crank as normal on the ‘admiral’s’ bottom bracket with the chain running back to the rear wheel and through the derailleur (as if you were reassembling the old bike).  You can use the existing chain etc for this if it is in good working order.

On the non-drive side you will need to fit a drive-side crank – i.e. one with a chainring fitted (chainring = large cog mounted to the cranks).  It is not a major issue if the chainrings on either side are of different sizes but it is best to keep them similar so that you still have a full range of high to low gears.

The ‘captain’s’ cranks are then put on the opposite way round to normal – i.e. the crank with the chainring will need to be fitted on the opposite side to normal.   A non-drive crank must then be fitted onto the other side. 

It is essential that the chainring on the driver’s side is an identical size to that of the adjoining passenger’s chainring as the driver and passenger rider cycling must be synchronous.  Typically the ones on my two donor bikes didn’t match but my local bike shop were very friendly and gave me some old chainrings for free.  (Yes, they were worn but they did the job)

See the basic picture below to get an idea of how the gears/chains are configured

You now need to run a chain between the captain and admiral’s chainrings.  This long chain needs to be made out of two standard chains using a chain tool.  The number of links required will depend on the chainring sizes and the distance between the front and rear bottom brackets.   Take up as much slack as you can without overtightening the chain.  You’ll know if you’ve made the chain too short as the cranks will be difficult/stiff to turn.

NOTE ON PEDALS: The pedals on drive cranks undo as you would expect, anti-clockwise.  However, the pedals on the non-drive crank will undo clockwise.  On a normal setup this helps to prevent the pedals from undoing themselves from the crank arms as you pedal.  BUT with the setup I have explained above there is a risk of the pedals coming undone as you cycle due to them being on opposite sides of the bike from normal.  As such I would suggest that you do the pedals up tighter than normal and use threadlock to ensure that they won’t come undone again.  Just be careful not to strip the thread within the crank arm as they are generally made off soft alloy which just hates being over tightened!

Step 8: Assembly - Chain Tensioner

There is now another issue to overcome as the slack in the middle of the chain needs to be taken up.  At this point you need to fit a tensioner.  You can buy one that clamps onto the frame but where is the fun in that?  I simply used part of the spare rear derailleur and, after cleaning the rust off, welded it to the frame.  The bracket needs to be stiff to ensure it doesn't flex under the tensional load in the spring.  I found that the tension wasn't quite enough to stop the chain going slack and so I removed it and drilled a new hole on the derailleur for the spring to fit into to increase its tension.  In hindsight I should have fitted the tensioner prior to spraying the bike but at the time I didn't have all the chainrings that I needed and was keen to progress with the project.  In any case, it didn’t take too long to respray this section after welding and the colour match was fine as I was using matt black.

Step 9: Assembly - Everything Else!

With the cranks done you can now fit the cables from the derailleur to the handlebars.  The front gear cable needs extending to account for the fact that the front derailleur is now further back on the bike.  This can be achieved by using the old rear gear cable if it is in good, clean condition.  For the rear gears a new, tandem specific cable will need to be purchased (£2) to fit between the handlebar all the way back to the rear wheel.  Ideally you want to avoid using the cable shrouding wherever possible as this causes friction on the cable, making it harder to change gear.  I left the cable exposed and ran it along the bottom of the bicycle.  It then only needs the shroud either end i.e. where the cable leaves the frame to the gear lever and the derailleur itself.

I used the handlebar clamp from another old bike to form the clamp between the captains’ seat post and the admiral's handlebars.  The diameter didn’t match as the seat post was a lot narrower that the steerer tube on the front forks.  To overcome this I bent a price of thin sheet metal around the full circumference of the seat tube to act as a large spacer.  This did the trick, and once tightened up it didn’t budge.

You can easily re-use the old brakes however, as I had some old V-brakes lying around I fitted these to provide a bit of extra stopping power.  V-brakes and cantilever brakes both use cables to pull a set of rubber pads onto the wheel rim.  However, the V-brakes provide better leverage and the pads tend to be a bit wider.  They are cheap to buy second hand if you are keen for extra braking power.

I had to buy new tyres and tubes as the existing ones had all perished.  I also put a bit of extra air in them once fitted to account for the fact they would each be carrying twice as much weight as they were designed for!  Finally I used new bearings in the bottom bracket and put nice fresh grease in the wheel bearings.  

Again, you’ll be needing a tandem specific brake cable for the rear brake.  A few more bits to bolt on and you will be nearly done.  One piece of advice for fitting the grips back onto the handlesbars is NOT to use anything like oil or washing up liquid.  If you do this the grips will remain slippery forever - especially on wet rides!.  My advice would be to firstly try to fit them dry and if this doesn't work use a very small amount of water to act as a lubricant.  The water will eventually dry out leaving a solid grip on the bar.  

Step 10: Finished Bike

Stickers and leopard print seat covers are optional for most, but essential when being used as part of a rocker themed charity cycle ride!!  Our maiden voyage was a 5 mile training ride.  However the very next day, the new bike, captain and admiral successfully completed the London to Brighton bike ride in England.  No major issues other than one of the pedals falling off (hence my suggestion of using threadlock) but this was solved by tightening the pedals up with a *very* large pedal spanner.

Riding the bike in itself is quite a challenge.  The captain must be very vocal when setting off, slowing down, changing gear or going over bumps.  The admiral doesn't get a good view of the road ahead and does not have access to brakes, gears or steering so needs to have 100% trust in the captain.  Start slow and get used to the bike and each other before setting off on a 50 mile bike ride!

Hope this instructable has been of use to you. Thanks for reading. : )

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