Putting stuff in front of you seems better to me. You can keep an eye on it and it seems like a more efficient use of space. Putting the cargo behind you means extending the chain and keeping things clear of the space your feet need to pedal in.
Since I mainly wanted this bike to carry my two daughters I really wanted them to be in front of me where we can talk more easily and they have a good view.
Bikes with extended front ends are commonly called "Long Johns" and although they can seem more difficult to make at first, with the need for a steering linkage and an extra headtube, it really isn't that difficult to make one.
I dont know if this is a new way to make a Long John I made it up as I went along and it removes the need to have much in the way of jigs etc. I have a lathe and a pillar drill so I made the most of them, but with a bit of imagination you could manage without and do this whole thing with just a hand drill, a hacksaw, a file and some patience.
Even if you dont want to make a Long John I hope that you enjoy reading this instructable and it gives you some inspiration to do something else in the same way that I was inspired to write my instructables by reading other peoples'.
If you do decide to build something then make sure you stay safe, be careful with tools and don't ride any kind of bike unless you know it is safe.
Step 1: Find a Donor Bike
I didn't have to look far for a donor bike as I had this old mountain bike cluttering up the cellar. This is/was actually my wife's bike, but she hasnt ridden it in years and really deserves a new bike. It had also had a pretty rough life so the front triangle wasnt up to much anyway, so it was perfect for this project. It forced me to build in Aluminium which was fine by me because I wanted to keep the weight under control and it is easy to work with (aside from the welding). This frame is 7005 aluminium which means you need slightly different welding rods, but this isnt a huge hassle.
It is important to bear in mind that welding an aluminium frame will mess up the temper of the aluminium, but some of this strength will be regained with age hardening over time and we are going to be fairly heavily over engineering this thing anyway.
Step 2: Design It
I also opted to have a good low BB so that it would be easy to put a foot down to stabilise when stopping.
For a front wheel I went with a 20" wheel because I had plenty of them spare and plenty of good strong forks to go with it. But more importantly a small front wheel helps keep the cargo space big without the wheelbase getting too big which is a pain for manouvering in tight spaces.
I went with a fairly long front end, and in hindsight I could have shaved at least 3-4" (75-100mm) off the front end length for my immediate purposes
My design was chosen to be simple and easy to make. I also wanted to leave the design open to adaption later as my children grow. When they outgrow the box I can convert this into a "Child in-front Tandem".
By using a single rectangular tube all the way from the bottom bracket to the front headtube everything would be fairly "self jigging" and solid. I think the main tube is 50mm wide 100mm high and 3mm wall thickness and 6082 grade which isnt spectacularly good stuff, but cheap, weldable and easy to find.
If you dont have thousands of dollars wort... sorry cost of Solidworks, a pencil and paper will work just fine too, it is just a bit harder to tweak it about until you like it.
The central circle is where the kinkstand will swing if I ever get round to making it. The aim of the kickstand is to allow the children to climb in and out on their own while keeping the wheels on the ground so it doesnt tip around the stand.
Step 3: Tidy Up
Step 4: Cut Away What You Dont Need
Step 5: Start Making Things Fit Together
It is important to try to avoid damaging the threads in the BB shell, so I clamped the frame between two off-cuts of Oak. Dont stress though if you do do some slight damage as we are going to have to chase the threads out after welding anyway.
Step 6: Keep Making Things Fit Together
A good tip for getting a square mark all around a tube (whether the tube is round or square or shaped like a rabbit) is to wrap a piece of paper with a straight side around the tube; then wiggle it to get the ends to meet up. As long as the tube is not tapered the resulting line will be perpendicular to the axis of the tube. If you want the holes for say the headtube to be off perpendicular then you can just measure away from this line the correct amount.
So to get a headtube at 88 degrees to the main tube you mark one side, then wrap the paper and mark 3.5mm off to get that 2 degree deviation (100 tan 2). Then just drill through both marks straight. A little filing will get it all working.
Step 7: Keep Checking Your Progress
Step 8: More Trimming
But now it is time to whip off the top tube too. To avoid damaging anything whilst filing I chose to clamp the frame to an old stub of seatpost and then clamp that in the vice.
Step 9: Brace Tube Fabrication
I didnt want to make the brace super beefy so it was going to come in directly on a flange of the box and clear of the sidewalls, so to prevent this wall buckling in I added an extra plate here. Because the thin space between the reinforcement plate and the main beam needs to breathe during welding I put a hole through the middle.
I used the lathe to mitre the top end of the tube in the sketchy way shown below.
Step 10: Welded and Box Mount
Those are some nice welds right? Shame I cant take credit for them. I do have a TIG welder that could do it, but I also have an awesome family of welders in my city who have been helping me out for years. JNC welding in Sheffield. They weld everything from copper to titanium and surgical instruments to ice-cream moulds. Most big cities will have some jobbing welders who will help you out. Take them tea and biscuits and make friends. Pay cash and respect their experience and expertise and you will be set forever for all your welding needs.
Step 11: Post-weld Adjustments
In the before and after pics you can see weld in the seat tube. It just happens that I had a suitable size reamer so I cleared this out myself, but I didn't have taps for the BB shell so I took it to my local bike shop for that step. Most good bike shops will have both these tools and shouldn't charge you much to do the work.
Step 12: Paint and Weight
It turns out that this paint DOES work on aluminium but not nearly as well as it does on wood where it is far superior to modern alkalid paints as it lets the wood breathe.
I also took the opportunity to weigh the frame. About 10lbs which isnt bad considering, though obviously you get the added weight of the steering linkage and extra steering column.
Step 13: Make the Steering Bits
The steering column is just a 1,1/8" aluminium tube with a plate welded to the end. I use two top headset sections and two seat-clamps to locate this on the bearings so there is no need for any precise machining on here (this tube is too big to fit in my lathe). The seat clamp and top wedge arrangement also allows me to fine tune the position of the steerer a little.
The link rod is just a tube with two turned bosses welded in the ends, and cable guides fitted. I didnt want to use a super long (tandem specific) brake cable and breaking the outer brake cable like this reduces flex and allows the use of two standard length cables joined with a little connector on this stretch. I also routed the front brake cable down through the steerer tube to eliminate another run of outer cable and for neatness.
Two spherical rod ends screw into the ends of the link rod to cope with the offset steering axis etc. In hindsight a steeper steering column angle would have helped with this but might have made the seating position in the box a bit upright.
The final part of the steering system is the fork peg. The neat way to do this is to fix it to the crown of the fork, but I was getting impatient by this stage and this is super quick and easy to do. The square "peg" bolts onto the end of the hub axle and has the spherical rod end bolt into one side.
Step 14: Make Any Drive Parts You Need
Because of this I had to work out the ratios carefully and use suitable size sprockets, to avoid using a chain tensioner. In my case it turned out that 33:20 (from memory) was the right gear. I also wanted to run a nice fat single speed BMX chain instead of a narrow chain, so I wanted proper 1/8" thick sprockets. But the only cranks I had spare for a euro BB were these nasty things.
But a bit of work on the lathe and pillar drill soon married an old 33 tooth BMX sprocket to the multispeed crankset spider.
Step 15: Get It Together and Test Ride
And the Shimano Nexus hub comes with a nasty grip-shift instead of a lovely thumb shifter (BOO!) so I needed to file the brake-lever to clear it.
With it all assembled I did a quick weigh again and then took it for a spin. The weight at this stage is 17.4 kgs which is about 38lbs, and this showed when riding it in this state. With no box on it rode beautifully and felt nice and stable at speed thanks to the shear length of the wheelbase. Steering takes virtually no time to get used to. The only weird thing is that you need to steer MORE than normal, ie. when you might normally steer through 10 degrees you need to steer through 15 or 20 with this to make up for the long wheelbase. This could be accounted for by making the peg on the fork shorter than the arm on the steering column, but I had little tyre clearance/steering angle available anyway so I didnt want to reduce it further.
Step 16: Build Your Cargo Bay
One sheet of ply was notched to hang over the main beam and form a back, and one sheet was nothced and slid up under the main beam at the front to screw to the front plate. Then it was just a case of linking all the sides and floor with angle. Because none of the angles were 90degrees I had to open out each piece of angle by squashing the corner between a round steel bar and the vice jaw.
Hopefully the pictures are fairly self explanatory. Main corner pieces were screwed on and then corner additions pop-riveted through those to solidify the corners.
These views also give you a good look at some of the steering linkage parts.
One thing to note is that I brought the bike up from the cellar to build the box as I wasnt sure it would fit up the stairs with it fitted.
Step 17: Seatbelts
Step 18: Go Ride.
1. Bikes are awesome.
2. Bikes for more than one person rule.
3. If you want a cargo bike but don't want to pay thousands for a Dutch tank made of Hi-Ten steel think about building your own.
4. This bike is now close to 50lbs. My daughters now (a year on) weigh about 40lbs each. Yet picking them up from nursery and riding back up a steep hill is an absolute pleasure. They love it and I love it. Although it is obviously damn hard work going up a 1 in 5 with a 300lb gross weight vehicle the gears arguably make it easier than pushing them in a pram.
5. You could always add an electric assist.
6. If you build one, think long and hard about the handlebar height/clearance and the brakes. This really needs a front disc for the hills where I live.
I think that's it. If I missed anything ask me in the comments.