Build a 2-wheel Cargo Bike

Intro: Build a 2-wheel Cargo Bike

as promised in my last instructable, here's my attempt to build a 2-wheeler. why? i got infected by the bike-building virus. especially cargo bikes are just awesome vehicles: you meet lots of new people ("hey, what's this?"), you can transport nearly everything you need on a regular basis and it's better than a car if you live in a city like me (no parking fees, no searching for space to park a car, no insurances, taxes, gasoline, healthier & better for the environment,...). so go on and build your own, it's not that hard ;-)

STEP 1: Donor Frames

(sorry no pic) i got myself two donor frames from the local dump: an old 26'' mountainbike (hardtail) and a 20'' kids bike. the kids bike is just needed for the front fork and wheel, so if you find one where everything else is rusty and broken - take it! the other bike is used as a whole.

STEP 2: Bulding the Frame Pt.I

after disassembling the bikes completely i took the bigger one and welded two tubes (construction steel, 34x2mm) to it as shown in the picture.

STEP 3: Frame Construction

now it's time to decide how long your bike should be. after that i suggest to draw the front construction 1:1 on some paper and put the rear part beneath it. it helps a lot to see if everything fits together. after that use it to weld the pieces together.
some technical notes:
- be careful to have the main tube to the front parallel to the ground. this means to measure exactly as possible the dimensions of the front wheel and fork and the center of the back wheel (see drawing)
- for the steering angle of the front wheel i used 75°

STEP 4: Steering

take the fork from the bigger donor bike and cut it in three pieces as shown above. then weld the top two pieces to another steel tube (something that fits inside the head tube (by the way, a good source to learn bikeframe vocabulary is here: http://aarline.info/hotaar/wp-content/uploads/2011/09/BicycleTypogram_mini_Black2.png )) and extend the bottom with a piece of steel.

STEP 5: Fork

add a piece of metal to the fork in an angle of 90° as shown in the pic. a better position would be to move it more to the top (see annotation). that gives the wheel more space in left turns.
be careful to have the same distance from wheel center to the hole for the steering axis and from he center of the head tube to the hole for the steering axis. if these are different turning the handlebar doesn't result in the same turning of the front wheel.

STEP 6: Mounting the Steering

the steering axis is screwed to some ball joints and connected to the two holes where it should rest. added is also some support to the bottom tube (see pic).

STEP 7: Putting Everything Together

STEP 8: Disassembling and Cleaning

everything is disassembled and all metal parts are cleaned from rust and old paint. what you also see in this picture is the support for the load-box, made of steel tube and welded to the frame. the stand in the background is also made of small steel tube and was a pain to construct. next time i will try some motorbike kickstands, maybe that works out, too.

STEP 9: Painting the Frame

STEP 10: Putting Everything Together

it's done!

Comments

[Marie-LaureY]

Hi there!
Was really interested in trying this but have never done any welding before. Is it difficult?? I am fairly handy...
Also, I saw you have plans for 2 wheels vs 3 wheels and mentioned 2 wheels is easier to maneuver. How steady is it though, once you load the cargo box with stuff (or kids in my case)? it seems it would be hard to keep a balance but not sure.
Thanks!

[carkat]

hi!
welding isn't difficult, but it needs some practicing. it's easier to learn if you can find someone who knows how to weld and is willing to show you how when you try it for the first time. also, in my opinion, don't start with tig or stick-welding. although for the latter one you can find pretty cheap machines to buy, it's the most difficult method for welding. i'd say mig/mag welding is the method to start with.
the "easier to maneuver" is just because of the smaller size - i'm speaking of central-european streets in cities here, which tend to be quite small sometimes. the three-wheeler is definitely more stable (except for turns; there it tends to tilt if you're not slow enough). if you're used to riding it, the two-wheeler is easy to handle, even with fidgety kids in the box (i know what i'm speaking of, trust me ;) ). but i would ride it for a few days before you load the kids up, just to make sure.
in general i would say that if you think of using a cargo bike for transporting your kids and stuff - go for it! i'm bringing my kids to kindergarten and school for 10 years now with the cargo bikes and neither of us would want to miss this morning routine. also i am living car-free for the same period, there's no need for one if you can haul stuff by cargobike.

[weldinpatt]

is that a file you have welded to the right hand fork leg ? I hope not the metal that files are made of is very hard but also brittle, too brittle i think for that application . try sticking one in a vice and whack it back over with a sledge i love systems with a drag link as it allows alterations in the steering ratio rather than the direct method traditionally used it's the parallelogram of forces from physics a school, I loved it
i only wish to be positive and constructive this represents a safety issue snapped files snap sharp like a flint tool you might be able to take the temper out if you heat it to red all over and let it cool on its own.

[carkat]

Hi, thanks for the hint. Might look like a file, but it's just a piece of mild steel...

[cueball0019]

Hello carkat.
First this looks like a great build.
My question is. When you extended the head tube on the bigger donor bike did you put a bearing cup at the bottom to help stabilize the steering tube?
Regards

[carkat]

thank you! there's a bearing cup at the bottom of the extended head tube, yes. probably it's a good idea to check if it fits in the new tube first before cutting/welding...

[cueball0019]

Hello Carkat.
I was wondering you used 34mm x 2mm tubing for the frame. Is that i.d. or o.d.?
Regards

[carkat]

hi, that's 34mm outer diameter and 2mm wall thickness!

[FilipJ8]

Bravo!!!

[mawwwk]

What was the angle of the tube that meets the fork steer tube?

[carkat]

hi, that angle depends on a few factors. i don't know the angle anymore, sorry. but i would recommend to draw the front in 1:1 scale to get that angle. the fork angle should be somewhere between 73 and 75 degrees (the more degrees the more stiff is the steering). then add the tube going down so that it doesn't interfere with the wheel (or the fender if you have one).

hope thathelps!

[mawwwk]

Yeah, I figured it depends on the rake of the fork. My plans of 73 degree angle, but I haven't been able to find any specs on cargo bikes to verify that this is anywhere close.

[rwoudenberg]

If you can get a donor cheap mountain bike with a dual crown fork the tubes slide into the steerer! So by cutting the steerer you can braze the stanchion tube form the shock and braze the rest of the steere to the top. The rest of the bikes tubes can finish the external parts.Ill post a photo soon. Do you have your plans for the box?

[carkat]

sounds good, though i'm not sure i got everything what you wrote :-) a photo would be great! re. the box: unfortunately not. it was a build on the go - i took material i had lying around and built without planning. sorry!

[Maestro Jacob]

Beautiful! Im considering trying this build, I will post it here if I do:-)

[carkat]

yeah, please do so! thanks!

[fvega3]

this is very good i would like to build a few and pass them around.

[carkat]

thanks! passing them on would be a great idea - so people could actually experience on their own how it is to live a less car-centric life without having to make an investment beforehand :-)

[Neander]

That is cool! I plan on making one like this but from a 3-wheel bike, so I have front and rear cargo space!

[carkat]

sounds great! if you're done with it a pic of your work would be highly appreciated. thanks!