My cycling has had to take a back seat for the last two months since the birth of my gorgeous twin girls georgie and grace. I was thinking about making a cargo bike like the ones on instructables. The only concern i have regarding the kids in front in the box is that all the cycle paths in my area have barriers to stop motorbikes from getting onto the paths which wouldnt let me get this design through. Having nearly given up on the idea i typed "two kids on a bike" into google and it came up with alot of pictures of different bikes. Scrolling through these images i stumbled upon a bike made long enough to have two cycle kids seats attached!!!! bingo!!!! I couldnt find anything like it on here so decided to not only make one but to write it up as an instructable. I soon found some suitable bike frames on ebay, locally for five pounds. I also did a rough sketch to get the idea straight in my head.
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Step 1: Parts
The frames i got of ebay were a struggle to strip as they had been stored outside. To get the saddle post and bottom bracket cups out i had to weld pieces of scrap steel to them so i could unscrew them from the frame (i think the temperature of the welding has a cracking effect on the rusted up components). but eventually i had two strippped frames. I stuck two wheels on the frame to be the front to get the height right them a rear on the rear!!! After some placing next to each other and trying the seat i got from my brotherinlaw I rekoned that the rear frame needed to be 17 inches seat tube to seat tube. I marked this onto the frame and used a hole saw to cut through the frame. As it was a cheap saw it soon burnt out about halfway through each side. Now i used a hacksaw to chop off the head tube then finnish off with my angle grinder until i had a good fit onto the seat tube of the front frame.
Step 2: Welding
I used a length of square tubing as a jig and clamped the frames to it, together. They were then tacked together using my mig welder. I then clamped the front frames chainstays together until they touched the down tube of the rear frame. I replaced the clamp ( it was a bit dodgy and looked like it could ping off at any second ) with an m8 bolt before cleaning the paint off and welding together. After it had cooled i removed the steel tube and clamps whitch left me an impressive looking mini tandem frame.
Step 3: Dry Run
Just finished the welding and grinding on the frame. I also ground off the cable guides of the top tube of the front bike and will have to make and weld on some new ones in a better position matching the rear frames. I also cold set the rear drop outs as the wheel im using is 135mm wide and the frame was 125mm. To do this i used the sheldon brown method which is to open up one side using a 4foot lenght of 4by2 through the rear triangle and up against the seat tube . With a few tugs on this it should bend a little keep doing this till it is half the difference (130mm) then swap the wood around and bend the otherside to the 135mm. The rear wheel now fits a lot easier!!!!! my impatience now took hold and i fitted the centre stand that i purchased the wheels then the child seat. All apears in the correct position and should work a treat.
Just picked up the second seat bought from ebay for a tenner. Couldnt resist another dry run.
For the new cable guides i hacksawed some of one of the bits of donor frame that i have lying around. These were filed to clean uo then welded to the top tube in the best place. Next step was to apply paint. There are plenty of instructables describing how to paint a cycle frame which explain it much better than i ever could so i wont be going into to much detail here. First rub the frame with wetndry paper then prime then when dry rubagain with finer wetndry paper then on with the top coloured coats. Not the best paint job but im not going to be entering any show with it!!!!!!!
I recently had an early day so manage to crack on a bit with the bike. I fitted the forks and wheels also the stand to make the rest of the build up easier. I also started cleaning the derailers and brakes ready to fit.
Another early day and managed to bolt some bits onto the frame and then see if the girls like it. Good Friday and ive managed to fit brakes derailers chain and then all the cables and levers. Didnt have any brake blocks but still had to take it for its maiden voyage!!!!! It rides realy well. when back in the garage i applied the stickers i got of ebay as a finnishing touch. Just need the girls heads to grow into their helmets before we can try it properly buti will take it for a few rides before then.