Each rider controls one wheel. Pedal together and you move in a straight line forward or backward. Anything else is a turn including a spin in place by pedaling in opposite directions. I guessed a top speed of around 7mph would be a good start. I set the gear ratio accordingly. It was designed for kids around 5' tall, but it can easily handle taller. I am 5'6" and about 160lbs. I rode it with my daughter and it worked well.
This instructable details how to make a basic version. I designed everything in Pro/E. I have exported all the parts to DXF format so you can access with free software like QCAD. The drawings have basic dimensions for overall reference. They are 1:1 so you can scale off them or add additional dimensions. There are also PDFs too. I used my homemade CNC router so I added a lot of details that are not required. Need more info, detail, pictures...just ask.
The project took me about 16-20 hours over 3 weeks to build. A lot of that was design and testing, so it could take you less time. I had a lot of left over and found material that I used. If you started from scratch this could cost $150 to $200 to build. The bearings and drive train parts are the most expensive. I bought them at a surplus store. Hopefully you can find them cheaper.
The design worked pretty much as intended without any major problems. I did learn a few things along the way. I added "possible improvements" sections to each step that might make your version better and easier to build.
The working name is SteamRoller due to the steampunk look. The kids like Wheels of Doom and Portable Porch Swing. Does anyone else have any suggestions?
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Signing UpStep 1: Materials
Wood
(2) 4' x 8' sheets of 3/4" Plywood (I used BC Exterior grade)
(1) 4' x 8' sheet of 1/2" Plywood (I used BC Exterior grade)
(1) 2 x 4 x 6' pine board
(1) 1 x 6 x 6' pine board
Surplus Center Parts
(4) 7/8 4 Bolt Bearing Block (#1-205-14-4)
(2) 10' pieces .40 pitch chain (#1-1163-40)
(2) 11 tooth 7/8" shaft sprocket (#1-2123-11-D)
(2) 30 tooth sprocket. (#1-2123-30-4B)
(4) 7/8" dia. shaft collars (#1-2766-87)
(2) #40 Chain Connecting Link (#1-1087-40)
(4) 7/8" I.D. bearings (eBay)
6' of 3/4" heavy wall copper tubing
4' of 1" thin wall copper tubing.
(12) 3/4" 90deg copper elbows. (buy a bag/box of them...much cheaper)
(2) 1" copper end caps.
(2) 8" long 1/2" pipe (wheel Axles)
(2) 1/2" pipe flanges (mounts axles)
26' 5/8" I.D. Heater tubing
5/8" double barbed fitting.
1/8" NPT Schreader tire value












































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I am looking to clear it out of my garage. It takes up too much room. If someone in the Chicago area wants it, make me an offer.
The kids are going to be a little upset :-(
For the one person version we could use a a V- belt drive with a Variable speed pulley to change the speed of one wheel, so we can control the direction by adjusting the pulley.
The V-Belt variable speed pulley are not expensive and it is available for a range of torques and dimensions.
Your design is AWESOME!!
It's looks like something you would need to wait in line and pay to ride. The worry-wart in me is afraid of any little fingers or arms going into those spokes. Perhaps a little netting or wire would prevent that?
Keep building cool stuff!
And yeah, still awesome even with the flexing.
I'd love to do a single seater version, hand cranked. Would then fit in bike lanes and also be suitable for disabled use as a bonus. I can almost see it but the models I've tried to generate in the PC so far suck.
Plus a hand cranked idea adds the option of hybrid human/electric - batteries under the seat for stability
http://www.thebigbearingstore.com/servlet/the-4-dsh-Bolt-Flange-Bearings-cln-Set-Screw-Locking/Categories