After look at online pics, i have decided to build my own mini giraffe. Im using pieces of an old bike. I want to put a push- lawnmower tire on there. Probably be about 10" or so. Might be bigger if that would help.
I am stumped on a sprocket question though. The top sprocket is going to be the front sprocket of the 20"bike i am using. I got a problem though with the bottom sprocket. How big should it be? I was going to use the back sprocket off the bike but it was a multi-speed and all the sprockets are together as one piece.
Also, how will i attach the bottom sprocket to the lawn mower wheel?
I also need help with the frame. SHould i use the bike frame and chop it up so i will already have the crank shaft (?) or should i make a custom frame??
Looks like i got my work cut out for me.
Kelly.
Have you considered using a very small children’s bike for the wheel? It seems to me that a lawnmower wheel would be incompatible with the design? I’m sure you could find a cheap kids bike with a 12" wheel, then use the bottom sprocket that’s already attached. To lock out the sprocket I’ve seen where someone welded the sprocket to the axle without changing anything else on the wheel.
Also, have you seen my prototype home designed giraffe? Maybe you could make something similar just with a smaller wheel?
As for the gear ratio, for example: on a 10" wheel you would want twice as big a cog on the cranks then on the wheel so the giraffe would pedal and balance like a 20" giraffe.
Unless you have access to welding equipment, I would recommend just using a back half of a regular bike frame; it looks kind of odd, but works quite well from what I have seen.
Keep us posted on your progress!
~Cameron
I would use a wheelbarrow wheel or a handcart wheel.
I have a photo album at my Yahoo club with photos of a mini giraffe I built with a 12" bike wheel.
The ratio seems to work the best will have an equivilant to a 20" tire.
Tire diam/#of cog teeth x #of drive sprocket teeth = 20
without going outside and counting I think the cog is 16 teeth and the cahin wheel is 24 theeth. I’ll let someone else do the arithmatic, but it is in the 19 3/4" range.
you will also want longer cranks with a giraffe than with the same wheel equivilant on a standard uni. I like to use 5" or 51/2 one piece cranksets. on my giraffes.
Al