casters

[gfish]

The one big question mark in the Kalamazoo's design is the front wheels. They need to caster, to allow for steering. And they need to be big and pneumatic, to smooth the ride. I did find some references to 25 inch industrial models that fit these requirements -- at a cool $1k each. So, uh, no. Going to have to make them myself from bike wheels.

Have any of you, my kind and loyal readers, ever done something like this? I can't find any guidelines on the web on the best way to approach this. There is a certain amount of caster effect in a normally-mounted bicycle wheel, but I have no idea if it will be enough, even if I increase the head angle. This would have the advantage of letting me use a standard bike fork and head tube pivot. (Though how I can cleanly and solidly mount it to the Kalamazoo frame is a bit of an open question.) Do people think that would work as a caster for a platform like this?

The other main alternative I see is to fab a new wheel frame with a pivoting swivel plate set back. Turn it into a standard caster design, basically. I'd rather not do this if I can avoid it, as there will be a lot of weird forces at work on this thing. And I'd still have the offset of the swivel plate as a tweakable parameter what would need optimizing.

These issues will have to be solved fairly quickly once I start construction, as getting the wheels mounted will be the first thing done after building the frame itself. There are too many questions (like how how close to the rear axle can I stand when piloting solo without risking flipping it) which impact later design choices that need to be answered empirically.

Comments

[tfabris.livejournal.com]

Weight? On the wheels and on the bearings. Bicycle wheels are intended to take only the weight of a bike and its rider.

[gfish.livejournal.com]

It's something to keep in mind, but I'm not too worried. There will be very little dynamic loading of the Kalamazoo -- no curb jumping. I'll want wide mountain bike/balloon tires anyway for the playa, so it's not like I'd be using super light racing parts. I don't think tandems are made from particularly heavy parts, and 1 person per wheel is more or less what I'm aiming for in terms of max loading.

[randomdreams.livejournal.com]

Tandems often/usually have more spokes, but the hubs themselves are the same internals.

[gfish.livejournal.com]

But it is a reason I really want to avoid making my own caster from scratch, I should add. That's a lot of weird torquey forces to subject my pathetic welds to.