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  1. #1
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    20" Wheels with 20mm thru axle Question

    I am tinkering with a toy project with some fellow colleagues. We came across various recumbent trikes/tadpoles in which we observed one model in particular that appears to have exactly what could work in our application. The front wheel assembly as spec’d on CatTrikes, from what I can gather, are 20” wheels, disc compatible and have 20mm thru hole hubs that allow the fastening of the wheel to a spindle in a single side manner (in other words, a dual leg fork is not required). Is it the case that each and every recumbent manufacturer machines their own hubs so that they are compatible with their spindles? Looking to sites such as Mavic, Hed and Velocity, I was able to determine that though they can definitely offer the rims and traditional hubs, I could not see the “hub systems” as found on the various tadpole front wheel assemblies to be available in an easy manner.

    I can image a few questions that would come to mind, and as such, I will attempt to address them here:

    How much weight will be loaded to the wheels/hubs: Technically, they will be required to carry an adult, but the adult will not be directly over the wheels/center axle, such as for example, in the case of a unicycle. At the same time, the adult will not be so extremely offset such as in the case of a tadpole. I estimate that the adult’s torso, seated in an upright position, will be centered approximately 25 – 30” from this axle points of the front wheels.

    Are Disc Brakes necessary? Personally, I do not think it is necessary from a stopping power argument. However, from a technical point, the routing of the cables for a clean pull of the disc brake caliper would be so much easier. My intent is that we would utilize Avid BB5 Disc Brake Assemblies. Given the application, I believe that the right compromise of economics and stopping power can be had. Of course, if calipers prove that much more economical and can sustain the pull of a complex cable routing system, we may rethink this position. Said more directly, our fear is that the caliper of a V-Brake or standard “road bike” brake caliper will pull to one side as opposed to having both arms compress against the rim equally given the fact that we are not able to have a straight line trajectory in our cable pull.

    Type of wheel? To be quite honest, I am not sure. Based on the application and weight load, I am hopeful that someone could recommend the number of spokes/type of spokes and rim that can carry the load. To be sure, it is not our intent to traverse mountains or technical single track. Instead the primary purpose will be street applications. However, having said this, we must be cognizant of the role that poor, deteriorating roads/pavement can have on a wheel’s ability to stay true. Still yet, we are not in any way attempting to break speed records. We simply need to traverse from point A to point B but in a manner that allows the lease amount of rolling resistance while keeping economics into the scheme of things. For sure, some ultra carbon only wheels could be pretty to look at, but it would simply be overkill. Using a rim that will come out of true in less than one ride or have such a profound effect in terms of rolling resistance due to weight would not serve our purpose either.

    Is a quick-release application required? Technically no. A bolt fastening system could work, however in terms of attaching and detaching, a skewer system would be simply an easier process. Be sure that this skewer will not pass through a spindle such as on a tadpole/Cat-Trike, but simply a bracket with a hole in it. Think of this as the rear end of a “little radio-flyer” wagon (the non-steering end) but with no axle that is required to connect both wheels (only an axle that is long enough to travel the length of the hub and X amount more space to pass through the thickness of the bracket (perhaps 6-10mm).

    No doubt, trying to explain all of this in writing is not the easiest, thus I hope I was clear enough. Any information or parts/material that you could advise of that would meet our requirements would be most appreciative, and of course, should further explanation be required, I will be glad to expound on any points.

  2. #2
    META Severian's Avatar
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    ONE... In the grand tradition of the Society of Improbable Research: Can you, in 7 words or less, describe what your project actually is supposed to be?

    and TWO... If your intent in writing this is to "debunk" the frame design and component choices of recumbent makers in particular (and bicycles in general) I'm not sure you've quite done your research very well.

    and THREE... to answer the question you half-asked in your first paragraph. You can get ANYTHING machined in Taiwan.

  3. #3
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    This goes along with a question I have too- I am working on fixing up a quadracycle, and thanks to some great advice I got from this board, I was able to remove the (rusty) front wheels.

    Now I'm looking to see if replacement (moped or bicycle) wheels could be found for a reasonable price. Here are the specs from what I can tell:

    Axle diameter: 20mm (about 3/4")
    Rim diameter: 16"
    Tire diameter: 20"

    And the length of the axle (stub axle) where the wheel spins is about 2 7/8" or maybe 73mm... I'm not sure if this would be called the spacing or not. Again, this is a stub axle so it has a cap on one end (no forks or dropouts).

    Do any of you guys think that a wheel could be found online or in a store that would fit those specs? They sound similar to the specs that the OP is looking for.

    Thanks,
    Lobojpm

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