Hyena wrote:Chalo wrote:24" and 26" sizes (20" and 22" in motorcycle lingo)
Can John or someone else confirm that a 20" motorcycle tyre will indeed fit properly on a 24" bicycle rim ?
20" doesn't seem to be a common size but I'll keep my eye out for some locally if they can be shoe horned onto my 39mm wide sun double tracks
(sorry a bit OT)
johnrobholmes wrote:Very good discussion about the strength to weight ratio of the parts and why the rim strength is more important than spoke strength. As much as I would LOVE to start out with a custom extrusion for our needs, I can't afford it without bringing in a few loads of "normal" rims first. I already have an extrusion drawn up for use with 15 through 13ga spokes, but the problem is the angled nipple seats combined with a box extrusion design. The existing tooling can't angle dimple through a double wall rim. So we have tooling for a new extrusion, and we have tooling for the dimple machine that needs to be made. The final question is whether to put a bicycle bead hook or a moped bead hook on it, as we can't do both with one rim.
johnrobholmes wrote:I can also get fatter nipples to avoid using washers. I have been using 13ga fat nipples to adapt normal hubs to moped rims for about a year now.
Chalo wrote:johnrobholmes wrote:I can also get fatter nipples to avoid using washers. I have been using 13ga fat nipples to adapt normal hubs to moped rims for about a year now.
Interesting. I'll bet that makes mixing bicycle hubs and moto rims a lot more feasible and reliable.
I wonder if such nipps can be gotten in 14ga, since all butted spokes that would be of interest here have 14ga threads. (That's normal 14-15ga double butted, 13-14ga single butted, and 13-15-14ga triple butted.)
Chalo wrote:biohazardman wrote:As far as spoke sizes go in a decent quality spoke thicker is stronger.
Yes, but spokes don't carry wheel loads-- they only carry preload. They only have to be strong enough for their preload. The rim carries the load. A thinner spoke is more elastic and thus able to follow a rim more faithfully as it moves under load, without becoming loose or failing to support the rim.Bicycles have skinny spokes and lower loads,
Tandems? Triplets? Quads? Quints? They use 14ga or 14/15ga spokes too, just like regular single bikes. They just use stronger rims and slightly higher spoke counts (48 instead of 36). The bike in the picture below is spec'ed with spokes that are 14ga (2.0mm) or 15ga (1.8mm) in the middle, depending on wheel size. I'm guessing the folks at Santana Tandems have a little more experience and proven success with carrying heavy loads on bike wheels than anyone here:
When you beef up the rim, the structural demands on the spokes become smaller. That's why the folks at Shimano were able to design this wheelset for Santana tandems:
I think there are practical reasons to use more than 16 spokes per wheel, but this is a good demonstration that the wheel's strength is not in its spokes.mopeds have thicker spokes and a heavier loads, motorcycles are even thicker and cars well it's not a mute point that thicker spokes are stronger in a properly built wheel.
It is a fact that thick-spoked moped, motorcycle, and car wheels have lower strength-to-weight and stiffness-to-weight ratios than ordinary bicycle wheels. They might be ten times stronger, but only by being twenty times heavier. That's not a smart way to build anything. Moto wheels are the way they are mainly so that they'll be cheap for the manufacturer (even if building them the same way is not so cheap for us). Since we here are willing to spend what it takes in money and effort to do the job right, we should be using proper design and engineering, not just pig iron.It is however difficult to build a decent wheel with the hub motors we use often being so big. Like others have said it would be nice if we had bicycle rims with the angled eyelets like the mopeds and motorcycles have as drilling bicycle rims is tedious work and can weaken things.
Cross-1 lacing usually does the trick, unless the rim is too small for the motor, or the spoke nipples are too fat for the holes in the rim. Since cross-1 and radial lacing pull outward from the hub flange, there's another reason to use normal thin spokes. The hub flange holes can be smaller and the variations in tension from riding much less abrupt than that of thicker spokes, so the hub flanges are less likely to break. For the same reasons, thinner spokes are less likely to crack rims at the spoke holes.
I have a few new old stock Araya 20" bicycle rims that have deep dimples with angled spoke holes. It's not a bad idea in principle, but it limits the lacing patterns you can use on a given rim. In the case of the 36 hole rims I have, they can only be laced up cross-2, -3, or -4 in a plain alternating pattern on a normal sized hub. The holes would have to be angled much more than they are to fit a hub motor that's more than half the diameter of the rim.
You can get a wider range of insertion angle if you use normal 14ga or 15ga spoke nipples, rather than fatties that don't have room to gimbal in the rim holes. Spherical headed nipples help a little bit too, compared with conical headed ones.
johnrobholmes wrote:3" wide probably. 2.75" would be preferred. The alloy rims will be 1.6" wide, those take 3" tires well.
gensem wrote:John, prebuilt black moped wheels would rock!
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