William K. - I agree with your comments, "redundant supports and safety wires on the support bolts would be the best way."
For the record, this belt guard mount has been trouble-free, since I attached the guard screws with lock-tite blue AND the back mount also with safety wire.
The screws are small enough diameter that I am VERY careful on torque. The front screw is a button head, so I was not able to cross-drill the head for safety wire (or I would). I didn't replace that button head with a SHCS, because I didn't want a form that could rub or catch on the belt in any condition.
I also monitor this component (and the top belt guard) very closely now that I am more aware of their vunerability.
Thanks for the information about the problem of stuff getting caught in the belt. That is one of the things that those touting belt drive never mention. I have not had a rock get caught up in a chain, although I did have a chain come off one time and wrap between the big sprocket and the spokes. I came to a very squirrly stop with the rear wheel locked, fortunately I was just starting up when it happened. I learned how critical chain tension is, and a bit about chain paths. That bike got a back-side chain idler and always had correct belt tension from there on for the next 20 years.
But still it seems that there should be a way to avoid that kind of hazard with the belt guard.Safety wires on the bolt is a good approach, but redundant supports and safety wires on the support bolts would be the best way.
William K. "The fundamental design flaw was putting anything inside the belt loop. If there really was a need for the guard it would be covering the loop so as to prevent anything from getting caught in the drive pulley or getting chewed by the belt teeth. When a correctly implemented belt guard falls onto the belt it will make a lot of noise and wear the belt, but never result in a loss of control."
I agree with you in principle; however, the one other design consideration that I have become aware of is that rocks or sticks can be deflected by the rear tire and land in that belt loop causing a lock-up or damage to the belt and rear pulley. This guard was designed to reduce this possibility without having the guard itself creating other problems of making frequent belt inspection impossible without partial disassembly. Design is indeed a trade-off of sometimes conflicting considerations.
I still feel that it is important to have better retention of this guard to avoid potentially lethal consequences. Mine is now safety wired.
You are certainly correct about the "social stigma" associated with drive shafts.
Any manufacturer would love to have that kind of loyalty to their product.
I suppose that it would be possible to come up with a rugged enough type of U-joint, but it would probably be heavier and I know that it would cost more, and besides that it would make field changing the driven end ratio awhole lot more complex, at best.
Probably a bike without a chain could be safer, but there are other things to be considered. Some motorcycles wind up being used in rather harsh terrain and in a very abusive (to the bike) manner. The result is that a bike with a drive shaft would be damaged to the point of being disabled and needing shop repair in a fairly short time, since the universal joint is a relatively fragile part, and does not generally like large changes in angle. Toothed belts are much better in that area, and are often used, but a damaged belt requires replacement, since they are not generally repairable. Chains and sprockets do wear more than belts and pulleys, but chains are field repairable, and also replacable with less effort than a normal belt replacement requires.
So the application requires consideration. In addition, a belt will chew up a leg almost as much as a chain will, if one contacts the side of either one. At least that is what I have read, but not experienced.
It is very exciting to have a rear wheel lock up. It happened to me one time just coming foo the line, when "the engine broke".
The fundamental design flaw was putting anything inside the belt loop. If there really was a need for the guard it would be covering the loop so as to prevent anything from getting caught in the drive pulley or getting chewed by the belt teeth. When a correctly implemented belt guard falls onto the belt it will make a lot of noise and wear the belt, but never result in a loss of control.
The bike that I built had an idler that held the chainin line with the engine-end sprocket at the same time that it kept the chain adjusted correctly. It was similar in shape to a pulley, except that the edges did not taper very much. The result was that as the chain would stretch, which they certainly do, the slack was easy to adjust out, and when the limits of the adjuster were reached the chain was due to be replaced anyway. PLus, it looked good.
Of course, there are those who claim that "real bikes have chains", but that would be part of a different discussion.
What should be the perception of a product’s real-world performance with regard to the published spec sheet? While it is easy to assume that the product will operate according to spec, what variables should be considered, and is that a designer obligation or a customer responsibility? Or both?
Biomimicry has already found its way into the development of robots and new materials, with researchers studying animals and nature to come up with new innovations. Now thanks to researchers in Boston, biomimicry could even inform the future of electrical networks for next-generation displays.
Focus on Fundamentals consists of 45-minute on-line classes that cover a host of technologies. You learn without leaving the comfort of your desk. All classes are taught by subject-matter experts and all are archived. So if you can't attend live, attend at your convenience.