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Happy fourth!

Too late...I've unstuck! :) For weeks I thought the same, it didn't seem to work. I made ideas one after another, for parts of the crossbow, but they didn't fit together (too big, too long, too heavy, one part makes the operation of the other one impossible...I have details, but they are...

Thank you for the feedback (poll).

Stuck with that. (trigger) I don't give up! Basically, it's not so hard to make one, but I want such one which stops the "limbs", not the string. The reason is to launch light projectiles at higher speeds. In that case, the string load would only consist of the inertia of the accelerating...

I'm still working on a good combination of trigger and nock-string interface. Very difficult.(Many unusual requirements at one place).

Do cables break at the cams frequently?

M-Cameron, your every line is either gloomy, not true, or contains pseudo-science. Please don't take it as an offense, because it disturbs much more people who take science seriously.

Thanks, SeekHer! And what about Picatinny rails? Why Weaver instead of Picatinny? Is the Picatinny rather militaristic?

The good thing is, anybody can alter the fork width while keeping energy unchanged. X times less spacing, X times more folds of rubber band, still no play, smaller draw length, bigger draw force, same energy.

All right. Your math is not exactly OK, because you fail to show how exactly that force of yours does work on (actually non-existing) displacements. No displacement sideway: no work by sideway force. You just calculate the side component of the band pull force. :banghead:

Maybe we should start another thread and leave poor people in peace. Then we could discuss this disturbance in the Force, Jedi. Whoamzzz. Kshhhhhhhzzmm. :cool: Seriously, I don't want to second-guess Joerg's experience, he and others might get better efficiency accompanied by a narrower...

Never mind, Joerg, do what you think is right, given all the circumstances, you must be right about fork width, but what M-Cameron says... that's medieval. P.S. - I'm glad to hear you have a physicist brother. One physicist is enough, huh?:)

M-Cameron, you want me to get a stroke.

M-Cameron: Here's the proof. l= the total loose lenght of the rubber band K=spring constant of the rubber band F (not F(s))= maximum rubber load (one band) No link, no book, no "my experience". I think the alleged change in efficiency in practice is due to that many things are...

I r o n y. I guess all the engineers around the world should be fired, they're useless, because they calculate before build. Cars, airplanes, guns are just grown on farms, unless built from LEGO by trial-and-error.

OK, I won't argue with you, Joerg. But with Cameron...

Sheet metal yield strength is 59 000 psi. Quite strong. Good for a testbed.

Most rails I've seen on crossbows looked Weaver rail to me. Is that right? If it is, why?

Picatinny all over the cover? :D "Groovy, baby!" (Austin Powers) OK, I googled "excalibur trigger pull". The trigger is a little stiff (3-3.5lbs), and there's a big pull before the let-off.

In the meanwhile, I've measured material properties. Sorry for the slow progress. I found interesting results: The elastic energy content per unit weight of rubber is 8 times more than that of spring steel. (No, I'm not stating that rubber is stronger.) NERD WARNING Formula: (Spec...