Re: Bell cap how to

[jvrjenivs]

I reread some of the posts on here and have to admit I misread one post. Has to do more with my dyslexia, as I simply substitute a word and thus have read another reasoning as was told. Haven't anything to do with my English. Now I see you don't argue the clothing protection function, as I thought you did. I try to do this in simply language. Also my last course on mathematics was about 1.5 years ago, so forgive me as something isn't totally scientifically noted.

Now, we should go further with the mechanical explanation of riveting, as that's what you're after, aren't you. I mean, how all forces work on the pieces and where they differ from a regular washer. First, we have to start with the simple law action = - reaction. This simply tells you that when you add force on something, the same force will be replied to it. So, if you have your rivet on your support and use your hammer to bounce onto it, it will give the same force back to the hammer. Okay, that's the first force that is working on the system.

Next, we have a rivet made of soft metal, which, under the above mentioned force seems to change his shape. The force added will try to compress the rivet, but that doesn't gonna work, so the rivet will be bounced to the sides and lock into the washer. Not, this is all the same by any kind of washer. But now we gonna look closer at what a regular washer will do and what the washer we discussed here will do.

First, the regular washer, is flat and thus can hardly move in horizontal direction (that is in the direction of the sheet). Also, only a small piece (relative) of the rivet is in contact with the washer. Now, this result in a change of shape of the part of the rivet 'above' the washer. Most force will thus be used to reshape the washer. Now we look at the Bell-cap.
First we have to see we here have a piece that has a slightly bigger contact surface with the rivet. We also have a form that can a bit easier change his shape. If we now add force to the rivet and want it to devide to the sides it will both reshape the rivet but also reshape the washer to the shaft, more as the 'normal washer'. Also, as the shape of the washer is a dome, when adding force to the rivet, you also add some force to the washer, as it is at the same surface as the rivet. This means that there is even less force needed to peen all together.

Here is where Brian estimates that he only need 10% of the force needed by a normal washer. of course we can set up a system to measure this, but do we really need to do so? I also feel it need much less force to rivet this way. So that is always better for all materials involved.

Hope this all is clear.