Voit Trieste- how bad is good?

[antique diver]

Very cool diaphragm form Bill, I am going to have to look into making something similar but I think first I will play with some improvements in the LP seat area.

I hope that you can find an improvement there that I have overlooked... I sure would love to be able use the repro silicone diaphragm instead of making my own. Please keep us posted.

BTW, while you a tinkering would you try something that I meant to do while I had mine apart, but forgot to? I would like to know the suction effort required to pull the diaphgram down with the lever off... just measuring diaph resistance only. I don't really want to disassemble mine since I have it set the way I like.

[luis]

That shape of that diaphragm looks very good.
Some of the best diaphragm designs include a flexible loop (convolution) similar to the one in that diaphragm.


The shape of original Trieste diaphragm is just flawed if the desire is to have a flexible membrane.

A while back, I tested the force required to flex an original diaphragm (in excellent condition) and the newer silicone diaphragms. I placed the diaphragm on an empty can (no mechanism or lever behind them) and added small weights until the diaphragm started to deflect.

I repeated the test many times and took an average and a range. Once the diaphragm starts to deflect it normally collapses as expected from a domed structure.

I don’t remember the actual weights (I have my notes somewhere, but can’t find them at this moment), but I do remember that the weight divided by the diaphragm area was equivalent to over 1 inWC (on average close to 1.5 inWC).

If it takes over 1.5 inWC of suction just to start to flex the diaphragm by itself, it is just not possible to lower the initial cracking below that suction without a new diaphragm design. It will actually be higher once to add the force required to actuate the demand valve.

[Bryan]

Bryan, I would like to do a complete write up as you suggest. It may take a few days, as I am away a lot for work for a while. It would be nice to get a production diaphragm, as I am a little concerned about the liability in providing my handmade versions that have been requested by a couple of forum members. Maybe we should talk more about that.

thanks!

Would be happy to see what we can do with it.

[macado]

I decided to try my hand at making a new diaphragm using antique diver's technique.

So far I'm pleased with the results. I'm going to make a few more and experiment with the height and thickness. The Trieste will get a pool test this Sunday.

I also have a reproduction diaphragm from Rob however it is a tiny bit too small for my Trieste cans making it difficult to form a proper seal.

I used the trieste bottom can as part of my diaphragm mold. I didnt have time to make a fancy mold so I figured this would do It also has the advantage of fitting perfectly into the groove in the bottom can.

[antique diver]

Mike, You have done a great job with your diaphragm, and I especially like your simplification of the frame/mold concept by using the Trieste can.

I failed to even think about using the actual can to perfectly size and shape the new diaphragm, and I took off on a more complicated course of making the mold from scratch. Why the heck did I do that?

Keep up the good work!

BT

[Greg Barlow]

Very, very interesting... I am looking forward to seeing the outcome.

Greg

[luis]

That looks interesting... its got to be better than the original. At least the shape looks like it should work.