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RE: [PSUBS-MAILIST] Big acrylic dome problem
Darek,
I agree with Jim and frank that forming a dome from flat plate has the best
price and quality.
But... it is not easy. Before we controlled the process (of a 580 mm, 40 mm
sheet acrylic dome), 3 or 4 pieces of expensive material were destroyed.
1500 mm is maybe too big as you have to start with 80-100 thick sheet and
need a 2x2 meter oven. Maybe start with a scaled down one to practice??
All the best, Emile
-----Oorspronkelijk bericht-----
Van: owner-personal_submersibles@psubs.org
[mailto:owner-personal_submersibles@psubs.org] Namens Dariusz Hoffmann
Verzonden: vrijdag 6 juni 2008 20:12
Aan: personal_submersibles@psubs.org
Onderwerp: [PSUBS-MAILIST] Big acrylic dome problem
Hello everyone,
my name is Darek, I'm 27yo, I'm from central Europe
and I always wanted to build a sub.
I am curently on early stages of designing my sub (something similar
to XPC15 by Marlin Submarines, but smaller) and I have a problem with
with a front window. It should be a dome of acrylics 70 mm thick and
1500 mm (59") inner diameter. 125-135 deg. Thats a big window. After few
weeks of sending questions to dozens of acrylics manufacturers I am sure
that it is a serious problem. I found only one company that is capable
of making the thing - blanson ltd. Estimated price £12,000 to £14,000
(about 23600-27600 $). There is another one in UK - Stanley Plastics,
but i think the price would be similar. That price is just too high for
me. It is even higher than the cash i plan to spend on the whole sub!
Right now I am considering making the window myself. Worm forming of a sheet
is not a good idea because of the thickness of a sheet. So there are two
possibilities: molding in a form or creating a cube and machine it to a
dome. Since I have minor knowledge about the polymerization conditions
of acrylics it would be difficult for me to make it this way.
So here's the crazy idea. Take, lets say, 20 thick flat sheets and
join their surfaces
together using the acrylic cement. This cement is not a glue, it softens the
surfaces of acrylics and fuse them together creating one part. The bond
is transparent. This will form a cube. Next it should be taken on a big
lathe and machined into a roller. The roller should be machinned to a
half-dome and then machinned inside to create a dome.
The possible crossviews of the dome are with bonds on x OR y axis
depending on the
placement on a lathe.
(Which one of these would grant a better visibility / strength ?)
I read that two parts joined this way will be fused to one part. But I
think that there has to be some loss of strength. What is the exact loss
- I do not know. 10-40% ? Tests on smaller parts should be made..
Thickness of the dome can be increased much since that is no problem for a
lathe...
In Busby's book there is a sub with an acrylic sphere made from
octagonal parts joined together. Stresses are different there I guess
but I wonder can it be done the way I described above.
What do you think about this idea ?
Do you have any other ideas of how to make it / where to buy it ?
Thanks for all your thoughts
Darek
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