Alternatives to Lexan????
 

I am looking for some different material options. I have found that 1" think Lexan (polycarb) is beaucoup $$$. This will be for my integrated barb top block.

I am looking at using acrylic as an alternative...I know that DangerDen in particular had lots of trouble with cracking when using a acrylic top. Does anyone know where exactally they were having trouble with the thing cracking? My guess would be around the pipe threads...the taper would put alot of force on the plastic. If this is the case I might just try the acrylic route.

Ok, I am still looking for some economical alternatives to polycarb assuming that the acrylic is going to give me problems. Anyone got ideas? One key point...I would like to be clear...or at least very translucent at a thickness of 1/4" (6mm)

Thanks,
Zymrgy

I got 1/4" polycarb sample sheets from McMaster, relatively cheap.

As I've pointed out, methylene chloride can be used to seal the cracks, in polycarbonate. (see link in the Radius thread)

So I plan, when I figure it out more accurately, to use Weld-On #4 adhesive, available from Delvies plastic, which contains methylene chloride (a carcinogen, BTW), to glue two sheets together, to make a 1/2" top, and use some of it to seal cracks in any openings I make.

Otherwise, BlackEagle recently told me that there may be some deals on polycarb (Lexan) available on EBay right now.

Another alternative to the barb taper problem is to remove the threads from the barbs, and just epoxy/seal them in. You could also re-thread with straight (non-tapered) threads.

Bob

Or do as I have done on any acrylic that needs a barb... use acrylic tube that is over sized.

You will need to sand a taper on the tip so you can force the tube over it. This makes a VERY tight seal for the tube (read: no clamps) and is easy to seal to the acrylic... just glue it.

I always drill the hole the same size as outer diameter as the tube and then glue it in the hole.

All the cracks I seen from DD where screw hole cracks caused by the O ring grove not being deep enough. I never had any problems with NPT threads on any of my blocks with acrylic tops. In fact I never had a crack on any of my acrylic tops. As long as the acrylic can sit flat against the base it should be fine. And don't counter sink the screws. Use good pan head screws. I have made numerous blocks now with acrylic tops and have yet to have any problems and they do get hammered on quite a bit.

Acrylic should do fine with your block. Remeber to use metal washers with the screws so that surface area is maximised therefore not much pressure is placed on the acrylic. To furthur minimise stresses, you could cut your O ring groove slightly wider or deeper, maybe even cut it with one tool pass in the former case.

its expensive, but you need a very small amount.
if you ask nice most places will give you a small peice or two,
all the shops i have worked in would rather give away the drops rather than fill the dumpster.

I picked up 3 sq. ft. of 1/2" polycarb with a MR-10 surface hardening coating (scratch resistence is greater) for a price of $21.00 shipped to my door.:D

Gotta like it! !;)

Right now there is a section of 3/8" X 15" X 37" Lexan on half.com (E-bay). Starting bid minimum on this is 25.00, but that is a long term supply for any block maker & far cheaper than retail.

Shipping is a addeed 8.00

No real options on E-bay right now.

I believe DD used to countersink ( |_| not \_/ ) the bolts that secure the top, and this is what was causing the cracks around the mounting screws. They stopped countersinking and used 'rounded top ~ low profile' allen bolts (|== instead of the standard ones |#|== they were using...

People get cracks through user error when overtightening the barbs as well. It's best to use silicon sealant paste and do them up hand tight only, then wait for the SS to cure...

Love the ASCII artwork! :drool: :D

I wrote the programing for the 'knurling' on the allen bolt head myself :D :evilaugh: ...

For what? CNC lathe?

(|== are referred to as Button Head Cap Screws (BHCS) in the fastener industry. If you want to buy them, that's what you ask for.

Trying to familiarize myself with the terminology here.
Among all these synthetic materials, what is plexi?
"Junk used for reservoires" or can it be used for other purposes?
regards
Mikael S.