www.TK560.com

[drcrash]

I got ahold of a copy of Nick Bryson's book, "Thermoplastic Scenery for Theatre" (Drama Book Specialists/Publishers, New York, 1972). Unfortunately, it's out of print.

That's where Thurston James got the basic design of his machine from, including:

1. Millboard bottom-heating oven with sloping walls

2. 22-gauge nichrome coil heating elements

3. Single-stage vacuum system with a vacuum pump and a water heater tank, a main ball valve, and a check valve between the main valve and the pump to keep from sucking air backwards through the pump when it's off

4. welded steel frames in a symmetrical pair

5. side-byside flip frame setup to get the plastic from the oven to the platen

6. direct edge-sealing sandwich construction platen made of 2 pieces of 3/4" plywood with 1/4" spacers in between

7. Two sizes of machine, one a quarter as big as the other (half as big each way)

There are some differences, too, including:

0. Bryson's plans are much more detailed.

1. Bryson's machine uses 36 x 40 inch sheets (or 18 x 20 for the smaller one); he was starting with 40 x 72 inch full sheets and splitting them in half, then splitting the half-sheets in quarters for the small machine

2. Bryson's oven does not use ceramic insulators, just (asbestos) millboard. The nichrome is wired to the board using short bits of extra nichrome wire. (The same 22-gauge stuff used for the heating elements.)

3. Bryson's frames are 3/4" angle steel (L profile), 1/8" thick, not 3/4 square tube. The vertical part is toward the outside. The bottom frame's horizontal part rests on the top edge of the slope-sided oven, with the vertical part coming down around it.

4. Bryson's clamping frames are detachable from the hinge mechanism, so that you can have two pairs of frames and be loading one with plastic while the other's on the oven with plastic heating. (For fast production.)

5. Bryson's smaller machine (with its own little oven and flip frame setup) sits on top of his bigger one's platen, sideways, in such a way that the larger machine's vacuum system can suck air through the smaller one's platen.

6. A foot pedal to operate the main valve. (Using a steel cable through some pulleys to a lever attached to the valve, with a return spring to pull the valve shut when you take your foot off the pedal. The lever's just a turnbuckle with the slotted metal part around the regular valve lever.)
_________________
Paul (a.k.a. Dr. Crash)

Tired of buying cheap plastic crap? Now you can make your own! www.VacuumFormerPlans.com

[jegner]

Cool!

I've been looking for that book for ages. Love to take a peek at it!

Where did you find it?

I've have a copy on inter library loan via the local university, but they can't track it down.

Jim

[drcrash]

I talked to Nick Bryson on the phone yesterday, and among other things I asked him about the ceramic insulators in TJ's oven. He doesn't see the point, either, if the coils are resting on the oven floor anyway. He agrees that they're just a waste of money if you're not putting them up on standoffs to keep the coils off the oven floor.

Since they just used nichrome both for the heating coils and the attachment wires, they strung their 40 x 36 oven for $5. (In 1972 money.)

They were using 1/4" asbestos millboard, with the coils resting directly on it (no standoffs), so the whole oven was cheap. (Asbestos is pretty cheap stuff, and great at handling heat; too bad it turns out to be carcinogenic.)

They did get some cracking of the oven floor, but only when they moved the machine around. The asbestos did not crack spontaneously from the heating and cooling, but it was fairly fragile stuff. The cracks didn't noticeably affect performance.

I wonder if 1/4" hardibacker might be a better choice than 1/2", if you support it appropriately. Since it will heat all the way through more evenly, it may be under less thermal stress due to one side being hotter than the other. (The difference won't be as large.) In general, thin stuff is more flexible and less brittle than thick stuff, so a thinner board may be the way to go.
_________________
Paul (a.k.a. Dr. Crash)

Tired of buying cheap plastic crap? Now you can make your own! www.VacuumFormerPlans.com

[drcrash]

[kayaker43]

Nick Bryson sold the book rights to the guy who sells these machines http://www.vacugenic.com/index.html I forgot his name, but tell him the Hobby-Vac guy sent you.

He reprinted and was selling them on ebay for a while. I think he may have updated it a little too?

They have non asbestos millboards now but they are $$$ You can get various types from Mcmaster Carr but they ship by truck so they are double expensive. No need for insulators if the board can handle the 1400f or so temps. I use stainless steel cotter pins in my element kits.

[drcrash]

[cod]

[kayaker43]

The Vacugenic guy wanted to send me his machine for evaluation too. (I'm bad with names, not trying to be disrespectful) He pumped me hard for info before making it but I realize he was just looking for design help so I wasn't interested in evaluating it. Nice tactic though, its smart to build on others knowledge. The dual circuit concept scares the hell out of me. I assume he researched it but I wonder if it meets code?

Really nice and intelligent guy though, apparently he has other successful products, and the construction quality looks nice.

He kept telling me how he was going to design a cheap machine that had limited but acceptable performance because most people don't need the more than that, but he would build it so cheap many could afford it. I was trying to be supportive at that point. I think he was shooting for well under $1000?

Not sure what happened there, but it started out around $2000, then $2499, and now $3499!!! He had big plans for the book too but I think he realized how small the market is from his ebay sales and lost interest?

I'm happy to sell anyones book, I sell a few of TJ's and Gingery's too, I would even be a distributor for a good affordable machine, but I expect better performance than I've seen available, and they all seem overpriced to me? I sold machines in the mid 90's but I always tell people its easy to build a cheap machine, you just can't sell one unless you work for free.

[TK 109]

woa!

hey doug!
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-Alex

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[jegner]

Thanks eveyone for the input. Great info.

Doug, good to see you here! Welcome to the board. You have a lot of adorning fans here. Great design on your Proto-form machine.

I do have a question. A buddy of mine in FL. has a Boba-matic machine. Do you have any recollections of this machine? Looked to be a commercial verison based somewhat on yours and my buddy says it was in very limited producton back in the 1990s.

I think I have a pic of it, time to look for it.

EDIT here is the pic:



Jim

[TK 109]

what was formed on that machine, do you know?

kinda looks like some trooper parts, but i dunno...
_________________
-Alex

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[kayaker43]

Hey guys, thanks for the kind words. I've been keeping a low profile the last 5 years while dealing with family issues. I'll be getting a lot more active soon, now I'm trying to decide which way to grow. I have a mountain of accumulated ideas stored away, some tested, some not. Some will find their way into new plans, and a lot I'll just dump on my website to help homebuilders.

Now I'm working on some modular heating elements that can be tiled to any size, so that may interest you guys. They will be offered to homebuilders as well as featured in a series of plans I'll do to replace the Proto-Fom as well as larger sizes.

The Proto-Form has been a successful machine and I get about a 30% build rate which is unheard of for plans. Almost all are used commercially in places like Nasa, Disney, film industry, colleges, factories etc. The new one promises to be much cheaper and easier to build with hopefully no welding? Also the old plans were costly to produce (almost 4 lbs of paper, color pics and blueprints, binder, box) I also tried to include distributor discounts so it came out way too expensive. I have a new method for plans that's more concise and intuitive and I'll try to offer them digitally for a very low cost if I can find a way to protect against theft?

Oh yeah,.. that Bob-o-matic appears to be maybe a chinese clone of a machine made by Ron Charles & assoc, in the 90's. Looks identical except for the funny name. It was called the R/C Vacuformer and came in three sizes. Nothing noteworthy about it, it used Glo-coil elements that screwed into light bulb sockets and had the usual heat issues. It also used a vac motor or two, so it wasn't a real performer either. Another case of an otherwise well built machine with too limited performance. It was pricey and sold mostly in low numbers to schools and such.

Great forum,.. I knew the internet was good for something.

[jegner]

[CJanssen]

I see that he figured out how to control the webbing issue.....

nice


CJ
_________________
"What, you think your some kind of Jedi?"

[badger]