Vacuum Pot Options

[Sailor]

I am seeking a Vacuum Pot for degassing resin.
No doubt everyone already knows the following, but I do need to confirm my thinking with you - as I don't know what I am doing, and the little I do know is from reading.

Option 1.
My engineer will make a pot from a steel pipe 218mm ID x 400mm tall, welded (sealed) to a 6mm base plate, for $120.
Perspex 250mm x 250mm x 20mm is $12. They cut a circular grove to fit an 'O' ring matching pot rim.
Not sure what sized pump. I need one that will work reasonable quickly.

Option 2.
150mm PVC pressure pipe approx $37 L/m, end caps pretty cheap, and perspex negligible, but I think too small. (what do you think)
300 ID x 6m Length is $380, end caps $57, so between 12 blokes be around $100 each. (got to get the cuts straight tho)

Option 3.
Vacuum Solutions sell
36 Litre Degassing Chamber Kit - $790 + gst (Ex stock, Melbourne)
Pump to suit above - LC12/240V - $1,090 + gst (Ex stock, Melbourne)

12 Litre Degassing Chamber Kit - $536 + gst (1-2 weeks)
Pump to suit above - LB4/240V - $710 + gst (Ex stock, Melbourne)

Conclusion:
Without doubt Vacuum Solutions (Option 3) is the best by a long shot, except for the price.

Option 1 (steel pot) seems better for me, if I can get a suitable pump at a suitable price.

So my Q now is, what size pump for the job? I see a lot of them on ebay but I am not sure what I am doing. I do need something that will work quickly balanced against price.

Thanks everyone.
Cheers
Phillip

[mangozac]

I'd go with option 1 also, although do you really need 400mm high? That's going to be a 15L volume (I use my 10L pressure pot as a vacuum chamber).

Earlier this year I bought one of *CFM (Cubic Feet Per Minute) vacuum pumps from ebay. I've been very happy with it. It pumps my 10L pot down to a good vacuum in around 20 seconds. It will be a bit slower for 15L (maybe 40 seconds or so - the time to evacuate a chamber is not linear) though. Going up in flow rate from there gets pretty pricey very quickly.

[ValueGear]

My friend made me some steel pots and I use neoprene seal and 20mm acrylic top... it is heavy but I will not ever need a new one... affordable and durable...

here is a video of me lifting the pot by the lid... the pot probably weighs 15 pounds or so... We build model tanks so he made it like a real tank...

I went for the smallest and most durable pot for what I am casting. vacuums fast and strong... all of my molds are small. so the suggestion of maybe not needing it as 400 mm might be a good suggestion. depending on what you plan to cast.



Steve
www.valuegeardetails.com

[Sailor]

Thank you both for your replies.
That 8 CFM pump on ebay is the exact same one I was looking at, (and trying to match with the chart you put up on another thread).
I was looking at 400mm tall as each yacht hull should weigh around 850gms. I read that when degassing, the liquid can triple it's cubic capacity. Add to this, if the whole op works (and that is a big unknown), my roto set-up could do 2-3 hulls at a time. However I will re-think the 400mm height bit.

Thanks for the video. Interesting.
As a side issue, I was a soldier for 9yrs, and last months of my time got posted to Armour (well, the Tankie School as the Chief Clerk) so I enjoyed driving the MII3. I recall being in a strange wagon called an M41 at some stage too - (fast). In VN the M113 was a workhorse for us, well, along with the Mk3 Inter Truck and the Slick. Long time ago.

Cheers
Phillip

[Lane]

I had a vacuum chamber built from a design stolen from the Yahoo? Casting list.

It's made from 10" dia. 1/4' wall steel pipe 20" long. One end was turned on a lathe to get a straight edge for the sealing surface. There is a 1/4" plate welded on the bottom and another at the mid point creating two chambers, one sealed the other open on top. Pipe nipples are welded on the side of each chamber. I use a 1" acrylic lid but will replace with Lexan when I get a chance.

The advantage of this system is I can draw a vacuum in the lower chamber then open the valve to the upper. This allows me to pump down the upper chamber almost twice as fast.

By using a 10" dia. pipe I can fit most (model sized) molds inside if I need to.

[mangozac]

Hang on a minute. So you're planning to degas the resin before pouring it into the mould? Are you certain that that will be necessary? My understanding was that the agitation caused by the roto-moulding would disperse any bubbles in the resin. I haven't done it before though so I may be wrong...

Have you tracked down a suitable resin yet? Who are you dealing with? I highly recommend Barnes in Woolloongabba - that's where I get all of my supplies from.

Lane's systems sounds excellent: shows what you can do with access to the right tools and materials

[Sailor]

mangozac.
Yes, I was going to degas before pouring into the mould, and then rotate.
Checked Reps notes and he advises try without degassing, so thanks for raising the issue. I completely missed it. I will let you know how I go.

I am dealing with Era Polymers, Meadowbrook 4131.
The reps' very helpful
Ordered a 4kg Kit Eracast TL65D at around $22 kg (tooling grade urethane, UV, min shrinkage).
plus his Salease (1kg $26 approx) to line mould for release.

I went to Barnes. The lady was really helpful, but knew little of roto-moulding.
I went to a US Company and they knew all about it - made resins, rotational caster machine etc. The Aussie agent was Barnes who didn't stock this line. I did learn this roto-moulding is also know as Roto-casting, Resin-casting, Slush-casting etc.

I am flying by the seat of my pants here, so every comment is appreciated.
Cheers
Phillip

[mangozac]

Yeah roto-casting isn't anywhere near as popular. I'm glad you've got someone who can give you some good advice with regards to materials.

Perhaps you could start a new thread documenting your roto-casting adventures?

[Anvils Hammer]

I plan to start playing around with rotocasting to make a line of very cheap one peice tank hulls, but that wont be till next year, so in the meanwhile very interested to see what process you are using and the results!

AH