Alright alright alright. i have not heard about anyone venturing down into autoclave territory. but maybe i havent been looking hard enough. has anyone posted about a home brew autoclave that wouldnt cost a fortune?
would it be possible to construct one using just a huge PVC pipe ( maybe 2 foot diameter or bigger even), then basically just have a threaded end that can cap the pipe on both sides. and then a air compressor connection that can fill and pressurize the pipe. that would be the basics of it. i wonder what kind of PSI those threaded caps are rated to.
the skis would probably need to be under vacuum before going into the autoclave, so one more hose coming in the pipe for the vacuum bag. and then maybe a heat blanket as well, so one more entry in for some electrical wires
I wonder how challenging it would be to build. an autoclave would have incredible versatility to make all kinds of parts besides just skis.
thoughts, resources, info?
has anyone posted about this before, or anyone heard about making an autoclave out of plastic pipe? most that i have seen are made out of steel which is way more expensive and look very time consuming to build, and heavy.
Homebrew autoclave?
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petemorgan(pmoskico)
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NinetyFour
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kiln?
Also maybe looking for some information. I have access to free local Black Poplar and Yellow Poplar, and would like to build a Kiln to dry some of it out as opposed to air drying it for a few months, even though as I understand it air dried wood is much better...
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twizzstyle
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This has in fact been brought up a number of times.
Basically for skis it makes zero sense. For other projects? Hell yeah, I'd LOVE an autoclave. With skis, it's easier to just go with a firehose, and that's all you're after is pressure.
Yes of course you'd still have to vacuum bag, an autoclave is nothing but an oven without the vacuum bag. Normal vacuum bagging you get atmospheric pressure (~14.7psi at sea level). But stick it in a pressurized chamber, and your atmospheric pressure goes up.
But having a chamber big enough for skis, at upwards of 50+psi, just sounds scary to me. I'd want it metal, and I'd want it thick. A firehose is safer, easier, and cheaper in my mind.
But... as I said, for other projects... I've had this in the back of my mind for a few years now. I do a fair bit of other composites stuff (or at least I used to, not so much these days) and an autoclave would have been loads of fun!
Basically for skis it makes zero sense. For other projects? Hell yeah, I'd LOVE an autoclave. With skis, it's easier to just go with a firehose, and that's all you're after is pressure.
Yes of course you'd still have to vacuum bag, an autoclave is nothing but an oven without the vacuum bag. Normal vacuum bagging you get atmospheric pressure (~14.7psi at sea level). But stick it in a pressurized chamber, and your atmospheric pressure goes up.
But having a chamber big enough for skis, at upwards of 50+psi, just sounds scary to me. I'd want it metal, and I'd want it thick. A firehose is safer, easier, and cheaper in my mind.
But... as I said, for other projects... I've had this in the back of my mind for a few years now. I do a fair bit of other composites stuff (or at least I used to, not so much these days) and an autoclave would have been loads of fun!
Here are some photos of my autoclave that I've been making skis in. Maybe not the ideal way to make skis, but a way none the less. It also provides flexibility on design options, since it can do cap (or hybrid cap-sidewall) construction without having matched top and bottom molds.
http://www.facebook.com/media/set/?set= ... 343&type=1
http://www.facebook.com/media/set/?set= ... 343&type=1
I can't take credit for the entire project. I bought the project off a guy that built it when he was in graduate school about 15 years ago. He really did the hard work. He found the pressure vesssle and had access to a shop that was able to cut the end off. He had the custom flanges made and welded on. He also worked out the details of adding the recirculating fan and getting the rotating motor shaft to work and not leak when passed through a heated, pressurized bulkhead. He wanted to build snowboards using prepregs and Rohacell cores. Althought he hadn't done anything with if for a few years, he had made about 6 boards with it and moved it to two different houses (no small feat it is 11'6" long and weighs 2300#) before he sold it to me.
When I got it home I completely reworked the heating and duct system, moving the heating elements to under the false floor enabling me to get the longer ski tooling inside. I redid the electrical system bringing it up to the national electrical code, added digital temperature control (it had an older analog system) and a VFD speed control for the 3 phase recirculating motor. An acid etch of the inside to clean up the light surface rust that would get on everything, and a high temp aluminum epoxy paint really brightened the whole machine up. Essentially I touched every part other than the pressure vessel/door and motor assembly.
There have been a handful of other small changes made since the photos you saw; additional valves, gauges, thermocouples etc, the things you learn about a tool when you start using it. Right now I'm working on monitoring the systems with an Arduino micro-controller and LabView. Eventually I will be able to control the cure cycle, adjusting the pressure and temp, from a LabView routine. This will also enable me to monitor, adjust, and shut down the system remotely over the Internet. All from the comfort of my iPad at home...
When I got it home I completely reworked the heating and duct system, moving the heating elements to under the false floor enabling me to get the longer ski tooling inside. I redid the electrical system bringing it up to the national electrical code, added digital temperature control (it had an older analog system) and a VFD speed control for the 3 phase recirculating motor. An acid etch of the inside to clean up the light surface rust that would get on everything, and a high temp aluminum epoxy paint really brightened the whole machine up. Essentially I touched every part other than the pressure vessel/door and motor assembly.
There have been a handful of other small changes made since the photos you saw; additional valves, gauges, thermocouples etc, the things you learn about a tool when you start using it. Right now I'm working on monitoring the systems with an Arduino micro-controller and LabView. Eventually I will be able to control the cure cycle, adjusting the pressure and temp, from a LabView routine. This will also enable me to monitor, adjust, and shut down the system remotely over the Internet. All from the comfort of my iPad at home...
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skidesmond
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Re: kiln?
If you're air drying outside it's about 1 year. If drying in your basement/garage it's a little less. Run a dehumidifier too. From my readings on drying wood, air dry is better in the sense that the wood may have a clearer look to it when it's, mostly a concern for furniture makers, the ones who really care about what they make. Not sure it makes much of a difference for ski building.NinetyFour wrote:Also maybe looking for some information. I have access to free local Black Poplar and Yellow Poplar, and would like to build a Kiln to dry some of it out as opposed to air drying it for a few months, even though as I understand it air dried wood is much better...
Autoclave - Serious hardware!
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petemorgan(pmoskico)
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Nice autoclave! how thick are the walls and what kind of steel was used?.. and to OP when I looked a big thing was that pressure vessels of that size have to be ASME code stamped if they operate at or over 15psi.
Anyways if I remember correctly PVC violently shatters when it splodes in to shards when it fails.. you really want metal
Anyways if I remember correctly PVC violently shatters when it splodes in to shards when it fails.. you really want metal
i moved from press to autoclave two years ago as we are doing this for low volume runs of various models :some autoclave advantages include:use for more than just skis,---- graphite ski boots?---no large heavy bottom & top die to build for each ski ,possible to stack many cookie sheets (cassettes) in same space as one set of press dies,able to quickly shim standard cassettes for different rocker and camber ,able to see through bag to see lineup of layup ,cap construction is easy if wanted, vessel ASME thickness guidelines can be obtained from propane tank mfg or air compressor mfgr
ps. our old press is for sale for $2800.00 and includes steel roller table,
ps. our old press is for sale for $2800.00 and includes steel roller table,
read articles on debulking composites. you don't want the topsheet to pinchdown on edges and stop resin evacuation make sure your vacuum lines and bleeder paths have good manifolding flow to all areas at pressure,make sure you have ample area of breather past edge of topsheet to soak up resin- (double up breather in perimeter outboard of layup)-monitor vacuum reading as psi is increased,( a drop in vacuum will indicate bag leak).also low psi vacuum breather material will squish down and not manifold your vacuum air around your part at high pressure,
( will not allow a place for resin to go) ---we use autoclave Airweave N-10 , a heavier 10 oz/sq yd white polyester fiber that is used for higher pressure cures 400°F temperature resistance.--
looking at the humidity Epoxies and many other resin systems absorb moisture from the environment, (which turns to steam )as the laminate is heat-cured. That causes micro-bubbles which may coalesce into larger voids. As a guideline, materials should not be exposed above the humidity and temperature limits of 65% at 18C (65F) to 45% at 23C (75F).------ if all else fails another possible test is to put a pressure intensifier plate ( layer of stiff ski shaped aluminum tapered down to edges (or tapered rubber) placed over the topsheet that extends only to the start of the cap curve---this will provide slightly more evacuation psi to the center large area on the top first than the cap side wall area :(saw your pictures)(danger--look up autoclave explosions) be careful as resin may gas off and be dangerous -- wrapped our heat blankets on "outside "of autoclave and then insulated over that for no electrical ignition source in volatile autoclave atmosphere ----we have had sparks from heat blankets where minor abrasions were found----good luck and becareful
( will not allow a place for resin to go) ---we use autoclave Airweave N-10 , a heavier 10 oz/sq yd white polyester fiber that is used for higher pressure cures 400°F temperature resistance.--
looking at the humidity Epoxies and many other resin systems absorb moisture from the environment, (which turns to steam )as the laminate is heat-cured. That causes micro-bubbles which may coalesce into larger voids. As a guideline, materials should not be exposed above the humidity and temperature limits of 65% at 18C (65F) to 45% at 23C (75F).------ if all else fails another possible test is to put a pressure intensifier plate ( layer of stiff ski shaped aluminum tapered down to edges (or tapered rubber) placed over the topsheet that extends only to the start of the cap curve---this will provide slightly more evacuation psi to the center large area on the top first than the cap side wall area :(saw your pictures)(danger--look up autoclave explosions) be careful as resin may gas off and be dangerous -- wrapped our heat blankets on "outside "of autoclave and then insulated over that for no electrical ignition source in volatile autoclave atmosphere ----we have had sparks from heat blankets where minor abrasions were found----good luck and becareful
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I've been thinking about this as well. Frankly, beam presses scare the shit out of me, there's too many possible points of failure, and the failure modes are potentially catastrophic.
I'd stay well away from PVC, though. Maximum rated / burst pressure goes down fast with pipe diameter *and temperature*. For a 12" diameter schedule 80 pipe, maximum pressure rating is 230 psi at 73°F (15.86 bar at 23°C), but it drops rapidly as temperature increases - 50.6 psi at 140°F (3.48 bar at 60°C). It's not rated for pressurised use *at all* above 140°F.
That's for plain schedule 80 pipe, in perfect condition. Scratch it, you've got a failure point. Threaded joints require derating by 50%. Non-hemispherical end caps are liable to be seeing between 50 and 100 times the pressure you're nominally applying to the tube walls.
PVC autoclave for skis? It's a 10 foot long pipe bomb.
I'm currently talking to some mates to see if I can't lay my hands on some 12" id steel water pipe. A 2m long flanged pipe should be able to "fall off" a site somewhere, which just leaves finding some hemispherical end caps.
I've been thinking about this as well. Frankly, beam presses scare the shit out of me, there's too many possible points of failure, and the failure modes are potentially catastrophic.
I'd stay well away from PVC, though. Maximum rated / burst pressure goes down fast with pipe diameter *and temperature*. For a 12" diameter schedule 80 pipe, maximum pressure rating is 230 psi at 73°F (15.86 bar at 23°C), but it drops rapidly as temperature increases - 50.6 psi at 140°F (3.48 bar at 60°C). It's not rated for pressurised use *at all* above 140°F.
That's for plain schedule 80 pipe, in perfect condition. Scratch it, you've got a failure point. Threaded joints require derating by 50%. Non-hemispherical end caps are liable to be seeing between 50 and 100 times the pressure you're nominally applying to the tube walls.
PVC autoclave for skis? It's a 10 foot long pipe bomb.
I'm currently talking to some mates to see if I can't lay my hands on some 12" id steel water pipe. A 2m long flanged pipe should be able to "fall off" a site somewhere, which just leaves finding some hemispherical end caps.