Backyard mechanical press

[meremademe]

So I have neither the know-how nor the materials to construct a pneumatic press I could use confidently, so my engineering-major friend and I came up with a novel idea, admittedly with a few problems. See, he has a number of tractors; backhoes, front-end loaders and the like at his house, so he came up with the plan to build a box to contain the mold, but without a top or bottom, so basically a sheath for the mold to keep the mold from shifting side to side. Then we would press down with the bucket of the tractor (running a previous test to make sure the pressure is right) and let it set. Two problems with this. First, making sure that the top and bottom mold match perfectly with the core as to make sure that there are no gaps not getting pressure, a problem eliminated by pneumatics, and second, getting enough heat to the epoxy. I can imagine getting a few kerosene heaters to work the outside, and perhaps getting his father to weld us a metal box to conduct the heat better, but still...

[rockaukum]

Just a quick thought. When you load the pressure with the bucket it may cause the mold to shift. I don't think the bucket will come straight down. Doesn't it travel in an arc? Then you would have to make sure the pressure is spread evenly across the length of the mold. Sounds like your friends dad can weld. Have him build a press??
rockaukum

[meremademe]

Yeah the core shifting is a worry, but we figure that if we build a sheath to keep the movement of the mold only up and down, it can't move side to side. Also, if we can attach the top piece of the mold to the underside of the bucket, and anchor the whole mold setup well, we would throw the tractor into neutral so when we pushed down with the bucket, the wheels would be free to move so the load was always going down over the mold. And though I could probably find enough metal and welding know-how to build a press frame, I still can't confidently make a pneumatic press setup that I could use without thinking it would catastrophically fail.

[doughboyshredder]

Dude,

Dig a big hole. Set your mold at the bottom of the hole. Cover it with a bunch of dirt, then cover that with more dirt. Drive over it a bunch. leave it for a couple days.

[doughboyshredder]

depending on the dirt, one cubic yard should weigh about 2,000 lbs. You could get some serious pressure going on your mold if you did it right. And digging in the dirt is so much fun.

[meremademe]

I suppose that would cover the weight issue, but how would I make sure that I don't get a bunch of dirt and shit on my skis? cover them in plastic? would that even work? And I live in NH, and I don't plan on pressing these until mid-Dec, so i may find it hard to dig in semi-frozen ground... Plus, don't you need to press skis at room-temperature or above? I feel like the epoxy would bond much better in a non-freezing, non-hole environment.

[Wren Akula]

Nah, just build a press. You can do it, it's not that hard.

*Note: I have no experience building a board press of any sort. Heh.

[plywood]

i`d also say: just try to build a press. it doesn`t even have to be an extremely heavy and expensive one out of metal. if you think hard there are also solutions for wooden pressframes that hold up. there is no need for that high pressures.

your idea is nice, but it incorporates a high risk of shifting cores, not precisely aligned molds....so there is a lot of potential frustration.

[MartinJern]

or use vacuum...
if your concerned about the safety of a pneumatic press, just use vacuum.
i garantee a better result with that than any clamp or hydraulic presses and no risk of explosion.
on the other hand u would have the bigges skipress ever if u use the frontloader

Regarding the "dirt method", there were some posts about using sandbags on top of the mold, it sounds like it should work sand is pretty hevy...

good luck

[meremademe]

I know I have the materials and knowhow to build a more than competent press-FRAME, but the actual pneumatic part of the press, i.e. firehose, tubing, compressed air, is not in anyway my forté, so I feel like i would spend much more time trying to build a working pneumatic press than I would in building a solid mechanical one.
And regarding shifting cores: if I leave a fair amount of overlap w/ the sidewalls when I put them on, and then nail the extra sidewall to the bottom of the mold after I have put down the bottom piece and first piece of glass, the core shouldn't move away from the bottom. And the mold fitting nicely IS a concern, but i am looking into other options to fix it.

[rockaukum]

The air portion is quite simple.
1. Get 5" fire hose - Contact me if you need some..
2. Small pieces of angle iron - 4ea at about 18" each
3. Nine nut and bolt combos, I like nylocks
4. drill - to drill the angle iron and hose for #3
5. schrader valve (2 ea - one for each hose)
6. air compressor
That is it! If you need pictures for assembly let me know and I'll get them to you. Just make sure your frame will hold the pressure and you will be set to go and as an added benifit you will be able to work indoors!
Again, contact me if you need pics and I'll get them to you.
P.S. I assume your tractor's hydrolics are better than mine (mine leak the pressure).
rockaukum

[meremademe]

Where is somewhere I can get fire hose at a local level? I live in NH so i don't know what the options are really. If i can find some that I don't need to send away for I may try building a pneumatic. Also, I am moving to Vail in january, so my skis need to be done by then, and I don't get out of school until mid-Dec, so I only have two or so weeks to do this in. I think i am leaning towards a mechanical option because I have the materials and knowhow w/o much experimentation into a field I am not familiar with. I am looking for some rubber mats though to distribute pressure evenly over the skis.
My dad is a rather accomplished carpenter so I have little doubt he will be able to make a mold that matches the shape of the core nicely. Applying adequate even pressure is my main concern right now.

[windego]

Go hose! A press can generate over 100,000 lbs with a little compressor......scary but true. Be sure you understand the forces!