:: View topic - My press design

I've been following this site and learning from everyones ideas for several months now and have finally begun my building process. I found some scrap i-beams today and was hoping to find some help or ideas on how I should build my press. I've been watching hosemans progress and I might follow a similar style for my press. The beams measure 3" X 11.5" X 108" I have two of them. I got them both for free so I am trying to use them to their full potential. Thanks in advance for any help. I'll post pictures and more details along the way.

That's great SLC. Do you plan on welding or bolting? If you weld be sure to drill some holes in the cross pieces & the plug weld them. It will ad significantly to the strength of the joint. I'll try to get a couple more detailed images on my journal to explain what I'm saying.

I probably won't have any welding access. So as for now I'm planning on bolting everything.

welcome SLC-Skis, and congrats for being the 100th forum user!!! post some photos of your press when you get a chance. we're all excited to see it.

Is that like being the 100th customer? Hooray, what do I win!!!?

I have been doing some prelim searches for a hose but have not had any success. Does anyone, especially hoseman, have any suggestions and/or extra hose that they are willing to part with?

I actually only have half the hose I need. I will be stopping in at a couple of the smaller fire depts in the area in search of surplus LDH. (Large Diameter Hose). I would just check with the fire departments in your area. The bigger fire departments will have have a shop or maitenance division where damaged hose is repaired, or discarded. That's the place you need to find. Others have found retailers online which weren't crazy expensive. It's hard to beat free though.

Just got home from the fire department logistics office and they were friendly enough to donate about 35 ft. of hose. I called and said I only needed about 8-9 ft and when I got there they handed me a huge roll. I might have to make another press. Thanks for the tip Hoseman.

So far I have most of the metal for the press frame and the hose and I have yet to spend any money.

SLC, what is the diameter of your hose? i've tried asking around my local fire depts. for large diameter hoses and none carry them.

Speaking in generalities...... LDH is a 5" hose. There are some 6" hoses out there & some people even consider 3" LDH. It's hard for me to imagine a FD that would have some. Our standard hose load has 800' of 5" hose on every engine in the department. Its what we hook to the large port of the hydrant & supply the engine it's water. I guess if all the hydrants in your district only had 2 1/2" ports then you'd use 2- 2 1/2" hoses to supply the pump instead of 1- 5" hose. You probably just need to find the right person to ask. Isn't much of life that way? Odd.

It's 5" hose. The captain that gave it to me said that 5" hose is really only about 4.5" but they call it 5". Laid flat it's about 9" and will cover any size ski that I will make.

I thought I was logged in when I posted that. Sorry.

Disclaimer: I haven't tried either of these and they might be very dangerous.

#1-

How stiff are mold halves made out of MDF? What I was thinking was that it might be possible to to away with the press frame. One inch tubular climbing webbing is rated at ~4k lbs tensile strength, though I think knots and bends decrease this somewhat. Assuming that the MDF molds are stiff enough you could place loops of webbing around them to hold them (perpendicular to the length of the ski) together when you pressurize the bladders. 15 loops would have a breaking point of ~60k lbs.

Say with your ski in the mold and the bladder deflated the circumfrence of the mold is 50" and with the bladder partially inflated 55". You could slide loops of webbing with a circumference of 55" over the mold, and maybe put some grooves in the sides of the mold that face awar from the ski for the webbing to sit in.

Nylon webbing does strech somewhat so I think that this would help equalize the force, since they're not all going to be identical.

Thoughts?

#2-

Why not build an "autoclave"? I was looking at a piece of PVC pipe and it's stamped rated to 280 psi which is really high, though it's only 3" diameter. Looking at this page for some pipe company PVC goes up to 24" in diameter and 120 psi (or 210 psi for higher quality) which gives a nice margin of safety (shrapnel is bad for your health). (PVC is plastic, which means heating it makes it WEAKER, the psi rating seem to be for a pipe at a temp of 78 deg F or sort of room temperature.)

The problem with this is the pipe needs to be big enough for you, at the very least, to put a bottom mold for one ski with the ski on it (and a vacume bag you vent to the outside of the pipe) into the pipe. It seems that the largest pipe that's easy to get (say at Home Depot) is 6" which -might- be big enough thought it would be pretty tight. Though now that I think about it [help me out here engineering/physics guys] since the forces on the mold and ski are uniformly distributed the mold only needs to be stiff enough to not warp under the forces of the ski wanting to go back to flat. I just reread that last sentence and even though I don't remember my physics too well it doesn't seem right. Anyway, so having a much thinner mold might make 6" pipe work. And you could allways just chain two (or more really) of these together to do two skis at once.

Thoughts?

Mdf isn't that stiff or strong to be used without proper support. Without the steel beams, it would probably bend and break with just a little pressure. The strap idea may be good to reinforce the beams to minimize any deflection. However, there is probably more strech in the straps than the beam deflects.

I have looked into the pvc autoclave idea a while back. The problem with pvc is that it doesn't do well at even slight elevated temperatures. At 100F it only has 51% of it's original strength and at 140f it has 22%. It will start to sag and lose its shape quickly. Also the price of just one 24" pvc pipe is so much that you could build a steel presses and still come out ahead. The nice thing about a vacuum press is the mold doesn't have to be as sturdy, but you probably still need a 16" pipe to make it fit. Maybe if you can find a large steel pipe at a surplus yard, that might work better than pvc.

intresting ideas though.

kelvin