Ski Builders Forum

I recently acquired a steel I Beam from a friend, and after reading up a lot on the site, decided I might as well give ski building a shot. Because I have steel on hand, I figured I would build a pneumatic press (although it clearly isn't as simple as a vacuum bag, especially considering my lack of real engineering knowledge).

The beam I got is:
Length: 204"
Depth: 6.75"
Web Thickness: 1/2"
Flange Width: 12"
Flange Thickness: 3/8"

I plan to model my press after Head Monkey's. Here is a link to my (poorly drawn) plans (note that I left space between the beams in my diagram to the lengths I will use).

*Edit* Because of my low post count, I can't post links. Please copy/paste the link below into your browser.

My plans:

img806.
imageshack.
us/img806/6190/mypress.
jpg

I plan on bolting my beams together in the same way that Head Monkey did his. I will be using 1/2" grade 8 steel bolts paired with 2 grade 8 nuts and loctite.

The one change: because my beam has a wide flange (12"), I will only have one section of beam running length wise on the top and bottom, not two skinnier beams.


Here are my concerns.
1) The beams will deflect in the middle
2) The bolts will shear (I don't think this will happen since I don't plan on pressing above 70psi, but if a kind soul could help me with the mathematics I would really appreciate it )
And my final question,
3) Will the 6.75" cavity height be large enough to fit the fire hoses, mold, and ski materials?

Obviously, safety is my first priority. If anything about this design seems blatantly dangerous, please suggest what changes I can make in order to ensure that my press will be both functional and safe.

*Edit* Here is Head Monkey's press, for those unfamiliar with it.
http://www.skibuilders.com/phpBB2/viewtopic.php?t=485

CAPTAINoCRUNCH wrote: And my final question,
3) Will the 6.75" cavity height be large enough to fit the fire hoses, mold, and ski materials?

I have not read anything other than this. Yes you can make skis like this but you will be limited in tip rise.

The answer is no in my opinion.

I really didn't think it was enough room, 12" looks like it should be my minimum.

Here's a new question.

What would happen if I used two beam sections as spacers instead of simply one section of beam? That would double the cavity from 6.75" to 13.5" which should be sufficient room. I would bolt the additional meeting points the same way as the original joints, however I'm not sure how this would effect the press' integrity. Adding more joints would just make more places for it to fail, would it still be safe to operate?

http://www.engineersedge.com/standard_m ... erties.htm

Look at this list and tell us which beam section you have first.

Stan

IMO You can use that cavity size to press if your molds are 1" thick, top and bottom and you use no larger than 7" lay flat firehose with 1/2" cat track. That would leave you approximately 1.5 to 2" cavity. Plenty.

but you will be limited to the rise of your tips to about 7cm at most with cassettes, ski materials and blankets. make it bigger, trust me I did this once before.
We made ours 15", overkill in retrospect but its easy to fill the gap with sheet goods.
12" is plenty.

12" is what I'll aim for then.

In response to what beam it is, I can't locate it on the chart as my friend had it custom milled for a home improvement project.

It is 36 lbs/ft. however, so wouldn't that make it a W7x36, seeing as the beam depth is 6.75"

That beam is a little short for complete open span I think. You can put a midspan support and be sure. You can download beamboy or similar to calculate the deflection at the desired psi.