Peter's Ski Press

pwskis · Post by **pwskis** » Thu Oct 14, 2010 7:44 pm

Thanks to all who post here. Your knowledge was very helpful to me during this process.

So, for a senior engineering project at my high school we are allowed to build whatever we want. I decided to base my ski press design off of Geoff's. I used 3in X 3in square tubing for the main frame and 8X12in square tube for the end blocks. I was able to get this metal from my step-dads work for free, which I am extremely pumped about. The main cost of this project so far has been the cattrack, made out of steel not aluminum, for $100, the MDF for the mold and some other tools.

I have to get two posts in before I can post pictures. It is hard to understand what I am talking about without pics. They will be coming soon. Sorry.

pwskis · Post by **pwskis** » Thu Oct 14, 2010 7:48 pm

Here are my plans and questions I have as of right now.
For my press, the next thing I will be working on is drilling the holes through all the cattrack pieces. Then I will be working on the bladder and top mold. I haven't done a deflection calculation (because I don't really know how), but it seems to be pretty strong. I intend on adding those flip up bars on the outside like Geoff's, but then again thinking about how necessary that is. It would be nice to not have to unbolt those bars each time I press a ski. Another thing I am slightly worried about is that the ladder structures are bolted down using two bolts on each end. Will this be strong enough? Once again, I am not an engineer so I have no idea how strong these are beside the fact that they are 1/2in. Thanks!

pwskis · Post by **pwskis** » Thu Oct 14, 2010 8:10 pm

I just realized that I have to wait another day to be able to post pictures. I will post them tomorrow, unless other issues arise.

pwskis · Post by **pwskis** » Thu Oct 14, 2010 8:19 pm

Finally here are the pictures:

This is my main press frame.
http://www.facebook.com/photo.php?fbid= ... 1123395481

I bolted down the top and bottom ladder like structures (which are poorly welded together by me) to the end blocks using a 1/2in bolt.
http://www.facebook.com/photo.php?fbid= ... 1123395481

Recently I finished cutting all the metal for the cattrack, which was 3/4in.
http://www.facebook.com/photo.php?fbid= ... 1123395481

I also have three 10ft sections of 9in diameter, 4.5in radius fire hose.
http://www.facebook.com/photo.php?fbid= ... 1123395481

At home I have been working on the ski profile and just finished it. Here is what it looks like inside the ski press.
http://www.facebook.com/photo.php?fbid= ... 1123395481

Still have a lot of work to do, but I am getting there. I ordered ski material from the website and should be getting it soon.

EricW · Post by **EricW** » Thu Oct 14, 2010 8:27 pm

we have to be your friend on FB to see the pics. If you right click and get the pic info you can embed it on the forum.

sammer · Post by **sammer** » Thu Oct 14, 2010 8:28 pm

Photobucket!

sam

pwskis · Post by **pwskis** » Thu Oct 14, 2010 8:57 pm

Sorry about that one guys. I just made a photobucket account. Hope this works!
Here is the cattrack pieces:

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Here is the general ski press, still needs side bars:

Here is a close up of the bolt connection:

Here are the fire hoses:

The profile inside the press:

MontuckyMadman · Post by **MontuckyMadman** » Thu Oct 14, 2010 9:04 pm

yeah, nice. NEEDS side bars those little bolts bear all the load. You know that right?

BTW I have sen allot of high school mig welding remember not to back your hand away from the bead. Stay home and hot.

pwskis · Post by **pwskis** » Mon Oct 18, 2010 7:54 pm

So today at school I noticed some 1in square tubing. I am thinking about using it for the side bars, but noticed most people use 2in square tubing. Will the 1in square tubing be strong enough or should I just get some 2in? I am thinking about using a 1/4in or 3/8in bolt and having three bars on each side for a total of six. Also thinking about adding another 1/2in bolt near the ends where the other bolts are, not sure though.

I also got my ski materials and will start working on the skis at home.
Ya I am still working on my welding skills. I will probably go over a few spots. Thanks for the advice Montucky.

MontuckyMadman · Post by **MontuckyMadman** » Mon Oct 18, 2010 9:09 pm

loose the bolts man. weld it all.
You only need to put materials in from one side anyway.

The side bars will be structurally based on the sheer points of the bolts you use. 1" would be pushing it maybe but if its a thick wall and you use big bolts with 4 sheer points per bar then may be.

Others with more knowledge should chime in.
These spaceframe styles do have a tendency to rack or twist with 2 skis side by side at over 45psi. Keep that in mind.

powderho · Post by **powderho** » Tue Oct 19, 2010 3:38 pm

Great looking start PW!

I gotta state the obvious like Montucky though.....ditch the bolts and weld the crap out of it. You have four 1/2" grade 3(?) bolts taking the entire load. I think your press would fail at around 15psi just by guessing. Do some google'n on how to determine the strength of your bolts--in tension. The math is really pretty simple. Don't even bother doing a FEA of the frame, or anything like that. It's not really necessary. It's pretty obvious from your design that the 4 bolts take the entire load. The steel tubing isn't going to fail before the nuts are ripped right off the bolts. Also I would put 3 additional vertical members on each side. Just weld them to the frame on the backside and bolt them to front side.

FWIW, I have 40 1/2" grade 8 bolts holding my press together.

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Peter's Ski Press

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