pneumatic ski press help

fouldsys · Post by **fouldsys** » Sun Feb 10, 2008 4:36 pm

so im new to ski building and im looking for some plans or even a diagram or picture i can follow to build a ski press. im hoping to make one thats lightweight(less than 300lbs), as cheap as possible, and needs easily available materials. im leaning towards a wooden one, or maybe one like the one on the howto page. any help is appreciated.

bluedog · Post by **bluedog** » Wed Feb 13, 2008 9:21 am

Have built a press that weighs less than 100lb (just) but it does not use air. It uses 20 bolts along each side with wooden bars doing the pressing. Have to shape the wooden cross bars near the tip and tail which is the only tedious bit, but it works and was cheap! It was welded up from 2 short bits of solid C-channel with two bits of angle iron on each side to put the bolts into - will try and get you a photo soon. It works!!!!!!

plywood · Post by **plywood** » Wed Feb 13, 2008 12:27 pm

my pressframe weights about 500g or so, can be folded together and i have no idea how much it would have cost - it`s made out of cloth. the cheapest and lightest way of building a press frame:

this is a pic of my old construction. i`m just sewing a new "frame" for the new mold, so more pics to come

bluedog · Post by **bluedog** » Thu Feb 14, 2008 10:50 am

You win on the lightness factor - I dont think my sewing would handle the pressure! I am still trying to avoid the pneumatic hose thing as I have seen many failures in the discharge hoses that many seem to be using. We use lots of it where I work.

plywood · Post by **plywood** » Thu Feb 14, 2008 11:19 am

the sewing is not a big deal as long as you can use a sewing machine - just sew 15 times throug it and you`ll be fine. the pressure isn`t that high as it gets distributed over a huge area.

hydrant71 · Post by **hydrant71** » Tue Feb 19, 2008 9:34 am

bluedog,

discharge hose like anything else has different pressure ratings depending
on the intended application. utility discharge hose normally has a fairly low psi rating especially in the larger diameters. fire service rated hose
is usually rated with a 400-600 psi burst pressure (some are less) and is very heavy duty compared to the the cheap utility discharge hose.
don't know what kind of hose you are using at work but i thought i would throw in my two cents so you wouldn't go away from a method that works really well.

jason

rockaukum · Post by **rockaukum** » Tue Feb 19, 2008 9:59 am

I'd second the pressure rating of the fire hose. Ours is service rated at 250psi and burst pressure at 400 (I think).
ra

bluedog · Post by **bluedog** » Thu Feb 21, 2008 3:26 am

You guys are right about the hose ratings but I am still trying to avoid using hoses and high pressure air. The case of beer that I would have to buy the fireman, in exchange for the length of hose, would cost more than the bolts my press uses!

hansonc · Post by **hansonc** » Thu Feb 21, 2008 11:50 am

Plywood-

You probably mentioned this in another thread but what kind of cloth are you using on your press? It must be something with very little stretching ability.

I wonder if you could make the whole thing a little more adjustable by using a handful of tie down straps. It would certainly add to the up front costs but you wouldn't need to sow a new "press" for each design change.

plywood · Post by **plywood** » Thu Feb 21, 2008 12:41 pm

about the cloth: i have no idea what type of cloth it is exactely

i think it was made initially for protection clothes for bikers. so it`s quite tough and resistant. it feels a bit like the material used on lashing straps, but thinner. and if you try to rip out a fibre it cuts your hand. these are all the informations i can give you about the cloth...

i doubt that you could make it more adjustable because then the tie down straps had to be capable of taking up a huge load - the main idea of such a "press" design is to distribute all the forces to the largest possible area. this decreases the load that the different elements of a frame have to withstand. so if you reduced this area the load would get bigger again and the whole system could possibly collapse in the end.

and of course you don`t have to sew a new press for every change in design - you don`t change a regular steel frame for different designs either, and it`s pretty much the same. i used the actual "frame" for 4 different designs so far and i`m still using it, now for a 5th, differnt design. there are a lot of ways to adjust such a design: if you need a tighter fit you just can trow in some wooden planks on top of the molds in the press frame.
i just built a new frame to be able to operate two presses at the same time.

hansonc · Post by **hansonc** » Fri Feb 22, 2008 8:49 am

@plywood

I guess I just misunderstood why you were sewing a new "frame". I think whenever I get the time and energy to actually build some skis I'm going to seriously look at building a frame similar to yours. Thanks!

esscher · Post by **esscher** » Thu Apr 03, 2008 7:12 am

plywood,
what is that material that you are using for your cat tracks?

esscher

knightsofnii · Post by **knightsofnii** » Fri Apr 04, 2008 7:39 pm

Plywood, have you noticed any deflection in the bottom mold?
with your design you have compression AND tension so i'm wondering about all the forces around the bottom mold and whether or not it could warp it out of being flat?

either way, its the sickest press out there, way to think outside the box. i'd love to try this method

plywood · Post by **plywood** » Sat Apr 05, 2008 11:37 am

@esscher: i`m using wood for my cat track. some leftovers i got laying arougn

for the first mold i used 15mm thick spruce plywood. for the second mold about 15-20mm thick stuff, i don`t know what kind of wood, maybe it was spruce too. just take the grain crosswise, this is the best and cheapest way. maybe for a conventional shape with tight radius in tip and tail you have to round the cat track there a little...

@knightsofnii: don`t say "NII", otherwise i`ll say "IT". and no, i didn`t use a shrubbery for my cat track

seriously: no deflection at all, my skis are still plane and even - more plane than a factory ski when they come out of the press.
but you`re right, the forces in my press are a bit weird. there are "no" longitudinal forces, all forces appear crosswise. so there is a risk of breaking the mold in two pieces lenghtwise. hope i wrote it right and you can get it.
BUT! this is the reason why my mold has just enough space for one ski at a time. so it won`t get this wide which decreases the risk of breaking it in the middle. and the firehose covers quite some width, so there is not much room left on each side of the hose. this helps distribute the forces to the whole mold.

so yeh... it`s a cheap and space saving system, but there are some limitations: you only can build presses for one ski at a time and they are a bit of a bitch to get loaded. but it fully works

knightsofnii · Post by **knightsofnii** » Sun Apr 06, 2008 9:23 am

you could probably put all the work on a stand,

wrap it in un-sewn cloth, with a little bit extra length, feed the excess thru a rod, and crank it all down with a big crank. kinda like those tie-down straps, but really wide

.

or you could just say ecky ecky ecky ecky pecang zup poing whereghppw!!

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