For the fire hose, how is it set up? I was told there are 2 hoses side by side, How did you go about clamping the ends so that it holds air? how did you insert the air hoses into it, and what kinda hose did you use?
Also, when setting it up, do you just place the bottom mold down, ski materials on it, then the hoses, then the top mold, then just inflate the bags?
depending on how big your hose is, you might need two hoses if you decide to build a press that presses a pair of skis at a time. typically, you'll want to find a 5" diameter fire hose. when it's flat, it's pretty wide and can easy cover an area for one ski during the pressing process.
you can also build a press for just one ski and make one ski at a time. this option is often times easiers, and plus, it makes the layup process straightforward.
in our current press design, we can make a pair of skis at once, but it requires two people to layup and put the bottom mold/ski materials/top mold setup into the press frame. everything weighs so much. so it might be easier to build a press that makes one ski at a time.
what you want to do is take two pieces of angle iron and cut them so that they lay across the fire hose, one on top and one on the bottom. now drill a couple holes through the angle iron and use bolts & nuts to secure them. we'll post up a writeup showing you how to do it soon.
you'll have to punch a hole into the fire hose and use some hardware, like the kind for compressors, to secure an inlet plug so that you can connect the hoses from a compressor. we'll post some instructions soon for this. it's not that difficult. the only crux is making sure it doesn't leak.
yes, that's pretty much how you do it. you might want to put some painters plastic over the molds so that extra epoxy that leaks out doesn't stick to the press.
Pat - how's your press coming along?
it isn't. I don't have time to go out and get materials right now. The week is filled with school, and weekends are spent skiing. I'm hoping to do it over march break. Gotta look around and find some places to get the material though.
Hey Pat,
I just remembered something. If you still have access to the CNC machine, then I would use that to profile your cores. It would be much easier and quicker that way.
ya, I just don't know how much I will have acess to them though. I still need to stop in and talk to the guy who runs it.
Pat: we put up a basic page discussing the bladder. check it out:
hey great job with your web site! Anyway, I was wondering how long you keep the compressor running when pressing a ski. I own a 3 gallon compressor already for odjobs, will that do the trick?
hey jedi, i keep my compressor running throughout the entire pressing. this ranges from 10 hours to 12 hours. i think my compressor may be smaller than yours and it works fine. as long as your fire hose doesn't have any major leaks any decent sized compressor will work. it'll just kick in every hour or so to keep your fire hose inflated at the designated pressure. i think if you can manage to make your fire hose completely leak free you could even get away with a bicycle pump. this was my first option (never happened due to a leaky hose) because i like to do things like a cave man.
alright cool! thanks for the suggestion!
oh... also, are hoses sized by their inflated diameter or the width when flat? thanks again!
i think they're sized by inflated diameter. for example, we used a 5-inch diameter hose and it flattens down to 9-inches:
will a small electric compressor like a 3 gal one wear out after 8 hours. thanks.
it really depends on how leak proof your fire hose is. if your fire hose has holes in it then your compressor will be constantly running for the entire hours, which i don't think is too good for your compressor. but if your fire hose doesn't have any leaks your compressor will turn on or kick in only a few times throughout the 8 hour period, which should be fine. i hope this helps.
what type of valves are used to connect the fire hose to the compressor hose?
Hey All:
I am, either fortunately or unfortunately, not a mechanical engineer. So when I look at the frame and hear about '40 to 50 PSI' required to press out a ski, I like to think that is the same sort of pressure that is in my mtn. bike tire. What am i missing?
I understand that its all about uniform pressure from tip to tail, but can't that be acheived (on a WAY less engineered-out frame) by a torque wrench and a home-made clamp press. Has that been tried yet? Seems to me that the cost and spirit of that is more in tune with the garage building scene.
Anyways, killer website and you guys are on it!
Endless Winter
Td
The frame needs to be very stong! While 40 psi does not sound like a lot, over the length of a ski it is quite a bit of force. (ie 5"x72" area at 40psi is 14,400 lbs of force pushing the frame rails apart, that's only for 1 ski, double that for a pair) While this is distributed along the rail, it is still a lot of force.
A clamp press will work, but it is hard to get even pressure along and across the whole ski.
-kelvin
Well, totally understand the PSI and how it adds up - thanks for the clarification. Have you (or anyone else) messed with a modified clamp scenario.. maybe still using drilled flat steel and a consistent pattern of clamping to acheive the same. Thoughts on a trial effort for that?
t dog
i really think a clamp press will work. it was actually my first option when i started to build skis. but when i began designing the frame i realized that you get much more out of a pneumatic press (uniform pressing and easy adjustability) than from a clamp press with almost the same amount of effort.
the thing with a clamp press is that it's difficult to get uniform pressure throughout the ski as Kelvin mentioned. but i think this can be achieved by using sand or water creatively. another drawback is that you may have to make a new top mold every time you change your bottom mold.
I have tryed clamping with a double mould. I got a lot of blisters in my hands, and compared to a pneumatic press there is not enough space for required amount of clamps (ca300kg/clamp=50-100 clamps.) and not enough time to tighten them. By the way you have done so it is time to untighten. bottlejacks would be a better option, but you would have to be very accurate when you build the molds. To even out the pressure you can use a cork mat (or even better a silicon/rubber mat if you can find one. ) If you want to experiment and develop your skills there is no good alternative to a pneumatic press.
i also would like to know what valves you use. do you have a detailed picture? the problem is, i need european standard, it might be different from the one you have in us.
And do you think a hose with about 9 cm when it is flat is enough? I don't think so. Thats only 3.6 inches! I have 10 meters, so I could put three into the press, but I would not have the height I need.
In Germany I can only find the so called "C"-hoses at ebay. is your hose an "A"-hose?
thank you!
karsten
for the valves, look at the 'bladder construction' thread, they talk about them in there.
as for the hose, 9 cm flat is not enough at all, unless you want skis that are like.... 50-60 mm thick (rough guess).
