I'm looking into building the frame. I have a metal supplier near enough to me that I can get metal, but it's not super cheap. Do you think that using a 4x4 of a hard wood would work for the frame (and be cheaper)? cause I can easily get that, and I think it may work.
I would perfer using wood if it will work, as I have a wood shop in my basement, but it's not exactly cut of for metal working right now.
i've heard of others using wooden pneumatic press frames but i'm very skeptical of how safe they are. at the very least you could combine some of the wood with some steel tubing to help increase the strength of the frame.
but you mentioned using 4x4 hard wood. what kind of hard wood are you looking at? it may even be more expensive than steel tubing. also it doesn't take much machinery to work with the tubing. a jig saw and a powerful drill (a drill press is even better) are all you need.
I am not positive on what type of wood I would use. However, my friend bough some 4x4 steel tubing from the supplier I'm going through, around 20 feet in total, for $100. Seeing as I may need 3-4 times that amount, that's an expensive frame.
I'm waiting to hear back from the supplier though, and I will talk to them about my options.
I think that the best stiffness-and-strength/prize ratio is achieved with steel I-beams. Not without reason they use I-beams in buildings. If you use wood you can get a pretty stong press to, but it takes a lot of wood glued together. Pine is stong and cheap here.
I know I can get i-beams, the question is, for what I need, will it be the best solution as far as cost goes?
Here's the design I came up with. It uses the same type of steel 2x2 tubing around the edges (if it's not obvious, the black pieces), 4 hard wood 4x4 pieces of wood, with a plywood top. Now, the dimensions are the same as the one in the press frame link (I believe little kam's, the all black steel one). Is that for pressing 1 ski at a time, or two?
Do you think the frame will be strong enough (I do, but I want other more 'expert' opinions)?
Also, I can order some HDPE for the top of the work surface (the plywood on the top of the frame) at a very good cost, and I've read elsewhere (I believe grafsnowboards.com) that the HDPE will not bind with the epoxy, so I figure it will make for an ideal work surface. Should I do it?
(PS, ignore the 'wheel' in the fron left, it was left in by mistake, but I will have wheels on it at the end)
http://newschoolers.com/PHP/Pictures/Uploaded/3002press_frame1.jpg
by that I meant the INSIDE dimensions are the same as the INSIDE dimensions of the other one.
hi pat,
the inside dimensions of my ski press are just guides. i would first measure the width of your bladder (at it's widest point) and also the intended height of your molds. then i would make the press geared specifically towards these dimensions so that your equipment will fit into the press. it may turn out that my press dimensions are too small for your stuff.
after looking at the press design (nice rendering by the way) i'm thinking there may be a problem. you see, the top and botton wooden beams will still bend. this is because there is nothing really strong or stiff connecting your steel cross members. the vertical distance between the wooden beams will stay the same because of the steel members but the overall shape of your press under operation will look like a person grinning. you'd be surprised as to how much pressure just 20psi is and what it can do to wood. if you substituted the wooden beams with something stronger then i would say the frame is okay to use.
the hdpe is a good idea. if you can get your hands on some i would use it to line the molds as well like Big Kam and Kelvin do. i can''t seem to find some so i'm still using the painter's plastic method.
my work surface is actually just some cheap 1/8" thick material (1'x8') I bought from Home Depot. i covered the surface with some plastic tape and epoxy doesn't stick to it.
Thanks for the input. I'm still looking to find some better materials for the press. Do you reconmend building the molds first? I was just gonna buidl the press frame, then the bottom mold, and just cut the top mold so that it all fits, but if you say build the molds first, I guess that's what I'll do.
I know where there is some like 1.5x.15 galvanized aluminum (or it looks like it) tubing I can 'take'. Would that work at all better than wood?
you don't have to actually build the mold first. but i would finalize the dimensions of the bottom mold, however, before you begin building anything. just as long as the inside height of the frame has more than enough room for the mold (especially the tip and tail portions) then you'll be fine. you just fill up the excess room with a bigger top mold.
but do keep in mind the width of the bladder. especially the point at which you apply the clamps. if you build the frame too small for your bladder's width then you're pretty much screwed. for the style of press you're making, the bladder length doesn't matter too much. just make sure it's longer than your mold length by at least 6 inches on both sides so you get adequate coverage.
here's the order that i built my stuff:
1. bladder
2. press frame (determined by bladder width and rough estimation of mold dimensions)
3. bottom mold
4. top mold (built to fill up most of the excess volume of the frame after mold, bladder, and materials are inserted).
just remember to take your time and measure carefully. another good option for you since you seem to be handy with the CAD is to simply draw everything up beforehand to check the fit. it's a good way to prevent mistakes. i'm assuming you'll CAD most of the stuff anyway.
Galvanized aluminum or steel? If it's aluminum I would say probably not. But if it's steel then I would say it's okay. My press uses 2.0 x 0.08 steel tubing - the kind you tubing see in home fencing. But I'm not a metal expert. Perhaps someone else with more experience can chime in on this one.
hope this helps!
where did you get the steel tubing? because I check home depot and they had none. I know of a couple fence places around here that I could go and ask about buying some if that's the same type though.
the tubing at Home Depot is in the fence section. try looking where they have the chain link fencing. they come in 78" long sections and are already pre-painted white or black. over here they cost about $13 for one.
Well.... went looking around today, and ended up going to a Dept. of Trans. near my house and looking throuhg their scrap pile.... found 81 in. long 4" wide x 6" high x1/4 thick steel ibeams.... and a lot of them. Gotta go back for a few more tommorow, but I have all the material for the press now, for free (luckily no one was there!!).
So ya, I'm revising my design in pro/e and I'll have pics up whenever, just make sure you think it'll work.
nice find dude! perfect length too! i always wanted to make an I-beam press but the cost (and weight) always got in the way. let us know how the I-beam press construction works out.
there's the newest one. i-beams are all 4 wide x 6 high x .25 thick steel. the only thing I'm not 100% sure will work is the space between the i-beams and what that may do to the molds.
But ya, suggestins to improve it/make sure it will work?
i'm sure the press will more than enough.
but i'm curious, what's the reasoning behind the spacing of the i-beams? why not just put them side by side to get a 12" wide solid frame? i'm not sure, but if the spacing is too large i think the high pressure may do some damage to the molds.
what I wanna have is a press that cam press 2 skis at a time. is 12in wide enough for that?
perhaps Big Kam or Kelvin can jump in on this one because they have a press designed for 2 skis at a time.
my press measures about 8-9 inches for the inside width and it's just for one ski. i wish i had about 2 inches more room but that's just me. i'm sure 12 inches will be fine unless you plan on making super fats. remember that it's preferable to have your materials overlap the ski's edges a little bit during layup.
Here are two pics of the steel. not all is the right size (I was sloppy while taking it cause I was worried about who saw me doing it). I have one less than I need, so I will go grab that sometime. some are slighty bent in places, but all have a flat side that is usable. I weighed them, and they weigh 60 lbs each. I will be using approx. 9 of them, meaning around 500-550 pounds.
damn, i'm jealous.
hey Pat. the press that Kelvin and i have is 16-inches wide, and it accomodates 2 ski. the widest we've made so far is around 150mm. if you're planning on making reasonably wide skis, i'd recommend making your press wider than 12-inches...
nice I-beams, by the way!
I'm thinking 8 inches per ski, for 16 inches wide total. I have enough metal for that, and if that's what you have and it works, I'm definitly doing that! The 12 inches was before I went and got another load of metal.
And ya, if you have a D.O.T. near you, go see if they have these i-beams laying around in the scrap pile, cause they're pretty stanrd for holding up gaurd rails in my area, so there are tons.
Here is an album of today. We got the press frame all built today, and it's looking mighty fine. Gonna spray paint it so it looks nicer this week, and get some caster wheels and wood for a work surface, then I'm getting the hose this next weekend, and I should be able to start on the molds.
3.5 weeks till school starts, I'm hoping to be able to make a ski by them.
link didnt work for me
wait now it does
thats sweet
nice. that's the cleanest way to make a press frame in my opinion. nice gorilla steeze by the way.
Well, realized today that I'm a fucking idiot. The length INSIDE of the press frame is 72 inches... or 180 cm. Definitly not long enough for making skis that are 182-185 cm long... SOOO... I'm left with the task of figuring out how the hell to rework it so that it works... I've got a couple ideas, and I'll be working on figuring it out today as my car broke down and I can't go to work...
all that work just to have it fucked up.
Move your short cross beams back, so they overhang. Then bolt from the front of them. Do this for the nose/tail cross beams and it should give you an extra 2-3 inches on the inside .. as far as I can tell from the pics.
that's actually what I decied to do... it works fairly well and adds 4 inches to it... which should be enough.
75 in = 190.5 centimeters
with 4 inches for the hose to hang over beyond that. It'll work!
Cool man - good luck
J
All done with the frame!!!!!
Now onto the molds.
check out the pictures here:
i've never built a press before, but you could 'salvage' some staight pieces of steel from abandoned train tracks. just an idea...
that stuff is super heavy, but I did 'salvage' some perfectly sized i-beams from a DOT junk pile near my house.
haha well i guess i shoulda read all the posts before replying :P
I was looking at your building frame and it looks like a nice job, I see a dangerous weak point though which will limit your pressure or cause failure. It might be that I was looking at an incomplete picture but I saw 8 bolts joining the upper and lower sections together. If you have 10*72" of clamping surface with a pressure at 60psi then the tension in each of those 8 bolts is 10800 lbs. I don't know the size of the bolts but if they are 1/2" bolts you would need 32 bolts joining each of the halves together to safely pressurize the frame. You could also work at lower pressure but your frame overall is quite strong so you probably want to work at higher pressures. email me if you want some recommendations
Tony
how serious of a problem do you forsee this being? are we talking the press blowing apart?
I was thinking about adding some clamps of some sort on it while testing it, do you think that would be a good solution to the problem as well?
Technically, those bolts should hold, but I would still tend to agree that you should use more bolts. Bolts are pretty cheap compared with the fresh pair of pants you will need if any of them blow apart. Some of the nuts I used on my press weren't of very good quality and they blew apart while I was pressing the first time. The press still held together because of the way it is designed, but when the nuts failed, there was enough energy released to lift the hole press frame off the ground about a half an inch. Not to mention the fact that it sounded like a gunshot.
Right now I would not go over 10psi until you add more bolts. The two halves will blow apart, they are not likely to go anywhere but if you have a pair of skiis in there you are going to have to do some mighty fast bolting. The clamps might help but the stresses on the clamps are difficult to predict so the more direct route of bolting has more predictable results.
Another alternative is to weld the two halves together. You have lots of bolts joining the long pieces to the transverse pieces, try and get the same number on the two halves so it will be of equal strength. If you tell me the number of bolts and the diameter and grade of bolt I can tell you the maximum pressures that you can use.
By the way, our press is wooden, and we have made 4 skis so far without any issues in that regaurd.
Nothing wrong with wood at all its just a matter of using the materials in an effective manner. The comment on the bolts is just pointing out the weak link in the steel assembly, since the total forces on these presses is in the range of 20 to 40 tons the 8 small bolts will yield at about 18 tons so they are substantially undersized. Normally you don't want the bolts being stressed more than 1/2 their strength which is why I suggested that the number of bolts be increased to 32 whish is exactly how many bolts join the longitudinal sections to the transverse section. Have you got a picture of your wood frame, that is what I'm making.
I agree with the last post there, I got scared when my 32 M10 bolts started stretching at around 40tons (parallell press), so I drilled up the holes and changed them with M16, now I'm really on the safe side though..
Better safe than dead
origanally I had more bolts in the design, and all the holes are drilled for them, but I loose 3 inches of ski length if I do it, making the max length of the skis around a 178 or so. I guess that's fine and it will make the total bolts around 16 on each side ( a couple of the bolts can't go through because of how to steel is bent), so maybe that would be the best thing to do?
Pat that sounds good, I made the assumption that you were using 1/2"bolts when we last talked and 32 of those are perfect for all the pressures that you are talking about. If they are 3/8" bolts reduce the pressure a bit say aabout 35-40 max so you don't run into the situation that Endre described in the previous post. Like he says better safe than dead although I'd still test it with no ski inside and cover the whole thing with a blanket in case a bolt lets go. These are big loads we are dealing with.
Tony
^at what pressure do you run your press?
I have to apologize for my tardiness in writing up my synopsis of our ski building
adventure. So let me at least write up a summary of our press construction and
some of the lessons learned.
My son Cal (*Armada*) and I started putting together the materials for making
skis after he found the SkiBuilders.com site last summer. I figured this would
cost me a few hundred bucks and a few weekends of work and maybe we might have
something skiable but at the least Cal would learn some about design and
implementation of a project. I underestimated on counts. I'm in for over two
thousand dollars, 4 months of weekends (and many marital points), and Cal
learned enough about planning, design, implementation and materials to make
him more qualified than many of the recent college grads we interview at work.
Cal is a high school junior probably headed for a Mech. Engr. program at SUNY
Binghamton. I'm a software guy at Hand Held Products (bar code scanners and
PDTs).
I had no idea where to find I-beams for a press and I'm not the type of person
to ask around so I decided to try an alternative approach. I-beams seemed like
tremendous over-kill. My bicycle tires hold 100 psi, why would I need so much
steel?? Fortunately, while I may be ignorant, I'm not stupid. One of the few
good things about getting older (I'm 55) is that you have alot of time to work
on problems at 4 a.m. when you can't sleep. The important thing to consider
with PSI is that it is pounds PER SQUARE INCH. The square inches need to be
measured as the area of where the air bladder touches the press. Don't think
only of the area of the ski. For us this was about 6" by 80" = 480 sq. in. for
one ski. If you want to press @ 50 psi then the resulting force is 24000 lbs,
or 12 tons. 12 TONS - holy cow! I was humbled and chagrined that I had been
misdirected by my gut feeling. After many nights of night sweats imagining
catastrophic press failure I decided to go ahead with my design but to beef it
up some.
The basic design is apparent in the picture Cal posted.
MATERIALS
18 2"x6"x8'
20 16" angle iron
20 3/8" x 24" threaded rod
80 3/8" nuts (doubled up for strength)
6 24" angle iron
lots of screws, nails, and washers
The press was designed to be wide enough to be able to press a snow board
also. First I nailed the 2x6s together. I used 5 nails through each plank into
the next. (If I were doing it again I would use construction adhesive and
double the nails.) Cal then sanded the top and bottom where each angle iron
would straddle to ensure flatness. Next we laid out some cinder block to
support the press. (It is outside since we don't have a shop or garage.) Ten
of the angle iron were attached to each of the two beams with 3 screws in each
through holes that we drilled. 7/16" holes were drilled through each end
of the angle iron, just outboard of the wood, for the rod. One beam was placed
on the cinder blocks and the other was propped up parallel to first with about
11" inches of clearance between the beams. The six angle irons were then
attached to the sides with 24 screws. These support the top when it is used as
a table. While they may add some strength to the press they shouldn't be
relied upon, however, they may help prevent twisting of the press under
stress. The rod was then inserted in there holes and the nuts were threaded on
(doubled). Each rod was placed under a little tension to try to even the load
so no rod was carrying more than its share when loaded. Now came the fun/scary
part: pressure testing. The important thing to remember here is to mimic how
the press is to be used. You want to test with the air bladder contact patch
to be the same as when you are pressing the ski. We used 2"x10" boards to fill
about 9 of the 11 inches between the beams. The air bladder was in the
middle of the stack. Slowly and from a safe place we ran the pressure up to 80
psi and left it there for a couple hours. This step is very important!!! Make
sure you have some safety margin. Cal's mom would castrate me if he got hurt
by flying pieces of a shattered bolt. Even now, after 4 skis, I still jump a
mile when the compressor comes on. We pressed our skis at 55 psi but this is
probably overkill. I'm going to add some more rod/angle iron to the frame
cause there is some deflection/arching across the beam. I have an old bed
frame I'm going to use as a source of angle iron so I'll just have to eat the
cost of the rod.
Tomorrow I'll post pictures of my skis but let me say now that they are
awesome!
Nice looking press. When Kam and I built our press, we considered using wood, but after some calculations and luck, we went with steel. We found steel beams at the scrap yard that was cheaper than the wood for a wooden press. It's nice to see different presses. How much deflection are you getting?
Binghamton is an interesting place. I've been there many times as my sister went there and my uncle teaches physics at SUNY.
-Kelvin
[quote="Wheezer"] The important thing to consider
with PSI is that it is pounds PER SQUARE INCH. The square inches need to be
measured as the area of where the air bladder touches the press. Don't think
only of the area of the ski. For us this was about 6" by 80" = 480 sq. in. for
one ski. If you want to press @ 50 psi then the resulting force is 24000 lbs,
or 12 tons.
Don't forget about the other side of the bladder. It pushes down with the same force as the top surface presses up so the tension in your connecting structure (bolts and angles) is double the above calculation.
In your parts list you mentioned that the rods were 3/8" but elsewhere you mentioned 7/16". If they are 3/8" at 50 psi you are getting very close to the maximum bolt strength.
You guys have some good ideas in the press, I really like the support bars so that it can be used as a work surface and the threaded rod is nice so that the overall height can be adjusted for other projects.
Has anyone confirmed that we need such high pressures, I'm wondering if the high pressures are squeezing out to much glue leaving not enough epoxy for a good bond. Most snowboards are made with vacuum presses so they are working to a maximum of 10-14psi. Epoxy manufactures websites are not specific but say only use enough clamp pressure to squeeze out the epoxy. I work in the boatbuilding industry and these kind of pressures are only used with pre-pregs and autoclaves. Is is a matter of getting the ski to conform to the mold at the tip and tail? or is it trying to squeeze enough epoxy out to create a light ski?
ive talked to a guy that runs a ski manufacturing business out of jackson, WY. Theyve been operating for 10 years, and are currently running approx. 120psi and making mass production quality products....this seems high to me, but apparently it doesnt squeeze out all the epoxy--maybe they use a progression where they increase pressure as the spoxy cures.
Is the guy from igneous skis? They make pretty stuff. If he is, I'd be interested in how they treat their wood sidewalls and top sheets. You should bribe/beat some more info out of him.
