Wooden Press Frame?
Moderators: Head Monkey, kelvin, bigKam, skidesmond, chrismp
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!
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
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?
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.newmie wrote: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.
