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The full unit is shown here. It has a box frame which uses four pieces of 2 inch angle iron
for the vertical support structures. They are 6 ft. 8 in. tall and are connected at the top
and bottom with pieces of quarter inch plate.
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The plates at the top and bottom were cut from 6 inch wide flat stock mild steel. Each plate
has 4 bolts connecting it to the vertical pieces of angle. The base uses two additional pieces
of angle to give the unit good stability and balance.
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The top of the frame looks identical to the bottom with the same size plates forming the box.
Each large plate is 14 inches wide and the small side plates are 4 inches wide.
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The vertical angle pieces have 1/2 inch holes for the support pins. They allow both the
top and bottom press decks to be ajustable. The pins are made from 1/2 inch stainless
round stock to give them very high shear strength. This picture shows the upper press deck from behind.
The upper pins receive the load stress when the hydraulic jack pushes from below. The lower pins only
serve to support the weight of the upper press deck while the jack is inactive. The holes in the vertical
angle struts must be very accurately placed to allow 1/32 inch of clearance for the press deck between
any 2 adjacent pairs. This means that when the jack is activated, it pushes the press target (perhaps
a stinger missile or fountain) up until it contacts the upper press deck. The upper press deck will
then ride up 1/32 of an inch until it contacts the upper pins. Then the real business of compressing the
press target can begin.
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Here is a Google sketch-up of the upper press deck to illustrate its
construction. It is built from a piece of 3/4 inch flat bar attached to the bottom edges of a pair
of 4 inch channel pieces. The straps on top only serve to keep the deck square, but are probably
not essential to the structural design. The bottom press deck is constructed exactly the same way,
only with the flat bar on top.
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The compressed-air-driven hydraulic jack sits on a piece of 1/4 inch plate mounted to the top of
the lower press deck. This unit is a 20 ton jack, but a smaller one would probably be more
appropriate. My hydraulic load cell can only measure a range of 0 to 20,000 psi. All of my pyro
projects only need half or less of this range. I fully expect that this jack could seriously
bend or break its frame if I ever tried to use all of the force it is capable of exerting. Thus,
I would recommend a 10 or 12 ton jack instead of this one. Another benefit of a smaller jack
is that the smaller cylinder would travel faster, saving pyro project construction time. This
jack moves very slowly and requires a lot of patience to use. However, I'd still rather wait
for this jack to do its job than return to manually pumping the jack on my previous press.
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The jack has 2 retraction springs that bring the cylinder back down when the release valve is
opened. The springs attach to eye bolts at both ends that connect to the cylinder platform at
the top and the lower press deck at the bottom.
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The jack can also be activated with a manual pump, but you'd have to twist my arm pretty hard to
get me to use it after being spoiled by the air drive motor shown below.
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This view shows the air motor that drives the hydraulic pump by connecting the pressure line to an
air compressor. My hat is off to the guy that invented this sweet little jewel. It has saved me
from a lot of stress and strain on my aging bones.
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I added the red valve knob to the release valve. This makes it very easy to open the release valve with
a little twist of the wrist.
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The cylinder platform is a very thick piece of aluminum round stock. It is attached to the cylinder with a
single countersunk bolt through the top.
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This is a shot of the upper press deck from the front. It shows the hydraulic load cell attached to the bottom
of the deck. This gives me the means to very accurately measure the force being applied by the press on its
target. There were two possible choices for implementing this feature. A fairly popular one is to disassemble
the jack and drill a hole into the pressure chamber through the base. The hole is then tapped with threads and
used to run a line to a gauge. I chose the external measurement system shown for several reasons. First, even
with a 4 foot cheater bar on a huge plummer's wrench, I was not able to unscrew the top of the jack. Second,
with my custom machined load cell, I was able to design a system that would indicate applied force without
having to make a difficult math conversion.
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The Helicoid gauge has a large face for easy reading. I bought it on eBay for about 25 bucks. It probably cost
considerably more originally. I love to find a good deal.
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This picture shows the load cell from the back side. The cylinder bore was designed so that its surface
area is exactly 2 square inches. This means that a force of 20 pounds applied to the cylinder head will
register as exactly 10 psi on the gauge dial. All I have to do is read the dial and double it to find
the actual force being applied to my press target. Pretty slick, yes?
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Here we have yet another view of the entire upper press deck assembly from the rear.
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This is a final shot of the lower press deck assembly from the rear. I hope the visual views
and the verbal explanation have been sufficient to illustrate how the machine is designed and
built. The entire project cost about $200 in materials. You can buy a similar shop press from
Harbor Freight, but not with all the bells and whistles. Of all the tools in my pyro shop, this
one is one of the most useful.
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