KR> Re: Gas Struts

[Larry H.]

Here is a gas strut company that says you can store or install their struts in 
any position. This page shows a diagram of how their struts are constructed. It 
seems that things continually change and get better, like KR2s.  : )
Larry H.

http://www.easylift.com/





The big end of the gas strut (spring) has to be up so the oil will be 
metered through a small internal orifice to get a smooth steady damped 
movement.  The seals do not have any tendency to dry out.  If you put the 
rod end upper-most, you will not get the damped action on extension, and 
then on retraction you'll get a hydraulic lock before full retraction is 
completed.  Take care not to scratch the rod or let it corrode; the rough 
spots will gouge the shaft seal and cause leaks.  The higher quality gas 
springs have an internal seal that peals back and forth something like 
peeling a latex glove inside-out off your hand or rolling the glove back on. 
The result is no shaft seal to leak.
For sources just do a Google search using Gas Springs as key words.  Some 
vendor sites will also show you how to size the gas springs for your 
application.
Sid Wood
Tri-gear KR-2 N6242
Mechanicsville, MD, USA
sidney.w...@l-3com.com

KR> Re: Gas Struts

[smwood]

The big end of the gas strut (spring) has to be up so the oil will be 
metered through a small internal orifice to get a smooth steady damped 
movement.  The seals do not have any tendency to dry out.  If you put the 
rod end upper-most, you will not get the damped action on extension, and 
then on retraction you'll get a hydraulic lock before full retraction is 
completed.  Take care not to scratch the rod or let it corrode; the rough 
spots will gouge the shaft seal and cause leaks.  The higher quality gas 
springs have an internal seal that peals back and forth something like 
peeling a latex glove inside-out off your hand or rolling the glove back on. 
The result is no shaft seal to leak.
For sources just do a Google search using Gas Springs as key words.  Some 
vendor sites will also show you how to size the gas springs for your 
application.
Sid Wood
Tri-gear KR-2 N6242
Mechanicsville, MD, USA
sidney.w...@l-3com.com


McMaster Carr or WW Grainger, do not remember for sure but someone sells 
valve adjustable gas struts. Open the valve and release pressure until it is 
where you need it. I have no idea what happens if you release too much 
pressure? Maybe more can be added, maybe it can't, I have no idea. I know 
someone who has one on his canopy but I have not questioned him about it.
I have been told that the big part (gas and oil end) goes upward when 
extended, the small shaft should be coming out the bottom when extended 
(inverted that is) the reason is said to be that the seals where the shaft 
comes out will dry out if in the opposite direction. If you look at the gas 
struts on auto hoods, van hatchback doors etc, the shaft comes out the 
bottom on all of them when extended.
Larry H.




From: "sidney.w...@l-3com.com" t
Robin,
Drilling a hole in the gas spring will produce an oil shower depending
on which end you go for. The oil is for damping, so you can get a
smooth, controlled steady movement. Proper operation depends on which
end is up. Welding will most likely destroy the elastic seals.
A better approach is to get the gas springs sized for your application.
The gas springs are rated in pounds force at full rod retraction. How
much PSI that turns out to be is not of any concern. As the rod
extends, the force will steadily diminish until it hits the stop; the

KR> RE: Gas Struts

[Larry H.]

McMaster Carr or WW Grainger, do not remember for sure but someone sells valve 
adjustable gas struts. Open the valve and release pressure until it is where 
you need it. I have no idea what happens if you release too much pressure? 
Maybe more can be added, maybe it can't, I have no idea. I know someone who has 
one on his canopy but I have not questioned him about it.
I have been told that the big part (gas and oil end) goes upward when extended, 
the small shaft should be coming out the bottom when extended (inverted that 
is) the reason is said to be that the seals where the shaft comes out will dry 
out if in the opposite direction. If you look at the gas struts on auto hoods, 
van hatchback doors etc, the shaft comes out the bottom on all of them when 
extended.
Larry H.




From: "sidney.w...@l-3com.com" t
Robin,
Drilling a hole in the gas spring will produce an oil shower depending
on which end you go for.  The oil is for damping, so you can get a
smooth, controlled steady movement.  Proper operation depends on which
end is up.  Welding will most likely destroy the elastic seals.
A better approach is to get the gas springs sized for your application.
The gas springs are rated in pounds force at full rod retraction. How
much PSI that turns out to be is not of any concern.  As the rod
extends, the force will steadily diminish until it hits the stop; the

KR> RE: Gas Struts

[Teate, Stephen]

"I
used two each gas springs rated at 20 pounds each. (No, my canopy does
not weigh 40 pounds.)"

This is a very good point. You don't size the strut to the actual weight
of the item you are trying to lift, it all depends on the geometry of
your design. Last year before Sun-n-Fun I built a car top carrier for my
generator out of 1/2" foam and split it so I could raise the top to run
the generator without having to relocate anything. The lid didn't weigh
five pounds, but due to the geometry of my design, my original 20 lb
strut wouldn't even crack the lid open. To get it to work properly this
year I will be replacing the single 120 lb cylinder with two 90 lb
cylinders. Most folks won't need anything as strong as this but I was
space limited so had to use very short cylinders. For canopies I would
suggest copying Langford's design and if you have any problem finding
cylinders McMaster Carr is an excellent source and they have an
assortment of mounting options and fittings that can be used at each
end.

Stephen Teate
Paradise, Texas

KR> RE: Gas Struts

[sidney.w...@l-3com.com]

Robin,
Drilling a hole in the gas spring will produce an oil shower depending
on which end you go for.  The oil is for damping, so you can get a
smooth, controlled steady movement.  Proper operation depends on which
end is up.  Welding will most likely destroy the elastic seals.
A better approach is to get the gas springs sized for your application.
The gas springs are rated in pounds force at full rod retraction. How
much PSI that turns out to be is not of any concern.  As the rod
extends, the force will steadily diminish until it hits the stop; the
force should never go to zero before hitting the stop.  You should take
advantage of this characteristic by setting up the geometry between the
canopy hinge and maximum extension and retraction of the gas springs.  I
used two each gas springs rated at 20 pounds each. (No, my canopy does
not weigh 40 pounds.)
http://www.guden.com/ItemDisplay/displayItem-GGS48-020-K.aspx I had to
experiment with the mounting points for the gas springs to get the full
canopy open position and still balance the full weight of the canopy at
about 3-inches open at the aft edge.  At closer than 3-inches the
geometry starts to go over center and the gas springs start to push the
canopy down.  That's so the canopy will stay shut sitting on the ramp
without having to latch it.
As Larry often says: "Your results may vary."

Sid Wood
Tri-gear KR-2 N6242
Mechanicsville,MD,USA
sidney.w...@l-3com.com


>I want to use gas struts for the canopy, I have 2 but the pressure is
too high. Apparenty you can increase the pressure but most struts you
cannot reduce the pressure. With the struts that you can reduce the
presure there is a valve in one end but these do not have the valve. 

I am thinking of drilling  hole & welding in a valve from a vehicle tube
has anyone out there tried this & how did you get on.  I only want about
10 -20 PSI.

Many thanks 
Robin 
New Zealand.