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Old 04-22-2013, 09:42 PM   #1
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Need Pilot 30 Lift Support for Motor Hatch

Does anyone know the replacement part numbers for the two gas lift supports that hold up that big motor hatch? Mine are about to run out of steam and it's a heavy hatch.

I can measure the compressed and extended lengths for a replacement but don't trust how I'd calculate the rated lift poundage.
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Old 04-22-2013, 11:24 PM   #2
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Here's a great resource for lifting shocks, gas, spring and electric. If you look through the site, you'll also find a formula for calculating necessary pressures, compressed lengths and strokes.

Hatch Lifts & Gas Springs
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Old 04-22-2013, 11:42 PM   #3
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From the website -

The gas spring lift consists of three measurements:
Extended Length is the overall length of the lifter with the rod out
Compressed Length is the minimum length with the rod pushed into the lifter

Rated Lift is how much the lifter will 'push'

A 15" Extended length = 9.5" Compressed + 5.5" of lifting travel (Stroke).The simple way to do this is by trial and error with a fish scale. You need to see how much lift is needed at the point where you will attach the lift to the door / hatch / cover. Remember, you will still want to have about 5-10 pounds of force on the place where you lift. You will also need to calculate the stroke and extended length of the gas lift.

For those who want to get technical, here is the long math to calculate this.
if you define: W = weight of door (in lbs) L = length of door (in inches) a = angle door makes with base at hinge (initially 0 deg, 90 deg when vertical) b = angle piston makes with base (initially 0 deg, varies with a) H = hand force applied at lip of door, and perpendicular to door Fp = force in ONE piston (assuming there are two pistons, one each side of door) - double the Fp for a single piston. A = distance from hinge to attachment of piston to door B = distance from hinge to attachment of piston to base Lp = length of piston (initially B-A for the setup you show) Sp = stroke of piston from initial position (initially zero) then: b = arctan(A*sin(a)/(B-A*cos(a))) Lp = (B-A*cos(a)) / cos(b) Sp = Lp (B-A) and the big one: H*L + 2*Fp*sin(b)*A*cos(a) + 2*Fp*cos(b)*A*sin(a) = 0.5*W*L*cos(a) now, for a given A and B you can get angle b for any angle a for a given A and B you can get the stroke of the piston Sp for any angle a for a given Fp you can get H at any angle a, or for a given H you can get Fp for any angle.

Well, that was easy. WTH?
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Old 04-23-2013, 07:43 PM   #4
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Thanks Nsail,

I found that site and calculation as well. That's what prompted me to ask if anyone knew the rating or specific springs to order. The placement on my motor hatch is really awkward to weigh at the piston mount point and that's a rough calculation to determine for the lbs rating.

I was hoping someone may have replaced theirs and knew the specs that worked.
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Old 04-23-2013, 08:57 PM   #5
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I just replaced a couple, and like yours, there is no way to use a fish scale where the attachment point is per the instructions. Calculating using their long math method seemed way too complicated, so I just weighed the whole thing and went from there. I added 20 pounds or so (I don't remember exactly) and it worked out fine.
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