Gas Spring Calculation

[jackf]

My son and I are building our first Teardrop. It has been very fun. But I am have trouble calculating the size for my gas springs on my rear hatch. Due to space limitations and having already built my kitchen the spread sheets that I've seen don't help me. I think I need to use a flip over design. Here is what i have.

Distance from pivot point to end of Hatch 64.5"
Distance from pivot point to center of gravity 33.5"
Operating angle is 60 degrees
Hatch weight is 130#
Compressed spring length 20" +/-
Extended spring length 36" +/-
Radius of circle in drawing 3'7"

All measurements are approx. Please feel free to move things to make it work better, If you can't help me any direction on someone who can would be very appreciated.

[danlott]

The calculator that I posted should work. When I get home later tonight I will look at your drawing and try and figure something out.

Dan

[danlott]

At what point on the hatch did you measure your weight of the hatch?

[jackf]

That is total weight of the hatch. Thank You for your help.

Jack

[danlott]

I believe your numbers on spring size and geometry will work good. The big issue then would be what force of springs to use. I am assuming you have found the spring calculator that I created. If not here is the link to the thread.

http://www.tnttt.com/viewtopic.php?f=21&t=58263

You will still be able to use this calculator with the springs in the flipped over design that you are referring to.

For the calculator to work you need the total length of the hatch, your's is 64.5" (I imported your drawing and scaled it and got a length of 68.5", so make sure what your hatch length is based on your hatch as built).

Then you need the spring attachment to hinge center point, which according to you drawings would be 41.83".

The next measurement that you need is the dead weight of your hatch. This is different that the total weight of the hatch. To measure the dead weight of the hatch, the hatch must be attached to your trailer. Prop open the hatch approximately 45 degrees from the closed position. Use a prop stick and a weight scale to measure the weight of the hatch at approximately 50% of the overall length of the hatch. Refer to the drawing.



After you determine the dead weight of the hatch you will need to enter the above measurements into the spring calculator spreadsheet. You do not need to worry about putting in a value for the "Stroke Length of Gas Shock". That is only used to determine the ideal spring attachment point and is not used anywhere else in the calculator.

Let me know if you need further help.

Dan

[jackf]

Thank you for all your help. Very much appreciated. I hope I can help others with the same problem I had. I ended up ordering 2 100# gas springs from McMaster Carr and they barely held up the gate so I got a pair of 150# and they work great. Thanks again for the help.

Jack

[tituscook]

Thank you for all your help. Very much appreciated. I hope I can help others with the same problem I had. I ended up ordering 2 100# gas springs from McMaster Carr and they barely held up the gate so I got a pair of 150# and they work great. Thanks again for the help.

Jack

We are in the same stage here with our galley shelves already in place and looking at needing a similar application to mount our gas spring/shock and working through calculations. Do you have any final build picture with the gas springs installed? Enjoyed seeing your gallery build pictures, but only see wood poles holding your hatch.... unless I somehow missed it.

Linda

[Poi397]

Hello Dan,
I was able yo use your formula for locating gas springs on my galley hatch,works like a charm and I dont have a whole bunch of holes all over the place!
I used 2 springs rated at 56 lbs each,raising a weight of 65lbs
many thanks
Frank Poirier

[danlott]

Hello Dan,
I was able yo use your formula for locating gas springs on my galley hatch,works like a charm and I dont have a whole bunch of holes all over the place!
I used 2 springs rated at 56 lbs each,raising a weight of 65lbs
many thanks
Frank Poirier

Thank you for posting this information. I am glad that the spreadsheet helped you.

Dan