On Monday, December 9, 2013 3:46:42 PM UTC-5, wrote:
I have an old (1972?)semi-clamshell type trailer. When open, 4 gas struts hold the "lid" up. Two look like original equipment from Germany and two from an, apparently defunct, company (Colmar Gas Springs) in Pennsylvania. In cold weather the hatch won't stay open. Any idea as to how to determine the lifting force necessary for new struts? I didn't see that number on the existing struts but it may be there. I was able to get the P/N off the American struts, thought that's all I would need and stopped looking. I found out today they were a two person company and the phone number doesn't work. The trailer is now 300 miles away in winter storage so I don't have ready access to look for more numbers. No rush, the spring ridge season is a long way off.

Grainger carries Bansbach Easylift gas springs. I replaced gas springs on my homebuilt trailer because they kept bending when trying to close the top.. Called Bansbach in Melbourne, FL and found out they only sold to business resellers i.e. Grainger et al and a minimum order from them was 1k. But, spent about a half hour on the phone with one of their engineers discussing the issues I was having. He recommended several options for replacement gas springs to replace the new ones I purchased from another company, that company was much less than helpful. As a note, Grainger was not very helpful either when I went to the local store with the damaged gas springs. But they do have a lot of choices they can order for you.

Was toying with linear actuators (electro-mechanical) but after some comments here, gave that idea up. Will get some cables made for both sides of the lift mechanism to limit the extension of the gas springs. Worked this weekend. And put the top down slowly.

Bansbach website has an page where you input measurements and it provides the gas spring required. but you need to do a lot of measuring and know the newtons/lbs required.

Still like the linear actuator idea though

r/Jim
N9XL/H-201B