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Gas Lifters

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    Gordon HartsliefParticipant

    Hi, I have a Jurgens Fleetline L and need to fit new Gas lifters on the pop up roof after a back op and need something a bit stronger. Any Advice please.

    Regards

    Gordon

     

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    Fyko
    Fyko on

    If you change to McNaughtan’s gas struts you can (in fact you must) specify the pressure in Newtons that the strut be pressured to. You buy the strut un-pressured and they pump it to your specified pressure before they hand it over.

    Initially you may have to guess a value that may turn out not quite correct (you can increase the pressure, but not decrease it once it’s pumped), but once you get it right you’ll get pretty good service from those struts. Not that they’re rust-proof however.

    There’s a thread on this forum somewhere that I started with a procedure to safely compress a Conqueror’s roof struts (750N) in order to fit them. They are a little compressed even when the roof is fully up. You compress the strut with a farm jack and hold it that way with a clamp made from aluminium flat bar and 8mm threaded rod. You slack the nuts off to let it extend to the right length once you have the first bolt in its hole. Easy, safe, and cheap.

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    Fyko
    Fyko on

    To estimate how hard the strut must push when lifting the roof you need to know the total weight of the roof to be lifted. Each strut can be expected to carry an equal quarter of that weight.

    But the struts never lift vertically – rather they rise to an angle of about 45 degrees above horizontal, which means they each need to push 1,4 times their quarter of the roof weight to hold the roof up when they are almost fully extended.

    But you want the struts to start lifting the roof from a much lower level – you don’t want to have to help the roof up while the struts are at a mechanical disadvantage. For the strut to take up the weight of the roof at a 20 degree angle it need to push 2,9 times its share of the roof’s weight. (Bear in mind that the pushing force will increase as the strut is compressed, but we don’t really know by how much).

    So if he strut pushes 3/4 of the entire weight of the roof it should be able to lift its share from a 20 degree angle above horizontal, without being to hard to pull down again when you want to close the roof.

    The roof is weighed in Kgs while the strut is pumped in Newtons. There are near enough 10 Newtons in a Kilogram (9,8) . So take three quarters of the total weight of the roof and multiply by 10 and you should have a good starting point for how hard to pump the struts.

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    Gordon Hartslief
    Gordon Hartslief on

    Thank you for the advice Fyko, I found out from Loftus caravans and they suggest I go to a 450-500 (max.) Newtons to be safe.

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    Fyko
    Fyko on

    500N is 50Kg, and enough to cause a bit of injury if things get out of control.

    I can’t find the other thread about the Conqueror roof, but what I did was bend 2 long U brackets from 12mm x 3mm aluminium flat bar, fold the ends open, drill 8,5mm holes in the bent over ends, and connect the Us together with two pieces of 8mm threaded rod.

    I put the Us over the ends of the gas struts, joined to each other the Us with the threaded rods, and compressed the whole assembly in a farm jack until it was slightly shorter then the desired length and took the slack off the 8mm rods by tightening the nuts.

    After securing one end of the strut you slack the nuts off slowly and evenly until the strut is the right length, and voila you secure the second mounting. You can do this single handed without assistance, and nobody gets hurt.

    Sadly nobody seems able to make a strut that doesn’t rust, so any time its extended it will start to corrode, if you’re at the coast that is.

     

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    Simon Tasman
    Simon Tasman on

    That will work where there are ball-joints on the mountings, but a lot of the pop-tops have a little plastic foot secured by 4 self-tapping screws and a fork that takes a pin through a hole in a yoke at the end of the strut.

    In this case there is no room for anything to wrap around the end of the strut – you have to make a clamp to go around the body of the strut, I used a large nut that I split and welded 2 bolts to to squeeze the 2 halves of the nut around the cylinder, and then I made the end of an M6 threaded rod into a hook. The M6 rod also passes through an M8 nut welded to the clamp so it can pull the hook in, and the hook pulls the through-pin at the far end of the strut.

    You still need a farm jack for the initial compression of the gas strut because it needs a straight-line compression, or the extended strut will try to bend. You compress the gas strut with both the plastic end mounts already attached, and just turn the self-tappers in when the holes line up. Very easy to do once you’ve made the compression clamp.

     

     

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