home made tie downs - spring strength?

[tanuki.himself]

In preparation for my camper build, I'm thinking of making my own tie downs - I like the happijac tie downs as a neat looking system but to get some shipped to the UK more than doubles the online price with shipping and import taxes, and I hate giving the government any more money than I have to.

I figure I can make them from 8mm stainless bar, forge a hook on one end and threaded, some 16mm stainless bolts drilled through and screwed into some 20mm x 3mm thick stainless tube - fine threads tapped into the tube will not be fully formed, but as the shortest bolt i can buy is 40mm long its not going to be the weakest link.

I can buy a variety of different strength and length compression die springs 14mm outside diameter that should fit inside the tube - the big question is how strong do they need to be, i.e. how much should they compress under what load?

 

[Dusty-NZ]

I have made some spring tie downs for my front mounts . I have figured the spring movement needs to accommodate the chassis flex of the truck .

In my case it has been up to an inch of spring travel when off road in a terrible situation . Normal use just a few mm.

I used car hood (bonnet) hinge springs under tension . (I know you are using compression) . Strong enough to be too hard to pull apart by hand , but easy to adjust with the turnbuckle. A bit agricultural looking , but that is the nature of my unit .

 

[hurc85]

Here’s another idea. He posted on expo somewhere, but I couldn’t find the post, did find the YouTube vid though.

 

[tanuki.himself]

In my case it has been up to an inch of spring travel when off road in a terrible situation . Normal use just a few mm.

I used car hood (bonnet) hinge springs under tension . (I know you are using compression) . Strong enough to be too hard to pull apart by hand , but easy to adjust with the turnbuckle. A bit agricultural looking , but that is the nature of my unit .

thanks - good to know how much movement to expect to judge the length of springs required. Tension springs would probably be easier, but i've not found anything on ebay UK that looks like it would be small enough to be neat yet strong enough to take the tension. The compression springs they sell in 3 strengths and various lengths so may be easier to choose and test, and even combine strengths to give a form of rising rate resistance

 

[tanuki.himself]

Here’s another idea. He posted on expo somewhere, but I couldn’t find the post, did find the YouTube vid though.

thanks - its a similar idea to put the load through the compression spring, and has the advantage of dual springs and off the shelf components....

 

[Mnbogboy]

U tube clip very interesting, I have access to a lot of race car valve springs and possibly can fabricate something using them.
Thanks for the idea.