spring shackle design question

[KCStudly]

I kind of assumed that there would be some stabilizer jacks involved, but that would require diligence on behalf of the operator.

I suppose that for the typical stepping in and stepping out load transitions while not underway, the tires would be compliant enough to absorb any transitional loading, and the bound up spring might not be a worry.

Might want to be sure that the shackles never butt into the guide tubes at the fully loaded state so that the carriage can extend a little further if the spring wants to flatten out some more with load changes.

In travel mode the shackles pivot like normal, but it is a valid concern for loading and transitions when lowered/parked.

Angib, you always see what should be very obvious, that most people do not see. You have "The Knack".

[48Rob]

Andrew,

Thanks for your thoughts!

There is about an inch of free travel once the shackles are collapsed, before the weight would push on the outer tube.
If it turns out that is not enough, I can trim the tubes back a little.
With this design, in travel mode the tubes will be locked with a pin system. In the lowered position, the trailer will either be parked at camp or in the garage.
If at camp it will have the stabilizers down, so occupant weight/movement shouldn't be a big factor.

Unlike the first design/plan, I don't have the option of towing it in the lowered position, because of the potential strain on the tubes...as well as the low ground clearance.

Rob

[MtnDon]

Clever. My major concern would be about lateral movement; will the long shackle have too much side to side movement? That can be reduced by "boxing" or bracing the shackle.

example:



Sometimes one whole side, or most of it, is covered with plate and welded.

I have seen long shackles on vehicles exhibit lateral movement when under way.

[48Rob]

Hi Don,

Good point.

I've studied shackle length pro's-con's, and found that, as you know, longer shackles can move laterally. It can be limited by boxing as you have shown, or with a bolt and spacer (not as strong).
Allowing a little movement can be good as it can reduce the stress caused by twisting, such as when one side (wheel) is extended down in a pothole or similar, and the other side is up.

On most vehicles, the spring and shackle mounting includes rubber or polyurethane bushings, which allow some twisting to limit stress to the mount points.
On a trailer, or at least mine, I have only bronze sleeve bushings.
You probably can't see it in the video, but I have drilled holes in the center of the shackles for support bolts...just in case.
The new shackles are 2.5" longer than the old ones, for a total of 6".
1" to 1.5" longer than stock seems to be the generally acccepted line where bracing the shackles starts to be recommended.

Thank you for concerns and time helping me off line, and on! I'm learning a lot from a lot of people on this project

Rob

[angib]

It would be fairly easy to add some truck bump stops right above the axle in the down position, so that the spring can't flex - it might also be a benefit in making stabilisers less important.

But as there won;t be any dynamic loads on the spring, I guess it doesn't need much help.

[48Rob]

Andrew,

There won't typically be any dynamic loads on the springs in the down position, but I may cut just a little more off the outer tubes, so in the case of a failure to rise... the trailer could be pulled while in that position.
Having the bump stops is a great idea, and may save me if we pull into camp one night and am too tired to deploy the stabilizers!

Thank you for your help!
This is going to be one cool trailer!

Robert