Concrete Dock Float

@seasquirt , if you see one, please grab a picture. They are definitely on my mind.

 

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McMaster-Carr https://www.mcmaster.com/products/shock-absorbers/corrosion-resistant-self-adjusting-shock-absorbers/

 

Hi DogCavalry I have changed jobs since seeing the double sprung struts, and have no photos to share, but here is a CAD for you, (the computer was on nearby when I drew it). It's not rocket science, and any half decent metal fabrication shop could make it if you supply the springs. Or make it yourself. Get small car suspension coil springs from a wrecker, or weaker springs; rear motorcycle springs would do - maybe; you shouldn't need stronger springs for that application. If they compress but don't bottom out with your weight on them, should be OK. Paint it with cold galv or get hot dipped galved if you really want to. I'd use plates of half inch, and RHS struts of 4mm wall thickness to 1/4 ", but steel rod or hollow bar would work. Not lumpy re-bar. All plain mild steel (or 4140), with decent welds, say 6 - 8mm fillets. Could be stainless if you have a big budget. Customised eyes at the ends, and it should last for years with a bit of grease on the slides. Make 3 or 4, to fill all positions, if you like.
Fallguy's suggestion would also work, and looks neat, but probably quite expensive in comparison.

 

I can definitely get that fabbed up.

 

Glad I can help. If the RH bar in pic extends longer to slip through a hole in the next LH end plate, it will be more stable and less likely to twist and jam under angular loads. A stopper at the end of that bar extension will prevent it from being pulled out of the hole and becoming mis aligned. I forgot about that.

 

Excellent.

My first iteration was damaged when a massive wave passed through the channel. A wake from a tug. The entire assembly rose enough that the forks on the ends of the lower turnbuckle exerted a twisting load on the mounting brackets when everything went beyond the available range of motion. The concrete side bracket had one 13mm SS concrete anchor twisted off. The next iteration allows free vertical motion, but now there is enough play for the float to be pushed by waves slapping on the end. Momentum is bad, when it must be stopped over a very short distance. Peak loads are high. Your suggestion removes peak loads. Total energy doesn't break things. Peak load does.

 

Almost finished. Thanks @seasquirt .

 

Hi DC, that's looking good. When done, try push - pulling it gently with a car or something, to be sure it does stuff without twisting or any other issues. The shackles may need gussets. Hopefully it is tug proof for you. Trim corners, de-burr, cold galv paint, and good luck with it.

 

It shall be done. The strut is 1.22m LOA. Weighs enough to break a toe if I drop it.

Then the float can Heave but not Surge or Sway, and Roll and Pitch, but not Yaw.

 

You will note extra reinforcing around the shackles. It is almost as if I seriously consider every word someone is kind enough to write.

 

Allrighty then, ride it like it's a pogo stick, (just kidding), then later give us an update on how it actually worked for its intended purpose. I did notice the shackle reinforcements in the pic. Hopefully it will ease the stresses of a ton of poop wanting to go its own way. Your concrete anchors may be the next weak link. Going from 13mm - 1/2" to 14mm - 9/16" may be enough bigger only just, or go straight to 16mm, and if that's not enough, 3/4" should be overkill. I hope your project is still profitable after all that extra work. If not, just look at your scenery, it's awesome.

 

The scenery is indeed breathtaking.
It should still be profitable. Compared to clearing an area of forest to build a drainage field, 2 days building the pogo stick isn't much.