Design for portable hoist base

I've got a hyraulic hoist designed for use on a swivel base bolted to concrete. see:
http://www.camequipment.co.uk/product_detail.php?idX&list_id=2
It's actually the 500kg version, but the pic of that won't load for me.
I've built a portable base for it with 3 horizontal legs at 90 deg to one another, two are longer than the maximum jib extension and the third can be tied back to a building which becomes a counterweight. The idea is to be able to use it to lift stuff on & off boats. I've already used it successfully to lift a 150Kg flywheel onto a boat, but want to establish whether my setup will safely cope with the maximum 500kg rating of the hoist, or how I'll need to modify it to that end. The legs are 4" x 2" RHS, set on edge. Can anyone point me to how to calculate this, or even to someone who can do it for me without charging huge consultancy fees? Ultimately I may need to justify to the powers that be that it is safe, but initially it's for my own peace of mind.
Cheers Tim
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Why not do what the safety inspectors do and check it with a test load (in a safe place of course). This does rely on you being able to find a large enough weight to test it with -but water is a known density and you should have plenty of that around.
Regards
Kevin

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On Thu, 24 Feb 2005 18:54:11 +0000, Kevin Steele

The 'safe place' bit is the problem, although it's 'portable' there's actually only one spot where it's designed to operate. Trouble is, I can't leave it there for long obstructing the towpath <g> The real test is what happens when I swing the load out over the water, & I don't want to lose the whole thing into the canal :-( It's certainly worth a try, but I'd be happier with some idea beyond instinct as to whether it'll do the job.
Cheers Tim
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wrote:

Just had a thought about that one, if I built an open topped tank with capacity of 500 Kg of water (+25% minus the tank weight) I could lower it *empty* into the canal, then try to raise it *full* from the canal. There's unlikely to be a sudden dramatic failure that way.
Cheers Tim Dutton Dry-Dock Traditional & Modern canal craft repairs Vintage diesel engine service
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wrote:

.>
From my youth, I seem to remember the insurance engineers at Dad's place running tests loads at +30% of intended Safe Working Load, but it might be worth checking what the current practice is. He certainly had one machine that was designed for SWL +50%, which was apparently excessive. (30T + 50% !)
Steve
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On Fri, 25 Feb 2005 08:04:42 -0000, "Steve"

I based the 25% on the CAM website, which says all hoists tested to +25%, plus my 'new' Epco floor hoist came with a test cert which says +25%. Ideally it should be tested to the max the hydraulics will handle, plus a bit more for 'bouncing' loads etc.
Cheers Tim
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Tim
One of the methods used involves water bags hung from the hook at various jib extensions. Bags can be made easily from poly tarpaulins. With water density circa 1000Kg/m3 it is fairly easy to make a range of test weights. Hope this helps.
Ian

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