"Four Ton Jack"

[Cursitor Doom]

I've just bought one of these:

Pity I can't get across from a mere photo how dinky this thing is for a claimed 4 tons. I recall having 4 ton hydraulic bottle jacks in the

70 and they were very hefty & robust affairs. This isn't. So...

Should I be worried? Are mechanical things getting smaller and lighter rather like electronics have been for decades? Have the laws of physics changed, enabling the design of flimsy looking things to bear great weight?

Your reassurances sought.

Cheers,

cd

[Brian Gaff]

Surely you need to spread the weight. I cannot see it but I can well remember some chain my father got which was supposed to be about 5 ton, and it could not even take the strain of one end of our car. the welds in the links busted. Maybe there are Chinese tons?

Brian

[pcb1962]

In the past machinery was reassuringly over-engineered. Nowadays every gram of metal used in production has to be justified to the bean counters, so nothing is any bigger or stronger than it absolutely has to be.

[Davey]

I worked once at a Steel Mill near Shanghai, which produced steel in those large rolls that you see on the backs of lorries. They typically weighed about 12 tones each, give or take a ton. I once saw a lorry at the side of the road, outside the canteen, and it had ten of these steel rolls in the box at the back. The lorry had one front axle, and one rear axle, so even if the load had been spread evenly, each axle would have been supporting about 60 tons. As it was, the rear axle was probably supporting 100 tons or more. I kept well away from the whole thing.

[Mr Fuxit]

I heard of her, but never met her.

[newshound]

SIP is a well known brand. I would be very surprised if it did not have this rating, with a pretty reasonable margin. The thing with bottle jacks is that it is *very* important to get the load accurately aligned with the jack: they will tip over very easily. Not a bad idea to bolt them to a larger base plate to give you better stability.

In tension, a piece of even the cheapest steel 10 mm diameter will support four tons.

[Tim Watts]

It will lift 40kN if the base is welded down to a 1/2" steel plate under the object to be lifted, the top engages into a cup and the object to be lifted is laterally restrained in all directions...

[Tim Watts]

On 06/07/14 16:23, pcb1962 wrote: justified to the bean

Type approval should be

"Lift 4 ton truck, insert bean counter's head, leave for an hour".

Then they'd be over engineered.

[Cursitor Doom]

I'm pleased to hear it. I just bought a milling machine and the lifting eye it comes with has an alarmingly slim stem of no more than that!

[Gazz]

Would they be multiples of wontons ? :)

[Vir Campestris]

Look at the links. They do a 12-ton model that looks identical!

Andy

[Cursitor Doom]

Perhaps the jacks are all identical; they just put different labels on them and charge accordingly?