How Much Weight A Chain Block Can Lift

should be under rated to avoid liability issues

Can you please simplify your answer

We know the average force a person can exerts in pulling the chain is 120 N so can this person lift the 3 ton load? how to solve this using statics?

Can't get much more simple than moronicbumbles explanation

"Can you please simplify your answer"?

Yes.

How'bout doing your homework yourself?

Why would the manufacture rate it at 3 tons if it couldn't lift it.

IT can, but YOU might not have enough weight or strength to pull it

You are right but what would be the use of building one that the average man did not have the strength to use. The person should not have to place a lot of his body weight onto the chain to get the load to lift. In that position he has no control of himself or the load.

Has been some discussion about pull force here.

Is this what you are using?

The type with the looped chain? This one requires 84 lbf @ 6,000 lbs.

I doubt a manufacturer would offer a mechanism that most people could not use.

can some one tell what is the average mechanical advantage a 3 ton chain block have or it depends on the manufacturer?

Well, let's see...

I will ask the question posed in #8 differently: What Type of Chain Block?

If the type shown in #8, that particular model from that manufacturer is, well, listed right there under the picture.

How are your studies coming along? Are a lot of your friends in school as well?

GA, dk. You've got the most straightforward answer I've seen so far.

Manual hoists are designed to require a force of 75-100 lb (333-444 N) on the control chain to lift the design capacity of the hoist. With the input force fixed, different hoist capacities will produce different mechanical advantage ratios.

Of course it's possible for a 3 ton chain block to lift 3 tons. That is what it's rated for. It is also possible to misuse a 3 ton chain block in trying to lift 3 tons so that untrained people or only equipment get crushed. While rigging is certainly not as complicated as some engineering disciplines discussed here, it should not be taken lightly. (No pun intended ) A 3 ton mass raised to a height of 1 meter is about 26,700 Joules of potential energy. This much energy can do considerable damage.

This one will lift 3T 15 feet with a 92lb pull: There are others here

You remember a quote by Newton (Yes, same Newton who discovered the laws of gravity) "Give a long enough and strong enough lever and a (place for)fulcrum, I will lift the earth"

So even the force of common man can lift a earth, provided proper mechanism and sufficient tiem is available.

It was Archimedes, not Newton.

Good quote but it was not by Newton.

This quote is from Archimedes

Thanks all for correcting me.

Guest, (jeeze why not sign up a be a real person?),, yeah it's a silly question. If it's a three ton block, it's rated to safely lift a three ton load, probably with a safety factor of 4. Further it will be geared so that a normal human male can, by himself lift said load.

Further it will be geared so that a normal human male can, by himself lift said load.

And if you are not then try hanging weights on the lift side of the pull chain. With enough additional weight for leverage you can pull the chain with two fingers. The big draw back is all of the additional weight hanging from the lifting point and you having to move them up the chain as they reach the floor.

Of course you could develop an overunity wheel to allow it to move on its own. Just replace the lift chain with your magic device. You will need to design in a brake to stop you overunity device before the load is pulled into the rafters.

Sorry, I forgot to login.

I take full blame for recommending the overunity device as a lifting aid. The joke seemed appropriate due to the nature of the question.

The Mechanic-

Um - I think I must have an over-unity hoist.

It doesn't have that chain loop and the only energy I exert is depressing the small disk in the yellow box.

probably a highschool student doing homework.

As many others have answered, of course it can - that is is what is made for. If excessive force is required to operate it - I would say anything more than about 25-30kg is excessive - there is something wrong with it, you are not meant to use your whole weight to make it work. There are 10 & 20T manual chain blocks which allow one person to lift these weight so long as they have enough time - the ratio is so high you actually need a team to take it in turns but it works.

The maximum weight anything can lift is that stated on its test certificate filed in the General Register. The tests will have been carried out by an insurance company's Engineer/Surveyor with a view to assessing it for indemnity insurance cover.

If a chain block could lift weight.

As far as figuring it out using "statics", go back and open up your Static & Strength of Materials textbook and study how pullys work....same principle as your lifting hoist.....

You can easily lift 3 Ton if Chain Pulley block is in good condition.In India we subject Chain Pulley Blocks to 50% overload which means we test at 4.5 Ton. But you are not supposed to lift beyond 3 Ton. Also we design Chain Pulley Blocks with Factor of Safety of 5 as Indian Standard:3832. Which means break load of C.P.Block is 15 Ton.This is just for your information. I have worked for C.P.Block mfr for 33 years.

Yes! But check what you hang the chain block from. I have seen a 1.5 Ton block hanging from under a verandah off the middle of a 3 inch x 2 inch timber bearer 10 ft long, simply supported at each end. Boards were nailed to the top side of the bearer. Safety factor? Luckily, it was only for lifting a 4 cylinder car (auto) engine.

The chain is geared, using a worm and gear, or a set of spur gears. The mechanical advantage is such that one man can pull the endless chain, and up she lifts.

The fact that the block doesn't let itself down automatically tells you that the efficiency of the gearing is less than 50 percent (I had this as an exam question once, can't remember how I worked it out). Just in case though, there is usually a way of locking the chain after lifting. This is called a belt-and-braces arrangement.

Are you refering to a "chain block" or a "chain hoist"?

Chain block usually refers to pulleys ie. blocks connected by chains in such manner that by pulling on the chain you achieve a mechanical advantage. These are not common at the current time. Most of this type unit now uses rope as the connecting medium and is for relatively light loads. An example of this would be the pulley and rope device that hunters use to lift game (deer and larger) up inorder to gut them.

A chain hoist usually refers to the lifting device which has a hoist chain which the user manipulates to raise and lower the load and also a load chain which the load is hung from and is raised and lowered. These are often used to lift engines out of cars.

Manual chain hoists are usually manufactured with a ratio which enables one person to lift the total rated load of the hoist. Don't remember specifically but it is usually around 50-70 lbs pull to raise the capacity of the hoist.

Hoists are usually not limited by the "manufacturers load capacity' in their total user capacity. Depending on the construction of the hoist they can sometimes be used above the rating. In doing so you have to exert more than the rated pull on the hoist chain to acheive this. For example, a 2-ton hoist with a 80:1 ratio would require a pull of 50 lbs., using it for 4 tons would require a pull of at least 100 lbs. (probably more due to increased load on the gearing).

The best way to determine the load capacity is to contact the manufacturer (or look it up on the web) and ask them.

3 tons for a chain block would be alot of equipment since you would have to achieve about a 100:1 ratio with blocks and chain. Thats many blocks and a long piece of chain.

There is also a device which functions as a differential pulley system but that is too long to explain here.

Good Luck, Old Salt

It depends upon the current condition of the <...chain block...>.

All lifting equipment needs to have a periodic insurance inspection record:

• If its condition were assessed as satisfactory based on its condition at insurance inspection for a <...3 ton...lift...>, then it can lift <...3 ton...> safely.
• If it were found that the block were condemned for insurance purposes on the basis of its condition at inspection, then rather than lift anything, the best thing to do would be to lift it into the metal recycling skip and leave it there. In this condition it wouldn't achieve a <...3 ton...lift...> safely.

So, it depends upon what the last insurance assessment record says, rather than anything CR4 could conceive, and this record has been withheld from the forum.