How Does a Chain Wrench Function?

Simple, by the atrict force between the chain and the subject. The chain is flexible only in the transversal direction. It is capable of pulling large loads. What's your specific doubt about it? Have you tryied to use one and is having some problem?

The chain is fitted around the item to be turned and held in place by a lever which multiplies your hand force by a factor easily over 10 times...

So the chain grips the item very firmly and follows the items outside perimeter, applying force to the lever not only tries to turn the item but also increases the force that the chain grips the item - Something has to give!

The chain is unlikely to give, the mechanical advantage that the lever gives your hand means that the force applied should be sufficient, the chain is unlikely to slip due to the force pulling it together... So the only thing likely to give is the item...

John

sir, will the attraction of the chain to the cylinder will be there only when a rotational force is given by the lever or if suppose if we give a lifting force to one end of the lever
will the same attraction force will be there.Is that the same chain they are using what we are using for automobile transmission or its different.

To answer you....

the chain will only grip the cylinder when you operate the lever to turn the cylinder, the gripping action (tightening of the chain) is due to the lever action pulling the two ends of the chain together...

The chain is a low specification standard chain, as used for cheap drive chains etc... In fact an old, used chain can often be used for a chain wrench. In fact some 'chain wrenches' actually use a strap not a chain.

John.

The principle of a chain wrench will work with just about any flexible cord/strap/wire etc. The strap arrangement can be very useful for undoing relatively fragile cylinders such as filters and plastic pipe where a stilson or conventional chain wrench would do damage.

The strap is wrapped several times around the cylinder and tied to the end of the lever. The lever is placed against the cylinder, thus making the cylinder the fulcrum, For fragile materials some form of load spreader such as a piece of ply can be used here. When force is applied in the desired direction of rotation one of two things happen. Either the strap slips loosely around the cylinder or it grips. Once it grips it's unlikely to slip again as the force tightens it onto cylinder making it grip more. If it slips things need rearranging or possibly the loose end needs holding until it starts to grip

FRICTION.

A chain wrench, as opposed to the very similar, but different, strap wrench, is usually made from standard mechanical transmission chain, notably something like a bicycle chain. Unlike the strap wrench, which uses a flexible material or metal strap (might be sheet steel, nylon cloth, plastic, etc., the chain is composed of rigid links that connect and pivot at their ends. The strap wrench relies almost entirely on friction around the entire object being wrenched, whereas the chain links can somewhat resemble a large multi-point polygon wrench like a 6-point or 12-point socket, which can apply a mechanical torque at various point due to the angle of contact.

When the two ends meet, or connect by a joining mechanism (pivoting latch, lever, etc.) and a force applied to this connection, the entire chain usually becomes rigidized, due to the tension applied at each joint. On highly irregular objects, chain links might actually "catch" onto multiple points, perhaps even allowing sections of chain in-between to "go slack", and the wrench will still work. Not so with a strap wrench, which will only rub on the high points of the circumference, spanning low points and maintaining the same tension throughout. Additionally, due to the need for friction, a strap wrench will almost never work if it is wet or oily or if the item it is trying to turn is wet or oily, no matter how much tension is applied. A perfect example of this is the oil filter wrench, a type of strap wrench, which often slips if the oil filter is too oily (imagine that!).

As an extreme example, using a chain wrench to turn an old gear with many broken teeth, all that is required is for one tooth to grab onto the pivot point of one of the links, and the rest of the chain after that point could be slack, at least until the gear moved to the point where the geometry allowed the link to slip off.

The best use of chain wrenches is to turn odd-shaped items which might be mounted on a screw thread. Usually the object was originally installed by hand or other gripping tool, but over years had become worn or damaged, where the original tool no longer fit or rusty, frozen threads required a higher torque than hand gripping could apply. Cylindrical, ellipsoidal, or other rounded items could be turned with a chain wrench, however, now it acts more like a strap wrench and relies on the friction between the metal chain and the object at limited points of contact. In this case, a strap wrench is the better choice because of the much larger area of contact.

Good point re the grip on on irregular shapes. I've only used them on cylinders so it didn't leap out at me. You're right about the strap wrench on oily surfaces too. Only choice then is to use a chain wrench and turn your nice cylindrical oil filter into an irregular shape!

Just like and oil filter (strap type) wrench.