What are the pros and cons of fixing leaf chain using outer links?

Written by Peter Church on 24 Apr 2019

Leaf chain anchor bolts (also known as leaf chain clevises) play a safety-critical role in forklift truck operation.

Depending upon the application, they can be manufactured to a wide variety of sizes and designs.

It is widely accepted that the strongest possible connection is achieved when the leaf chain ends on the inner links and fits internally to the chain anchor, as it is a manufacturing method that ensures the maximum number of sheer faces and the greatest tensile strength.

But, as forklift manufacturers in Japan have discovered, there are also a number of advantages in fixing leaf chain to the outer links of an anchor bolt.

The pros - fewer materials means lower cost

If we take the case of a BL834 leaf chain for example, it is possible to reduce the amount of material required from 1.95kg (when the leaf chain ends on the inner links) to a finished weight of 1.10kg when the chain ends on the outer links.

That's a materials saving of 77%.

Removing less material also means there's less machining. And because the part takes less time to make, it is more cost effective to produce.

The cons - servicing leaf chain in the field

With so many Japanese forklift trucks now in use in the UK, there can be some challenges for technicians when it comes time to replace worn leaf chain in the field.

In a factory environment it is easy. As long as you have the right equipment, you can simply join the chain using a rivet link.

When companies cut the chain from bulk, they normally push the pins with a press to break the press fit.

As the rivet head passes through the chain links this can then damage the outer link - but because these links are normally thrown away when chain ends on the inner links, this needn't cause a problem.

Ending on the outer link, however, means you're leaving a damaged component on the chain which can create a weak point for a stress or fatigue failure to start.

It is almost impossible to push an anchor pin into the hole of the outer plate of a leaf chain, as it is an interference fit or press fit - which means that the hole is slightly smaller than the pin diameter.

Even if you are able to force the pin through both outer plates, the complete load of the chain will be held by just the outer links as the pin will not be touching the inner link holes.

Some companies may choose to use a smaller diameter pin which will pass through the outer links – but this will then not touch the inner links at all which could mean that only three of the seven links are taking the load on 3 x 4 chains. 

It is also possible to to ensure all links take the load by using a special last link which has the same hole diameter on the last hole as the inner links. But these will need to be made to length in a chain factory, and if the chain lengths need adjusting then this can create other challenges.

If it is necessary to carry out a replacement in the field, then the recommended fix is to cut the chain two pitches shorter (i.e 71 inner to inner) and to then use a cotter connecting link to join the chain to the chain anchors. Using this method you'll only have a slight reduction in tensile strength when compared with riveting the links.

It is important to bear in mind that you should never attempt to rivet or join chain yourself.

If you're in doubt, then the best course of action will be to seek advice from your industrial chain manufacturer. leaf chain for telehandlers

Topics: Anchor bolts

Peter Church

Written by Peter Church

Peter has in-depth knowledge of leaf chain and its applications. His 25 years experience in supplying UK manufacturing companies has given a detailed understanding of customer needs, and this has shaped the way he has taken FB chain.