Synthetic material used for very high load rollers?

[Adam HarrisParticipant @adamharris13683]

Thanks Dick – I will do that

[Adam HarrisParticipant @adamharris13683]

Ian, I disassembled the roller and found that the bearings were 6204 with a 14mm width and 20mm bore (not 5204 as I had misread, with a 20.6 mm width) and with greater surprise found that the bore through the body of the nylon or acetal wheel was 42mm, so with the bearings at each end,  the central 52mm length of the roller was entirely unsupported. I had assumed it would be 20mm throughout. Well it certainly will not be hard to improve on the strength of the roller design then! And on further inspection, because of the curved profile of the roller tread, those end parts of  the roller that are directly supported by the steel bearing, were not even in contact with the beam.

[Adam HarrisParticipant @adamharris13683]

I do actually notice from the cross section diagrams in Technica Wheels website that all similar purposed rollers have basically the same design of a large bore void unsupported through the centre of the roller. Strange.

[Adam Harris]

On Adam Harris Said:

Ian, I disassembled the roller and found that the bearings were 6204 with a 14mm width and 20mm bore (not 5204 as I had misread, with a 20.6 mm width) and with greater surprise found that the bore through the body of the nylon or acetal wheel was 42mm, so with the bearings at each end,  the central 52mm length of the roller was entirely unsupported. I had assumed it would be 20mm throughout. Well it certainly will not be hard to improve on the strength of the roller design then! And on further inspection, because of the curved profile of the roller tread, those end parts of  the roller that are directly supported by the steel bearing, were not even in contact with the beam.

Which is just what I said yesterday.

Ian P

 

[Adam HarrisParticipant @adamharris13683]

Indeed

[Adam HarrisParticipant @adamharris13683]

So why have all these rollers got such large voids in the middle? Is it that they are made out of cheaper tubes (less material) rather than solid rod?

[Ian PParticipant @ianp]

I doubt they are machined. probably moulded to save material.

Ian P

[Adam HarrisParticipant @adamharris13683]

AI search says such rollers are generally manufactured through injection molding

[Ian PParticipant @ianp]

The large void is not a problem if the rollers are used in accordance with the manufacturers specification. In this case it is the hoist manufacturer that has chosen the wrong item.

Making copies in Acetal might be a satisfying experience and it is harder/stronger material than Nylon so a copy made to the same dimensions would certainly outlast a Nylon one, but I dont think it worth the effort.

Anyway, since the outer ends of the rollers are in mid-air (because of the crowned profile) there is no point in them being there. Modify the existing Nylon parts by moving the bearings closer together and reducing the roller overall width by about two thirds, that should get rid of (most of) the flaked off damage.

There is nothing wrong with these commercial rollers when used correctly, in this case the hoist manufacturer has made a bad choice.  If the track was as wide as the roller (or it was running on a flat floor) then the whole face of the roller would be supporting the load, a static load is one thing but running up and down a track the roller will be constantly flexed and the cyclic bending under load will eventually lead to the nylon developing cracks resulting with the sort of failure you experienced.

Regarding your earlier mention of the trolley rocking or swaying with a heavy load, I’m not sure a wide roller will make a noticeable difference.

Ian P

[Adam HarrisParticipant @adamharris13683]

Thanks Ian for that explanation. Certainly makes sense.

[Mark EasingwoodParticipant @markeasingwood33578]

They look remarkably like pallet truck rollers, as used at the front of the forks.

There are some HERE (82mm x 80mm with 20mm bore bearings, 700 kilo load)

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