Wooden pulleys for church bell ropes.

I have been given a job to do. There are two wooden pulleys about a foot in diameter. They have been nicely turned with a rather rough 3 inch hole in the centre.

I have been asked to bush the holes with nylon and bore a hole for the spindle. Not a difficult job you may think. However the pulleys are showing signs of splitting and I fear that if I press the nylon bush into the pulleys, they may split.

I intend to glue and screw some aluminium discs each side of the pulleys to try and prevent this. Now what adhesive should I use? Epoxy with lots of keying scratches on the inside of the aluminium disc?

The other problem is retaining the nylon bushes. I dare not have a force fit for fear of splitting the pulleys. I shall probably have the hole in the aluminium discs, such that it overlaps the nylon. Now is there an adhesive I can use to secure the nylon discs into the hardwood pulley, as a belt and braces solution?

I have a nasty feeling that all the above is not the best approach. Does anyone have any better ideas please? I have probably been lumbered with this job in desperation, from the tower ringers. I used to ring bells until my muscle wasting disease got the better of me! But it seems that I have not escaped from working on the bells.

Andrew.

Why not use a steel disc and make the bush long enough to pass through on each side then put a tack weld to hold it there?.

I am not so sure I would use Nylon, it does absorb water and so may well be looking at a rusty shaft, if it is ferrous. Oilon is a oil impregnated version, but I would have gone for Acetal (Delrin etc).

You can with care use adhesives on Acetal but a bigger bush and with some through fasteners to the aluminium discs could solve that problem.

Could a top hat shaped bush be screwed or bolted into the pulley through the flange of the top hat and a retainer used between the bush and the wood. Would making a steel top hat and fixing as above and then using a bush of what ever you want. What about a double top hat with a register to maintain concentricity in the centre.

Mike

Andrew,

I presume these are the ground pulleys which are fitted in pairs to guide the rope where it comes off the wheel. In engineering terms it is a low speed, low stress application, so a sympathetic low-tech solution would be appropriate.

Nylon tends to absorb water and swell in damp conditions (and as a former steeple keeper I know all about damp towers). You might consider using delrin/acetal for your bearings instead of using nylon. Acetal turns beautifully.

Can you turn the bearings with a flange on one side, then recess the flange into the pulley? A couple of countersunk screws, brass of course, through the flange would keep the bearing in place.

I would not use use metal or epoxy on a wooden pulley as they cannot move with the natural expansion and contraction of the wood. My initial idea would be to cut two shallow stopped grooves across the face of the pulley at right angles to the grain, then glue in strips of good quality plywood with a waterproof wood glue. Put a small woodscrew or a pin at each end for added security if you don't trust the glue. It would be wise to do both sides to keep any stresses balanced.

I hope they have offered to do the removal and installation for you!

George

P.S. Ha! Larry, KWIL and Mike type faster than I do!

Edited By Georgineer on 08/07/2018 11:06:46

I would suggest hard alloy discs (eg 6082) either side bonded with epoxy or a better choice might be a polyurethane such as Sikaflex ( the type of adhesive that is used to bond car windscreens in place) which would tolerate any movement within the wood due to moisture variation. This will hold the wood together well should the splits develop further. Add flanged Oilon bushes screwed/bolted to each side to form a hub. Oilon will last much longer than straight nylon and is available in large diameters, up to about a foot I think. It machines well. I have of course assumed that you have the space to be effectively making the pulley thicker ?

Trevor.

Andrew,

I have had great success with a foaming polyurethane glue in bonding mismatched materials together, like sticking bar ends on wooden handles as holders to then cut slices from the bar on a bandsaw.

The material is called Gorilla Glue, it is widely available in nice screw top sealed squeezy bottles. I would also introduce proper wood glue into the pulley cracking and as others have suggested, screw fit side plates to help clamp in top hat shaped bushes with Gorilla glue between the cheeks of the plates and the pulley sides

As KWIL advised, avoid Nylon, Delrin would be a better choice

Regards Brian

Thanks for the ideas so far. It seems that my initial ideas were not the best, as I suspected. George you are quite correct about the application of the pulleys, so a low tech solution seems fine.

Everyone doesn't much like the use of "engineering" grade nylon for the bush. So I shall see if I have any acetal / delrin or even oilite for the bush material. The Nylon came with the pulleys so I never gave it a second thought.

I most certainly am not going to thread myself between wheels and pulleys to do the replacement in the tower. I can certainly thread my way in, but getting out is an entirely different matter! Guess how I found that out?

Thanks everyone, your input is much appreciated.

Andrew.

I would use one of the Nylatron grades for the bushes, very good wear characteristics and self lubricating. If the bores in the pulleys are bad, plate each side in steel and fit flanged steel bush clamped through then fit inner bush.

Why not make wooden bushes and glue them in place? Presumably the original wooden bearing surfaces lasted a good many years before requiring current repair? If the pulleys are splitting, or in danger thereof, how about gluing and screwing plywood discs each side? The brown stuff is not really my field, so just thinking out loud.

Hello Everyone,

Just for the record. The pulleys are newly made, pity about the incipient splits! The centre bore was cut with a hole saw and it isn't concentric. So a faceplate job is required to true up the bores. They may as well left me to do the bore on the lathe.

Andrew.