propeller bore reducer bushings

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PCUK said:
Any local engineers will be able to make them for you.
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Oh really? A "mate" wanted some lathe work doing and the firm that he tried had all gone CNC. They said that that they couldn't make anything without the programs which were all written by a programmer in London!

The days when every town had a railway, a gasworks, a blacksmiths and a foundry are long gone and trying to get anything done can be like banging ones head against the wall. There is however a rumour about a metal-worker who has a workshop somewhere up an alleyway in Plymouth Devon. Allegedly this bloke heats-up propellers to a high temperature "almost red" then he pours molten bronze into the bore. Allegedly the new metal bonds OK with the old. Once it has cooled the propeller can be machined to suit whatever taper the client wishes. Allegedly its a very small "grey" business that doesn't advertise and only uses cash. The jobs are in fact done almost as a hobby. Unfortunately I don't have anymore information.

If the wanted taper is exactly the same as the original taper and not too far out - say reducing a 1-1/8"" bore to 1" there is a method that avoids the casting of bronze or lathe-work. Brass strip can be annealed and bent into a sleeve. Sleeving a 30 mm bore down to 25 mm is another possibility as brass sheet in 2.5 mm thickness is a standard size. Use all these ideas at your own risk as I will not be responsible for any failures or mishaps. Good luck!
 
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Has it ever occurred to you why T. Norris will not supply. If you go down this route then best you put RNLI on speed dial! or better still just get them to follow you for a day or 2. Prop relies on a frictional (metal to metal contact) you cannot achieve sufficient holding power with a nylon/delrin bush. This will lead to the key being stressed with shear forces leading to failure.
 
dunmor said:
Does any body know where i can get these from. i have a chance of getting new props but they are for 1.5" shafts. mine are 1.25. many thanks in advance. have been on google but all the supplyers seem to be american.
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Keys are not essential,they only come into there own if the props come loose ! which shouldnt happen. The tapers must be a good fit . A bronze tapered sleeve with a slit in it will do the job ok but it will be quite thin in your case.I presume there is some finantial advantage in the 1.5" props.

Jim
 
Lake Engineering of Hamworthy Poole may be able to help. There is also Lancing Marine of Worthing.

If both tapers are the same angle it might be possible to make a good bodge by using annealed brass strip wrapped around the tapered shaft and beaten to shape with a mallet. Vise-Grip-Pliers or Mole Grips may help but several annealing sessions may be needed. For example going down from one and one eighth to one inch only needs 1/16" thick brass strip!

Yet another way is that used by the mythical-man-from-Plymouth. Allegedly he heats propellers to a dull red then pours molten brass or bronze into the bore. Once it has all cooled down, the propeller is bored to the wanted taper.

A new method has been invented that involves getting a thin bush made that fits the shaft. The bush is a sloppy fit in the propeller until Araldite epoxy resin is poured in.

If a 1 in 16 SAE taper is in use the grip on the shaft will be so tight that a key may be superfluous but this is up to the user. Teignbridge Propellers use the 1 in 16 taper as they say that it gives a greater gripping area than the popular 1 in 12 and 1 in 10 tapers.

This problem of bushes and tapers looks like being around for evermore!
 
macd said:
Did Norris indicate whether using such a bush was a wise move? I've used them in the past and been impressed by their knowledge (and prices).

I'd have thought anyone competent with a lathe could easily knock up a suitable bush. Assuming your shaft is stainless, you'd have a choice of that or whatever the prop is made from.

The main problem I'd envisage is that two keyways would need to be cut into the bush: one to key to the shaft, the other to the prop. Or, since it's a mere 1/8" thick, a slot allowing you to utilise a larger Woodruff key through all three components.
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IMHO the plastic bore reducers are a VERY BAD IDEA unless one is only playing with an electric trolling motor. I would strongly suggest getting some brass or bronze strip and making a reducer out of that. After several annealings and driving-in the shaft the strip should be shaped to perfection. For extra security it can be silver-soldered in place using "Easyflo" assuming that the do-gooders haven't banned it. (allegedly the trade name of "Easyflo" was never registered in the UK so a foreign company stole the name! This means that modern foreign Easyflo is not the same as the British original) The metalwork department at my old school had all the equipment to do the job although the brazing hearths were never as good once Coal Gas was phased-out but we were still able to construct brass tankards which were an exercise in graded-soldering. Anyhow in the good old days when boys left school they were adept at using machine tools etc. Allegedly Health & Safety has now put the kibosh on giving people a proper education but this is supposed to be progress. As to the silver-soldering, on something as large as a propeller one will need a 13 kilo propane cylinder and a "roofing torch" which is basically a forty kilowatt burner. Possibly one could borrow such a thing from a builder or a plumber. Cleanliness is extremely important and a good flux such as Borax needs to be used. The metal should be cleaned with steel wool NOT sandpaper or emery cloth. Firebricks will also be needed and whilst bricks from night storage heaters will resist great heat they are not ideal but at least they don't splinter. Good luck!
 
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