A boring question

If it was mine I would consider lining the bore with a "liquid metal". Given the lathe option pour some in bung up the ends and spin until it has gorn orf. Make up a 76mm reamer look alike and hand screw it through. I have never tried these options BTW. Alternatively run a hose up the inside and use the handle to operate a tap

Richard

Great minds, etc - I was thinking along the lines of fitting an electrically operated pump in the body...strikes me as MUCH easier than all that palaver with boring bars

Regards, Tony

Why worry with re-boring it? Sleeving it would be my approach, then make a simple piston to suit. (I did a similar job a few years back, and found the incorporation of modern one-way plumbing fittings to add greatly to the efficiency of my own system, which I still use regularly)

In article , BobKellock writes

Intriguing problem, and I'm sure you will get lots of good suggestions (and possibly some ribaldry...).

Does the delivery spigot come off? if not, you would need a lathe with a prodigious swing to accommodate the whole thing for use with a conventional boring bar - and a pretty big fixed steady. Most likely, you would need to set it up on the saddle/cross slide and use a very long between centres boring bar.

You may find you need to use a completely different method. One of Guy Lautard's Bedside Reader books has a story about someone setting up a boring bar which used the object itself to support bushes and a boring bar, you might find some inspiration there.

Sleeving the bore might be a worthwhile idea to think about - if you only want the external appearance to be correct and don't mind the non-original mechanics, this might work very well. At least you can bore or hone the sleeve (seamless steel tubing?) much more easily than a rusted thing with big bits sticking out.

How much use will the pump be getting? If only for occasional demonstrations, do you really need to bore it out? The early steam engine makers got by reasonably well with very crude bores and leather pistons IIRC.

I think if it were my job, I would start by wire brushing the interior to remove as much rust as possible, then stopping one end and filling it with one of the proprietary rust removers (for example, that sold by Arc Euro Trade). Then you can take a better view on how necessary a re-bore will be.

David

Old bilge pumps etc., admittedly on a rather bigger bore, used wooden pistons with leather nailed to the outside to form a cup washer-type seal. A leather flap valve in the centre of the piston would be weighted with a piece of lead.

Tim

I can offer two ideas, firstly get a stainless steel tube and glue it inside, quick but not too original or secondly bore it out by making up an adjustable boring bar and mounting the pump on the lathe saddle with a guide bush in one or both ends, leave the tailstock off take cuts to clean up. Peter

Is it really that bad inside and in fact how close a fit do these things have to be to work properly? I doubt they were made to a very high precision in the factory. Once you know these things you can better decide what to do. Looks to me like a line boring sort of job much as you'd do on the main bearing saddles of an engine block. A long bar running between bushes aligned with the ends of the job and a simple carbide cutter sticking through the bar which can be adjusted out and locked with a grubscrew. Alternatively it could be honed out progressively until it had cleaned up enough to be functional. You could do that with an ordinary engine bore hone albeit probably working from both ends due to the length.

That is the method I would try. Hydraulic cylinder shops use adjustable (not spring) hones to recondition long cylinders like that. I suspect a spring cylinder hone would clean it up well enough to work with a leather cup. You might even try a long dowel split to hold some coarse abrasive paper and turned by an electric drill motor.

Don Young (USA)

I think that might be your best bet, at least to start with. The most important thing with a pump like that is the condition of the foot valve. The bucket / plunger doesn't have to be a wonderful fit, but of course it's better if it is so long as it still moves freely in the cylinder.

Tim

In article , BobKellock writes

Coalbrookdale! That vintage, from those Iron Masters......

snip

Bet it wasn't really in millimetres........ ;)

John