Making injection pump spindles?

No answer Tim - they have all gone to Harrogate !
I was a metallurgist in a previous life and have also played a lot with engines, but three things I always left alone - automatic transmissions, synchromesh gearboxes, and diesel pumps. But I worked at Sperry Rand for a while where we made hydraulic valves. The valve spools were generally made of hardenable steel (medium carbon, low alloy), made close to size, then induction hardened on the surface and precision ground to finish. The valve bodies were cast iron. That was 30 years ago, so the memory is a bit vague. I had to check the hardening was in the right place and right thickness on the spools.
I am having trouble visualising what you are describing, is the bore in a body casting or a replacable component ? Do you have to stick to the same bore size to keep the same displacement, so an oversize piston won't do ? Like I said, I have never had a pump apart.
I may be able to pick the brains of a couple of people in Shell's fuel department if you think that would help. I guess they have to diagnose problems in modern equipment, and mechanical pumps haven't exactly died out yet. They should be familiar with the materials involved.
Steve

No answer Tim - they have all gone to Harrogate !
I was a metallurgist in a previous life and have also played a lot with engines, but three things I always left alone - automatic transmissions, synchromesh gearboxes, and diesel pumps. But I worked at Sperry Rand for a while where we made hydraulic valves. The valve spools were generally made of hardenable steel (medium carbon, low alloy), made close to size, then induction hardened on the surface and precision ground to finish. The valve bodies were cast iron. That was 30 years ago, so the memory is a bit vague. I had to check the hardening was in the right place and right thickness on the spools.
I am having trouble visualising what you are describing, is the bore in a body casting or a replacable component ? Do you have to stick to the same bore size to keep the same displacement, so an oversize piston won't do ? Like I said, I have never had a pump apart.
I may be able to pick the brains of a couple of people in Shell's fuel department if you think that would help. I guess they have to diagnose problems in modern equipment, and mechanical pumps haven't exactly died out yet. They should be familiar with the materials involved.
Steve

Didn't really make a plunger for an injection pump, but tried it (to see if it is doable; it had less than 1mm diameter). Problem are the tight tolerances. They are in the 1/1000 mm range with very accurate geometry. The problem might be to meassure the exact diameter of the bodies bore. I managed to do a plunger with quite some time of lapping. The material I tried it with was SS (hardened). But again, I didn't even intend to use it.
Does that help?
Nick

I was there yesterday
The bore is in a 'replaceable' item. but chances of finding a ready made replacement may be slim. The actual bore isn't super-critical, as the engine governor will adjust for variation in fuel delivered. Large changes to the bore would start to affect the timing. What is critical is the fit and finish, as there are no seals & it's pumping at around 170 atmospheres. And of course it mustn't seize.
One thought I've had was to get a worn plunger hard chromed & then ground to within a thou or so of finish size, then lap it to fit. Or maybe even lap the bore to suit, that might be easier than lapping a hard chrome surface? Never tried, so I don't know.
Any help appreciated
Cheers Tim
Dutton Dry-Dock Traditional & Modern canal craft repairs Vintage diesel engine service

Nominal bore here is actually 5/16", I can measure that to one tenth (0.0001").
All contributions gratefully received.
Thanks Tim
Dutton Dry-Dock Traditional & Modern canal craft repairs Vintage diesel engine service

This link may be of interest - 'm sure there are also a couple other threads covering injection systems on there aswell.
moray
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I had the same thought, but have never been down that avenue - though I
have considered it for renewing lathe spindles. I was going to go to one of the companies that offer this service for restorers of the forks on old motorcycles. They are a bit large scale for your job, but have all the right elements, clean-up, plate and then grind to size.
I don't have experience lapping pistons, but I don't see there should be any problem lapping a chromed piston using hard enough compound. Diamond paste is the ultimate - I have used that to polish tunsgten carbide for
analysis under the microscope. You would have to be very careful about not getting lapping paste into the bore, otherwise it will become a lap itself, which will means the finished item will go from lapped out to clapped out rather quickly !
How would you clean up the bore ?
Steve

Can't answer that, but I would be cautious. Chrome has certainly different properties than the original material. You might get problems with the lubrification. Is that spindle hard to make?
If that plunger is ruined (and they are, aint they?), you need to get the right geometry back again. And that is by grinding/lapping.
The first Diesels all had problems with the injection pumps. They never got it working at those pressures and they had to use compressed air to blast the fuel into the combustion chamber. Aroud 1900, mechanics weren't completely stupid and untalented, but they didn't get it working. Even not with prototypes and pumps that were very big. Just to say that it isn't a piece of cake for a HSM.
You can find nice tools for honing bores. The basic tool costs about 2000.- EUR and each spindle around 400.-. No, I don't have it. :-)
Nick

Not intrinsically hard to make, but getting it 'right' won't be easy & I think having the right material is pretty fundamental. Chroming came to mind as one way to get a hard surface which will take a very good finish, without heat treatment.
I'm sure of the last point I'd be just as happy to farm the job out if I can find someone who can do it without the cost running into megabucks.
Cheers Tim
Dutton Dry-Dock Traditional & Modern canal craft repairs Vintage diesel engine service

Have you tried some of the local diesel injection specialists?
You'd be surprised at what they can get for old injection pumps.
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I have to confess I haven't asked them on this specific item, but Crossleys were a law unto themselves in this department. They have had a go at some old Crossley injectors for me, but no chance whatever of getting new parts for them.
A lot of the bigger Crossleys were modified to use Bryce or similar 'standard' injection equipment, but that isn't a straightforward job.
Cheers Tim Dutton Dry-Dock Traditional & Modern canal craft repairs Vintage diesel engine service

Tim,
I said I would have a word with the Shell guys and as expected they are rather focussed on the latest stuff, which runs to the finest of tolerances due to the high pressures used. They said its often steel in steel with the piston hardened and precision ground and the bore slightly less hard - something like EN24. Having matching materials helps keep the tolerances as temperatures go up and down. They expected much the same material for the piston in older pumps with the piston hardened and ground, but the bore might easily be cast iron. The clearance needn't be so precise at the consierably lower pressures.
I don't know that this leaves you any wiser, but it seems to support what others have been saying.
You may not know that diesel fuel has lubricity additives added. This is especially the case since they took a lot of the sulphur out - the sulphur was good for lubrication and without the additives the wear in the pump can be a bit high. Now I wonder if they put the same additives in the fuel used for central heating ? Where does this leave chrome and cast iron - well I think chrome piston rings work OK.
Steve