I am attempting to refurbish a Metropolitan injector, and only have the original worn nozzles to go by. This is a lever operated lifting type with two sets of nozzles and tubes.
Does anyone have experience to comment on how precise the internal dimensions of the nozzles have to be? The main combining / delivery tube seems to be the most worn, and it has a crack from being overtightened, so I am replacing that. The other parts can be cleaned up enough, I think.
I have made plaster casts of the internal passage, but with the wear the minimum diameter may not be that close anymore. It's clearly a series of cones rather than a constant curve, so that makes it a little easier.
I plan to make a reamer to achieve the final internal shape. Another question is does it matter if it is made with a continuous curve or the cone approximation is as good as it gets? Theoretically it should be a curve, but I suspect that in practice the difference is hard to measure.
Any thoughts or experience in machining the internal shape would be appreciated.
Thanks in advance for your time and help.
Gordon Cook, Volunteer
WW&F Ry Museum

Dear Gordon:
We have had good results with nozzels machined by Balinski Tool & Machining, Inc, 262-857-9232. That said, we supplied the raw castings and prints with all dimensions.
All injectors that I have worked on have tapered nozzels, often multiple tapers at different places.
The last nozzels we made were for a Nathan Simplex Type "R". It has six nozzels to the set with 7 different tapers. Two of the nozzels have 3 different tapers.
Tooling and setup was far in excess of the cost to machine the nozzels.
Good luck!
J.David

Hello Gordon:

A Google search shows that Metropolitan injectors are included in the ICS (International Correspondence School) textbooks. Their cross-section drawings are quite helpful.

Metropolitan injectors may have been common in the British Empire. I suggest searching (Googling) British steam locomotive and steam traction engine repair & parts suppliers. Two good places to start might be

1. (courtesy of The Ultimate Steam Page / repair links / injectors, website: http://www.trainweb.org/tusp/r_links.html#HPE):

Hugh Phillips Engineering
Abergavenny, UK
phone and fax:
+44 (1873) 856013
E-mail: hugh@hughphillipsengineering.com

"Specialise in the manufacture of full size steam loco valves and controls such as : live and exhaust steam injectors, steam & vacuum brake valves, ejectors, etc., mechanical lubricators, hydrostatic lubricators, turbo generators, safety valves, valves of all types for steam, water and air, steam driven air compressors"

"This has been their main activity for over 25 years. Amongst projects completed have been the restoration of six of the Sudan Railways 2-8-2 for grain haulage in 1985-1986 and the design and build of three 4-4-0 and fifteen passenger cars for Euro Disney in Paris."

2. from website: http://www.mcbo.co.uk/
H.A.McEwen (Boiler Repairs) Ltd
Boilermakers - Boiler Repair Specialists
Boiler Plant Engineers

Farling Top, Cowling, Keighley, West Yorkshire BD22 0NW
Tel: 01535 634674 Fax: 01535 636802

They have done major restoration and reconstruction work on many British steam locomotive boilers. They make new flanged tube sheets.

"McEwen Boilermakers are renown for their specialist skills in repairing all types of Vintage and Industrial Steam Boilers. These are comprised of Railway Locomotives, both standard and narrow gauge, Traction Engines, Steam Waggon, Lancashire and Cornish “Mill” boilers, Steam Boat, and all types of Industrial Package Boilers. "

Good luck!
- Doug Debs

Often times a careful inspection of the nozzles will turn up unworn surfaces. Most nozzles do not wear evenly and some cavitate badly adjacent to the smallest diameter while leaving that diameter reasonably intact.

We tested delivery nozzles with a constant curve against our nozzles with a series of tapers. There was no difference in performance and the coned nozzles do not appear to wear any faster. We make "D" reamers to finish nozzles that are too small to bore smoothly. They are easy to make.

For what it is worth, I would make the nozzles as small as evidence indicates and try them. You can always ream them a bit larger. Probably the most important thing is that they are concentric to one another. New Penberthys are notoriously eccentric and don't work very well until the tubes are aligned. Good luck.

A Google search shows that Metropolitan injectors are included in the ICS (International Correspondence School) textbooks. Their cross-section drawings are quite helpful.

Doug,

Can you provide the link(s)for this info?

thanks.

Ray

Well, I was at least partly correct. I found two reprints (about $20 each) that cover the Metropolitan Injector:
http://knowledgepublications.com/history/mechanical_movements_detail.htm see section 5: Steam Appliances

Strickland L. Kneass: Practice and Theory of the Injector. John Wiley & Sons (1894).
This was reprinted by Lindsay Publications some years ago, but they are out of stock and do not plan to print more. Fortunately it was reprinted in 2007 by Kessinger Publications, ISBN 0-548-47587-3
http://www.abebooks.com/servlet/SearchResults?sts=t&tn=practice+and+theory+of+the+injector&x=41&y=17

I suspect that an ICS book on injectors from the 1890s or 1900s would also cover Metropolitan injectors, but haven't been able to confirm this yet.

- Doug

Painfully obvious, but is Backshop Enterprises making these? I know they support some other injectors in various sizes.

dave

Thanks to all who have offered their thoughts. Linn has confirmed my suspicion that the injector manufacturers figured out that it wasn't advantageous to make the internal shape a smooth curve, and so didn't bother.
I do have Kneass's book, and also 'Injectors: Their Theory, Construction, and Working", By W.W.F. Pullen, a 1997 reprint of the 1893 text by Camden Miniature Steam Services in the UK. (If you like math, you'll love this one!)
Also I have found some generic Metropolitan information in Google books, but all refer to earlier versions (circa 1898) of the dual tube injector that we have, so many details are different.
I was hoping to avoid going to a machine shop that would be able to custom make a reamer simply because of the expense and because there is a bit of trial and error here and that would make it more difficult to adjust the dimensions if necessary.
In any case, I have found a tapered reamer that has the correct angle for the smallest section of the main combining/delivery tube, which should make achieving good finish and accuracy in that section much easier. From my measurements on the 6 1/2 "OA" nozzle, the angle of the smallest cone section should be about 2.2 to 2.4 degrees, and a Brown and Sharpe taper (I think used in aircraft construction) is 2.4 degrees. Since this is the longest section, and is the same both entering and exiting the minimum diameter, I believe it is the most critical. I will simply bore the two larger cone sections at the entrance to the combining tube.
When we get it up and running I'll let you know how it works.

I forgot to mention that Kneass' book is available for download in Google books. It's a good explanation of how injectors work with a thorough and understandable analysis of the details as well as illustration of the many versions available up to 1900.