# S'powered screw-injector idea?!?



## Pauli (Jan 3, 2008)

Hello everybody,

In my mind, I've developed this strange (?!) idea for a steam powered screw-type water pump / injector. I want views and input, please! Look at my sketch at;

http://gallery.me.com/anders.grassman#100011

Sadly, I can't draw on a computer. In fact, I can't even draw a helical screw on paper. :-( But please try to understand my scetch anyway. ;-D And yes, I'm not even sure what direction the helixes should be mounted either. In practice though, I guess I would find out in a hartbeat! ;-D

Description; 
- on a single axle, two helical wormscrews are fixed. (Ungeared, single common axle solution, lessens transmission losses due to friction.)
- this "dual-worm-screw-axle-unit" (in my mothertoungue Swedish, and in German, that would actually be a legitimate single word! :-D ) is mounted / suspended, in a close fit bore, that "just" allows free rotation. The "wormaxle"-unit is mounted in bearings in both ends. Possibly by pointed mechanical clock-style needle bearings (forget the "jewls" though ;-D), or maybee some "ball-bearing" or similar style.
- the bore, and the two worm-screws, are separated by a "wall", through which though, the common axle passes through a pressure-seal (still allowing rotation), dividing the bore in two separate parts, inbetween which as little water- or stam-pressure as possible, should be able to pass. (Matching the right high- and low-pressure, steam- or water-end, still puzzles me. ;-)


Advantages would be;
- might actually be comparatively simple to build, if ready made worm-gear screws could be used as basis. (Cutting helical gears is faaar beyond my workshop skills ;-D
- would act - and possibly even look - something like a normal injector. 
- would be based on somewhat more basic mechanical principles, than a conventional injector. (At lest the general wisdom has been for decades, that no one has succeded building a conventional injector in small sizes, and that it probably can't be done.)

Drawbacks;

- Is it AT ALL a possibly WORKABLE idea? Maybee it has even been tested (and discarded?!) BEFORE?!?
- could it be based on pre-fabricated worm-gear screws, or would it probably, in practice, require machining unique dedicated screws, to work reasonably? If yes, I'm afraid the building would be the domain of a relative few skilled (and otherwise well "endowed", ie time and machinery) people, or a candidate for serial production.
- would it be self-starting? (=would it be able to produce the initial suction to the water-supply (tender / saddle-tank)
- A ZILLION OTHER reasons, my (?) idea is dumb / even silly to consider???

Let me know!

Greetings from Stockholm, where pitch-black night, now falls at 16:00 hours...

Anders Grassman


----------



## Dan Rowe (Mar 8, 2009)

Anders, 
You have drawn an Archimedes' screw see: http://en.wikipedia.org/wiki/Archimedes'_screw 
This type of pump is really not suitable for a boiler feed pump. A turbine would work much better than a second Archimedes screw to power the pump, but this type of pump will not delever presures high enough for boiler work. 

Dan


----------



## HMeinhold (Jan 2, 2008)

I have to agree with Dan. An Archimedes screw cannot build up pressure. It relies on gravity/fluid. For pressure you need 2 screws (screw type compressor), but then it gets ugly... 
Regards


----------



## dwegmull (Jan 2, 2008)

A similar design is used by turbo-chargers. However, the impeller blades have a different shape:








This is of course designed to use the exhaust gas flow to compress the incoming air. A steam / water model would probably need different shapes of blades. I've never seen such an apparatus but it would be interesting to try to build one. On the steam side, a small turbine like the one from Jensen could be used. The water side is left as an exercise for the student ;-)


----------



## Dan Rowe (Mar 8, 2009)

For the most part home built boiler feed pumps will be postive displacement pumps. They are simpler to construct and complex curves and castings are not needed. See:
http://en.wikipedia.org/wiki/Pump

Halfway down the page I spotted *The screw centrifugal impeller was invented in 1960 by the late Martin Stähle, the founder of Hidrostal AG.* 
That cought my interest see: http://www.hidrostal.co.uk/default.aspx?p=screwce

These pumps were devoloped to pump live fish and are now used for a any industrial service with large solids such as trash pumps.
Dan


----------



## Kovacjr (Jan 2, 2008)

Id think that what you would need to build is basically a liquid supercharger or a roots type design. The twin screw is what would give you the pressure but the motor needed and steam consumed would probally outweight the usefullness. Of course there must be a reason that everyone still uses simple steam piston water pumps.


----------



## Pauli (Jan 3, 2008)

Thank you for your responses!

What set my imagination in motion, was a guy who successfully built an electric feedwaterpump, I think it was about a year ago in Germany. The pumping action was done by two plain / normal teethering cogwheels. This touches on your comments that two screws are needed to build pressure. I didn't know that, so I omitted the other screw, because I think it would be very difficult to successfully build.


What about powering the two plain cogwheel-pump design with steam? Could it be done simple, and run reasonably efficient? Could the powering side also consist of two cogwheels?


The most beatiful solution is in my opinion the steam powered double piston type, as can now even be bought readymade from Regner. However, it costs roughly 500 Euro / 750 USD :-(


----------



## Kovacjr (Jan 2, 2008)

Many drawings are available for feedwater pumps, not that hard to build. Just need the equipment. they can all be scaled down successfully as shown by a few that posted some videos in the past.


----------



## Chris Scott (Jan 2, 2008)

Posted By Pauli on 26 Nov 2009 11:37 AM 
Hello everybody,

In my mind, I've developed this strange (?!) idea for a steam powered screw-type water *pump / injector*. I want views and input, please! Look at my sketch at;

Anders Grassman


Pauli:
While your design and the comments so far have been centered on pumps since you originally mentioned "pumps / injector", here is some information on injectors. While remotely related locomotive pumps and an injectors are very different. This is a link to a good History, principles of operation and principle types of American locomotive injectors:


1. Injectors 
"Theoretical Value of the Injector.—Invention of the Injector. Principle of the Injector’s Action.—Velocity of Steam and Water. —Temperature of Injected Water.—Elementary Form of Injector.—Care of Injectors.—Most Common Causes of Derangement.—How to keep an Injector in Good Order.—Common Defects.—Care of Injectors in Winter. —Sellers Injector. — Nathan Improved Monitor Injector.— The Mack Injector.—Little Giant Injector."


Injectors for G1 Locomotives are available from a number of sources. One is, Bruce Engineering Model Engineers’ Supplies. Link to catalog download page: 2. Polly Model Engineering Limited, incorporating Bruce Engineering . Catalog page #40 has their different injector models and sizing. If you need another source email me and I'll search the catalogs I have.


David Bailey has experience with injectors having used them on the K-27 coal fired locomotives he made a few years back (maybe others since. I'd say he knows all, or at least a great many things about injectors and pumps.


Just in case the above links don't work (?) 
1. http://www.catskillarchive.com/rrextra/chapt11.Html
2. http://www.pollymodelengineering.co.uk/


----------



## Pauli (Jan 3, 2008)

Thanks Chris,

I found both the article explaining injectors, and the link to Polly engineering interesting - I only knew of their 5" locomotive kits before. (Surprisingly affordable, considering the prices of our gauge 1 locomotives!)


Do injectors only have a narrow pressure interval, in wich they work? Considering that pressure kan vary from 1-6 bar in my kessels, that would be problematic. I must say though, the advice regarding operating injetors on Polly engineerings website, makes me more interested. It could pose an interesting challange to learn.


I've only operated an injector on a 1:1 Swedish locomotive. It was an uncomplicated operation, resulting in a loud "swosh" sound, where even the hefty piping resonated! I actually got some hands on, adjusting the reverser and "throttle", kind of driving the locomotive under close supervision for some kilometers. The engineer and driver allowed this after the 125th anniversary of Swedens state railways, as they quickly recognised I "knew the stuff". Lucky me - it was one of Swedens largest standard gauge locomotives - a rare opportunity.


Apart from that, a steam turbine locomotive made the strongest inpression on me. Sweden is the only country that successfully operated (two) turbine locomotives - i think it was done for 9 years or so ;-) One of the reasons that Sweden is just about the only successful exaple, is the abundant freshwater in Sweden, as turbine locomotives use huge amounts of water.

An this sort of connects to my late question - could some cogwheel constraption become successful?


----------



## Dan Rowe (Mar 8, 2009)

Pauli,
It is possible to make a small pump that is not a positive displacement type for boiler feed. Pumps that are not positive displacement usually trade velocity for pressure. As an injector is in this class of pump that proves the point that they can be made small. However to get one of these pumps to efficeintly trade velocity for pressure is a not going to be a simple matter. Complex math and formula and a good working knowledge of fluid dynamics will be required to achieve anything efficient.

With enough power and speed even a bad design might have enough pressure for boiler feed. The problem is it might take more power than what is avaible. Hey give it a go and let us know how you make out.
Dan


----------



## Chris Scott (Jan 2, 2008)

Posted By Pauli on 28 Nov 2009 02:00 PM 
Thanks Chris,

I found both the article explaining injectors, and the link to Polly engineering interesting - I only knew of their 5" locomotive kits before. (Surprisingly affordable, considering the prices of our gauge 1 locomotives!)


Do injectors only have a narrow pressure interval, in wich they work? Considering that pressure kan vary from 1-6 bar in my kessels, that would be problematic. I must say though, the advice regarding operating injetors on Polly engineerings website, makes me more interested. It could pose an interesting challange to learn.




Pauli:
The only thing I know about injectors is what I've read in a few pieces like the linked web page. Some time ago the topic of injectors came up and David Bailey replied. To paraphrase, they can be an interesting addition to a small scale steamer, in small steamers the are both temperamental and problematic. Curiosity from this exchange drove me to spend a couple of days digging into injectors. I've never used one. Send David an email and I'm sure he would be more than willing to share his perspective. You might also try searching mls for past threads on injectors and maybe find David's comments. Maybe he will read this thread and reply.




Posted By Pauli on 28 Nov 2009 02:00 PM 




An this sort of connects to my late question - could some cogwheel constraption become successful? 



This sounds like a complex machine to perform a simple task; something you might want to take up with Mr. Rube Goldberg, Mr. Reuben Lucius Goldberg.


----------



## Pauli (Jan 3, 2008)

Thank you Dan and Chris,

I'm very grateful for your and evryone elses input! Now I can happily discard any screw and cogwheel design as likely unreasonably complicated or inefficient ;-D I will stick to conventional designs like axle pump, steam double piston pump, and hand powered pumps - however possibly adding an injector, as it's not that expensive an alternative. I'm planning a long term project for a coal fired engine, wich is why I'm thinking about pumps.


Thanks again! I hate when ideas grind in my mind, and I don't have the knowlige to judge them!


----------



## Dan Rowe (Mar 8, 2009)

Posted By Pauli on 27 Nov 2009 11:29 AM 
What set my imagination in motion, was a guy who successfully built an electric feedwaterpump, I think it was about a year ago in Germany. The pumping action was done by two plain / normal teethering cogwheels. 


This sounds like a normal gear pump. They are a positive displacement type of pump and often see service as all types of oil pumps. For water service plastic gears in a brass housing might work well. You could always use batery power and a motor for a small version. The gears need to have a small backlash and be a close fit in the housing, but this should be simple to make in a home shop. http://en.wikipedia.org/wiki/Gear_pump
Dan


----------



## Havoc (Jan 2, 2008)

Powering an archimedes screw with steam wouldn't work I think. And then we are not even starting on the needed sealing between the circumference of the screw and the housing. Little nightmare. 

The gear pump idea would work. Those pumps can deliver the needed pressure. And they are reversible. Take a look at the Silsby fire engine. Again sealing between the teeth of the gears and the cavity and between the flat sides and the sides of the housing will be not simple.


----------

