[modeleng] Re: Injector selection

Hi Rich,

Speaking as a 2½" gauge man, a No.2 is really too large for a 2½" loco 
although people do fit them. It puts the water in fast but drops the 
pressure rapidly as well. They use too much steam for the small boilers 
to keep up with.

I've made  an 8oz and a 4oz for my Helen Longish which work but I 
haven't managed to get them to run dry yet  - more experimentation 
needed! I can leave the 4oz running with no real  drop in boiler 
pressure. The original idea was that the 4oz could be left running most 
of the time and be used instead of the axle pumps and the 8oz used for 
more 'serious' topping up.

I did enquire about No.1's at my local stockist and was told that the 
smallest they will sell is a No.2 as they cannot guarantee reliability 
with anything smaller. Thinking about it, I don't think I've ever seen 
anyone advertising a No.1?

I've read that as a rough guide the injector should be able to supply 
about twice the water consumption of the loco when running.

Out of interest I devised a spreadsheet to work out the water 
consumption based on cylinder swept volume, wheel diameter, speed, and 
cut off. You can download a copy from here:

http://www.baggo.copperstream.co.uk/me/injectors/Injector%20size%20calculator.xls

John

R.L. Roebuck wrote:
> Hi there All,
>
> What is the general opinion on what size of injector to fit to what type 
> of locomotive?
>
> Looking at the different common sizes out there:-
>
> * Number 2 (11 UK fluid oz water/min)
> * Number 3 (16 UK fluid oz water/min)
> * Number 4 (22 UK fluid oz water/min)
> * Number 5 (2.7 UK pints water/min)
> * Number 6 (4 UK pints water/min)
> * Number 8 (1 UK gallon water/min)
>
> ...is a number 2 injector too large to fit to a 2.5" gauge locomotive?
>
> Do many people fit two injectors, to allow for the differing needs of 
> continuous running and end to end running?
>
> I tried searching on the 'interweb', but unusually seemed to draw a blank 
> - am I just looking in the wrong places?
>
>
> Yours,
>
>
> Rich.
> PS Given the sometimes global nature of our discussions, if it helps...
>
> 1 US f.oz = 29.6 ml
> 1 UK f.oz = 28.4 ml
> 1 US gal = 3.79 l
> 1 UK gal = 4.55 l
> 1 UK pint = 568ml = 1.20 U.S. liquid pints = 1.03 U.S. dry pints
>
> PPS Why does no-one seem to make a number 1 injector?
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