Scale Traction Engine – installing a steam powered boiler injector.

by John

My 3″ Fowler R3 Traction Engine boiler can be filled with a hand pump from the tender tank, by a crankshaft powered pump from the tender tank, or by a battery powered electric pump from the driver’s trailer.   The full size original R3 (see previous post for photos) has a steam powered injector, which uses boiler steam to suck up water from the tender tank using a venturi effect, then using black magic passing the steam+ water through some cones, increases the pressure which forces the mixture back into the  boiler.

Here is a link to a YouTube site which sort of explains how the black magic works.

And this is the steam injector on the full size R3 Fowler.


And this is the injector which I bought for the 3″ scale Fowler.

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It is a vertical injector, with connections for 1/4″ (6.35mm) pipes.  But I did not use it because it protruded too far underneath the tender.  So I have used an identically sized horizontal injector, which is shown below, during installation.  The full size original also appears to be horizontal.   The black fitting connected is the water inlet valve.  The control handle will extend above the rim of the cockpit.



The red thing is the winch, and its driving disk.  Winch engaging pins have never been completed, another job for later.  The rear wheel has been removed.  The injector pipework passes between the winch drum and the hornplate, with just enough clearance.  Running the pipe around the brake axle seemed like a good idea at the time, but I am not so sure now.  When painted black it will not look so odd.   The water connection with the tender tank is yet to be made, as is the steam supply connection.  A few more hours.