Topic: 7/8ths Scale Darjeeling DHR B Locomotive

[jockygerald]

from the picture it is clear that the amount of carbon evolved is exceeded normal limits.

[Ferd]

Here is a bit more design progress.

Arminius, the pump will not need a lot of displacement as the loco is butane fired so very little water is wasted other than during operation. The boiler is only 2" in diameter so my thoughts were using a single ram pump with .125" ram. I am also working on  a couple larger engines that could really use a more efficient pump in particular the SR&RL #23 in 7/8ths scale will be coal fired and the boiler should be 3" in diameter minimum.

Yes I know how lazy using laser cut parts, then again to have all the holes and radii cut for you within 5 thou, why not 

[Arminius]

Hello, Ferd:

I have designed, built, and fitted a single cylinder double acting axle pump for my 3/4" scale Hudson.  The design was liberally adapted from a post bag letter in Model Engineer from waaay back when.  It uses 2 orings of different sizes and 3 check valves.  I don't have drawings, only sketches I made in '85 or '86.  Do you know what pump displacement per revolution you require in cubic inches?

I think my design could be easily adapted for your use;  almost 4-1/2" between axles should be sufficient room and width is not a problem;  in my size it is only about 1" wide.

I also published an article in Model Engineer in 1995 regarding a duplex steam pump I'd designed and built.  This design might also be a little too large for you but it can be shrunk down to suit your loco.  I'll try to post an assembly drawing here but, as you know I have some difficulties with posting photos.

And then there is the turbo-generator for which I have a really cute and functional design...

Arminius

[Ferd]

Hi Arminius

The axles are 122mm between centres and the frames are 67mm apart. I am really intrigued with the  double acting pump. I have design ideas from Kozo's book and a smaller variation from Brian Wilson's recent book - do you have any reference drawings for the pump - a duplex pump is also a great idea, saw a small one on a german forum that was applied to a G gauge engine.
The boiler will be butane fired.

cheers Ferd

[Arminius]

Laser cutting?  LASER CUTTING???:-)).

Geez, Ferd, whatever happened to drilling or hack sawing, and filing???:-)).

That's how I made all the siderods for my 2888 Hudson back in '86 or '87.  Really.  The only machines I had at that time were a 6" Atlas lathe, an 8" Delta drill press which I still have, and a 7" Atlas shaper which I also still own.  The 1/4" plate was free from my then employer.

When my son was old enough to appreciate the left-over steel plate from the side rods he asked "Gee Dad, were you THAT hungry you had to chew on this stuff or was that the only way to to cut the steel? You must have tough teeth".  I think the little devil was only half joking.

What is the axle spacing on your locomotive?  Have you thought of fitting a good double acting pump?   A well-designed and executed pump will halve the load on the eccentric while equalizing the wear to both sides of the eccentric.  There is a clever design for this, quite compact and, it requires only 3 check valves!

Then you need a duplex steam pump to feed the boiler when the loco is in steam but stationary, to replace the water used for blast nozzle steam.

I also noted in the pic below that it is equipped with a turbo-generator for illumination during night runs.  Flashlights are sooo gauche.:-)).

Arminius

[Ferd]

The frames and cranks are ready for laser cutting, I am getting the side rods ready so I can hopefully get the parts laser cut within the next two weeks. One of the nice features of 3D cad is being able to see how well the parts fit and clearance before any chips fly. Hoping to find room for an axle driven water pump so the engine can fill itself from the tank on top of the boiler.

[Ferd]

One of my favorite engines is the Darjeeling B unit. I guess you either love it or hate it. This has been a long ongoing project and my plans are to have it completed by the end of this summer. Currently I am building two of them, one for my collection and the other for a good friend in Sweden.  Here is a photo taken by Elizabeth Churchill (found on flickr - under creative commons license)