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Burrell Single Crank Compound Traction Engines - 4" Scale

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As promised in my introductory thread here are some sample pictures of progress on my traction engines. Here are the two engines, and assorted parts in progress. I am building the engines according to what interests me at the time, rather than in a logical order. I started with the gears, because I like gears:

And from the other side, showing the differential. The bevel gears are true bevel gears, rather than the normal approximations, made on my CNC mill:

I've made the pistons and piston rods, but instead of the normal aluminium pistons in this scale I chose to design and make hollow cast iron pistons; the two halves screw together. The stiffening ribs were designed using a FEA software package. The pistons are oversize and will be ground to final size once the liners are made and fitted:

I have recently finished the brake shafts and nuts. This was an interesting exercise as I have never cut a square thread before. It worked out better than I thought it might:

Here are the serial taps I made to cut the square thread in the bronze brake shaft nuts:

I've also been busy making the studs and nuts for the engines, mostly " and 5/16" BSF, I still have some 2BA studs to go, and assorted bolts:

I am currently making the gear change mechanism. This has been redesigned as the drawings are a fantasy. Having 3D printed the parts to make sure it worked as intended I am now converting the parts to metal. Once finished I'll have a go at the water pump. This has been completely redesigned, as I think the original one, as drawn, has a ram that is way larger than needed. I have also taken the opportunity to redesign the internals to incorporate proper winged valves, as per full size. Here's a section of the 3D CAD model:

My morning tug pilot duty has been cancelled due to wind and rain, so I've got the rest of the day in the workshop!


Dave Otto:
Very nice work!

It appears that you keep your toys in the kitchen? you must be single :lolb:


Wow, that is some heavy iron Andrew. But well done from the looks of them too!!


very impressive work indeed!
very professional looking shop made taps as well. what size are they and how did you go about making them?
thanks for taking the time to post the pictures


Dave: Any resemblance to a kitchen is purely accidental. It is actually the assembly hall, casting storage area, and potential workshop - spot the coil winder, dead weight pressure tester and Pultra lathe on the table. I just happen to cook in the same area. And yes, I am single, the last girlfriend left in a huff muttering about lifestyle issues.

Bill: Indeed they are big, the engines will weight over a 1000 lbs each when finished. But they are an antidote to the electronics I do in the day job where the components are getting so small I can't see them. One sneeze and that's the entire packet of resistors gone for good.

Peter: The brake shaft square thread is " OD and 8 tpi. I'll dig out some pictures and post an outline of how I made them tomorrow. I see that you are in Liverpool; I was there in the late 70s doing my first degree at the university.



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