1/20th Scale Burrell

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Also a thick pencil line can form a limit to where the solder flows... it won't cross the line of clay and graphite. I use a Carpenter's pencil as a good black line for this... (when necessary).

Hi Ken, yes, I tried this on a few samples, it's not quite masking tape for silver solder, but it works well



I've now made the Burrell door handles and the locking system, this now all works at 1/20th scale.


This hopefully shows the basic locking system.

The Burrell door lock is a T-head bolt with flat sides on the threaded section. This bolt goes through the door from the back, a handle with a slot then goes on allowing the bolt to be rotated. A second handle with a threaded not then allows the bolt to be pulled up tight.

In the smokebox a beam goes across the diameter of the opening and has a slot in it to allow the bolt head to go through. Then the bolt is rotated and hence the T-head gets a purchase on the beam.


The handles were made as one part based on them being so small and then I split them into two parts later.


Still lots to do
I’ve been thinking about the Burrell gearing for some time. Calculating the overall ratio, estimating the maximum torque and speed of the traction engine.

I think 1000rpm is a good top speed for this small double acting engine. The rear wheels are 97mm OD and the gearing gives me around 10:1

My simple calculation says that this will give me 1.1mph or ~0.5m/s which feels reasonable for an engine that might run on my dining table.

This is very similar speed to a Mamod Wagon with 2000rpm, 16:1 and 75mm OD wheels
12mm bore at 60psi is ~45N on the conrod

14mm stroke means ~0.32Nm of torque at the flywheel

hence 3.2Nm at the wheel

the drive wheels are 97mm OD and so hence 32N of tractive effort and the engine will be around 1.8 to 2kg

Also, I'm likely to run at a pressure of 45psi mostly and so I think around ~24N

That should be fine
I have to firstly say a huge thanks to JG for sorting out the angles and cutting of these bevels. He did say bevels are not easy to get right and I'm definitely learning that the heard way....

I spent a happy hour (no drinking) setting out a 9.5° angle on the milling table and then aligning the rotary table to it.



Now I have to go and cut those gears. Must admit that the cost and effort required in fitting the DRO has been paid back several times over...and it isn't the simplest thing to fit :D
The differential has taken some time to get to even operate. However, after making some shims to space the crown wheels correctly I have something that operates as a differential.

I did run this at speed on the lathe to get it run-in - this helped a lot.

I might still re-make this, but for now I know I can get something that works as a differential. In practice it will not actually see that much work and so it is probably ok.
Back to the Burrell at last and this time the conrod.

As this engine is rather small, hopefully the matchstick puts it into context, I decided to split the crankshaft. This allowed me to make the big end of the conrod from PB.



The other parts were made from brass and then all silver soldered together like jewellery.


I really like the easy flo silver solder paste for small parts such as this. Just remember to heat the parts with the blow torch away from the joints before then heating the joint/silver solder.

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