4" Burrell DCC Showmans Cylinder Block

Good evening all,
After some advice regarding one of our club members STW DCC Showmans engine he has been building for the past four years. As this is his first involvement with building steam engines he is at the point where he thought he was ready to steam the engine for the first time.
I suggested to our member that I would go over and fit my equipment so as to be able to carry out a hydraulic test, on the engine and to rectify any minor leaks before putting a fire in the firebox for the first time and then finding leaks.

After filling the boiler with water and then connecting the test pump, as I began pumping up the pressure we noticed several minor leaks which were then rectified. But as we began pumping again water appeared to be escaping into the valve chests and water coming out of the exhaust and into the smokebox.

We checked the regulator plate and regulator puck to make sure that they were fitting correctly, we removed a couple of burs and found that there was a small radius on the underside of the stainless steel plate, and when the three countersunk screws were loosened and removed found that the plate was not sitting down correctly, so after using a counter sink on the hole of the machined face in the block, refitted the plate which now was seating correctly and the regulator assembly.

We then replaced the plate and began pumping again, once again as the water reached the top and began pumping pressure, water was still draining into the valve chests and out via the exhaust and into the smokebox.

I have one of the original showmans which I purchased from another of our club members with the original design of cylinder block, and my other Showmans which is nearing completion has the modified cylinder block with the rear cover plate which when fitted says to use a suitable car filler to blend in so as to make it look like a solid casting.

Now my question to all the builders of recent Road locos and Showmans, are the cylinder blocks still supplied with the modified back cover, or has STW started sending out the original style of cylinder castings. Our colleague has the build instructions for the modified cylinder but has an original cylinder block, which during the first batch of Showmans and Road Locos they had a load of faulty cylinder blocks with pourus castings causing the cylinder blocks to be faulty hence why the new design to make the casting and the machining of the cylinder blocks to be easier.

Are the current cylinder blocks still sent out where the customer has to fit the rear cover plate as per the instructions or are they sent out already finished and made to look like a solid casting ?.

We also had our club boiler inspector helping today as well and we both came up with the conclusion that the cylinder block has a fault somewhere in one of the ports allowing the water to leak into the valve chests (High and Low pressure) and out via the engines exhaust.

Regards
Steve Honey (Heavyhaul)

Hi Steve,

all I can say is that Pied Piper has the modified cylinder. I picked it up end of 2017. Best get into contact with Will that, he will know.

Cheers

Elwood

Many thanks Elwood, for your reply yes Chris who's engine it is, is going to speak to Will or Dean on Monday to see if they have any record of the type of cylinder block they supplied him. Chris said today that he can't remember fitting the modified rear cover.
I must admit from having a good look myself, it does look like one of the original cylinder block castings which they had trouble with hence the modified version.

Regards
Steve Honey (Heavyhaul)

The two main faults the original blocks had were in the passageways under the cylinders. When testing on air one fault was that pressure leaked from the vertical steam chamber going to the regulator straight into the low pressure exhaust which sounds like what you have. The other fault was pressure from the vertical steam chamber going to the regulator going into the inlet of the low pressure cylinder so that any pressure gets the engine running with the regulator closed. Opening the regulator stops the engine as it equalises the pressure.

To be fair it is a very complicated casting especially having blind bores. Redesigning the cylinder block with open bores made the castings much more reliable and they work just as well. The cosmetic difference in appearance especially after they have a few miles under their belt is minimal.

Hi
I’m just wondering what the solution to this was as I seem to have the same problem. I have everything blocked off, regulator and starting valve blanked,and when I pump up for the hydraulic test the water is flowing out the chamber under the cyclinders which comes from the HP exhaust to the LP valve .. I have steamed a few times and the engine always leaked steam into the cyclinders when shut off but I put it down to the regulator not seating properly.. Now I’m worried I have a problem with the cyclinder block as I can’t get it to hold pressure.

Hi James,
Chris got in touch with Dean at STW and Dean suggested he took the cylinder block upto STW factory for them to have a look at.
Chris telephoned me to say that the problem was with the thickness of the blanking plate which is fitted on the underside of the cylinder block. Chris said that a new plate was fitted with sealer and said that this should solve the problem.
Chris then fitted the cylinder block back on his boiler and asked me to go over and recheck. After attaching my test pump and starting to pump, the same thing was happening with water leaking into the smokebox via the exhaust.

Chris contacted STW and said that the problem was still there and that by fitting the new plate had not made a difference to the original problem. Chris was told by STW to put a fire in the engine and to try this to see if it seals the problem. As yet I've not heard anymore from Chris as he was going on holiday, and said he would contact me on his return but he hasn't contacted me, so I'm going to give him a call to see if he has tried to put a light fire in his engine to see if anything has changed.

Regards
Steve (Heavyhaul)

If the block is leaking on test with just water it is unlikely to seal under steam. The design of the cylinder block was changed from having the integral rear cover to the open bore design due to numerous failures in the casting process and whilst being machined. Not sure car body filler will remain in place in a block with steam at 175psi - 191 deg's C.

Ideally the block needs pressure testing off the engine. Sound to be a failure of an internal steam passage.