In the last couple of days I have made up some basic loco jacks for setting up the Britt (and similar locos). Made from coach bolts and some left over buffer plates. I can see a few improvements to them already but needed something infinitely adjustable.
The springing is not yet adjusted for the weight on the loco springs.
Happy steaming!
Nigel
A bit more work in the last couple of days machining up Princess Marina cylinders finishing off the LH cylinder boring and facing. I won't "bore" you with photos the same as the other day!
Happy steaming!
Nigel
Princess Marina cylinders are progressing with boring and facing. RH cylinder done and onto the left.
Also the Britannia has had a look in with the regulator rodding and pivot and linkages being researched and worked out.
Happy steaming!
Nigel
Some months back the owner of the Princess Marina I've been making bits for asked me to do the cylinders. These were ordered from the UK.
Today was spent measuring the extra metal and machining the faces and bores, the rearmost cover face and the bore being done square to each other.
I've decided to have a go at boring them out on the mill rather than setting them up on the lathe. The quill on the milling machine has a slow feedrate available and it seems to leave a reasonable finish on the first few cuts done.
Last time I used the boring head was boring out a big end bearing for a full size locomotive. The arbor and boring head are attached by a fine thread on the end of the arbor. The boring bar out the end of the boring head in that orientation (horizontal) requires the machine to run in reverse for the tip to cut. The intermittent cut on the big end bearing caused the head to unscrew from the arbor until I realised what was happening! Certainly made me jump at the time as the tool being out a long distance is very unwieldy and makes you think twice about where its going!
So some loctite bearing mount (610?) was used to lock up that thread so it wouldn't unscrew again. Didn't want to use threadlocker as its weaker than 610 and can still be undone with tools, happy to know some heat will get it undone. Wasn't happy to put a weld on it as it was brand new and may need another arbor in time to come!
Happy steaming!
Nigel
Well after a day of mucking around with the valve I have finally managed to get it to blow off with a 5psi pressure drop from open to close. It doesn't "jazz" or "buzz" much but definitely opens and closes without leakage which I am happy with. The final cup clearance was between .0155" and .0160". Any more than that and it starts to blow like a conventional valve, but any less and the pressure drop is abour 7psi.
A lighter gauge spring increased the pressure drop.
I had to make a checksheet for changes to critical dimensions as it was easy to lose track of what it was that had changed or what seemed to be a positive result. I ended up number stamping the end of the spindles.
I also played with the underside of the cup on one of the spindles as the shape I have to get 1mm engagement of cup and secondary seat flattens off the bottom of the cup and would be far more streamlined for any escaping gases. The measurement of reality against my CAD file meant the shape was a little different once the ball had bedded into the seat and cup.
I wondered if the shape of the underside being a recessed cup causes drag/eddying with the escaping air or steam, which I thought would push it open easier without increasing the cup diameter. Didn't seem to make much difference by just putting a groove on the underside. Might have a bit more of a think about that one.
I made a measuring cap to check the engagement of the cup and secondary seat while in situ which assists holding a digital caliper vertical.
Happy steaming!
Nigel
Been still mucking about with the pop safety valve experimenting with different cup diameters. I took 1 thou cuts off the first one until it didn't pop anymore which was about .017" diameter clearance between the cup and the secondary seat.
I have another pop valve drawing which stipulates a .006" clearance but only has 4 exit holes at the top. I made some years ago which have .006" clearance and they seem to work OK.
Still getting ~10psi difference between lift and close and have a few more experiments tomorrow. I've changed the way I made the cup and spindle...both have threads but decided to do it into a blind hole rather than a through hole. The difference was the end of the stainless thread and brass being two different metals had shown that it was pushing the ball to one side once it bedded into the cup after a little bit of operation. The tangent point where the ball was sitting was on the end of the thread. Also found the seat in the body needed a cleanup with the seating tool as the ball had made its own sweet spot on the square edge and flattened it a little.
Happy steaming!
Nigel
