Burrell Snippets 2008 Please read disclaimer

3rd March 2008:  Easter is very early this year and I have already begun to prepare the Burrell for the Medway Festival of Steam & Transport.  Over the last few week I have attending to a few little niggles I noted towards the end of last season.   I have remade the seating for the gauge glass's blow down cock as it has been leaking.  This did not take long as I had previously made the necessary tooling.

Drip tray fitted to catch oil

I have found that oil dribbles from the cylinder glands and then trickles down around the boiler.  This has the effect of making the engine very dirty as dirt sticks to the oil.  In an attempt to stop this I have made and fitted a drip tray behind the cylinder.  The drip tray is "L" shaped fixed to the bottom slide bar.  I made the tray by beating a brass sheet over a specially shaped wooden former.  The dimensions of the former used can be found here.  When forming the lip progress was slow as the brass sheet needed frequent annealing. 

As last season progressed the regulator began to leak again.  Examining the regulator it was covered in a fine deposit that was either dried on water treatment or rust.  Since the Burrell's lubricator feed is after the regulator the regulator's valve face is never oiled.  In an attempt to improve matters I have drilled a passage in the base of the safety valve through which I can squirt oil after steaming.

In readiness for my annual boiler test on Wednesday I had a steam up last Friday.   I had a major problem with the lubrication - it didn't!  On draining the oil I discovered that the crank pin that pushs the plunger had dropped out.  Originally this had been Loctited and I suspect that the Lotictite had been weekend by my steam oil.  To avoid a repeat I quickly silver soldered the pin in place and was once again able to get steam oil into the cylinder.  I was disappointed to find that cleaning and oiling the regulator valve face had not improved the leak.

February: Out on the road

Success - Solid blue around the regulator valve

Monday: I am determined to fix the regulator as I believe it is unacceptable for the engine to run with the regulator closed.   On reflecting my previous attempts I concluded that the critical area is under the regulator in its closed position.  It does not matter if their are isolated depressions provided there is a "ring of blue" around the regulator when rubbed with a flat plate coated with engineers blue.

I improvised a scraper by sharpening the end of a needle file and began the painstaking process.  Since it is hard to work near the edge of the regulator channel I cut a shallow grove either side.  At first the blue was not showing at all in the centre and all my scrapings were at the ends.  As these areas are not under the closed valve I was less concerned at keep these area flat than removing metal quickly.  As blue started to show around the regulator valve took greater care.  I was extremely pleased when I achieved my desired "ring of blue"  around the regulator valve port.  I have no intention of ever using wet and dry on a regulator again and left the valve port with an as scraped finish.  Time will tell if I have finally fixed the problem.

With the prospect of a wintry Easter I took the engine for a run in the park on Wednesday

The modified lubricator linkage

20 March:  I took the engine for a run in the park yesterday as I don't think I am going to have much opportunity this weekend.  I am booked to attend Chatham Dockyard but if I believe the weather forecast the snow may prevent me getting out of my estate.

Cleaning the engine after my run was much quicker following my addition of a drip tray under the motion. No more tar and feathering or in my case oiler and ashing.  I wish I fitted a drip tray right form the start.

In another modification, suggested by Alan Phillips, I have changed the lubricator linkage so that it is driven  by the reverse eccentric.  This ensures consistent operation of the lubricator irrespective of the position of the reverser.   I was surprised how easy the modification was to perform and the clean lines of the result.  My only problem now is that I am using a little too much oil.

Lubricator test rig

167 April: The easter rally at the dockyard was very cold with plenty of wintry showers.  The lubricator proved very reliable but I got though loads of steam oil.  When I came to clean the engine the chimney was gaggled with oily soot.  My first concern was that I would run out of steam oil so I ordered 20 liters from Morris Lubricants. 

In an attempt to reduce the amount of oil used by the engine I have fitted reduced the thickness of the spacer between the two "O" rings.  To keep the total thickness the same I have introduced a compensating spacer before the first "O" ring.  To simplify testing I have built a simple test jig in which the lubricator is operated by a cam driven by an electric motor.  In order to test the lubricator under load I have used a spare small boiler as a pressurised receiver.

Using this set up I confirmed that the oiler delivery is excessive.  I tried the lubricator with no spacer between the "O" rings and the delivery was still excessive.  After all the battles to get the lubricator working this was turning into an unexpected challenge.

The ModelWorks lubricator uses a 1/8" diameter ram and in an attempt to reduce output I made a new lubricator pump using a 2mm diameter ram.   I had to compromise the design as I found it very difficult to find "O" rings with an internal bore less than 1/8".  The only small "O" rings I could find were 4mm outside 2mm inside.   The new pump supplied very little oil when working to atmosphere and none when working against pressure.  I put this down to the diameter of the small wall of the "O" ring; 1mm instead of 1/6".

 As the original pump is a tried and tested design I gave it another chance.  Watching the pump outfall I noticed that each stoke delivered a large drop of oil, far bigger than the volume between the two "O" rings.  I surmised that the volume was more akin to the volume between the end of the oil entry port and the final "O" ring.  Even though my attempt at making a new pump was unsuccessful it had enabled me to get a good understand as to how the pump operates which I shall now explain.

Section through lubricator

Starting on the return stroke with the ram just touching the ball.  The ball provides a good seal against the final "O" ring and as the ram goes back a vacuum is created in the cylinder made between the two "O" rings.  When the tip of the ram passes the entry ports oil from the tank oil is sucked into the cylinder from the tank by the vacuum.  On the forward stroke oil escapes out through the entry port until the ram is sealed in the cylinder.  The intention is that this is not until the tip reaches the first "O" ring.  As the froward stroke continues the oil is compressed pushing the ball off its seating allowing a blob of pressurised oil to enter the deliver pipe.  As the return stroke starts the ball reseats preventing the pressure falling in the delivery pipe.  I have noticed that the ram actually touches the ball and pushes it a little way up the delivery pipe.  Provided the ram touches the ball I don't believe the amount of over travel is material.  The volume of oil pumped is that contained between the first and second "O" ring.

I believe my current over supply problem is due to too good a fit between the ram and the pumps body forming a perfect seal as soon as the ram passed the entry ports.   In my previous attempts to get the lubricator working when my problem was no oil I had made sure the ram was a good fit in the body.  To rectify this and allow the oil to squidge past the ram until the first "O" ring is reached I drilled out the bottom section of the body to 3.6mm diameter to a depth of 1/6".  O retesting the lubricator I was pleased to find I had reduced the rate of delivery.  Testing the lubricator against 80 psi I found that it used about 1/4" depth of oil in the tank in a hour with the crank operating at 140 rpm.  I am happy with this though I cannot say for sure until I have tested the lubricator on the engine in steam.