Second Steaming
Monday 20 March

ModelWorks 4 inch Scale Burrell Agricultural Traction Engine 

Monday: I attempted to repair the pump last night.  When I refitted it I was frustrated to find it was leaking from the original spot.  Without much hope of success I removed the pump and stripped it ready for my fourth re-brazing attempt.  When I refitted it the pump body did not leak. A victory but read on.

Encouraged by this I decided to try my second steaming.  I got on much better lighting the fire.  I momentarily dipped a few bits of kindling wool in paraffin and I put this together with some dry wood into the firebox.  I lit a small bit of kindling wood on the shovel and dropped it in and closed the doors.  After a few minutes I added some larger kindling wood. Over the next hour I slowly built up the fire adding a little coal every 5 minutes.  As the picture on the right shows it is essential to keep the fire doors closed.

It took about an hour to reach the point where the safety valve began to lift.  I found that the safety valve lifted at 110 PSI rather than the expected 120 PSI.  I will get the gauge checked but I suspect I will need to adjust the safety valve. 

All this blowing off used up some water so I decided to use the pump.  As the picture on the right shows it sprang a leak.  The good news was the leak was not from the pump casing.  What appears to be happening is that water is escaping past the o-ring and spurting out between the pump body and the gland packing. I have contacted Steve in the hope that there is a simple solution.

There was good news when I tried the injector.  It works!  I turned on the water and as I open the steam valve water spurted out the overflow but as I open it further the overflowing water reduced to a dribble.  I then trimmed the water valve and got the water going into the boiler with the overflow dry.  Over the next hour the safety valve periodically blew.  I did not add any coal to the fire, closed the damper and used the injector as much as I could.  For stationary running I had built far too big a fire.

Misfortune struck as dirt got stuck in the injectors clack valve.  I tried running the injector to clear the crud but the steam being blown back to the injector heated it too much and it refused to pick up.  I was glad that the clack incorporates a cock and I turned this through 90 degrees to isolate the injector. I now had to rely on the crank pump.

By now the fire was cooler and the pressure was begging to fall.  The pump spurted more water than went into the boiler but the water was going up the glass.  I ran for another hour maintaining the water level using the pump.  By keeping a very mean fire I was able to hold the pressure at 50 around PSI.  The fire bed was only about 3/4" deep with a few larger lumps.

The engine ran very well and I believe it is starting to free up. One job I shall add to the "to do list" is to remove the shims from the eccentrics as they were a bit slack.

I stopped putting on any more coal but the engine ran on for another 1/4 hour.

Last time I had to drop the fire in a hurry and I could not find anything to drop it into.  In desperation I used a sheet of Aluminum but had difficulty keeping the hot coals away from the wheels. 

I have now made a "product improvement" and folded this into a large tray.  This worked very well with the added bonus that I could drag the fire out from under the engine.

My second steaming was successful.  I am sure the injector works despite my problems with the clack valve.  I am beginning to learn about the fire and I shall be meaner on the coal in future.   Even the pump is showing encouraging signs.

Tuesday: After my PHD thesis in lubricator linkage geometry I have decided to refit the original lubricator supplied by ModelWorks.   Having used a ratchet based lubricator I now know the strength and weakness of both.  I believe the ultimate reliability of the ratchet is superior but roller clutches will work with a small arm movement.   I changed because I was a bit short of arm movement and ModelWorks have improved the reliability of their lubricators by increasing the diameter of the operating shaft.

Wednesday 29 March: I have been very busy recently sorting out a trailer to transport the Burrell.  I have not yet had time to implement the fix for the leaking pump.  It would seem that I am not the only one to experience water leaking past the pumps O-ring.  The easiest fix  is to fit a second O-ring but after discussion with Steve I have decided to try replacing the O-Ring with 3 rings of 3mm square section PTFE yarn.  

In choosing a trailer to transport the Burrell I have been forced to compromise. If I had a large tow vehicle and plenty of storage space I would have gone for a twin axle covered trailer. Unfortunately I only have a Rover 25 and no storage space.   Having had some previous experience of towing I ruled out trying to get a small light unbraked  trailer.  In any case keeping the gross weight below 750Kg would be difficult.  Opting for a braked trailer only increases my cars towing limit to1000Kg but makes the towing experience less exciting. The down side of a braked trailer is that they are longer and heaver that their unbraked counterparts.

For reasons I am now questioning I opted for a platform trailer from Benderup.  I chose is the discontinued Bravo 225 which has a bed size of 2.2M x 1.4M.  The advantage of this trailer is that it weights only 250Kg and has a maximum width of 1.54M.

I was soon to discover a big down side namely the loading height.  My original concept was to tip the trailer up to bring the back near the ground and with a short ramp run onto the trailer.  When I got the trailer home I fitted an extra long prop stand at the front and tipped the trailer.  As it looked very scary I abandoned this idea and began to wonder why I had brought a trailer with a 0.6M loading height.

I decided to follow conventional wisdom and load with the bed level with prop stands at the back to stop the bed tipping.  Research indicated that I should aim for a maximum ramp gradient of 1 in 3 so I needed 2 metre ramps.

As supplied there was no suitable place to fit a hand winch.  I had hoped to buy a suitable winch post but as none was available I was forced to make my own.  Welding is not one of my skills but after making a prototype I was able to weld up a reasonable winch post.  The horizontal tube reacts the load directly to the bed of the trailer.

Once I had fitted the winch I was keen to try and load the Burrell.  I positioned the Burrell at the foot of the ramp.  I unwound the winch cable and attached it to the front tow hook and began to wind.  Instead of the Burrell moving the cable started to tighten and kink on the winch drum.  Before trying again I shortened the original 15M of cable such that it was fully unwound with the Burrell a few inched from the base of the ramps.  This ensures that there is no slack cable on the drum at the start of the pull. 

As I had a single axle trailer I needed to position the Burrell so that the nose weight was correct.  I am sure I am not the first to use bathroom scales but they made a very effect nose weight gauge.

With a bed 21 inches longer than the Burrell I had plenty adjustment but the correct position turned out to be with the Burrell roughly in the middle (1.5 inches back from centre).  I will need to repeat this excise with the Burrell wet.  My guess is that with a dry tender and a wet boiler the Burrell will be in the middle.  The C of G of the dry Burrell turns out the be roughly 12 inched in front of the rear axle.

Friday:   Yesterday I fixed strong hooks to each corner of the trailer plus the centre back and front.  I used an extra strong fixing at the back of the trailer as this will take the main load during braking.  My original plan was to attach a chain between this and the Burrell's rear tow hook.   When I fitted this I found that it was more vertical that horizontal and hence unable to do its job properly.  Instead I placed a strop around the bottom of the smoke box and ran a lashing under Burrell back to the rear fixing.  To prevent rearward  movement I attached a strap between the Burrell's front tow hook and the front of the trailer.  As I am nervous of the Burrell moving I placed addition lashing around the Burrell rear wheels.  I need to do some more work on these as I am not convinced I have fitted them correctly.  I would also like find a way to utilize the Burrell's rear tow hook as this might enable me to dispense with the wheel straps all together.

I could now turn my attention to preparations for my next and hopefully final steaming before my steam test.

My first task was to fit 3 C's of PTFE packing to the water pump.  I am using 3mm square section PTFE woven yarn available from LSM. In order to cut the C's I wound the yarn around pump's piston and cut  the rings in one go using a scalpel.

To fit the rings I temporally inserted the piston and pushed the PTFE into place, staggering the joints.  

The three rings  filled most of the space previously occupied by the pump gland.  It might have been better to only fit two rings but as I was determined to stop the leak I stuck with three and will fit longer studs.

I shall have to be careful when tightening the gland not to twist it and jam the pump's piston.

Saturday: I started by refitting the pump.  Finger crossed that it works.

I turned my attention to the safety valve.  I had contacted steve an he advised that I should try 1/3 of a turn on the adjustment nut. This is located under a brass cap that is held in place with gasket paste.

I took the opportunity to fit longer studs to the cylinder as the originals for the safety were a bit short.

In the process of removing the safety valve I destroyed the gasket.  ModelWorks originally supplied a spare but as I had already used this It was time to make some more.  Fortunately I had some 1/16 thick proper gasket material that I had previously brought from LSM.

I have made several sets of gasket for my POP and I have achieved good results printing the outline using a inkjet printer.  The image on the right links to a graphic which should be printed at 300dpi.  As a cross check, check the outside dimensions of the gasket.

If the gasket material was paper based I would printed directly onto it but as the material was  graphite loaded I printed on ordinary paper and stuck it to to gasket using spray mount adhesive.  Do not use water based adhesives as they will alter the size of the paper. 

I cut the outline using a scalpel but for the 6mm holes I use a home made punch.  I have made several of these and each consists of a C shaped body with a hole for the punch.  The punch is made from a length of silver steel with the intention of hardening it but I never have.  For these 6mm holes it may be possible to use a stationers punch.

Monday: On my first steaming I found it very difficult to gauge how much water was in the tender. The the try cocks on the side of the tender are only able to indicate completely full or nearly empty.  Steve Traill has fitted a dip stick to his tender and for my second steaming I made and fitted one also.  While I was able to determine how much water was in the tender it was difficult to read the mark on the dip stick.  

For my third steaming I have made a float. This should be easier to read and should enable me to dynamically see the changes in level when using the injector.

I wanted a thin float that would act in line with the rod to minimize the chance of it sticking.  The prototype float is made from expanded polystyrene and if  successful I plan to make a more refined version.  I used a heat gun to seal any loose  polystyrene though I might also give it a coat of paint but first I have to find a paint that won't dissolve the polystyrene .

The level is indicated by a 1/8 stainless rod that runs in a brass bush fixed to the tender.  To drill a hole 1/2" out from the tender side I had to Loctite a drill into a length of bar stock.

How I never lost the lubricator cap for my POP I will never know since it is extremely easy to knock off.  It probably was tell tale tinkle as it hit the floor.  Since I am now going to stick with the ModelWorks lubricator I decided to remake the cap.  Some constructor attach the cap with a short length of chain but I went for a more elaborate solution. 

I milled a new cap and hinge from 3/16" thick brass bar stock.  Now that I have fitted it I am very pleased with the improvement in appearance.  When I get round to repainting the pump I think I will paint the lubricator at the same time.