First Steaming
Monday 13 March

ModelWorks 4 inch Scale Burrell Agricultural Traction Engine 

My garden is not the ideal place to steam the Burrell since there is no suitable flat area.   My drive slopes at 1 in 6 and in order to level the Burrell I have had to made a ramp to support the back wheels.

I tried lighting the fire using barbecue brickets soaked in paraffin.  Unfortunately I left them soaking much longer (days) then recommended by Steve and  I ended up with more paraffin than could be burnt by the available oxygen.  Even if relit it was going out in a few seconds.

All I had was a smoke generator so I dropped the fire and started again.

Having stunk out the neighborhood I went back to using wood.  I started with a few small sticks soaked in paraffin (normally used for the POP) and some larger pieces of dry timber.  I built the fire up slowly adding more wood.  I was soon able to add coal and I continued building the fire without any further problems.

I did notice a dribble of water from the smoke box but as Steve warned this might happen I did not panic and after a while it stopped.

After about an hour there was 50 PSI on the clock and I decided to give the engine a run.  With the drain cocks open it started first time.

I left the engine gently ticking over and I continued to slowly build the fire.  After about another half hour I got to 90 PSI and as the water was now less that 1/2 a glass I decided to try the crank pump.   Unfortunately it leaked. 

With the crank pump out of action I tried the injector with only limited success.  I did manage to fill up the boiler but the injector only worked in fits and starts.

I have talked these problems through with Steve and I understand that more modifications to the injector are needed.  The good news is that Steve Traill has already incorporated the mods and passed his Steam test last Saturday.  

The problem with the pump is down to faulty brazing and I am debating whether  to have a go fixing it myself or sending it back for repair.

I had deliberately built up the fire slowly and after about two hour from lighting the fire the safety valve blew.   The rear safety continued to blow  despite the pressure dropping to 70 PSI at which point I decide to manually reseat it.

Blowing off used up some water so I tried to replenish it using the injector.  As I only had limited success at this and I was becoming suspicious of the water gauge I decide to call it a day and drop the fire.  

I had not planned to drop the fire and did not have a suitable tray to hand.  I pressed into service a sheet of aluminum but I had to quickly knock the hot coals away from the wheels.   Before I steam again I will fold up the sides of this sheet so as to provide protection for the wheels.

I did drive the engine  a short distance up my drive.  To my surprise the front wheel refused to steer.  Even when I got off and walked alongside the engine it would only go in a straight line.  My best guess is that the 1 in 6 slope was loading the differential so much that it was jamming.  I hope this will improve as the engine is run in.

Tuesday: Looking back over yesterdays steaming it was quite successful.  A lot more could have gone wrong and I am thankful that I had no significant leaks.

Thursday: Steve has been busy at ModelWorks and solutions to the injector problems have been devised.  It turns out that Steve was over generous with the size of the injector specifying a 8 pint/minute injector.  Unfortunately not enough steam is reaching the injector to satisfy it's appetite.  The solution is to modify the injector steam cock to increase the size of the internal passages so there is less of a restriction to the steam. Customers will shortly be getting a letter asking for the return of the injectors globe valve body and both clack valve blanking plugs for modification.  A lesser problem affecting the injector is the water supply and it may be beneficial to remove the filter so as to increase water flow.

Having discussed the modification to the globe valve with Steve I decided to tackle this myself.  This is not for the faint hearted and all but the best equipped should return the cocks to Modelworks for Modification.

Each end of the valve body is counterbored with a 3/8" slot drill as deep as possible without breaking through. This leave a short section of the original steam passage and this is elongated with a file to increase its capacity.  The valve seat is not modified in anyway and great care is needed when enlarging the holes not to disturb it.

The easiest way to remove the valve bodies was to remove the steam head.  When I was undoing the pipes I had problems with the globe valves turning.  When it came to refit the steam head I devised a very effective way of holding the globe valves still.  I threaded a length of brass bar 3/8" x 32  and screwed it into the vacant position  normally occupied by the tap assembly. This worked extremely well as I was able to apply force between the bar and spanner without any hint of movement of the body.  I had to be careful not to overdo it as it is possible to snap a fitting if it is over tightened.

I originally planned to return the pump to ModelWorks for repair but having talked this through with Steve I decided to have a go myself.  During manufacture the pumps were held together with internal pegs and tight fitting bushes so it is possible to reheat it without it falling to pieces.

I removed all the paint from the pump body and mechanically cleaned around the affected area and applied flux.  Using a relatively powerful torch I heated the pump and ran in silver solder to the location of the leak.  This went very well and I was happy until I dropped the pump from the brazing hearth onto the floor. 

Even though it only fell a few inches sods law applied and it landed on the threaded bypass boss.  At this point I really wished I had returned the pump to ModelWorks.

Even though I had previously agreed with Steve that ModelWorks would replace the pump if it went wrong I was determined not to be beaten.  I had a similar accident with my Kite spray gun and was able to pull back into shape. 

The dent was only affecting the top 1/4" and I needed to find a way of repairing it without damaging the bore lower down where the "O" ring sealing the bypass cock runs. I made a brass collar to slip over the boss and a moon shaped wedge to go inside.  Using a small tool maker clamp I was able to pull out most of the dent.

The bore was beginning to look salvageable but tests showed it was a few thou out of true and the bypass cock would not fit.  I made a former which I used to grind down the high spots. 

My efforts were rewarded when I got the bypass cock to fit.  The only remaining problem was the thread.  I could not get my 9/16" x 26 die to engage so I cleaned the thread up the best I could with a thread file.  This is a special file with serrated teeth that cut groves to match the tread form.  I was then able to engage the die and run it over the thread. As the picture below left shows it nearly looks as good as new. 

When I first saw the damage I thought the pump was only fit for the bin.  Now that I have cleaned up the pump and repaired the damage I am happy again.  

The re-brazed seams look good but I will not know for sure until I refit and test the pump.

Saturday: I refitted the water pump today.  I decided to test the pump running on air rather than steam.  I filled the tender with water and used my compressor to pressurised the boiler to 50 PSI.   When I closed the bypass I was disappointed to find another leak.   This time the leak was on the top of the pump where the main pump bore joins the clack chambers.  The leak was shooting a very fine filament of water high into the air.   The leak may have been there all along but did not stop the pump working.  When I finished the test and blew down I was surprised how much water was pumped into the boiler.

When I removed the pump and inspected the leaking seam under a magnifier it looked perfect.  Using a scriber I excavated the steam and found a small blemish under the surface.  In preparation for re-silver soldering I used a small burr in my mini drill to open a thin trench around the affected area.  I returned the pump to the brazing hearth and it did not take long to run in some more silver solder.  I hope the pump will be OK now.  One comment I received from Steve is now making more sense.  He said that many pumps can be fixed by just reflowing the existing silver solder.