Burrell Snippets 

ModelWorks 4 inch Scale Burrell Agricultural Traction Engine 

Guildford Rally 2006: I had a enjoyable time at the Guildford rally but I did have a frightening incident.  After I had raised steam I went for a drive and everything was fine except that the pressure  never went above 100psi so I returned to my peg to check out the fire.  

With a little attention to the fire I soon had the safeties lifting.  The fun started when I went to move off.  I found the regulator stiff and the engine did not start to move until the regulator was wide open.  The next thing I remember was the engine speeding up out of control.  Closing the regulator made no difference and the engine continued to accelerate.  I pulled the reverser back but missed mid gear as the lever is stiff to operate when in motion.  After a few backward and forward lurches involving several wheelies I managed to find mid gear. 

With the engine stationary and out of gear I investigated.  The regulator rod moved as normal but if found that "Off" had moved to the middle of its range.  It was only then that I realised what had happened; the regulator valve had slid down the control rod.  By taking note of the new "Off" position I could have continued to use the engine but did not consider this safe so dropped the fire.  I did this in an orderly fashion initially pumping in water to cool the boiler and only dropping the grate once the fire subdued.

Once the engine had cooled I removed the safety valve and refixed the valve in its correct position.  I have since dimpled the control rod shaft so that the valve will never slide again.

I have recently been contacted by Steve Traill who tells a similar story.  His regulator jammed open but in his case it was caused by the safety valve adjusting nut's blanking cap falling down into the works.  Fortunately for Steve he only had 40psi on the clock and he was able to stall the engine using the band brake.  Steve's blanking cap is now in his tool box where it will remain.  Not wanting another regulator jam I have also removed my blanking cap.

I fixed one of the plates directly to the cladding on the left hand side.  In order to get a snug fit I milled a 5" radius on the back of the plate.  I did this using a smart function on the DRO I have recently installed on the mill. The other plate is fixed to the tool box

.16th August 2006:  Having received positive feedback on the item on the safety valve cap I have decided to use the page to detail operational issues affecting the Burrell.  If something untoward happens to you please let me know so that I can warn other constructors.
 

Little Beastie in trouble: Whilst winching onto trailer the front axle turned only stopped by the lock chains The culprit - any over efficient worm gear I eventually locked the steering using a luggage strap

Today I was loading the Burrell in preparation for the Detling Steam Rally when near disaster stuck. Little Beastie nearly fell off the trailer ramps.

The last rally I attended was the Waldershare Steam Fair and unfortunately the rally field was rough cow pasture from which the cows had only recently been removed.   As the day wore on the steering became very loose and the engine refused to go in a straight line but instead turning into the many potholes.  It felt like the steering chains were slack but on checking them I found them to be OK.  When I had loaded the engine onto the flat bed of the trailer the reason for the trouble became apparent.   I found that I could move (steer) the front axle with finger tip pressure.  It is hard to believe that a worm can be back driven but when I pushed the front axle the steering wheel span rapidly.   

From my engineering days I know that a worm can be back driven if it is "too" efficient.  I had though that the only consequence of this feature was that I would no longer be able to take my hand off the steering wheel whilst driving but whilst loading the Burrell today I found a darker side.

As the front wheels of the Burrell reached the top of the ramp the front axle suddenly swung to full lock.  Fortunately my ramps are wide enough and the axle was arrested by the locking chains before the wheel dropped off the ramp.  I found it very difficult to straighten the axle as each time I let go of the steering wheel the axle started to move.  Initially I prevented this by chocking the front wheels but to enable me to continue winching I locked the steering wheel using a luggage strap.

This is something I am going to have to watch but as it is going to be a pain I shall be looking for a ways to reduce the efficiency of the worm gear.  Perhaps I should stop oiling it!

19 August: A great advantage of attending steam rallies is the chance it gives to talk to other model engineers.  Today I attended the Detling Steam rally and had a chance to discus my steering problem.  It would seem that it is usual to be able to back drive the steering.  I tried pushing the front axle of two 4" engines and in both cases the axle moved and the steering wheel span. 

The bottom line is that it is normal for the front axle to move on its own and it is always necessary to watch out for this when winching onto a trailer.

20 August:  I was pleased to find "Prince" a Burrell single cylinder 7nhp Agricultural Traction Engine belted up to a saw bench.  With the engines side by side I could see that their general appearance was the same but I could find differences in detail.  Despite the differences I believe that "Prince" is a close to our models as I am ever likely to find.

"Little Beastie" spent most of Sunday Afternoon next to Prince and many members of the public though "Prince" had brought along its baby.

21 August: The down side of being near a saw bench is that the engine got covered in saw dust.  I had hoped it would have blown off on the way home but as the engine was covered in a film of oil it stuck fast.  I spent most of today removing genuine Burrell saw dust.

Whilst decommissioning the engine I noticed that the lubricator was not working properly.  It turned out that the check valve was offering too much resistance.  On striping the check valve I found that the "O" ring had grown and was getting trapped on the side of the valve's body.  I guess the "O" ring had been affected by the oil.  Rather than replace the "O" ring I bored out a slight recess  inside the body.  This allowed the "O" ring to float freely and when I reassembled the lubrication system all was fine.