Burrell Snippets 

ModelWorks 4 inch Scale Burrell Agricultural Traction Engine 
I have divided this page in order to keep in down to a manageable size. The previous snippets are available here.
 

Steam engines at the White Lion Pub Whissendine
The highlight each day was the road run to
the White Lion pub
6th June 2007: I have just returned from the excellent 2007 Whissendine Steam rally.  I would like to say the engine performed well and in the main it did bit I did have trouble maintaining steam pressure towards the end of each day.  On occasions with the blower full on I could not get the pressure above 50 PSI.   I initially put this down to clinker and after a thorough rake and careful firing I could get the pressure to rise higher.  Even after this I was seriously short of draft causing a dull fire and incomplete combustion.  An advantage of being at a rally is that help in available from experienced enginemen and a number of possibilities were identified.

The firebars in my grate are seriously distorted blocking air from entering the centre section of the grate.  The distortion also makes it difficult to rake between the bars to dislodge clinker. Paul showed me the grate from their 4" Foster and I was stuck by how much air there was between the firebars.  Could this be the source of my problem?   

Modelworks Burrell Grate
My distorted grate, note crack at top lh
 


Sue & Paul's grate from their 4" Foster


My brushes and tube scraper (top)
 
Paul also suspected that my tubes might be sooted up.  Once the soot has been baked on Paul explained that a bristle brush can't dislodge it.  It still goes though as the bristles are easily compressed to a smaller diameter.

Paul uses a scrapper consisting of brass washer mounted on the end of a ramrod.  He showed me the rod used for their engine.  It is for tubes slightly smaller than the Burrell but it still met considerable resistance when inserted into my tubes.  Using a too and fro motion he was able to get it through my tubes. The section nearest the fire box was difficult and to my surprise a carbon ring was pushed out together with a lot of soot.  (I had already brushed the tubes!).  Is this too brutal? see below

Once home I used my brass tube brush and was able to dislodge more soot but I could tell that a significant amount remained.  I made a scraper similar to Paul's together with  brass washer 10 thou smaller than the Burrell's tubes.  I had difficulty getting it to go all the way though so I made successively smaller washers until I was able to pass the scraper the full length on the tubes.  This scraper was 30 thou under size.  Having cleared the tubes with a 30 thou undersize scraper I moved on to a scraper 25 thou undersize.  Even though this scraper was only 5 thou bigger it kept jamming and I since I did not like using force to free it I decided to file slots around the periphery of the brass disk.  This made it easier to brake up the soot using a twisting motion.  Using this technique I was able to get the 10 thou undersize scraper through and not wanting to damage my tubes left it at that.  Paul explained than some owners use a reamer and in effect I had made a brass reamer.  I now understand Paul's comment that some owners use a power drill to turn it as I now have a nasty blister on my hand from all the twisting I had to do. Including that scraped by Paul I estimate the soot/clinker in places was 1/16" thick. 
 
The real problem?


Not a dead pigeon but definetly blocked
I had jokingly said it was as if I had a dead pigeon up the chimney and when I got home I had a look.  There was a lot of soot especially around the blast pipe and I estimate that the airway was reduced by half (ie 50% blocked). It did not take long to clear but this is something I am going to have to watch in the future.

I suspect my trouble started when I let the grate clinkered up at the dockyard resulting in a lot of sooty smoke caused by incomplete combustion.  This started a vicious circle in which the tubes a chimney got blocked which in turn continued to cause incomplete combustion. 
 
9 June: I have been busy for the latter half of the week making a new grate.  The existing grate is not going to last much longer as the top has cracked all the way though.  As a temporary measure I had fitted a bar under the crack to prevent it drooping but it is only a matter of time before the grate fails completely.

I have decided to try a grate similar to the one Paul showed me.  The chief advantage of this style of grate is that, as the fire bars are dropped in, they are free to expand.  A secondary consideration is that I will incorporate a much wider air gap.  Ideally I would have preferred to make the fire bars from 25x6mm or even 25x8mm stainless steel but as I had 30x5mm black steel to hand I used that.  I am not convinced stainless is necessary and I will be able to access how black steel wears before ordering the correct size.
 


The old grate has a nasty crack at the top


The new grate fashioned from
30x5mm black steel 
 


Using diamond point chisel to cut fire bar notches
 


Modified rear ashpan support
The fire bar support frame is made from the same 30x5mm steel welded at the corners.  I though that cutting the slots for the fire bars would be an onerous task and then it struck me that it was an ideal job for a diamond point chisel.

The support frame stands on simple legs and is not fixed to the ash pan.  When I fitted the grate to the Burrell I discovered that the back of the ash pan drooped excessively.  I suspect that the old fixed grate rested on the back of the fire box providing some support. 

MW had originally provided a rear ashpan support consisting of a U shaped piece of sheet metal fixed to the hornplate.  Unfortunately with the support in place it is impossible to remove the ashpan.  In order to clear the rear support the ashpan needs to move forward about an inch before it is able to drop.  With the grate floating it is possible to side the ashpan forward but it hits the bottom edge of the fire box before it has cleared the rear support.  Thus to be practical the rear support must only engage on the last 1/2" of the ashpan. 

I made a new support consisting of two plates fixed to the existing hornplate mountings with a 3/8" dia bar between them.  The new support works but if the grate is allowed to drop before it is slid forward the ashpan is jammed between the rear support and firebox.  I hope I have got the ashpan close enough to the fire box to provide a seal as I will need an effective damper given that I have increased the air gaps in the grate.  In the past I have noticed that the damper has little effect on the fire which I have put down to the large gap between the ashpan and the rear of the firebox.
 
10 June 2007: I have had a chance to ask around my club and the consensus is that using a brass scraper is too brutal and risks either damaging a tube or starting a leek at the tube plate.  The most aggressive implement in general use appears to be a phosphor bronze shot gun cleaning brush.  

13 September 2007: Yesterday I took "Little Beastie" to the park to test a new seat I have designed and made.
 

  ^ Clink above to play video
Like most drivers who sit on their engine I have been having trouble with light steering and the front wheels lifting.  I have recently designed and made a new seat that places the drivers weight on a fifth wheel.

The 5th wheel is on a frame that is liked to the Burrell by a pair of swing arms that allows the wheel to move up and down.  It all other respect the seat is rigidly fixed to the Burrell giving all of the advantages of a fixed seat without the drivers weight affect the axle loads.

If you liked the video it can be found here at high quality.  This file is very large (18Mb) so only download it after you have watched the video above.

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