Kit 20 - Reverser and Regulator

ModelWorks 4 inch Scale Burrell Agricultural Traction Engine
Kit 20 was delivered Friday 26th of May

Kit 20 contents - a lot of small bits this time

Friday: Since I was working on the valve gear yesterday I though a good place to start was the reverser.  I took most of the afternoon to clean up the parts.  This took some time as the laser cut part are covered in what I assume is oxide that is extremely difficult to shift.

I trial assembled the gear guard and reverser in the workshop without encountering any problems.  When I came to fit it I discovered that the tender and hornplates have been pre taped M6 but M5 nuts and bolts have been supplied.  Apart from the wasted effort in tapping the holes this should not be a problem as "the other side" will be well hidden by all the gears. However there is one small problem, one of the bolts securing the reversing quadrant is too short to pass through the various bits and get a nut on the other side.

Saturday: I investigated the clearance issue affecting the reverser and die block.  I could find nothing that I had done wrong.  I decided to temporally abandon the full forward and fully backward slots.  Using the mid gear forward and reverse slots I set the reach rod length to achieve equal die block clearance against the top and bottom of the expansion link.  As it turns out this was about 1mm which is the stated expected clearance for full gear.  

I had no trouble cleaning up and fitting the regulator lever.  After setting up the opening and observing its operation I am suspicious that I have filed the notch at the wrong end.  Something else to think about.  It comes down to which way the regulator should be pushed to shut off the steam; our Burrell can be set up either way.  The notch will work correctly if the valve is set so that with the regulator fully forward steam is shut off.  I have an inkling that full size Burrell's were this way round.  The down side of this arrangement is a that a jolt as the engine starts cause the regulator to open further making the jolt bigger - positive feedback.

Sunday: Not much time on the Burrell but I did get a chance to measure the valve timing.  I made a giant protractor and stuck it to the flywheel using bluetack. The table below gives the angle in degrees before or after bottom/top dead centre for admission and cutoff of steam to the cylinder. I define TDC as the piston fully forward ie closest the front cover. Because of the clearance issue with the die block I was unable to measure some of the events in full gear. I have included in (red) the angle obtained with the reverser out of detent in the fullest attainable position.  In most cases this about half way between the two positions.

To my untrained eye they look pretty good.  I am not sufficiently knowledgeable to know whether full gear is missing or whether the first notch offers too little expansive working.  Depending which is the case the problem either lies with the expansion link/die block, or the travel of the reverser and linkages.

(5/6/05)  I am unsure as to the convention to numbering the reverser quadrant slots.  I have christened the slot that gives the most valve movement as "Full".  My slot 1 gives the least valve movement. In follows that Forward 1 has the earliest cutoff and hence most expansive working.

Monday: Fitting the blower adaptor required that I further reduced the height of the nut a little more that I had done previously.  In fact I ground a pit using my mini-drill.

Whilst cleaning up the brake wheel I though it would be a ideal replacement for the POP's steering wheel but other than my wondering thoughts I had no problems.  With the brake wheel fitted that wraps up kit 20 apart from painting.

I have yet to decide what to paint and what to polish but I suspect that in faithfulness to the prototype I will be painting some of the brass work.

Wednesday: Steve has now been able to understand the die block/expansion link clashes. It took a lot of head scratching on Steve part as initially the control model did not show the problem.  It turns out to be excessive travel of the reverser rather than related to the die block.  In due course we will all be getting replacement reverser quadrants (see below).  Now the issue has been resolved I can get on with the painting.  

Thursday:  I couldn't resist the temptation to try running the Burrell on air.  I spent most of yesterday making up a collection of blanking plates and plugs.  As I did not want to pressurise the boiler I made brass blanking buttons to lie on top of the steam passages inside the regulator valve chest.    

Steve has since told me that we will be getting appropriate blanking plates to enable hydraulic testing of the boiler; so if I had waited I could have save myself the bother.  I used butterfly nuts because that is all I had!

When I connected up the air there was lots of whoosh and not much action.  It turned out to be coming from the cylinder drain cocks.  I had to retire to the workshop to make additional blanking plugs.

Initially the engine would only mange about 3 strokes before my compressor's reservoir was exhausted.  I gave the engine some TLC and plenty of oil and it will now run indefinitely off my compressor.  

Friday: I have spent the day analysing and measuring the Burrell's valve gear.  I have been introduced to the valve design software written by Bill Hall.  In order to measure the lap of the side valve I removed the side valve cover and I was shocked to find RUST.   The innards of the engine were wetted by the condensation from the compressed air that I ran the engine on yesterday.  Apart from smearing oil over the surfaces I had better get used to it rusting.

Now that I have got my head round the subject I am pleased to report that the ModelWorks Burrell valve timing is OK.
My studies indicate that the Forward 2 and Reverse 2 notches on the reverser quadrant are just about the limits of the ideal travel for the reverser.  The Forward 2 slot gives cutoff at 72% and 81% of stroke (depending on piston direction).  When we get our replacement reverser quadrants I expect there will be two further notches toward mid gear that will provide expansive working (cutoff earlier in stroke).  The slots I have christened "Forward 3" and "Reverse 3" will be gone.  I have measured the valve displacement for the Forward 2 position and found that the RMS error between actual and predicted valve position was 0.1mm 

Friday 10 June: I have been putting it off for some time but the time has come for what I hope will be the last big painting session.  In addition to the gear guard supplied with this kit I need to paint the boiler cleading.

ModelWorks supplied the cleading in 5 sections which made it more manageable but I still wanted to find a way to hold them.  I made brackets to grip the edge cleading securing these to a T bar.  This enabled me to freely manipulate the cleading whilst I sprayed both sides with undercoat.  

Friday 24th June: It has been a hot week!
I did manage to complete my spraying task but not without a hiccup.  With all the heat and humidity the air was not that dry from my compressor.  At just the wrong moment a shower of water came out of the gun spoiling the finish of the gear guard.  My only choice was to put it to one side to rub it down later and respray.  Fortunately things behaved themselves after that and I had no problems obtaining a good finish on the boiler cleading. 
 
Monday 4th July: Included with Kit 20 was a replacement reversing quadrant.  I will not try it on the engine until after kit 21.  My thinking is that the gear guard will have to be removed in order to fit the pinion gears to the crank; no point in fitting it twice. 
(30/9/05) See issues found here.

Replacement quadrant in front of original