Rocking Valve Filer & Stowell

[Jasonb]

When Tinglett started posting about his build of Jesse Livingston's Rocking valve Engine a few years ago it got me interested in making one myself.

http://www.modelenginemaker.com/index.php/topic,6798.0.html

At the time the Live Steam article was available on the net and I started to draw up my own version, you can see how far I got in that thread but here it is again to save you looking. I had the general layout of the "castings" done but not much of the detail.



Other engines since took my interest and the "rocker" was but on the back burner. I did look at it a few times but found that the web article was no longer available and I had not downloaded it so did not progress the model any further. with the arrival of the CNC last year I felt that some of the parts would be ideal for making on that so started looking at this engine again, a bit of research into rocking valves and a few of Tinglett's photos gave me enough info to have a go at making up the rest and over a couple of days at the end of May a design was finalised, not easy to see are a complete rework of what I had done previously on te "valve chest" and also how the cylinder mounted to the trunckguide and the cylinder cover itself. At this time I was still in two minds as to whether to include a governor as these engines were offered with and without.



It is not based on any specific engine but takes inspiration from several Filer & Stowell engines found on the net, although mostly Corliss designs they did make "heavy Duty Rocking valve" engines such as the one below which has had quite an influence. The rocking valve engines were a simpler design to the Corliss and used a lot in saw mills where economy was not such as issue as there was an endless supply of offcuts to feed the boiler.



I have not recorded all the parts of the engine being made but will show the more complex ones and other bits of interest.

A block of cast iron was face milled to overall size and then held in the 4-jaw to drill and bore the 22mm trunk guide hole and have the end shaped to receive the previously turned cylinder marking flange which can be seen gauging the fit here.



Then over onto the mill to form the stiffening spine along the top and a recess to take the oiler boss



A couple of threaded end plugs and a suitable shaft were knocked up so the trunk guide could be held in the Er chuck on therotary table and supported by the tailstock at the other end so the curved top and side cut outs could be milled



A couple of slots were added to the underside to take the feet which were JBWelded into place as was the cylinder mounting flange

[Jasonb]

The cylinder was made from two slices off a 50mm steel bar and a chopped up bronze loco cylinder casting that were silver soldered together.



The new cylinder "casting" was held in the soft jaws to bore, face the end and reduce the flange to finished diameter before being reversed round to do the flange and OD on the other end.



Over to the mill do drill and tap M2 on a 10 hole PCD for the trunk guide flange and 6hole PCD of the cylinder cover, just the 10 hole pattern on the other end.



The cylinder cover was a simple turning job that was then drilled for M2 CSK screws and M1.6 for the gland studs



The gland was turned and then screwed to the cover so they could both have the elliptical shape milled as one on the CNC



Holding the cylinder on the rotary table two 2.5mm slots were cut to line up with the valve block's inlets and a third slot milled around the side to join the valves exhaust to a boss that will be on the side of the cylinder.



Three 2.0mm holes were then drilled down from each end to meet the inlet slots and a recess milled to allow the air/stem into the bore.

[Jasonb]

The two bearing supports were profiled from 16mm aluminium plate which was rough cut on the vertial bandsaw and then tapped so it could be screwed to a holding block.



The longer of the two also had it's side profiled where it tapers down to the side of the trunk guide.



The CNC made quick work of these operations rather than multiple setups on the rotary table.

<a href="https://www.youtube.com/watch?v=geKWDVsKAeg" target="_blank">http://www.youtube.com/watch?v=geKWDVsKAeg</a>

The two parts as they will be positioned on the finished engine.



The bearing caps were treated in a similar way making use of their stud holes to fix them to a block that coul dbe held in the mills vice.





With the bearing caps screwed into place the holes for the bearings could be drilled and reamed 10mm, having the bottom of the part against the vice's fixed jaw ensured both bearings would be at equal height.

[Jasonb]

The "valve chest" was silver soldered up from 3 pieces of brass that had been part machined, once cleaned up the bore was taken out to the final 16mm diameter and the end flanges skimmed true to the bore.



Then over to the mill to flycut the top flange true to the other faces and drill & tap the four M1.6 holes for the governor.



That top flange was then set vertical in the vice so that the concave bottom surface could be cut to fit the outside of the cylinder using a boring head



Due to the depth I opted to drill the passages into the valve and just mill in a little way, looks like that milling cutter is near the end of it's life.



The actual valve was cut from 303 stainless with a central pocket much like the usual slide valves plus a reduced diameter most of the way round which sets the length of the valve and allows the air/steam down and into whichever of the two inlets that is exposed. One end was reamed 3mm for a stainless shaft to be Loctited into place.



The valve chest and exhaust boss were bonded to the cylinder with JBWeld.

A simple cast iron cover was turned for the closed end but the one for the spindle end had a recess cut into which the extended support was bonded. This support was turned from brass and then milled away either side before being parted off from the parent bar.

[Johnmcc69]

 
 Looking good!
 
 John

[Jasonb]

Thanks

I had intended to home the trunk guide prior to cutting the two holes in the sides but got carried away so had to lap it which was done with a by hand with a piece of 22mm copper pipe and 600g silicon carbide powder and oil working the pipe in and out while slowly rotating it.

The 22mm dia cross head was turned from 25mm stock until it just started to enter the trunk guide then the piston rod hole was drilled and tapped M5 x 0.5 and the end shaped before cutting off the bar and turning the other end.



I had drilled the tapping hole right through the cross head so it was easy to mount onto the end of a bit of rod with a M4 screw and nut, the rod served as a handle as the crosshead was worked into the trunk guide with 1000g abrasive again using a twisting motion while working it in and out until it moved freely along the whole length



The cross head was then taken to final shape by milling the sides and reaming for the wrist pin



Followed by hollowing out a pocket from the conrod's little end

[gary.a.ayres]

Some really nice shapes going on here.

Great photos too.

 

[Don1966]

Ok Jason how did you make the port face block fit. Was it square or convect before soldering into place? Where’s the photos?
And by the way awesome fab work!


 
Don

[Jasonb]

Don, The basic soldered fabrication was three pieces

1. The circular chamber with flanges on each end with under size boor and over length
2. The top spigot and flange, basic turning then while still on the bar the end had a concave cut done with the boring head so it sat nicely on part1, again flange over thickness
3. Bottom block, had a concave cut done while the boring head was at the same setting used for #2 cut along its length and left flat at the bottom with a machining allowance.

You can see this soldered assembly in the photo I posted earlier (top of page) having the bore cut to finish size and spindle flange face done all at the same setting much like you would a cylinder.



I also posted a photo of the underside being cut to suit the OD of the cylinder body.

[Don1966]

Figure it was Convect, And did you pre tint the Cylinder or block before soldering? Much like I did with my engines....



Don

[Jasonb]

And did you pre tint the Cylinder or block before soldering? Much like I did with my engines....

Tint? do you mean tin? Valve assembly and cylinder were JBWelded together but had I soft soldered them I would either have tinned both surfaces or used solder paste both of which would have ensured there was solder between the passages so no risk of leaking between them, if just feeding in solder from outside it would be hard to ensure full coverage.

[Don1966]

Yes Tin, that’s what I did to my cylinders to insure the port face didn’t have leaks but did it with silver solder. Thanks you, you didn’t bother to explain it in your project and I am always open to new ideas on how to go about doing it. I think I like my way better I had no complications doing it.
And yes just feeding in solder does not cover the layers inside.

 
Don

[Jasonb]

For this engine I wanted a flywheel with quite a wide but thin rim and  oval spokes tapering in width and thickness .



I have often used cast flywheels from other models but could not find anything to suit. Fabrication was an option but by the time I had sourced some thick wall tube, a disc to cut the spokes from and added something to beef up the hub area it worked out cheaper to go for the solid option so I ordered a 30mm length of 130mm diameter EN3 steel.



I decided to rough it out on the lathe and manual mill leaving material on all surfaces.



I did a dummy clearing program to mimic what I had done on the manual machines so that the CNC would not try and remove the metal again and then a clearing program was run starting at the height of the "disc" with a 1mm stepdown that left a finish like this



Then a finishing ramp with 0.2mm stepdown to give the draft angle to the inside of the rim and hub and then carry on down further to shape the spokes with a 6mm dia R1  tool. I have since figured out that this was not the best tactic and I should have use done that gave an even step over irrespective of the angle of the surface which would have resulted in a smoother finish particularly on the more horizontal areas.



It then just needed a bit of fettling with the Dremel to blend the 0.2mm steps and I also added the bits to make it look like a 2 part flywheel.



A couple of coats of filler/primer and it's ready for colour.





Looks like I won't be needing many castings in the future.

<a href="https://www.youtube.com/watch?v=OFS41VbX6DA" target="_blank">http://www.youtube.com/watch?v=OFS41VbX6DA</a>

Starting to look like an engien now

[gary.a.ayres]

Lovely bit of carving on that flywheel, and the engine is starting to take shape.
 

[Jasonb]

The old illustration shows a moulding running around the bottom of the main frame and bearing support castings which I decided to do by screwing a suitably shaped 3mm steel plate to the bottom of the parts. The CNC made quick work of these, first I drilled the various holes so they could be used for additional hold down screws then had the mill cut out the shape leaving a few tabs to keep everything in place.

Out rigger bearing base


Main frame base


And with the castings showing how they replicate the shape but are 1mm larger all round


It was then time to add a few mechanical parts to the "castings" I started by drilling and reaming the holes in either end of the conrod together with milling to thickness



Then transferred to the mill to turn the tapered section between after which the ends were finished off and bearings added.



Two pieces of brass were soft soldered together to form the eccentric strap which was then bored and a recess machined for the end of the flat eccentric rod



I decided to shape the outside manually with the aid of the rotary table, the two rods and their forked ends were quite straight forward so I did not take photos.



The intermediate and rocking levers were done on the CNC forming the boss, tapered sides, rounded ends and placing the holes is just the job for these machines, after milling they were held by the boss so that the bit left in the mill vice could be machined away.



Just need a little more cleanup on the flat surfaces



The eccentric was turned and then drilled and reamed in the mill. Then held on a stub end to turn the groove for the governor drive belt



At this stage there were just about enough parts made to give the engine a try so it was lashed together with a few odd screws and clamped to the mill table to see if there was any life in it.



After a quick tweak of the timing it was off and running

<a href="https://www.youtube.com/watch?v=tC_klQJhhhQ" target="_blank">http://www.youtube.com/watch?v=tC_klQJhhhQ</a>