Rocking Valve Filer & Stowell

[JasonBModerator @jasonb]

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

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. 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 the rotary 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

[JasonBModerator @jasonb]

[JasonBModerator @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.

[JasonBModerator @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.

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.

[JasonBModerator @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 what would normally be 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.

[Ramon WilsonParticipant @ramonwilson3]

Pleased to see this finally make the top of the list Jason, it's all looking good so far.

I like the sloped bearing faces – I wished I'd found that image you have there as I have made my version with a main base very similar to the original article. Confess I haven't got far – messed up the first flywheel in not offsetting far enough when milling the spokes – decided to scale it up a tad so have a second slightly larger flywheel roughed out and the main base made. Had some health issues over the last year or so – very little machining interest as a result so that's where it sits at present. Hopefully things will change this year or next.

Good to see you on yours though – hope you are well and staying safe

Regards – Ramon

[JasonBModerator @jasonb]

Hi Ramon, I was going to e-mail you as I knew you were interested in the Rocking valve, if you want to jump to the end of the book I have posted a couple of videos in the "workshop Progress" thread here, next project is at the bottom of the same page.

Hope you feel upto some engineering soon, still looking forward to that tether car engine.

J

[Ramon WilsonParticipant @ramonwilson3]

Hello Jason,

When I first saw your cad layout in the first post above I thought to myself that's a nice blue rendition – this engine would look good in such a colour. Well, weren't far wrong with that thought – it's an absolute stunner – a truly superb result and a lovely runner too.

Liked your touch of setting it at an angle to the base too – usually do that with a plastic model but have never given a thought to doing so with an engine, truly, a lovely looking model all round. I will continue to follow your posts so keep 'em coming

With regard to machining – well, the intention is always there but the desire has not been I'm afraid. However things are somewhat on the mend now and once other extraneous matters that have also crept in over this time have been dealt with hopefully it won't be too long before I will feel up to making some swarf again.

Keep up with that fine work – if you have anything to add to your previous help on the RV engine it would be nice to hear from you.

Best Regards – Ramon

[JasonBModerator @jasonb]

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 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 wa sdrilled 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

[JasonBModerator @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.

Starting to look like an engine now

[JasonBModerator @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

[JasonBModerator @jasonb]

One item that I wanted to try and replicate on this engine was the metal cylinder cladding often seen on American engines that has a series of recessed "slots" in the surface. I started out by turning down some aluminium tube to the right diameters and then milling clearance for the valve block and exhaust boss.

I then made up a couple of plugs so it could be held in a 3-jaw chuck on the rotary table with tailstock support to mill the 2mm wide grooves.

As I have a 6mm Weldon shank holder for the SX2.7 I opted to use that as it made it easier to see the end of the small cutter, a bit of masking tape with some marks added made sure I stopped feeding at the right place as I don't have a DRO on this machine.

With the milling complete the tube was cut down the middle with my thinnest slitting saw so it could be fitted, a small loose piece also had to be made as it was not possible to slide the exhaust side straight into place.

The few images of engines that I managed to find showed glass oilers for the main bearings and trunk guide, the tops and bottoms were straightforward turning and the "glass" was turned and polished from a square strip cut off a sheet of 6mm perspex.

The governors fitted to these engines look to be Gardner ones which I managed to find a few larger images of, they varied a bit so I took features from each for my design, this is a typical one and you can also just make out the cylinder cladding which is what I was after.

A piece of gauge plate was machined to the required 12mm width and a concave cutting edge milled with a 16mm cutter followed by a slight rounding of the two "points" This was then used to form the body of the governor.

After which the flat sides and various holes were added

The 12 & 18 tooth bevel gears were approx 0.4MOD and cut with a single point cutter

The rest was very small turning and milling work to get to this stage

The 3/16" stainless balls were heated to soften them before being drilled 1.0mm, I decided to fix them with Loctite rather than threading

Due to the small size I decided early on that it would not be a functioning item but just wanted the balls to spin round and swing out.

[JasonBModerator @jasonb]

Thanks for the comment

The last part to make was the exhaust pipe, as I wanted quite a tight bend on this I did not fancy my chances with 8mm copper tube so drew out an elbow supported within a "box" much like I had seen Dave Otto do on the valve for his Pacific Vapour engine which makes the part easy to hold and flip over to machine from both sides on the CNC

While still in it's frame two holes were drilled with a 5mm ball ended mill to form the passage and then counterbored with a flat ended 7mm cutter to accept spigots turned onto the ends of the 8mm pipe

These together with the flange were stuck together with JBWeld and cleaned up with Emery Cloth once set

I decided that a planked floor would suit the engine so some 1mm x 10mm strips were ripped to size and then glued onto a piece of 9mm MDF which was then cut to final size before adding a moulding around the edge. I also set the engine at an angle for a bit of a change which had the added bonus of allowing me to keep the base a bit narrower as there was no need to have it wider for the exhaust.

Right from when I first started to draw this engine I had always visualised it in a light blue, normally I would go to the local Halfords (Car parts shop) but with lockdown that was out of the question so I settled for a company that mixes rattle cans to BS and RAL colours so I could use one of my paint charts rather than pick something that looked nice on the screen but could be completely different in the flesh. The colour I settled on was "pale Roundel Blue"

The air control valve is a dummy but I can unscrew the handwheel to add a drop or two of oil before running which keeps it ticking over nice and smoothly.

Finally the obligatory video, I'm pleased with it's slow speed running and even though the rocking valve engines were meant for high speed use I prefer to see what's going on. For those that endure to the end you will notice that the governor balls are a bit erratic, I think this is down to the drive belt (Mamod) being too short and the spindle that the gear is on is being bowed by the excess tension so will get another to extend it with.

[Ron LadenParticipant @ronladen17547]

One of the nicest engines I have seen, unusual, full of detail and interest, very nice engineering and design even the colour was a good choice plus a very sweet runner, what more can you say…excellent…

Ron

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