A Robinson in the making. The conclusion.

[Alyn Foundry]

The Robinson Oil engine.

Well over 40 years ago my friend and now curator of the Anson engine museum, Geoff Challinor recovered a Robinson oil engine from near the Scottish border. The engine was in a very rough condition with frost cracked cylinder and totally worn out crankshaft. From early advertising literature it was thought to be either the HA or HB model. The recovered engine was then stored for future restoration. The engine was built somewhere in the latter part of the 1890’s and has fitted the 1895 patent epicyclic drive.

Thirty odd years later and with all of us a lot more savvy the engine got its restoration debut. Another friend of mine, Dave Allen took on the task for the museum. A new crankshaft was cast in Steel along with new Brasses and the cylinder repaired with the latest welding technology. Several months of work later saw its first run at the Anson. At this point in time this engine is considered to be the only survivor of its type and both my sons and I thought worthy of a scale model.

Back in the day Lamp oil was very cheap and plentiful. It was also favoured as a safe fuel for use in the latest “ new fangled “ internal combustion engines that were appearing everywhere. Period advertising made comments about how much cheaper the building insurance was when using lamp oil over the more volatile gasses and spirits that were also being used. These days we know Lamp oil under the generic term of Paraffin or Kerosene, it has a standardised calorific value unlike its earlier forms that varied considerably. Where compression ignition was concerned engines were supplied with a variety of plates that could be fitted to suit different makes of oil. These plates altered the compression pressure ratio to ensure consistent power output depending upon the make of oil.  Different makers had different ideas. For example the Hornsby Akryod used conical shaped Iron rings that were placed inside the rather cavernous inlet/exhaust valve chest. They were bolted to the underside of the cover plate. Others simply had Steel plates that fitted between the end of the conrod and big end Brasses. With the Robinson it doesn’t appear to have had this method of variable compression fitted but as the original was little more than a bare skeleton we don’t know for sure.

Back in 1885 a gentleman by the name of Herbert Akryod Stuart accidentally dropped some lamp oil into a pot of molten Tin whilst he was soldering something, an adjacent oil lamp immediately ignited the vapour. This would be considered an “ Eureka or light bulb “ moment today. He went on to invent the first “ compression ignition “ oil engine where the atomised fuel was sprayed into a “ hot bulb “ and “ auto ignition “ ensued. This principle differs from the Diesel engine where the temperature of the air is raised by compression only. Needless to say that his discovery was taken up by many engine manufacturers all around the world.

Instead of a “ bulb “ the Robinson engine uses a tube, similar to those fitted to early gas engines. HR also simplified the atomisation process by using a “ rattling “ valve system where the air valve carries a secondary, loose seat that vibrates as the air passes. The Paraffin is metered by gravity feed onto the loose seating and gets fractured as it mixes with the incoming air. This, combined with the general heating of the ignition tube and surrounding area of the cylinder head ensures the “ bang “ at the end of the compression stroke.

Finally, the “ all important “ governor. Although the fuel is metered by an adjustable needle this design won’t stop the engine from getting carried away under a “ no load “ condition leading to catastrophic failure. HR used a very simple “ pendulum “ that hangs from the exhaust pushrod that when under normal speed gently rocks from side to side. As the speed increases the rock becomes more powerful and a small pivoted arm starts to lift up a latch that then props open the exhaust valve. Being an atmospherically operated inlet/fuel valve this won’t open because the engine is breathing through the now, permanently open exhaust port. As the engines speed decreases the pivot starts to drop away from the prop the prop then drops back to rest and the four stroke cycle is resumed. This particular governor is only suitable for very rigidly mounted engines, there’s been many a mishap on the rally field where the trolley moves in one direction as the pendulum moves in the other. This effect nullifies the action and the engine becomes un governed.

With the introduction over I’ll be posting some pictures of the construction as we go along. I have now got a working prototype with just the fiddly little governor to do.

  Graham.

Link to the first part of the story here:-

https://www.modelenginemaker.com/index.php/topic,8042.0.html

The attached photos show the original cylinder damage and then the process of machining the cast Steel crankshaft.

[Alyn Foundry]

Here’s a video of the first “ successful “ run of the Robinson Oil engine.

Several previous attempts showed that the compression pressure was way too high with the engine firing at nearly 120 degrees before TDC. Several modifications were made including:- Shortening the conrod by 1/2” or 13 mm. Opening the transfer port to the cylinder head from 3/4” to 1-1/4” inches. A much larger bore stainless Steel ignition tube.

<a href="https://www.youtube.com/watch?v=4MdSeVslvig" target="_blank">http://www.youtube.com/watch?v=4MdSeVslvig</a>

More pictures to follow in the not too distant future.

  Graham.

[Jasonb]

Interesting to see the photos of the repairs to the original, could have done with that for patching up the hole from the wayward core.

[Alyn Foundry]

Interesting to see the photos of the repairs to the original, could have done with that for patching up the hole from the wayward core.

What? This one?

Or even better.

[Jasonb]

That's the one , or was it two?

Not cleaned the core sand out of my one yet to work out where the passage goes.

[Alyn Foundry]

That's the one , or was it two?

Not cleaned the core sand out of my one yet to work out where the passage goes.

Please check my edited post Jason. 

[Admiral_dk]

Very interesting story and Video 

I thought that the Hot Tube would sustain itself after a bit of running - Like the Olde Danish Fishing Vessels - a several Liter Single Cylinder Hot-Bulb 'Semi-Diesel' [youtube1]https://www.youtube.com/watch?v=66t2Zl6w-Ic[/youtube1] (he is cheating and heating the Bulb with electricity).

I must be blind - but I can't see the Guv'nor (have seen it on some of your models Graham) 

Per

[Alyn Foundry]

Hi Per.

The Robinson is slightly different insofar as the ignition needs more temperature externally, these are known as “ permanent lamp engines “ With “ hot bulb “ ignition you have a considerably higher cylinder pressure. The initial heat from the lamp brings up the temperature enough to get the engine running and then the combustion keeps the bulb hot enough to continue.

No, no eyesight problems…. Little Otto took precedence and the Robinson was shelved. The governor has yet to be made and fitted.

  Graham.

[Alyn Foundry]

I won’t bore you with the details of the majority of the castings. I’m sure most are well versed in the mundane things like flywheels, cylinder boring and honing, line boring etc.
The interesting part on this particular engine is the epicyclic reduction gearbox. This was patented around 1895 by H Robinson. The crankshaft drive’s into a pinion with, in this case 12 teeth. An internally cut gear carries, in this case 24 teeth. The two gears are kept in the correct mesh by a carefully machined cast Iron housing. The half time gears outside is eccentric to the concentric pair. This means that as the housing is pegged to the bed the eccentric strap moves back and forth a set distance opening and closing the exhaust valve. The front end of the eccentric strap hangs from a peg sticking out from the exhaust valve chest mounting arrangement.

Horace Robinson described it as a perfect arrangement to stop the Ingres of dust and dirt into the gear train. The gearbox has a front cover to hold the lubricating oil in and stop the gears falling out.

The 1/3rd scale was chosen for a couple of reasons. At 28” ( full size ) a half scale flywheel would be too big for the average model engineer. But more importantly at 1/3rd scale I could use the same gearbox that’s fitted to my Robinson “ Chippy “ engine ( type X ) so no extra tooling would be needed. I was hoping that I could use the X types flywheel but when offered up to the base and cylinder patterns it just didn’t look right at all. I ended up using our 1/2 scale Gardner flywheel instead.

I’ve mentioned this several times about Robinson and Gardner virtually being at opposite ends of the same street. So little is known about their early years of manufacturing it makes me wonder where they got their castings from? I know that Gardner had their own foundry latterly but when you look at some of their early stuff could they have been “ pattern/foundry sharing “ ?

Below are some pictures of the gearbox, crankshaft etc.

As mentioned in my thread. A Robinson from rejects, the special half-time gear is a die casting produced in house.

  Graham.

[crueby]

Fascinating arrangement on those gears, looking forward to seeing a video of that all moving slowly. (hint hint)   

[Admiral_dk]

Another New one for me .... 
Just got to show how little we know / how many different way to skin the proverbial Feline .... 

Per

[Alyn Foundry]

Fascinating arrangement on those gears, looking forward to seeing a video of that all moving slowly. (hint hint)   

Hi Chris.

Well, you could always join us at :- https://www.facebook.com/groups/ALYNFOUNDRYMODELS/

I have recently posted a short video of my son’s gearbox running in slow motion. However, when transferring the video from my iPad over to YouTube it always comes out at normal speed??

  Graham.

[RayW]

In full screen view on YouTube, if you click on the Settings gear wheel at the bottom of the screen, you can select playback speed. Very useful!

[Jasonb]

Or just turn the gearbox over by hand

<a href="https://www.youtube.com/watch?v=bKVMaQw4DVA" target="_blank">http://www.youtube.com/watch?v=bKVMaQw4DVA</a>

I'll get to try out one of Graham's cast internal gears on the one rather than a home cut one. The eccentric strap/rod is also quite a bit longer on this engine than the X-type again I'll have the iron casting for this from my pattern rather than fabricating

[crueby]

Quite a clever setup, thanks for the video clip!  I do not do Facebook.   

[Alyn Foundry]

Thanks to both Ray and Jason. 

I wasn’t quite correct about the Robinson engine in question.  I thought it was my son’s but it’s video of an engine that came back to the “ works “ earlier this year for some tweaking….

<a href="https://www.youtube.com/watch?v=q2eOvxOJb_Q" target="_blank">http://www.youtube.com/watch?v=q2eOvxOJb_Q</a>

Just hit the “ slow “ setting.

   Graham.

[Jasonb]

I don't do much on Facebook but it has it's uses and you can be selective about what you look at.

Currently following Wayne Grennings latest restoration project, What Graham and other Alyn owners get upto and only last week on the Stuart Models group learnt of a Stuart engine that I had never heard of before which you could say is a bad thing as I've now drawn up my rendition and started cutting metal.

It's also been the source of size sand information that have enable dme to make a couple of other engines so can't all be bad.

[Alyn Foundry]

Cylinder and liner.

As with most of my previous scale models, the Robinson use’s a glued in liner. There’s a few good reasons for using this method.
1.  Ease of water jacket provision.
2. Being a blind cylinder, the liner can be bored and more easily honed.
3. Well, that’s about it really….

The cylinder casting was first fettled and put on the milling machine to flat off the base, using the flange top side as a datum. Once down to the correct thickness the casting was then transferred over to the 4 jaw chuck on the lathe. Before that the other flanges were also flatted, one for water the next for the pedestal fuel tank and the last for the sight feed lubricator. Just a couple more, the underside water flange and the face for the exhaust valve chest mounting pad.

We tend to first machine the liner to its outside diameter then bore the cylinder jacket to a slight oversize. This allows the Loctite high strength retainer to do its job properly. These days I leave the outside diameter of the liner in its rough, as cast state. Using a 4 jaw I get the cored hole running as truthfully as possible.  Cores can run off in all directions during casting so using this method can reduce the risk of not cleaning up properly. I then bore out the liner using as large a bar as possible to reduce the “ waft “ and so reduce the risk of a tapered bore. Some tapering is inevitable but you can minimise the effect by a couple of very light finishing cuts. The bored casting is then removed from the chuck and placed on an expanding mandrel. The Robinson didn’t allow much for the use of a separate liner so it has ended up being quite thin. Once on the mandrel the outside is cleaned and trued up, ready for honing.

My last set of stones for my Delapena honing machine disintegrated. The only other person who I knew used this type was Jo, here on the forum. I emailed her to ask if she had any spare stones I could buy. No joy. I tried eBay, a vendor in the USA was offering some but not overseas. What was I to do? Further trawling on t internet I discovered that Delapena were still trading. A very nice man discovered that the company’s website had failed to list the particular stones that I was looking for then proceeded to get them to me the following day. I was back in business. It’s amazing the difference the “ right “ set of stones make! I could spend hours in the past just getting parallel. It took just a couple of minutes. So now all nicely shiny I got back to finishing the cylinder jacket.
Several passes later the cylinder jacket was bored to size. It was then turned end on to make a face for both the cylinder head and exhaust valve cover mounts. Before I could glue in the liner there was one more important job to do, drill the top and bottom waterways. A long series drill was used to pass through the hole where the liner would go and down onto the ledge formed by the core. The holes were drilled to the correct depth and nicely picked up the ones drilled from either side of the water flanges. Before the gluing ceremony began I tentatively drilled the hole for the exhaust tract. Amazingly I managed to centrally pick up the cored hole from the combustion chamber and cleared out the remaining core sand.

The two machined castings were then thoroughly cleaned with Acetone before being liberally coated with glue. They were then put in the airing cupboard overnight to cure.

Since the Delapena incident I have bought a cylinder hone off eBay. I can certainly recommend those that come from India. The engineering is quite good and they certainly do a really good job. ( they are Delapena inspired ) My only complaint is the glue that they use to bond the stones to the metal frame is quite poor. I have used some Epoxy resin to good effect. I don’t use the three legged ones because they can have a tendency to get wider at the openings.

   Graham.

[Jasonb]

Graham, what size was the hone you bought? 34-60mm sounds about right for our uses though it would be nice if it went down to 32mm (1.5")

I was wasting time the other day on Youtube, this guy has a bigger tool but interesting to see how he used the different stones to take the bore out to size and then finish. I quite like his videos though it's bigger stuff than we tend to deal with. Video should start at the honing bit

<a href="https://www.youtube.com/watch?v=u1q2TC3UiX8" target="_blank">http://www.youtube.com/watch?v=u1q2TC3UiX8</a>

[Alyn Foundry]

Hi Jason.

Yep, 34-60 mm. However the stones are carried in little Steel channels and are held to the expanding Brass portions by a couple of screw clamps. I’m sure we could develop a method that used shallower stones to get 32 mm.

Back when working at the motorcycle shop, before I joined them they were using Delapena kit to rebore the cylinders. They used ridiculously coarse stones to start and then moved on to finer grades to finish. Thanks to my background I persuaded the boss to buy a second hand Van Norman boring bar and stand. Within weeks the money saved on the cutting stones paid for the cylinder borer!! The properly bored cylinders only needed a light cross hone to finish.

The beauty of the 4 stone arrangement is that it keeps things concentric once the stones are properly trued up.

   Graham.

[Alyn Foundry]

The piston.

A very essential part of almost all reciprocating engines. Aluminium was just becoming available at the turn of the 19th century. Such an expensive metal that a number of manufacturers actually used it for their name plates and badges rather than Brass! ( 19th century bling ! ) That being the case it wasn’t widely used for early piston engines. The Robinson has a cast Iron piston with the now common gudgeon pin bosses cast into the side walls. There were still many manufacturers that didn’t trust this method and were still using the older yoke and pin fixing . At full scale the engine has quite a large bore and stroke
( 5-1/4” by 6” ) so we were at 1/3rd. 1.750”

The first casting back from the foundry was an absolute nightmare. I had to resort to Diamond technology to knock off some hard spots. I managed the gudgeon pin hole with solid Carbide but I just couldn’t get it properly round. It got a little softer at the crown end for the single Viton “ O “ ring but on testing the engine under power, it burned it out. There was nothing more I could do with this casting so I needed a replacement. I ended up using a Retlas piston casting, thankfully being 1.750” when machined. All went beautifully, partly due to the extra thickness I’d given the pattern. Thus making the casting a little thicker in section than that of the Robinson one.

Now with over 40 years of experience we come to piston rings. I’ve made hundreds of them, broken nearly as many, but not anymore. Back in the day Martin came up with a formula that worked for us. We used the same Iron as the piston, or liner and made the ring to bore diameter. The inside diameter was made to 0.180” smaller. This gives a thickness of 0.090”. We made them 0.090” wide as well, a square section. These rings were then “ cracked “ apart on a suitable mandrel and a very sharp blade, placed at right angles to the ring. A sharp rap with a hammer was all that was needed to crack them apart.

The next operation was to anneal them. Our standard was 0.125” and a group of rings would be placed in the forge on the metal “ gapping “ tool and heated, uniformly until bright Orange. At this temperature the rings would suddenly loose their hold on the tool and fall sideways. They were then allowed to cool naturally.

Are you getting bored yet? There’s more!

The next stage was lapping. On a sharp, flat Oilstone. Martin was a joiner by trade and had a thing for a particular stone from the USA. Washeter if my memory serves me correctly? This grit made short work of getting the edges sharp and crisp. You would constantly be checking the width of the ring with the groove ( the depth was made to 0.095” ) until they fitted snugly.
Nearly there now…. The rings were then correctly gapped to the Heppolite piston ring manual for water cooled cylinders.

Now, if you were lucky, it was time to successfully fit them to the piston. This required a really steady hand, invariably one would break, hence the batch making. And that’s the end of the process. Phew, thank goodness for modern technology.

I discovered Viton “ O “ rings several years ago now and all the previous text goes right out of the window. Measure the finished bore diameter, obtain a 2 mm section ring based upon the inside diameter ( so that’s ID + 4 mm ) make a single 2 mm wide groove in the piston at a depth of roughly 0.002” shy of 2 mm and fit the O ring. As that Meerkat Alexander would say, “ simples “

I have been using Viton rings for several years now even refitting my much tired rally engines with them. They work exceptionally well and don’t require any special lubrication either.

   Graham.

Robinson Oil engine with single Viton ring.

[Jo]

Are these the India honing sets you mentioned Graham : https://www.ebay.co.uk/itm/393155824129

They seem to have a good range (but are not as cheap as the 3 legged hones)

Jo

[Alyn Foundry]

Morning Jo.

Yes, that’s the type but they have jumped up in price hugely since April. I got mine at around the 30/40 pound mark with £10.00 express shipping. I got it within 4 days of ordering. With both the Robinson and Little Otto having a 44 mm bore diameter this was beyond the scope of my Delapena machine’s capability.

I know you’re familiar with honing as you have the same machine as me. The tool carries a pair of adjustable stones on a special, parallel mandrel. Opposite the stones are the “ Brass or Aluminium shoes “ that contact the bore. With this method of contact it ensures that the stones cut to the bore because they’re mechanically held. The 3 legged types are spring loaded and pivoted on the stone centre. This can cause a couple of problems. Any hard spots will push the stones away from cutting. And, if you’re over zealous on the stroke the ends can become “ Bell mouthed “ because of the pivot.

Now before I start a war, there’s nothing wrong with the latter mentioned hones. If used correctly they do their job. However for doing commercial work you go with tried and tested equipment. For us folks that build engines over and over again the little extra price is well worth it in the long run.

  Graham.

[Alyn Foundry]

The Crankshaft.

As Per put it “ there’s many a way to skin the proverbial feline “ indeed there is, particularly with the crankshaft.

Being lazy, my method is the “ composite “ build. I use ground stock/drill stock for the shafts and pin. The main shaft is centre spotted to aid any warp correction later. Separately cut Steel billet for the webs. Having recently ruined an expensive horizontal cutter trying to cut the keyway after Silver soldering I now cut the keyways before soldering.
With this method you need to accurately drill and ream the webs as a pair then place them on a perfectly flat firebrick with a decent flux covering the joints to be soldered. Having tried many fluxes over the years only one has stood the test consistently. Tenacity No 5. Specifically designed for long heated ferrous metals. With plenty of firebricks placed around the shaft I start playing the heat from end to end. This gets the main shaft expanding outwards before you concentrate the heat on the 4 joints being soldered. I tend to cut the Silver solder into little pieces and place them on the fluxed joint transitions. Experience has shown that a 1/8” diameter cut to 3/16” long will adequately fill each joint. This doesn’t stop me from hovering around with stick in hand as a “ just in case “ moment might occur. The shaft is then allowed to cool naturally before being “ pickled “ for 24 hours in an Acetic acid bath. This removes any unwanted flux residues. Once pickled and cleaned the crankshaft can have the main shaft metal removed from between the webs to form the nearly completed crankshaft. Now put in the lathe, the crankshaft can be checked for truth. I have a very accurate chuck for this task but obviously known for truth collets work just as well. A DTI is placed on the far end of the shaft and any runout noted. By having a centre spot the shaft can be nudged using a solid centre from the tailstock. Once trued, and a packer placed between the gap you can now machine the big end radius and clean up any excess solder at the main bearing sides. To true up the crankpin I have a special jig that’s held in the 4 jaw chuck that carries the shaft and puts the crankpin on lathe centre. You can now clean up the pin and do the other radius on the webs. All that remains is to carefully clean and polish the webs and shafts with fine grade Emery cloth. The method described above can be partially used for cast crankshaft’s too.

As a footnote and totally my own opinion, I don’t believe that pinning is a good idea where composite crankshaft’s are concerned. Particularly on larger, slow running and with heavy flywheel’d engines. Rather than aiding the joints they have a tendency to weaken and actually reduce the overall strength that a good soldered joint can provide. We are talking about some quite dynamic forces here. This comment is based upon years of experience and having tried just about everything.

If you’ve got plenty of time and patience, I have neither, the ultimate crankshaft is cut from suitable billet Steel in the form of an elongated “ E “ shape. One end spotted for both shaft centre line and pin centre line. With the aid of a 4 jaw chuck you can then hack your way down to form the shafts and webs before turning it around to form the crankpin and inside webs. You will see that Dave welded on the extensions to the casting for the full size replacement.

Being a purist the only good keyway is a horizontally cut keyway. My old Denbigh mill makes an excellent job of this task. I just centralise the shaft in the vice, set a 0.065” cut and then go do something else whilst it gets on with the work. All that’s required is a light lick with a Diamond file to clean up the cut edges. They’re really sharp and have caused more leaks of the “ Claret “ than anything else that I can think of !

It’s very probable that the original engine had its crankshaft made, down the road at Gardner’s machine shop. Having had the pleasure of speaking to an early apprentice he told me that one of his first jobs was drilling the through holes in Steel plate billet ready for the slotting machine. The rough shape would be slotted out before moving over to one of the “ in house “ designed crankshaft lathes. I believe designed by Charles Gardner. Luckily one or two of these machines survive and are kept at the Anson engine museum.

  Graham.

[Alyn Foundry]

Number 2 son making his scale Gardner crankshaft.

You might notice that one of the little pieces of Silver solder slipped away needing a little help from dad.

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

  Graham.

[Admiral_dk]

Thank you for a very imformative Video 

I first noticed that he brought the colour up to Red-Orange and thought that this would have Flunked my Test back in time - we where Told in no Uncertain Manner, that if you Ever got it that Hot - you have Ruined the whole Solder Process (should be Golden-Straw) -> take it all apart, Rinse, Clean and Start over again ....

.... hmm - it probably has everything to do with the Flux & Solder Combo used here - compared to what we where taught, to use back then (1979) 

Next I noticed that the Flux started to go 'Liquid' - followed by the Solder doing the same - so that kind of confirmed that it is a very different Solder to back then ....

That begs the question - what Solder do you use in the Video (the Flux has been told) ?

Per

[Alyn Foundry]

Hi Per.

You are most definitely correct about the heat. Back in the day the Ferrous material would have oxidised, preventing the joint to be made.

Thanks to the Tenacity number 5 formulation this allows for much higher and prolonged heat without oxidisation of Ferrous material.

The Silver solder is Oerlikon brand and costed over £9.00 per rod over 10 years ago. I bought a whole pack, way over £100.00’s worth. I can’t imagine what the cost would be today! 

  Graham.

[Jo]

Let me teach you a little trick Graham to save your fingers getting burnt 

Find yourself an old bit of copper tube say 6mm O/D about 30cm long. About 50mm from the end bend it a bit so that when you poke a length of silver solder into the tube it holds the silver solder in place. When you want to apply silver solder to a job hold onto the copper tube and stick 20 or 30mm out of the end of the tube. Worth lightly heating the silver solder and sticking it into the flux before applying it to the job 

Jo

[Alyn Foundry]

Thanks Jo, that’s a very useful tip for one and all. 

Typically things go bosoms up when you’re filming. Non of us expected the solder to fall off the joint but it does happen. My brand new side cutters got a serious baptism of fire as they were the closest thing to hand.

The Sievert burner is massive @ 30 mm bore and was a snip @ 50 pence, brand new, at a car boot sale many years ago. They didn’t know what it was. I also got a full bottle of Tinmans solder paste for a quid. Lucky me….

  Graham.

[Alyn Foundry]

The conrod.

Or connecting, rod is made from ordinary mild Steel. A suitable length of mild steel is marked out with the big end and small end  centre spotted. Before cutting through the big end centre line a pair of holes are drilled and tapped, end on to allow for the conrod to be fitted with its bearings and then bolted onto the crankshaft. Once the cut ends are properly cleaned up the cap can be bolted back ready for drilling and reaming. This can be done on the milling machine or even an accurate pillar drill. The only critical point is that both holes need to be parallel with each other. The model is trying out some, off the shelf Glacier bushes for the small end bearing and a pair, of well tried Zinc alloy shells for the big end.

Once the holes are finished the surplus metal was removed by using an angle grinder fitted with a thin cutting disc. I hadn’t tried this method before mainly because I didn’t know about their existence until number 2 son brought some home for me to try. With a steady hand the amount of metal you can remove is amazing. You can even dig down, between cross cuts if you’re careful. The roughed out rod was then placed on my little used Harrison L 5 that has a taper turning attachment and a traditional looking conrod emerged from the swarf.

The top slide was used to radius both big and little end eyes to finish. All that remains will be to drill through the big end cap holes and replace the bolts with the correct looking fixings.

I have used Zinc alloy for many engine parts over the years, I refitted my Gardner with both big end and mains. The full size engine had Babbitt but at half scale it’s a difficult material to work with. I chose Bronze at the time. Now fitted with Zinc they have done hours of display time and haven’t worn either themselves or, in the case of Bronze, the crankshaft. Pictured is the half mould and ejector and the castings. The extra length serves two purposes, head for the casting and the chucking stub for machining.

   Graham.

[Alyn Foundry]

Rather than mess with my last post having realised there should have been some extra content….

The most important thing I failed to mention was the accuracy of the finished components. If the mould is made to size then the cold casting will end up being just fractionally smaller than the original dimension. This means that minimal extra machining is involved. Zinc alloy has quite a low melting temperature and I would seriously recommend that the more enterprising members give it a try. Here’s a short video of making a bearing for our Gardner gas engine.

<a href="https://www.youtube.com/watch?v=tXp8hEamWtY" target="_blank">http://www.youtube.com/watch?v=tXp8hEamWtY</a>

The broken glass used to seal the mould bottom came from our multi fuel stove window.

  Graham.

[Alyn Foundry]

A short one today.

Exhaust valve chest.

This will take little to describe and just a bit longer to machine. A solid Iron casting with the correct shape is placed into the 4 jaw chuck. It is then centred up to itself. A quick face off before drilling and reaming to 0.125” for the exhaust valve. I used to have home made tools to form the exhaust tract but I have recently discovered the cutters used for magnetic drills. These cut a neat hole but leave a central core which makes for a great valve guide. All that’s required to finish the job is cut back the guide a bit and cut the valve seat.

The casting is removed from the lathe chuck and transferred over to the pillar drill for the exhaust outlet hole. In this case drilled and tapped to 1/4” BSP. The two by 2 BA clearance holes will be drilled later when the chest is correctly mated to the cylinder casting.

I told you it wouldn’t take long….

[Jasonb]

Working drawings, whatever next

[Alyn Foundry]

Working drawings, whatever next

Definitely not as good as yours Jason but Mathew got the picture.   

[Alyn Foundry]

Cylinder head.

Another simple casting, mainly solid with a small cored cavity at the front for the ignition tube and vaporiser.

After the usual fettling of flash etc I needed to use my smaller 4 jaw chuck to handle this casting. I had already flatted off the top flange previously in the milling machine. Initially I bored a 19 mm hole half way and then dropped down to 7.5 mm for the ignition tube thread. The front face was cleaned up and brought to the correct thickness. I also machined its edge. The casting was then turned through 90 degrees to bore out the inlet valve cavity. The casting was then moved over to the pillar drill for the inlet cavity connection hole. At this point I hadn’t made the inlet valve chest so the cylinder head was then put on the rotary table and the 3 by 2 BA clearance holes drilled for its mounting to the cylinder.

Once the inlet valve chest had been machined it was temporarily glued to the top flange and the 2 BA tapping holes drilled as a pair. There’s not much more to this component other than tapping for the valve chest studs and an
8 x 0.75 thread for the stainless Steel ignition tube. The hardest bit was the small opening at the front for where the lamp burns. Even Carbide wouldn’t touch it!

As an additional note, the combustion space ended up being opened up to 30 mm as the compression pressure was too high initially.
 
First picture. Original, burnt out cylinder head.
Second picture. Loosely fitted to the cylinder.
   Graham.

[Alyn Foundry]

Inlet valve chest.

Just an elongated flange really. However there’s a little more to it than that.

History first. The patent granted to Horace Robinson shows a valve with a double seating. The arrangement caused the liquid fuel to fracture into smaller droplets aiding vaporisation. This arrangement was considered but I decided upon using the same valve as that fitted to my Robinson X type replica. This is a simple “ flat “ valve closing off six holes from the outside. Five of the holes admit air and the sixth has the fuel metering control valve fitted. The flat valve always rattles when opening so I figured this would be enough for the model. My guess turned out to be successful so I’m running with it. This valve works very well with the Paraffin fuel but with gas there’s always a little leakage.

There’s not much to explain about the machining side, once trued up in the 4 jaw chuck it was just a matter of drilling and reaming the 1/8” hole for the valve stem. Then cleaning the front face for the valve to seat against. A little tip, don’t forget to relieve the central hole as you always get a chamfer between stem and valve. The casting was then offered up to the rotary table to drill the six holes for air and fuel. The valve was hacked out of some mild Steel bar and then the finished article put on the bandsaw to separate it from the stock. I’ve tried to part things off in the past but usually disaster strikes and the whole exercise ends up in the bin. Better to be safe than sorry these days.

The most tedious part is “ grinding in “ because trying to rush things with power usually puts scores in the metal that are a real pain in the proverbial to remove. Just good old fashioned elbow grease and patience gets the job done. I have a small tin of fine Carborundum power that will last the family several generations.

For testing the engine I used a steam blow off valve for the fuel control but I might have to rethink this as it gets too hot to touch after a few minutes.

The first two pictures are excerpts from H Robinson’s patent application.

The other two are fairly self explanatory. Including the senior moment with the indexing! 

   Graham.

[Admiral_dk]

The other two are fairly self explanatory. Including the senior moment with the indexing! 

When we are young - the excuse (explanation) is usually down to lack of Experience ....
And when we get too  to use that one - it's called a 'Senior Moment' .... 
... and I have completely lost track on both accounts 

Per

[Alyn Foundry]

Have I forgotten anything?

I’m sure you’ll let me know. Please feel free to ask questions.

As with all my previous builds the engine is assembled bit by bit. The conrod length was found by inserting the piston into the bore just touching the end and then relieving it. This turned out to be way too much compression so a second rod was made to leave 13 mm space. In all cases the fitting of parts is found by offering one up against the next. I then leave it up to the draughtsman to finalise the measurements. Unlike some engines the Robinson is fairly simple in construction and a testament to its inventor.

As stated previously the first run saw the engine trying to fire at around 120 degrees before TDC. Only by the use of a power drill was it able to run. A call to the museum saw the cylinder head being removed to find that the combustion space happened to be 1500.00” not 0.010” like I had got! Hence the shortening of the conrod. The second thing that became apparent was the connection between cylinder and head was also larger than imagined. More remedial work was required, also mentioned earlier.

The next test run was amazing, I could use a single pull on the flywheel and away she went.

So I’m now at a point where the model is a good runner leaving me with the rather fiddly bits left to do. The governor….

At this time I literally have no idea whether this is going to work using liquid fuel. With gas I don’t see a problem but the liquid fuel will keep dripping into the valve seat and we could end up flooding during the “ miss “ cycles. Only time will tell.

Another problem to solve is the permanent lamp. It would be really neat to have a fully functional Paraffin blowlamp but I fear the scale might be a little too small. I’m toying with the idea of a small Paraffin wick lamp but instead of Glass a metal chimney to pull sufficient air to create a clean combustion ( Blue flame ) just like the Aladdin mantle over wick lamps. The exhaust would then be funnelled directly under the ignition tube.

As I close this chapter I would like to thank Jason Ballamy for his help with some of the more complicated patterns and look forward to seeing his Robinson HA engine emerge from his workshop.

Pictures of the  “ pendulum “ governor assembly as fitted to the original engine.

   Graham.

[Admiral_dk]

Great result and an interesting story     

If you really desire a mini blow torch - have a look at Find Hansen and his miniature diesels and semidiesels - the later have mini blow torches. As others have found out - he is not really showing much more than what you can see in his YouTube Videos.

Per

[Jasonb]

That 1/4 scale Pool oil engine that was posted today on FB had quite a dinky blowlamp

[Alyn Foundry]

Yes, I’m guessing at Spirit fuelled rather than Paraffin.