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.