Little Otto

[Alyn Foundry]

Little Otto.

Back in 1873 Nicolaus August Otto had a patent granted for a Caloric engine. We now call this type of engine a Vacuum or flame gulper.

The working principle is very simple. At piston TDC a port is opened to allow a volume of heated air to be drawn into the cylinder. This heated air is furnished by the addition of either a flammable gas or liquid hydrocarbon. As the piston descends towards BDC the admission port is closed, sealing the cylinder. As the heated air is now enclosed within the water cooled cylinder it rapidly loses its heat and becomes much smaller in volume. The volume decreases so rapidly that a partial vacuum now exists within the cylinder. Now atmospheric pressure provides the force against the underside of the piston and draws it up towards TDC. Once the pressures have equalised and then slightly increased within the cylinder, an exhaust valve opens to purge the remaining spent air. Thus the cycle repeats over and over until the fuel supply is turned off. Because these engines rely on atmospheric pressure as the power source they weren’t very powerful, as the force is directly related to the piston cross sectional area. However they found uses for driving sewing machines, Dentist drills etc and required little to no experience with things mechanical to operate.

The engine in question, rumour has it that Otto used it to pioneer his now well known 4 stroke cycle. The engine was kept at the Deutz museum for a while before it vanished. Recently a group member sent me some photos and a video of a full scale replica that he was building, needless to say I fell in love with the design and a model was planned. I decided that the flywheel from my Robinson hot air engine would be just right for this project and was used to provide the datum for all the other dimensions needed for pattern making.

That’s all from me for now. I am trying to finish the model in time for the Neunen show next month where, I hope, it will join it’s full scale replica’s debut.

Special thanks to Wayne Grenning from who’s research work I have borrowed.

The bottom picture clearly shows the engine in question in the bottom left hand corner.

[Alyn Foundry]

Otto used a couple of interesting features in his design.

The gaseous fuel was only supplied on demand by the use of a valve that was incorporated into the port slide. Just a small pilot flame remained lit.

The Scotch yoke gave a rapid down/induction stroke followed by a much slower return stroke.

[Alyn Foundry]

I approached Jason several weeks ago with the idea of a model, his help previously providing the last remaining patterns for the Brayton Ready-Motor project was invaluable. The CNC process ensures high accuracy and near perfect results.

We used the Robinson hot air engine flywheel as a scale datum and Jason then used the picture to find all the rest of the measurements using his program. I had callipers, rule and calculator to make my patterns…. 

I will now had over the reins to Jason with an overwhelming debt of gratitude for his help in getting yet another of the great pioneers in the world of IC into model form.

  Graham.

[Admiral_dk]

Getting the  and  ready and thank you for the introduction on this historic engine 

Per

[Jo]

I will now had over the reins to Jason with an overwhelming debt of gratitude for his help in getting yet another of the great pioneers in the world of IC into model form.

We will have to wait for him to first finish the engine and gets his running before he posts the build 

Jo

[Jasonb]

Oh well in the mean time for those that are interested I'll have to fill in with some background and the design.

It all started with an e-mail from Graham enclosing a copy of one of the patent drawings and suggesting that it would make a good candidate for my 24mm bore series of engines. I went back to him enclosing more images including the second one he shows in his first post which is of the patent model that was posted by Nick Roland (RMC Engines) on Smokstak forum. This model is held by the Smithsonian and this is a shot from the other side of what remains.



 Knowing his liking for using food tins as parts of his models I did suggest that a large Corned beef or Spam tin would make an ideal engine base He seemed keener that I make a pattern for a cast iron one. So discussing carried on and mention was made of using the existing Robinson flywheel which at 7" dia (178mm) set our scale and was soon followed by a printed drawing of Grahams with some sizes calculated from proportioning from the now known flywheel diameter.



I've moved on from the days of drawing a grid over and image and determining dimensions from that. Instead I used Alibre's "trace" function to import the image and then enlarge it to a point where the flywheel measure d178mm so that any further drawing on it would be actual size. had the image been a straight on side view I could have drawn directly over the image but a sit was at an angle I just drew a series of lines from point to point and used what they measured to start producing a drawing for the pattern.



The overall external shape was not too hard to draw out being little more than a taper sided box with a flange at the bottom and a few rounded corners and internal fillets.



Had the base just been a 5 sided box without the cutouts then it could have simply been made hollow as a "self coding" pattern but the need to form the various windows meant that a core and therefor a corebox to mould it in was needed. I started off by drawing up the core, well half the core actually as the other half is a simple mirror image that is only a couple of clicks away. The protruding parts of the core around the sides will touch the edge of the void produced in the sand by the pattern but as it only has them on three sides the top ones were made to protrude more and they locate in the core pockets produced by the core prints on the pattern which are the black coloured bits in the above photo.



we decided on an over scale wall thickness to the base of 6mm to ensure that the iron flowed easily and that bit of extra thickness should help to keep the chill away. This will only really show around the sides as the top and underside of the bottom flange will have 3mm machined off them and 2nn off the bearing supports.

A couple of images of the core being tried out for size within the pattern which was set to be semi transparent to help seeing if things were correct.







Once satisfied that all was as it should be it was a fairly simple job to form the negative of the core into a block using a Boolene Subtract and then just mirroring that to get the other half.



Well that's enough for now I've an engine to finish Next time I'll write a bit about the CAM and the machining.

[Alyn Foundry]

Many thanks for the introduction of the technical drawing side Jason. I personally find this aspect difficult to get my head around. I’d still be sat in front of the PC now, instead we’re nearly 2/3rds towards completion.

I should have mentioned that the original engine was water cooled, those with Eagle eyes might have spotted the spigots on the side of the cylinder? However, our rendition isn’t….

When I was developing the CHUK engine for Chester UK Ltd, I met up with Bob Sier at the Midlands model engineering exhibition. Bob had been one of the first customers and had got his engine running and on display. Whilst chatting he mentioned the fact that he’d bored his cylinder out to the maximum the casting would allow. He explained that the greater the piston cross sectional area was, the greater the power would be.

Based upon that knowledge I decided on an air cooled cylinder with the maximum bore that the scale could allow. We are using a bore diameter of 44 mm. Being just a model, display runs would be short in duration so wouldn’t need the extra complication of cooling tanks etc. From this value, under “ ideal “ conditions we could expect a maximum pressure of 34.65 PSI acting on the underside of the piston. The engine should at least move !

At this moment the cylinder pattern isn’t fitted with water cooling spigots but they can be added at a later date, as could an extra pattern to make a casting to create a water jacket.

The photo shows the base fitted with crankshaft and Scotch yoke assembly.

  Graham.

[Jasonb]

It would also be possible to make a simple bobbin shaped liner to give a water space that will seal at either end should it be required. That might even bring it backdown to 24mm bore

[Jasonb]

With all the CAD work done it was time to fire up F360 to do the CAM and generate the tool paths to machine the patterns. The actual CAM would have been quite simple just an adaptive path to remove most of the waste, a finishing pass on the mainly near vertical surfaces and then a couple of small horizontal paths to clean up the top of the core prints and the top of the bearing supports.

However as the pattern is close to 105mm tall I would have needed at least that amount of tool sticking out beyond the collet chuck if I was going to avoid crashing that into the work, F360 certainly turned the screen red with masses of collision warnings even when using an extended shank cutter with 30mm projection. The answer was to split the piece into several layers which could correspond to the layers of wood I would be using to build up the pattern from.

You can see down the left hand side I have a number of adaptive and then ramp paths which are numbered in the order they will be cut.



The actual order they are listed is to allow me to run the simulation on a "solid" block starting from the top and fooling F360 by having a very long cutting tool so it doe snot show any collisions. This shows it about to do the last ramp cut where the blue waste will be removed to leave the green finished surface below.



So time to put it into practice. As I don't have quick change tooling I opted to do all the adaptive cuts first with a 6mm 3-flute cutter just screwing each layer onto the one below. Then I took them all apart, changed to a 4-flute long shank 4mm ball nose cutter and worked my way up again, this time screwing and gluing the layers together.

First layer roughed out


Second layer screwed on and adaptive cut just started


Second layer complete


And the third showing the amount of chips each layer produced


All 5 layers roughed out


With them all taken apart and the tool changed it was time to start the finishing cuts


And all done

[Jasonb]

The core box was not so deep and I was able to get away with using extended shank cutters without having to resort to multiple layers. To reduce the amount of cutting I built up the block from one full size base layer and then just added three strips at the ends and top. Similar roughing and finishing paths were again used with the same two tools. The last path was the drilling of two holes for location pegs to keep the two halves of the box lined up, I used an HSS brad point drill for this as they produce a nice clean entry hole



With the second half done which was basically a mirror image of the first a couple of 6mm steel dowels were put in the peg holes and I was pleased that the two halves pushed together nicely.



It was just after this that I got an e-mail from Graham suggesting that some writing should be added to the inside of the base so that was added to the CAD model and then the CAM done for that. As it was 30mm deep into the corebox my engraving cutters were not going to be long enough so I opted to use a 6mm spotting drill which had enough length to still be able to get a good grip of and a reasonably pointed end. The halves were clocked in again on the mill and the writing engraved - right way round on the core box = wrong way round on the sand core which should hopefully equal right way round on the casting.



All that remained was a very light sanding with 180g paper and a coat of paint, we have just been using grey rattle can primer which seems to work OK.

[Johnmcc69]

 
  very nice work!

 John

[Zephyrin]

The overall external shape was not too hard to draw out being little more than a taper sided box with a flange at the bottom and a few rounded corners and internal fillets.

this little sentence contains a huge amount of skills...

draft angle, internal filets, rounded corners...
it looks so simple that I wanted to try to make a 3D model for the casting of my next engine, and no it wasn't easy...
I'll finally cut the engine in an aluminum block, as usual, if I want to have a finished engine one day...

[Jasonb]

Compared to a typical crankcase kike those of the Midget or Lightweight that I built it is a much simpler part.

If you take a look down the left of the page to the blue horizontal break bar there are just 4 sketches which are extruded these are just rectangles and a circle, Alibre lets me include a draft angle to the extrusion.

There is then one additional draft angle added to the sides of the bearing supports.

The remaining items are just internal fillets which are fairly straightforward to add though a bit of care can be needed to get them in the right order. I probably could have done away with a couple of those if I had included them in the sketches but it's often easier to edit if they are done separately

[Alyn Foundry]

The mechanicals have been completed for several days now. Getting the little blighter to run is proving rather difficult.

  Graham.

[Jasonb]

I was wondering if you could try it without the exhaust valve but just use a bit of shim stock held by one of the head fixings to see if that allows it to breath a bit easier, much like the exhaust on Nattie.

Would also be interesting to hold it on it's side in the vice and see if it runs as this would eliminate the weight of the yoke having to be lifted on the power stroke.

[Alyn Foundry]

As with any new model there are bound to be teething problems, particularly when you don’t have anything to go on. Although a vacuum engine this design doesn’t have the very large cam profile that you’d naturally expect, it’s quite the opposite in fact. Luckily I started out with a bossed disc and removed what I thought would be enough for a run. I’m now down to something that resembles the standard cam profile we see on IC engines.

I’m quietly “ dialling in “ towards the sweet spot, we had a sustained run of just under 30 seconds yesterday evening. I discovered that the flame port lever was binding against the casting putting extra load upon the crankshaft. The flame position is also very critical too. Another area for improvement might be the addition of needle roller bearings instead of the plain Brasses to help reduce the friction.

Today is my 66th birthday, officially retired. The best present would be for Little Otto to keep on running!!

  Graham.

[Jo]

Happy Birthday Graham, hope you have a good one 

Jo

[Admiral_dk]

Happy Birthday Graham - may you have long sustained one 

Congratulations on retirement     

Per

[Jasonb]

Enjoy your birthday and don't eat all the cake. Hope the little sucker will make your day complete.

[Kim]

Happy Birthday, Graham!

Enjoy your retirement! It's a wonderful thing! 

Kim

[Dave Otto]

Happy Birthday!!

Dave

[Alyn Foundry]

Many thanks for the birthday wishes.   

Sadly Little Otto didn’t perform so I spent a few hours playing with Mr Robinson in the workshop instead.

Due to the marginal power developed by this engine a smaller crankshaft will be made to allow the use of ball races to reduce the friction at the main bearings.

  Graham.

[Twizseven]

Happy Birthday Graham.  Hope you had a good day and your engine rewarded you with a longer run.

Colin

[Jasonb]

While little Otto is getting closer to a sustained run from the videos I have seen his bug brother replica has made it's first appearance in daylight at the Nuenen Rally, here it is captured on video so you can see what we are trying to model

<a href="https://www.youtube.com/watch?v=NG_sbib7RUM" target="_blank">http://www.youtube.com/watch?v=NG_sbib7RUM</a>

The same Youtuber has quite a few other videos of the Rally.

[Zephyrin]

The video shows that the drag in the fork with the sliding shoe may cancel the advantage of the quick return mechanism...
flame gulper engine are never simple, and sometimes deceptive, even if they run at the end !
happy birthday, young man...

[Jasonb]

So as not to keep the impatient kids waiting too long I thought I might post a bit about building mine. There will be some differences to Grahams as we both have slightly different ideas, ways of doing things and also interpret the patent drawings differently. he was also in a rush to get the little Otto off to Holland to meet his big relative but that will have to wait until next year now.

I started with the base as not only was it the largest bit but also from my pattern so I wanted to see how it came out. After a good fettling with Dremel, linisher and 115mm angle grinder I mounted it upside down on the mill table and took the flange down to finished thickness and also took a very light cut off the four edges of the flange which gave me good datum edges that were all at 90deg to each other.



I could then clamp this surface to the mill table and bring the base down to finished height. We had decided to make the pattern so it produced a 6mm wall thickness to allow the iron to flow and reduce the risk of chill so there was about 3mm to come off.



As the design was being tweaked a bit as I went along some of the operations may seem a bit out of sequence or things will be remounted to do something that could have been done at the same time if just working from a set of proven drawings but that is the way of us engine designers.

So it was again mounted upside down to machine a vertical area on the tapering inside face so that the yoke pivot would have  a flat surface to sit on. I got a bit carried away and also drilled the mounting holes in the corners, it was only looking again at the patent that I saw they should be part way along the sides so out with the JBWeld.



Up the right way again and the hole below the cylinder was opened up with the Soba boring head followed by squaring up the other opening as some draft angle had had to be included on the core so it could be removed from the core box.



With the bottom of the casting now clamped to an angle plate the height of the two bearing supports could be machined down to 49mm above the bottom face.



The stud hole to retain the bearing caps could then be drilled and tapped which needed a long reach ctr drill and long series drill bit followed by extending the tap. I also did the cylinder mounting holes at the same setting to make sure the crank to cylinder distance was right and that the cylinder would sit centrally between the two bearings



To be continued.

[Jasonb]

After that brief interlude where the bearing caps were cleaned up and drilled so that they could be screwed to the bearing supports and machining continued.

I had intended to skim the insides of the bearing supports to remove a little of the draft angle and give a flat surface for drilling but had to take a bit more off as the cap castings could probably have been 1mm or so wider, the CAD file has already been altered should a revised pattern need to be cut. Here you can see one side cut vertical until the inside edge of the cap just cleaned up.



I clamped a 1-2-3 block against the outside of the bearing support to reduce any risk of the cutting forces deflecting the casting.



I then used a 4-flute ctr cutting milling cutter to form a flat on the outside before drilling 6mm pilot on the top bearing, then 9.8mm through both and finally went through with a 10mm machine reamer. A ground 10mm HSS tool blank ran nicely in the holes so nothing had wandered on the lower hole.



A couple of 8mm bore flanged bearings were soon turned up from some bronze bar and all fitted together as it should.



The last job on the base was to drill the four holes that will be used to mount the pivot for the scotch yoke.



There is not a casting for the pivot so I cut it on the end of some 25mm square bar, first doing the profile on the CNC and then cutting the slot down the middle and tapping the holes on the manual mill. It was given a running over with a grinding point in the Dremel to give a bit of texture so it should look like a casting once painted.

[Jasonb]

After a quick clean up the cylinder was set so that the main outside diameter of the cylinder ran true at each end. Taking very light cuts as the part projects about 100mm from the chuck the end and outer edge of the flange were just cleaned up so that I could hold onto a decent surface for boring.



Then holding by the cleaned up surface it was again set to run true and a clean up cut taken off the other flanged OD. This then gave me a surface to run the fixed steady against, well just!. The flange was then faced back to 3.5mm thickness before boring the cylinder.



I then made up a plug so the tailstock could provide support while holding in soft jaws so the back face of the flanges could be cleaned up. The casting is a bit tight on width for a nut to bear on so I used an insert with a 0.8mm radius to leave a fillet that was quite a bit less than the cast one to maximise the width of the flange. Both ends were treated the same.



Drilling and tapping the two different bolt hole patterns was quite straightforward with the cylinder clamped to the mill table by the flange it was just a case of locating ctr and drilling the required pattern, simple 4 hole PCD on the bottom equally spaced but the top has an irregular pattern as the three hole son the left are on one PCD but the other two are co-ordinate drilled as they will have long studs that also hold the exhaust block in place.



before I could tackle the bos sthat the rocker arm pivot fixes two I needed the pivot. Graham made a pattern and had iron castings made for these but I felt form was more important than function, if the engine fails to run at least it should look the part!.

So a bit of 25 x 25 x 3 steel angle was thinned down to 2.5mm thickness, trimme dto overall size and a slot and hole added. A bit of 8mm rod also had a slot cut and was pilot drilled 2.8 ready for later reaming out to 3mm and lastly a bit of 2.5mm sheet wa scut to width.



Add in some heat and silver solder then pickle for 1/2hr or so and the embryo bracket is ready for final machining.



After some further milling, drilling, filing and a going over with the Dremel the pivot "casting" was done and has a bit more form than the functional cast iron one.



The pad on the cylinder could then be milled flat and drilled and tapped M2.5 making sure not to go too deep and into the bore.



I could then screw the pivot into place and scribe around it so that the edges of the pad could be tidied up with files and Dremel which completed all the work to the cylinder

[Alyn Foundry]

Great to see some “ decent “ engineering going on.

I did try to put some sort of form into my bracket, sadly the only photo I had for the engine the support looks pretty basic.

I’m hoping that you fare better as the construction goes on, my engine seems to be quite tight in the crankshaft department. The flanged  “ Oilite “ bushes used don’t remove that much friction….

  Graham.

[Jasonb]

I went for a similar bracket to Tom's as it looked OK, don't know if he had other refs or just went with wat he wanted. Levers are done as are the separate shutter gibs.

Currently I'm forging ahead with my crankshaft in every sense of the word

[Alyn Foundry]

It seems we were posting together Jason, I look forward to seeing the latest from the Blacksmiths department….
 

I decided to try a needle roller bearing in place of the flanged Oilite bush the friction reduction is tremendous. From this….

<a href="https://www.youtube.com/watch?v=tTp7JS2FoXw" target="_blank">http://www.youtube.com/watch?v=tTp7JS2FoXw</a>

To this….

<a href="https://www.youtube.com/watch?v=JKr8j_PdxOQ" target="_blank">http://www.youtube.com/watch?v=JKr8j_PdxOQ</a>

The new bearing does nothing for the high precision machined flywheel so a new, replacement crankshaft will have to be made to accommodate some “ proper “ ball races.

  Graham.

[Zephyrin]

great improvements, your engine is now a runner...
I wonder why do you are using such a sooty flame and not a hotter one ?

[Alyn Foundry]

great improvements, your engine is now a runner...
I wonder why do you are using such a sooty flame and not a hotter one ?

Hi Zephyrin.

Yes we’re definitely getting there. I have always found that the “ dirty “ flame seems to work for this type of engine really well, particularly on just finished engines.

Otto’s patent shows an automated flame delivery system that should mix the gas and air more effectively and, hopefully make a much cleaner burn.

  Graham.

[Jasonb]

A cast iron disc is supplied for the cylinder head or end cover - not sure what to class it as. No chucking piece on this but not a problem, after cleaning off a few bits of flash with the linisher it was held in the soft jaws, faced, OD turned and then a spigot formed to locate into the cylinder bore. After that it was just flipped over and the other side faced off but left over thickness for now.



I took a few clean up cuts off the inlet and exhaust blocks to get an idea of their final size and juggled them about on the engine to see what was the optimum position.





Once happy with the positions the some measurements were taken and then added to the CAD model. This was then used to complete the machining. From the underside there is a slot that lines up with the cast in slot of the inlet block that has had a chamfer milled on the inner edge to aid flame flow. The large circular hole is the exhaust, I wanted to get this as large as possible so have overlapped the flange but there is still plenty of metal around it to get a good seal. There are four 3mm holes to mount the inlet Block two counterbored and two others countersunk as the metal above the flange would be too thin to counterbore. Finally five 3.5mm holes for the studs to hold the part to the cylinder, the the right two will also hold the exhaust block.





After drilling the two stud holes in the exhaust block these were used to set it level in the mill vice so that the exhuast pipe boss could be drilled and tapped, as I'm making my engine to metric sizes I opted for M10 x 1.



This thread was then used to hold the casting in the lathe so the boss could be turned round and then blended into the main shape by hand.



My mill has no problem doing circular recesses so I cut a 20mm dia x 11mm deep one first then a 10mm x 1mm deep one in the bottom of that. The 20mm dia will locate the exhaust valve disc and the smaller one the spring. I then needed a way to allow the exhaust gasses past the disc so milled four pockets just leaving a small sections of the 20mm dia remaining.



Quick check with a  piece of 20mm bar and it just fits nicely

[Alyn Foundry]

As mentioned in other places, I really liked the way you provided the exhaust valve guide Jason.   

We definitely have different ways and ideas of how to make this engine. I opted for rather small, for me, stainless Steel 2 mm studding to hold down the valve block to the cylinder head. And also used 2 mm Brass grub screws as a guide for the exhaust valve disc.

I used a tee slot cutter to create the slide ways and more 2 mm Brass grub screws to provide adjustment. The photo says it all….

  Graham.

[Alyn Foundry]

I must add that my engine was rather hurriedly done with a view to it joining its big brother over in Holland earlier this month. I went for as many “ off the shelf “ components that I could to save on machining and fitting time. I used 4 mm Rose joints for the conrod and Oilite bushes for the mains. This has now proved to be a problem insofar as the conrod is really noisy and the bushes are really heavy on friction.

<a href="https://www.youtube.com/watch?v=E_c4y1kNEsM" target="_blank">http://www.youtube.com/watch?v=E_c4y1kNEsM</a>

  Graham.

[Alyn Foundry]

Today it’s hard to imagine that these engines were in common use driving small loads and were built in reasonable quantities. Here in the UK a patent was granted to a Mr R M Lowne in 1892 for one such engine. He manufactured is own versions, a picture of a twin is shown below. Another firm, Hardy and Padmore, also made a vertical version under license.

What’s interesting to note is that they both used Brass pistons. So armed with this knowledge I decided to try out a different approach with Little Otto. I have had quite a bit of experience with metal spinning over the years making spares for Tilley lamps. There’s virtually no waste involved with the production and the finished product requires very little work to complete. A Steel “ chuck “ was turned up with the ubiquitous 1” Whitworth thread made to fit the spindle nose of the spinning lathe. Discs of 2 mm thickness “ cartridge Brass “ were then placed upon the chuck and spun down to form a cup. The first attempt saw a taper of over 2 mm from crown to skirt, absolutely useless…. The chuck was gently tapered down from the crown to the skirt end, the cups were then re annealed and the metal sprang back to under the permitted maximum diameter.

The Brass piston spinning was then placed upon a suitable mandrel and the OD machined parallel to suit the cylinder bore. A single stainless Steel counter sunk Allen cap screw was used to fix the piston to the small end yoke.

Photo 1. The chuck.
Photo 2. Lowne twin cylinder.
Photo 3. Hardy Padmore engine.

[Jasonb]

interesting little engines.

As Grahams piston is now in the engine here is mine as it came off the spinning lathe, just a few thou of taper due to spring back, it's a fine line between getting a parallel side and not being able to remove the spinning from the former, no doubt mass produced items have the time to do a few more test ones to reduce the taper to a minimum.

Was it 2mm sheet or 1.5 as that is about what the flat part of mine measures, bit thicker around the edge as you would expect.

[Craig DeShong]

Jason and Graham, I’m enjoying watching these builds and the two different approaches you are taking in this fascinating engine.

[Jasonb]

Must be time fore a bit more progress.

During one of our many e-mails Graham had mentioned a forged crankshaft although in the end he did not use one going for a two piece crankshaft in the end to aid assembly with the scotch yoke. However I decided to give it a go and Forged mine though not in the sense Graham was originally thinking of.

Starting with some bar that had been machined down to 10mm x 12mm section some holes were drilled and reamed for 8mm PGMS shafts.



Then a bit of turning between the two holes taking the rectangle down to 10mm dia with a 2mm nose diameter grooving tool so a 1mm radius was left at the ends.



Some rounding over of the ends on the rotary table was next no pictures of that as Jo may not approve Before silver soldering it together as you would a normal built up crankshaft.

Some more rounding on the Rotary table saw the basic "forged" parts of the crankshaft start to take shape, I'll sneak in a picture this time.



The remaining shaping was done by filing which then just left milling a keyway to complete the crankshaft



A quick spray of primer is always a good way to see if there are any bits that need a bit more attention with the file, then a final coat.



Graham had some pistons spun from soft brass sheet as shown here



There was a slight taper to the sides due to spring back of the brass despite the former having a negative taper but it's a fine line between parallel sides and not being able to get the spinning off the former. To true up the sides I turned a short spigot on the end of a stub of aluminium to a firm fit inside the piston and added support from the tailstock via a pressure pad so the OD could be skimmed down to fit into the cylinder.





The cylinder was then honed to remove a very slight taper until the piston slid freely in and out.

I also did some more work on the inlet side of things with a shutter made from 3/32" gauge plate and two "L" shaped gibs to guide it. The two levers that convert the movement of the cam to movement of the shutter via the pivot were also made from 1.5mm sheet with bosses soldered on.





With enough bits now made it was time to have a listen to Otto's first words. Sounds like it should work even if it's just for duck hunting!

<a href="https://www.youtube.com/watch?v=DePiCL5zCus" target="_blank">http://www.youtube.com/watch?v=DePiCL5zCus</a>

[Roger B]

That's some interesting takes      I like the faux forged  crankshaft   

[Alyn Foundry]

Blimey, this thread got buried quickly overnight. 

Some great workmanship again Jason, puts mine to shame. I don’t have much to report as the family was hit by the dreaded Rona a couple weeks ago. For me the fatigue was so bad that I’ve just been sleeping for the most part.

What has become very apparent is that friction in the main bearings will need to be as low as possible. As mentioned, my crankshaft was made from 8 mm Silver Steel with 10 mm webs. I made it so the crankpin was a sliding fit into the other web. This allowed me to minimise the machine work on the Scotch yoke ( a simple 8 mm slot milled from end to end ) however the addition of the second half of the crankshaft will stall the engine.

I don’t have the same, excellent, piston to bore fit as you do because I didn’t have the two components available at the time of boring the cylinder. This meant that when the piston returned from the Spinners after the chuck modifications it was already fitting the cylinder by around half the length. After truing just a third of the skirt fits with any seal. This might have a bearing on why mine isn’t very powerful? As your build progresses we will ultimately find out!

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


  Graham.

[Admiral_dk]

I like your last part Jason - great fit (and Sound) 

Very impressed with how well you got that Flame dialed in Graham  Both the very blue flame during induction and the Pilot Light in between.

Love to see both builds here 

Per

[Alyn Foundry]

Thanks for the interest Per. 

It has taken quite a lot of time to get to this point. Much experimentation with hole sizes for the gas were tried. Initially two 0.5 mm were drilled through the 4 mm thickness gauge plate and the casting had a couple of 2 mm section Viton O rings to help seal the joint. It was hoped that the gas would hit the roof of the, now nicknamed, “ Snail house “ and travel, after being ignited into the flame port. Needless to say it didn’t work at all to plan! In the end 2 pieces of 1/8” OD Copper tube were bent, cut and Silver soldered into the shutter.

I discovered that the little O rings were causing severe drag on the shutter and once removed it began to run. Having much larger holes for the gas enabled me to run at a greatly reduced pressure ensuring little to no leakage between the two, highly polished surfaces.

What has now become apparent is that as the slide moves to open the fuel to the flame port the pilot flame virtually extinguishes. You need a pilot for the pilot.    I have got some little Brass taps on order so that the branch between the ignition and fuel supply can be separated so the pressure drop won’t affect the pilot light.

  Graham

[Admiral_dk]

You need a pilot for the pilot. 

     

I can't say that it surprises me much about the plans - Mice and Men - springs to Mind 

But like my suprice on how well you got it dialed in (for such a small scale) - I'm also glad to see that you succeded - this requires some Patience and Persistance

Per

[Jasonb]

If you look back at the first few posts in this thread you will see that little Otto has a form of scotch yoke that is pivoted at one end and connects to the conrod big end at the other. I had sent Graham a basic sketch of this with the critical sizes from which he made a pattern and had some cast in brass with the intention to have the crank run against the brass slot. Having subsequently seem images of Tom's larger size replica I decided to go down that route which has split bearings for the crankshaft and to get them into place the bottom of the Yoke is a separate part.

I did a few alterations to my initial model while bearing in mind how I might machine the part and also ways to hold it and came up with this.



Wary that cutting a big notch out of the lower edge could make the steel go banana shaped I cut off a short length of 10mm x 100mm black hot rolled steel which should have less internal stresses than bright bar. After milling down to the required 8mm thick by taking 0.5mm cuts off alternate faces to keep the cuts balanced  I drilled and reamed for the two 4mm holes and also stitch drilled out most of the waste material from the slot.



A couple of quick hacksaw cuts and the remaining waste dropped out so that the slot could be milled to the final 50mm x 10mm size and a pair of holes tapped M3 for the bottom plate retaining bolts.



Another piece of steel milled to 3mm x 8mm section with a couple of clearance holes completed the work on the manual machines.



The CNC is the best tool for the job on a part like this where there are curved features running into straight and angled ones so a session on Fusion 360 soon gave me a USB stick with all the tool paths needed, 5 per side which were:

1. Adaptive cut to remove most of the waste using a 4mm dia 4-flute R1 cutter at 5000rpm and 500mm/min feed
2. Ramp cut to finish the vertical and curved surfaces using a 3mm dia 4-flute carbide ball nose cutter at the same speeds and feeds. This was also used for the remaining cuts
3. Horizontal cut to finish the face of the webs and the "D" shaped big end boss
4. Scallop cut to refine the near horizontal parts of the three round bosses
5. Pencil cut which refined the internal fillets particularly where the three bosses meet the main body.

With the KX3 fired up the first thing to do was drill and ream for two location pegs in a bit of scrap aluminium which would locate in the two hole sin the yoke. I also tapped a couple of M3 holes to take screws to clamp down a top hat section clamping block.



It was then just a case of clicking "GO" and then getting on with something else, just popping back to change the tool and start the next tool path. Also just had to turn the yoke over half way through so the opposite side could be machined.



quite pleased with how it turned out. There is one small flaw in the steel that you may just ne able to see about mid way along the top flange between the oiler boss and big end boss. I could hear it as the tool passed but not really see what was causing the change in tone until the part was out of the machine as it was towards the rear when being cut.







Finally a couple of close ups of the tool marks left by the ball nose cutter as it stepped over 0.2mm between each pass of the horizontal path, they are more visual that physical as I can only just about feel them with a finger nail but as this was probably a casting or possibly a forging it will be fine after final fettling.

[Jo]

It strikes me that needing CNC to make some of the parts for this engine is not going to encourage people to buy casting sets  from Graham.

Jo

[Jasonb]

Strikes me you need to read the thread again. You missed where I mentioned that Graham supplies a casting, this could be used as is which is what he has done on his engine and it runs, His whole engine has been made on manual machine so it DOES NOT need CNC to be make a running engine.

His casting could easily be modified to be a two part one like mine as there is plenty of material in the casting.

Could also be done with manual machining and some silver soldered on bosses.

Just up to the individual builder as to what route they choose to follow be it a casting as Graham used or cut from solid on the machines I have available. Is it any different to you making new columns for the A&M rather than using the castings?

If he does decide to make this one available to others then its not too hard to mill a slot and ream two holes in this, even you could probably do it without a muck up though there are no drawings to blame

[Alyn Foundry]

It strikes me that needing CNC to make some of the parts for this engine is not going to encourage people to buy casting sets  from Graham.

Jo

Fear not Jo.
As Jason beat me to it with a reply. I’m still very weary and getting as much sleep as I can. Yes there’s a casting available for those of us who  them.

Jason has followed very closely the  ( full scale? ) engine replica built by a Dutch gentleman called Tom. We’ve all based the parts around an original photo and a couple of patent drawings. Apparently the one and only Deutz built engine was actually scrapped by the museum in the 1930’s. 

As I’ve stated earlier in the thread I wanted to get mine running for the prestigious Neunnen engine rally to join with Tom’s engine. This meant doing things as simply and easily as I could. I really do feel that when Jason gets to the finish line his model will be worthy of “ museum quality “ status.

  Graham.

[Jo]

Thank goodness for that Graham, someone does love showing off his CNC machine at every possible opportunity.

Jo

[Jasonb]

Is it CNC in General you have a problem with Jo or just my machine?

I've shown one part in this thread using the CNC and you make these comments, Why not post comments in the likes of Vixens thread where he shows far more use of CNC or any of the other members that use them?

I just use what I have available and choose what best suits the job, much like you choose to use say your Delapina Hone as you are lucky enough to have one where most of us make do with a brake cylinder hone. I choose to document all the parts I make for a model so don't want to leave out the ones made by CNC as some people are interested in it even if you are not

[Jo]

No problem, just observing that since you were given the machine you endeavour to use it at every opportunity, some would say you are getting your monies worth out of it.

I don't think Mike has any manual milling machines  he has a well worn in lathe that he paid a fortune for 

Jo

[Jasonb]

Certainly do seem to be getting some use out of it. Its interesting that John Stevenson offered me one (early KX1) a few years earlier and I said it was not really for me, was even in two minds about this one but glad I went for it though still like to use the manual machines as well.

This whole model would probably never have got off the ground without my CNC patterns as I could not convince graham that the base would be quite easy to fabricate when he first contacted me about the engine but he wanted a cast one.

For anyone put off thinking they may need CNC for this engine should castings become available this is Graham's casting side by side with my CNC machined one. As I said there is plenty of metal there to do whatever you wish. One of the other reasons I went down this route is that the power stroke on little Otto is upwards so any reduction in weight he has to lift will be helpful so apart from being a two part yoke mine has much thinner webs and slightly reduced diameters at the rounded ends. easy enough to mill a bit off the casting and the thicker web would be thick enough to tap if you wanted to do the two part option





Original sketch sent to Graham to make the pattern from and one of my version, as you can see all critical sizes are the same.

[Alyn Foundry]

We have very different attitudes where fabrication is concerned 

However, Jason’s program and CNC machine made an absolutely perfect job of the base pattern and associated core box for it. I can now see why, for a one-off, that Jason finds this route the best. 

The Scotch yoke pattern was made well over the top to allow for most eventualities. To my eye, the picture shows the big end to be a simple ring within the forked end of the yoke. Both Tom and Jason saw it differently, the conrod end being forked instead. The casting allows for either option.

I also made the pattern parallel for ease of machining, the casting can then be finished to the correct shape.

  Graham.

[Alyn Foundry]

Well my model has reached its conclusion, and yes, I’ve even painted it.   Not very well though…. 

I have got some video to sort out but in the meantime here’s a couple of photos.

I’m eagerly awaiting Jason’s rendition as he has followed much more closely to the large replica that has recently been shown in the Netherlands.

  Graham.

[Alyn Foundry]

The video.

<a href="https://www.youtube.com/watch?v=1zxH_Ajp9kA" target="_blank">http://www.youtube.com/watch?v=1zxH_Ajp9kA</a>

  Graham.

[Admiral_dk]

Congratulations - You have a fine Runner     

We know that the Camera can show many minor details that the Eye don't notice/can't see - and the Microphone can do likewise in most Video Cameras (+Mobile Phones) ....
So I have a question - the majority off the Sound - is that from the 'Cam / Follower Interface' or something else ?
I do NOT mean this a critique - but curiousity !!!

Per

[Alyn Foundry]

Well, at least somebody’s watching Per.

The high pitched ringing that I detected after a preview of the video is coming from the Brass “ snail house “ loosely mounted on the shutter plate. I discovered that there wasn’t enough air getting to the two inlet tubes so it’s resting on top of a packing washer currently.

The major knocking was coming from the conrod. My engine has two, so called, precision Rose joints fitted at either end. These were quite expensive but still over tolerance to the 4 mm ground stock used for both little and big end pins.

I made the video yesterday evening, published it and then went off to my care duties. Upon inspection this morning I discovered that the big end pin had virtually ridden its way out of the Scotch yoke pivot. Thus being even more loose than usual.

I’m eagerly waiting to see and hear Jason’s engine running. Having spent a lot more time and very careful engineering on his model I’m guessing that the top and bottom transition into the Scotch yoke will be much quieter than mine.

   Graham.

[Jasonb]

I'm watching too even though I have seen it all previously on FB

I think the design of the pivoted yoke may well accentuate any small clearances that accumalate. With the crank closest to the pivot and slight play between the pin and yoke will be magnified several times at the conrod connection.

[Roger B]

Looks good to me    As Per says it makes some intersting noises 

[Jasonb]

It's gone a bit quiet at the moment. I was eager to give it a try just as a basic flame licker and forgot I did not have the Yoke bolts tightened right up. The yoke came loose and got badly bent and broke when I tried to straighten it. Waiting to have a new one made but I'm distracted by other projects. as well as some pattern making







J

[Alyn Foundry]

Hi Jason.
Several weeks ago I managed to get my fore finger jammed between a flywheel spoke and the main bearing pedestal, needless to say it made quite a mess. Although small the flywheel stores a considerable amount of energy and I can understand why it broke the Scotch yoke.

The latest upgrade of the patterns look superb. I marvel at the accuracy that’s been achieved. In the area of say a flywheel for instance. The CNC makes them perfect. I remember it taking several weeks to make the curved spoke flywheel for the Akryod. I used a piece of glass to align each pair of handed spokes. In fact the whole pattern ended up being built on the glass using filler and whatnot before being used in the moulding box to create each half in Aluminium.

Having recently spoken to the foundry about some thin section castings being chilled they’re going to add a little extra Copper to the melt for the next batch.

Many thanks for the compliments Roger, greatly appreciated. As the engine gets more minutes of running under its belt it gets better and better.

   Graham.

[Jasonb]

I know the feeling I got my thumb caught in Jo's R&B engine, can't remember if she has the single 12" flywheel or pair or 9" but they are big. New yoke with a bit of added material is drawn up and ready to cut.

Yes that split one for the rocker bracket would not be ideal if hard. I suppose this is why a lot of the kit makers go for gun metal on the smaller parts as it's unlikely to have hard spots, just not a nice to work otherwise.

[Jo]

My R&B has a pair of 12" flywheels (for maximum thumb effect  )

Jo

[Alyn Foundry]

My R&B has a pair of 12" flywheels (for maximum thumb effect  )

Jo

I can beat that record by 2 feet Jo!

I got my thumb caught between the 3’ flywheel of my Lister P type and the vertical Steel support for the cooling tank. Needless to say that I had to continue to turn it until I became unstuck. I now have a left handed nail on my right handed thumb.

The photo was taken in 1981 two years of restoration work nearly completed.

  Graham.

[Admiral_dk]

So it would be fair to say that it is not a new interest for you Graham   

As for the accidents - some can be avoided with a bit of care and others not so much ....
But Not One of Them are Enjoyable 

Take Care and Enjoy our Hobby   

Per

[Chipmaster]

Like the swept back exhaust pipe. 

Andy

[Alyn Foundry]

Hi Guys.

I got involved with the vintage machinery preservation movement at the tender age of 20 Per. In fact the Lister engine in the picture was instrumental in me getting involved in amateur foundry work. The engine was used to lift water from a deep well at the back of Chirk castle. It drove a water cooled Ingersoll Rand air compressor the water being moved by the air lift principal. Being in a remote location the scrapper’s had been “ in “ and removed every piece of Copper and Brass that they could, quite literally, smash off the engine. The rest became history….

Andy, yes the rakish angle of the exhaust pipe was picked up by David Edgington when photographed at the second 1000 engine rally, Longleat in 1981. She ended up on the front page several years later with a caption something like “ after 40 years spent working at the local Drill hall old habits die hard “

The photo, courtesy, Ray Wilkinson is from an article I wrote for SE magazine about casting parts for engines. The Petrol Paraffin changeover arrangement was all homemade.

   Graham

[vtsteam]

Fantastic build thread. Sorry I hadn't been present at the time to see it unfold.