Author Topic: The McOnie Oscillating Engine  (Read 27256 times)

Offline Ramon Wilson

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Re: The McOnie Oscillating Engine
« Reply #15 on: March 22, 2013, 11:02:51 PM »
Hi Guy's - thanks all once again for your kind and thoughtful remarks.

As I said I don't have too many pics to post about this engine and so for the early part this will be from memory and therefore retrospective. Also I did get back onto the Eta engines today :D so they will have to take precedence but I'll try to put a bit up on here when theres not much to say about them. There won't be any further machining work on this though until they are finished.

I obtained these castings untouched from my friend Gordon who, having bought them when it was first released, decided it wasn't for him - I think he got the better deal pound wise - I parted with a set of ST No 9 castings - but I think this is a much nicer engine

I first saw this particular engine when it was featured on the cover of model engineer magazine but that was long before these castings became available. That was a scratch built version by Anthony Walshaw and like Nick G was attracted to it as it was a 'full size' oscillator so when Gordon offered me these it didn't take much to agree
(Nick - are you aware of the four colum table oscillator described several years ago in ME by a Dr Gregory ? I think it's based on one in the Science museum and has similar valve gear to the McOnie - it can all be built without castings - a very nice project).

The drawings did have the odd error (which could easily catch the unwary out) and were somewhat ambiguous in the area of the cylinder pivot bearings so I set out to see if my thinking about how to go about this area would work. I began to notice one or two errors early on and so began to check every thing as I went but so far all has worked out and as you see it's not looking too bad at this stage.

I began by milling the base and main frames and erecting them. One of the bolting holes in the base is misplaced on the drawing by 2mm and the location of the hole for the governor spindle is datumed from the opposite end. Given that this has to align with the governor bracket bolted to the frames this datum was changed to that of the mainframes location. The guy I was speaking to at the weekend told me he took this anomaly at face value and ended up having to fill and redrill his baseplate.

After some consideration over the bearing brackets - the drawing does not make it clear how these are attached to the frames - it was decided to attach them with two 8BA countersunk screws and plenty of JB Weld.  The bolt holes for the frames were opened up and cast iron pads fitted with JBW and filleted to give a more casting like appearance. A couple of long shank spot-facers  were made to clean these up later...







As you will see JBW was also used to fair in around various points to smooth some areas out.

The bearing caps were made at the same time as the lower bearings then fitted after the lower bearings were screwed and bonded in. After this had cured the L/H side frame was set up to drill and ream the 3mm holes at the requisite angle for the valve rocker guide rods. The 3mm reamers available were no way long enough for this op so the holes were reamed by a home made reamer made by grinding a shallow angle on 3mm silver steel. The caps still have quite a bit of work left on them to shape them, fit oil bosses and bolt pads but at this stage it was possible to set them up on the lathe and line drill and ream them






This method proved successful in getting those bearing holes in line - an important factor for the cylinder to swing freely - next was to ensure that the bearings either side of the cylinder were in the same plane too

Hope that will do for tonight - some more on setting up and machining the cylinder next time.

Regards - Ramon


"I ain't here for the long time but I am here for a good time"
(a very apt phrase - thanks to a well meaning MEM friend)

Online Jo

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Re: The McOnie Oscillating Engine
« Reply #16 on: March 23, 2013, 07:11:45 AM »
Thanks Ramon,

Any more details on the drawing faults will be much appreciated.

Jo
Enjoyment is more important than achievement.

Offline NickG

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The McOnie Oscillating Engine
« Reply #17 on: March 23, 2013, 11:50:46 AM »
Ramon, no I wasn't aware of that engine, I think the only other realistic looking one I'd seen was the crosskills one by Anthony mount? That's a lot simpler though and doesn't interest as much. Will look up the one you mentioned. Thanks.

Offline Jasonb

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Re: The McOnie Oscillating Engine
« Reply #18 on: March 23, 2013, 01:13:55 PM »
Nick you should take a look at Anthony Mounts Kientzy far nicer than the Crosskills and this variation on the theam

Offline Ramon Wilson

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Re: The McOnie Oscillating Engine
« Reply #19 on: March 23, 2013, 01:36:54 PM »
Ah, any colour you like as long as it's black eh Jason  ;) These chaps do like their black and polished bronze don't they. I confess it's not quite my cup of tea (to see so many done in the same fashion)  but I have to admit it does look striking.

Nick, there was a series of articles by Dr Gregory on various small stationary engines in early 1974 - the oscillator I was referring to was in the Feb edition

Ramon

Edit -  Jason - following your mention above I have just seen AMs 'Kientzy' engine for the first time. Is this a relatively new model? and any idea how big it is - flywheel diameter for instance?
« Last Edit: March 23, 2013, 01:42:57 PM by Ramon »
"I ain't here for the long time but I am here for a good time"
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Online Jo

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Re: The McOnie Oscillating Engine
« Reply #20 on: March 23, 2013, 02:50:28 PM »
Anthony's Kientzy's Oscillating engine has a 228mm flywheel. If anyone is interested it was published in EIM from May 2005 to Feb 2006.

I am trying not to look at it again otherwise it might appear on my build list  :facepalm2:

(In my opinion the Germans have a very morbid theme their engine colours would not look out of place in a cemetery  :-X)

Jo
Enjoyment is more important than achievement.

Offline NickG

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The McOnie Oscillating Engine
« Reply #21 on: March 23, 2013, 03:45:52 PM »
They all look v nice but look like a heck if a lot of work above and beyond my skill set to be honest!

Offline Jasonb

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Re: The McOnie Oscillating Engine
« Reply #22 on: March 23, 2013, 04:48:53 PM »
Well I suppose the black does cover up all that brass they tend to like making engines from, though having just used up the best part of 9" of 1.5" brass rod making the governor for the Easton I can see the appeal of working in brass.

Just for you Ramon here is another version of that oscillator in a more subdude cream, there is also a kientzy in a rather bright green :ShakeHead:

http://www.vollmer-pb.de/4.html

Offline Bobp

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Re: The McOnie Oscillating Engine
« Reply #23 on: March 23, 2013, 08:55:01 PM »
Thanks Ramon and all the rest of you. I got a set of McOnie castings when they first came out and was warned there some issues. The photos really help. It is a great looking and interesting engine though and should be worth the effort when I get round to making a start on it.

Bob P

Offline Ramon Wilson

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Re: The McOnie Oscillating Engine
« Reply #24 on: March 23, 2013, 10:13:54 PM »
My word Jason am I right in thinking that is all one mans output. What gorgeous looking models, yes even the black ones. How ever does one person find the time to produce such models to such a consistency? Bet it's because they don't allow themselves to get distracted  ::)

Talking of which  :D  no sailing today - absolutely bitter east wind and wet snow - only one place to be then so made a start back on the Etas  :) Not a lot to report on them however so a little more on the McOnie.

First off though -

Thanks Ramon,

Any more details on the drawing faults will be much appreciated.

Jo

Jo, Just to make it clear, though I have found the odd error which I will point out when relevant I'm at pains to stress this is not nit picking at someones design. Overall this is going together well just that there are, as said, some pitfalls for the unwary.


One of the big 'dimensional' challenges faced on this engine was going to be getting the pivots directly opposite each other and perfectly in line both concentrically and axially as well as ideally perfectly on the centre line of the bore. Several thoughts were mulled over and finally it was decided to potentially crack two nuts together. As all ready stated I'm not keen on gunmetal and didn't particularly want a gunmetal/gunmetal piston and bore set up. The decision was made then to take the bore oversize and slightly reduce the piston diameter and insert a cast iron sleeve. This would allow cross drilling the casting right through, on centre line and in line - the sleeve then sealing the cross holes.

First off was to hold the casting very gently in the  vise on the mill and take a very thin skim cut across the port face. A  sharp new 6mm FC3 cutter was used stepping over 5mm at a time in order to keep the cutting forces to a minimum - besides keeping those cutting forces low this also produces a much 'flatter' surface than fly cutting and is a method I much prefer over the latter.

With a nice flat face still with plenty to come off the casting was set up on the lathe against an angle plate and then bored using a between centres boring bar.


After the initial clean up cut it was checked for it's relationship with the centres of the pivot bosses and also to check that the oversize bore was not going to break through the side of the cylinder then the bore was taken to size - this was not critical as the sleeve would be made to fit - and eventually, the piston made to fit the sleeve




I have found that by getting the bore in first its much easier to bring the outside surfaces to a bores centre line both dimensionally and in parallel than trying it the other way round. First thing required then is an expanding mandrel....


.... on which the cylinder is mounted to machine the ends square to the bore and to finished length.


At this point it was realised that there would be no need to machine the pivot bores right through so without removing the mandrel the chuck was transferred to the rotary table set up on the mill and the spindle set to the mandrel centre line. The port face was set square to the table then the pivot bores drilled and 'bored' by sizing with a slot drill with one flute backed off as a boring tool. It was then rotated on the mandrel 180deg, the port face reset square and the op repeated.


An angle plate was set up and the cylinder held to it with 6mm studding. The pivot bores had tight fitting 'dowels' pushed in then supporting them on two parallels the port face was milled to dimension true to the bore C/L


It was then removed to check the accuracy on the surface plate before setting it back up to mill the steam ports


After milling the ports the cylinder could be swivelled the allow the angular drilling of the steam ways....

Spot facing using an FC3 cutter held in the drill chuck to create a level surface for drilling...


and reaming the hole that will be plugged.


Finally for this post the set up to drill the steam passageways through to the port face


I've been doing this in stages tonight - sidetracked by a bit of telly  :o

I see you've posted since I started this Bob, nice to see you here.

As usual I hope some will find this useful.


Regards - Ramon

"I ain't here for the long time but I am here for a good time"
(a very apt phrase - thanks to a well meaning MEM friend)

Online Jo

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Re: The McOnie Oscillating Engine
« Reply #25 on: March 24, 2013, 06:24:32 AM »
Thanks Ramon, really useful. I saw her cylinder as the major machining challenge with this engine.

Jo 
Enjoyment is more important than achievement.

Offline Bearcar1

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Re: The McOnie Oscillating Engine
« Reply #26 on: March 24, 2013, 04:12:35 PM »
Very helpful and informative thread, Ramon. The pictures along with your clear dialog, is terrific. Like Jo stated, that cylinder arrangement can put off a lot of builders  :'( but seeing how you have overcome those obstacles is a breath of fresh air.  :praise2:


BC1
Jim

Offline steamer

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Re: The McOnie Oscillating Engine
« Reply #27 on: March 24, 2013, 04:19:24 PM »
That's an awesome post Ramon!  So many good points and tips!  Backing off a lip of the end mill was worth the trip right there...it's like a single point reamer!   Brilliant!

Thanks bud!

Dave
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Damned ijjit!

Offline Ramon Wilson

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Re: The McOnie Oscillating Engine
« Reply #28 on: March 25, 2013, 11:19:28 PM »
Hi guys -
Had a good session making conrods today but as they're not quite finished thought it might be worth adding a bit more here.

Yes Jo and Jim this cylinder is a bit thought provoking but personally I would say the crux of this model is getting those bearings machined to fit the mainframes - run through the drawings several times before making that first cut.

I took a pic tonight of the liner just to give you some idea of it's thickness - I would say it's about 1mm wall thickness and is Loctited in place (this engine will only ever run on air). The piston is bronze, about 2 thou down on diameter, finish turned after fitting to the piston rod and is fitted with 1/8 square PTFE impregnated yarn.


I mentioned using this material before on the Waller build. I prefer to use this packing for pistons as it is very easy to fit, gives an absolutely superb seal which lasts and lasts and best of all - certainly compared to using an o ring - provides very little friction. To give some idea of how little friction/good a piston seal  it's possible to turn this engine over at the moment by pushing on the cylinder and running it like a 'finger engine' - cover the ports with a piece of tape and thats no longer possible.

With the cylinder done the pivots ('steam' inlet and exhaust ) were turned from mild steel turning the ID surfaces first then finishing the outers by holding on a mandrel.


Fitted to their respective cylinder ports the cylinder was dropped into the bearings and the caps bolted up to check the alignment.
Despite some apprehension that some misalignment would occur those thoughts proved negative and it pivoted quite freely - I remember feeling extremely relieved  :)

Next up was to make the big end get the connecting rod finished so as to couple it up and get something moveing.

The strap was made by milling all the ops on the end of a piece of steel before milling the back away to leave the finished strap to fall free. One of the materials used at a place of work was one called UHB11. This was a bolster steel likened by the manufactures to En9. It machines very easily but is best attribute is that it exhibits little, if any, distortion no matter how deep a cut is taken. Ideal for this sort of work and consequently, with full permission,  the scrap bin was constantly raided  ;)


The inner end was fabricated to get the rectangular slot for the gib and cotter...


... and...  Hmm!  Err, it would appear that the pic I thought I had of the finished  big end doesn't exist  ::) so I'll have to come up with something a bit later.

All of this is beginning to have an effect - I can see I shall have to pick this project up again before too long  ;) - actually it would be nice to see it finished and running if not for this years Forncett 'do' but possibly next

Regards for now - Ramon
"I ain't here for the long time but I am here for a good time"
(a very apt phrase - thanks to a well meaning MEM friend)

Offline Stuart

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Re: The McOnie Oscillating Engine
« Reply #29 on: March 26, 2013, 07:40:04 AM »
Ramon
Very nice work and well documented

A quick question

what is the dia of the flywheel ?


my lathe is diameter challenged to 9 1/2 inches


Stuart
My aim is for a accurate part with a good finish

 

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