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Hypocycloidal Engine

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Ken I

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The Hypocycloidal design always intrigued me as I could not see any valid reason for going to such extremes when a simple crank would suffice – that was until I discovered that this was to work around various patents that had been lodged covering the crankshaft.

(Edit) I started this post calling it an "Epicyclic" - I had this wrong and have corrected it to its proper name of "hypercycloidal".

So I decided to design and build one - this is the GA

EpiGA.jpg


I will post a full set of plans and build notes when completed - hopefully successfully.

I have started on the cylinder assembly.

Regards,
Ken I
 
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vederstein

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Do you plan on purchasing or making the ring gear? If it's making, I'd like to see that process.

...Ved.
 

Ken I

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Ved,
I have made plenty of pinion and spur wheels (even from my own hobs) but I'm afraid a decent annulus is a bit much for my machinery so I'm having a friend wire cut EDM the set from my developed database.
Annulus.jpg

I posted a piece on developing profiles under Tips & Tricks because of this - I know there are packages that can do this but most won't bend or break the rules - so I thought I would do a posting as it may be of some interest to fellow members.

If you have a home brew solution to an annulus I'd like to see that.

Regards, Ken
 

Richard Carlstedt

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Matthew Murray of Leeds is the originator of the Hypocycloidal Steam Engine
He did it mostly to bypass Watt's patent on Parallel Motion on Beam Engines.
It eliminated the need for a Beam which was a huge weight and cost savings.
Murray also invented the short stroke "D" valve which we use today .

James Watt feared this man and his capabilities. I have a copy of a letter from Watt's son to his dad telling him of their efforts to infiltrate Murray's foundry/factory with 3 industrial spies ( espionage ! ) in 1803 .Watt bought all the land around Murray's foundry so he could not expand..
I look forward to your build .
Rich
 

Jasonb

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It's not to hard to cut your own internal gears, basically grind a single tooth cutter to match the drawn profile and then mount it in a holder in your mill and use the quill as a manual slotting head.

I started describing making one for an epicyclic gearbox in this thread and carry on down that page with teh finished item on the next.

 

Steamchick

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A simple ring-gear, made by another member of my local club, used a MyFord change-wheel as a pattern to cast the ring - using Mayzac zinc alloy from scrapped car and domestic appliances.... Low melting point, durable and casts well.
K
 

Ken I

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Richard - thanks for the history - steam age espionage - whodathunkit ?
JasonB - I have used a Bridgeport to broach with but my home minimill won't cut it (no pun intended).
Steamchick - now that's a clever idea - start with the ring gear and design around that - but a negative gear shape is quite a bit off an annulus - but I suppose you can compensate with the pinion - I'll give that a whirl on CAD. - I have cast parts in Mazak alloy for jukebox restoration projects.
Regards all - Ken
 
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Jasonb

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That's how Alyn Founry used to do the cast gear that they supplied, although the profile is not correct when casting from a Spur gear if you use a fairly large tooth size and allow for some running in they work OK.

Photo is a bit dark but top right shows the mould with the spur gear just visible and the resulting cast zinc rich alloy ring gear below.

You can also plane the teeth in the lathe if that is a bit heavier than your mill or even just use the slotting method to put the final profile on a cast gear.
 

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Ken I

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Just to follow up of the cast gear idea....illustration for a 16T / 32T M1.5 gearset.
GearX.jpg

Top Centre = Normal and Cast overlay
Bottom Left = Normal Annulus (blue) and Pinion (Magenta)
Bottom Right =Annulus (cast from a spur gear) Green & Pinion generated to suit (Red)

Casting an annulus from a spur gear will have the spur "clearance" extend into the pinion - which means you have to generate an undersized pinion - both those factors combined with the "pinched closed" profile of the cast annulus introduce massive undercutting into the pinion.
(After casting you could bore away the extra annulus tooth height (created by the clearance on the spur) - which will help a bit - but even then you must at least truncate the pinion to get clearance - however slight.)
This will give rise to a very strange tooth form where only the addendum will do any useful work the dedendum has to be cut away to clear the interference. As you can see below....
GearY.jpg

But yes it can be made to work - a neat idea in a pinch.

Regards - Ken
 
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JCSteam

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Ken my head hurts after reading that lol. Very informative response that I think I'll have to read again without the kids yapping in the background to digest.
Jon
 

Ken I

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Making The Cylinder & Cylinder Heads.

I chose to make all three parts from one piece of stock – as much as possible in the same setup - this process will ensure all three parts align perfectly.
I started by blocking up a piece of brass 33.5mm x 26mm x 100mm – which I then mounted vertically to drill and ream the Ø5 bore of the gland end cylinder head – as datum.
cylinder1.jpg


Photo above:
Left = drilling the Ø2.5 hole (long series drill) after the Ø5 reamed hole (datum) & the 4 x Ø3.2 bolt clearance holes deep enough for both heads – followed by the 2.5 (M3 tap size) into the cylinder.
Top Right = Mount to lathe – clocking from Ø5 datum.
Middle Right = M8 thread added + parting / forming
Bottom Right = using the part-off to turn Ø20 location boss on the backside – to ensure concentricity and save on having to set up second operation work.
cylinder2.jpg

Top Left = Finish & part-off blind end cylinder head – note: Ø3.2 holes continue through this piece but stop short in the part off gap (plan ahead – depth drilling diagram in the drawing). The Ø2.5 holes continue into the cylinder for the M3 threads.
Top Right = Finish boring the Ø20 cylinder bore.
Bottom Left = Finished cylinder and heads assemble perfectly.
Bottom Middle = Loose Parts
Bottom Right = End view – porting and gallery holes drilled.

The cluster of 9 Ø1.5 holes in the cylinder are the cross holes drilled into the gallery holes and the central exhaust port.
The “D” valve slides over these holes commutating pressure from the steam chest into the cylinder
and directing the exhaust from the cylinder to the exhaust.

The steam chest is bolted down to this face by the 4 x M2 screw holes around the ports.

Obviously care must be taken drilling all these holes to avoid inter gallery or cylinder breakthrough. Follow the drilling depths indicated in the drawing.

To be perfectly honest – the three holes side by side abreast for each gallery is excessive – you can get quite enough air through a single Ø1.5 hole to suit a running model – so it’s O.K. by me if you drill just the middle one or just the two outer ones – instead of all three. The inlet and exhaust ports are single Ø1.5 holes in any case.

Now for the steam chest and "D" valve.
Regards, Ken
 

Ken I

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Making Steam Chest & Inlet Cover.

A picture is worth 1000 words – should be self-explanatory.
chest1.jpg

Final filing is easier mounted back in the lathe chuck prior to finishing off the rear end and parting off.
chest2.jpg

The steam chest cover also has the inlet nipple which accepts a Festo KD-M5 quick coupler which I use for all my models – you can make it anything you please – also as an option in the drawing is an M3 inlet port into the side of the steam chest – you will also need an access hole through the Faux Wood Barrel to access it.
Bottom Right – I always mark the #1 Chuck Jaw position – when you return to the lathe you more or less retain your concentricity (typically within 0.1mm TIR) good enough for most second operations or parting off.

Making The “D” Valve.
I made the square cavity by center drilling the corners and working inwards with increasing diameter slot drills to depth before cleaning up.
dv1.jpg

Something of a fiddly bit to make.
To make the “U” slot (which the valve pin fits into) I first drilled the 1.5 hole and then sawed the remainder of the slot.
dv2.jpg

Below – assembled onto valve stem and assembled into the steam chest.
chest3.jpg

Cylinder Assmbly Completed.
cylinderassy.jpg

Next step the Faux Wooden Barrel & Hoops.
Regards - Ken.
 

ACHiPo

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Wow. I know my articulation can be overwhelming.:rolleyes:

Really nice work!
 

Ken I

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Deeferdog - the plans are finished - but I don't want to post them until the build is finished.
I found one small problem and it was an easy fix - but..... when it runs I'll post the plans.
Build notes are progressing with the build - should be finished within the next two weeks.
Thanks for your interest - Regards, Ken.
 
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Richard Hed

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Matthew Murray of Leeds is the originator of the Hypocycloidal Steam Engine
He did it mostly to bypass Watt's patent on Parallel Motion on Beam Engines.
It eliminated the need for a Beam which was a huge weight and cost savings.
Murray also invented the short stroke "D" valve which we use today .

James Watt feared this man and his capabilities. I have a copy of a letter from Watt's son to his dad telling him of their efforts to infiltrate Murray's foundry/factory with 3 industrial spies ( espionage ! ) in 1803 .Watt bought all the land around Murray's foundry so he could not expand..
I look forward to your build .
Rich
Yes, James Watt, like t edison, was a bustard, took advantage of his employees, stole their ideas, etc. etc.
 

Ken I

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Making The Faux Barrel.
In a fit of design exuberance, I designed an elliptical barrel – which is a PITB to make but looks nice.
barrel1.jpg

The slot down the side clears the steamchest and valvegear, the two holes in the underside are for the cylinder mounts to go through.

At this stage, I had forgotten the exhaust hole in the top side and added it later.

I had a piece of Namibian “Kameeldoring” = Camelthorn: used for making barbeque fires (makes great coals).
However it has a very attractive crown grain and red colour – it is also very dense and as hard as a whore’s heart. It sinks in water – its bone dry density is 1.06g/cc (I measured it).

Turns out it machines nicely as well.
barrel2.jpg

Top Left: Block up and machine interior, drill dowel holes for assembly alignment – the Ø2 dowels are cut from bicycle spokes.
Top Right: Glue together. Make sure it fits your cylinder assembly before this step.
Bottom Left: Mounting blocks machined from MDF to mount it accurately on an M14 threaded rod mandrel in a collet chuck. Hole is a tight fit on the bar – it is not threaded.

I used the (non-preferred) M14 as it is the largest thread that will fit through my MT2 rotary table.

In the end it didn’t need to go all the way through and I could just as easily used M16 or M20
barrel3.jpg


Top Left: Assembled (but not tightened) to collet – note turned down nut at rear.
Top Right: Collet tightened onto M14 rod and locknut tightened.
Bottom Left: Rough turning to Ø54.5 = 0.5 over finished major diameter of ellipse.

Remove from lathe to Rotary Table – which has an ER42 adaptor flange – makes moving between turning and milling operations nice and easy.
barrel4.jpg


Top Left: Setting the job level at zero degrees on the RT – I didn’t want to use the RT to level and end up with some arbitrary numbers.
Top Right – The flange “floats” slightly and can be clocked dead true – in this case clocking wood with a micrometer clock might just be considered “anal”.
Bottom Left: Co-ordinate milling the ellipse with a R6 cutter – in retrospect a flat face or side of the cutter would have been better – I have provided co-ordinates in the drawing for either option.
(Above photo) Bottom Right: Rough machining completed.
barrel5.jpg


Note the “Near Miss” indications – the mounting MDF block gave me a visible warning that I’d made a mistake. With hindsight it would have been just as well to attach a printed self adhesive label of the outline onto the MDF to act as a guide. Since the OD is only cosmetic you could use this form of “marking out” to eyeball the cuts.

Again the drawing has co-ordinates for using the corner of a milling cutter to produce fake “joints” approximating equal 8mm “planks” all round. Since the outside is still “rough” cutting the grooves is an act of faith in the data.
Back to the lathe for a quick linish to remove all the high points – and my faith in my co-ordinates was justified.
barrel6.jpg


Barrel Assembled To Cylinder - unfinished and without hoops.
barrel7.jpg

Not bad for a piece of firewood.

Next machining the hoops.

Regards, Ken
 
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Steamchick

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Lovely finish! But I first saw this type of solid lagging on engines my Father had made in the 1980s~90s. He only made cylindrical lagging though. I think your elliptical engineering deserves to be a chapter in a text book!
I have usually fabricate lagging from Balsa strips - quite thick usually - as I want "easy" lagging. (I have lagged 4 boilers with 1/2" thick balsa as it has a low thermal conductivity, and boilers need that!). I use 5mm wide x 0.5 thick brass strip to make straps. The joints and different colours and grains of the balsa planks indicate the planking without the "scribed joints" you have - and it looks guite good, but not as pretty as yours. Incidentally, I think I recall my Father making the "joints" by simply marking the wood surface with a sharp tool (perhaps a thread tool?) turned side-ways on to face the chuck, then simply marking a couple of thou deep grooves with the lathe main-shaft stationary and simply traversing the main carriage from tail to head. This is how he also marked indications on a micrometer barrel, and gauge rings when he made them for other tooling. He used a dog engaging with a gear on the main-shaft to hold it stationary and to index uniformly around the barrel. He also broached key-ways with a suitable tool and manually traversing the carriage - with a locked main-shaft.
Also. when making the deck of a boat, I used a single piece of 2mm plywood, then marked the planking simply "by eye" and a ruler, using a scriber, very carefully. When finished, the dye/varnish had developed the lines thicker where the grooves were scribed, so it looked like planking! Much easier than doing it with strips stuck on a base. Adhesive in joints seems to make the lines look wrong so must be avoided. (On Naval ships the deck-planking joints are black (Tarred), decks unvarnished, so a black fine ball pen marks those planks on my models. I know from hours of scrubbing decks!).
Hope these tips help someone? Any better ideas?
Well done and thankyou for the lesson in elliptical engineering!
K
 

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