Author Topic: Model Heinrici Engine  (Read 8310 times)

Offline Alyn Foundry

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Re: Model Heinrici Engine
« Reply #30 on: November 09, 2020, 05:57:43 PM »
Hi Jo.

Your set of castings is Andy's interpretation of the E T Westbury design. On the square water jacket you might notice a rather steep angle of draught around each water outlet? This was done to make the " draw " from the sand mould easier to accomplish.

Andy has let all his engines go apart from a couple of his favourites, a Robinson and a very early LT ignition Bamford, sorry no pictures either.

Cheers Graham.

Offline Dave Otto

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Re: Model Heinrici Engine
« Reply #31 on: November 09, 2020, 06:19:48 PM »
Hi Dave

People get quite confused by the alpha, beta and gamma configurations of Stirling engines. I am not sure if the terminology is very helpful but I suppose using Greek letters adds an air of academic respectability. The gamma configuration has separate power cylinder and displacer chamber that are linked by a tube. This configuration gives a lot of flexibility for the linkage so for example the power cylinder and the displacer chamber can be at 90 degrees to one another and both work from a single crank pin (As the Stirling 90 described by Anthony Mount in Historic Engines worth Modelling Vol 1) or the two chambers can be parallel to one another and the linkage uses two crank pins 90 degrees apart (Typical of Heinrici HA) or by the use of a bell crank linkage (as used by T E Haynes in his engine described in Model Engineering for Schools Book 2 Incidentally this engine has been described by others  in the model engineering world but without giving Mr Haynes his due recognition) The downside of the gamma configuration is the dead space due to the air in the transfer pipe and possible restriction of the pressure pulse between the displacer chamber where it is generated and the power cylinder.

The beta configuration has the power cylinder coaxial with the displacer chamber and in the best designs the stroke of the power piston overlaps with the swept volume of the displacer. There are lots of engines that work like this such as the Rider Ericsson pumping engine and the Heinrici HL type. From my observations at Stirling rallies and exhibition stands beta engines outperform gamma engines and I have always attributed this to the reduction in dead volume and the free flow of air between the working cylinder in the displacer chamber.

The enigma is the alpha engine. These should be the best engines in terms of specific power output and the ones that have been well documented do indeed run very well and produce a lot of power for their size. That being the case why in over 10 years of exhibiting Stirling engines at model engineering shows and rallies have I only ever seen one alpha engine running? The alpha has two pistons set 90 degrees apart and the cylinders are connected by a transfer pipe that often incorporates a regenerator. In full size the Haywood Tyler engine is an example of an alpha engine. I suspect some Haywood Tyler models are actually gamma configuration engines rather than true alpha engines.

Rather contentiously, is an alpha engine just a gamma engine with a big fat displacer rod the same diameter as the bore of the displacer chamber??

Bob

Thanks Bob!

Dave

Offline Jo

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Re: Model Heinrici Engine
« Reply #32 on: November 09, 2020, 06:27:17 PM »
Your set of castings is Andy's interpretation of the E T Westbury design. On the square water jacket you might notice a rather steep angle of draught around each water outlet? This was done to make the " draw " from the sand mould easier to accomplish.

Thanks Graham,

I will be building it as a copy of Westbury's design of the Heinrici so that it can go with the Air cooled Heinrici Engine that came from Westbury's own engine collection. I will work on the assumption that the two ali flywheels will be heavy enough as my Rider-Ericsson runs ok with an Ali wheel.

Jo
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Offline Jasonb

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Re: Model Heinrici Engine
« Reply #33 on: November 09, 2020, 06:32:11 PM »

It is full sized: it has a 30mm bore same as the original Heinrici engine.

Jo

So which is the correct bore? Westbury's one from reeves is 1" presumably his best guess at what would have been a 26mm bore or your engine which has a 30mm bore.

Or did Andy scale it up a bit to suit an old shock absorber he had going spare?

EDIT, Ignore that Reeves describe it as 1" but drawing is 1 3/16" which is close enough for 30mm
« Last Edit: November 09, 2020, 06:49:29 PM by Jasonb »

Offline Jo

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Re: Model Heinrici Engine
« Reply #34 on: November 10, 2020, 12:32:00 PM »
The water jacket has been bored and the four mounting holes drilled 4.1mm using a long series drill. Then on to the cover: this is a square shaped casting that needs turning - it can be mounted up in a four jaw independent chuck but even easier the four jaw self centring chuck  :)

I have modified the design as I have chosen to add a bronze bush in the centre of the cover as I am not sure an aluminium cover is not going to wear and the hole will become oval. The cover was bored and a piece of bronze loctitied in before completing the machining.

I found a tipped tool supplier who could provide me round tipped tools of 6mm, 8mm, 10mm and 12mm diameter using one of these tool the curved surface was turned.

The top surface also has a curved feature. These tipped tools cannot be used to form this as they do not have sufficient clearance so I had to go back to using one of my old bits of HSS and even then the groove is only 4mm deep not the 6mm shown on the drawing.

I now have three parts with three different diameters which are joined together using the liner so it must be time to turn that up

Jo
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Offline Roger B

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Re: Model Heinrici Engine
« Reply #35 on: November 10, 2020, 05:06:32 PM »
That's some rather nice metal sculpting  :praise2:  :wine1:
Best regards

Roger

Offline JULIUS

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Re: Model Heinrici Engine
« Reply #36 on: November 10, 2020, 07:29:52 PM »
Jo

I have attached some drawings of the Heinrici model which I made years ago
These drawings are in imperial measurements.
I hope they might help. If you look on my disc it is under project number 05A-05-00

Julius

Offline Jo

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Re: Model Heinrici Engine
« Reply #37 on: November 10, 2020, 07:47:11 PM »
Thank you Roger  :)

And Thank you Julius, I had noted that your design has a round cylinder jacket which is something we were discussing yesterday

Jo
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Offline Jo

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Re: Model Heinrici Engine
« Reply #38 on: November 11, 2020, 04:05:41 PM »
A small drill was used to start the hole through the piece of Cast Iron bar. (I tried not to think about all those piston rings I was wasting  :wallbang: ) Then my small hole precision boring bar was employed to open it up so the cover fitted in the hole. Then holding one end then the other it was turned such that the bottom would fit in the platform, the bottom/middle would fit into the lower part of the water jacket before turning round and machining top to fit the top of the water jacket and finishing off by using a round turning tool to undercut the middle.

This undercut is supposed to help with assembly but you have to be careful on such large diameters is is amazing just how little off square you need to be with a liner for everything to lock solid as you try pushing it in  :ShakeHead: Talking of locking solid: Straight of the lathe I decide to assemble everything, first dropping on the top cover which promptly locked in place solid  :wallbang: Of course the cast iron had been a little warm straight of Big C and as it cooled is shrank and it would have only taken one piece of dirt :facepalm: Having encouraged the cover off I used a brake liner hone to take off a nats whisker from the top bore and it is now fitting nicely again.

I finished off by assembling everything. It was only once I came inside I started wondering if I had the liner the correct length  :thinking: It looks long in that pic. I'll check in the morning - it is easily corrected if needed  ;)

Jo
Enjoyment is more important than achievement.

Offline Roger B

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Re: Model Heinrici Engine
« Reply #39 on: November 11, 2020, 04:58:26 PM »
I take the cores out of cylinders etc. with a hole saw. With my low powered machines it is much quicker than step drilling and boring and you save most of the material  :)
Best regards

Roger

Offline Jo

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Re: Model Heinrici Engine
« Reply #40 on: November 11, 2020, 05:13:24 PM »
Thanks Roger,

Sadly this lump was 85mm long and my hole saws (which I have been known to employ like you did  ;) ) do not have the required depth  :-\

Jo
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Offline Roger B

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Re: Model Heinrici Engine
« Reply #41 on: November 11, 2020, 07:56:02 PM »
Yup, that's just over the limit  :( I have done 80mm for the horizontal engine and the diesel.
Best regards

Roger

Offline Jasonb

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Re: Model Heinrici Engine
« Reply #42 on: November 11, 2020, 08:03:53 PM »
The trick is when you drill the second end bore away some of the "plug" so that the holesaw can meet the cut from the first side ;)

Offline crueby

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Re: Model Heinrici Engine
« Reply #43 on: November 11, 2020, 08:07:06 PM »
Never tried using a hole saw like that - does it take a special type for cutting metal, or will the normal hardware store ones work well enough?

Offline Roger B

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Re: Model Heinrici Engine
« Reply #44 on: November 12, 2020, 07:38:03 AM »
I use Bosch Bimetallic ones from the local shop. They work well on cast iron but can tend to clog up with swarf on alumuinium. I haven't tried on brass or steel.
Best regards

Roger