Heinrici engine

Has anyone built the Heinrici hot air engine with castings supplied by Reeves ?

Any problems ?

BUMP...................................

Looks like no one has built it.............................

I've not seen any build threads on the various forums that I visit so can only assume it its not a very popular engine or all the builders are keeping quiet. The Ryder and Robinson engines seem to be more popular when it comes to casting sets for hot air engines.

I've just built this Stirling hot air engine , based on the Heinrici engine, all fabricated except the flywheels,

7" wheels, 21" to top of wheels, coke can for size comparison, heat is a small Primus 8842 propane burner,

Runs lovely, water cooled cold end is aluminium, hot end is brass with copper end,

Has been a nice project.

Richard.

Nice job, Richard

If anyone repeats your opening question ... we will have an answer

MichaelG.

Here's a question for the Stirling engine experts out there,.............Will a stirling engine "scale up" ?

I've just built the engine in this thread, it has 7" flywheels, I have in stock a couple of 14" flywheels and would like to build another engine twice the size ,

My question is will it scale up and run the same as the smaller one, with a larger burner of course.

Richard.

Any comments ?

OK I will make a response and maybe somebody who actually knows something might respond.

https://www.stirlingengine.com/forums/viewtopic.php?f=3&t=134 a liitle discussion in that thread may be of use to you.

I googled "scale up stirling engine" - have been pondering that question recently.

Bill

I've just bought a set of castings and drawings for this engine, and I'll be starting the build over the Christmas period. As has been mentioned above in this thread, there seems to be very little info online about these engines. I'll start a thread and try and keep a regular update of build pictures throughout.

Good Health

Will

You might want to have a look at Jo's build over on MEM, although not from the Reeves castings it is very similar, you will need to register to see the images.

I've also just started on one, see this thread, again not from Reeves castings or the same design

In the wonderful future, when normality returns, The Stirling Engine Society has a stand at various shows, and hold a meet each year at The WaterWorks Museum in Hereford.

Your engine would be a welcome addition to the display, I would imagine.

Howard

Engines built from the Reeves castings do seem very few and far between. I've previously only made steam engines. From reading various forum posts it would seem there is definitely a different knack required for building Stirling engines. In terms of the absolute free running nature of them, lack of tight spots etc...

I'll have lots of questions no doubt!

Afternoon all,

As promised, I started on my set of castings just after Christmas, as my Stuart Beam took a little bit longer than planned. I'm afraid the pictures are in reverse order.

So far the parts for this engine seem relatively straightforward, the conrod was made on a Saturday, meaning I had a good 10 hours of making. The biggest piece of grief that came with the conrod was a broken drill almost immediately after centre drilling for the big end bolts. A 2mm drill from a brand new 'draper' set I had received for Christmas, this meant that instead of drilling straight through the big end, I had to split the big end first and then meet the broken drill from the other side before attacking it for a good period of time with a punch. Luckily I managed to get all the pieces out and from there on in it was plain sailing. On a side note the drill set has gone back to the seller after I took out the 2.5mm drill, put it in the lathe and measured the run out at the tip. This measure 2.5mm, gobsmacked that anyone can be producing such tat in this day and age.

The cylinder was a much smoother affair. The only grief coming from trying to get a top finish over the 3 inch stroke of the bore. This took many many passes and a lot of patience, but hopefully you'll be able to see from the picture, I got there in the end.

I've now started work on the piston and piston yoke. my first impressions of the piston design is that it will make an awful lot of cast iron waste.

Will

I started to make the piston last night and after a few hours of what seemed like endless swarf making, I had finished, it seems to fit in the bore snugly at the moment, but I think after some running in in oil it should be perfect for this engine. Tonight I will start on the piston yoke. the finish is as good as i can make it at the moment, it was done using a round nosed tipped tool, traversed by hand rather than by using the carriage feed. Myford running at about 900rpm, it took me a few minutes to traverse the 1 1/2" but the finish came up quite well. Again, when run in with oil i'm sure they will bed together nicely.

This weekend had brought about some rapid progress on the Westbury Heinrici. It seems the duo of no housework and a national lockdown is good for model engineering.

I've created an album for the build of this engine, which is HERE

If anyone would like to know more about this don't hesitate to ask.

A few notes as i've been building I've included here. As with the posts above, I'd be glad to hear from someone else who has built one of these for any tips and tricks.

Piston yoke boss machined.

Piston yoke turned around in chuck for machining

Piston yoke with all turning complete

piston yoke having slot milled for conrod

completed piston and gudgeon pin assembly

completed piston and conrod

completed piston and conrod, please excuse the snacks...

displacer rod in the lathe, thread slightly recessed to provide a perfect parallel alignment between it and the cap

displacer cap machined and test fitted to displacer itself. whilst also being screwed into displacer rod and in turn conrod.

machining hot end cap outer

machining hot end cap, innerfinished hot end cap, test fitted to hot end.

It's coming along nicely, I was doing the cap for mine yesterday.

Scaling probably deserves a thread of it's own. It's a big subject and I've never seen a book on it.

With mechanical objects, including engines, it's generally easier to scale up than down, so the outlook for a Stirling Engine is rosy. But there are pitfalls.

Consider a full size steam locomotive. Heat loss from the boiler is proportional to the ratio between its surface area and volume. And because volume is proportional to the square of the diameter, while surface area is proportional to a plain multiplication, small boilers leak heat disproportionally faster than big ones. With boilers the bigger the better, and scaling them down to make a model loco automatically means the model can't be as efficient as the prototype. (Anyone built a working N-Gauge Steam Loco?)

As Stirling Engines leak heat, they benefit from being big rather than small.

But nothing is ever easy! The strength of materials doesn't scale up linearly, so building bigger means checking details. Big boilers are very dangerous. A decent dart glider can be made from a sheet of A4 paper, but the same design scaled up to 2 by 3 metres is a floppy disaster: there's a point beyond which paper can't support it's own weight. The same is true of all materials; no problem building house walls with bricks, but they can't take the weight of a skyscraper. And there's a limit to the maximum height of those too.

Weight and strength need looking at together. Simply scaling up a model piston to full size will make it heavier than it need be, and cylinders and frames will probably use more metal than is actually needed. Or not! Most model ships are strong enough to be picked up at one end. A full-size ship would break if subjected to an equivalent lift - they depend on the support provided by water and dry-docking requires careful positioning of wooden beams. It's not economic to make ships stronger than they have to be - extra metal & construction has to be paid for and then shifting unnecessary weight around the world is commercial suicide. Engineering with hard sums, not non-critical construction in a shed.

Unlikely to be a problem with Stirling Engines, but flywheel strength needs careful watching. The force applied to spokes and rim is proportional to the square of the diameter and to the square of the velocity. Big flywheels require careful design, suitable materials and competent construction because they store a lot of energy and can burst.

I've failed to find a reference to the relative sizes of Stirling Engine volumes, but I vaguely remember there's an optimum ratio between hot, cold and regenerator spaces. Do any of our Stirling experts recall that? If so, would pay to check that the working volume ratios of the model stay the same when the dimesions are scaled up.

Hope that's not too depressing because I think modestly scaling up a Stirling Engine should be relatively painless. But it depends how large you intend? Big difference between twice model size and an Engine producing tens of Horse Power.

Dave

Well Heinrici did not have too many problems scaling them up, the Reeves one is the same same as the engine on the left being one of their smaller offerings. So no problem doubling up the geometry but things like the thickness of the displacer piston's walls would not want to be double as you will end up with a lot of weight to lift that will then want to drop. Worth mentioning that the Reeves one is approx a 1:1 model

Edited By JasonB on 11/01/2021 16:13:37

Yesterday evening brought about some more machining time. I had already decided against trying to cut a 2" x 24 TPI thread on the hot end cap and liner. So as the drawing suggests I went down the grub screw route. I had stacks of 4BA grub screws so instead of the 4 on the drawing I decided to put 6 in. to aid with this, I clamped up the hot end cap in the rotary table and spotted with a pin pointed centre drill the 6 holes for tapping 4BA.

I don't know if anyone else has any tips for drilling bronze / gunmetal, but i find it the most awful thing to drill. It is of no value to pilot drill as this will just cause the drill to snatch in an attempt by the drill press to remove your arm.

After very careful drilling at 3mm to 4BA tapping size I moved on to machining the flywheels.

The flywheels are slightly different as can be seen in the pictures, one has a cast boss for the crank pin and the other does not.

I started on the non-crank pin flywheel. this turned out to be an odd setup in the lathe, as the boss on the flywheel was not centred well enough, nor did it have enough protruding for me to get a good grip on it in the chuck.

Whilst playing around with the flywheel I realised that the inside of the flywheel tread was actually in good shape, and appeared to run nearly true. After a bit of fettling I decided this was the best way forward for work holding.

So I set the lathe in back gear running at around 40rpm and set to work. the quality of the iron was very good apart from the expected scale on the outer elements. Once the scale was removed and the flywheel was round, I picked up the rpm to 200 and went for finishing cuts.

I have centre drilled and machined the boss ready to be drilled and reamed 3/8".

All being well I should be able to get that and the other side machined tonight. If all goes very well I should be able to make a start on the crank side flywheel.