Open crank horizontal engine conversion to Stirling cycle.

Discussion on Stirling or "hot air" engines (all types)
Artificer7
Posts: 4
Joined: Wed Jan 03, 2018 3:18 am

Open crank horizontal engine conversion to Stirling cycle.

Postby Artificer7 » Wed Jan 03, 2018 3:53 am

Dear Stirling Brains Trust,

I'm planning to convert a 2hp open crank horizontal internal combustion engine to single cylinder Beta configuration. The arrangement will pretty well be a copy of a Henrici engine owned by a friend, except of course it will be horizontal. The engine is to drive a spit roasting rig which currently has a steam engine driving it, also a converted open crank horizontal ICE I built for the task. The steam engine actually runs on compressed air for safety reasons but I'm now thinking hot air is the way to go. The bore is 3.5" with a 5" stroke and is an Australian copy of the American Waterloo Boy as far as I know. Firstly, is this a fools errand? Thinking the horizontal configuration will have more friction than the vertical Henrici but hoping it is not a fatal flaw. Wondering if anyone here has any experience in a similar venture? Anyway, thanks for the add and looking forward to entering the wonderful world of hot air. Cheers, Dave.

Alfista
Posts: 68
Joined: Thu Feb 18, 2016 9:14 pm

better to start from scratch

Postby Alfista » Wed Jan 03, 2018 8:41 am

At the risk of being seen as a heretic, I would say, don't do it. It sounds like a nice, old engine worth restoring as a gasoline engine. It may be worth watching the unsuccessful attempt of the conversion of an air compressor by Dan Rojas on the Greenpowerscience youtube channel as you would face many of the same challenges.

I will not give you a full critique on this but in my opinion, you would be better off building up from scratch. Check out the videos of Approtechie. He does amazing work. However, if you have access to a lathe and mill, then you could look at plans by Rudy Kouhoupt, Jerry Howell and others, which would be my best recommendation.

To add to my heresy, I would suggest that if safety is your only concern about the steam, then why not build a flash boiler. It is a much, much easier job than building your proposed conversion. LynxSteam on youtube gives step by step building instructions. Here is the first in the series :


https://youtu.be/fKaIofi3bGc

Artificer7
Posts: 4
Joined: Wed Jan 03, 2018 3:18 am

Re: Open crank horizontal engine conversion to Stirling cycle.

Postby Artificer7 » Wed Jan 03, 2018 12:51 pm

Thanks very much for your thoughts Alfista. I will investigate all your suggestions. The engine in question is very common and pretty well only a block and crank with flywheels in "garden ornament" condition, but nonetheless, I never do anything that will cause a future restorer to curse my name so all good there. I was actually heading towards a flash boiler until I discovered how much compressed air it takes to run my frankensteamer - a bit of heat from the spit was never going to cut it and we were heading towards a more efficient scratch built steam engine before hot air popped up. Off to check out Greenpowerscience right now!

cbstirling2
Posts: 128
Joined: Sat Dec 17, 2016 9:35 pm

Re: Open crank horizontal engine conversion to Stirling cycle.

Postby cbstirling2 » Thu Jan 04, 2018 11:29 am

I think a horizontal cylinder has too much friction imho.
CBStirling2

Wellington
Posts: 130
Joined: Mon Apr 18, 2016 4:02 am

Re: Open crank horizontal engine conversion to Stirling cycle.

Postby Wellington » Thu Jan 04, 2018 11:40 am

Artificer7 wrote:Dear Stirling Brains Trust,

I'm planning to convert a 2hp open crank horizontal internal combustion engine to single cylinder Beta configuration......


I remember reading the first paragraph of the Andy Ross book on stirling engines. It read something like: "The first thing you have to do is get all ideas of converting an engine into a stirling engine out of your mind". He goes on to say that it usually turns into a big headache with too many variables to predict and get results and it is just so much easier to start building a stirling from scratch. Andy Ross is widely concidered a jedi knight stirling engine builder.

Hope that helps

Artificer7
Posts: 4
Joined: Wed Jan 03, 2018 3:18 am

Re: Open crank horizontal engine conversion to Stirling cycle.

Postby Artificer7 » Thu Jan 04, 2018 12:42 pm

Thanks very much Wellington - I'll read Andy's book before I embark on this project. The lack of conversions on youtube is probably also indicative of practicality.

Ian S C
Posts: 2007
Joined: Thu Dec 02, 2010 5:15 am
Location: New Zealand

Re: Open crank horizontal engine conversion to Stirling cycle.

Postby Ian S C » Fri Jan 05, 2018 3:22 am

there is a thread on this site of the conversion of a V twin compressor to Stirling Engine, I'm unsure of the outcome of that enterprise, but I suspect it wasn't as good as expected, it may not have even been finished.
The sort of thing that needs looking at is the weight of the crankshaft, the original one you have is about 1 1/2" dia, in plain bronze bearings, for the Stirling Engine about 5/8" to 3/4" dia running in ball bearings, a much lighter flywheel, and a piston without rings, and much lighter but still cast iron. Unless you propose to link the displacer to the crank via a bell crank, you will need a shaft with two crank throws 90* apart.
You'll be able to get rid of the carby, the mag, and the hit and miss gear, and the old cylinder head.
Ian S C

Artificer7
Posts: 4
Joined: Wed Jan 03, 2018 3:18 am

Re: Open crank horizontal engine conversion to Stirling cycle.

Postby Artificer7 » Fri Jan 05, 2018 9:58 pm

Thanks very much Ian. My "donor" engine is only a block, piston, rod, crank and flywheels so no parts to ditch. I wouldn't be considering the conversion with anything remotely complete or likely to be restored any time soon. I have a four of these engines in total, one complete and another waiting for a side shaft conversion to replace its missing components. Leaning a lot closer to scratch building a walking beam Beta along the lines of the horizontal displacer models. Still planning to use the Rosebery crank and flywheels but ball bearing mains would seem like a really good idea. I'll check that thread now :)

Ian S C
Posts: 2007
Joined: Thu Dec 02, 2010 5:15 am
Location: New Zealand

Re: Open crank horizontal engine conversion to Stirling cycle.

Postby Ian S C » Sat Jan 06, 2018 2:22 am

The crank is far too heavy, you might get away with using one of the flywheels, extra weight means extra friction. You could chose ball races that fit in the existing bearings, and make a new shaft, it could be quite complex arranging the bell crank needed to run the displacer off a single crank along with the power piston. Normally both the piston and displacer are the same diameter, so the displacer crank would have a longer throw to give the ratio between the two of 1.5 : 1. With the bell crank this it achieved by adjusting the length of the arms of the bell crank. This little GAMMA motor uses a bell crank to operate the displacer.
Ian S C
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