Model Engine Maker
Help! => Specific Engine Help => Topic started by: Frank Boyle on April 29, 2015, 05:56:55 PM
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Hi all
I am going to build an oil engine in 3" scale and after measuring an existing engine I am drawing the engine to scale.I have most of the information that I need but am unsure of the compression space for the exhaust and the air inlet and if their is anyone who can give me help with this ,I would be most grateful.This engine is a hot bulb ignition.
Frank Boyle
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8) Sounds like a fascinating engine to make a model of.
Sorry I can't help you with the information you need.
Jo
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Frank,
There is some interesting information on hot bulb engines in the Model Engine Builder magazine issue 16. Most of it pertains to real engines and not models, but mentions compression ratio's, and hot bulb volume.
Jeff
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Welcome to MEM Frank. I can't help with your question either, but will enjoy following your build. If you would, take a moment to post an introduction to yourself in the Introduce Yourself section, so that we can welcome you properly.
Bill
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Hi Frank,
I saw this model of the Hornsby Akroyd oil engine at the Astle Park '1,000 Engine' Rally in 2003 and again in the Anson museum last year. It was from the defunct Alyn Foundry http://www.alynfoundry.co.uk/coming.htm. These could be a useful line of enquiry for you to follow up.
Andy
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Hi Frank
Does this diagram of a Lanz tractor engine give you any assistance?
(https://farm8.staticflickr.com/7705/17131159078_2f79261bcc.jpg)
I believe the Lanz Bulldog series of tractors, and also the Field Marshal tractors, had hot bulb engines operating on the Ackroyd principle.
John
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Hi Jeff
Thank you for your information,could you tell me where this magazine is availiable from.
Frank
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Hi Andy
I have looked at the Alyn Foundry but could get knowhere with my search. Thank you Andy
Frank
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Hi John
That diagram is helpful as at full stroke there is little space left at the head of the compression space .Thank you john.
Frank
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Hi Frank,
I seem to recall Edgar T Wesbury wrote an article in Model Engineer on Akroyd. I cannot remember the title of the article but I do remember there were details of the engine construction.
I have found the following in the Encyclopaedia Britannica, http://gluedideas.com/Encyclopedia-Britannica-Volume-12-Part-1-Hydrozoa-Jeremy/Heavy-Oil-Engines.html
From this you will see the compression ratio is very low as the compression pressure is only 85 PSI.
Also attached is a cross-section of a Hornsby which gives an idea as to the combustion space and a couple of photographs taken about 4 years ago.
My best regards
Gray,
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Can't give you the exact space but as Gray says the compression ratio needs to be quite low typically between 3 and 5 : 1.
Have you asked on any of the stationary engine forums?
I have a slightly later Ruston Hornsby BPR partly drawn up that I hope to get round to making a start on soon.
J
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John Hill is correct that the Lanz Bulldog used a hot bulb engine. There was a choice of heads/bulbs with different volumes and geometries for different fuels ranging from alcohol to tar oil. The Field Marshalls had full diesel engines although a burning paper was used to aid cold starting.
I have a couple of references to the Hornsby Akroyd engines. Hiscox:
https://ia700508.us.archive.org/2/items/gasgasolineoilen00hisciala/gasgasolineoilen00hisciala.pdf
Refers to it from page 359.
The attached scans from 'Diesel Electric Shunting Locomotives' by V. Finegan also give some information.
I hope this is of use to you.
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Hi Frank,
Model Engine Builder magazine used to be in print, but now is available only in digital form. The issue I mentioned is more than likely still available in print. Check their website at www.modelenginebuilder.com. Additional information is available about a model builder in Denmark named Find Hansen. The Joe Martin Museum did a feature article on Find Hansen that can be viewed here http://www.craftsmanshipmuseum.com/Hansen.htm. This article also includes links to many of Find Hansen's great video's of his hot bulb and full diesel models in operation. Definitely worth a look!
I own a 1.5 hp Mietz & Weiss hot bulb engine made in NYC. It is a 2 stroke crankcase scavenged engine unlike the 4 stroke H-A engines. Literature states the M&W compression was about 65 psi which is quite low. They used a water drip, or steam condensate from the cooling system to control early ignition under heavy loads. Good idea, and it worked, but they found that water wasn't a great cylinder lubricant. About 40% of the fuel usually went up the exhaust stack as unburnt fuel, but insurance companies preferred them in 1900 to gasoline engines when used inside buildings. I believe the 4 stroke hot bulb engines were a little more fuel efficient than the 2 stroke engines. There were a lot of different hot bulb engine fuel systems back then, mostly different in where and when the fuel was injected.
Jeff
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We have a Ruston Hornsby HR 6 oil engine, it's not a hot bulb type, but doesn't seem to have a high compression. We run it as a demonstration at our museum, short runs and light load.
One of my favorate engines was a gas powered Ruston ? Akroyd engine that we had in the mechanics lab at Tech in Dunedin in the 1960s. We used to sneak in at lunch time, and start it, all 7hp, and dead silent.
Ian S C :naughty:
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Hi frank if you are still intrested in some info I can get in touch with my dad. Hi Andy
I have looked at the Alyn Foundry but could get knowhere with my search. Thank you Andy
Frank
Thanks Mathew, I noticed this thread some time ago but lost it! My advice, for what it's worth, is don't expect a decent runner. Unless you're building a quarter scale from a very large HP engine.
The pictures posted earlier by Chipmaster are our attempt at a quarter scale 2.5 HP Akroyd. We had a compression presure of 65 PSI and also fitted a series of " booster plates " inside the inlet / exhaust valve chest, just like Hornsby did.
As I saw it you can physically scale things but the elementals remain a constant.
What did surprise me was that the fuel pump worked really well and we were even able to produce fuel spray. The injector hole was made by first fine Diamond grinding a piece of quality tool steel and delicately punching the end of the injector outer sleeve.
I'm not in any way trying to deter you but after spending nine months of hard work that ended up being a stationary, stationary engine I thought it best to inform you.
Kind regards, Graham.
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Hi Graham
My apologies for not following the replys to my post,but to practice building an engine I bought and started an ETW Centaur which I am progressing with.
I did construct the injector for the Hornby Acroyd in 3" scale and have yet to test it,I was waiting to build the fuel pump.Building the injector was a decider wether I went ahead with the project or not.Having never built an ic engine I am still practicing.Thank you for the information and I accept the advice of a more informed constructer.I did visit the Anson museum two weeks ago but there was nobody availiable to discuss the hot bulb model ,I should have viewed the replies on this post .Thanks again Graham.
Frank