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Bluewater Bulletin
Bluewater Model Engineering Society Sarnia, Ontario
Vol. 30 No.8 May 2015 Editor John Lovegrove
Our next Meeting (and last of the season) will be on
Monday June 15th, 2015 @ 7:30 pm
Northern Collegiate Machine Shop (Rm. 148), Indian Road, Sarnia.
The May Meeting
There was some discussion about newsletters from
other ME societies. We already exchange
newsletters with the Richmond Hill Live Steamers, we
now have a proposal to exchange them with the
Toronto Society of Model Engineers. It was agreed
that we should go ahead with this and I will circulate
the newsletters received when I send out our own.
Bruce Mannerow talked about the new “projects”
section on our website and would like members to
submit information on the projects they are working
on (pictures, brief descriptions) that can be included.
There was also a suggestion that information on what
is in our library could be added to the website.
We discussed whether to hold a June meeting this
year and also whether to have a summer party/picnic
in early July. The answer was yes to both.
something of a relatively low cost flying look-alike
since according to one source they are using a 250
HP Isuzu engine (the original Merlin produced almost
10x that power.)
Show and Tell
Tony Koolen brought along a chain sprocket that he
has made for the drive on his electric locomotive. He
started by drilling a series of holes in the blank;
corresponding to where the chain rollers will sit. Initial
forming of the tooth shape was carried out using a
gear cutter (on the right) then a file was used to finish
off. He now has a 24V motor for the locomotive, this
runs faster than the one installed previously and
therefore needs a greater reduction ratio.
Tony's sprocket
Apparently John Shelley’s partially completed
(English) traction engine is now for sale. Details were
sketchy but John’s workmanship was excellent and so
one can expect that what he did manage to complete
will be of a high standard.
Bruce talked about the apparent phasing out of the
old style soft solder that contains lead. Lead free
solder was originally introduced for plumbing
applications to avoid getting lead into drinking water
but now seems to be becoming the only type
available. Unfortunately it does not flow as well as
the leaded variety and for many applications the
presence of lead is not an issue. After trying several
places he found some of the lead containing type in
the hardware store near his home in Forest.
Apparently Princess Auto also stock it. Something
else that is also getting very difficult to find is the
Kasey Schuilenberg brought along an indexing device
he has acquired. It uses 5C collets, is designed to
give 100 major angular increments and 10 increments
liquid “acid” flux (zinc chloride is the active
component.) Menards in the US seems to be the only
place we know of where it is still available (better
stock up while they still have some!)
Another subject discussed was the 0.9 scale
reproduction Spitfires being made in the UK. The
person responsible is Paul Fowler and it seems to be
where the user is supposed be exercising and
providing the power.)
Kasey’s Indexing Device
using a kind of Vernier arrangement. He plans to use
it for drilling holes in the spoked (wagon) wheels that
he makes. (Precision drilling holes in both the rim
and the hub should make lining everything up and
fitting the spokes much easier.)
Peter Esser had the motor and speed controller from
an old treadmill. He plans to use it to drive his Taig
lathe. The motor is rated at ~ 2hp and just looking at
the size it will probably be running at high speed to
develop that power. It is a DC brush motor with what
looks like a thyristor speed controller complete with
tacho generator for feedback control. (I have often
wondered why one needs a 2hp motor on something
dates have become available. Bruce will post the
complete, updated list on our website.
The Lathe that is For Sale
Peter’s Treadmill Motor and Controller
Our Summer Party/Get-together
This will be on Thursday, July 2nd. Please save the
date – more details later.
Hot Bulb Engines
From time to time I try to put something extra in the
newsletter apart from the normal report on the
meeting etc. The subject of Hot Bulb Engines is one
that has interested me for some time and it came up
in some discussion with Reg Miller a few weeks ago.
Therefore I thought that I would try to share what I
have managed to learn on the subject.
Herbert Akroyd Stuart is credited with inventing this
type of engine; initial development took place in the
mid-1880s and the first engines came off the
production line in the early 1890s. Over the years,
these engines evolved in a number of ways before
they were eventually superseded by true diesel or
compression ignition engines. Although generally
known as hot bulb or semi-diesel engines, probably
the most appropriate generic term is surface ignition
(as opposed to spark or compression ignition.)
Looking at some of the fundamentals; all fuels have
what is known as an auto ignition temperature
whereby if the fuel is heated to that temperature and
held there long enough, it will eventually ignite. The
higher the temperature is above the auto ignition
temperature the shorter the delay before ignition
actually occurs. In practice the temperature has to be
well above the auto ignition temperature for ignition to
occur in the time available in typical engine operation.
(It is rather like throwing a log on a dull burning fire
when it will smolder for a while before catching fire,
compared with throwing it on a brightly burning fire
when it bursts into flame almost immediately.)
Another important factor is pressure, the higher the
pressure the shorter the ignition delay.
In a spark ignition engine the temperature of the spark
is way above the auto-ignition temperature of the fuel,
so if a combustible mixture is present it will ignite
It seems possible that the hot bulb arrangement might
have been partially inspired by the hot tube but
adapted for use with heavier (higher boiling point)
fuels.
As with a diesel engine the air was not throttled and
the power output was adjusted through the amount of
fuel injected. This means that the overall fuel/air ratio
varied significantly and at lower power outputs
operation relied on having zones in the hot bulb
where the fuel concentration was higher than the
average so that at least some of the fuel/air mixture
was in the combustible range.
It has always seemed to me that getting the
arrangement to work, given the issues around
producing some form of combustible mixture over the
whole power range and getting it to ignite at about the
right time using a hot surface with no real temperature
I brought along a couple of camshafts that I had
milled using the techniques presented in my seminar
at NAMES. Further machining case hardening and
final grinding are still required
John's Cranks
For Sale
Peter Esser mentioned a lathe that someone he
knows has for sale. He has now provided a picture
and owner information. The person is Pete Wilkins
519-336-5242 or 4806. The note also says call 1:00
on Saturday. It looks like a real antique c/w line-shaft
drive.
Shows this Summer
The schedule in last month’s newsletter had a few
dates missing. Some of these are now available but
rather than include the whole list again, at the end I
have just attached a (short) list of the ones where
essentially immediately. In a diesel engine one relies
on the temperature developed by compression being
sufficiently above the auto ignition temperature to
bring about ignition during the time available near the
end of the compression stroke. (The high
compression pressure also helps in its own right.)
In a hot bulb engine there is no spark and the
compression ratio is too low to reach the ignition
temperature. What one relies on is having a hot
surface available to initiate combustion. The original
engines made by Hornsby Akroyd were 4 stroke with
a heated bulb that formed the combustion chamber
essentially separate from the cylinder. The
compression ratio was ~3:1 and fuel was injected into
the hot bulb during the intake stroke while air was
drawn into the cylinder (but not through the hot bulb.)
Vaporization of the fuel occurred but there was no
ignition at this point. During the compression stroke,
air was pushed into the hot bulb and at some point a
combustible mixture was formed (at least in some part
of the hot bulb.) This, along with the right
temperature and pressure resulted in ignition and
combustion of the fuel taking place. Below is a
sectional arrangement of one of these engines
showing the hot bulb vaporizer. The inlet and exhaust
valves are not seen in this view, they are in a pocket
behind the cylinder.
control, must be in total contravention of Murphy’s
Law. However, work they did. The only reasonably
constant factor was the compression pressure, given
the un-throttled air admission, so maybe it is this
(working in conjunction with a sufficiently high surface
temperature) that really allows them to work.
There are still some of the early engines in working
order in the UK but I have not seen one running.
There is a Hornsby Akroyd engine from 1986 at the
Anson Engine Museum just South of Manchester but
this has not been restored.
They did licence manufacture of the engines to De La
Vergne in New York and one of their engines can be
seen in operation at the Coolspring Power Museum in
PA.
The one below is from 1902, has a 16” bore, 20”
stroke and develops all of 35 HP.
With a compression ratio of only ~3:1 these engines
were not very efficient but they had some significant
advantages over other sources of power available at
the time. Compared with a steam engine, they did not
require a person in attendance essentially the whole
time.
(at a relatively low pressure) into the hot bulb. The
vapour then formed mixed fairly easily with the air.
However, the heterogeneity of the mixture meant that
combustion was still not complete. The exhaust was
usually fairly smoky but this was much less of an
issue when the engines were in their heyday than it
would be now.
Another problem with these engines was coping with
the whole range of loading. When idling, insufficient
heat was generated in the hot bulb to keep it hot
enough. (The Coolspring engine runs with a gas
burner on all the time.) At the other end of the load
range the amount of fuel being burned results in high
pressures and detonation of the mixture. Water
injection was generally used to “dampen down” the
combustion and minimize the problem. I have also
seen reference to problems using oils from different
sources that have different ignition characteristics. It
seems that the hot bulb/combustion chamber design
was varied somewhat to accommodate the different
fuels.
All of what I have written so far is fairly easy to glean
from readily available literature but over the next 40
years or so there was an evolution in the design so
that it became much more of a “semi diesel” than the
early engines. Piecing this together is much more
One story I have read is that Herbert Akroyd Stuart
accidentally spilled some kerosene into a pot of
molten tin and it caught fire and this gave him the
inspiration for his engine. However, the hot tube
system was being used from at least the early 1880s
as a means of ignition for gas engines. (“Gas” in this
case mainly means coal or town gas.) Electrical
ignition systems were not very practical back then and
the hot tube was a simple alternative. It comprised a
small diameter tube (~ ¼”) and was brought to red
heat by a gas flame. During the compression stroke
the gas/air mixture was forced into the tube and when
it reached the hot part, the combination of
temperature and pressure brought about ignition.
Timing was not very precise but some adjustment
was possible primarily by changing the length of the
tube and how much of it was heated.
Compared with early diesel engines they were much
easier to construct and more reliable given the
design, materials and manufacturing issues
encountered with the early diesels (that were not
properly resolved for a long time.) Compared with
(true) gas engines they did not need a source of town
gas, natural gas or a gas producer. Compared with
gasoline type (volatile liquid) engines the fuel used
was cheaper and much safer. Also, early spark
ignition systems on these engines were far from
reliable and although it took a while to get a hot bulb
up to temperature, once that was achieved, unless
there was some serious mechanical issue, the engine
would start.
Going back to a comparison with the diesel, one of
the major problems with early diesels was getting a
fine enough spray of fuel to adequately mix with the
air. Diesel and the others developing his engine
resorted to an air blast system but with the high
pressures needed the compressor required
consumed a significant fraction of the engine power.
Hot bulb engines need only a simple pump and
difficult – but I will try in the newsletters that follow.
Our Website
https://sites.google.com/site/bluewatermes/
Last Meeting this Season
June 15th, 2015
injector system to “squirt” the amount of fuel needed
John Lovegrove
SOUTH BRUCE VINTAGE
TRACTOR TOUR
MILDMAY
June-27
http://www.masseycollectors.ca/2014%20-
Tractor%20Tour%20poster%20-%20Best.pdf
ALL COLOUR ANTIQUE
TRACTOR & TOY SHOW
COUNTRY
HERITAGE PARK
July 17,18,19
http://www.tractordata.com/shows/canada/ontario/countryheritage-
park-all-colour-antique-tractor-and-toy-show.html
ONTARIO STEAM &
ANTIQUE PRESERVERS
ASSOC.
MILTON
Sept. 4-7
http://www.steam-era.com
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