Ref mssg 178, Dyno, Loco Engine
- Malcolm and others; Sorry for the delayed response--maybe the Holidays
have kept us busy, maybe most of us don't have an exact answer . . .nor do I,
but I don't mind putting a foot wrong, so to speak, to get a correspondence
The short answers are no and yes.
Nobody knows with any exactness how much power their model engines
develop. (If anyone has comparative figures, please respond.) Most folks are
happy to get their engines running and start another project. EXCEPTION:
There is a report that Westbury and Prof.D H Chaddock tested the Kiwi (15cc).
"The engine produced about 0.4 hp@6000 rpm and about 0.64 hp at 8000
rpm." See the article about Kiwi at Phil Colemans site,
A dynamometer has to be built with the capacity and range of measurement
suitable to the engines it will measure. As I understand it, the accuracy will fall
off at either end of the scale. Small dynos have been made and tried on
model engines. The results are comparable in house but not extandable to
other shops. I mean that engine to engine comparisons are accurate as far as
which engine is stronger on a given day, in its current state of tune; but a
readout in exact horsepower and torque is not available. What standard
would be used to calibrate the scale ? Would the same calibration have been
used in Calif., Ohio and Florida ?; in South Africa, Australia and London ?
In this sense the aero engine people have an advantage. They can put their
engine on a bench mount and try it with various propellors (which have
standard working dimensions) and thus report what pitch and diameter the
engine will swing at what rpm, and these results are reliable. They do not
however, give fractional horsepower and torque, though sometimes these
figures are inferred by numerical extrapolation. For an extended discussion of
methods and results of small dynomometers try
<http://www.foxvalleykart.com/dyno1.html> . .(the first of six parts).
Also, Robert Washburn collaborated with Bud Kirk in getting a model size
dynamometer designed and published in Strictly Internal Combustion
magazine- - -back issues still available- - -see at
<http://www.strictlyIC.com/pit01.html> "Kirk Miniature Dynamometer" in eight
Extended operation of miniature engines is less a cooling problem than you
might expect. Some engines run all day at model exhibitions. In the enclosed
loco body you can use a water cooled engine with a small radiator. Adding
the load of doing actual work may need excess cooling and a thermostat. Cut
and try. But you may want to have engine temp gauges during development.
Putting some chalk on the shed wall . . . .
What locomotive do you want to model? (Is the scale 1/12 ?) As I think about
this, you want to replicate the external appearance, but the internal volume is
available to re-engineer at will. For example, I am interested in modelling the
Fairbanks-Morse 20-44, which is in a museum about sixty miles away. This
may be one of the taller road-switchers; the hood runs full height for most of
the body. At 1/8 size the model would be 76.5 inchs long, 21.75" tall and
15.75" wide for 7 1/2" track. I can almost visualize a 750cc Crosley block filling
that long hood; but realistically the engine auxiliaries would double the
volume. So take a long look at the enclosed volume and divide by three: 1/3
engine block, 1/3 stuff to keep the engine running, 1/3 drive system. I'm
thinking a Dynastart system, (starter and generator in one housing) then
electric drive motors in each truck. The trucks should have a realistic look.
Most locomotive hods are rectangular shapes; wouldn't inline engines adapt
There are two engines designed for use in scale locomotives on the Internet:
E T Westburys "1831" (as "Wallaby") and Roy Amsburys V8. Westburys 1831
was intended for use in a model of the first diesel in a locomotive by any
British railway, the LMS1831, a short coupled 0-6-0 converted from steam. It
had hydraulic drive. ETW arranged a variable ratio friction drive for the model
similar to th one used in the Roadroller (Aveling DX) and a centrifugal clutch.
Later a hydrostatic drive, consisting of two oil pumps in series where one
controls the volume/speed and the other does forward/neutral/reverse was
published and is online at Yahoo group mlprojects4, file #2902.
But this was a small model and scaled for 3 1/2 in track, so the engine is
small, a 30cc inline twin-cylinder, water cooled. In fact on page two of the
Wallaby article he states "I may mention that the choice of a twin-cylinder
engine for the 1831 was determined by the installation space". ((Plans for this
are available from Argus Specialist Publications; or in North America from
Sulphur Springs, see listing at
<http://www.sssmodels.com/booksvidsdwgs/booksvidsdwgs.html> or in
Australia try <www.ploughbooksales.com.au/22.htm> as #008725-Wallaby
and #008727 carburettor plans.)) As far as I know the "1831" and the
"Wallaby" are identical (except that the 1831 was cast gunmetal and th
Wallaby cast aluminium). There may be detail differences- - -perhaps one of
our members will know. You would want something larger for the five inch
railway. But how much ? A 50cc engine in a motorbike can propel a
teenager outside the envelope of safety. But train hauling is probably more a
matter of torque, a steady pull rather than an accelerative zing.
Roy Amsburys V8 engine was specifically designed for a 5" gauge "Hymek"
diesel. It is an attractive design with a very nice five gear drive to camshaft, oil
pump,fuel pump and distributor and water pump. But it is seven inchs wide
(and eight inchs long).At 120cc, I think it is too big. At 7.3 cu.in. we can
guesstimate the output betw 3 1/2 to 7 horsepower. It is not built for torque, but
more for performance; the bore and stroke nearly equal (1.08"by 1.05" est.);
the conrods less than 2x the stroke; analogous to a Chevy V8. If you complete
this engine by the method described you will have earned a medal in brazing
with special stripe for miniature work. ((Online archive of seven parts,
runnning to twenty pages, well illustrated, at
The Wallaby articles are also at this site; Kiwi and Wallaby are also at Yahoo
group mlprojects files))
But I think 120cc is too big.(Again, anyone who has experience in this area,
please reply - - have you seen the Hymek model run ? )
Still, the long rectangular hoods common to most diesel locomotives seem
better adapted (or amenable?) to inline engines. A 50cc engine might be
enough---striking an average between 50 and 120 gets about 85cc. The Seal
and Sealion are both good engines; can they be expanded to five cubic
inches ? Well, first, lets add two cylinders, as Nissan did with their 1600 and
2400 family of engines. This SeaLion inline six would be about 44cc.
Expanding to 1 inch cylinders (used on several ETW designs) and a stroke of
1.104 in. makes 5.2 cu.in.. But the Wallaby has a stroke of 1.125, listed as 29
or 30cc.; six of the Wallaby cylinders (three blocks of two) would be 87 or
90cc. (TLAR!) with the connecting rods and other elements all sized to work
together according to the wisdom and experience of E T Westbury. Except
that Westbury never drew- - well, never published- - a six cylinder. One could
mount the cylinder blocks on a unifying crankcase, over a stretched six
cylinder crankshaft. (Would have to rework the cylinder heads so the exhaust
comes out opp the intakes; and only need one distributor, one left end, one
right end, larger oil pump etc. Might be 7"tall, 4"wide and 12.5"long.)
Well, thats my recommendation, to open discussion on the topic "What engine
would be practical for a model gas-electric locomotive ?" Inline six cylinder,
90cc , maybe three to five horsepower, Dynastart (or a starter and alternator),
electric motors in the trucks, fuel and oil tanks, moto battery, and radiators for
cooling - - - Its like building a small car from scratch.
Richard (in San Diego)
Now that is what I might call a "considered response" and WELL worth
the wait - THANKYOU!
I think I agree with all you say and a SealSix sounds like a fine
I had forgotten that Roy's V8 was designed for the Hymec, I now
recall reading the articles in the ME when they came out - I'll
search them out from my library...
I found the articles on the 1831 in the club's library, but there was
a lot of "guessing" in the sizing, and I have never seen a finished
one running and its only 3.5inch so I had some level of
I am planning on modeling at 1/12th scale (or maybe a narrow guage
prototype at a larger scale) so as you say there should be enough
room for the straight 6.
My thinking was that we know from the Steam Efficiency Trials that
the most powerfull 5inch steam loco's are producing about 1.0 draw-
bar horsepower. So it would seem that an IC engine producing about
that figure should be OK - as if we assume a 50% efficiency in the
generator/control/motor department we would still have about half a
horse power on the draw bar.
Given that you don't want to thrash the poor thing, and it would be
good to sustain extended patches of pulling joe public at the
society's track, you might want about 2 to perhaps 3 HP available in
an "ideal world".
This tallies with the Briggs&Straton sidevalve engine which powers
our existing diesel/hydraulic being about 3.5HP (from memory) and
this works quite well...
So all this suggests to me that the 50cc to 80cc range feels right.
Now please be aware that all this is "future planning" as I am still
finishing the 5inch 2-8-0 I am building (which it'self got stalled
while I build a Proff. CHaddock Quorn Cutter/Grinder to resharpen the
tooling after finishing the motion (rods etc.) for the loco! -
However it feels to me like a cam-griner in the making!)
So thanks for the input - I think I will go order a set of Drawings
for Seal to pin on the wall and "consider" while I finish the steamer!
THanks again ....
Medstead, Hampshire, UK
--- In ETWestburyEngines@yahoogroups.com, "sicreader" <obadevi@s...>
> Malcolm and others; Sorry for the delayed response--maybe the