1" bore X 7/8" stroke twin launch engine
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     Updated on:
December 30, 2008

2 1/2" gauge carpet engine
Beneath this photo of the cylinder block from a model tugboat engine is a gallery of color photographs of various miniature engines that I have made over the past 17 years.
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twin-cylinder, double acting model marine engine made from castings.
    Keep an eye out for highlighted text that you can click on for more information and larger or additional photos.  Leaving the mouse pointer on top of a picture or button for more than two seconds will sometimes yield abbreviated descriptions or comments,  but these will be brief.

   The pictures presented here have been scanned at 200 dots per inch.  Most were 4 x 6 inch photos,  processed at one-hour supermarket photofinishers.  They have been in my album for years and carried all over the country.  I am amazed by the quality of these images on the computer monitor - it provides the perfect lighting seldom found when viewing the originals.

   Many photographs were taken with a Fujica ST-901 automatic 35mm SLR and a 24mm Pentax lens.  On occasion I used a Pentax Spotmatic manual camera body.  Film ranged from Kodak to K-Mart (Focal).
fifty cents worth of materials
'lots of nice copper !
Model four-pass firetube boiler
miniature steam generating plant
end view of engine and boiler
There was a wasp's nest under the real one
1890 T. A. Maclean horizontal engine
This is a Carpet Engine - a model of a model.  These were the toy trains of the mid-Nineteenth century.  They loosely resembled the locomotives of the day and were constructed entirely of brass. This one is called the Birmingham Dribbler.  It  was made from a package of castings and materials that I purchased from Maxwell Hemmens in Thorganby, England.  Mr. Hemmens told me that they were dubbed "dribblers" or "piddlers" because of the wet trails left behind as they lumbered across the living room carpet under steam.
A model mill engine steam plant with dynamo
This engine was made from  a set
of Stuart Turner S50 castings. The
flywheel is 3 3/4 inches in diameter.

    5/8" bore           1 1/4" stroke
The mill engine is coupled to a Cornish boiler fashioned from silver-soldered copper.  It is  2 1/2 inches in diameter and the flue contains 16 Galloway tubes.  The riveted exterior is only a decorative cover not attached to the pressure vessel.
There are six miniature lamps on the model, as well as a working voltmeter and pilot light. The control panel houses a voltage regulator to supply a precise 3-volt output.  The plant is capable of powering a radio at room filling volume at a fairly slow shaft speed.
Here's an alcohol - powered engine that was made from a few pennies worth of leftover materials from my workshop.  It's an experimental unit I made to test my skill on several  machining operations and to try a homemade threading attachment on the Taig micro lathe.

The displacement is approximately .05 cu. in. and the base is about two inches square.

The throttle return spring is actually the fuel line.  It is made from silicone rubber and just pushed on with a little bit of a counterclockwise twist.....it works like a charm!

No,  I didn't make the glow plug,  I bought it at the corner hobby shop.
  A four-pass unit modeled after a present-day prototype:             Cleaver-Brooks CBH 70
Here is a model boiler in the making.
   I was fortunate in having a good friend who was installing a real one of these units in his family's laundry business.  I was able to get dimensions and other important information from him at the end of each day over lots of cups of coffee and tea !
                        Many thanks Bruce !
The boiler is three-inches in diameter and designed to operate at 50 P.S.I.   The prototype is fired with oil,  but I chose to burn Propane in the model.
Here is the finished              model boiler
  Below is a GRASSHOPPER ENGINE.  The original design of using a swinging link to achieve straight line motion in the piston rod is usually credited to Oliver Evans.  My model was made from odds and ends and operates quite smartly at a steam pressure of only four pounds per square inch.
    The engine itself is about five inches long and the boiler is one and three-quarters inches in diameter.  This was an early project for me,  constructed before I bought my first lathe. Any turning was done in the chuck of a hand drill with a file       .....not a practice I recommend!

    That's my Dad standing there - he passed away in 1993.  He was always interested in planes, boats and engines.
                   THE AEOLIPILE

   Actually a steam reaction turbine,  the Aeolipile was invented by Heron of Alexandria in the first century A.D.  It was described in detail in his book Pneumatica.

   A fire beneath the cauldron boils water, producing steam which is conducted through one of the copper elbows to the pivoted brass sphere.  This steam issues from nozzles at the ends of the two small opposing arms on the sphere causing it to spin.

   This little replica spins practically silently at 1500 RPM with a steam pressure of only 1.8 pounds per square inch.
Miniature Gasoline Blowtorch
for dropping in,    and come again!
   Seated on a wooden platform to allow clearance under the five-inch flywheels,  this replica has been fabricated in one-twelfth scale.  No castings were used in the construction of this model.  All the parts (including the flywheels) were made from flat metal sheets and bars,  silver-soldered together. Much of the finish work was done by hand with a file and sandpaper.

   The engine was constructed from photographs,  measurements and drawings which I made in the summer of 1996 from the original antique engine.

    Practically completed,  this miniature steam engine is designed to be operated on  60 - 75 P.S.I. at 100 RPM.

The prototype of this steam sawmill engine was designed and built in my hometown circa 1890.
       It now stands at the entrance to the home of a well-respected antique engine collector. 

In this front view of the same engine you will notice the boiler in the background with the adjustable-weight,  lever- type safety valve on top of the steam dome.

If you look closely, you can see the difference between the two pulleys:  the left one has a wider rim,  while the other is out farther from the crankshaft bearing to accommodate the excentric and governor belt pulley.  In practice the larger wheel was used for the main drive,  and the smaller one for the auxiliaries. 
   Here is a view of the boiler front.  It is a wood-burning HRT (horizontal return tube) unit three inches in diameter.  Heat from burning tiny Manitoba Maple "logs" on a stainless steel grate first heats the bottom of the boiler shell, then passes through fifteen flue tubes toward the front,  boiling the water.  An induced draft from a steam blower in the smokestack keeps the fire burning fiercely.

Note: These shots were taken prior to much of the pipefitting that went into the final  plant.
This back view shows the angled blowdown valve and spring safety valve (top at back). This photograph was also taken before the boiler installation.  The boiler shell is eight inches in length.

  This is a scale model of a 5 hp gasoline marine motor.  For many years,  Bruce Stewart & Co.  produced these and a variety of smaller and larger engines.  In the first half of the 20th century a great number of small foundries were producing machines of this type.  These  two-stroke engines were used in the small boats of the inshore fishery on the Atlantic Coast.
    The little motor presented in these two photos is about the size of a baseball and was entirely fabricated without the use of castings.  Early Imperials like this one used a standard "jump-spark" ignition,  later going to the more waterproof  "make-and-break" system.

    This  model sports a working water pump for cooling and a homemade spark plug.  For purposes of display,  I purchased the unfinished propeller casting from James Bliss Marine in Boston.
  Friends dropped by one evening with a carton of old Popular Science magazines from a flea market they thought I might enjoy.  The February 1950 issue provided the plans for this little gem.

    It's a vacuum or atmospheric engine.  It burns alcohol, makes a nice plopping sound, cost almost nothing to make and I can shut it down by blowing out the flame. 

....There's enough things to construct in those old magazines to do me a lifetime!
A working ornament,  this little steam plant has a three-flue dryback Scotch marine boiler, coupled to a single-acting oscillating engine.  There is a throttle and a forty-p.s.i. safety valve.  The boiler is copper and  the rest is brass and stainless steel.  It rests on a four- inch square block of American walnut.
    The dome on the right is a two-inch-high hydraulic ram or impulse pump (it is no relation to those long cylinder-piston assemblies full of oil now using the same name).

    These units can pump a small quantity of water higher than their own supply using only gravity to provide the work.

    The black PVC parts are only to display it as a working model and not existent in the prototypes.  The discharge pipe can be connected to either the brass nipple at the bottom front or the top of the air chamber as seen here.
    A work in progress.  I am attempting here to couple a Stuart 10V steam engine to a model of a Scott Patent Steam Generator, considered to be the first example of a flash steam or monotube boiler.
     Extremely powerful for its size and weight,  a flash boiler is not expensive to make and is said to be safer than an equivalent drum-type of boiler.

     The actual steam-generating part of this one is inside the conical stainless steel shroud just above the black firebox.  The middle copper section contains a small vessel to dry the steam.  The stack,  of course,  is empty.

     I haven't perfected a firing method yet,  but at times during testing,  I have seen that old engine go faster than ever before !
A miniature gasoline blowtorch  - overall height 3 inches
A tiny replica of a Butler 100.  The tank on this torch was hollowed out from solid brass stock.  It has a working air pump and vaporizing burner to produce a loud & hot short blue flame.  I turned the handle for this one from the trunk of an unfortunate Flowering Crab in our back yard.

   While the electric elevator of the time was considered "simple and cheap" to install,
elevators were "intrinsically safe, reliable,  smooth-acting and under perfect control."  These words from  The International Textbook Company  in 1902.  In Britain they were referred to as "hydraulic suspension lifts, and the system of wire ropes and pulleys was termed a "jigger."  This kind of elevator is still produced today and marketed here as a "roped holeless hydraulic elevator" (however, the steam pump is replaced by an electric one).  The best type of hydraulic elevators were said to be the vertical tension elevators,  the type chosen for this 1/24 size replica.

    Like the originals,  I selected water as the hydraulic medium.  A steam-powered water pump provides the pressure to operate the system.  Steam for the pump is produced by an alcohol-fired boiler of the Babcock-Wilcox pattern with a 70-tube economizer.

   The photos were taken prior to the threading of the ropes.  Only a single line was attached at this point.  It is too bad.......quadruple lines through all the pulleys make quite a sight!

Economizer with ladder attached
Shaft pit with car and cables removed
The boiler and water tubes are suspended by straps from an "exoskeleton-type" I-beam framework,  barely visible in the background of these two photographs.
   This marine steam plant uses a twin launch engine made from castings and fitted with a Stephenson Link reverse gear. 

    Powered by a kerosene-fired Yarrow-type boiler,  it has two heated stainless steel tanks which together hold a half gallon of water.

    The copper boiler has sixty-six watertubes heated by six kerosene wick lamp burners with induced draft. They are are ganged in two banks of three for easy pushrod use with future radio control.  The double-walled boiler shroud is entirely made of stainless steel. 

    In addition,  there is a feedwater heater,  economizer, superheater, stack dampers, displacement lubricator, stop and throttle valves, manual and engine-driven feed pumps with filter, steam blower, whistle, exhaust steam separator, automatic regulator and safety valve, steam pressure gauge,  water level gauge and a stack temperature gauge.

Bore & Stroke: 1" x 7/8"     Wt:  28 lbs (wet)
To see the all-aluminum tugboat under construction  -  CLICK HERE

     Six of these guard our city from attack by sea.  As far as I know,  on the only occasion we could have used them,  we threw up our hands and gave all our riches, and the Town Seal, to privateers.

     In more recent times a procession of cruise ships comes from over the horizon and now the flow of Gold is most happily reversed !
      I made this tiny replica for my friend Gordon who was kind enough to lend me his digital camera to get some missing shots I needed for this page.

A fifty-five-pound model of the nuclear attack submarine Thresher.      Length:  60 inches
I won't forget hearing those first sketchy reports of the loss of the Thresher       over WKBW radio in Buffalo.  All hands were lost on April 10, 1963.
You can sever a wooden clothespin in half a second with this saw.  I designed it to use an abrasive cut-off wheel to cut that very thin brass tubing and channel stock they sell in the hobby shops.

The performance really shines with a woodcutting blade installed. The cuts are extremely fast and clean.  It would be a great tool for building model boats.

The green metal base contains nickel cadmium cells to supply electricity to the motor,  making it cordless.  The motor is no wimp...in its former life it powered a cordless grass string trimmer.
Model Builder's 3-inch Sliding Compound Miter Saw
                        LARRY' S LAMP

    This four-inch high lamp was constructed from an old engraving in an encyclopedia.  The shade is copper and brass, the body is brass and the base is aluminum.  The glass chimney functions well,  noticeably increasing the whiteness of the flame.  It will run for a considerable time from the kerosene contained within the urn-shaped reservoir.

    I made it as a Christmas gift for Larry, our good friend who has provided me with wise counsel and support on numerous occasions over the years.

    The lamp is pictured here burning on top of a volume from the Encyclopedia Britannica.

This little project was an early one for me.  The spindle turns in ball bearings and the headstock can be swiveled to allow it to be used as a grinder.  It was made from aluminum and stainless steel.  It is powered by a small 6-volt motor  coupled to a three-speed pulley system.  The capacity is a one-inch swing and the distance between centers is about two-and-a-half inches. It is a semi-scale model of the well-known Austrian Unimat SL. 
(c) John R. Bentley 2001- 2008.
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