By Staff
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Two sides of George Fair's home-built 'Otto-Volks,' so named for its use of Volkswagen engine parts, in particular the VW-sourced cylinder head and cylinders.
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Clearly visible here is the VW brake drum that defines the end of the combustion chamber, the blower motor that supercharges the cylinder and the VW-sourced fuel injector.
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A simple bungee cord keeps the connecting rod in check.
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George Fair and the Otto-Volks. The completed engine is an impressive project by any measure, made even more so by its extensive use of salvaged parts.

I had just finished my ‘VBS Engine’ (see GEM, June 2001)
and was looking for another engine project, but it had to be an
unusual engine. The Otto-Langen atmospheric engine of 1864 had
always interested me, but I had never seen one.

Wayne Grenning’s Web site (http://members., had a revised edition
of his February 1991 Gas Engine Magazine article, which was my main
source of information on this early engine.

The Otto-Langen engine was the first internal combustion engine
to go into production, and from 1864 to 1876 about 4,000 engines
were built using a free piston design. The power of these early
giants was low and the engines were big: A 2 HP engine weighed
about two tons. Low horsepower seemed great for a home-built
engine, so I put Nicolaus Otto’s design on a diet and introduce
some new engine components.

My home-built engine wasn’t going to be a scale model (Wayne
Grenning already offers excellent Otto-Langen models), just a
home-built engine put together with junk. I didn’t bother to
make formal drawings or even a sketch, as that might have
restricted me since my intention was to use available parts and
materials in building this engine. The only power tools used on
this project were a drill press, belt sander and 3/8-inch electric
drill. Mo welding, lathe turning or milling was required.

Sourcing Parts

The engine is mounted to a discarded lawn mower frame turned
upside down.

My first stop for parts was R&S Performance in Orlando, Fla.
Scooter and Big Daddy, the moving forces behind R&S, make a
living by repairing and maintaining air-cooled Volkswagens (VW) but
live to build and drag-race Volkswagen-powered cars. My initial
shopping list was a later model VW, 1,600 cc dual-port head and
cylinder, which were easy to find in their scrap pile. I cut the
head in half, modified the valve spring retainers to operate with
very weak springs and made a progressive rocker arm assembly, using
two door hinges to sequentially open the valves using one push rod
(actually, my inverted engine uses a ‘pull rod,’ not a push
rod). A small piece of foam rubber saturated with oil and wrapped
around the valve stems provides lubrication. I wasn’t sure how
big the combustion chamber should be for this low-efficiency
engine, so I extended the 85.5 mm cylinder with a 90.5 mm cylinder.
I drove the two cylinders together, skirt-to-skirt (a VW cylinder
has a protruding skirt that mates to the engine case), and sealed
the surface between the two cylinders with a copper head gasket and
flat gasket material cemented between the two cylinders. I was
beginning to realize that each step of this home-built engine would
be a ‘science project,’ and workable solutions would have
to be determined before proceeding to the next issue.

A scrap VW bus brake drum was selected to terminate the
combustion chamber and translate it to a 1-1/4-inch pipe fitting.
The outside face of the VW brake drum is turned flat, providing an
easy seal for the 90.5 mm cylinder to brake drum interface. There
are holes drilled through the brake drum, and threaded rod running
through the VW head, the two cylinders and the brake drum bolts
them all together.

As this engine was going to be big, some type of frame was going
to be necessary to mount up this odd accumulation of junk. An
original 2 HP Otto-Langen was about 10 feet high, and just the head
and combustion chamber on my home-built engine was 20 inches tall.
The ‘Curbside Parts Supply’ (trash piles) had a nice
chrome-plated clothing display rack that 1 used for part of the
engine frame. Some steel angle iron salvaged from old bed frames
made for a sturdy fixture between the brake drum and the clothing
frame, with holes drilled in the brake drum securing it to the
angle iron. The VW cylinders and head are suspended from the brake

My initial idea for a carburetor was to bubble air through a
glass jar filled with gasoline, but the more I thought about this
idea the more I wanted to incorporate safety features to prevent
any possible fire or explosion. Scooter suggested using a fuel
injector, and at first I thought this sounded too high tech. I took
his advice, however, especially since he also offered an intake
manifold with injectors from a Type Ill Volkswagen. The fuel
injector would require pressurized gasoline, so I converted a
compressed air dryer housing into a pressurized fuel tank. My
engine has no intake stroke to suck the gas and air mixture into
the cylinder, so I mounted a small blower on the intake manifold.
Talk about high tech, this 1864 design was now becoming a
supercharged, fuel-injected beast. The ‘blower,’ by the
way, is a 12-volt raft inflator, and at $5.49 the single most
expensive part I bought for this engine.

Slow-running engines attract attention at engine shows, and I
decided that firing the engine every 12 seconds was a good starting
point for a slow engine. The ‘Curbside Parts Supply’
provided a 5 rpm rotisserie motor from an outdoor grill. I mounted
the rotisserie motor to the clothing rack engine frame, and on the
motor’s armature I mounted an arm to be connected to the valve
lifters. Also, mounted to the armature is a round aluminum disk
with a scrap of Formica bonded on one side. This functions as a
rotating electrical contact to turn on the blower, fuel injector
and ignition system at the correct time, with three sets of
electrical wipers contacting bare wires that are mounted through
the Formica and grounded to the aluminum disk. I drilled extra
holes in the timing wheel so I can change the timing of these three
electrical functions by moving the grounded jumper wire

‘I still hadn ‘t worked out the details for my cylinder
and piston, but I needed to see some action just to keep my
interest in this never-ending engine project.’

The basic design of this free piston engine is 138 years old,
but up to this point I hadn’t used any parts that were over 30
years old. Old engine people like to see some old parts used, and
since I wouldn’t want to disappoint anyone I fitted a Ford
Model T ignition coil to fire the spark plug.

I still hadn’t worked out the details for my cylinder and
piston, but I needed to see some action just to keep my interest in
this never-ending engine project. I took some scrap 1-1/4-inch PVC
pipe and used it for a temporary test-cylinder because it is easy
to work with. I put gasoline in the pressurized tank, and using an
old computer power supply I sent 120 volts AC to the rotisserie
motor. I then turned everything on, but nothing happened. Twelve
seconds later the engine was ready to fire again, and just as the
Ford coil buzzed I heard a muffled ‘WHOMP’, like you’d
hear lighting a gas stove. I wadded up a ‘shop rag’ and
jammed it in the open 1-1/4-inch PVC cylinder just in time for the
next firing sequence. BANG! My shop rag blew about 20 feet in the
air and was hanging on a limb in my oak tree. I stuffed another
rag. BANG! Another shop rag was hanging in the tree. I quickly
disconnected the power and begin to look for a long pole to get my
shop rags down from the oak tree. I live in a city with neighbors
all around, and my ‘shop rags’ are old underwear. It’s
one thing to have the neighbors talking about my strange engines,
but underwear still smoking and hanging in the trees may create
more attention than I want.

My next test was to see if the engine had enough power to turn a
flywheel. A piece of 3/4-inch PCV pipe was weighted and vented with
an old valve and rigged up as a piston. The vented ‘test
piston’ cleared the PVC cylinder by about 2 feet with its vent
wide open. I never bothered to completely close the vent for fear
of taking down small airplanes that frequent a nearby airport. I
took the engine apart and drilled and tapped holes in the brake
drum and added copper tubing to vent some of the power from the
combustion chamber. One of these vent lines is tied directly to the
exhaust system, and the other goes through a gate valve and then to
the exhaust system. Adjusting this valve or varying the pressure in
the fuel tank allows me to have some control of the power

This home-built engine would have to fit in the trunk of my
Honda Civic, so I made the flywheel support a bolt-on arrangement
made from a couple of front bicycle forks, some plumbing fittings
and more bed frame angle iron. Loosening some bolts and sliding the
pieces into their proper position allows the flywheel and piston to
be aligned. I had originally planned to use a heavy flywheel about
15 inches in diameter, but I changed my design to save weight and
ease the assembly process. This upper engine subassembly is secured
to the clothing rack with eight bolts, and after initial setup it
requires very little alignment when reassembling.

The connecting rod in the Otto-Langen engine did not pivot on a
wrist pin but was instead rigidly connected to the piston with a
rack gear mounted on one edge of the connecting rod. I had several
ideas on how to do this but settled on a simple idea that relies on
a material that is, pound for pound, stronger than steel: wood!
Nothing fancy, just an old rake handle secured with epoxy in a
piece of thin-wall PVC pipe and with holes drilled every 1/2-inch
to engage a bicycle sprocket. The PVC pipe provides a uniform
surface for laying out the holes to be drilled for the sprocket,
and it also permits an easy translation to 3/4-inch iron pipe
fittings that can take the high temperature of the combustion
chamber during the ignition/combustion (upward piston stroke)
cycle. Elastic shock cord limits the stroke and helps accelerate my
lightweight piston on its downward (power) stroke.

Ten-speed bicycles use a roller clutch that is similar in
function to the one originally designed for the Otto-Langen engine.
And since a bicycle wheel is, in fact, similar to a flywheel, why
reinvent clutches and flywheels when the ‘Curbside Parts
Supply’ always has the best prices in town? I found an 18-speed
bicycle that probably was run over by a car, and after a lot or
work I got the rear wheel straight enough to use. It still has some
wobble, which I like to refer to as character.

‘It’s one thing to have the neighbors talking about my
strange engines, but underwear still smoking and hanging in the
trees may create more attention than I want.’

A local bike shop loaned me the special wrench to dissemble the
free-wheel sprocket cluster, which I then reassembled with two
26-tooth sprockets and one 16-tooth sprocket. The 26-tooth
sprockets restrict the connecting rod and center it so the 16-tooth
sprocket situated between the two will engage in the holes I
drilled in the connecting rod.

A length of bicycle chain secured to the rim of the bicycle
wheel gives it some mass, increasing its turning time by 20
percent. The bicycle wheel flywheel seemed to work so well I
started to consider keeping the PVC cylinder and increasing the
time between ignitions to reduce heat output, perhaps enough to
allow the engine to survive short demonstration runs. I knew the
reduced power would produce a slower running engine, but who needs
power? The wooden connecting rod and PVC cylinder became a
permanent part of this unique, slow running engine, eliminating the
need for any welding and machining on this project.

I initially used a 120-volt AC rotisserie motor and a power
supply from a trashed computer for an external power source, but
now that the engine was showing some promise of actually working I
started converting everything to 12-volt battery power. I had
considered a DC/AC converter to run the rotisserie motor, but 1
found a battery-powered rotisserie motor at the ‘Curbside Parts
Supply.’ This should have been an easy and quick motor
replacement, but the process of incorporating ball bearings and an
improved timing wheel mount turned this phase into still another
never-ending ‘science project.’ After salvaging another
trashed computer I came up with enough parts to make an adjustable
voltage regulator for the rotisserie motor so I could provide
uniformed timing for the air, fuel and ignition systems. More
salvaged components went into another voltage regulator to power up
the raft inflator, or ‘supercharger.’ I felt a good
evacuation and charging of the combustion chamber could be
accomplished at a lower fan speed, which should increase the life
of this motor, my most expensive single part ($5.49). Regulating
the voltage to the rotisserie motor to three volts and the
‘supercharger’ to five volts should make these components
perform uniformly regardless of the voltage of my 12-volt

To control the timing wheel I picked out a motion detector
security light with some problems (small fire) in its power supply
but with all its other functions working okay. I used duct tape
(almost everything I build uses some duct tape somewhere) to
‘blind’ the day/night sensor. I replaced the relay so the
motion detector now turns power to the rotisserie motor off rather
than turning a security light on. A small light bulb wired in
parallel with the Ford buzz coil is mounted in front of the motion
sensor. When power is applied to the Ford coil the spark plug fires
and the light flashes on, which triggers the motion detector to
turn the power to the rotisserie motor off. I relocated the
adjustable time-delay resistor to the control panel where I can
change the time between engine firings by turning a knob.

Making it Portable

The clothing rack engine frame had four legs extending out to
stabilize the rack, but this prevented the engine from fitting in
my Honda Civic. I built a full size mock-up out of wood and
cardboard so I could try every possible way to get the engine in
the car: The mock-up would just barely fit with its legs cut off. I
then added weight to the mock-up to make sure I could get it in out
of the trunk by myself. Cutting the legs off the engine made it
unstable, and 1 needed wheels to make it mobile around the shop. To
get around this I mounted the engine to an old lawn mower deck
turned upside down. Bed frame angle iron and clamps secure the
engine to the mower deck, and the wheels are adjusted to give the
deck about a 1/2-inch of ground clearance. With this
‘low-boy’ cart I can wheel the engine into my garage (after
slipping off the shock cord over-travel assembly) with a 1/4-inch
of clearance. I added leveling screws to the lawn mower deck to
adjust for the uneven ground locations often encountered at engine

How it Works

The sequence of events on this engine can be divided into two
major categories: When the timing wheel (rotisserie motor) is
turning and when the time-delay circuit is active (and the timing
wheel is not turning). The timing wheel turns for 12 seconds,
during which the following events take place: Timing wheel starts
to turn, intake valve starts to open, exhaust valve starts to open,
blower starts, exhaust valve starts to close, fuel injector fires,
exhaust valve closed, intake valve closed, blower stops, ignition
and the timing wheel stops and waits for the electronic
(adjustable) time delay to start the sequence again. The electronic
time delay is adjusted to fire the engine every two minutes, which
keeps the flywheel in continuous motion and allows the PVC cylinder
to cool down so the engine can run all day with a nominal power
stroke of 30 inches. When I first got this engine running I was
using regular gasoline, but since this engine uses so little gas I
switched to lantern fuel as it doesn’t go bad if left in the
tank. Fuel consumption is low: Four ounces of camp lantern fuel is
all I need for eight to 10 hours of continuous running at

‘The Otto-Volks Engine’ is the name I gave this
home-built engine because it is based on Nicolaus Otto’s design
and it uses a lot of VW parts. My engine club, The Florida
Flywheelers, was the first group to see The Otto-Volks engine
running and it attracted attention all day long at their shows.
This whimsical contraption at first glance appears to be just
another attention-getting gadget, but further observation shows
this non-compressing, free-piston engine design with roller clutch
uses several principles introduced by the 1864 Otto-Langen
atmospheric engine. The materials used in my home-built engine are
easy to obtain and can be modified with simple tools. This makes it
a good engine to build if you do not have access to a machine shop
or welding equipment.

Watching the expression on people’s faces when they
recognize familiar parts (such as bicycle, VW or lawn mower parts)
that I have used on my engine is priceless. Especially rewarding is
the reaction from young people when they realize that you can use
parts for purposes other than that for which they were originally
intended. These young minds will soon be in control of our hobby
and our nation, and if we do not expose them to how things were
done in the past, and how to improvise, how can we expect them to
make good decisions in the future?

Contact engine enthusiast George Fair at: 118 N. Glenwood Ave.,
Orlando FL 32803, (407) 894-8796, or e-mail:

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