Performance Description of the Trammel Engine
The Trammel Engine is an internal combustion (IC) engine based on a well known motion mechanism, called a Trammel mechanism or an ellipsograph, which serves the function of coupling a linear oscillating motion to a rotational motion. In the traditional piston engine this function is performed by the crankshaft, connecting rod and piston (gudgeon) pin.
It can be easily proven that if the output of the Trammel engine has a constant angular velocity the piston pairs performs a true sinusoidal motion, equivalent of a traditional piston engine with an infinitely long connecting rod. It can also be easily proven that under the same circumstances the center of mass of the piston pairs (and the linkage) performs a steady circular motion, thus being simple to balance fully.
The challenge, in taking advantage of this mechanism in an engine with significant power, is to design an appropriate linkage. Three problems in particular seem to have held back such a design, namely connecting the rotational output from the front and back of the engine, the number of components needed to mechanically actuate the overhead valves and eliminating the inherent piston to cylinder side-loads, that the combustion pressure would generate. That there would be large side-loads can be visualized from fig.1 by fixing the center point of the linkage in space, applying a downward force to the top piston and realizing that the rotation of the linkage would result in a push of the vertical piston pair to the right and push of the horizontal piston pair upwards.
Fig.1 shows a conceptual drawing of the Trammel engine consisting of two perpendicular rigid piston pairs, connected through the outer pivot points of a clockwise rotating linkage having also a center pivot point performing a counter-clockwise circular orbit and through which a rotational output can be captured.
absence of the impacts of rocking pistons, there is the potential of applying
brittle ceramic coating (thermal and anti friction) on the cylinder walls
improving the efficiency.
lack of friction between pistons and cylinders (friction between piston rings
and cylinders is unchanged), which now is captured in a planetary gear, has a
surprisingly large effect on the internal friction. The resulting fuel savings
compared to a comparable 4-cylinder engine has been calculated
and is shown in the figure below, which also can be interpreted as relative
torque increase. Averaged over the working range for typical automotive use this
corresponds to a fuel saving (or torque increase) of about 15%.
Fig.2 shows the calculated fuel saving of the Trammel engine relative to a similar 4-cylinder engine. High RPM and low load provides the most benefit.
cost mechanism overcoming the problems described previously has been designed
and is patented (see references). A theory for the main internal forces has been
developed and is documented in a compendium and in the patent. The first
iteration is manufactured and has been successfully powered externally. The
mechanical drawings for the second iteration of the basic engine are in the
process of being done and a SAE
paper on the subject has
been written and was presented at Future of Transportation Technology (FTT)
conference in Costa Mesa CA 1999.
As can be seen from figure 1, a 4-cylinder configuration of the engine is the most natural, but others can be easily envisioned, such as 8-cylinders consisting of two "stacks" of 4-cylinders and down to two cylinders, accomplished by reducing each piston pair to a piston plus a guided counterweight, pump or the like, ensuring the center of mass is at the outer pivot point of the linkage (center of piston journal bearing).
In order to make the prototypes better than the best of near future traditional engines, some key components are necessary, namely an electronically controlled valve mechanism and comprehensive engine management hardware and software. Furthermore recent technological trends suggest the flywheel, alternator and starter can be substituted by an integrated starter-alternator-damper ISAD at the location of the traditional flywheel.
Trammel mechanism has among other the following advantages relative to the
traditional piston-connecting rod-crankshaft design:
Is fully balanced (no higher harmonics resulting in
less noise and vibration) and is in this respect equal to the Wankel engine.
Has less reciprocating mass, resulting in a potential
for running up to 15000 RPM
Has no piston to cylinder friction and a true
sinusoidal motion, thus providing smoother torque.
Has at least 30% fewer bearings for a 4-cylinder
configuration, again resulting in higher efficiency especially at higher
Has a much shorter (higher stiffness/mass)
crankshaft, resulting in a higher Power/mass ratio.
Is spatially more compact, resulting in a higher
Provides possibility for load dependent compression
ratio, again resulting in improved efficiency especially at part load.
to the Wankel engine the following advantages are obtained:
Better combustion chamber sealing (a circle has the
shortest possible periphery, i.e. shortest seal per displacement), resulting
in higher efficiency especially at lower RPM and lower oil consumption
Traditional piston seals can be used directly
Has better shaped combustion chambers, leading to in
less unburned HC and higher efficiency*.
10-30% improved fuel economy
20-25% improved combined emissions
10-15% improved torque for 800-6000 RPM and much
better beyond this range
80-100% improved available horse power
cylinder enable/disable for further operating economy
(software programmable 2-, 4- and 6-stroke)
no need for a separate throttle (reduced complexity)
valve timing programmability leading to easy
adaptation of multi-fuel use
individual cylinder control with potential for
compensation for uneven manifold flow pattern and difference in wear between
provides possibility for combustion starter,
eliminating need for starter-motor, potential for elimination of reverse
More available momentary torque (and possibly power),
when the ISAD‚
system is used in power-boost mode
Is spatially more compact, resulting in a higher
power/volume and power/weight ratio
Much better noise-vibration-harshness NVH
accomplished by electronically controlled torsional damping, no starter
noise and no alternator belt oscillation
Ability to run cylinder cut-off by compensating or
the increased torsional vibration
20-35% improved fuel economy accomplished through
automatic stop-start and cylinder cut-off
Fig.3 is a graphical representation of the expected improvement provided by the Trammel engine, using the best contemporary ICSI engine as a baseline (Std+EM-valve means standard engine with computer controlled electromagnetic valves).
In summary, the Trammel engine can be expected to be better than both future traditional piston and Wankel engines. More specifically better most and equal some of the critical design parameters for automotive IC engines such as low brake specific fuel consumption (bsfc), emission (HC, CO, NOx), NVH, high power density, broad-bandedness (wide RPM range) and expected low manufacturing cost, serviceability, durability, long service intervals and clean uncluttered appearance.
Recently Honda has shown natural gas vehicle based on a 1.6 liter gasoline engine with only few internal modification accomplishing 1/10th of ULEV emission. The Trammel engine is no more difficult to convert to natural gas.
I have now entered into a collaboration with Ginler Technologies who in parallel pursued the Trammel engine and simultaneous with the issuance of my patent arrived a the same idea of offloading the piston cylinder forces through a planetary gear. Their approach was to use an external shaft to index the front and back of the engine components. Patent number 5,189,994 and 6,006,619 captures their ideas.
expected that the engine needs three design iterations, at a duration of one
year each, before a commercially attractive prototype will materialize.
Internal Combustion Engine in Theory and Practice", C.F. Taylor, MIT Press,
"Cruciform Engine", P. Gibbons, Costa Mesa, CA, Patent # 4,850,313, July 25, 1989.
"Electronic Valve Timing", L.A. Gould, W.E. Richeson and F.L. Erickson, Philips Industrial Electronics Company. Automotive Engineering, April 1991.
"Electro-magnetically Actuated Valve", F. B. Morinigo and K.O. Stuart, Aura Systems, El Segundo, CA, Patent # 5,222,714, June 29, 1993.
"Electro-magnetically Valve Actuator Drives Variable Valvetrain", M. Gottschalk. Design News, Nov.1993.
"Camless Engine", M.M. Schecter and M.B. Levin. SAE Technical Paper # 960581, Feb. 26-29, 1996.
"ISAD‚ A Computer Controlled Starter-Alternator-damper-System", Klaus-Peter Zeyen and Thomas Pels. SAE Technical Paper # 972660, Aug. 6-8, 1997.
"The Integrated Starter Alternator Damper: The First Step Toward Hybrid Electric Vehicles", C. Peter Cho - Delco Remy America Inc. William B. Wylam - Delco Remy America Inc. SAE Technical Paper # 2000-01-1571, Future Car Congress, April 2000.
"Near-Zero Emission Natural Gas Vehicle, Honda Civic GX", Toshiuki Suga, Ben Knight and Sakuji Arai. SAE Technical Paper # 972643, Aug. 6-8, 1997.
"Soft Landing Electro-magnetically Actuated Engine Valve", R.E.Diel et Al., Ford Global Technologies, Patent # 5,730,091, March 24, 1998.
"Internal Combustion Engine Equipped with Electromagnetic Valve Driving Apparatus and Head Structure Thereof", T.Izuo, Toyota Japan, Patent # 5,720,242, February 24, 1998.
"Internal Combustion Engine", L.Pedersen, Patent # 5,782,213, July 21, 1998.
"Trammel Engine Crank Mechanism", L.G.Pedersen, SAE Technical Paper # 2000-01-3073 SP-1559.
informative and entertaining web-addresses:
|Model of a trammel engine in its natural 4-cylinder configuration, taking up very little space.|
|Wooden model of a trammel engine crank mechanism and piston pairs as well as in the 2-cylinder boxer configuration. The two cylinders can also be configured as a V and even a perfectly balanced 3-cylinder configuration can be made.|
|Manufacturing area for the first Trammel engine in the world. CNC controlled mill/lathe in my garage.|
|Aluminum and steel components for the first design iteration.|
|Internal components of Trammel engine set up for balancing.|
|First iteration of the Trammel engine (without valve actuation) being externally powered by an electric motor.|
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