Using Elliptical trammel for opposed cylinder engine

  • Context: Automotive 
  • Thread starter Thread starter The tin man
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    Mechanical design
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Discussion Overview

The discussion explores the feasibility of using an elliptical trammel design for an opposed combustion engine configuration, specifically with two vertical and two horizontal cylinders. Participants consider the implications of such a design on engine performance and mechanics.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • One participant questions why an elliptical trammel has not been used in opposed combustion engines, suggesting it could function similarly if pressure is fed in a loop.
  • Another participant acknowledges the possibility of using an elliptical trammel but cites potential bearing lubrication issues due to high surface velocity as a reason for its lack of implementation.
  • Concerns are raised about balancing the assembly at high speeds, with suggestions that offset cylinders or multiple trammels might be necessary for balance.
  • A comparison is made to radial engines, noting that the proposed design could resemble a radial engine with fewer pins needed for operation.
  • It is mentioned that a four-piston engine would likely require a two-stroke design without a closely coupled flywheel, as four-stroke radial engines typically need an odd number of cylinders, usually more than six.

Areas of Agreement / Disagreement

Participants express differing views on the practicality and challenges of the elliptical trammel design, indicating that multiple competing perspectives remain without a clear consensus.

Contextual Notes

Participants note potential limitations such as lubrication challenges, balancing issues at high speeds, and the design requirements for two-stroke versus four-stroke configurations, which remain unresolved.

The tin man
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Question I'm sure theirs a reason this hasn't been done but why couldn't you use an elliptical trammel as a design for an opposed combustion engine where 2 cylinders are vertical and 2 horizontal and have the cylinders combust in separate loops wouldn't that technically do the same thing in principle as long as the pressure fed in a loop
 
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Welcome to PF.
You could use an elliptical trammel in a four piston engine.

The reason it is not done is probably because of bearing lubrication problems, due to high surface velocity.

The engine would be more compact if it was built as a flat boxer, with a quadrature crankshaft for the two journals.

Maybe a diagram of your idea would help find references to that style of engine.
 
I think balancing the assembly at high speed might be difficult as the two cylinders would need to be offset (and the crankshaft as well). Or you would need multiple two-cylinder trammels to balance each other?

Otherwise, it would look a lot like a radial engine with fewer pins needed. In the following animation, the link with the 5 pins would be the rod between the two pistons; The middle of that rod being connected to the crank pin.

800px-Radial_engine_timing.gif

(original animated GIF)
I also found this but I have no clue what the engine looks like.
 
Last edited:
Without a closely coupled flywheel, the four piston engine would need to be of two-stroke design.

Four-stroke radial engines need an odd number of cylinders, usually greater than six.
 

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