Longboy's "SILO" Model Engine!

[Longboy]

What are the bore and stroke of this engine? I'm asking since I'm building a small database with the typical dimensionss of varois (odd) model IC engines. This to get an idea on how far one can stretch physics.

Thanks Xander. A one inch bore and stroke for The SILO engine. I would say that physics remain the same regardless of bore and stroke for running reciprocating engines at different scales. You may be more in concern for rod length and angles rather than B.& S. sizes for the physical limitations. In that case the stroke either confirms / denies an engine's run capabilities.

 

[xander janssen]

Indeed other numbers are far more important, but here I was interested to see how much volume is displaced through these relative long and narrow tubes. Given your RPM range it does not look like the engine is struggeling to get the air in and the exhaust gasses out.

Laws of physic do not change, but scaling an engine down will change some important physical properties.

For example:

When scaling an engine by a factor of 2, the swept volume will reduce by a factor of 8, while the surface of the cylinder wall will reduce by a factor of 4. When building a true i.e. compression ignition Diesel engine, ratio between the amount of generated heat (compressed volume) over heat loss (cylinder + head surface) will become less favourable.

Basically why a mouse is the smallest warm blooded animal and the elephant, the former has the risk of becoming hypothermic (too cold) while the latter has the risk of becoming hyperthermic (too warm).

Furthermore, the swept volume (factor 8) will go through a valve surface (factor 4), reducing the speed of the air by a factor of 2. This can have the effect of bringing the flow of air from turbulent to laminar, which has dramatic consequences for the mixing of air and fuel in the cylinder.

 

[Longboy]

Indeed other numbers are far more important, but here I was interested to see how much volume is displaced through these relative long and narrow tubes. Given your RPM range it does not look like the engine is struggeling to get the air in and the exhaust gasses out.

Laws of physic do not change, but scaling an engine down will change some important physical properties.

For example:

When scaling an engine by a factor of 2, the swept volume will reduce by a factor of 8, while the surface of the cylinder wall will reduce by a factor of 4. When building a true i.e. compression ignition Diesel engine, ratio between the amount of generated heat (compressed volume) over heat loss (cylinder + head surface) will become less favourable.

Basically why a mouse is the smallest warm blooded animal and the elephant, the former has the risk of becoming hypothermic (too cold) while the latter has the risk of becoming hyperthermic (too warm).

Furthermore, the swept volume (factor 8) will go through a valve surface (factor 4), reducing the speed of the air by a factor of 2. This can have the effect of bringing the flow of air from turbulent to laminar, which has dramatic consequences for the mixing of air and fuel in the cylinder.

I would consider the intake and exhaust passage diameters which are normally reduced to scale along with the cyl. diameters to scale, maintaining a proper flow charge to the cyl. per cycle where a variance will not affect the operational range, RPM or smoothness. Also per previous post, the length of the intake tubes not adding much to the cyl. volumes. It is more likely that small scale model engines will not respond to math pretenses either actually or by predictability. However, since my engine is low RPM. My thoughts may be over ruled if the RPM range was extended to faster speeds and increased air volumes and not fit your research via SOLO's limited operational range.