Opposed cylinder engines would make less noise if they rotated at lower rpm and more power if they ran higher mean piston speed for same thermal stress levels.
The mean piston speed of ungeared VW,Lyc,Con is around 8-9 m/sec and geared Rotax has good reliability at 12m/sec.
VW,Lyc,Con etc would be less noissy and more powerful for same mass with smaller pistons and longer strokes.It would also look a lot less sexy up front
Let me try to argue for an inline,inverted two cylinder fourstroke that can make 40 hp at 50 rps.
Usefull for quite some single seaters IF you accept the torque vibrations from a two cylinder even fire fourstroke (or a single cylinder direct drive two stroke).
Stroke must be 120mm for a mean piston speed of 12m/sec.
A simple horsepower formula can be :
(MEP (in bar) *swept volume (litre)*working strokes(per second))/75=horsepower.
It can be shown that four-strokes can do MEP ca 10 bar with good design and no smart supercharging.
The Sidevalved D-Motor does at least.
And Lycconts and VWs
Nessecary cylinder volume for my poor mans Merlin
(10*volume*25)/75 =40 makes a volume of 1.2liter nessecary or 600 ccm per cylinder that have strokes of 120mm and therefore a bore of 80mm.
D-Motor compress 8 to 1 and is 25 kg per litre including liquids and radiators.
My engine has 80mm bore and 120 mm stroke and D-Motor has 102 bore and 80mm stroke.
Both handle same maximum pressure and If I had not to do a countrrotating shaft and some counterweights on crank my specifig liter mass will be lower due to bore/stroke ratio.
I have to so let me say that my proposal is 1.2 liter of 25kg each i e 30 kg total.Is that worthwhile?
The mean piston speed of ungeared VW,Lyc,Con is around 8-9 m/sec and geared Rotax has good reliability at 12m/sec.
VW,Lyc,Con etc would be less noissy and more powerful for same mass with smaller pistons and longer strokes.It would also look a lot less sexy up front
Let me try to argue for an inline,inverted two cylinder fourstroke that can make 40 hp at 50 rps.
Usefull for quite some single seaters IF you accept the torque vibrations from a two cylinder even fire fourstroke (or a single cylinder direct drive two stroke).
Stroke must be 120mm for a mean piston speed of 12m/sec.
A simple horsepower formula can be :
(MEP (in bar) *swept volume (litre)*working strokes(per second))/75=horsepower.
It can be shown that four-strokes can do MEP ca 10 bar with good design and no smart supercharging.
The Sidevalved D-Motor does at least.
And Lycconts and VWs
Nessecary cylinder volume for my poor mans Merlin
(10*volume*25)/75 =40 makes a volume of 1.2liter nessecary or 600 ccm per cylinder that have strokes of 120mm and therefore a bore of 80mm.
D-Motor compress 8 to 1 and is 25 kg per litre including liquids and radiators.
My engine has 80mm bore and 120 mm stroke and D-Motor has 102 bore and 80mm stroke.
Both handle same maximum pressure and If I had not to do a countrrotating shaft and some counterweights on crank my specifig liter mass will be lower due to bore/stroke ratio.
I have to so let me say that my proposal is 1.2 liter of 25kg each i e 30 kg total.Is that worthwhile?
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