"Safe" maximum mean piston speed?
- Thread starter Sonreir
- Start date
scm
Been Around the Block
For given stroke, yes, of course (teaches the formula).
Just seemed uncommon to me, maybe you wanted to
build up a stroker engine.
Back to topic, I'm a Yamaha man, can't tell. Normally
japanes engines are much less sensitive to over-revving(?)
than british or european ones.
Best regards
Sven
Just seemed uncommon to me, maybe you wanted to
build up a stroker engine.
Back to topic, I'm a Yamaha man, can't tell. Normally
japanes engines are much less sensitive to over-revving(?)
than british or european ones.
Best regards
Sven
Thanks, Sven. At some point I'd be interested in a stroker, but I'm actually wondering about revs for my current build. My 360 is only a single valve and so I know breathing will be an issue, but I'm wondering is the breathing will be a problem before the revs will...
rockcitycafe
I make things.
it depends on the mass of the piston, pin and conrod, a lighter piston will exert less force on the rod, pin and bearing than a heavier one will, honestly, there are other things in that engine that'll fail long before the rods do.
crazypj
Split personality, I fake being smart
12,000 is a fair guess from the math 
Centrifugal loads are the problem
With different ignition and lighter piston, 12,500 isn't really a problem, big end bearings will fail before rods snap, rings will 'flutter' and break pistons around 13,500, although you will get a few thousand miles out of it before re-ringing or blowing up ;D
I use stock cams and about 11~ 11,500 in my 378cc motors although they are past peak power by 10,500 (points 'bounce' around 11,750~12,000)
Cam oiling is the main issue, use 5w/40 full synthetic (Rotella is JASO spec 8) )
Centrifugal loads are the problem
With different ignition and lighter piston, 12,500 isn't really a problem, big end bearings will fail before rods snap, rings will 'flutter' and break pistons around 13,500, although you will get a few thousand miles out of it before re-ringing or blowing up ;D
I use stock cams and about 11~ 11,500 in my 378cc motors although they are past peak power by 10,500 (points 'bounce' around 11,750~12,000)
Cam oiling is the main issue, use 5w/40 full synthetic (Rotella is JASO spec 8) )
Stroke is 50.6 and full throw is 50.6 not 101.2!.
Rings are limited by the rate of acceleration before they flutter.
Pistons tend to fail over a certain MPS level
Big ends fail when their design limits are exceeded and forces rise with the square or is the cube of rpms.
Ports stop flowing at around 0.55 mach
In other words, you really need to work through every design aspect and work out what the limiting factors are.
In this case I think the oil system fails first.
Rings are limited by the rate of acceleration before they flutter.
Pistons tend to fail over a certain MPS level
Big ends fail when their design limits are exceeded and forces rise with the square or is the cube of rpms.
Ports stop flowing at around 0.55 mach
In other words, you really need to work through every design aspect and work out what the limiting factors are.
In this case I think the oil system fails first.
scm
Been Around the Block
No problem, the following is an approximation
formula for the inertia force F caused by a crank
driven reciprocating mass:
F = m*r*ω²*[cos(φ) + λ*cos(2*φ)]
with
m reciprocating mass,
r eccentricity of crank,
ω angular velocity (rad/s),
φ crank angle (0 = tdc)
λ crank:rodlength ratio (r/l)
Best regards
Sven
formula for the inertia force F caused by a crank
driven reciprocating mass:
F = m*r*ω²*[cos(φ) + λ*cos(2*φ)]
with
m reciprocating mass,
r eccentricity of crank,
ω angular velocity (rad/s),
φ crank angle (0 = tdc)
λ crank:rodlength ratio (r/l)
Best regards
Sven
