Reciprocating mass

[Danger]

Without googling the term I would like to hear what your immediate understanding of reciprocating mass is, or if you even have any idea what it is? Just trying to get an idea of the level of knowledge out there regarding this, so don't be worried if you get it wrong. I will reveal the reason why I ask later.

[noobi]

Without googling the term I would like to hear what your immediate understanding of reciprocating mass is, or if you even have any idea what it is? Just trying to get an idea of the level of knowledge out there regarding this, so don't be worried if you get it wrong. I will reveal the reason why I ask later.

i understand it to be the point in which a mass is forced to go in the opposite direction to which it was going, thus it must overcome the moment of enertia. like a piston has to be forced to go up after getting to the bottom of the stroke? year 12 physics boyo

[diesel_mr2]

An object turning in a circular motion, e.g: a wheel?

[kezzafish]

yeah i thought reciprocating meant spinning/turning and mass is mass. when do we get to know why you ask?

[Sam I Am]

sounds like the counter weight in a thumper to offset the piston and rod ?

[Sam I Am]

ok now I have googled it and I got it wrong Duh

[kezzafish]

"Flywheel" is much a simpler way to say it. But it doesn't have to be a motor it can be any thing which spins and has a mass?? the earth even

[Gravel911]

errrrrrrr ummmmmmmmmm

I think it’s the parts that have to change direction of travel in the engine

i.e. Piston, rings, gudgen pin and probably part of the rod.

I know the Husaberg engines have a little rotating weight that spins in the opposite direction to counter the effect of reciprocating mass

[flyingcr250]

yeah i thought reciprocating meant spinning/turning and mass is mass. when do we get to know why you ask?

a spinning object has less recipricating mass than an object heading in opposite directions , like the difference between a piston engine and a rotary engine. or a sabre saw and a circular saw.

[CookMySock]

A moving mass with a longitudal path that reverses direction upon itself twice for every cycle. Do I win?

Steve

[cheese]

Noobi explained it well, but yes a piston is a perfect example. Man 6th form physics are only just there in the back of my memory...

[oldskool]

i understand it to be the point in which a mass is forced to go in the opposite direction to which it was going, thus it must overcome the moment of enertia. like a piston has to be forced to go up after getting to the bottom of the stroke? year 12 physics boyo

I agree with noobi, a mass that reverses on itself and is the point of failure. Like my brain when I headbang to music.

[flyingcr250]

Noobi explained it well, but yes a piston is a perfect example. Man 6th form physics are only just there in the back of my memory...

oh no rotary bike engines?? please god no.

[Motu]

I've given this one a bit of thought these last few years after my experiments with the XT400/500/600/621.The changes in an identical bike with changes in reciprocating mass were very marked....it's not so much an engine capacity difference,it's the reciprocating mass.The 400cc engine,with shorter stroke,lighter flywheel etc was much easier to ride - just flicked through the gears up and down without any effect on the motorcycle itself.Just riding the bigger capacity engine bike,it felt heavier,you could really feel the capacity change through the reciprocating mass.The bigger capacity bike was much more powerful of course,but harder to ride.Coming out of turns there was heaps of wheelspin of course....but more than could be controlled by just the throttle.Most noticeable was coming into turns - the smaller capacity bike was very stable,I was able to set up slides with ease....the bigger engines were almost uncontrollable by contrast.I could just rail the turns on the little engine,and was a total mess with the bigger engine.

So when I wanted a BMW airhead to set up for gravel roads - I went for the small capacity R65.Less reciprocating mass means less wheel spin out of turns,and is much more stable on turn entry.The road surface is able to control engine speed....rather than the engine dictate things.

Also after the DT230,I found lack of engine braking a big advantage....2 strokes have that advantage.MotoGP teams have spent as much effort reducing engine braking as gaining HP.

Dunno if this is what you want to hear - but I want minimal engine braking,and an engine that can react to surface conditions to maintain traction.I'm all for less reciprocating mass.

[Danger]

Excellent post Motu, and sorry I can't give you gas as apparently I've given out too much in the last 24 hours! Everyone that posted above you got gas for answering.