Engine balancing and reciprocatory mass

[RevX]

I have watched a video of engine balancing in which the Technician told that the in engine balancing they make the counter weight= Rotary mass+Half of reciprocatory mass..Why full reciprocatory mass is not taken..and what are the impacts of taking full reciprocatory mass.

 

[drawoh]

RevX,

There are an awful lot of ways to unbalance an engine, and a similar number of ways to balance it afterwards. Centrifugal force is mass times radius. More radius, less mass!

--
JHG

 

[GregLocock]

OP - you aren't talking about overall imbalance as such, but using out of balance on the crank webs to compensate for the linear reciprocating mass. The 50% figure is a rule of thumb, but in real engines where people calculate this stuff out, a number between 40 and 60% is the usual result. The way it is done these days is to simulate the pressure in each main journal for every speed and load, and to optimise the local imbalances, while retaining overall balance, to minimise the peaks in bearing load.

Cheers

Greg Locock


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