Balanced Engine vs Balanced Crank
Posted: Thu Feb 19, 2004 2:49 pm
With all of the talk about un-balanced cranks lately, and some of the other post I've been seeing, I started thinking about what exactly is a balanced crank, and are the Cannondale engine builders actually balancing our cranks, or balancing our engines, and does it matter?
I am by no means an expert on this subject, just trying to learn and get everyones ideas.
First, I'll throw out my definitions:
Balanced Engine: A balanced engine will have the weight matched for the opposing forces in the engine: i.e. The weight of the piston, piston pin, rings, rod, and counterbalance will be matched to the weight of the crank so that as they are spinning opposite each other everything balances out.
Crank balancing: To properly balance a crank, it is installed on a machine that spins the crank at high RPM's that checks for proper balance - similar to balancing a tire. Given that our crank is single cylinder and all the weight is on one side it can't be 100% balanced, however it can be trued and adjusted for best performance in out engines.
From the Falicon website: A single cylinder crank is always unbalanced. The balancing operation we perform moves that unbalance (vibration) to an RPM that is either higher or lower than your engine's RPM operating range. We accomplish this by removing or adding weight to the crank in a location that our balancing equipment has told us to do so. Balancing or "moving the unbalance" really helps a single cylinder crank, especially if it is to be used at sustained high speeds.
OK, so I know from the factory that when the cranks where changed for 03' they where lighter than the old style cranks. Based on my definitions above, this would cause our engines to be out of balance, not necessarily the cranks to be out of balance. The factory corrected this late in 03' by adding weight to the crank.
I just saw a post from Southbay stating These kits have been balanced to the new style crank to prevent the known balance issues associated with the OEM piston kits. which again goes toward balancing the engine.
So my questions are:
Are the cranks themselves in balance, and if not, is anyone doing anything about it?
When the factory added the weight to the 03' cranks to correct engine balance, they put it all on one side. Wouldn't that throw the side-to-side balance of the crank itself out?
How much out of balance can our engines be without causing exsessive vibration and wear? my understanding is that the stock bore piston is 4 grams lighter than the 450 - is this a problem?
I am by no means an expert on this subject, just trying to learn and get everyones ideas.
First, I'll throw out my definitions:
Balanced Engine: A balanced engine will have the weight matched for the opposing forces in the engine: i.e. The weight of the piston, piston pin, rings, rod, and counterbalance will be matched to the weight of the crank so that as they are spinning opposite each other everything balances out.
Crank balancing: To properly balance a crank, it is installed on a machine that spins the crank at high RPM's that checks for proper balance - similar to balancing a tire. Given that our crank is single cylinder and all the weight is on one side it can't be 100% balanced, however it can be trued and adjusted for best performance in out engines.
From the Falicon website: A single cylinder crank is always unbalanced. The balancing operation we perform moves that unbalance (vibration) to an RPM that is either higher or lower than your engine's RPM operating range. We accomplish this by removing or adding weight to the crank in a location that our balancing equipment has told us to do so. Balancing or "moving the unbalance" really helps a single cylinder crank, especially if it is to be used at sustained high speeds.
OK, so I know from the factory that when the cranks where changed for 03' they where lighter than the old style cranks. Based on my definitions above, this would cause our engines to be out of balance, not necessarily the cranks to be out of balance. The factory corrected this late in 03' by adding weight to the crank.
I just saw a post from Southbay stating These kits have been balanced to the new style crank to prevent the known balance issues associated with the OEM piston kits. which again goes toward balancing the engine.
So my questions are:
Are the cranks themselves in balance, and if not, is anyone doing anything about it?
When the factory added the weight to the 03' cranks to correct engine balance, they put it all on one side. Wouldn't that throw the side-to-side balance of the crank itself out?
How much out of balance can our engines be without causing exsessive vibration and wear? my understanding is that the stock bore piston is 4 grams lighter than the 450 - is this a problem?