Engine Balancing
12-23-2002, 06:34 PM
#51
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Engine Balancing
Dave:
What is commonly called a harmonic "Balancer" is not. It is a damper (NOT dampENer) to remove or decrease the tendency of a crankshaft to twist torsionally in operation. Viscous (semi-liquid) dampers have been used foir many years.
Mark:
If it works, it works.
I just don't see how centrifugal force will push the movable weight to the lighter side.
In trucks, I'm sure you've seen the big harmonic damper on the Cummins 855 engines, that's an example of Dave's viscous damper.
Quote Mark:
when you are upside down down is up and up is down!
DOH!
It's all a matter of perspective. When you try it blindfolded tell me; I'll want to watch.
Liquids tend to slosh, my twins say it's bosh.
Bill.
What is commonly called a harmonic "Balancer" is not. It is a damper (NOT dampENer) to remove or decrease the tendency of a crankshaft to twist torsionally in operation. Viscous (semi-liquid) dampers have been used foir many years.
Mark:
If it works, it works.
I just don't see how centrifugal force will push the movable weight to the lighter side.
In trucks, I'm sure you've seen the big harmonic damper on the Cummins 855 engines, that's an example of Dave's viscous damper.
Quote Mark:
when you are upside down down is up and up is down!
DOH!
It's all a matter of perspective. When you try it blindfolded tell me; I'll want to watch.
Liquids tend to slosh, my twins say it's bosh.
Bill.
12-23-2002, 10:10 PM
#52
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Engine Balancing
Quote from their page on how it works...
"American engineers perfected the idea in the late 1930's and early 1940's when they needed to find a way to perfectly, precisely and continuously balance a new-fangled invention...the jet turbine engine."
LOL...who are they trying to kid??
"American engineers perfected the idea in the late 1930's and early 1940's when they needed to find a way to perfectly, precisely and continuously balance a new-fangled invention...the jet turbine engine."
LOL...who are they trying to kid??
05-04-2003, 03:21 PM
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Engine Balancing
I got wind of this wind from RunRyder. There seems to be some confusion on how to ballance a crand shaft so I would like to add my input.
The correct bob-weight is half of the piston with all its parts and half of the top end of the con rod and all of the bottom of the con rod.
Another way to look at it is to weigh the piston-ring-pin-conrod assembly and divide that weight in half. Add back in 1/4 the weight of the con rod. Now use that number to make a weight on your lathe to fit on the crank shaft pin where the big end of the con rod normally goes. Now ballance this assembly.
Single cylinder engines will NEVER be able to be ballanced completely.
The reason for this is that the piston only goes up and down and any counter weight on the crank goes 'round 'n 'round. The more counter weight on the crank the more you can offset the piston going up and down. So you can offset the up and down vibration. But as you add more counter weight, the motor starts to vibrate side to side. The only answer is to put enough counter weight on the crank so the up and down vibration is equal to the side to side vibration. This way the counter weight will offset half of the up and down vibration while causing that same amount of vibration side to side.
Now, when you mix these two vibrations that are 90º out of phase, you get a circular vibration that acts like it's rotation is opposite of the crank rotation. Just like a smooth running shaft with a weight mounted on the side of the shaft.
The only way to cancell this last amount of vibration is to have a counter rotating weight concentric or near the crank shaft center line. Some motorcycle engines have used this method of vibration control.
Wolfgang
The correct bob-weight is half of the piston with all its parts and half of the top end of the con rod and all of the bottom of the con rod.
Another way to look at it is to weigh the piston-ring-pin-conrod assembly and divide that weight in half. Add back in 1/4 the weight of the con rod. Now use that number to make a weight on your lathe to fit on the crank shaft pin where the big end of the con rod normally goes. Now ballance this assembly.
Single cylinder engines will NEVER be able to be ballanced completely.
The reason for this is that the piston only goes up and down and any counter weight on the crank goes 'round 'n 'round. The more counter weight on the crank the more you can offset the piston going up and down. So you can offset the up and down vibration. But as you add more counter weight, the motor starts to vibrate side to side. The only answer is to put enough counter weight on the crank so the up and down vibration is equal to the side to side vibration. This way the counter weight will offset half of the up and down vibration while causing that same amount of vibration side to side.
Now, when you mix these two vibrations that are 90º out of phase, you get a circular vibration that acts like it's rotation is opposite of the crank rotation. Just like a smooth running shaft with a weight mounted on the side of the shaft.
The only way to cancell this last amount of vibration is to have a counter rotating weight concentric or near the crank shaft center line. Some motorcycle engines have used this method of vibration control.
Wolfgang
05-05-2003, 01:39 AM
#56
Wolfgang....
....do you do this type of balancing ?
I have a Super Tiger that vibrates real bad. I need to
check it for a bent crank....I got it used. And I have
two others as well. There all 3000's. I don't have the
scales and necessary stuff to do it.
Dave.
I have a Super Tiger that vibrates real bad. I need to
check it for a bent crank....I got it used. And I have
two others as well. There all 3000's. I don't have the
scales and necessary stuff to do it.
Dave.
05-05-2003, 02:10 PM
#58
Engine Balancing
Ok, Wolfgang....I just thought I'd ask. I have all the
grinding stuff....and I guess I might be able to use my
prop balancer as a stand. I'll just have to come up with
the scales....and give it a try. Can you post a pic of how
you made the weight, and how you hung it off the crank
in the stand ?
Thanks for posting the info....
Dave.
grinding stuff....and I guess I might be able to use my
prop balancer as a stand. I'll just have to come up with
the scales....and give it a try. Can you post a pic of how
you made the weight, and how you hung it off the crank
in the stand ?
Thanks for posting the info....
Dave.
05-05-2003, 03:10 PM
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If you do not have a scale, you can make one from a carbon tail boom support rod. Tie a string around the center to support it, then measure out one side at 5" and tie another string to it for hanging the piston-pin-con rod assembly. Tie another string on the other side at 10" for the weight. make a weight to ballance. The weight is nothing more than a cylinder of metal with a hole in it the size of the crank pin and about 1" in diameter. Make the thickness to suit the needed weight.
Do this again for the con rod alone and use a ratio of 2-1/2" and 10" to get the 1/4 weight ratio. Add this weight to the first weight and ballance the crank.
Crude but effective if you don't have a scale.
Wolfgang
Do this again for the con rod alone and use a ratio of 2-1/2" and 10" to get the 1/4 weight ratio. Add this weight to the first weight and ballance the crank.
Crude but effective if you don't have a scale.
Wolfgang
05-05-2003, 06:53 PM
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Holeshot:
Make Perry pumps obsolete?
The Perry oscillating pump that works from engine vibration, yes.
But there is no substitute for the VP-30 running on crankcase pressure.
Except maybe the Cline system, and Cline is more expensive.
Bill.
Make Perry pumps obsolete?
The Perry oscillating pump that works from engine vibration, yes.
But there is no substitute for the VP-30 running on crankcase pressure.
Except maybe the Cline system, and Cline is more expensive.
Bill.
