F4 1000s Critical speed - MVAgusta.net
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post #1 of 30 (permalink) Old 11-19-2012, 10:58 AM Thread Starter
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Question F4 1000s Critical speed

Has anyone with a F4 1000s came across a specific "critical speed" for this model? I have but I am curious to see if other F4 1000s owners have the same matching critical speed?

has anyone else with a different model found a specific critical speed for your model of bike?

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post #2 of 30 (permalink) Old 11-19-2012, 11:11 AM
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Is this the speed at which the front wheel begins to lift or the speed at which the whole bike gets airborne?

Sorry couldn't resist :-)
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post #3 of 30 (permalink) Old 11-19-2012, 11:12 AM
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What do you mean exactly by 'critical'?

I find my critical speed is dictated by the speed vs revs in the selected gear, otherwise I assume you must be referring to max speed?

Last edited by MV BOY; 11-19-2012 at 11:14 AM.
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post #4 of 30 (permalink) Old 11-19-2012, 12:22 PM Thread Starter
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I am refering to the rpm where a machine's resonance frequencies will cause vibration to the point of self destruction. Within all industry it is important to run up a machine through its critical speed as quickly as possible, whether it be a pump, compressor, turbine or other mechanical device.

Due to adverse road conditions the other day I spent a lot of time around 3500 - 4000rpm at some point between these rpm the vibration was excessive and after a 200 mile ride I found various bolts had worked themselves loose, one side stand bolt fully fell out, the other was half way out and various other bolts had loosened.
A lot of work & time offshore is spent on condition monitoring and vibration analysis to prevent this on all rotating equipment, I am just wondering if anyone has noticed higher vibration at specific revs

some are aware of critical speeds, others are not, ideally when a critical speed is established it should be avoided.

Last edited by F4-1NXS; 11-19-2012 at 12:24 PM.
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post #5 of 30 (permalink) Old 11-19-2012, 12:36 PM
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I've never heard of a "critical speed" used in that context. Nor have I gone on a long cruise and found stuff falling off of my bike. Are you sure you aren't talking to the Harley owners? Maybe Carl can enlighten us as to what RPM a Harley starts to fall apart.

Beyond that, RPM wise, vibration issues would be the result of a poorly balanced engine.
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post #6 of 30 (permalink) Old 11-19-2012, 12:49 PM
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F4 has it right, critical speeds exist where harmonics and tolerances combine to exponentially increase vibrations. Big commercial turbines have at least three critical speeds though which you pass quickly during turbine roll and start up to synchronous speed.

I'd say that you have discovered the "critical speed" for your F4...3500-4000 rpm.

It will be close to others, but it will be machine specific.

Keep your words soft and sweet, for someday you shall eat them....
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post #7 of 30 (permalink) Old 11-19-2012, 12:54 PM
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Quote:
Originally Posted by F4-1NXS View Post
I am refering to the rpm where a machine's resonance frequencies will cause vibration to the point of self destruction. Within all industry it is important to run up a machine through its critical speed as quickly as possible, whether it be a pump, compressor, turbine or other mechanical device.

Due to adverse road conditions the other day I spent a lot of time around 3500 - 4000rpm at some point between these rpm the vibration was excessive and after a 200 mile ride I found various bolts had worked themselves loose, one side stand bolt fully fell out, the other was half way out and various other bolts had loosened.
A lot of work & time offshore is spent on condition monitoring and vibration analysis to prevent this on all rotating equipment, I am just wondering if anyone has noticed higher vibration at specific revs

some are aware of critical speeds, others are not, ideally when a critical speed is established it should be avoided.

I've owned and rode a 1000s for years Roy and never had any of that happen to mine.


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post #8 of 30 (permalink) Old 11-19-2012, 01:12 PM
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Quote:
Originally Posted by adecritten View Post
I've owned and rode a 1000s for years Roy and never had any of that happen to mine.


I check all my nuts and bolts every so often and usually find that my aftermarket carbon additions need tightening but not much and that's only due to not using a thread lock.

My bike certainly isn't critical between this rev range and if anything vibration is more obvious around 6000 - 7000and my hands and fingers are the first sign of that lol
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post #9 of 30 (permalink) Old 11-19-2012, 02:23 PM
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Argh, you beat me to the Harley comment.

Quote:
Originally Posted by Ryan Stewart View Post
I've never heard of a "critical speed" used in that context. Nor have I gone on a long cruise and found stuff falling off of my bike. Are you sure you aren't talking to the Harley owners? Maybe Carl can enlighten us as to what RPM a Harley starts to fall apart.

Beyond that, RPM wise, vibration issues would be the result of a poorly balanced engine.
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post #10 of 30 (permalink) Old 11-19-2012, 03:22 PM Thread Starter
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Originally Posted by adecritten View Post
I've owned and rode a 1000s for years Roy and never had any of that happen to mine.




ade, I also have been riding F4's for 9 years but I have never sat between 3500 / 4000rpm for a considerable duration of time such as I did last week, normally on the EV03 I prefered to sit around 7000 - 8000rpm+, on the 312R and the 1000s I also prefer high up in the rev band, but as I previously mentioned due to appauling road conditions I was stuck at the lower mentioned revs for some considerable time, this is where I believe I have found the problem on my machine and the only explanation I can give is critical speed as its a thing I have dealt with often in the past whilst working with vibration analysis.
Riding through a critical speed is not a problem and should be encouraged, but to sit on a rpm similar to natural frequency is a problem.

Critical speed is a phenomenon, the same as compressor surge is, but both have wrecked machines time and time again.

This will be a one off for me, as I am aware of it now, up to yourselves if you want to take note on this or not.

Last edited by F4-1NXS; 11-20-2012 at 05:15 AM.
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