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cyclebrain
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Joined: Jun 16 2006 - 11:40pm
Not quite room tuning, but is related

My Ducati requires an expensive laser device too tension its' cam belt by measuring the belts resonant frequency when the belt is plucked. The spec is 110Hz +/-5Hz.
So why not break out my laptop running TrueaudioRTA (spectrum analyzer) and a microphone? Didn't know if the S/N would be good enough, or if the peak would be narrow enough to provide the resolution required.
It worked fantastic, nice big amplitude with a narrow bandwidth, and it was repeatable.
I'm still amazed when theory and practice agree.

piinob
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Re: Not quite room tuning, but is related

Pretty Cool. I knew Ducks took special tools but not many details. Never had ione myself although several friends have them. Is this measured with a microphone or an optical sensor or... I would be curious how it is done.

KBK
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Re: Not quite room tuning, but is related

likely an accelerometer.

cyclebrain
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Re: Not quite room tuning, but is related

Like I said in my original post, the factory device uses an optical source and an optical reader.
My method uses a microphone.
Using an accelerometer is an other idea that I hadn't thought of.

ethanwiner
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Re: Not quite room tuning, but is related


Quote:
measuring the belts resonant frequency when the belt is plucked. The spec is 110Hz +/-5Hz.


Or just match it to an A note on a piano or guitar.

KBK
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Re: Not quite room tuning, but is related


Quote:
Like I said in my original post, the factory device uses an optical source and an optical reader.
My method uses a microphone.
Using an accelerometer is an other idea that I hadn't thought of.

Sorry. Then they likely use the sensor in the point of most flexture in order to utilize the greatest amount of flex in the 'string' (belt) for as much frequency accuracy as possible.

One can create a similar device with an extremely small amount of very light aluminum tape (hardware shop, or, old open reel metal tape for direction sensors)..and place a rigidly mounted tape head along side the belt,and then measure/record the frequency.

A handy electronics guy could have such a system up and running in a single afternoon, by butchering an old cassette deck and running the signal into a PC sound card for analysis.

The smart thing to do is to change the size/mass of the small piece of aluminum tape by a factor of exactly two, to check on any frequency change of the belt due to the added mass. If the change is negligible, then the numbers recorded stand a chance of being accurate.

If change is noted, then compensation must be intelligently applied. Weigh the belt, consider the tension, consider the mass of the suspended plucked section...and then compare the mass levels of the added tape piece - and then consider again.

~~~~~~~~~~~~~~~~~~~~~~~~
I'm saying this all due to the fact that my mind is attuned to the idea of checking the belts on TURNTABLES. A far more delicate situation, with regards to measurement complexity.

Nice bike! By my mind went straight to the turntable belt.

Nice idea of the bike, though, I'm sure it works 100% fine.

I'll bet that Ducati does it the optical way with special hardware, strictly due to liability/warranty and consistency considerations. Not because they want their mechanics/shops to invest in ridiculously expensive hardware, it's just that reliable and consistent measurements need be taken, even in the hands of someone who could be termed a 'numbnuts'. Bulletproof and reliable application, is the byword.

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