cam belt tension alternative
 

Just for interest sake, any comments on the following excerpt of an email I got recently for tensioning 4v cam belts;

SPX is no longer reselling the belt tensioning tools to me at a dealer price, so I have stopped selling the tools. Instead, you can use the "sonic" method referenced in the factory manual for ST4s. You want a vibration of 112 Hz. Please read the e-mail from the ST owners list referenced below for more details. For the actual frequency measurement, you can download the FREE software from this link: http://www.techmind.org/audio/#mustun
(download his frequency counter) And then any cheap microphone plugged into your computer in combination with this free software replaces the >$400 handheld gauge or the multiple thousand dollar Ducati "mathesis" tester.

Questions;
Anyone tensioned belts this way?
How would you calibrate the microphone (take a reading from existing tensioned belts?)
Would any "cheap" mic. work, or would it pick up too much interference?

And finally; 'Cat among pidgeons' also springs to mind :D
Cheers,
Pete.

belt tension theory
 

This page kinda explains the idea.

http://www.clavis.co.uk/page2.htm

Interesting! I've not seen the 'sonic' method before but I presume the basis of this technique is to treat the belt (or section thereof) as a kind of guitar string. Thus, the frequency of the belt vibration (after being plucked) will be determined directly by the tension of the belt (assuming that belt to belt variation is not a complicating factor of course). The 'sound' of the belt will then be picked up by the microphone and then displayed on an oscilloscope (or a PC program doing the same thing). Any microphone with sensitivity to the relevant frequency should work though experimentation will be necessary to get a clean signal from the belt (ie other bits may also vibrate). Calibration of the microphone will not be necessary as you just count the oscillations per second and you can just set belt tension so you get 112 waves per sec. You would obviously also want to check against a correctly tensioned belt to confirm the quoted 112Hz! I should be able to knock something up so I might give it a go!

Keith

In my previous job where I worked for a company that designed automotive belt drives, inc. primary drives, we used to use a clavis gauge so I am very familiar with this device.

Don't forget each span will have its own frequency so make sure you are checking the correct span.

If anyone wants to check your microphone method against a clavis gauge let me know and I can bring one along.

I actually spoke to one of the technicians at Clavis, who was really approachable and told me lots of interesting stuff! They make the gauge that Ducati use to tension the testastretta engines. I think he said it's an optical pickup head on the gauge.
He popped away and came back with the info on the 4v engine. Tension is checked on the lower run on the horizontal cylinder and on the left side run on the vertical. (I'm no technical expert at this so any claims made in this thread have no actual factory or otherwise guarantees ok!).
Jeez, I sound like a lawer :D.
Keith, I like your bit about just taking the readings of the oscillations, regardless of the type of mic. used, kinda makes sense to me when put like that.
I wish Clavis would just sell me one of their heads so I could plug it into my computer!
Pete.

This is the puppy I've found so far, but I'm not sue if it would need a power supply as well.
http://www.dv247.com/invt/5869/

The thought also occurs that an old pickup/stylus from a record deck (remember those?) might also work (and give a bigger signal).

Keith

i used the snap-on/ast version very similar to sealey vs009, using button decided by belt width gauge provided, to tension 2 new belts on a 996S 2 years and 9000 miles ago. the bike has performed faultlessly over that period.

The Sealey vs009 is currently offered for £140 inc p&p at http://www.oldclassiccar.co.uk/tools...5009_vs009.htm

but i recently bought the Facom DM.16, which predates but appears identical to vs009, etc., for £110 on ebay buyitnow from davethetools, owna HD tools. last time i looked, he was still offering the same deal.

SPX gave me the price of their tension tool 303-201, previously number 21-113 recommended by ducati, in euros 200.43 equal to about £146 plus VAT but I dont know if they would mail it direct.