M. Requin

As an ex-maker of electric basses the technique mentioned on the Jager Engineering site of using the audio frequency of a vibrating correctly tensioned timing belt appeals to me, as it is a very exact way of measuring tension in a vibrating "string". Belt manufacturers such as Gates are now selling devices to do this and it seems to be becoming a preferred measurement method (I see Ducati uses this approach, too). I downloaded the .wav file from Jager and had no problem using it adjust the timing belt tension when I did the TB/WP job recently. I also had a look at the sound file using a software soundwave analysis program, and it looks like it is about 43Hz - F1 on a music scale. I tried using a Boss bass tuner to adjust against, as well as my ear, and it seemed to be a pretty easy, functional approach.

Since I'm fundamentally against reinventing the wheel, I wonder if anyone else is pursuing this approach (majhopper, I saw you tried this from your recent post) and has any data on freq or on measurement technique to pass along? If not, I think I'll get the Kempf tool and hook up some of my fairly rudimentary electronic equipment and see if I can come up with something easy to do.

Alan

Ahh interesting approach.. great one for the musically inclined - timing belt tension by ear... for the pitch perfect ?

For me I'd need a frequency counter or something similar to be able to match the tones well - but its an attractive method.

Alan

Bill Ball

I have an adjustable guitar tuner too. I should give this a try. My old physics knowledge told me it should work well when Paul first proposed it. I do worry about my Kempf tool's calibration over time. It's years old now and has been tossed around a bit. This could be a good way to check that at the very least. Thanks for reminding me.

AO

I think there is an inherent problem with this method and that is that it relies on the assumption that all belts are similar enough in their build to give the same resonant frequency for a given tension. I don't know/trust the various manufacturers to use this method, therefore I will continue to use the Kempf tool. However, if you knew the pitch for a given manufacturer of the belt and always that same brand, it should work quite well, and may even be more accurate.

Bill Ball

If the mass and length of the vibrating section are the same, then equal tension will produce the same tone. I could weigh some of my old belts. The belts show almost no wear from new. Any belts worn enough to change mass should be replaced.

the flyin' scotsman

While I can acoustically agree the 'tuning' method may work has anyone compared a 'tuned' belt measured with the Kemp tool?

I have the same reservations as Bill as the Kemp tool may require calibration after sometime; anyone know the proceedure to verify? I assume replacing the spring is the only recourse if its out of cal.

M. Requin

You're both exaclty right: for this to work, there has to be a figure for each brand of timing belt (assuming they differ enough in belt mass, which some probably do), which means some testing would be needed. But the advantages are accuracy and repeatibility, I think. And using a bass/guitar tuner (which I think can work pretty well), you don't have to worry about your "ear", which is probably ruined by too much BWAAHHH anyway... Thanks for your input!

the flyin' scotsman

Racing motorcycles, Led Zep and Deep Purple concerts, kids, wifes............


Pardon, what was that dear?

MBMB

I can't seem to get a 43hz tone generated on my Mac. May be too low for the software to deal with.

Is this .wav file still available? Has the adjustment-by-ear method been discredited?

Bill Ball

Here you go :

M. Requin

It's on the Jager Engineering site somewhere. I'll email you the file if you can't find it (I'm pretty sure I still have it). As far as technique if you take a look at some of the belt manufacturers you'll see that this is a well-accepted method, although pro instrumentation doesn't use an ear...

MBMB

Perfect. Thanks.

MBMB

I'll bet the human ear comes pretty close to instrumentation.

Bill Ball

I made a 43Hz wav file with Audacity software. Please be sure that 43Hz is correct. It seems awfully low. I can't find the original on Jagers site any more, but I recall it being a higher frequency tone.

http://norcal928.org/43hz.wav

M. Requin

That's pretty funny, just went over to the GJ website and saw your post on Entropy. Very funny, as you might glean from my sig...