NVH kit accelerometer

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Re: NVH kit accelerometer

Postby Steve Smith » Mon Aug 10, 2015 8:17 am

Thank you for the continued feedback with this post its all good stuff.

I have searched below for the Gates tool you mentioned and came up with some interesting pointers

https://www.gates.com/products/industri ... ccessories

Their website allows you to download the "Sonic Tension Meter" manual where I had a brief look through the theory and operating instructions

It would appear after entering specific details about the belt (Including Mass) by tapping on the belt with microphone positioned in close proximity, we can acquire a tension result.

I cannot believe I have never heard of such a device which does concern me as I wonder just how many workshops are equipped with such a device and more importantly how many of those are using them?

I would be very interested to know just how simple the process would be and how vulnerable the results are to incorrect use?

The handbook does go on to mention some interesting optional extras such a s the flexible flat microphone and the inductive sensor!

The inductive sensor sounds intriguing too whereby a magnet is secured to the "flat" side of the belt whilst the deflection of the belt is measured by the inductive sensor.

I can see this option removing some of the many variables associated with a microphone, Gates themselves claim this is the desired electronic belt tension measuring method in windy conditions.

For some reason when this post began I had it in my head that we could look at belt tension whilst running as part of routine service.

Here technician would apply the microphone within the timing belt service port, (where applicable) enter in vehicle/belt details and run the engine!

I guess that was a bit science fiction but not impossible if the formulas exist, however, there would simply be thousands of variables.

Both the microphone and the inductive sensor could be added to PicoScope with no issues, (possibly a feature of Pico Diagnostics) the challenge would be for the software to calculate the tension based on the formulas used by Gates.

I will add the additional comments here into the file I have raised as a result of this post, thank you and keep them coming.

Take care......Steve
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Re: NVH kit accelerometer

Postby Technician » Mon Aug 10, 2015 8:21 pm

steve smith wrote:Thank you for the continued feedback with this post its all good stuff.

For some reason when this post began I had it in my head that we could look at belt tension whilst running as part of routine service.



Steve, a few notes...

It would appear after entering specific details about the belt (Including Mass) by tapping on the belt with microphone positioned in close proximity, we can acquire a tension result.

It only works on Gates Belts, don't try it on other makes you'll be upset.

I cannot believe I have never heard of such a device which does concern me as I wonder just how many workshops are equipped with such a device and more importantly how many of those are using them?

I have if memory serves me correctly owned the tension tester since about year 2000.

I would be very interested to know just how simple the process would be and how vulnerable the results are to incorrect use?

It's possible that Gates have updated it since I bought mine, must admit to not having used it for a long time, there is also a chip inside which is update able as technology moves on.

The inductive sensor sounds intriguing too whereby a magnet is secured to the "flat" side of the belt whilst the deflection of the belt is measured by the inductive sensor.

I can see this option removing some of the many variables associated with a microphone, Gates themselves claim this is the desired electronic belt tension measuring method in windy conditions.

These last two sentences read like updates I think?

Here technician would apply the microphone within the timing belt service port, (where applicable) enter in vehicle/belt details and run the engine!

I guess that was a bit science fiction but not impossible if the formulas exist, however, there would simply be thousands of variables.

Back in my day there were no service ports, the microphone was simply held very close to the belt and the belt was flicked with your fingers :)

What we choose to believe is science fiction Steve in reality is not, take the TV program the car KIT and Micheal Knight, back then everyone thought its science fiction on TV, try getting away with that today?

Both the microphone and the inductive sensor could be added to PicoScope with no issues, (possibly a feature of Pico Diagnostics) the challenge would be for the software to calculate the tension based on the formulas used by Gates.

I don't see too much of an issue with the calculations for tension and creating formulas to be honest, there are some very bright people in our industry :)
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Re: NVH kit accelerometer

Postby LEYLAND MILL MOTORS » Tue Aug 11, 2015 2:46 pm

We have the gates sonic tension tester

It is used on manually tensioned timing belts. However the tradition now appears to be for automatic belt tensioners so gets very little use now.

We got it because Gates said for any warranty to be given on timing belts you had to prove method of installation. Years of knowledge was not enough. So we got the STT-1 and online autodata for method of replacement. This was enough to cover any warranty issues (thankfully we never had any)

It is very easy to use, just type in the gates timing belt number, place one of the two speakers over the span of belt as indicated on the box or auto data and give it a flick, the too then measures the vibration frequency of the belt and lights whether the belt is ok, too loose or too tight.

There is also a feature that I have never used ot tried. You could enter the span length between pulleys of any belt and measure the tension of those toothose. If memory serves me right you could do both poly-vee and vee belts.

Hope this helps a little?

Great site by the way :D
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Re: NVH kit accelerometer

Postby Steve Smith » Wed Aug 12, 2015 7:43 am

Thank you for the feedback, the tool you have posted looks very simple to use with Gates belts for sure.

Interesting to see we have 2 x microphones in the image. The model I have looked at on their site is the "508C" which seems to use a single microphone and requires 3 data entries (Mass, Width and Span) which I guess could lend itself to non Gates belts.

V-belts are also included within the manual and so it would seem possible to apply this tool to any belt assuming the formulas are relevant.

I can see a possible PicoScope application here but you mentioned the "automatic belt tensioners" which does remove some of the "unknowns" during installation.(Also reducing the use of such a tool) Chain driven engines seem to be on the rise too!

Perhaps the major use of such a tool would be evaluating belt tension whilst in service (between intervals).

What about timing chain evaluation in a similar fashion? (Microphone placed onto timing cover) could there real value here as this is a tricky one given the chain is hydraulically tensioned.

I know the PCM can see Cam Crank correlation issues as a result of Cam Crank signal "phase shift" (worn timing chain), could a microphone application detect anomalies in the frequency generated by a worn timing chain? (Better still a chain showing signs of wear but not worn)

This would need serious investment to research but not beyond the realms of possibility for sure.

Great input from all, thank you.
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Re: NVH kit accelerometer

Postby Valhalla » Wed Aug 12, 2015 12:39 pm

Hi Steve (el. al.),
I think that it must have been an early prototype from Gates that I had used in 1997. At the time, they were trying to make some progress in the OEM market, and a data-driven approach using such tools as described above was their way forward.

The biggest problem I encountered during any of the tensioning processes was the precise timing of the belt, which has a big input to the frequency measured. This is why I found that a dynamic resonant frequency was more reliable, if less predictable, than a static test. What would often happen is that the engine would place the belt under load on the working side, and the elasticity of that portion of the belt would then lower the measured frequency on the slack (tensioned) side of drive-system. This was fine if the timing was exact, bearing in mind that a timing pin would have to be fitted to confirm pulley positions before being removed for frequency measures.

The downside to resonant frequencies whilst running was that the belt has so many modes of oscillation; under stroboscopic light in a darkened dynamometer cell, I measured not only longitudinal frequencies, but torsional frequencies as well, often at the same time! Added to which, each manufacturer's belt material behaved differently, even when the mass/unit length&cross-section was quoted as the same.

However, with a "good known base" measurement, it should not be impossible to establish what state a timing is in. Not least that if the microphone can be made reasonably robust against oils, etc. then a chain analysis is also possible, as well as belt-in-oil systems like the current small Peugeots/Fords.
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Re: NVH kit accelerometer

Postby LEYLAND MILL MOTORS » Wed Aug 12, 2015 7:57 pm

I personally found the tool very easy to use, the reason for 2 microphone's was just ease of access for one or the other in my experience.
It could be a little bit of a pain at times, as when tensioned and then turn crank twice and recheck the tension on the belt, the tight (measured) span may be very slightly off. With retenshioning required.

Bearing in mind all this is measured and checked with static engine.

Some automatically tensioned belts you are able to see the position of the pointer as the engine is running. Although this is mostly pointless due to pointer fluctuations.

I have not come across any time to just check the belt for tension as usually the resulting time taken is just shy of the time taken to change the belt and idlers. We find best practice is replace belt, tensioner and idlers along with water pump if timing belt driven.

I am not too sure if measuring either timing belt or chains while the engine is running using NVH would be too successful, due to slight bearing noise on belts and with timing chain, the tensioner is usually oil pressure fed. When noise is herd on chain its usually too late and it needs changing.

The more I am using my 4 channel pico, the more I am sure the only accurate way to check belt or chain tension is scoping the cam and crank sync.

Steven Marsh
Leyland Mill Motors

ps, Steve if you would like to send me a NVH kit FOC, I would be more than willing to supply you each and every vehicle NVH belt files for your research into this :lol:
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Re: NVH kit accelerometer

Postby Steve Smith » Thu Aug 13, 2015 11:47 am

Thank you for the feedback Steven, much appreciated.

The offer to send in numerous NVH files is intriguing too, but first we must feed this into the Ideas Funnel.

Here we look at all the options/alternatives (Cam Crank correlation for example) from a technical point of view and then the implications from a business point of view (of which I know very little)

I sincerely hope that does not sound like a "throw away line" for everyone's input here. I can assure all its documented and posted internally and will be reviewed at some point.

Thanks again, take care.......Steve
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