I got to play with my Pico NHV in a real situation for my first time
I got to play with my Pico NHV in a real situation for my first time. We do a fleet of funeral cars and this VE statesman Hearse had a uni joint replaced by my Dr Death Mechanic who only lasted 3 weeks with me. So I was very aware that the reason for this vehicle having a server vibration at 80 kmh had to be something he did.
Anyhow after pulling out the uni joint and seeing it was good and refitting the tail shaft I used my NHV on a highway road test. My first issue with this tool is the buffer recording time is hopeless there is no time and unless you have a passenger with you by the time you pull over it is too late as you have lost the collected data.
Any how I saw enough of the screen to see I had a P1 vibration but I also had a higher than normal T1 and T2 (not as high as my T1) and T3 (again not has high as my T2) But it was the P1 I was concerned about as it was my most intense vibration graft I had and of cause were my most concern was. It was disappointing I could only glance at the screen and even trying to hit the space bar would not freeze the capture. The only way to stop the capture is by having the mouse on the stop button which is not possible when driving.
Anyhow I had seen the prof I needed and I know I have a tailshaft balance issue due to my NHV so I was still happy that I did this test and this meant I could go back to my workshop and give 100% attention to my tailshaft. I am always conscious to mark a tailshaft whether a single or 2 piece shaft it is not worth the risk of messing up the position of a shaft. But how do I know if my previous staff had the same values as I have, so it was a no brainer to rotate the shaft 180 deg.
This time on my next road test I brought a staff so they could stop my NHV capture when the vibration happens. This way I would be able to better study this capture. Well this time there was no vibration and the problem was solved. Because this vehicle is a hearse the vehicle and its tailshaft have all be stretched making the tail shaft much more acceptable to vibrations if it is not properly in balance.
I found it interesting after studying the new capture had very little amplitude with my T1, T2,T3 as was the case when the tailshaft was causing the server vibration. This makes me realise how important to only concentrate on the most notable amplitude graft which in my case was the P1. I suspect the tailshaft was causing the vibration to travel to the wheels which is why my wheel vibrations were at the time higher.
NVH is an amazing tool. I use ours here at the dealership all the time. I am actually the only tech that does. I use it for TCC concerns, engine, and of course vibrations. I have gotten decent with it, like any other tool it takes time and data can be up to interpretation depending on quite a few variables. I know there are some guys on here that are doing awesome things with NVH for diagnostic purposes.
Yes Andrew I can see how useful this tool is and it takes the guessing out of the equation. You either know if the vibration is driveshaft speed or not.
I have a case study I am putting together right now about a fuel system issue on a Duramax. Hopefully I will have it finished in the next few days. The NVH tool helped isolate the issue for me. I still got a lot to learn with it, but the more and more I get to use it... the more I like it!
My knee-jerk reaction is that you have tapping enabled on the touch-pad of your laptop and accidentally zoomed in on the window, therefore your display time is seemingly short.
I believe the default collection time is 50 seconds, which should be more than adequate to capture, pause and review; although having a co-pilot is by far safer.
Correct Matt, the default is 50 seconds with a maximum of 500 seconds. I usually prefer to set the time for ~100 seconds to get a good feel for drive through, coast down and accurately capturing the event through its worst range, with markers set to identify the range that accurately reflects the area of customer concern.
FWIW, for GM dealership technicians dealing with a warranty vibration concern, a capture may be required to be mailed to TAC for analysis/assistance. Without a proper customer concern description noted during set up and accurate markers identifying the area of concern, no assistance is likely to be forthcoming.
Thanks matt, my big problem is I had to go on the motorway and there is nowhere one can pull over and by the time you exit the motor way the whole screen has refreshed and event has passed.
Since I don't have the Pico tool, I have no clue what T1, T2, T3, and P1 are. Would you mind filling in those of us that may consider buying it in the future?
I just happened to purchase the NVH for android app when it went on sale for $100, and I have used it for several vibration diagnostics, and it has turned out very handy. A few months ago, I had a Caravan with a vibration between 55-60 only, and it was there whether accelerating, cruising, or decelerating. The app determined that it was a 3rd degree tire rotation vibration issue, which is 3 times per tire revolution. Knowing that these had tripod style inner joints, I replaced the right axle, because the vibration felt worse on that side. Vibration better, but still there. replaced the left axle, and no more vibration, and a very satisfied customer, because nobody else could figure it out.
T is tire, P is propshaft, E is engine, 1 is once per rev, 2 is twice per rev, etc... 😎
Hi Sean. Stephen already responded with the orders of vibration for tires and prop shaft that are the standard known algorithms. Those will be the default displayed values. However, with the Pico, you can also select other vibration orders and unknown orders.
FYI, here's some screen shots below of an induced engine vibration on an '06 Solstice. One image shows the individual axis values for each of the 3 axis sensor, while another image shows the default (aka consolidated) view measurement of the same condition. While the basic presets are what we see displayed on the screen, the user can select and de-select vibration orders as shown in the image with the "Add a Vibration" selection screen open . This feature can be useful when dealing with engine vibration orders associated with specific systems, such as active fuel management.
You may alsofind some interesting user information at this link. picoauto​.​com/download/docum…​.​pdf
Well done Sean and great buying, $100 you made it back on first diagnostic. Technology is changing the way we work on cars, who would have expected 10 or 20 years ago we would be diagnosing vibrations using an oscilloscope.
Hi Maurice. It is good to see that you are enjoying the PicoScope NH kit and putting it to good use.
Below is a screen capture of a 1st order drive line imbalance on an '07 Chevrolet Silverado 2WD, that shows the drive line vibration effects on T1, T2, T3, E1 and P2 Vibration Orders. Note that these are milli g and micro g values
With the prop shaft imbalance reduced to an in spec value using the hose clamp method as shown, the tire orders were no longer anything more than trace values.
- Hi Martin Really appreciate your input, I have only just started and I know I am still very green in my experience using the NHV but I hope to get up to speed over the next couple of years. Having people around me like you will certainly be reassuring if I am ever unsure of something.
- I have not looked into the balancing side of Pico yet, I see you have a capture you sent me, I think I have to purchase other NHV equipment to be able to do this, but it sounds like something I would like to do.
- I have a microphone in the NHV kit but I am unsure of how to set this up and how to use the microphone. I am sure it is not that hard, but when I tried the software only gave me a accelerometer drop down selection, not a microphone. I had a drive belt idler bearing noise today in the front of a engine, I was hoping to play with the mic but was not understanding the set up so we just found the area using the old fashion stethoscope.
Great to see you getting the NVH kit and putting it to good use. I think we can all agree that NVH is not the easiest of subjects but one that is becomingly increasingly popular, especially with more and more Electric and Hybrid vehicles on the road.
I just wanted to touch on a couple of things here as I could be typing for days! You mentioned here that you couldn't stop the scope without pressing 'Stop.' You should find that the NVH software will allow the user to hit the space bar to stop the recording much like we can do in PicoScope 6 Automotive. This should help when on a road test but the safest way is to take another person with you, but I know from experience that this isn't always possible.
The next point you made was the signal history. I believe both Matt and Martin have mentioned that the default time is indeed 50 seconds and for the majority of the time this is enough to capture the data you need. However, we can increase this to a maximum of 500s if needed. Please be aware though that when capturing this amount of data it takes a lot longer to analyse and the files can get big! In order to change the settings you need to enable the advanced features which you can find under Options>Advanced Options>Features. You can then tick the box which will allow you to change to signal history time on the setup screen. You can see this on the mic setup attachment I've added.
This mic setup picture will hopefully help you another question you asked regarding using the mics. I'm hoping that this helps explain but do get in touch if you are still having problems and we can assist you more directly.
Finally, don't forget the NVH help within the software. It might not have all the answers to your questions but it might help you when you're in battle! There is also help if you hover the mouse pointer over a recognised T, E or P vibration that will give you quick overview of what it is with link to the help page.
I cannot stress enough though that this is a tough subject and nothing can take away the requirement for good training.
Keep up the good work guys! Love seeing Pico being put to good use and getting the results we need!
Thanks Ben much appreciated, I will do some more playing with this great tool and get myself a lot more fluent in understanding and using this great tool.