Re:Re:Show us your homemade Test Equipment

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07 May 2021 13:03 #48704 by Ben
Replied by Ben on topic Re:Show us your homemade Test Equipment
Here's another 1 on a rear wheel drive Lincoln front wheel bearing is bad sounds like it's coming from drivers on road test but load test says passenger. spinning front wheel by hand you can hear there is bearing noise from right side and just a slight rotor scrape on left side. hooked up the chassis ear and listening with headphones cannot tell which bearing is making noise (I was suprised as I could hear it without headphones) hooked it up to chassis ear and spinning left side with rotor scrape is 1st frame 2nd and 3rd is spinning right side

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07 May 2021 16:37 - 07 May 2021 18:00 #48711 by Wightscope
Replied by Wightscope on topic Re:Show us your homemade Test Equipment
I have seen a clever trick with a stethoscope on an oscilloscope which is to look at the frequency peak of the sound then you can match it to the crank, valvetrain, a wheel a particular pulley or whatever.
So at 1200rpm a sound at 10Hz is going to be valvetrain as the cams rotate at half the speed of the crankshaft, or maybe an idler pulley bearing - if it is 2/3rds of the size of the crank pulley will make a noise at 13.3Hz
There must be a simple way of detecting which wheel bearing it is by seeing if the frequency goes up or down when turning a corner...
Last edit: 07 May 2021 18:00 by Wightscope.

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07 May 2021 17:03 #48712 by Ben
I love the idea of using frequency to diag how fast it's moving sadly I decided to save a few bucks and bought the autel scope rather than the picoscope..... and as luck would have it they dont support frequency yet....

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07 May 2021 17:16 #48713 by Wightscope
Replied by Wightscope on topic Re:Re:Show us your homemade Test Equipment
It's a lot of bucks difference!
My wallet is not yet recovered from the delivery yesterday of a fresh 4425A with it's fancy leads. I was indecisive about it, then a standard kit came up on ebay - 2 months old, like new for 20% off the new price, quick chat with the seller and done. It's perfect -only one of the leads had ever been out it's bag.
Still undecided about Pico 7 but I think that is just familiarity.
But yea that's a lot of time to sell, I tend to reach for the scope a lot - especially as I'm doing a few classics at the moment.

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07 May 2021 17:33 #48714 by Ben
Nice!

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09 May 2021 09:41 #48745 by juergen.scholl
Replied by juergen.scholl on topic Re:Show us your homemade Test Equipment

So at 1200rpm a sound at 10Hz is going to be valvetrain as the cams rotate at half the speed of the crankshaft, or maybe an idler pulley bearing - if it is 2/3rds of the size of the crank pulley will make a noise at 13.3Hz
/quote]

The frequency in your example would be 15 hertz, not 13.3.


An expert is someone who knows each time more on each time less, until he finally knows absolutely everything about absolutely nothing.

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09 May 2021 10:52 #48749 by Matt T
Replied by Matt T on topic Re:Show us your homemade Test Equipment

So at 1200rpm a sound at 10Hz is going to be valvetrain as the cams rotate at half the speed of the crankshaft, or maybe an idler pulley bearing - if it is 2/3rds of the size of the crank pulley will make a noise at 13.3Hz


The frequency in your example would be 15 hertz, not 13.3.


An idler pulley that is 2/3 the effective diameter of the crank pulley will be rotating 50% faster. Crank is at 20Hz in the example so idler will be 30Hz if the noise only happens once per idler revolution. More likely to be a higher frequency bearing noise though.
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09 May 2021 10:55 #48751 by juergen.scholl
Replied by juergen.scholl on topic Re:Show us your homemade Test Equipment
Your correct!

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09 May 2021 11:56 #48752 by Matt T
Replied by Matt T on topic Re:Show us your homemade Test Equipment

Your correct!


I think you could've been correct too if Wightscope hadn't tricked you into using camshaft frequency.

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09 May 2021 12:07 #48753 by Wightscope
Replied by Wightscope on topic Re:Show us your homemade Test Equipment
I'll be more careful about my casual examples next time !

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05 Jun 2021 21:40 #49352 by Ben
Alright got another 1 today with the chassis ear on a diesel injector and a pulse sensor in the radiator . This 1 happens to be on my poor severely overheated lawn mower.....

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05 Jun 2021 21:42 #49353 by Ben
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05 Jun 2021 21:47 #49354 by Ben
The sync is on injector #2 I'm not sure what degree they fire in relations to crank angle so I just marked the peak pressure and divided( I measured 180 degrees from pulse to peak but I believe this is direct inject and not above the intake valve?)

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05 Jun 2021 21:48 #49355 by Ben
Setup

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11 Jun 2021 08:27 #49407 by Noah
Is it stupid that I'm impressed by your commercial grade lawn mower?

-Seems to me that I could live my life, a lot better than I think I am.
I guess that's why call me The Working Man.-

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