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Aerodynamic rattle In truck mirror

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Aerodynamic rattle In truck mirror

Old 2nd Dec 2018, 05:52
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Aerodynamic rattle In truck mirror

sort of related to aviation...

A mate's Isuzu truck's left mirror rattles suddenly and harshly when the speed reaches 100kmh.
If I wind the passenger window down, the rattle ceases. If I place a wedge of corrugated cardboard in the gap between main mirror and frame it temporarily cures the rattle.

It's a very "deep" and violent rattle causing the main mirror to shiver.

And the rattle is intermittent it doesn't ALWAYS happen at the speed limit, but If the road turns through a quartering crosswind at 100kmh the rattle starts again.

I am suspecting a broken mounting in there somewhere.

We remove the eleven or so torx scews that the main cover mounts to, in order to reveal the innards.

No broken mount... but the insulated cover of the power lead is fairly loose and looks to have some witness marks on it from vibrating against something...

We remove the right mirror's cover to compare the routing of the power lead and see it is routed differently to the left mirror, obviously a repair has been made badly, of the mirror was manufactured (in Australia) on a Friday...

Each lead has two connector blocks on it for the wide angle mirror as well as the main mirror's power. These are floating about inside the mirror cavity.

Re-rout the left power lead to match, zip tie the lead to the frame on both sides for insurance.

Replace the covers and test drive, 100kmh, no vibrations, nods of superiority and satisfaction all round.

The beer is going to taste better tonight.

Increase speed to 110kmh, rattle returns....WTF? No rattle from the RHS I hasten to add.

I'm all for zip tie bondage on the lead, but old mate says he's speed limited to 100kmh...
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Old 2nd Dec 2018, 05:59
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Did you mean to put this in the "The really boring and totally pointless snippets" thread?

Really? Are you sure?
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Old 2nd Dec 2018, 06:02
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I thought it was interesting....
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Old 2nd Dec 2018, 06:51
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the mirror was manufactured (in Australia) on a Friday...
Take the van back and insist on one made on a Wednesday.
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Old 2nd Dec 2018, 08:00
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Photos and a vid please!
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Old 2nd Dec 2018, 08:10
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The term I coined is Profile Fault. There are three approaches. Do what your mate says and avoid that speed (the pragmatic approach). Take it apart, fix, check, dismantle, fix, check etc (the OCD approach because it's there), Or take is apart, drive at 110 km/m, and reassemble, (Darwinism).

Or get a new truck.
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Old 2nd Dec 2018, 10:19
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You could take it to a lab with a wind tunnel and a shaker board and install sensors to determine the conditions under which the issue presents itself.

Or just buy a new mirror assembly.
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Old 2nd Dec 2018, 11:01
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Or buy your mate some earplugs?
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Old 2nd Dec 2018, 11:13
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Maybe the cable re-routing was to shift the resonance from 100kph to 110kph?
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Old 2nd Dec 2018, 11:26
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This will solve it. And reduce block fuel.
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Old 2nd Dec 2018, 11:36
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Well if jamming in a piece of card stopped it, it was unlikely to be the internal wiring, up more likely a resonant frequency in the mirror or turbelence around the mirror causing it to vibrate against the frame. In which case investigate the glass ball/pivot joint for slack or even the tightness of the entire mirror to truck fixing nuts.

Conversely, if space permits, a strip of soft insulating tape between the mirror and cowl to do the same job as the piece of card on a more permanent basis.
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Old 2nd Dec 2018, 11:59
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Originally Posted by cattletruck View Post
Take the van back and insist on one made on a Wednesday.
Wednesday's are for installing the dashboard rattle.
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Old 2nd Dec 2018, 12:04
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Originally Posted by WingNut60 View Post
Did you mean to put this in the "The really boring and totally pointless snippets" thread?

Really? Are you sure?

Nice.

Be thankful that engineers asked themselves exactly the OP sort of question when they were developing the car YOU own; to make it quiet, smooth and refined to drive. Unless you drive a clapped-out wreck and cannot appreciate good engineering?

Ditto your tablet, your phone, your washing machine, your TV..................

To the OP; Try putting some extra mass in the mirror housing, such as putty or similar? Or some weights glued in. That should change the resonant frequency, which might stop the problem?
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Old 2nd Dec 2018, 12:17
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Once had a motorbike whose rear light kept failing. Took it into the lab at work to see what was going on, hooked up all sorts of electronic test gear. But it was mechanical - at a particular engine speed the rear number place resonated and shook the lamp filament to pieces. Fix: replace the two bottom number plate mountings, which were fixed tight nuts and bolts, with long bolts, lock nuts and separating rubber grommets, end of problem.

Once had a colleague whose new (company) car had a horrible vibration at 75mph. Took it back to the garage. "You discovered this driving in Germany did you?" - no, he hadn't. They refused to investigate as (a) my mate couldn't legally have discovered that there was a problem, and (b) the garage didn't have anywhere they could legally drive at 75mph to investigate the "fault". Complained to boss about the inadequate service being provided by the company's contracted garage. Boss laughed.
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Old 2nd Dec 2018, 14:40
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Complained many years ago that my Sierra had a prop shaft vibration at 135 mph.
Got it fixed under warranty.
But I couldn't prove out the fix until the following year's holiday in Germany.

Thereafter, FType was not awakened as we passed through 135 mph to utter her advice of "Slow Down!"
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Old 2nd Dec 2018, 16:46
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I don't own this space under my name. I should have leased it while I still could
 
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GTW, interesting. I had a second hand Honda moped. The fuel tank cracked on the bottom. I got a second hand tank from a friend 's bike. In due course the fuel tank cracked again. As it could not be repaired by welding I made a patch of araldite and shirt fabric. It didn't crack.

I guess the glue patch could flex. Either all Honda had a resonance problem or my bike did. I didn't think to investigate.
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Old 2nd Dec 2018, 19:22
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Pontius, Uplinker and Orac, your thoughts "mirror' my own....

(sorry)
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Old 2nd Dec 2018, 20:54
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Originally Posted by Uplinker View Post



Nice.

Be thankful that engineers asked themselves exactly the OP sort of question when they were developing the car YOU own; to make it quiet, smooth and refined to drive. Unless you drive a clapped-out wreck and cannot appreciate good engineering?

Ditto your tablet, your phone, your washing machine, your TV..................

To the OP; Try putting some extra mass in the mirror housing, such as putty or similar? Or some weights glued in. That should change the resonant frequency, which might stop the problem?
Yeah, right.

My LH mirror rattles. My RH mirror does not.
Must be an engineering design flaw in the mirror.

May I take this opportunity to introduce you to Brother William of Ockham.
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Old 2nd Dec 2018, 23:42
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Have you tried turning up the radio?
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Old 3rd Dec 2018, 00:49
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Have you spoken to a dealer? Even if the car is well out of warrantee, they often know straight off what is causing a problem and can tell you how to sort it out.

I replaced the (perfectly satisfactory) mirrors on my Mazda ute with a pair of these:



I got them so I could see past the box body on my ute which was wider than the standard mirrors, as well as for towing a large (wide) boat, but they also represent an alternative design if you can't get the genuine Isuzu mirrors right.
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