Menu
Home
Forums
New posts
Search forums
What's new
New posts
Latest activity
Members
Current visitors
Log in
Register
What's new
Search
Search
Search titles only
By:
New posts
Search forums
Menu
Log in
Register
Reply to thread
Click here to become an Official Member of BMW Club Malaysia
Download Form
Home
Forums
The BMW Range
3 Series
E36
e36 328 ownership experience
JavaScript is disabled. For a better experience, please enable JavaScript in your browser before proceeding.
You are using an out of date browser. It may not display this or other websites correctly.
You should upgrade or use an
alternative browser
.
Message
<blockquote data-quote="Lee36328" data-source="post: 253030" data-attributes="member: 113"><p>Vibration hunting - harmonic resonance and damping</p><p></p><p><strong>Symptoms</strong><p style="margin-left: 20px"> A vibration that is rpm-specific. Occurs at regular stepped intervals of the rpm, for example 1,250 rpm, 2,500 rpm, 3,750 rpm, 5,000 rpm and so forth.</p> <p style="margin-left: 20px"></p> <p style="margin-left: 20px">1 x 1,250 rpm = 1,250 rpm</p> <p style="margin-left: 20px">2 x 1,250 rpm = 2,500 rpm</p> <p style="margin-left: 20px">3 x 1,250 rpm = 3,750 rpm</p> <p style="margin-left: 20px">4 x 1,250 rpm = 5,000 rpm</p> <p style="margin-left: 20px"></p><p><strong>Potential culprit</strong><p style="margin-left: 20px"> Resonance. <a href="http://en.wikipedia.org/wiki/Resonance" target="_blank">http://en.wikipedia.org/wiki/Resonance</a></p> <p style="margin-left: 20px"></p> <p style="margin-left: 20px">Wiki - In <a href="http://en.wikipedia.org/wiki/Physics" target="_blank">physics</a>, <strong>resonance</strong> is the phenomenon of producing <u><strong>large amplitude of vibrations by a small periodic driving force.</strong></u> It is the tendency of a system to <a href="http://en.wikipedia.org/wiki/Oscillate" target="_blank">oscillate</a> at maximum <a href="http://en.wikipedia.org/wiki/Amplitude" target="_blank">amplitude</a> at a certain <a href="http://en.wikipedia.org/wiki/Frequency" target="_blank">frequency</a>. This frequency is known as the system's <em>resonance frequency</em> (or <em>resonant frequency</em>). </p> <p style="margin-left: 20px"></p><p><strong>The affected parts</strong></p><p><strong></strong><p style="margin-left: 20px"><img src="http://bmwfans.info/original/images/971_p.png" alt="" class="fr-fic fr-dii fr-draggable " style="" /></p> <p style="margin-left: 20px"></p> <p style="margin-left: 20px">Diagram Item No. 1. AGGREGATE SUPPORT WITH OIL FILTER</p> <p style="margin-left: 20px"></p> <p style="margin-left: 20px"> Here's what it looks like broken.</p> <p style="margin-left: 20px"></p> <p style="margin-left: 20px"><img src="http://i51.photobucket.com/albums/f369/L36328/repairs/IMG_2943.jpg" alt="" class="fr-fic fr-dii fr-draggable " style="" /></p> <p style="margin-left: 20px"></p> <p style="margin-left: 20px"><img src="http://i51.photobucket.com/albums/f369/L36328/repairs/IMG_2944.jpg" alt="" class="fr-fic fr-dii fr-draggable " style="" /></p> <p style="margin-left: 20px"></p> <p style="margin-left: 20px"><img src="http://i51.photobucket.com/albums/f369/L36328/repairs/IMG_2945.jpg" alt="" class="fr-fic fr-dii fr-draggable " style="" /></p> <p style="margin-left: 20px"></p><p><strong>Potential Effects of Harmonic Resonance</strong></p><p><strong></strong><p style="margin-left: 20px"> The power steering pump is attached to the aggregate support shown above. The periodic pulses from the power steering pump and the engine (and to a lesser extent, other rotating parts such as alternator) can build upon themselves (resonate) and result in a level of vibration with sufficient amplitude (energy) to damage the aggregate support (shown above). With the cracked support, vibration from the power steering pump is increased resulting in increased resonance. </p> <p style="margin-left: 20px"></p> <p style="margin-left: 20px"><strong>What it means to you : </strong>Excessive vibrations from this area may be mis-diagnosed as a faulty power-steering pump, resulting in a costly replacement that does not rectify the problem.</p> <p style="margin-left: 20px"></p> <p style="margin-left: 20px">Other chassis components may also be broken as a result, for example the front axle support, shown below.</p> <p style="margin-left: 20px"></p> <p style="margin-left: 20px"><img src="http://bmwfans.info/original/images/103613_p.png" alt="" class="fr-fic fr-dii fr-draggable " style="" /></p> <p style="margin-left: 20px"></p> <p style="margin-left: 20px">Diagram Item No. 1. FRONT AXLE SUPPORT</p> <p style="margin-left: 20px"></p> <p style="margin-left: 20px">In this example, the mounting points of the engine mount to the axle support has started to crack on the right and has completely failed on the left. </p> <p style="margin-left: 20px"></p> <p style="margin-left: 20px"><img src="http://i51.photobucket.com/albums/f369/L36328/repairs/IMG_2939.jpg" alt="" class="fr-fic fr-dii fr-draggable " style="" /></p> <p style="margin-left: 20px"></p> <p style="margin-left: 20px">Below : Complete failure of the left mounting point.</p> <p style="margin-left: 20px"></p> <p style="margin-left: 20px"><img src="http://i51.photobucket.com/albums/f369/L36328/repairs/IMG_2937.jpg" alt="" class="fr-fic fr-dii fr-draggable " style="" /></p> <p style="margin-left: 20px"></p> <p style="margin-left: 20px">Below : Cracks beginning to appear on the right mounting point.</p> <p style="margin-left: 20px"></p> <p style="margin-left: 20px"><img src="http://i51.photobucket.com/albums/f369/L36328/repairs/IMG_2936.jpg" alt="" class="fr-fic fr-dii fr-draggable " style="" /></p> <p style="margin-left: 20px"></p> <p style="margin-left: 20px">As a result, instead of being secured, there is free play where the engine mount bolts to the axle support. The engine mount cannot fully dampen the engine vibrations as intended and some vibration and noise filter into the passenger cabin.</p> <p style="margin-left: 20px"></p><p><strong>Other related areas - Engine Vibration Damper</strong></p><p><strong></strong><p style="margin-left: 20px"><img src="http://bmwfans.info/original/images/161_p.png" alt="" class="fr-fic fr-dii fr-draggable " style="" /></p> <p style="margin-left: 20px">Diagram Item No. 1. VIBRATION DAMPER</p> <p style="margin-left: 20px"></p> <p style="margin-left: 20px"> The function of the vibration damper is to dampen the natural harmonic resonance of the engine. If this damper is worn out, the engine will also resonate at specific frequency (rpm) intervals. This is another area to check when investigating engine vibrations.</p> <p style="margin-left: 20px"></p><p>So, the next time you feel your car is vibrating excessively, you may want to check out these areas.</p></blockquote><p></p>
[QUOTE="Lee36328, post: 253030, member: 113"] Vibration hunting - harmonic resonance and damping [B]Symptoms[/B][INDENT] A vibration that is rpm-specific. Occurs at regular stepped intervals of the rpm, for example 1,250 rpm, 2,500 rpm, 3,750 rpm, 5,000 rpm and so forth. 1 x 1,250 rpm = 1,250 rpm 2 x 1,250 rpm = 2,500 rpm 3 x 1,250 rpm = 3,750 rpm 4 x 1,250 rpm = 5,000 rpm [/INDENT][B]Potential culprit[/B][INDENT] Resonance. [URL]http://en.wikipedia.org/wiki/Resonance[/URL] Wiki - In [URL="http://en.wikipedia.org/wiki/Physics"]physics[/URL], [B]resonance[/B] is the phenomenon of producing [U][B]large amplitude of vibrations by a small periodic driving force.[/B][/U] It is the tendency of a system to [URL="http://en.wikipedia.org/wiki/Oscillate"]oscillate[/URL] at maximum [URL="http://en.wikipedia.org/wiki/Amplitude"]amplitude[/URL] at a certain [URL="http://en.wikipedia.org/wiki/Frequency"]frequency[/URL]. This frequency is known as the system's [I]resonance frequency[/I] (or [I]resonant frequency[/I]). [/INDENT][B]The affected parts [/B][INDENT][IMG]http://bmwfans.info/original/images/971_p.png[/IMG] [/INDENT][INDENT]Diagram Item No. 1. AGGREGATE SUPPORT WITH OIL FILTER [/INDENT][INDENT] Here's what it looks like broken. [/INDENT][INDENT][IMG]http://i51.photobucket.com/albums/f369/L36328/repairs/IMG_2943.jpg[/IMG] [/INDENT][INDENT][IMG]http://i51.photobucket.com/albums/f369/L36328/repairs/IMG_2944.jpg[/IMG] [/INDENT][INDENT][IMG]http://i51.photobucket.com/albums/f369/L36328/repairs/IMG_2945.jpg[/IMG] [/INDENT][B]Potential Effects of Harmonic Resonance [/B][INDENT] The power steering pump is attached to the aggregate support shown above. The periodic pulses from the power steering pump and the engine (and to a lesser extent, other rotating parts such as alternator) can build upon themselves (resonate) and result in a level of vibration with sufficient amplitude (energy) to damage the aggregate support (shown above). With the cracked support, vibration from the power steering pump is increased resulting in increased resonance. [B]What it means to you : [/B]Excessive vibrations from this area may be mis-diagnosed as a faulty power-steering pump, resulting in a costly replacement that does not rectify the problem. Other chassis components may also be broken as a result, for example the front axle support, shown below. [/INDENT][INDENT][IMG]http://bmwfans.info/original/images/103613_p.png[/IMG] [/INDENT][INDENT]Diagram Item No. 1. FRONT AXLE SUPPORT [/INDENT][INDENT]In this example, the mounting points of the engine mount to the axle support has started to crack on the right and has completely failed on the left. [/INDENT][INDENT][IMG]http://i51.photobucket.com/albums/f369/L36328/repairs/IMG_2939.jpg[/IMG] [/INDENT][INDENT]Below : Complete failure of the left mounting point. [/INDENT][INDENT][IMG]http://i51.photobucket.com/albums/f369/L36328/repairs/IMG_2937.jpg[/IMG] [/INDENT][INDENT]Below : Cracks beginning to appear on the right mounting point. [/INDENT][INDENT][IMG]http://i51.photobucket.com/albums/f369/L36328/repairs/IMG_2936.jpg[/IMG] [/INDENT][INDENT]As a result, instead of being secured, there is free play where the engine mount bolts to the axle support. The engine mount cannot fully dampen the engine vibrations as intended and some vibration and noise filter into the passenger cabin. [/INDENT][B]Other related areas - Engine Vibration Damper [/B][INDENT][IMG]http://bmwfans.info/original/images/161_p.png[/IMG] Diagram Item No. 1. VIBRATION DAMPER [/INDENT][INDENT] The function of the vibration damper is to dampen the natural harmonic resonance of the engine. If this damper is worn out, the engine will also resonate at specific frequency (rpm) intervals. This is another area to check when investigating engine vibrations. [/INDENT]So, the next time you feel your car is vibrating excessively, you may want to check out these areas. [/QUOTE]
Verification
Post reply
Home
Forums
The BMW Range
3 Series
E36
e36 328 ownership experience
Top
Bottom
