VAP

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So far in testing I've ruined 41 brand new OEM Boge strut mounts. Some via bad CNC entry typos, measurements a few thousandths off, some from other unintentional screw-ups and some, like today as a direct result of intentionally trying to fail them.

In my first series of testing this morning I was conducting such tests on mounts with spherical bearings and with/without Mount-Savers installed trying to see if opening the mount floor bore from the stock diameter of 20mm to 28mm so the sphericals had a good shoulder to rest on that would hold the load and provide a seat to nestle into once pressed in as well as plenty of room at the top of the mount for the strut threaded shaft and cupped washers to rotate orbitally/radially within the strut mount cavity at the strut tower.

So I mount one in one of my spare strut tower plates I cut out of 2 cars in the junkyard. Place it upside down in the press and start monitoring the hydraulic pressure gauge thats hooked up to a 1" diamter ram and gives me an accurate psi read-out from 0-50 tons. Well I'm steadily increasing the pressure on the mount until just past 12 tons and just at/over 12.2 tons, KABOOM!!! Small objects on the nearby work bench toppled. Round objects rolled off the table on to the floor and the pressure lever I use went slack along with "0" indicated pressure on the gauge. WTF!?! My ears are still ringing as I had the garage door closed to try and keep it cool inside.

I pull the mount and it looks fine... nothing visibly apparent at all. So I mount it back up in the fixture and place the press arbor inside and it pushes the mount fully collapsed with "0" indicated psi and no resistence felt on the press lever. WTF!?! Pull it out and again there's nothing immediately apparent. So 3rd time being the charm I try again only s-l-o-w-l-y this time while watching it. Its definately collapsed but I cannot see where or how. So I rotate the mount 45* a couple of times while pressing and VOILA!! There it is! I've split the outer steel reinforcing ring that surrounds the inner steel bearing cup. This is what happens when the OEM mount bottoms out hard against the the strut tower top. And if you release the weight off it (or remove it from the car) it closes the gap back up and is virtually impossible to see/detect because its totally encased in rubber. Only reason its visible in this pic is because I'm pressing down on the mount spherical bearing in the arbor press all the way to the strut tower surround-ring. The inner (green) bearing shell should NEVER be "inside" or "below" that outer rubber encapsulated steel sleeve as it is in this picture. That is a war the green/thicker inner steel sleeve will win EVERY time due to being over 5x thicker than the outer steel sleeve!! The outer sleeve appears thick but thats simply a rubber coating. The inner sleeve simply splits then blows the outer sleeve apart on hard suspension compression. BTW, with Mount-Savers installed this is dramatically less likely to occur because compression travel is both dampened as well as reduced/limited. I havent been able to induce this failure with an MS installed until just at 27 tons of pressure. Its only an issue with an un-reinforced stock, OEM mount. And I've got a strong gut-level hunch the generic mounts are even weaker at this spot.

Got me wondering how many collapsed mounts are directly related to this phenomenon occurring when a serious bump/pothole is encountered. Probably wouldnt even feel it occur beyond the bone-jarring bump but the strut mount could easily be toast at that point yet still have some small percentage of elasticity and re-bound capability but now would start an accelerated downward spiral into complete failure
with total collapse looming large and eminent on the not-too-distant horizon.

Worst part is you'll likely never be able to find this fracture/split on the mount without some method that forces it open wide enough to see a gap.

Ok, I'll go try and ruin another 10-12 mounts before the days over and I'll post pics of any other interesting snippets or surprises.

Actually, intentionally breaking stuff is kinda fun. Usually only scarey if it goes KABOOM when you werent expecting it ;-)

VAP

Which confirms two things, ie; the static dynamic load limit of this steel ring is right at 24,000psi. And secondly that the first test was not a fluke, weak steel ring, surface flaw or other contributing structural cause in that steel ring failing. Now since I know the weak link and that the Mount-Saver extends that range by a factor of over 50% (tested/confirmed) I'll back down to 10 tons/20,000psi on any/all "strut mount only" testing.

BTW spherical bearing seat held to over 27 tons before shearing itself away from the stamped bearing shell and blowing thru the top of the mount which is the exact same psi that the stock diameter seat started to deflect and bend upwards. Definately no weaker and with GOBS of strength to spare. Good test on that aspect!

audifreakjim

Mance, I demand a webcam!

YucatanAudi

Where can we get ahold of these mount savers...?

CrazyCab

Whether on purpose or accident.

VAP

the only bad thing is never knowing when the BOOM is gonna come. And that makes it a bit surprising/startling every time. Its also a little loud for a closed garage and I cant wear my noise-canceling headset as I need to hear the sounds of rubber ripping/shredding as it too is a key structural component in OEM mount testing.