Crazy prices from Mercedes for our old cars! - Page 3 - PeachParts Mercedes-Benz Forum

gsxr · #31 08-03-2023, 09:31 AM

@Graham, any chance you can re-post what was deleted?

@vstech, any update on who exactly deleted posts, and why?

Thanks.

Graham · #32 08-03-2023, 11:29 AM

Quote:

Originally Posted by gsxr

@Graham, any chance you can re-post what was deleted?

@vstech, any update on who exactly deleted posts, and why?

Thanks.

I can't easily re-post because I did not keep a copy and I did not get an email notification from Peachparts because it was my post.

Other than the pictures showing how I bench tested the threads on URO and original mounts, I had also researched the recommended torque for M8 bolts/nuts of various grades. This showed why low or even mid grade threads would not be able to handle the recommended MB torque.

Another issue was the depth of the threads. Recommended bolt torques are based on a depth of thread equivalent to at least the diameter of the bolt.

I had not thought about Frank's thought about how the URO threads vs the OE threads might have been formed.

Something wrong seeing that another owner and myself had the same issue - threads stripped before any real torque was applied (without getting to needing a torque wrench!)

URO Parts Support · #33 08-03-2023, 11:31 AM

@vstech Also very interested to know, please share the edit history for those two threads.

From the emailed thread notifications, here's a copy of the post that was mysteriously deleted:

Here is the message that has just been posted:
***************
In order to get car back on road, I decided only way is to drill out the stripped hole with 5/16" bit and rethread to 3/8-16. Not metric, but is nearest size.

I did a test on the old mount first. That worked out, so I removed the URO mount and brought it to bench.

Only one hole had stripped, so I decided to do a test on the second one. I used a new bolt with an oversize nut so that thread protruded same as the originals.
Image: https://www.dropbox.com/scl/fi/ibxoxnapbxdwtkoybpvvm/boltandspacer.JPG?rlkey=ch9bfawi4ksi66w8rfxmvg7np&dl=1

Image: https://www.dropbox.com/scl/fi/xaky0ziologzz5hj70jn0/torqueing.JPG?rlkey=j3x6h4bl54m0qyabzaqkv3wuu&dl=1

Image: https://www.dropbox.com/scl/fi/iwvdmrdkp8xwmps5jrtn8/trq1.JPG?rlkey=m511cbstw0nzf7q6g2r8hg4o6&dl=1

I first ran an M8 tap through hole just to clean out any dirt. Went through easily. I then screwed the new bolt into the undamaged hole by hand and finally tightened with torque wrench set to 21ft/lb.

Result - the second hole also stripped!

Conclusion- These mounts cannot take the 22ft.lb. torque spec quoted eatlier. Reason would be that the steel is not same as the Mercedes originals on which the spec was based. As an example, these are the torques for M8 bolts of different standards.
Grade 5.6 (low carbon steel) -: 8.1ft.lb; Grade 8.8 19 ft.lb.; 10.9 26ft.lb

These torques are based on full thread engagement. For an M8 bolt this means the nut or socket should be approximately 8mm thick. The mount thread area is only about 4-5mm deep, so allowable torque should only be about 1/2 of the published bolt torque.

MB probably did the calculations, but they must have been based on a high strength steel.

I would suggest that URO do the same test that I just did. I think they will find that the mount cannot accept the alldata spec quoted. Then redesign with a high strength steel. In other words use mechanical engineering, not Amazon returns

***************

URO Parts Support · #34 08-03-2023, 11:45 AM

From Graham's deleted post: "I would suggest that URO do the same test that I just did. I think they will find that the mount cannot accept the alldata spec quoted."

That's what our engineers did, using an known-accurate Snap-On torque wrench that had been recently tested by Snap-On and found to be within 0.5 ft-lbs of the setting.

Several of our production pieces were tested (both holes), and all stripped at almost exactly 32 ft-lbs, which is about 50% higher torque than the Alldata/factory spec. If folks follow the proper Alldata/factory torque spec, the threads don't strip. They only strip if the proper torque is exceeded by an additional 50%.

22 ft-lbs is not a lot of torque, and is easy to exceed if someone isn't using an calibrated torque wrench.

Graham · #35 08-03-2023, 11:48 AM

Using URO's post above, but with working images, this was the post. No idea how or why it disappeared, but here we are. Wonder if it will stay this time

In order to get car back on road, I decided only way is to drill out the stripped hole with 5/16" bit and rethread to 3/8-16. Not metric, but is nearest size.

I did a test on the old mount first. That worked out, so I removed the URO mount and brought it to bench.

Only one hole had stripped, so I decided to do a test on the second one. I used a new bolt with an oversize nut so that thread protruded same as the originals.
Image:

Image:

I first ran an M8 tap through hole just to clean out any dirt. Went through easily. I then screwed the new bolt into the undamaged hole by hand and finally tightened with torque wrench set to 21ft/lb.

Result - the second hole also stripped!

Conclusion- These mounts cannot take the 22ft.lb. torque spec quoted eatlier. Reason would be that the steel is not same as the Mercedes originals on which the spec was based. As an example, these are the torques for M8 bolts of different standards.
Grade 5.6 (low carbon steel) -: 8.1ft.lb; Grade 8.8 19 ft.lb.; 10.9 26ft.lb

These torques are based on full thread engagement. For an M8 bolt this means the nut or socket should be approximately 8mm thick. The mount thread area is only about 4-5mm deep, so allowable torque should only be about 1/2 of the published bolt torque.

MB probably did the calculations, but they must have been based on a high strength steel.

I would suggest that URO do the same test that I just did. I think they will find that the mount cannot accept the alldata spec quoted. Then redesign with a high strength steel. In other words use mechanical engineering, not Amazon returns

Graham · #36 08-03-2023, 11:58 AM

Quote:

Originally Posted by URO Parts Support

From Graham's deleted post: "I would suggest that URO do the same test that I just did. I think they will find that the mount cannot accept the alldata spec quoted."

That's what our engineers did, using an known-accurate Snap-On torque wrench that had been recently tested by Snap-On and found to be within 0.5 ft-lbs of the setting.

Engineer did it here too (a real P.Eng

) and the threads stripped way before any measurable torque was applied. Using exactly the same tools and method, the OE mount threads did not strip.

Nothing you say can change that. You should give up trying to defend this real issue.

URO Parts Support · #37 08-03-2023, 12:09 PM

Quote:

Originally Posted by Graham

Then redesign with a high strength steel. In other words use mechanical engineering,

If the Mercedes-Benz engineers determined the proper torque spec is 22 ft-lbs, and our mounts take 50% of additional torque (32 ft-lbs), why do you believe our mounts should be redesigned to take even more additional torque beyond the factory specification?

Should folks use the factory torque spec of 22 ft-lbs? Or should they double that and arbitrarily use 44 ft-lbs instead, because (hypothetically speaking) that's when the factory mount strips?

Graham · #38 08-03-2023, 03:06 PM

Quote:

Originally Posted by URO Parts Support

If the Mercedes-Benz engineers determined the proper torque spec is 22 ft-lbs, and our mounts take 50% of additional torque (32 ft-lbs), why do you believe our mounts should be redesigned to take even more additional torque beyond the factory specification?

Should folks use the factory torque spec of 22 ft-lbs? Or should they double that and arbitrarily use 44 ft-lbs instead, because (hypothetically speaking) that's when the factory mount strips?

See previous post #36. Give it up.

gsxr · #39 08-03-2023, 03:14 PM

If I'm reading this correctly, the URO mount had the threads strip out below the required 22 lb-ft of torque, per the info in post #35. In which case, that's a problem.

Maybe other parts on the production line survived to 50% higher torque levels, but that doesn't help the customer who did not get the "good" ones.

URO Parts Support · #40 08-03-2023, 03:44 PM

Quote:

Originally Posted by gsxr

If I'm reading this correctly, the URO mount had the threads strip out below the required 22 lb-ft of torque, per the info in post #35. In which case, that's a problem.

Maybe other parts on the production line survived to 50% higher torque levels, but that doesn't help the customer who did not get the "good" ones.

According to Graham's posts, he's never had his torque wrench tested. Powerfist 2920935 gets mixed reviews. There are many good reviews, but also reviews stating:

"Poor quality. Mine did not click out and I ended up stripping a threaded hole on my block."

"Didn't work right out of the case. I bought this to work on my motorcycle and atv based on the reviews. Unfortunately mine never clicks so you basically have no clue what torque you are using."

"Defective. Poorly made wranch. Bought this online. But the locking screw is coming out loose all the time and doesn't lock. It feels very fragile. This thing is poorly made. There is a reason for this to cheap priced."

So not only is tool accuracy a complete unknown, he re-tapped the threads in the mount first, which certainly could have cut into the production threads. "Testing" with multiple random variables isn't actually a test. There's no way to know if he received a good mount or not at this point, and we're definitely not the only folks who are thinking this.

When Graham receives the warranty replacement, hopefully he uses a professionally-calibrated torque wrench and doesn't re-tap the threads. Also replicate the full thickness of the washers and crossmember, so the bolt isn't bottoming out against the rubber blocks.

Graham · #41 08-03-2023, 03:54 PM

Quote:

Originally Posted by URO Parts Support

This thing is poorly made. There is a reason for this to cheap priced."[/I][/B]

Sounds like URO.

Drew is digging his hole even deeper. Lots of mis-information again. I wonder if the management people at A.P.A (URO's owners) read this? Very bad public relations.

tbomachines · #42 08-03-2023, 04:03 PM

Yikes, how is 22ftlbs enough to strip or pull threads in any steel? Or even 32 for that matter?

Id be tempted to throw a bit of loctite on there to make sure it doesnt back out over time/heat cycles/vibration with so little torque.

URO Parts Support · #43 08-03-2023, 04:14 PM

^ Mercedes' engineers designed the mount to support the weight of the transmission primarily, so the bolts simply locate the mount (which is in compression) laterally on the cross member. Bolt shear strength is what matters in this application, not tensile. That's why Mercedes didn't bother using welded nuts or inserts (which would have been much stronger), and simply formed threads in the holes punched the thin steel bracket.

See diagram in post #1, and how the mount is physically trapped inside the cross member valley beneath the transmission.

Graham · #44 08-03-2023, 04:21 PM

Quote:

Originally Posted by tbomachines

Yikes, how is 22ftlbs enough to strip or pull threads in any steel? Or even 32 for that matter?

Id be tempted to throw a bit of loctite on there to make sure it doesnt back out over time/heat cycles/vibration with so little torque.

Check out applicable bolting tables. This one might help:
https://www.grampianfasteners.com/files/95b2c19b-1d29-4624-abdf-0813df2db3ac/Torque_Settings.pdf
Divide Nm by 1.356 to get Ft.Lb.
For M8 bolts recommended torque is 8.1 ft.lb for Grade 4.6 and 20.95ft.lb. for Grade 8.8 steel bolts. Lower if you apply Loctite!

Graham · #45 08-03-2023, 04:34 PM

Life is too short for this crp. Solution?

"This message is hidden because URO Parts Support is on your ignore list."