IO360 M20E Engine Shock Mount evaluation

[HRM]

I suspect my engine is sagging and this causing the cooling issues I'm having. So, is it shims or is it mounts? How do you evaluate the state of the mounts? Since I just replaced the donuts (and my gawd how my landings/ground handling have improved), it may be 'time' for the mounts.

[yvesg]

This might help you. Anyone having the shims picture (figure 1) missing from this page?

http://www.donmaxwell.com/publications/MAPA_TEXT/Alining Engine Using Shims/ALIGNING_YOUR_ENGINE.HTM

 

Yves

[mike20papa]

In theory, these mounts start deteriorating from their original/optimum performance almost immediately.  After about five years they begin to really show their age.  I have even tried rotating mounts, ones in compression with ones in tension, and that helps, but heat and load just wear them out.  Ten years old & they are shot.   

[HRM]

1 hour ago, yvesg said:

Anyone having the shims picture (figure 1) missing from this page?

Yes, here's what they look like (uncut). Apparently LAZAR has the thin one, but not the thick one.

[HRM]

1 hour ago, mike20papa said:

In theory, these mounts start deteriorating from their original/optimum performance almost immediately.  After about five years they begin to really show their age.  I have even tried rotating mounts, ones in compression with ones in tension, and that helps, but heat and load just wear them out.  Ten years old & they are shot.   

Thank you! When I bought the plane everything was perfect and I have owned her for eight years. That was a lot of newbie landings ago.

Just read the engine log, Maxwell installed 'Installed 4 proper shims' in 2007 and no other engine mount entries after that. Looks like it's time.

Hints on replacement? I have a buddy A&P who will supervise and has a hoist, but 'I wanna do it'.

[carusoam]

Lord Brand not the other one.

Lords are expensive just like the donuts...

Stuff I read on MS, and have on my plane...

Best regards,

-a-

[N201MKTurbo]

Back in the 80s when I was flying my Mooney all over doing field service, I was in an oil field supply business and saw a set of Mooney motor mounts sitting on a guys desk. He said they were for a stationary engine. He looked them up and they were $40 each. They looked exactly the same and were made by Lord.

[mike20papa]

Here's a photo of mounts on my 180 hp o-360.  Old vs new.  Replaced after about 300hrs.  ..and don't ask me why cyberspace thinks these look better when viewed upside down! 

[HRM]

2 hours ago, mike20papa said:

Here's a photo of mounts on my 180 hp o-360.  Old vs new.  Replaced after about 300hrs.  ..and don't ask me why cyberspace thinks these look better when viewed upside down! 

Well, mine definitely have that squashed look. We're going to take a closer look after hoisting the engine up. To freaking cold to breathe in the hangar right now. The mounts would probably shatter if we touched them.

[RLCarter]

On 1/15/2018 at 1:06 PM, HRM said:

Thank you! When I bought the plane everything was perfect and I have owned her for eight years. That was a lot of newbie landings ago.

Just read the engine log, Maxwell installed 'Installed 4 proper shims' in 2007 and no other engine mount entries after that. Looks like it's time.

Hints on replacement? I have a buddy A&P who will supervise and has a hoist, but 'I wanna do it'.

Both of you will need to get your hands dirty, note where the shim are and put them back in the same location(s) for starters. When I did mine it took about 6hrs if I remember correctly.

[aaronk25]

On my J we replaced all the mounts and even right off the bat installed 2 lower shims, which according to instructions is the most shims you can put on it and it still in my opinion needs to come up just a hair to align perfectly with the cowl. Maybe the cowl is slightly high.....?


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[rbridges]

I replaced mine about 5 years ago.  Couldn't tell if they were in bad shape, but I knew my engine sagged a little.  You could see their glory days were over.  In fact, one of the mounts had a tear in it.  

[EricJ]

13 hours ago, aaronk25 said:

On my J we replaced all the mounts and even right off the bat installed 2 lower shims, which according to instructions is the most shims you can put on it and it still in my opinion needs to come up just a hair to align perfectly with the cowl. Maybe the cowl is slightly high.....?

Mine had shims in both top and bottom, and Maxwell moved the top shims to the bottom.   So the bottom is double shimmed and no shims on top, and it's about right.

[aaronk25]

Mine had shims in both top and bottom, and Maxwell moved the top shims to the bottom.   So the bottom is double shimmed and no shims on top, and it's about right.

Was this new mounts or existing mounts. Mine was shimmed with new mounts same as you described above.


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[EricJ]

2 hours ago, aaronk25 said:

Was this new mounts or existing mounts. Mine was shimmed with new mounts same as you described above.
 

 

 

The mounts were relatively new, about a year and 50 hours or so old.   I think the original installers just installed it by the installation diagram, which is one shim per mount, and didn't notice or care about the sag.   It sagged a LOT that way, so Maxwell moved them.   Now when the cowl is freshly put on the alignment is pretty much perfect, but after a few hours the cowl creeps up a bit.

 

 

 

[M20D6607U]

There is a trick to replace the mounts. The bolts do not go straight in the mount holes. You have to bent the mount inward to go in. I had small shims on top and thick ones on the bottom. They do fall out so be ready. Do the bottom two first and them the top's will be lined up. I had to modify a box wrench to work in the top left. A cherry picker with a pitch changer works good. 

[cctsurf]

4 hours ago, M20D6607U said:

cherry picker with a pitch changer

I'm trying to imagine how a pitch changer (by this do you mean a "load leveler") would be attached to our engines.  Would it be connected to the engine lift point (on the crankcase bolt) at the back and to the propeller lift strap at the front?

BTW, this is what I am thinking when I say "Load Leveler"

[HRM]

23 hours ago, aaronk25 said:

...and it still in my opinion needs to come up just a hair to align perfectly with the cowl.

And of course, this is the $64K question, when is it aligned? Right now, the front edge of the doghouse is so low that the seal bows up to be tucked under the top edge of the cowl. After flight, it has pulled out and leaves a gaping hole across the top. I think this is the source of my overheating. There is scant space between the spinner and the lower cowl--not rubbing yet, but awfully close.

[M20D6607U]

16 hours ago, cctsurf said:

I'm trying to imagine how a pitch changer (by this do you mean a "load leveler") would be attached to our engines.  Would it be connected to the engine lift point (on the crankcase bolt) at the back and to the propeller lift strap at the front?

BTW, this is what I am thinking when I say "Load Leveler"

Yes a load leveler, helps the angle of the dangle! And yes, attached to the engine lift point and I used a strap around the prop. 

[M20D6607U]

15 hours ago, HRM said:

And of course, this is the $64K question, when is it aligned? Right now, the front edge of the doghouse is so low that the seal bows up to be tucked under the top edge of the cowl. After flight, it has pulled out and leaves a gaping hole across the top. I think this is the source of my overheating. There is scant space between the spinner and the lower cowl--not rubbing yet, but awfully close.

If the spacers were correctly placed when the mounts were replaced prior, the engine will be higher and the proper gap restored. Such is the case with my M20D. Plus less vibration. Then have your prop balanced. It's amazing to see how much weight and pressure are on those mounts and they last as long as they do.  All the mounts should be torqued the same amount. You can tell by how many threads are left on the end of the bolt. Not to tight and not to loose. There is a torque setting for those. 

[HRM]

On 1/19/2018 at 1:13 PM, M20D6607U said:

If the spacers were correctly placed when the mounts were replaced prior, the engine will be higher and the proper gap restored. Such is the case with my M20D. Plus less vibration. Then have your prop balanced. It's amazing to see how much weight and pressure are on those mounts and they last as long as they do.  All the mounts should be torqued the same amount. You can tell by how many threads are left on the end of the bolt. Not to tight and not to loose. There is a torque setting for those. 

I pulled the cowling and doghouse off today. The lower baffle seal is sitting a good inch below the u-channel in the lower front cowl. I saw that when I replaced #2 jug a few weeks ago and I should have done the mounts then <sigh>. The upper ones are soft, is that a good sign or bad?

I need to get the hoist on it and lift it up to see if the alignment changes, but it is really looking like new mounts (~0.45 AMU) <sigh>

[carusoam]

Rubber usually gets harder over time...

Soft rubber is good for vibration adsorption...

Another example... Old pucks get harder with age and they compress over time...

Outiside of this discussion... when selecting a rubber material for the application, it is a challenge to select one that is stiff enough to hold the weight up, and soft enough to adsorb vibration.  Selecting the chemistry and cross-linking to keep the rubber from flowing over the years... and protecting it from its environment... O2, UV, heat, oil and fuels contact...

Best regards,

-a-

[HRM]

6 minutes ago, carusoam said:

Rubber usually gets harder over time...

One would think...this is why I was surprised that the uppers were soft. Of course, some rubber hardens with time, other rubber softens. Could explain the droop.

[carusoam]

Rubber, like all polymers, flows over time.  The % crosslinking is a way to adjust / retard the flow.  

• Too much X-link, There is no rubbery-ness, hard like a rock...
• too little X-link, There is just viscosity, with no rebound...

Rubber is often modeled like a spring and dash pot, in a parallel arrangement ...  a shock absorber analogy.  The viscosity in the dash pot adjust the speed of the flow.  The spring adjust the distance allowed and recovery.

In the proper time frame, even glass flows.  Centuries old cathedral glass is known to exhibit this behavior...

There is also a temperature effect that goes with all of this...

Hot environment and under a heavy load... the rubber wants to squeeze out.

Relieving the compression stress could slow the progression.  But, where is the convenience of that?

Rubber hardness is measured like other materials.  Pressing a point into it and measuring distance and force required. Getting softer over time may not be normal. It could be a sign of the chemistry breaking down, or solvents like oil being absorbed into it...

Thoughts of a ChE specializing in polymer processing, not just an ordinary PP on some days...

Best regards,

-a-

[Guest]

This might help.