Engine Shock Mounts

OkieFlyer

OkieFlyer

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Andrew L.
As I have been experiencing some excess vibration of late, I've decided to replace my engine mounts. Not sure yet where the vibe is coming from yet, but I'm going to go ahead and do the mounts. I believe my mounts are around 20 years old unless I missed something in the log book, so I figure it's time.

Never done this before so I'm curious what the differences are in the Lord and Barry mounts. Barry is about $160 cheaper per set, which isn't a ton, but it's money. I don't mind spending more for the Lords if they are better, but I don't want to buy a name either. What say you?

1962 C-182E with Cont. O-470-R
 
Before you spend money, find a mechanic that can check prop balance and do a spectrum on the engine. Lots of things can cause vibrations. I would isolate the cause first if they are that noticeable.
 
Bell206 said:
Before you spend money, find a mechanic that can check prop balance and do a spectrum on the engine. Lots of things can cause vibrations. I would isolate the cause first if they are that noticeable.
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Noted.

I had a dynamic prop balance done recently. He recommended that I replace my shock mounts at annual. That's what I'm doing. Need to decide on Lord or Barry and get them ordered before annual next week.
 
Be very careful ordering your shock mounts. I learned the hard way (went with Lord by the way) that I have two different part numbers and the mounting location is critical. This may not be the case with your Cessna. Do you own a parts manual? An engine hoist is a must.
 
Timbeck2 said:
Be very careful ordering your shock mounts. I learned the hard way (went with Lord by the way) that I have two different part numbers and the mounting location is critical. This may not be the case with your Cessna. Do you own a parts manual? An engine hoist is a must.
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Thank ya, Timbo. I'll have to look that up in the manual. We'll do it at the mechanic's shop, so we'll have all the necessary equipment.
 
just curious, why did your prop man tell you that you needed new mounts?
 
Unless they are sagging and allowing your engine to droop off center and touch the cowling at the prop shaft opening. Leave them alone.
How they look has nothing to do with how well they do their job.
 
My Glasair was sagging and the mounts were worn (10 years old). Never really noticed a vibration but after I had them replaced this year, I could tell a difference in how much smoother it is...not to mention the spinner lines up with the cowling now.
 
Tom-D said:
Unless they are sagging and allowing your engine to droop off center and touch the cowling at the prop shaft opening. Leave them alone.
How they look has nothing to do with how well they do their job.
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I've seen them sag enough that the internal spacer starts hammering at the shockmount's internal diameter, causing unusual vibration. It can show up fairly suddenly. Besides that, a 20-year-old shockmount has hardened considerably and isn't absorbing nearly as much vibration as it used to.

The OP's vibration might be from a bad sparkplug or two, or a bad mag. Weak spark can cause vibration too. It doesn't always show up on the mag check at runup.
 
OkieFlyer said:
I have been experiencing some excess vibration of late
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OkieFlyer said:
I had a dynamic prop balance done recently.
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OkieFlyer said:
Because they are looking worn out and are pretty old.
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Don't quite follow. If you just had your prop balanced and there are still "excess" vibrations, I wouldn't change a thing until you determine the source of those vibrations. And part of those vibration checks will determine if your rubber mounts have lost their dampening effect.
 
Bell206 said:
Don't quite follow. If you just had your prop balanced and there are still "excess" vibrations, I wouldn't change a thing until you determine the source of those vibrations. And part of those vibration checks will determine if your rubber mounts have lost their dampening effect.
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If the engine mounts are the source of the vibration how do you suggest determining that without changing them?

Those old rubber mounts have probably turned hard over the years, it certainly will not hurt anything to change them.
 
Grum.Man said:
If the engine mounts are the source of the vibration how do you suggest determining that without changing them?
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As I mentioned through vibration checks with balancing gear, the same gear used to balance his prop.

The mounts are mostly designed to dampen the 1/2 per, 1 per, and in some cases 2 per vibrations that are found in normal engine/prop operation. Any vibration outside those frequencies will not be dampened as much. While simply changing the mounts will give 50% of the aircraft a better ride, the new mounts may also mask the issue that is causing the vibrations.

While there are a number of methods, in general, with an accelerometer mounted on the front of the engine, back of the engine, and at a point aft of the mounts, one can determine if the mounts are dampening correctly. You can also determine the phase/frequency of the vibration and troubleshoot its location and cause.
 
Well you certainly made that overly complicated. Engine didn't vibrate before, change mounts. Vibration goes away all is good, if it does not then you have to dig deeper.
 
Grum.Man said:
Engine didn't vibrate before, change mounts. Vibration goes away all is good,
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And entirely subjective. If your average vibration level was .7 ips before, went up to .9, then went back to .7 ips and you're happy... then so am I.

But as a general comparison, it's not unusual to balance an aircraft down to .1 ips or less average vibration level which is entirely objective.
 
Does the prop look like its sagging a bit when compared to the opening in the cowling? Just curious.
 
Bell206 said:
As I mentioned through vibration checks with balancing gear, the same gear used to balance his prop.

The mounts are mostly designed to dampen the 1/2 per, 1 per, and in some cases 2 per vibrations that are found in normal engine/prop operation. Any vibration outside those frequencies will not be dampened as much. While simply changing the mounts will give 50% of the aircraft a better ride, the new mounts may also mask the issue that is causing the vibrations.

While there are a number of methods, in general, with an accelerometer mounted on the front of the engine, back of the engine, and at a point aft of the mounts, one can determine if the mounts are dampening correctly. You can also determine the phase/frequency of the vibration and troubleshoot its location and cause.
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What does one do with all of that dampness?
 
UngaWunga said:
Does the prop look like its sagging a bit when compared to the opening in the cowling? Just curious.
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I haven't noticed, and to tell you the truth, I haven't looked real hard at that.
Bell206 said:
As I mentioned through vibration checks with balancing gear, the same gear used to balance his prop.

The mounts are mostly designed to dampen the 1/2 per, 1 per, and in some cases 2 per vibrations that are found in normal engine/prop operation. Any vibration outside those frequencies will not be dampened as much. While simply changing the mounts will give 50% of the aircraft a better ride, the new mounts may also mask the issue that is causing the vibrations.

While there are a number of methods, in general, with an accelerometer mounted on the front of the engine, back of the engine, and at a point aft of the mounts, one can determine if the mounts are dampening correctly. You can also determine the phase/frequency of the vibration and troubleshoot its location and cause.
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Thank you. I'm not at all suggesting that we just change the mounts and quit. Quite the contrary actually. I'm almost 100% certain that I have an issue other than the mounts for other reasons outside of the scope of this thread. That being said, I still intend to change my shock mounts. Interestingly, after 21 posts nobody has yet made any attempt to address the question of Lord v. Barry mounts. You see, I never asked anybody if they think I should change my mounts and why, rather, I said I'm going to change my mounts and asked for guidance on which mounts to use.
 
I change my mounts every five years because typically I can see my engine starting to sag a bit.

(And considering my relatively recent divorce, get your minds out of the gutter)

Edit: and I've always bought Lord mounts. Why? Because.
 
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OkieFlyer said:
Thank you.
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You're welcome. But in context, I was responding to the first paragraph in your post:
OkieFlyer said:
As I have been experiencing some excess vibration of late, I've decided to replace my engine mounts. Not sure yet where the vibe is coming from yet, but I'm going to go ahead and do the mounts. I believe my mounts are around 20 years old unless I missed something in the log book, so I figure it's time.
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Didn't recall seeing Lord or Barry mentioned there. My bad.

Kenny Phillips said:
What does one do with all of that dampness?
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Ha. Well, right after I dry off... I'll take door #2... to dull or deaden; depress; to soundproof.
 
Dan Thomas said:
...
I've seen them sag enough that the internal spacer starts hammering at the shockmount's internal diameter, causing unusual vibration. It can show up fairly suddenly. Besides that, a 20-year-old shockmount has hardened considerably and isn't absorbing nearly as much vibration as it used to.
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Let'sgoflying! said:
20 years old? Even if they look fine, change them. They could be as hard as flint at 20 years, not much shock absorption with that.
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Grum.Man said:
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Those old rubber mounts have probably turned hard over the years, it certainly will not hurt anything to change them.
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I’m in agreement with these posts. Change the mounts. Whether they are the sole source of your issue or not, I do not know, but I’d change them due to their age and their likely hardening.
 
My mechanic just told me that my mounts looked like they are starting to sag and recommended changing them at next annual or next time we need work done. He wrote Lord Mounts on my bill so that was his suggestion. There, question answered. Albeit by someone with no real information on the subject other than a word written on a piece of paper.
 
Dan Thomas said:
I've seen them sag enough that the internal spacer starts hammering at the shockmount's internal diameter, causing unusual vibration. It can show up fairly suddenly. Besides that, a 20-year-old shockmount has hardened considerably and isn't absorbing nearly as much vibration as it used to.

The OP's vibration might be from a bad sparkplug or two, or a bad mag. Weak spark can cause vibration too. It doesn't always show up on the mag check at runup.
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Shame on you for allowing them to get that bad.. when they are still doing their job,, leave them alone.
 
When isn't good enough, good enough?
Matthew Rogers said:
My mechanic just told me that my mounts looked like they are starting to sag and recommended changing them at next annual or next time we need work done. He wrote Lord Mounts on my bill so that was his suggestion. There, question answered. Albeit by someone with no real information on the subject other than a word written on a piece of paper.
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They do sag,,and the first indication of that is the prop is no longer centered in the cowling.
 
Bell206 said:
You're welcome. But in context, I was responding to the first paragraph in your post:

Didn't recall seeing Lord or Barry mentioned there. My bad.


Ha. Well, right after I dry off... I'll take door #2... to dull or deaden; depress; to soundproof.
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No worries. The question is in the second paragraph. I know I have some work yet to do on finding the vibration. I don't know what it is yet, but we'll find it. In the mean time, the shock mounts are looking crusty and was wondering if the cheaper Barry mounts are as good as the more expensive Lord mounts. I believe the mounts I have are Barry or something other than Lord.
 
Tom-D said:
When isn't good enough, good enough?

They do sag,,and the first indication of that is the prop is no longer centered in the cowling.
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I'll have to look more closely at that. I haven't noticed a sag, but it's not something I look closely at either. I reckon I will from now on though.
 
Tom-D said:
Shame on you for allowing them to get that bad.. when they are still doing their job,, leave them alone.
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I didn't let them get that bad. Other mechanics did. Mechanics who propose that 20 years old and showing sag was OK. I merely mentioned that they can sag enough that they start striking the internal spacer against the mount cup, causing unusual vibration. It isn't just sag, of course, that is an issue. Propeller reaction torque twists the engine on those mounts, and if they're shot they won't stop that internal interference.
 
Lord vs Barry = 6 vs half dozen (IMO). I think the Barry mounts are less expensive and are commonly used on EAB aircraft.
 
Tom-D said:
Shame on you for allowing them to get that bad.. when they are still doing their job,, leave them alone.
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You are the king of backtrackers my man. The king.
 
I don't think an engine mount can be the cause of vibrations. It can certainly make them a lot worse though. Eh?
 
I changed out all the mounts on both sides of my Aztec earlier this year. The Piper manual is a bit confusing (at least I found it so). So I ended up researching the part numbers in more detail.

The mounts on the plane were Lords, installed when Victor in Palo Alto overhauled the engines for a previous owner. The shops I called all now seem to use Barry mounts as they are a few bucks less expensive. The mechanics didn't seem to think there was any real difference; which left me with the impression the Barry mounts are a copy and not some superior new technology or design compared to the traditional Lord mounts.

During the "research" phase I ended up calling the company that makes Lord mounts and they really went out of their way to help me make sure I was getting the exactly correct part numbers for my make and model - emailed me pages from their tech documents and patiently walked me through those on the phone. I ended up buying Lord mounts as I figured the small difference in price amortized over 15 or 20 years of service life is peanuts. Nothing more sophisticated in my analysis and choice than that however.

With reference to some of the postings above, the thing that most made me change the mounts is that all were showing signs of hardening and cracks, with the ones just above the exhaust on each side by far the worst (they seem to take a lot of abuse despite the heat shields around them).

On the Husky, which is a 1996, all four of the original factory installed mounts are showing signs of age hardening and cracks, so they are being changed out too. Not sure which brand was used at the factory but I'll probably use Lord mounts again.
 
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Salty said:
I don't think an engine mount can be the cause of vibrations
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FYI: technically the engine mount is the steel tube assembly and the rubber inserts are technically vibration control/isolation parts and are called such by the manufacturer. The tube mount can be a vibration cause if cracked or loose. The separate rubber inserts would have to be pretty degraded/loose to be a cause.

Salty said:
It can certainly make them a lot worse though.
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Yes. The rubber inserts are designed to isolate certain levels of normal vibration from the airframe. If the vibration is outside the design level or the rubber is degraded then airframe vibration level is definitely worse.
 
Bell206 said:
FYI: technically the engine mount is the steel tube assembly and the rubber inserts are technically vibration control/isolation parts and are called such by the manufacturer. The tube mount can be a vibration cause if cracked or loose. The separate rubber inserts would have to be pretty degraded/loose to be a cause.


Yes. The rubber inserts are designed to isolate certain levels of normal vibration from the airframe. If the vibration is outside the design level or the rubber is degraded then airframe vibration level is definitely worse.
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I'm being pedantic, but a rubber insulator isn't moving on it's own, therefore it can't be the cause of a vibration. Unless your shock mounts are causing your plane to vibrate when the engine is off, then they aren't the cause. And again, yes, I'm being pedantic. Probably what we should be saying is that they can cause "excessive" vibrations to occur in the airframe.
 
Salty said:
You are the king of backtrackers my man. The king.
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So you go ahead and fix a lot of stuff that doesn't need it, we need your support.
 
OkieFlyer said:
I haven't noticed, and to tell you the truth, I haven't looked real hard at that.


Thank you. I'm not at all suggesting that we just change the mounts and quit. Quite the contrary actually. I'm almost 100% certain that I have an issue other than the mounts for other reasons outside of the scope of this thread. That being said, I still intend to change my shock mounts. Interestingly, after 21 posts nobody has yet made any attempt to address the question of Lord v. Barry mounts. You see, I never asked anybody if they think I should change my mounts and why, rather, I said I'm going to change my mounts and asked for guidance on which mounts to use.
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I thought I did in post 4 but all I said was that I went with Lord. Why? Because as I said, I needed two part numbers and the chart Barry provided didn't address that for a Piper Cherokee 140.
 
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