I am flying tomorrow to PPonk and will ask Steve about this.
He is doing my engine in a couple of weeks, if he does not recommend new mounts then, I wont get them.

bat443 wrote:...please site... Otherwise it is just your opinion or that of someone who told you.
Tim

SUPPLEMENTAL INSPECTION NUMBER: 71-20-01, 2A-14-31. Required at 10,000hrs 20 years, or engine overhaul. Paragraph D says: If rust is found, cracks are suspected or if airplane has exceeded the compliance flight hour time listed above, remove the tubular engine mount. Conduct a magnetic particle inspection of these areas.

https://support.cessna.com/custsupt/contacts/pubs/ourpdf.pdf?as_id=37388

Technically, it is not "required" to remove the mount if you don't "see" or "suspect" anything. Guys that don't care, don't want to know, or want to save the cash are safe. Its not even an AD, so I should have been much more careful with my language.

Personally, on an airplane that may or may not have been operated for 70 years on uneven surfaces, it sure does seem prudent to go ahead and do some definitive testing beyond what an eyeball, a bright light, and a 7x magnifier can see. But that's just me...


CESSNA AIRCRAFT COMPANY
MODEL 100 SERIES (1953 - 1962)
SERVICE MANUAL
SUPPLEMENTAL INSPECTION NUMBER: 71-20-01
1. TITLE:
Engine Mount Inspection - All Models
2. EFFECTIVITY
Model 150 Serial Numbers 617, 628, 17001 thru 17999, 59001 thru 59018, 15059019 thru 15059700,
Model 172 Serial Numbers 610, 612, 615, 622, 625, 630, 28000 thru 29999, 36000 thru 36999, 46001
thru 47746, 17247747 thru 17249544,
Model 175 Serial Numbers 619, 626, 55001 thru 56777, 17556778 thru 17257119,
Model 180 Serial Numbers 604, 614, 624, 30000 thru 32999, 50001 thru 50911, 18050912 thru
18051183,
Model 182 Serial Numbers 613, 631, 33000 thru 34999, 51001 thru 53007, 18253008 thru 18254423,
Model 185 Serial Numbers 632, 185-0001 thru 185-0512
INSPECTION COMPLIANCE
ALL USAGE:
INITIAL
10,000 Hours
or
20 Years
(NOTE)
REPEAT
At Engine
Overhaul
(NOTE)
NOTE:
Refer to Note 1, Section 2A-14-00.
3. PURPOSE
To ensure structural integrity of the engine mount.
4. INSPECTION INSTRUCTIONS
A. Remove engine cowling, engine and sufficient accessories to allow removal of the tubular engine
mount. Refer to the Model 100 Series Service Manual.
B. Clean area before inspecting if grime or debris is present.
C. Conduct a visual inspection for cracks in the welds of the tubular engine mount and within three inches
on either side of the welds. Refer to Figure 1. Use a bright light and magnification lens of 7X or greater
power to aid in inspection.
D. If rust is found, cracks are suspected or if airplane has exceeded the compliance flight hour time listed
above, remove the tubular engine mount. Conduct a magnetic particle inspection of these areas.
Refer to Section 2A-13-01, Nondestructive Inspection Methods and Requirements, Magnetic Particle
Inspection, for additional instructions.
E. Replace the tubular engine mount, engine, previously removed accessories and the engine cowling.
Refer to the Model 100 Series Service Manual.
5. ACCESS AND DETECTABLE CRACK SIZE
ACCESS/LOCATION
DETECTABLE CRACK SIZE
Under Cowl
Not Allowed
6. INSPECTION METHOD
Visual and Magnetic Particle
7. REPAIR/MODIFICATION
Repair any cracks by rewelding. Prior to welding, locate either a drive pin or a hole welded shut in
the tube to be welded. Open the hole prior to welding. After welding, while the welded area is still
hot, introduce 3cc of unboiled Linseed oil or 6cc of corrosion preventative compound conforming to
D138-1-13 Temporary Revision Number 7 - Dec 1/2011
2A-14-31
Page 1
© Cessna Aircraft Company
Feb 3/2003
CESSNA AIRCRAFT COMPANY
MODEL 100 SERIES (1953 - 1962)
SERVICE MANUAL
MIL-PRF-81309, through the hole and reseal it using the same method as was used in the original
fabrication. The engine mount is not heat treated after fabrication, so no processing after welding is
required. Repairs may be made in accordance with Section 19 (Structural Repair) of the Model 100
Series Service Manual. Section 19 also describes tubes which MUST be replaced in their entirety
rather than being repaired. Any repair not available in Section 19 listed above should be coordinated
with Cessna Customer Service prior to beginning the repair.
8. COMMENTS
This is a complex and involved inspection. It is recommended that the inspection be coordinated
with an engine overhaul, even if the time does not exactly agree with inspection hours. Recurring
inspections will be satisfied by inspections at engine overhaul. The initial inspection must be
completed by June 30, 2015.

Thank's Greg, just wanting to keep the internet honest. I too send mounts out to be overhauled, but only at engine overhaul or if a problem is suspected, not each time the engine is removed. Usually require a couple of tubes to be replaced due to pitting exceeding 10 percent of wall thickness. I have witnessed other mechanics stripping, sanding, painting, and reinstalling mounts with pitting exceeding the limits (I'm old, just can't remember who the individuals involved were, and I am not the engine mount police in any case). Oh,and just so everyone understands the supplemental inspections you referenced are not required for "N" registered aircraft operated under FAR part 91 and may not be required for those operated under FAR part 135 depending on what is required by your Operating Certificate. (I am sure you are aware of this) though for aircraft receiving less than the highest quality care in my opinion are a good idea.

Tim

bat443 wrote:Thank's Greg, just wanting to keep the internet honest...

Tim

Silly me for thinking otherwise.

Rob wrote: I would send my mount to AWI for IRAN, and never look back. I don't think they'll leave one original tube in it. It WILL be new for all intents and purposes. I'd have them build it up as a K or L mount. And find the right legs for your motor....

AWI can overhaul my old A/J mount into a K style? Never thought about that.
That idea will go into the hopper for my (eventual) engine overhaul--
buy later engine legs & rubbers and rebuild mount accordingly.
Dunno what a set of newer style legs will cost me,
but the old style rubbers are about $840 for the set vs about $500 for the new style.
And they should last longer and probably be more effective.

I got most of the bits disconnected from my engine today in prep for removal, and finally got a clear look at the mount. I can see a good bit of corrosion, and it looks like someone just painted over it before - not good! I will yank the mount and blast it, and we'll see how bad it really is, but I will likely replace it regardless. It's going to need serious overhaul to be a contender, more work than I want to put into a 60 year old mount.

Jacking my own thread a bit here, but I was also pondering the Cessna exhaust design. The header pipes bolt up straight to the cylinders from underneath, no weird angles. They connect to the 3-1 collector, which just does an 'L' down to the muffler. Is there any legitimate reason why the headers and collector aren't or couldn't just be TIG welded to each other, and skip the mid clamps entirely? I would still use the muffler end clamps, but in my mind you'd basically just assemble the entire exhaust system and lift it into place as one unit.

The entire exhaust system just hangs down from the engine and moves with it anyway, and those crappy clamped joints aren't flexible enough to be useful in that regard. This just seems like a logical way to eliminate 6 guaranteed exhaust leakage points, lessen parts complexity, and remove the single worst thing to ever happen to engine mounts.

I have no doubt this requires some sort of field approval, but just from a purely mechanical standpoint, why not?

Knisley does pretty much what you want to get rid of the clamps but there is still a slip joint for the middle cylinder. Probably to much stress to be 100% solid.

180Marty wrote:Knisley does pretty much what you want to get rid of the clamps but there is still a slip joint for the middle cylinder. Probably to much stress to be 100% solid.

Yup, same with the Acorn exhaust. Also larger diameter tubing more appropriate for a larger displacement engine.


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Another thought: knisley and Acorn have done a good job of getting rid of the bead clamps on the risers but why not the header to “muffler” connection? I seriously hate bead clamps.

I was very close to hiring a DER to give me permission to install a V-band clamp on that joint when installing my new exhaust. Next time I have exhaust problems that’s what I’m doing dang it!


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Well OK then. I am probably headed towards the SPW (Acorn) mount + exhaust at this point anyway, glad to hear they have more or less gone down this path. I agree that better clamps would be ideal, maybe they'll get that approved at some point. At least with the muffler clamps you aren't torching the mount.

That looks like a great idea Halestorm. Big truck diesel engines use a clamp like that coming off the turbocharger.

Rajay STC used those V clamps, I have a fiend that is lucky to own a 182P with a Texas Skyways engine and Twin turbo Rajay STC.

I used those v bands on my Bearhawk exhaust. They are awesome, heavy but worth the weight I think.

thoughts on Isolators and stock engine mount?

Lord
VIP
Barry

I have no personal opinion on VIP. What I can glean on LORD vs Barry from the Internet is the Barry mounts cost half as much but appear to last half as long. IMO I'd go with the one that will last the longest, the couple hundred bucks saved pales in comparison to A&P cost to replace them more than necessary. Now, someone may have empirical evidence that the Barry's last about as long as LORD's, in which case they'd be a good deal.

If you need isolators for a stock mount, I have an almost new set of LORD's I was going to post up. We had just put them on when the engine issues surfaced.