ok, so who does good work rebuilding engine mounts?

[Clark1961]

Found a crack or two, ok, the darn mount is broken where the front strut is attached. Where's a good shop to strip, inspect, and repair as necessary? The A&P said he'd talk to some shops but I figure that I may as well talk to folks also.

Is normalization and stress relief usually part of the process after repair of these things? Looks to me like it should be but I'm used to working with heavier materials.

 

[Dan Thomas]

Found a crack or two, ok, the darn mount is broken where the front strut is attached. Where's a good shop to strip, inspect, and repair as necessary? The A&P said he'd talk to some shops but I figure that I may as well talk to folks also.

Is normalization and stress relief usually part of the process after repair of these things? Looks to me like it should be but I'm used to working with heavier materials.

Acorn Welding, in Edmonton, AB, Canada. They're so good they ship to Europe and many other countries.http://www.acornwelding.com/

We buy mufflers, mounts and other stuff from them. They're certified to manufacture some stuff from brand new, like the 172/Lyc mufflers, and those cost about a quarter of what Cessna wants for a new one. We get them to rebuild our mounts, or sometime exchange if time is important.

Dan

 

[ScottM]

We use http://www.wagaero.com/about.html in Wisconsin, they also have an exchange program that will minimize your downtime.

 

[Steve]

The FBOs in my area use Acorn Welding, also.

I'm considering sending them one for my plane to have as a pattern for other IAR owners.

Acorn Welding, in Edmonton, AB, Canada. They're so good they ship to Europe and many other countries.http://www.acornwelding.com/

 

[kmead]

We go through a lot of mounts here. My preference on the PA46 will always be new, they aren't always available quickly. My preferred mount company is always Kosola in Georgia they might have an exchange available. Acorn does well but I can't get the mount shipped to Kansas quickly or cheaply.

Regards, Kevin

 

[Bob Noel]

I was happy with Kosola.

 

[Clark1961]

Called Kolsola, Acorn, and Wag...

Looks like Kolsola & Acorn are competitive while Wag doesn't have the fixture to do the work (but would be willing to fix it on a time & materials basis). Acorn fills the mount with corrosion inhibitor. Kolsola didn't mention that.

Looks like I'll be spending about $2,000 just for the mount repair. Ouch!

Ya know, looking at the fracture, it looks like a side load that broke it. There's no deformation in any of the vertical structure and the main rupture is in a horizontal tube. Most puzzling because I don't recall ever having a large side load on the aircraft. Maybe it's just fatigue and maybe a few bad side loads in the past?

 

[Dan Thomas]

Called Kolsola, Acorn, and Wag...

Looks like Kolsola & Acorn are competitive while Wag doesn't have the fixture to do the work (but would be willing to fix it on a time & materials basis). Acorn fills the mount with corrosion inhibitor. Kolsola didn't mention that.

Looks like I'll be spending about $2,000 just for the mount repair. Ouch!

Ya know, looking at the fracture, it looks like a side load that broke it. There's no deformation in any of the vertical structure and the main rupture is in a horizontal tube. Most puzzling because I don't recall ever having a large side load on the aircraft. Maybe it's just fatigue and maybe a few bad side loads in the past?

What engine is this mount for? If it's the Lyc with Dynafocal mounts, the horizontal tube that runs between the two lower/inboard triangulation tubes does crack, starting at the welds. That tube is supposed to stiffen the assembly, but it's not so much in tension or compression as it is in bending.

Dan

 

[Clark1961]

What engine is this mount for? If it's the Lyc with Dynafocal mounts, the horizontal tube that runs between the two lower/inboard triangulation tubes does crack, starting at the welds. That tube is supposed to stiffen the assembly, but it's not so much in tension or compression as it is in bending.

It's the engine mount on the turbo Dakota so it's for the TSIO-360.

I'll try to post some pictures but it'll be Friday or so before I get back out to the airport.

 

[N801BH]

Called Kolsola, Acorn, and Wag...

Looks like Kolsola & Acorn are competitive while Wag doesn't have the fixture to do the work (but would be willing to fix it on a time & materials basis). Acorn fills the mount with corrosion inhibitor. Kolsola didn't mention that.

Looks like I'll be spending about $2,000 just for the mount repair. Ouch!

Ya know, looking at the fracture, it looks like a side load that broke it. There's no deformation in any of the vertical structure and the main rupture is in a horizontal tube. Most puzzling because I don't recall ever having a large side load on the aircraft. Maybe it's just fatigue and maybe a few bad side loads in the past?

Boy... Do I love owning an experimental and holding a repairmans certificate.

 

[Clark1961]

Boy... Do I love owning an experimental and holding a repairmans certificate.

Yup, not only the cost but now the aircraft will be out of service for about three weeks. As a result I had to book a flight to Dallas rather than flying myself. It's a twofer in the bummer department.

 

[Clark1961]

Ok, here are a few pictures of the broken bit. The gap in the upper member is right at 1/8 inch wide.

 

[N801BH]

WOW. !!!!. That is pretty ugly for sure..

 

[Dan Thomas]

Ok, here are a few pictures of the broken bit. The gap in the upper member is right at 1/8 inch wide.

Looks like bad landing technique, alright.

Dan

 

[Clark1961]

Looks like bad landing technique, alright.

Why would you type that? I used a strait edge to check and there is no other deformation of any of the other tubes. In particular there is no vertical offset on the horizontal fracture, e.g. it is a strait horizontal displacement.

It looks to me like a large side load was applied and we're talking an impact, not just setting it down a little crooked.

 

[Trapper John]

Why would you type that? I used a strait edge to check and there is no other deformation of any of the other tubes. In particular there is no vertical offset on the horizontal fracture, e.g. it is a strait horizontal displacement.

It looks to me like a large side load was applied and we're talking an impact, not just setting it down a little crooked.

Interesting. If that member failed in tension I wouldn't expect to see that clean of a fracture. It looks like it failed just at the edge of the weld - could be a fatigue fracture caused by or contributed by hydrogen embrittlement from poor welding technique.

What kind of process does the repair facility use to check the integrity of the remaining welds?


Trapper John

 

[Clark1961]

Interesting. If that member failed in tension I wouldn't expect to see that clean of a fracture. It looks like it failed just at the edge of the weld - could be a fatigue fracture caused by or contributed by hydrogen embrittlement from poor welding technique.

What kind of process does the repair facility use to check the integrity of the remaining welds?

I'm also thinking fatigue is a contributor. One of the repair shops mentioned that Piper's QC was less than stellar for the actual fit-up of engine mounts. In other words, Piper would use any mount they could force into position which could leave a static load on the framework, of course.

The actual inspection process from both shops sounded a tad suspect. I didn't hear the magic words "dye penetrant" or "ultrasound". I heard words like "lightly sand" and "know where to look.' It sounded like they had suspect areas to look for problems based on their experience. Considering Piper didn't put corrosion inhibitor on the inside of the mounts, knowing where to look for internal corrosion sounds important.

I'm also tempted to ask them to document wall thickness in a few choice locations. Ultrasound isn't a big deal as long as the gear is handy and ya know what yer doin'. All I've ever done is look over the inspector's shoulder so I fail both categories...

Of course the bad thing here is that a fatigue-life-remaining meter is yet to be developed. The aircraft only has about 2,600 hours on it so there should be plenty of remaining life.

edit: speling dye corrected

 

[Clark1961]

WOW. !!!!. That is pretty ugly for sure..

Ahh now Ben, ugly would have been pictures of a bent prop and an engine teardown. I call them "lucky" pictures!

 

[N801BH]

Interesting. If that member failed in tension I wouldn't expect to see that clean of a fracture. It looks like it failed just at the edge of the weld - could be a fatigue fracture caused by or contributed by hydrogen embrittlement from poor welding technique.

What kind of process does the repair facility use to check the integrity of the remaining welds?


Trapper John

I agree 100% on this analysis..... Way too clean of a break to be anything else.

 

[N801BH]

Ahh now Ben, ugly would have been pictures of a bent prop and an engine teardown. I call them "lucky" pictures!

Roger over...

 

[Dan Thomas]

Why would you type that? I used a strait edge to check and there is no other deformation of any of the other tubes. In particular there is no vertical offset on the horizontal fracture, e.g. it is a strait horizontal displacement.

It looks to me like a large side load was applied and we're talking an impact, not just setting it down a little crooked.

An impact can result from a bad landing. Slamming the nosewheel onto the surface, or even flaring so late that it hits first, is not unusual, and if the airplane is crabbing at the time damage can result.

Does the nosewheel on this airplane shimmy? That could fatigue those tubes and welds, too. On a 172, shimmy loosens the whole nosegear attach structure, and on one of our Citabrias, tailwheel shimmy broke the steel-tube sternpost.

For nosewheel shimmy, Cessna says that the first order of correction is to dynamically balance the nosewheel. Static balance won't do it. And since I started dynamically balancing our nosewheels about five years ago, we've had no shimmy issues unless the occasional tire wears all goofy and the balance deteriorates. Light aircraft tires are notoriously out of round and poorly balanced, and nobody seems interested in fixing that.

Dan

 

[Clark1961]

An impact can result from a bad landing. Slamming the nosewheel onto the surface, or even flaring so late that it hits first, is not unusual, and if the airplane is crabbing at the time damage can result.

Does the nosewheel on this airplane shimmy? That could fatigue those tubes and welds, too. On a 172, shimmy loosens the whole nosegear attach structure, and on one of our Citabrias, tailwheel shimmy broke the steel-tube sternpost.

For nosewheel shimmy, Cessna says that the first order of correction is to dynamically balance the nosewheel. Static balance won't do it. And since I started dynamically balancing our nosewheels about five years ago, we've had no shimmy issues unless the occasional tire wears all goofy and the balance deteriorates. Light aircraft tires are notoriously out of round and poorly balanced, and nobody seems interested in fixing that.

No Dan, the nose wheel never shimmied. Not even under heavy braking. On top of that, I've never landed nose wheel first. Perhaps a previous owner or pilot did but I see no strong evidence of a landing mishap.

I've seen a fair number of over-stress failures and there is always a "tang" or last fiber that is pulled out. I will note one particular case where the weld failed and later examination showed the weld wasn't to spec. In that particular case there was no obvious last failure portion. None of the ruptures show that character. In fact, that lower member shows a failure that is almost perfectly perpendicular to the tube and it is very uniform. Right now I'm thinking side load applied by an aircraft tug was the final straw on a pre-stressed member and/or stress intensified member. Perhaps fatigue and/or corrosion was contributory. Since there is no obvious deformation other than the gap I have a difficult time believing this was a singular event.

 

[Trapper John]

I'm also thinking fatigue is a contributor. One of the repair shops mentioned that Piper's QC was less than stellar for the actual fit-up of engine mounts. In other words, Piper would use any mount they could force into position which could leave a static load on the framework, of course.

The actual inspection process from both shops sounded a tad suspect. I didn't hear the magic words "dye penetrant" or "ultrasound". I heard words like "lightly sand" and "know where to look.' It sounded like they had suspect areas to look for problems based on their experience. Considering Piper didn't put corrosion inhibitor on the inside of the mounts, knowing where to look for internal corrosion sounds important.

I'm also tempted to ask them to document wall thickness in a few choice locations. Ultrasound isn't a big deal as long as the gear is handy and ya know what yer doin'. All I've ever done is look over the inspector's shoulder so I fail both categories...

Of course the bad thing here is that a fatigue-life-remaining meter is yet to be developed. The aircraft only has about 2,600 hours on it so there should be plenty of remaining life.

edit: speling dye corrected

The common non-destructive testing methods, dye penetrant (Zyglow), eddy current (Magnaflux) and ultrasonic, can only detect extant cracks. Unfortunately, as you noted, there's no predictive method for determining fatigue cracking in these situations. Not to be an arm waver, but a structure such as your engine mount could pass with flying colors today and fail next week; such is the mode of fatigue failure.

I'm not really sure that knowing wall thickness would be all that useful. It's more likely that the tubing selection was made given commercially available sections, rather than what was dictated by the loads expected to be imposed. At best, it would tell you something about the controls the tubing manufacturer had, and not what you really need to know in this case.

Is it possible for one of these pedigreed shops to essentially make an entirely new mount as a repair, thereby insuring quality welds (assuming that they have the correct QA/QC procedures in place)?

As a worst case backup, do the PA-28s have a restraining cable for the engine should the mount fail catastrophically?

Some of the Beech faithful and may chime in about the wisdom of Walter and company using the keel style of mount in the Bonanzas, and it would be hard to disagree with that design choice given the things were talking about here...


Trapper John

 

[Capt. Geoffrey Thorpe]

Ok, here are a few pictures of the broken bit. The gap in the upper member is right at 1/8 inch wide.

Well, if it's been flying OK without it, you probably don't need it, right?

 

[TangoWhiskey]

You haven't mentioned how you "found" this--was during annual, or did you spot it during preflight? Obviously, it's a good thing you found it, however it was, for the reasons you mentioned above (bent prop, etc.)!!

 

[Clark1961]

You haven't mentioned how you "found" this--was during annual, or did you spot it during preflight? Obviously, it's a good thing you found it, however it was, for the reasons you mentioned above (bent prop, etc.)!!

I was prepping the aircraft for the annual when I found it. It was the first time I'd pulled the lower cowl off the aircraft.

I've wondered if I should have caught it during preflight and have come to the conclusion that I need to be a bit more careful to inspect the engine mounts any time the upper cowl is off. Sure it is tough to see but if I'd traced each tube individually then I should have picked up the fracture (gap). I doubt I'd have picked up the crack in the lower member since that was difficult to see when I was looking right at it. All part of the learning process I suspect.

All in all, quite a learning process for me. I'm much more familiar with heavy equipment and non-critical failures. Obviously on the Pipers the engine mount is a critical component and deserves some extra time.

 

[Clark1961]

Well, if it's been flying OK without it, you probably don't need it, right?

Oh hay-zoos, I was really lucky that I didn't plant the nose on some poor unsuspecting runway. I really have no idea how long I've been flying it with the fracture. The ends are grimy so it's been awhile at least. I'm thinkin' that I took it into 6y9 with the broken bits.

On the plus side, yup, I do land it really gently just about 90% of the time. On the last landing in particular I felt the initial resistance to the strut compression before it stroked in normally. Pipers sure are amazing aircraft even if there were a few problems in manufacturing. Ok, I've also "plopped" it down a few times. Darn glad the struts are so forgiving when that happens. Anybody got a trailing link mod for the PA28's?:smile:

 

[Clark1961]

Talked to the welding shop (Acorn) and the preliminary evaluation is that an old repair was not done properly. It's real interesting that the logs have no mention of a repair.

Anyway, right now the plan is to only replace the two broken tubes. They think they'll be done with the work by the end of next week. I'm thinkin' I won't be flying before December...

 

[Clark1961]

Well the engine mount is finally headed back to me.

I think Acorn has failed to pass the test as a shop for repeat business. They fail in two areas, credibility and customer service. On the customer service side, they did not call me when the repair was complete. When I called them Monday they said the mount was in shipping then. I was more than a bit flabbergasted that they were done with the work and hadn't let me know. Settling the billing details cost an additional two days in shipping time. I'm certainly not happy about that. If they were taking care of business they would have contacted me when the mount went to the paint shop and they knew the total cost.

The next part is worse. The repair cost was exactly the price I had been quoted as "average" for a mount repair. It was not one dollar more or less. Okay, it is possible that the mount repair would exactly match the average of many mount repairs but it is not likely. Quite frankly I just don't believe they charged me fair cost.

It's all water under the bridge now but I'm giving them the publicity they earned. There are many shops capable of repairing engine mounts. I suggest not shipping to Canada.

 

[N801BH]

Well the engine mount is finally headed back to me.

I think Acorn has failed to pass the test as a shop for repeat business. They fail in two areas, credibility and customer service. On the customer service side, they did not call me when the repair was complete. When I called them Monday they said the mount was in shipping then. I was more than a bit flabbergasted that they were done with the work and hadn't let me know. Settling the billing details cost an additional two days in shipping time. I'm certainly not happy about that. If they were taking care of business they would have contacted me when the mount went to the paint shop and they knew the total cost.

The next part is worse. The repair cost was exactly the price I had been quoted as "average" for a mount repair. It was not one dollar more or less. Okay, it is possible that the mount repair would exactly match the average of many mount repairs but it is not likely. Quite frankly I just don't believe they charged me fair cost.

It's all water under the bridge now but I'm giving them the publicity they earned. There are many shops capable of repairing engine mounts. I suggest not shipping to Canada.

The paint shop = Thats the coat hangar hanging out back with a Krylon can of paint sitting on the upside down 5 gallon bucket.

Do me a favor and when it gets back to ya please take a few pics of their repair and post them here

TIA.

Ben.

 

[Clark1961]

The paint shop = Thats the coat hangar hanging out back with a Krylon can of paint sitting on the upside down 5 gallon bucket.

Do me a favor and when it gets back to ya please take a few pics of their repair and post them here

Ya want the empty Krylon can in the picture or not?

 

[Dan Thomas]

The paint shop = Thats the coat hangar hanging out back with a Krylon can of paint sitting on the upside down 5 gallon bucket.

Do me a favor and when it gets back to ya please take a few pics of their repair and post them here

TIA.

Ben.

I've been in Acorn's shop, and it's not like that at all. And they do good work. They ship to a number of happy customers in Europe. They're really busy, so contact with customer's can be spotty.

When it comes to expensive Cessna parts, they're hard to beat. Mufflers, carb airboxes, mounts, lots of stuff. When they do a mount they treat the inside of the tubing with a corrosion inhibitor, something even Cessna doesn't do.

Since I'm in Canada I often have to deal with US suppliers, and it can be ugly, I'll tell you. I've been waiting for six weeks for a shipment of ordinary stuff from American Champion. I've been waiting for at least five weeks for some striping tape from Gofer Auto. I'm waiting for some Superflite urethane. 20 years ago I was in the heavy-duty brake industry, and getting stuff from the US was tougher and took longer than getting it from England.

Dan

 

[Clark1961]

A few picts. From the paperwork it looks like less than 3/4 of the structure was renewed. Their welds look ok for the most part. Maybe a few small regions of undercut but nothing like the mount originally had on the tube-to-gear-sleeve weld that cracked.

For the picky types out there, most of the tube replacements were for mechanical wear. For the most part it looks like the wear was caused by zip-ties since thats the only thing that could possibly be touching the tube. Many ways to think about that little problem. One is to say something along the lines of a little wear is expected over 30 years. Another would be to say that use of lacing rather than zip-ties would have eliminated many of the tube replacements.

At least the aircraft should be reassembled by the end of the week or so. Hope it warms up a little before I get to finish re-installing the cowl, gear fairings, and tailcone bits.

On a side note, how 'bout that aircraft belly - nice and clean, eh?

 

[N801BH]

It does look like nice repair.:smile:
Proof will be when you fit it to the firewall.

Ben.

 

[Clark1961]

The fit up to the firewall went real well according to the A&P. They had the nose gear on today and were rigging that. Looked like they should get the engine on sometime next week.

Sounded like problems with the flightschool's planes were keeping them distracted from mine. An ancient Seneca (much older than it's years) is giving them fits.

 

[Clark1961]

Well, the Dakota ran today. Both mechanics were careful to tell me that it started right up. My reply was that I had great faith in them and knew they wouldn't break anything and starting like that proved my faith. They were a little surprised to learn the engine has always been a great starter and smooooth runner.

I got the the shop about 3:30 and just had time to clean the sump and glue on the heater. We'll get the cowl on in the morning and promptly park it in my hangar. Snow here tomorrow so no test flight.

 

[N801BH]

Congrats...

Which heater pad are you using?

 

[Clark1961]

E-Z heat