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ibjet

Discrepant Engine Mount

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The isolator came out surprising well.  Is it better to make a quick strike as you're doing with the hammer or to slowly press the punchies thru the rubber with a vise or arbor press?

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Update: 1). I'm sorry, I uploaded only the 2 page version of my MRA. So I have deleted that and uploaded the 8 page version. 2). And to Runtoeat - I did try blanking out the shock disc by slow clamping motion in my angle-lock vise (made for milling, the jaws stay very square to each other). It came out slightly larger and more cylindrical. But, I messed up my punch, grrrr. I ordered some 1.50 dia alum rod and I will make a guide so that I can use a hydraulic jack and do this. What a career, sheesh! I'll have to post another picture of my set up (wood framed arbor press)!

I used multiple strikes with a mini sledge hammer. Just made 2 holes so far, but they both came out very straight and clean (amazingly). I will try the same method with my home made punch. I've got a 6 foot roll of rubber, won't run out, ha ha. I can always machine the OD if I need to (but it's a mess and very slow. 

I realized I didn't share the finished MRA, so attaching. I have not redone it to show the number, but It's 20-021-USA. 

When I start machining the steel parts, I'm going to add a cutting oil flood system. I bought the flex outlet hose, but I'm making a gravity flow system with a supply jug and drain jug. Lots of little steps to this project! But, as I have said, really enjoying the challenge. 

3-29-2020 update: Finished making my punch to blank out the rubber shock discs. Thought I'd share a couple pics. It is quite sharp: I nicked myself when taking it out of the fixture and it cut me! I'll have to find a container for it so the knife edge won't get bent up. I didn't make a handle, just put the rubber strip down on a 2 x 4 (I use the end of the 2 x 4, the punch cuts into the end grain easier), put the punch on top, put a piece of birch 1 x 2 on top and struck right over the punch with my mini sledge.

BTW: That's a 1/8 dia. carbide end mill. The supplier said I shouldn't need cutting oil (and I didn't have it set up) so I did this dry. When I saw these online I realized it would exert far less cutting force (when I cut out the periphery of my chrome moly sheet parts). It did just fine, the part and the cutter stayed fairly cool. 

 

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MRA - Engine Mount all pages rev 3-15-2020.pdf

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Yay, (6) shock mount discs done! They meet my drawing tolerances. And I have tooling to make more discs which I will pass on to the new owner, if and when I sell my CT. So, sharing some pictures related to the shock discs fabrication. The white object on top of the hydraulic jack is a PVC fitting I found at Home Depot, that would work for the adapter I needed - I machined it to slip fit in the bottom of my punch and over the hydraulic jack ram. I made the (5) additional discs I needed in about half an hour, way cool, ha ha. They did come out slightly larger OD (.010") by the slower shearing action of the hydraulic jack and truer because of the better alignment while shearing. I should be able to knock the (3) metal parts out in a couple of days, have it all planned in the point of my head, ha ha. 

ET

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I'll say this... you never... ever... give  up !  

We need more of engineer types like you in American Industry... let's hope it all works out for you...

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Made the spacer last night and installed it tonight. I had to make up a spacer as a tool to push it into place because the engine mount tube is so out of round (from the welding I'm sure). I already have a little fixture I'll need to machine the 2 offset washers in. Nothing left to do that will be that challenging.  

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 I have seen a couple out of round mount tubes like that, and that is not from welding. I think you may have placed fault for this problem where it did not belong.

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Tom: I machined the spacer to 1.480 dia and it went almost into place. I wanted it to be a close fit so the Loctite would cure. It was not a problem, I pushed it into place with Loctite all over it and in the space that I pressed it into. When I finished and cleaned it up, there was a nice ring of Loctite visible all around on both ends. It came out perfectly. When I finished installing it, I measured the step on both sides. It was calculated to be .973 and measured .9720 on one end and .9745 on the other.

I had honed out the inside of the tube and there were definite visible irregularities in the tube adjacent to the welds. I thought about this a lot, and decided I would make the sleeve dia. as large as possible and press it into place instead of boring out the tube (didn't want to weaken it). There is a very small gap between the spacer and the tube for most of the diameter (essentially a slip fit which is needed for the Loctite 620). 

You mentioned before that these tubes can be bent out of round by a bad landing. I don't see any way that would be possible, they are very rigid due to the 2 flanges inside (I thought they were brazed in, but they are welded. My engine mount did have a minor bend next to this tube from a bad landing apparently. I already straightened that in a fixture and posted a picture in my Engine Removal post. 

But, back to your comment ( . . . that "you may have placed fault for this problem where it did not belong"): The error that I am fixing is a fabrication error. The lower left tube is shifted up .180". I verified that with a very elaborate precision inspection on a granite table with 2 different digital height gauges. Actually, the more precise height gauge gave me .183" tube location error. 

ET

 

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13 minutes ago, ibjet said:

You mentioned before that these tubes can be bent out of round by a bad landing. I don't see any way that would be possible, they are very rigid due to the 2 flanges inside (I thought they were brazed in, but they are welded. My engine mount did have a minor bend next to this tube from a bad landing apparently. I already straightened that in a fixture and posted a picture in my Engine Removal post. 

That last picture you posted clearly shows that the tube is out of round. This is also the first time you have posted a picture that shows that that I have seen. 

I performed one of the first hose changes in the US in late 2010 on a CTSW, while doing the firewall blanket installation. I have since performed around 20. That first airplane had a slightly bent mount. The tube was out of round just like yours. It also had some alignment issues at the same location that looked just like your pictures. Fortunately the firewall was not damaged. The owner flew out of a very rough grass strip on the bank of a river. I flew with him, and I can understand how it got bent. he later further damaged the airplane.

I also had a local customer who landed short of the end of his runway and went through a small ditch. He bent the mount, again in the same location. He was not as lucky, as it had composite damage to the firewall. I have that mount in my junk box.

While you may not think it is possible, I have personally seen 2 that were bent. I can provide a picture if needed. If you talk to anyone who has been doing repair work on CT's for a while they will have seen it as well. It is a fairly common thing to happen, and many motor mounts have been replaced because of it. 

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Wow, great info Tom, thanks! I have thought a lot about the mis-alignment in my engine mount. I'm thinking that there must have been several engine mounts that were fabricated with the same error (because weldments like that are made in batches). There likely was an order of say 20 to 40 weldments that were done in the same lot as mine. It's very disconcerting that Flight Design would have accepted them that way. Those mounts are pretty amazing in most respects. Anyway, I'll show you where my engine mount was bent (I straightened it, but you can see the chipped paint. You can see that this is a weak point of the weldment. Thanks, really appreciate the detail info. 

engine mount former bent area.jpg

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Adding a few more shots of my progress. I milled the first of the 2 Flanges tonight. It didn't quite fit in the engine mount tube, so I mounted it on a little arbor and in a drill motor which I placed in a vise. Then I filed the OD until it just would slip into the tube. I wanted a tight fit so the Loctite 620 would cure properly.  

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Last big hurdle was to machine the offset hole in the flanges that go in the engine mount tube. Still have to machine the hole in the second one, but I saved my set up by placing two clamps against the first part to serve as stops. Along the way I decided I had to install my digital read out to keep track of where the centerline of the rotary table was in relation to the spindle. Tomorrow I'll finish the second flange and Loctite them into the engine mount, yay!

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Just noticed I have the same mini mill in my garage.  I can't see a day when I don't have a mill and lathe.  It's just so handy.

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One more picture for now - I finished the offset hole in the second flange and installed them both yesterday. I added Loctite 620 before and after installing each one against the spacer (in between them). Measured the .91/.92 dimension (it was .9125) and clamped them in place while the Loctite cured. This picture is after I removed the clamp and cleaned off the excess Loctite. I was very pleased, once I slipped the flanges into place they would not move side to side at all, each one was custom slip fit.

I have a broken tab on the lower most portion of the mount which I will remake and pop rivet on next. I was amazed that the part I need exists because it was done that way originally! I guess that one bolted on, I have to make mine a little longer and I'll attach it with blind rivets. I need to correct one dimension in my MRA, so I'll see if I can get by with adding this tab to my existing MRA. Mean while I'll draw it up and make it and order the rivets. And on and on it goes! 

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Sharing a few more pictures of my progress. First several show the cracked Camloc receptacle bracket. I will cut it off flush with the rectangular tube and rivet on a replacement which I'm working on today. I will leave it blank, clamp it in place, and test fit the engine mount and cowlings to finalize position and hole location (for the Camloc receptacle, which is cracked on one end). The last picture shows the crane scale that I just purchased to proof load the flanges/spacer inside the engine mount tube. This one is 600lb capacity, I wanted to get a higher capacity, but they were much more expensive and all had long delivery times.

I'll have fun making the bracket, I'll clamp the strip of sheet steel on my rotary table so I can rotate to all the different angles that I will need to cut. The rotary table and the chop saw have been golden to me on this project!   

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A little progress (see pics) . . .

Next I get to test fit up my engine mount and upper/lower engine cowling so I can finish position the bracket and match drill it to the engine mount frame and mark the center hole where the Camloc receptacle will go. Then I'll bring it home, and make the 3 holes needed for the receptacle. Then I will do that 600lb pull test of the new details inside the one engine mount tube. I already have a "fixture" for that (that I made to check and straighten the engine mount - I did straighten a little bend I had in the upper/left part of the engine mount). 

Then it will officially be time to clean up the engine mount and paint all the new steel parts and touch up paint the engine mount. I have not even opened my mini steam cleaner. I plan to use that on the whole engine. The video that came with it looks amazing. It's a very small "stream of steam" ha ha, but looks very strong too. It should be very helpful in cleaning the cooling fins of the radiator.

Hmmm, I'll post a link to the Amazon page on that mini steam cleaner, if that sounds interesting view the video:  https://www.amazon.com/gp/product/B07H8ZV4Y3/ref=ppx_yo_dt_b_asin_title_o09_s00?ie=UTF8&psc=1

I will use it mainly with the little spray wand, it's toward the end of the video. 

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I hit a little snag - I need to remove the Camloc stud where my new bracket will mate to the lower cowling. I have new studs but my old ones are held on by a specialty star washer (it's called a retaining ring) that gets forced over the barrel shaped carrier for the stud. The Camloc pliers that I bought are for some other kind of Camloc.

QUESTION - Has anybody removed one of these? I will try to pry up the star washer on one side with a steak knife and then cut the star washer with a Dremel cut off wheel. I will put some grind marks on the steak knife, but that would be sacrificial, ha ha.

I should have taken a picture of one of the camloc installations, forgot to. But I'll show the camloc studs and the star washer here so you can picture what I'm asking about . . . 

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Never tried to remove one, because when I was replacing them the retainer had already fallen off. You can use a couple sockets and a pair of slip grove pliers or small "C" clamp in a pinch.

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Thanks CT9000 and Tom. I have a dozen of those star washer/retainers on order. I removed it today by prying a skinny knife blade under the washer one place, then I slit it with my Dremel motor cut off wheel. Once I got that off, I realized the stud was still held on by the little cross bar. So, pleased to realize I did need to use the Camloc pliers after all! Tomorrow I'll put the 5 holes I need in that bracket and then the cleaning and painting phase is next. The engine mount has lots of chipped paint and even a little rust showing thru. I hope to make it look like new. I guess I'll buy a small can of white enamel primer and a spray can of Gloss white Rustoleum. Unfortunately, I realized that the Camloc studs I bought are one grip length too long! I got them quite reasonably, hope the same source will have the shorter ones. 

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A few more pics of my progress (this is a story of the tortoise and the hare,  ha ha)! My new Camloc receptacle bracket is finished (located in the airplane and marked, then put in all the holes), the new flanges/spacer inside my lower/left engine mount tube have been load tested to 600 lbs., and the flanges/spacer did not move. Now I need to put this project on the back burner, have a new mini split A/C to install. Excited about that too! 

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