Engine Mount

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6843
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Engine Mount

Post by 6843 »

Hi All,

The rubber engine mount bushings (Continental part # 2387) have deteriorated and I have new bushings on order from spruce. The C-90 mount has a sleeve in the bushing that stop the compression at a defined spot. The C-85 bushing does not and, I suspect, you could squeeze the poop out of them long before you'd reach a torque value. So... how tight do I tighten the mounting bolts on a C-85?

Thanks,
Dave
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Dave Sirota
'46 C-140 N89654
'96 Hatz N24B
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6643
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Re: Engine Mount

Post by 6643 »

Warning! Can of worms...

There are two styles of mount, often called "conical" an "Lord" mounts. The mounts shown above are Conical mounts and fit all C85 and C90 engines except the -14 (e.g. C90-14) variants. The Lord mounts fit the C85-14, C90-14 and all O200 engines. (The Continental overhaul manual says the -16 variants also use the Lord mounts, but I have found that to not (always) be true.) The lord mounts are made up of 8 pieces, including a steel tube that runs through the center. The steel spacer is inside a rubber bushing (another one of the 8 parts) in the photo.
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lords_on_the_left_208.jpg
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To add to the confusion, Cessna lists a steel spacer that runs through the center of the conical mounts. Continental does not, and more than one person has mentioned problems using them since thee is no provision in the conical cushion for a spacer between the cushion and the bolt.

Here's the Continental drawing, including the torque spec (60-80 in-lbs.):
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Conical mount.jpg
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The Cessna part number for the steel bushing is 0450195. This is not the same spacer as used in the Lord mount, which is 0450200-502.

I'm sorry, what was the question?
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Re: Engine Mount

Post by 6898 »

Yes can of worms, (like wheel extenders) So my findings some 10-15 yrs ago as follows ; Thinking the steel tube spacers were meant to keep the mounts from smashing and also how can you get a correct torque with just rubber and nothing to bottom out on? Then thinking I was told the new conical mounts were a smaller dia. inner hole which could make sense because i hunted all over, found 4 tubes and theirs no way to get them in the rubber and through the case mounts? The call out for washers also seams too thin of a washer , after time they will start to pull and cave so we used a thicker large washer.
Jeff T 1948 C-140 NC3600V
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Re: Engine Mount

Post by 6643 »

6898 wrote: Tue Nov 29, 2022 8:44 amfound 4 tubes and theirs no way to get them in the rubber and through the case mounts
It's possible, with a lot of dish soap and blue language. However, it compresses the material in the narrow part of the engine case so much that it wears through pretty quickly. I ended up putting the spacers in the spare parts bin and going with the Continental recommended configuration. [And I stopped torquing at 60 inch-pounds.)

Continental says to adjust the torque between 60 and 80 inch pounds to achieve minimum vibration. I'm not sure how that could work...
The call out for washers also seams too thin of a washer
Yeah, my interpretation of the parts catalog is that you use two AN970-6 washers in front of each mount (8 total). I think I've seen other manufacturers calling for the same thing. The AN970s are each 1/16" thick. Continental part 21530 is a washer intended for the same purpose and is about twice as thick (as one AN970).

[Edit]The drawing above may imply they are 3/32" thick.
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