Conical Lycoming Rubbers

[birdofprey]

Has anyone had experiance with sagging engine mount bushings on a conical O-320? I topped my engine in June and replaced the worn out hardened rubbers with fresh ones from Spruce. During the replacement I noted that the last person to see to this had placed large area washers between the inner rubbers and the engine mounts on the lower bolts. This prevented the spinner from rubbing on the nose bowl. When I replaced the rubbers I took these out as they were not shown in the parts catalog. It wasn't but 3 months and 50 hours flying later that I noticed my spinner rubbing on the bowl and my tail pipe chafing against the engine mount diagonal. Thinking that the rubbers I used must not be of the correct composition; I ordered genuine Lycoming rubbers. I have flown those less than 10 hours and I can already see the sag developing. Anyone have a solution? I was working on a Citabria with a conical mount O-320 and noticed they use a Lord mount . Looking at the application guide the Lord mount is compatable with the O-320-A2B I have installed.

[Steve Pierce]

I have always used the Lycoming rubbers and no problems. I installed them per the drawing and torqued them to 40 inch pounds and double checked the 1.840" dimension from the engine installation drawing.

[gooeyduk]

Wrong information removed by gooeyduk

[Gilbert Pierce]

The drawing depicts a conical mount which is what an O-320A2B uses. The rubber insulators as well as the engine mounting holes are Conical or cones.
What you described, where the extended center line of the bolts converge at the center of mass is a Dynafocal Mount. In the Type 1 Dynafocal mount design the larger rubber isolators are positioned at an angle of 30°. The intent was to “focus” the mounts just ahead of the center of gravity of the engine/propeller combination. This mount reduces the engine vibrations felt in the airframe providing a smoother ride compared to the Conical mount.

Univair STC's for an O-360 engine uses a Dynafocal mount I believe. The E series and later O320's are Dynafocal.

[gooeyduk]

You are right Gilbert, I am wrong. It's the first time in my life.

[Gilbert Pierce]

I started to reply something to the effect that our President never made any mistakes but thought better of it. CHeers

[birdofprey]

Well I installed another set of lycoming rubbers on a 150 horse Pacer, We'll see. I followed Steve's 1.840 dimension. It didn't seem altogether different from what I was using. If you use the correct bolt's specifed in the part's book you have a very limited range of where the nut can be to pin the nut/bolt in a reasonable fashion. The 1.840 dimension seems to be at the maximum grip length allowable where you can still get a pin in.

[Eagleavn]

I have always used the Lycoming rubbers and no problems. I installed them per the drawing and torqued them to 40 inch pounds and double checked the 1.840" dimension from the engine installation drawing.

Wait what is the 1.840 dimension mean????? What are you measuring? I am in the process of installing new ones and I am not aware of that requirement.....Please school me!!!


Lloyd

[MN_flyer1]

1.840" is the compressed length of the rubber (inside washers) on the conical mount when properly torqued. You may have to make a little 1.840" notch in a sheet of aluminum to measure across the engine mount.

[Eagleavn]

1.840" is the compressed length of the rubber (inside washers) on the conical mount when properly torqued. You may have to make a little 1.840" notch in a sheet of aluminum to measure across the engine mount.

OK Thanks....

LP