Engine mount 22387

[Will Weidner]

I have questions about the engine mounts.  I bought p/n 22387 from Aircraft Spruce.  I was hoping that some of the seasoned veterans can comment on the following:

     - These mounts don't meet Steve Kiblinger’s criteria of being able to close the hole with thumb pressure. They are closer to being hard as a rock. However, I’m guessing this is what people are using, because that’s all I could find.

     - The cone angle isn’t 90 degrees, in fact it’s slightly less than 80.  This being the case, if I use 45 degree angles on my mount tubes and spacers, I won’t get good contact with the angled face on the tube until the mount is significantly deformed.  I can’t imagine this is what’s intended.

     - The Joe Engleman engine mount stud must be for a mount other than the 22387.  Anyone know which one?

I know I tend to over-analyze, but any comments on the above would be appreciated.  Thanks.

[Steve]

I have questions about the engine mounts.I bought p/n 22387 from Aircraft Spruce.I was hoping that some of the seasoned veterans can comment on the following:

    - These mounts don't meet Steve Kiblinger’s criteria of being able to close the hole with thumb pressure.They are closer to being hard as a rock.However, I’m guessing this is what people are using, because that’s all I could find.

    - The cone angle isn’t 90 degrees, in fact it’s slightly less than 80.This being the case, if I use 45 degree angles on my mount tubes and spacers, I won’t get good contact with the angled face on the tube until the mount is significantly deformed.I can’t imagine this is what’s intended.

    - The Joe Engleman engine mount stud must be for a mount other than the 22387.Anyone know which one?

I know I tend to over-analyze, but any comments on the above would be appreciated.Thanks.

Here is a link to the mount bushing spec's currently being offered... If the 60-70 Durameter value doesn't pass the thumb press test look for  equivalent dimensions in the 40-50 Durameter range at McMaster-Carr : http://www.skygeek.com/continental-motors-22387-bushing.html

[Will Weidner]

Thanks for the information.  I got my mount bushings from Aircraft Spruce.  I just measured them, and they are 68 durometer, exactly to the spec's on the Sky Geek website.  I looked in Mcmaster, but they don't have anything that looks like that.  I looked in other places too.  The only thing remotely similar is shock absorber bushings, but there aren't any durometer values listed.  I'm going to have to go ahead with what I got since I've already fabricated station 1.

[Steve]

Thanks for the information.  I got my mount bushings from Aircraft Spruce.  I just measured them, and they are 68 durometer, exactly to the spec's on the Sky Geek website.  I looked in Mcmaster, but they don't have anything that looks like that.  I looked in other places too.  The only thing remotely similar is shock absorber bushings, but there aren't any durometer values listed.  I'm going to have to go ahead with what I got since I've already fabricated station 1.

Down the road, if you are interested in 40 Durometer mount bushings consider getting 40 Durometer rubber bottle stoppers from McMaster-Carr and machine them after looking over the shoulders of others at: http://www.practicalmachinist.com/vb/general/machining-rubber-202796/

BTW: Murray was bubbling over after his visit with you and your son today - a perfect Saturday...

[Will Weidner]

Steve,  thanks for those ideas.  I hadn't thought of bottle stoppers, although I have dabbled in machining 40 durometer urethane barstock from Mcmaster.  It's like trying to machine a rubber band, and I have been moving toward one of the solutions (cutter rake and relief) mentioned in the link you provided, although there are a lot of ideas in there yet to try.  Thanks for the link, it gives me a lot of things to try.  My plan is to go ahead with the 22387 mounts, but I like knowing I have one or two viable fall back plans if I'm not happy with the results.  I've been dragging my feet welding station 1 to the fuselage, thinking that it boxes me into 1 option.

We had a great time with Murray yesterday.  He's a really interesting and nice guy.  We have to think of an excuse to go visit him again soon.

[Steve]

Steve,  thanks for those ideas.  I hadn't thought of bottle stoppers, although I have dabbled in machining 40 durometer urethane barstock from Mcmaster.  It's like trying to machine a rubber band, and I have been moving toward one of the solutions (cutter rake and relief) mentioned in the link you provided, although there are a lot of ideas in there yet to try.

You are making machining sounds - don't overlook the Joe Engelman lower motor mounts studs - sketch attached:

The .pdf viewing quality is marginal but printed to good paper it's good to go...