Zero Force Member in Engine Mount?

[Toobuilder]

Originally Posted by F1Boss

...basic assembly of the part. How else might you keep those points secure while building the mount...

That is one of my theories Mark. Its there for assembly.

Certainly a possibility.

[David Paule]

You've made a hypothesis as to why that tube is unnecessary. My professional experience leads me to think that the tube is, in fact, necessary and I've explained why I think so. It can be tested either by models or by FEA, and both are available for free or inexpensively, as noted.

As a point of reference, I'm building an RV-3B. I'm not doing anything to knowingly reduce the strength of any of it, and I check with the factory from time to time if I think there's something I might have done that's problematic.

Please, before whacking that tube, verify its purpose either by test or analysis, or at least by contacting Mr. Harmon.

Dave

[Captain Avgas]

Dear Toolbuilder, as I predicted in post #7 you are not going anywhere here.

For a number of reasons, the combined engine /landing gear mount is a complex structure and as others have suggested it really needs an FEA to accurately determine intrinsic load paths.

However, if the engine mount comes from Harmon Rocket I can't for the life of me understand why you don't go directly to them for an opinion. Is it possible that you already have their opinion but don't like what you're hearing.

[Toobuilder]

Yes Bob, this case is beyond the level of understanding by mere mortals. You have uncovered my attempt to subvert the VAF collective with a discussion which has an actual black or white answer. I will hereby withdraw back into the shadows.

And yes, next time I see John I will ask him about the tube.

[Captain Avgas]

Originally Posted by Toobuilder

Yes Bob, this case is beyond the level of understanding by mere mortals.
.

Michael, you started out by asking a very complex structural question about a Harmon Rocket engine mount without even an annotated photograph or a drawing of the relevant device. And then it wasn't until your post #18 that readers even became aware of the specific member you were considering removing from the mount. In IT terms I think they call it garbage in...garbage out.

At any rate I think that eventually the "mere mortals" have given you a number of good suggestions which include a) Leaving the member in place. b) Referring the matter to Harmon Rocket c) Paying a professional to perform a proper analysis.

[Toobuilder]

Picture and description in the first post...

...but yes, nobody on the forum has produced a loads survey so I will take it off the board since a grass roots discussion seems to be such a source of annoyance.

[hohocc]

Speaking purely for myself it was clear from the first sentence of the first post which tube was being referred to. It did not take until post 18 to work it out.
I haven't a clue as to the science involved, but there is nothing wrong with the English being used to describe it!

[skylor]

Originally Posted by Toobuilder

That is one of my theories Mark. Its there for assembly.

Certainly a possibility.

You may find that the cross-member in question is absorbing some residual weld stresses from fabrication, and removing it will cause the mount to distort at the engine interface points.

Skylor