I  recently borrowed a rotisserie fixture for painting from a MOPAR  fiend of mine.  I think I will build a plywood jig to attach the finished fuselage to the rotisserie.  My question is how to determine the center of gravity at the firewall.

If X is the longitudinal axis, Y is the vertical axis, and Z is the horizontal axis.  How can I determine the intersection of the three at the firewall and the tail.  Solving this question will allow the fuselage to rotate freely and allow it to remain in a position without additional movement.

Thanks for your thoughts, 

David

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Most rotisseries I've seen have a sliding fixture at each end so that when you place the auto body (or in this case fuselage!) in the fixture, you can hold the fuselage level in z/horizontal axis and then slide it up and down along the y/vertical axis 'til it balances. If this rotisserie doesn't have one, I'm sure you could make some sort of slide with 2x4 lumber, etc., and lock it with wood screws.

Even if you could calculate a balance point, it likely would vary from build-to-build and depend a great deal on what you had or had not yet installed into the fuselage, so an adjustable method would be the way to go.

I'm guessing you could get away with a fixed holding point in the tail and just build the adjustable fixture on the firewall end.

John

N750A

Thanks for your input.  The rotisserie I have is homemade and only has 3 set points on elevation.  I'll use your idea with the 2x4.

Thanks

Hey David,

Did you get your rotisserie project done? I was inspired by your post and started mine over the weekend. Have to move the fuselage to another hangar. Here is my idea:

I used the damaged firewall as my template. However there is a drawing (in my case 6-B-6) for that part if needed. The central block made of 5  identical plywood fixtures inserted and firmly tighten up to hold the entire fixture. Four 2x6 pieces of lumber are making the frame around that central block. The next layer is made of 1/2 " plywood in form similar to the firewall:

And the  most inexpensive Engine Stand is used to support the rotation. Here is a couple of assembly photos to share - the final test and the moving I am planning to conduct this week. Will keep you posted.

The platform is a frame made of two 2x4x10 +  six studs of 2x4x8 with six total 3" rubber casters. I am planning to document that carriage and share with everyone who might be interested in that project of mine.

Thanks for your post it truly inspirational  

By the way I did not calculate the center of gravity - it is balanceble - I am interested in the central ox for the rotation to keep it rotatable Simply crossed two the longest points of my firewall over the central line. The balance could be added to the handler with the rotator on the opposite side - like a traditional weights (moment over the distance) 

Thanks for your post. You've got great ideas. I appreciate your help. David

Here is some extra pictures from our final collection: Today we have the fuselage moved to our new Hangar 12 (temporary) location

The rotisserie and the platform in one bucket - fairly light to roll with hands but we decided to use the rob and tow it

Tow was not a problem since one of us managed the break system

The delivered construction. Here is the full picture of our rotisserie :

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