How Do You Properly Register a Brushless Motor On A Firewall

[AKfreak]

Hey there guys, I am at the final stages on my build, and I have saved one of the most difficult things for last (mounting the motor).
I know my plane is designed to fly with a Gas motor or Electric, but the instructions just leave me scratching my head with respect to mounting the motor.

I am aware of the thrust angle built in the firewall (right & down), but the markings on the firewall leave me a bit confused. The hole is not dead center, and the vertical line placement is offset. I get the horizontal line,it seems to be in that position to insure the motor shard exits the cowl opening.

I guess my question is what are the lines for, and how do you precisely mount the motor in the correct position based on the lines marked on the firewall.

I was going to pull a sting line through the tail of the plane to ensure I am centered left to right. Then put the motors standoffs on the motor with the spinner and prop installed. Tape the cowl in place and try to hold the motor so the spinner is centered on the string line then mark the standoffs. Then Drill and Mount the motor.

I am Extremely interested on how to determine the exact final location of the standoff holes based on the firewall markings. If you know of a video or a post that explains this process in a simple manor, I would be extremely grateful. You know Extreme Flight makes this process so easy, I wish my plane was the same.

I am just four little holes away from finishing up, but I don't want to mess this up so I ask your your advice.

 

[3dNater]

The line is offset on purpose... dont fix it!

What they have done is show you where the center of the mount pattern should be in order to have the prop shaft in the middle of the cowl. Since there is right thrust built in they have taken the guesswork out of that part of the equation for you.

 

[3dNater]

Use those lines on the firewall to center your mounting pattern right where they would intersect. The horizontal line is showing you where the designer thought the thrust line should be. The fact that it is not centered on the firewall is irrelevant.

 

[AKfreak]

Thanks for the info. I totally get it. After mocking it up, that offset cross represents the dead center of the motor shaft. DOH..

What I said needs fixing is the gap at the corner of the motor box.

 

[3dNater]

Ok, when I looked at it the first time I was on my phone... if I had zoomed in on the pic I would have noticed the gap Ya, if you mount right there your shaft should be pretty well centered in the cowl.

Does that gap look like it poses a structural threat? If not I'd leave it... it is under the cowl

 

[3dNater]

You could fill that gap with thick CA and drop some baking soda in it. Makes an excellent filler.

 

[AKfreak]

You could fill that gap with thick CA and drop some baking soda in it. Makes an excellent filler.

I will use thick CA and one of my wood clamps to pull it into place.