Engine mount alignment off center

[GLPalinkas]

Hi gang,

I am about to install the engine mount (RV-6 O-360) and noticed that when placed in position with temporary 1/4" bolts thru the firewall that the center of the mount is approx. 1 1/2" off from the airframe center point.

Is this normal?

I would think the the center of the mount should align with the center of the airframe.

I purchased the entire QB package/engine/finish kit, etc. in 1998 from Van's so who knows what they were building back then. I thought that they would have drilled the firewall holes using the actual engine mount they sent me. Wrong again.

Thanks for any help.

Gary

 

[rv8ch]

engine offset

There should be a drawing of the engine mount in the plans, and IIRC, it has a pretty healthy offset. This is to help minimize the workout your right leg gets when flying.

 

[rodrv6]

Are the four corners where the mount bolts up to the firewall equal distance from the centerline of the firewall? The portion of the mount that the engine bolts to is offset to one side and the engine centerline is designed to be at an angle to the fuselage centerline to counter the P-factor during takeoff. If your firewall mounting points are equal distance from the firewall centerline, it should be located properly.

 

[Rick6a]

Offset

....noticed that when placed in position with temporary 1/4" bolts thru the firewall that the center of the mount is approx. 1 1/2" off from the airframe center point. Is this normal?....

Gary,

If you critically examine the engine mount closely from various perspectives and angles, it will become increasingly clear to you that it is not assembled with a perfect symmetry. The right side is shorter than the left side. In fact, the built-in offset is designed to help overcome the P factor (is it 3 degrees?) and will become very apparent when you attach the FAB later and have to custom fit it to mate with the airscoop on the lower cowl. This is quite normal. Anticipate that ultimately, the cowl halfs will be asymmetrically trimmed to evenly butt with the firewall and forward skins.

Rick Galati RV-6A "Darla"

 

[GLPalinkas]

Engine mount positioning

Mickey/Rod,

Thanks for the help. I measured per the plans and the firewall holes are where they are supposed to be, equidistant from the C/L. The engine side of the mount is also OK based on your input.

It never hurts to ask with the older kits.

Thanks and back to work (well, aircraft building work)

Gary
RV-6 QB
Firewall forward fun

 

[gvgoff99]

Off Center

The air scoop is shown on the plans as being "on center." You may want to move it about 1/4" to the left when doing the cowling. You will find that if you do this it is not noticeable and that you have done yourself a BIG favor for the clearance of the carb and all the stuff that hangs off of it. Go look at a few and you'll see what I mean. This is true for all Lycomings. The carb is not mounted dead center on the engine. It hangs a little to the left.

 

[szicree]

Go look at a few and you'll see what I mean. It hangs a little to the left.

I'm familiar with this.