engine mount interference

[rjcthree]

9A with QB fuse. Mounting/drilling the engine mount. The lower rearward nose gear support on the RH side interferes with the QB installed forward facing nutplate for the fuel boost pump mounting, by no less than 3/32". Anybody else run into this? Right now, I'm not sure what the plan is, there will be no access once the mount is in place.

I'm likely to grind the nutplate and use a short bolt.

Thoughts?

Rick 90432

 

[ArVeeNiner]

Common problem

We all have that interference and we all do what you said, grind it and use a shorter bolt. Actually, I think I ground the existing bolt.

I don't know why they don't rev the drawing to fix this...oh well.

 

[rv9aviator]

When I ground mine down so it wouldn't touch there probably wasn't 3 threads holding the bolt. It does really need to be revised to miss the mount.

 

[panheadmark]

What I did.

My solution was to;

1- Remove the nut plate.
2- Drill and file a hex shaped hole in a piece of .040 aluminum that fit the
head of the bolt.
3- Insert the bolt (with the engine mount removed) through the firewall from
the engine side, back drill through the plate you made using the nutplate
mounting holes as a guide, then rivet it on the engine side of the firewall.

The end result is a bolt that doesn't contact the engine mount, can't turn due to the plate, and can't fall out due to the engine mount being in the way. A nut goes on the cabin side of the firewall to secure the pump.



Mark Erickson
RV9A 91317
O-360 Catto 3 Blade
Finish kit

 

[N526JS]

Yes, This nut plate interferes with the engine mount. It certainly did on mine. However, I believe that if you are using an fuel injected engine you do not use a fuel boost pump at this location. I drilled out both nut plates and riveted a SS patch over the remaining holes in the firewall.

 

[rjcthree]

Thanks

Thanks guys.

I actually started working on exactly what Mark described, a hex plate out of 1/8" stock. I'm going to wear out my little hand files.

I didn't feel comfortable with the 2.5 threads that would be left in the platenut.

Rick

 

[IowaRV9Dreamer]

stainless steel washers as engine mount spacers?

I've got the same interference issue - clearly a Vans design problem.

I notice that if I bolt up my engine mount on 3 corners, the fourth (on the lower right) is naturally a bit out from the fuselage (not much, maybe 1/32). The remaining two in the center bottom (nearest the nutplate) are out more, maybe 1/16.

It takes no torque to tighten them all up, but doing so makes the nutplate interference worse.

I'd like the groups opinion on the use of some stainless steel washers on the two center bottom engine mount bolts - to hold the mount out from the nutplate. This would simply keep the mount in it's natural (unbent) position. The washers are about 1" around.

I"m hoping that with the washers I can keep the nutplate from hitting the engine mount.

Otherwise, what is the deal with grinding the nutplate? Won't that defeat the locking function of the thing?

 

[Rupester]

A said by others ...

...this has been a problem on 7As and 9As for a long, long time. As much as I like and respect the Vans folks, it really angers me they don't make a simple design/drawing change and eliminate headaches like this. The lack of a "factory update" on simple items like this cost hundreds of manhours across hundreds of builders. Grrrr.
Someday, we should make a list of all these "factory/design issues" for those that follow us.