SB-00023 published: RV-12/12iS Engine Mount Standoff Inspection/Replacement

[bobg56]

If the hole does not quite line up it doesn't hurt to continue to torque until it does....

[Mel]

Originally Posted by rcarsey

I second that! Mine uses cotter pins. The only issue I had was that after torqueing, I couldn't install the cotter pin for 2 reasons.. the castellation didn't line up with the drilled hole (when does it ever!?), and also there was interference between the standoff and the cotter pin during insertion.
I had to make sure the bolt's drilled hole was up/down and not left/right. So maybe with locknuts, there's a better probability that builders will get the torque closer to spec.. ?

Standard procedure for torquing castellated nuts is to first torque to minimum spec, then continue to tighten until the holes line up. This will keep you within the required torque range.

[rvbuilder2002]

Originally Posted by Bob Y

Received mine May of ‘19. Maybe Scott can share what prompted the change?

Ease of installation.

AN-310 and cotter pins has been the traditional method for these type of fasteners (large sized fasteners loaded in shear and tension), but there is now decades of service history of using just all steel self locking nuts. Many certificated aircraft are configured this way.
Many builders of other RV models have been flying for a long time with steel self locking nuts.

Other than ease of installation, I know of no other benefits one way or the other.

[glongpilot]

Got notice from Bruce at Vans that the first batch of new parts came in but there were not enough to satisfy my order due to orders ahead of me. I should get one from the next batch but do not know when that will happen.

[DaleB]

WOW.

We finally had temperatures and opportunity yesterday to pull the original WD-1221 out and put in the new one. I had seen one crack during the initial inspection per the SB, but when we got it out and had a closer look it was much worse than we imagined. The right side was cracked close to 3/4 around the tube, and there was also a crack on the left side that we had not seen. It probably would have been visible with a flashlight and inspection mirror, but after seeing the first crack I hadn't looked any further.

Both cracks were exactly where the diagram in the SB showed they would be. On careful consideration, we figured that even if the tube had broken completely the airplane would not have fallen from the sky... it looks like both sides would have stayed attached, but it's still a little unnerving to see cracks like that.

[RFSchaller]

Dale, what was the service life on the part. Hours? Type of flying?

[DaleB]

Originally Posted by RFSchaller

Dale, what was the service life on the part. Hours? Type of flying?

A little under 600 hours currently. Three of us fly the plane, all low time pilots but nobody is abusing it. It's flown 99% off paved runways. I will say, though, that I've never been happy with the vibration level. We shipped the prop blades off to Sensenich last year for refurb and balance, when we had to replace the front half of the hub. It's better since then, but still not as good as I'd like it.

Right now we're finishing up replacing that tube, plus the trim servo and we're installing a landing light and the new throttle spring plates. I plan to re-balance the carbs again, then we're going to find a place to get the prop dynamically balanced. I don't think there is anyone around here that can do it, I'm considering a trip down to 52F to get it balanced.