You are correct, mine has the gussets welded on the inside. PP kit shipped early 2025.
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RV-12A Engine Mount Cracks
- Thread starter 7StarsAero
- Start date
You are correct, mine has the gussets welded on the inside. PP kit shipped early 2025.
That one gusset might help in that one joint, but probably won’t help out in the main tube frame where most of us had cracks? Why support told me they hadn’t changed anything, but had heard that they talked about it???
Ramblin' Wreck
I'm New Here
Thanks for the heads up! I followed up with the parts department after reading this, and they confirmed that their “new stock” arrived early. My new engine mount is allegedly going to ship today or tomorrow. Still awaiting shipping confirmation, but fingers crossed!
Can you post pictures when you get it. I am on the fence spending that much if they haven’t updated it in some way.
I just got my rebuilt one back on today, after doing the second coolant hose change . I’m with Seagull , would like to see if and what changes they have made.
DaleB
Well Known Member
Thought I had posted to this thread, but maybe not. Of the four RV-12s that I know of at my home airport, three of them had cracked engine mounts last summer. One RV-12iS and two ULS-equipped. All were over 1K hours. We all had the mounts repaired locally. At least one of us called Van's and was told they were unaware of any issues with RV-12 engine mounts cracking.
Ramblin' Wreck
I'm New Here
New mount arrived! Slight variation from the current one that cracked. Reinforcing gussets are on the inside like others mentioned, so there are at least 3 variations of this mount.
The thing holding me up on removing and replacing the old one is the perceived quality of some of the welds and one nick that looks like a crack waiting to happen right where my old one cracked. I’m not an aerospace welder, so I’m waiting on the support folks at the mothership to sanity check my concerns. It looks to me like they heated these joints up to the point of the weld burning through the tube, which seems bad to my admittedly untrained brain. All 4 mounting points have some evidence of burn through, but the one with the nick is the worst. Any welders on here, please feel free to tell me if I’m being excessively picky and concerned for no reason.
The thing holding me up on removing and replacing the old one is the perceived quality of some of the welds and one nick that looks like a crack waiting to happen right where my old one cracked. I’m not an aerospace welder, so I’m waiting on the support folks at the mothership to sanity check my concerns. It looks to me like they heated these joints up to the point of the weld burning through the tube, which seems bad to my admittedly untrained brain. All 4 mounting points have some evidence of burn through, but the one with the nick is the worst. Any welders on here, please feel free to tell me if I’m being excessively picky and concerned for no reason.
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Piper J3
Well Known Member
It would be nice to know if engine mount fabricator does a post stress relief... Probably not techniclly required with thinwall 4130 tubing, but with so many instances of cracking it might be a good idea for add’l step in the process. Perhaps fasten mount to a jig to hold alignment, place in cold oven and elevate temp to 1100F for several hours, and then let oven cool to room temp before removing part.
Ramblin' Wreck
I'm New Here
I pinged the mothership again today to try and get a response re: the impact of the bleed through on several of the welds on my new mount, and I asked that exact question. I’ll let you know what they say. If the fabricator does a post weld heat treatment for stress relief, I’d be far less worried about the bleed through and possible stress concentration in those areas. Again, I might just have excessively high expectations, but given the history of cracked mounts and the price of the new one, I don’t think I’m being unreasonable.
Post oven stress relief is not done on wall thickness under .120. In fact it can visibly distort the mount on thin wall tubing. It is not required by FAA AC 43.13. It is not universally practiced.
My experience is you can do all the engineering you want and if something still breaks, then use heavier wall tubing. This is what I was told what their fix was for the stand off mount. Can’t really change the shape because of where everything fits and you have to hold your mouth just “ right” to get it on the engine.
Piper J3
Well Known Member
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Correct, but if engine mount is bolted to a heavy precision jig at each fastener position and entire jig with engine mount is slowly heated and slowly cooled, I bet most of the stress would be relieved. A heavy jig would prevent distortion and could be used repeatedly.
I think the intricacy of the weldment with different size tubing would override standard practice especially with current track record of significant cracks in the field.
I had two Continental A65-8 crankshafts ground 0.020” undersize which required Nitride Hardening. The FAA Repair Station had ~ 50% reject rate when they first offered this service. Cranks were placed in oven loose and they warped. Procedure was changed to sandwich cranks between two heavy bolted plates. Batch of cranks are placed in cold oven and everything cycles up through nitride temp and returned to cold before removal from oven. Process is now near 100% yield.
Mine was a perfect fit. Hopefully I won’t have cracks if this is the root case of the issue.
Same for mine - no shims required. Fingers crossed.
Mine was a nice tight fit yet it cracked. After the repair I was worried that it would have problems fitting, but went on just like before.
Those look like bad cracks for only 127 hours.
His SN is 120896, so I’d guess it’s the original WD-01221, and not the revised stand-off. Looks like the SB came out in 2020.
That would make sense. The cracks are right where the Service Bulletin said to look.
I'm curious, did you notice anything that made you look for this? Or was it found during a regular inspection?
