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  #1  
Old 07-23-2022, 06:53 AM
andrewbutler andrewbutler is offline
 
Join Date: May 2006
Location: Meath, Ireland
Posts: 49
Default RV7 Engine Mount Crack

Hello,

I am looking for advice. I appear to have developed a small crack in a gusset on the port side of my engine mount. See three photos attached.

Aircraft total 500 hours, circa 500 flights mostly from grass. Currently operating off a hard runway.

I have some queries:

1. Is the aircraft airworthy?
2. If it is a crack, what are my options for repairing?
3. Assuming it needs to be welded, do I have to remove the mount, given the relatively small size of the crack?

Thank you for your help.

Best regards,

Andrew Butler.
RV7 EI-EEO located @ EIMH in Ireland.
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  #2  
Old 07-23-2022, 08:40 AM
lr172 lr172 is offline
 
Join Date: Oct 2013
Location: Schaumburg, IL
Posts: 7,753
Default

No guidance on airworthiness, but the issue is really ground worthiness, as the risk is the leg breaking off on a hard landing, though given the pics it doesn't look like that is going to happen any time soon. Please don't take that as a recommendation to keep flying, as I have no expertise in analyzing metal failure.

Very easy weld repair for a welder that uses gas or Tig. Can be welded in place, but will probably need to use some wet towels on the inside of the firewall to avoid burning things in that area. I would remove the bolt first to avoid loosing it's hardness. Also pull the leg and re grease, as it will likely liquefy during welding. If you take it off, you can bring it to most any shop, just be sure the welder knows that it is 4130 steel and not mild steel. I recommend a welder that has some experience with Chromoly steel. 4xxx steel is NOT unique to aviation and should have no problem finding a welder that has worked with it.

FYI, Tig machines need 220V and 50 amps, so that probably rules out that option at your airport, excluding welders that specialize in field repairs; They have gas powered machines on their truck. Gas welding, however, is fully portable.

Caveat: You need to inspect for cracks on the backside of that area. If you are unable to inspect that area, I recommend removal of the mount to inspect it. If there is a crack on the back side, the welder will not be able to get to it with the mount installed. It would seem that the gusset is taking the brunt of the loads, so other cracks are unlikely, but that is not a good reason to not be sure.

Larry
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Last edited by lr172 : 07-23-2022 at 08:59 AM.
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  #3  
Old 07-23-2022, 10:28 AM
Mile High Relic Mile High Relic is online now
 
Join Date: May 2010
Location: Arvada, Colorado
Posts: 365
Default

Quote:
Originally Posted by lr172 View Post
...Also pull the leg and re grease, as it will likely liquefy during welding....
I had similar cracks in my RV6 in 2015. It was an engine mount that did not already have the gussets.

I'm definitely not an expert, but when I called Vans to talk about the repair, they said I should NOT remove the gears legs from the from the mount, indicating that getting them back in would be very difficult. Maybe it is different for the newer kits.

The engine and mount were removed with the gear legs in place so the gussets could be welded on.

As another data point, a chapter member who also has an RV6 had similar cracks and when he called, Vans indicated he should get a new engine mount with the gussets already installed.
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  #4  
Old 07-23-2022, 12:01 PM
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Larco Larco is offline
 
Join Date: Mar 2005
Location: DVT Phoenix
Posts: 1,300
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Here locally we have a couple of welders with huge experience that will and have come to the hangers with their 110 Volt portable Tig welder and done some very nice work. Had some welding done on a couple of motor mounts in place and it worked out fine, however if they wanted it removed off it would come. :-) Check around and talk to an experienced welder as the Tig welder technology has changed immensely over the last few years.
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  #5  
Old 07-23-2022, 12:12 PM
lr172 lr172 is offline
 
Join Date: Oct 2013
Location: Schaumburg, IL
Posts: 7,753
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Quote:
Originally Posted by Mile High Relic View Post
I had similar cracks in my RV6 in 2015. It was an engine mount that did not already have the gussets.

I'm definitely not an expert, but when I called Vans to talk about the repair, they said I should NOT remove the gears legs from the from the mount, indicating that getting them back in would be very difficult. Maybe it is different for the newer kits.

The engine and mount were removed with the gear legs in place so the gussets could be welded on.

As another data point, a chapter member who also has an RV6 had similar cracks and when he called, Vans indicated he should get a new engine mount with the gussets already installed.
Agree completely! I meant to say remove and re grease after welding; I should have been more careful with my words. If it comes off without force, it is likely to go back in. If it doesn't come out, just drip oil into it each annual. The weld area for the OP is at the top of the gusset and pretty far from the sleeve, so distortion of the sleeve is not likely. Adding gussets is different, as you are welding the bottom of the gusset directly onto the sleeve and warpage of that sleeve is all but guaranteed in that case. From the OPs pics, there is no cracking at the lower gusset bead.
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Last edited by lr172 : 07-23-2022 at 12:33 PM.
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  #6  
Old 07-23-2022, 12:17 PM
lr172 lr172 is offline
 
Join Date: Oct 2013
Location: Schaumburg, IL
Posts: 7,753
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Quote:
Originally Posted by Larco View Post
Here locally we have a couple of welders with huge experience that will and have come to the hangers with their 110 Volt portable Tig welder and done some very nice work. Had some welding done on a couple of motor mounts in place and it worked out fine, however if they wanted it removed off it would come. :-) Check around and talk to an experienced welder as the Tig welder technology has changed immensely over the last few years.
Hopefully that works. My Tig wll run off 110, but I am not sure I could weld 1/8"+ steel (need to melt that current bead, as the crack is likely in the HAZ) without at least a 20 amp circuit. My machine recommends a 30A circuit for 110V. Possibly the pro's can get it done with a lower current. I am just an amateur.
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Last edited by lr172 : 07-23-2022 at 12:21 PM.
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  #7  
Old 07-23-2022, 12:34 PM
JDeanda JDeanda is offline
 
Join Date: Apr 2013
Location: Ventura, CA
Posts: 364
Default Randumb Thots

Just welding up a crack in a structural part is not a good repair. The fact that it cracked is an indication that it wasn't quite strong enough in the first place. Just welding the crack only returns the part to it's original strength AT BEST. If Vans has a mod to add a gusset or something, then of course that needs to be done at minimum. It might be a good idea to add a finger patch or something. Vans will help you if you email or call. Additionally, here's some info on the man who welds Vans' parts: https://www.finduslocal.com/local-bu...5-ne-209th-st/. He seems to be the guru and he will be able to help, too. Welding on the airplane seemed a bit dicey to me, but as noted above, there are welders about there who can do magic with a TIG torch (there's one at our aerodrome) and I think I'm fairly reconciled to that now. Be sure to isolate your avionics! As far as your airplane, I think I'd be willing to ferry it somewhere to get it fixed but of course that sure isn't anything I'd ignore.
At about 2000 hours, the engine mount on our RV-6 was just starting to corrode and the holes for the bolts that held the gear legs in place were getting pretty loose, so I finally pulled the mount, added Vans' gussets at the gear legs, welded on big bushings with extra thickness at the hole locations and then reamed and honed the holes for oversize bolts, bead blasted and repainted the thing. It was a big job, especially since I'd removed the gear legs. As noted, they came out relatively easy, but after all that welding they went back in very hard. And I feel good about the repair. It ain't a-gonna fail anytime soon.
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  #8  
Old 07-23-2022, 05:27 PM
kiwipete kiwipete is offline
 
Join Date: Oct 2007
Location: Birmingham United Kingdom
Posts: 485
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Andrew

Loads of information on the UK Rv squadron group regarding crack repairs and modifications.

https://groups.io/g/RVSqn

Most UK Rv-6 / 7’s have been repaired or modified as we fly off more grass strips and cracking as a result is more common.
The UK LAA also has a few repair modifications.

PM me if you want more info.

More info on this thread


https://vansairforce.net/community/s...d.php?t=147392

Regards

Peter
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Last edited by kiwipete : 07-23-2022 at 05:52 PM. Reason: More info
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