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Engine Mount cracked

Pittsartist

Well Known Member
"Every picture tells a story" or so the saying goes.

........... So here's my little story.

Spotted at the 2nd annual from new, 116 hours total logged, Almost all flying off grass strips (in reasonable condition)

Cracks in gear leg sockets - both sides, same place, red Dye Pen shows it

33301191785_f1396b3b37_b.jpg
[/url]IMG_3387 by WIGY TV, on Flickr[/IMG]

Mount off

32458253104_6bd0cbd538_b.jpg
[/url]IMG_3372 by WIGY TV, on Flickr[/IMG]
http://flic.kr/p/Rse2Pw
S9Tza7


Engine Off

33260433166_dc67028732_b.jpg
[/url]IMG_3380 by WIGY TV, on Flickr[/IMG]

Strip Mount

33260429176_c6aac6285f_b.jpg
[/url]IMG_3391 by WIGY TV, on Flickr[/IMG]

Bare Metal ready for Welding

32918434430_f56bf07ff1_b.jpg
[/url]IMG_3393 by WIGY TV, on Flickr[/IMG]

3 Days work so far. I'm expecting the get the mount back later this week and start re assembly - Predicting about 6 days work in total to repair the problem.

What I have learned so far

- The standard "6" mount is in need of some strengthening if you regularly operate from Grass
- I plan to change my operational technique post repair to give the mount as easy a time as possible (No more "Wheeler" ladings, Tail up taxiing, choosing rough grass strips when a smoother alternative is available, 20 min Aeros flights that could be tagged onto the end of another mission)
- There seems to be 3 levels of repair available
1) Just weld the cracks
2) Weld and add reinforcement gussets from 4130 steel
3) The above plus replace the gear socket tubes with custom made replacements machined from steel billet with a thicker wall.
- Above all, I really wish I had done "2" in the above During the build

I don't suppose there are that many 6's at this stage of build these days - but I hope this post may be of use to any that are.

...... Still love the aeroplane though, No regrets :D
 
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Couldn't view the photos. Only saw a small green square logo in place of each photo. :confused:
 
Same thing to me

Good write up.
Link to pictures worked for me.
I had the same thing happen to my dynafocal mount on my -6 at about 900 hours of mixed use runways but mostly paved. My crack was on the topside of the bottom of the gear tube, very close to your location, so I waited until a fwf update and then removed/stripped/inspected/welded crack/added Vans supplied gussets and repainted with epoxy white paint. Also straightened gear legs while I was at it. I would urge you to check yours by sighting down the length while you have them off.
Vans is aware of this and supplies gussets for the fix. I was told by vans that this gusset was added to the -7 mount and after adding the gusset, you virtually now have a -7 mount.
I never thought of replacing the gear tube with a heavier one.....
Thanks for posting.
 
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Richard, You need the 'Netherthorpe' mod - involves adding some gussets to strengthen the lower tubes. As fitted to -7 mounts. Not sure who is best to get the details from - I will ask on the Yahoo group. Pete

Call Mark or Dave Bonsall a call at Dukeries aviation. They have done several and should be able to give you all the info. P
 
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RV6 Engine/Mount/Gear removal procedure.

I would be very interested in how you got the bird off the ground high enough to remove the engine & mount & gear as a complete unit?
And especially how you supported the aircraft once gear/engine & mount were removed?
Did you have to weight or tie the tail down?
Thank You
 
I would be very interested in how you got the bird off the ground high enough to remove the engine & mount & gear as a complete unit?
And especially how you supported the aircraft once gear/engine & mount were removed?
Did you have to weight or tie the tail down?
Thank You

I only have one (auto) engine hoist so
- Empty fuel and any other "easy" bits of weight
- Lift the whole aircraft using the engine lift ring so the main gear is just off the ground
- fit the lashing eyes to the wings oriented so the hole is aligned with the spar
- Make up some 4 x 4 " x 18" wooden blocks with a 1 1/2" deep 3/8" wide slot cut across them half way along
- Lower the lashing rings into the slot with a steel bar through the ring (I used a 1/2" socket set 12" extension drive). The bar takes the load, the ring cannot bend as it sits in the slot in the wood.
- With the hoist still taking most of the load I managed to slide the engine & mount forward off the firewall bolts (yes - the tail would have tipped up had I not kept the load partly on the hoist)
- Remove the mount from the engine once separated from the air frame

I have been told that the lashing points will support the entire aircraft if needed. There certainly did not seem to be any problems during the above - but I never had the full weight on the lashing points. My A/C weighs 1066lb empty, I guess about 350 for the engine & prop so maybe 700lb ish to support. There must be 100lb of this on the tail wheel so 300lb per lash point ?.

Regards, Richard
 
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Richard, You need the 'Netherthorpe' mod - involves adding some gussets to strengthen the lower tubes. As fitted to -7 mounts. Not sure who is best to get the details from - I will ask on the Yahoo group. Pete

Call Mark or Dave Bonsall a call at Dukeries aviation. They have done several and should be able to give you all the info. P

Hi Pete. That's Prophetic ....... the mount arrived with Mark yesterday :D

All the best, Richard
 
- Lift the whole aircraft using the engine lift ring so the main gear is just off the ground

The engine lift ring is designed to support only the weight of the engine! A much safer way to lift the aircraft is by tying the straps to the engine mount.
 
The cracking is very common for high time RV-6s and RV-6s that operate off of grass. The fix is to install the WD-762A-L and WD-762A-R Gear Socket Gusset to engine mount that is used on the RV-7.

At 2,724 hobbs hours, I added the gussets to my mount.
 
The engine lift ring is designed to support only the weight of the engine! A much safer way to lift the aircraft is by tying the straps to the engine mount.

Ah !. I did not know that ..... just having vivid thoughts of pieces of missing crankcase.

"Every days a school day", or so the saying goes ......
 
Exact same spot

I started my annual condition inspection just after I read this article and I went straight to the gear legs when I got the cowling off. Looked like cracks on both sides. Right side turned out to be dirt. Left side however looked like the powder coat was cracked. Used a very fine sandpaper and cleaned it up some more. What do y'all think?

RV6 with 1085 tac hours. Only grass is taxing at OSH 😎

2db1fs0.jpg
[/IMG]
 
I started my annual condition inspection just after I read this article and I went straight to the gear legs when I got the cowling off. Looked like cracks on both sides. Right side turned out to be dirt. Left side however looked like the powder coat was cracked. Used a very fine sandpaper and cleaned it up some more. What do y'all think?

RV6 with 1085 tac hours. Only grass is taxing at OSH 😎

2db1fs0.jpg
[/IMG]

Hard to tell from that pic.
Remove the powder coat with paint remover to bare metal and inspect further. If your mount does not have the gussets, ie later style 7 mount, it is probably a matter of when, not if.
 
it is probably a matter of when, not if.
So just order the gussets from vans and fix it properly. Yea probability the best call. Gary Sobek is giving me info on how to do it without removing the engine from the mount.
 
Gusset Instructions

Mike, I sure hope you will post those instructions here when you get them. I have to check very closely as I thought it was just cracks in the powder coating. I am sure there are many of us out here without gussets on older models.

Thanks, Al
 
Gary Sobek is giving me info on how to do it without removing the engine from the mount.
Not knocking Gary by any means.
I have done this job.
Removed mount from plane.
Stripped to bare metal.
Had crack welded and added Vans Gussets....cheap and fit perfectly,.
The gussets mount on the bottom of the triangle at the bottom of the socket.
I saw my mount on the welders table being welded!
Cleaned it up again, primed and epoxy painted....
So good or better than new.

I can only speculate on how it would be installed while still attached to the engine....hanging from a hoist, engine wrapped with something to protect the engine and oil and gas fumes etc....

Also if your plane is high time...and for me I had 1100TT in 20 years so I took the opportunity to remove/strip/inspect/fix and repaint! I also removed the gear and cleaned/inspected/straightened and repainted as well.

So I would be interested in hearing a procedure to do it while mounted as well. I can always learn something and most days do!
 
Still Thinking

Bob

I am still trying to decide what to do. Gary is an engineer and very skilled. I on the other hand am as ordinary as anyone can get and was thinking the same thing welding with the engine on a swing might be interesting to say the least. I did not build the plane I adopted it from the builder about 500 hours ago. I will be needing assistance no matter what I choose to do.

I sure do not want to pull the engine but I would rather be safe and get a good look at the mount. Well have someone that knows what the heck they are doing take a look. It will be a learning experience for me no matter what which in the long run is a big plus.

Any way waiting to talk to my A&P (& friend) before I decide what the heck to do.
 
I'm just home after finishing my repair.

I've spent 24 of the last 48 hours working on it. It was welded for me Friday, Painted friday night and then all day Saturday and Sunday to re assemble and test run.

I'd say It's taken about 50 hours work to do the whole thing including welding (2), Stripping and Painting (10) and putting it all back together again (24). I did manage to get a few other jobs done at the same time though - oil change, air filter clean, secure spat mounting brackets, replace a fuel hose.

Ready to test fly if the weather is any good in the morning. I'll post some photos as soon as I get chance.

Beer time !
 
Hard to tell from that pic.
Remove the powder coat with paint remover to bare metal and inspect further. If your mount does not have the gussets, ie later style 7 mount, it is probably a matter of when, not if.

I'd found that Dye penetrant testing on mine was really the only way to be absolutely certain. The kit cost ?36 .... no doubt I'll be using it again in the future some time.
 
All finished and test flown, so far so good.

As mentioned before, I'd estimate about 50 hours work all told - although this did include a few small "incidental" jobs as well.

The only real snag worth mentioning was that when removing the mount a center bolt went back into a metal fuel line behind just the firewall. This in turn resulted in a fuel leak on the outlet of the Andair pump which is just in front of the main spar. I was very lucky to get away with this - It started up and ran fine for 7 mins during initial warm up but then started miss firing during my "1 min at max power" final ground run before flying. The pipe had fully fractured on the flare so a 3/8" pipe @ 30 psi leak !

Here's some photos.

(Edited 5th April 2017 - It turns out that the end plates I have fitted in the photos below are not to the approved UK Mod spec, my mistake but please don't copy them !.)

[url=https://flic.kr/p/SmRjfQ]IMG_3431 by WIGY TV, on Flickr[/URL]

33436797985_15d4df2024_b.jpg
[/url]IMG_3430 by WIGY TV, on Flickr[/IMG]

33436798305_710d112ebc_b.jpg
[/url]IMG_3429 by WIGY TV, on Flickr[/IMG]

33053788600_9947172d7e_b.jpg
[/url]IMG_3433 by WIGY TV, on Flickr[/IMG]
 
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pictures

Nice pictures...thanks for sharing.
Nice Job welding gussets.
But just to be clear that is not the WD-762A-L and WD-762A-R Gear Socket Gussets Vans sells for the Dynafocal mounts.
Is that a homebrew or did Vans direct it for a Conical mount?
You did not show a picture of the bottom view of the small triangle at the tube where the Vans gussets fit.
Again, nice work!
 
Hi Bob,

The gussets are from drawings often referred to as the "Netherthorpe mod" here in England. It's an LAA "Repeat mod" first done on G-ODEE in 2004. It seems almost every UK aircraft I look at has had this done

They are basically home made from 1/8" 4130 Steel plate, 4 parts are added - the elongated triangles (welded top & bottom) and the roughly 2 x 2" end plates welded to the mount ends.

Cheers,

Richard
 
Cowl

Have you put the cowl on yet? From the picture it looks as if there is an area that is going to be close to the cowl at the landing gear.
 
Richard,
Thanks for the reply.
1/8 is thicker than the Van's gussets.
12 years of history says something!
All good info. Best pictures I have seen posted regarding the fix.
Thanks
 
The cracking is very common for high time RV-6s and RV-6s that operate off of grass. The fix is to install the WD-762A-L and WD-762A-R Gear Socket Gusset to engine mount that is used on the RV-7.

At 2,724 hobbs hours, I added the gussets to my mount.

Here is what the gusset looks like on my spare engine mount.








Welding done by a professional Aerospace welder.

Here is a video clip of one of the gussets.
https://youtu.be/7MBCb1X-Z2c
 
Nice example

Gary,
Nice work, good example of the repair.
Thanks for pictures.
Of all my spare parts...I never thought to keep a "spare" engine mount!
 
I just found the same crack, on the right side on my RV-6 after 1450 hours. The left side cracked and was repaired a few years ago. This time the mount came off for the gusset mod, and it's over at Aerospace Welding in Eagan, MN for the full treatment. One less thing to worry about later.
 
OK, you have me frightened now. My -9, mount vintage 2009, doesn't have those additional horizontal braces.

I guess I'll be taking a closer look at my lower mounts the next time the cowling comes off.

Thanks for the great write-up!
 
Engine Mount Cracking

I've owned An RV-3,4 & 6 all have the combined engine/gear mount. I've had to do this twice now on the -3 and the -6 (the -4 is not old enough yet). It's common/engineered fatigue issue and RV with this mount configuration should inspect for cracked mounts around the landing gear on every annual and I like to look at them every time I have the cowl off. It's really not a big deal to fix actually and you can do it without fully pulling the engine all the way off. If it's simple it should take about a week and $100, two (of both) if you wish it bead blasted to strip it all the way down.

..oh, I personally would avoid "beefing up" these joints. This is a designed break-point. Making it stronger will cause more expensive parts (like airframes/firewalls) to get damaged when you do bad things. It's a _LOT_ cheaper to re-weld a twisted engine mount that rebuild a firewall or throw away a bent fuselage.

My point is that proven and well-engineered designs are built and time-tested for a reason. Alterations, even seemingly well-intentioned and small changes like these have unintended consequences.
 
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I found a small, hairline crack at the lowest weld on the aft side of both gear leg sockets after a few years of flying my RV-6. I watched the cracks for several years and they didn't spread. In spite of not being able to see how these defects could lead to a gear or mount failure, three years ago I pulled the mount away from the firewall far enough to run a weld bead over the cracks.....just because.

By next condition inspection a small crack had appeared at the edge of one of the new welds. I've decided this is something I can live with since this appears to be a compression failure where the mount is very unlikely to ever fail and I've never seen a crack grow to more than 1/2" long in this area. I will continue to monitor this situation but doubt I will ever feel the urge to repair it again.

At least until some sharp-eyed A&P sees it during a pre-buy someday. :)
 
While completing my Condition Inspection I noticed a crack.

The crack is on the bottom horizontal tube, just inboard of the short bracing tube that ties the gear leg tube to that horizontal tube.

My engine mount is circa 2009 and supports an O-360. There are no gussets on this mount.

The current manufacture of the mounts, which is different than the person who made my mount, said he now machines the gear leg tubes rather than nesting and welding two tubes.

The mount will come off and be sent to www.super-12.com where Steve will create a jig from my mount to make sure the six firewall bolts and the dynafocal mounts are all in the same place in space. This is important to make sure the mount will bolt back up and the prop/spinner will match the cowl.

Once my mount is in his jig, Steve will cut out the cracked tube and the old gear leg tubes and weld in the new machined gear leg tubes, cross tube, and gussets. Then it will have to be drilled to match my gear legs.

Next time you have your cowl off, please inspect it carefully for cracks.
 
Great Info

Just found these cracks in my 1998 Syd Nelson RV-6. Hard to see but they are there on both main gear mounts.

Remember reading this thread 9-months ago, was looking for it when a link was provided.

Just wanted to say Thank You to all posted photos and great explanations/examples!

Best regards,
Mike Bauer
 
My RV7's mount has the gussets. By 300 hours the gussets had cracked and needed to be rewelded. You might rethink the placement of the gussets and the thickness of the gussets. Every time you land the gusset is in compression; perhaps if it was a bit a bit thicker material it would be able to not flex enough to fatigue.
 
There comes a time in every RV-6's life.....

We were doing the annual on Louise's RV-6 this past week, and sure enough - the cracks have appeared. It's remarkable, actually, that it took over 3500 hours and 30 years for us to see the problem (although there are some reports it might have happened before - but I don't see a previous repair on this mount...), especially since this is kit #4, and there are no gussets.

So the engine is coming off, and the mount will find its way to the Greater Portland area will Russ will work his welding magic, fix the problem, and add the gussets. And meanwhile, we'll do some FWF clean-up. This has been (and will continue to be) a strong, working airplane!

Paul
 
There comes a time in every RV-6's life.....

We were doing the annual on Louise's RV-6 this past week, and sure enough - the cracks have appeared. It's remarkable, actually, that it took over 3500 hours and 30 years for us to see the problem (although there are some reports it might have happened before - but I don't see a previous repair on this mount...), especially since this is kit #4, and there are no gussets.

So the engine is coming off, and the mount will find its way to the Greater Portland area will Russ will work his welding magic, fix the problem, and add the gussets. And meanwhile, we'll do some FWF clean-up. This has been (and will continue to be) a strong, working airplane!

Paul

That is amazing! I am glad I have the gussets as I have made more than a few landings that should have broken something, although I think most cracks in engine mounts are fatigue.
I fancy myself as a decent welder. Then I watch Russ, and realize I am a hack. He is the best and you will get a fine product back.
 
I had serious cracks in my -6 mount. I welded the cracks after removing the mount, and welded a heavy ring around the bottom of the gear leg and over the cracks after smoothing the weld beads over. Rather than adding gussets I made multiple passes from the bottom of the bolt tubes to the heavy ring. I believe what I came up with is stronger than gussets.
 
Thanks Jon!

That is amazing! I am glad I have the gussets as I have made more than a few landings that should have broken something, although I think most cracks in engine mounts are fatigue.
I fancy myself as a decent welder. Then I watch Russ, and realize I am a hack. He is the best and you will get a fine product back.

Thanks Jon!
 
Looking forward to your visit!

There comes a time in every RV-6's life.....

We were doing the annual on Louise's RV-6 this past week, and sure enough - the cracks have appeared. It's remarkable, actually, that it took over 3500 hours and 30 years for us to see the problem (although there are some reports it might have happened before - but I don't see a previous repair on this mount...), especially since this is kit #4, and there are no gussets.

So the engine is coming off, and the mount will find its way to the Greater Portland area will Russ will work his welding magic, fix the problem, and add the gussets. And meanwhile, we'll do some FWF clean-up. This has been (and will continue to be) a strong, working airplane!

Paul

Looking forward to your visit!
 
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