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Engine mounting hardware - did vans change the hardware?

MS19087

Well Known Member
Getting ready to mount my engine. Reviewing drawing 43. The drawing calls out lock nuts vs castle nuts and cotter pins for the four engine mount bolts. The FWF kit details castle nuts and cotter pins and this is the hardware I have. Does anyone have any information on this ? Did vans change this detail?
 
Yes! My -7 has cotters; my buddy's -7A (a few years behind me) has metal lock nuts. SO much easier to install!
 
Ok. Why the change?

Thanks Scott. Any explanation why? My last RV used castle nuts and cotter pins. Why the change? The FWF kit recently had this hardware called out. I don’t see any SB or service letter.
 
Thank God

When I installed my new engine (replacing the XP-400) I used all metal lock nuts. When I originally installed the XP-400 the geometry of the case where the nuts go made it next to impossible to torque the nuts AND get the cotter pins in and bent over because one had to insert the cotter pin then rotate the bolt 180 degrees to be able to bend the cotter pin over. Inevitably the bolt would turn but the nut wouldn’t and the cotter pin would get jammed against the nut. When I removed the XP-400 it was a real bear to get the cotter pins out. That’s when I decided to go with all metal lock nuts/undrilled bolts when I mounted the new engine which was built using my XP-400 case/sump and all new everything else.
 
When I installed my new engine (replacing the XP-400) I used all metal lock nuts. When I originally installed the XP-400 the geometry of the case where the nuts go made it next to impossible to torque the nuts AND get the cotter pins in and bent over because one had to insert the cotter pin then rotate the bolt 180 degrees to be able to bend the cotter pin over. Inevitably the bolt would turn but the nut wouldn’t and the cotter pin would get jammed against the nut. When I removed the XP-400 it was a real bear to get the cotter pins out. That’s when I decided to go with all metal lock nuts/undrilled bolts when I mounted the new engine which was built using my XP-400 case/sump and all new everything else.

This isn't something unique to your XP-400. It has always been challenging on any 4 cyl dynafocal Lycoming style engine.

Design changes on RV kits aren't only made for things that service history shows to be necessary (usually issued with an SB or notification). Far more often they are made as improvements to a kit in areas that a lot of builders are challenged with.

That is the reason in this case as well.

Changing to self locking nuts brings the RV-14 kit in line with what many certificated aircraft have been doing for w while now, rather than just following the path of tradition.

When a change is made as just a general kit improvement, it will not usually be issued under a Notification or SB because it is not considered to be for a potential safety of flight issue, or performance improvement of the part(s). It is likely that it just makes things easier or it is a substitution for a part that has become obsolete or what we consider to be excessively over priced.

So the next question likely to be asked is why hasn't the hardware call out been changed for all the other models?

The answer is that it would steal far more resources than anyone outside of Van's can imagine, to make changes to all of the different packing lists, and plans pages for all of the different models.
In this instance, an improved version of the FWF kit was being introduced so many packing lists and plans pages were already being revised. That makes it a very simple process in this case.
 
Thanks Scott. Any explanation why? My last RV used castle nuts and cotter pins. Why the change? The FWF kit recently had this hardware called out. I don’t see any SB or service letter.

Not Scott, but as others have said, using the lock nuts and in-drilled bolts is far easier than trying to get cotter pins in. If you look through the usual certified airplane suspects, you’ll find that at least half (if not more) are using locknuts rather than cotter pins, so the engineering is probably there to support their use.

When we overhauled the engine on the RV-6 this year, I changed to the locknut configuration, since we already have that on a couple of other airplanes in the fleet, and it sure saves some bad words for other frustrating assembly procedures....

Paul
 
When I installed my new engine (replacing the XP-400) I used all metal lock nuts. When I originally installed the XP-400 the geometry of the case where the nuts go made it next to impossible to torque the nuts AND get the cotter pins in and bent over because one had to insert the cotter pin then rotate the bolt 180 degrees to be able to bend the cotter pin over. Inevitably the bolt would turn but the nut wouldn’t and the cotter pin would get jammed against the nut. When I removed the XP-400 it was a real bear to get the cotter pins out. That’s when I decided to go with all metal lock nuts/undrilled bolts when I mounted the new engine which was built using my XP-400 case/sump and all new everything else.

With the cotter pin in, how could the bolt turn without turning the nut?

When I replaced my Lord mounts, I torqued the bolts with the drag figured in. I installed the cotter pins as far as they would go, then I turned the bolt, along with the nut and the cotter pin as I continued to push the pin in until the pin was in a location that I was able to secure it to the nut. It was no big deal.
 
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