Washers under castle nuts

RVG8tor · #1 02-09-2012, 09:19 AM

I had another builder over the other day, and when he looked at my engine he commented about the 3 washers (2 regular and one thin) that I had under the castle nut on the Dyna-focal engine mount bolts (bolt thru firewall and mount). I was thrown, I started digging and can't seem to find an answer.

In AC43 is talks about attachments of nuts and bolts and max of 1/8" of washers to get the fit, meaning if you need more washers then perhaps you need to go to the next size bolt (grip issue). This seems different than getting the cotter hole to line up with a castle nut. AC 43 does not address amount of washers for castle nut alignment.

I think why I did what I did was the plan has a note on DWG 49 that says "it may take several washer", to me "several" means more than 3. Wouldn't the plan supersede the AC43 since the connection has been engineered. My engine is already mounted and I hate to move washers around.

Have others run into this, is there a limit on the number of washers under the castle nut for cotter alignment (not talking grip here). I can take the thin washer out and the cotter still does it's job but does not sit as deep in the groove on the nut. There is another question, is there a minimum depth the cotter must sit in the groove.

Hope to hear if this will pass inspection or not. I could not find specific answers in the search mode so I thought I would bring up this issue for future users.

Cheers

flyinga · #2 02-09-2012, 09:22 AM

I had the same thing on my 8; several wshers (3 I think) under one or more of the bolts as per the plans. Build on.

jrs14855 · #3 02-09-2012, 09:45 AM

Not just RV's but other aircraft as well, the callout on dynafocal bolt length is one dash number too long on two of the bolts. Two standard washers equals one dash number on length.

az_gila · #4 02-09-2012, 10:05 AM

In general, the manufacturer/designer's instructions override the generic standards in AC 43.13.

Go with the plans.

Captain_John · #5 02-09-2012, 02:39 PM

I agree with all above. You should not fall out of the sky in a ball of flames as a result of installing 3 washers under the nut side!

I just installed my engine mount and discovered the same thing.

Just pointing out the obvious to those who are getting close to this point; I installed one washer on the head side and two under the nut side.

This was only necessary (for me anyways) on the two top bolts.

YMMV...

CJ