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cylinder nuts

hmgm123

hmgm123

Well-known member
Has anyone had problems with a supercharge motor cylinders nuts coming loose? If so I was wondering if they should have a lock washer and also the nuts have holes in them so you can put twine and connect them together. I was thinking of doing that myself.
 
Were the base nuts torqued with the thread lubricant recommended by Lycoming?

90% 50wt mineral oil and 10% STP. Really. Right out of the overhaul manual. It works.
The only way to get a true torque on those base nuts. If you don't they will loosen up.

An A&P friend of mine helped me with an engine and stressed the importance of this.

From Sacramento Sky Ranch:
Were the studs improperly torqued?

Clamping force from torque is no more accurate than the predicted value of thread friction in the fastener. If we apply 40 foot pounds of torque to a stud, without thread friction, torque energy stretches the stud in tension and tightens the joint. Threads that are dirty, painted, or damaged have lots of friction. Torque energy twists instead of stretches the stud. Very little energy goes to stretching the stud and the joint is loose. The engineer who specifies the amount of torque assumes a friction value for the threads. To make sure this value exists at the time of torque he may specify the type of thread lubricant to use while torquing the stud. To get the correct preload the threads should be clean, undamaged, and lubricated with the manufacturer's specified thread lubricant. Among lubricants that Lycoming specifies is 90% SAE 50W engine oil and 10% STP. Continental, for example, has in the past specified Oil Grade 50, MHS27 for cylinder studs and through-bolts.


Anyway this might help.
 
I had a cylinder nut come loose on my 0-360 and go through the prop. It is worth taking the extra time to safety wire the nuts just in case. It would have saved me some money.
 
Believe it or not I just got done reading the same article. :lol: I have mechanic that doesn't believe in putting wire through the nuts doesn't think it is neccessary. As for the lub I going to try that my self I had one clinder come loose on me last night tighten up and it came loose again less that 10 min running time. I am also going to put the wire though all the nuts on the cylinder at least it won't come totally off.
 
You know what's funny is that the acorn nuts that are drilled for safety wire are not available any more. Replacements you purchase do not have holes for safety wire. If you need some there is a place out west that sells them used in "servicable" condition a lot cheaper than new. If you need some I.M. me and I'll get the number for you.
 
I've rebuilt a lot of aircraft engines and I've never had a base nut come loose on an aircraft cylinder. A couple of cautions need to be taken during installation. First make sure they are base nuts. The studs need to be oiled as previously stated before they are torqued. Torque them in an offset pattern. Make sure there is no paint on the cylinder surface where the nut contacts the base.

If a nut comes loose there is another problem that should be addressed. The manufactures recommendations in their overhaul manuals tell everything that is needed in assembling the engine. Use the base nuts that the manufacture recommends.
 
Most companies that supply the aircraft market (aircraftspruce.com) have a little fixture that you can use with a drill press to bore a safety wire hole in any nut.
I like to safety wire anything that will get expensive or dangerous if it gets loose.

olf
 
I have to agree with you on that Olf. I've never had a prop come loose either, but they are always safety wired.

I re-learned a lesson on my last boat. If it moves it gets a castle nut and cotter pin. I had a nylon lock tight nut come loose on my rudder cable one day and WOW what a suprise when I spun a 360 and ended up on the sand bar. I'm glad I wasn't next to a tree or stump.

You're right about drilling any nut to accept safety wire. It sure can't hurt to safety anything. Especially if it gives you piece of mind.
 
Well what gets me is my mechanic doesn't think it is necessary to safety wire the nuts. They all have holes to do so. So why not do it??? Well I'm going to take every one advice and do it myself. :violent1:
 
I don't mean to be the bearer of bad news, but if you had a cylinder come loose after ten minutes of run time, you've got something else going on there. I don't think safety wire is going to solve your problem. I'd tear it off and check the studs a little closer. Let us know what you find out.
 
One nice and easy safety is to double-nut things that you think would be a problem if they loosened.
It only costs 30 seconds and the price of another nut.

Another basic rule is to always install a bolt with the head up, or in the direction on rotation. If the bolt loosens, it still won't fall out.

Hmgm, the studs may be pulling out of the case. Not saying they are, but 10 min. isn't a long time if they were properly torqued. If they are, they can be heli-coiled.

olf
 
I WORK ON UNCLE SAMS AIRCRAFT EVERY THING IS SAFETY WIRED AND FOR A GOOD REASON ITS A PAIN SOMETIMES BUT IT WILL SAVE YOU ALOT OF HEARTACHE.
 
5gen, the mechanics used to like to remind us that it was .031 safety wire and not talent that kept us in the air ...... :lol: .

olf
 
Olf

Where did you get that little jig to hold the nuts for drilling in the drill press? Inquiring minds need to know :)

Scotty
 
Bear, go to Aircraft Spruce's website. They're great folks ..... been dealing with them for years. Request a catalog. They'll be happy to send you one. It's great reading too ..... lots of toys 8) .

olf
 
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