nuts with nylon inserts versus lock washers and jamb nuts

[mm]

I bought one of those little kit trailers, what you can get for about

350 dollars, with a 4x8' bed, for a one time use, and some little uses aftewrads. From Harbor Freight that carries 990 pounds they say. I only need to carry less than 100.

Assembling it today, I noticed that they depend on nuts with nylon inserts to keep the nuts from coming all the way off. They depend on tightening them tighlly to keep them from coming loose.

Is that enough or should I put split ring lock washers under each nut.

Or would it be better, just as good, to put jamb nuts on the bolts that are long enough.

IIRC the instructions say in one place to check that the nuts are tight after 100 miles, which seems like a good idea, but in another place I think it said every 100 miles!!!!!

Thanks

[Red Green]

mm wrote in news: [e-mail]:

Yes even if they come loose they won't vibrate off and allow disconnection. Built a custom motorcycle when I was a kid. Would not use anything else but those. They were also used by the original manufacturer before I chopped it.

Their lawyer assisted in instructions.

[PV]

To be really sure nothing will vibrate loose, use blue locktite along with the nylon insert nuts. Works like a charm especially in high vibration environments.

[RBM]

When I would build the shelving racks in my service vans, I always used split ring lock washers and lock-tite, but due to the constant vibration, it was a never ending battle to keep things tight. On the last two vans I set up, I had discovered the nylon lock nuts, and nothing has ever come loose since

[N8N]

I have heard from several authoritative sources that lock washers really don't do much more than a properly torqued nut and flat washer alone. The Nylocks are definitely an improvement. Anymore I only use the split washers where they were originally used to keep an original look but if I am building something from scratch I use either Loctite or Nylocks.

nate

[Jeff]

Nylon lock nuts came from the aircraft industry to solve the problem of nuts loosening due to prop engine vibrations. Always used them when I made model airplanes. Painting the threads after the nut is tight with finger nail polish is a good idea as a backup as well or use a product such as locktite.

[Pete C.]

The key difference between the nylock nuts and a conventional nut with a lockwasher is that while either one may work loose from the tight state, after that point, the nylock will stay put on the bolt, while the conventional nut and lockwasher have no retention after the compression of the lockwasher is lost and will continue to turn with vibration until the nut completely falls off.

[Pete C.]

Castle nuts have notches in them and are used with cotter pins. You're thinking of an interference nut which is deformed by several crimps and produces a tight fit. These don't work any better or worse than the nylocks, both will have reduced friction with repeated installation-removal cycles, and both resist continued loosening if they do come loose since they have friction. Conventional nuts and lockwashers have no friction once they loosen past the point of compressing the lockwasher and will continue to loosen until they fall off. For positive locking use the castle nuts and cotter pins.

[BobR]

Let me put it this way...I am building an airplane and using the nylon insert nuts for most applications with a few critical exceptions where only a castle nut and cotter pin is acceptable. I don't use and wouldn't even consider using lock washers on anything. On the nylon insert lock nuts I add a dab of bright colored paint across the thread and onto the nut in one small area. This will give a visual clue if the nut should move following installation.

PS: If you are really into the belt and suspenders approach, there are castle nuts with nylon locking inserts as well.

[dpb]

BobR wrote: ...

I don't know airframe rules, but if you mean "anything" within the ordinary English meaning, that's simply silly...

--

[SteveB]

My experience with Nylocks is this:

They are good for some applications. They are not good for others. They are a one time use thing, as once they are run on and off one time, the holding power is diminished a lot. I know they make them in all sizes up to double jumbo, but for something I really want to know is going to stay put, I'd prefer personally to use lock washers or even double nutting with a jam nut. I have yet to have a jammed jam nut come loose. OTOH, like you, I have had new Nylocks loosen up soon after installation. IIRC, there is a nut called a castle nut that has a small crimp in it, and fits tight tight tight on installation and is dependable not to work loose, and if it does not loosen, it won't just vibrate off once it gets just so loose. The crimps keeps a grip on the bolt, and cannot be taken off without a wrench.

Just my two pennies, your mileage may and probably does vary.

Steve

[DerbyDad03]

Another key application for nylock nuts is that they can be left slightly loose for those instances where you want to allow for movement such as at pivot points. You can obtain a snug fit so things aren't flopping around, but you can still move the parts.

All steering assemblies and some brake assemblies on official All American Soap Box Derby cars use nylock nuts for this very purpose. In fact, by rule, the steering assemblies require *two* nylock nuts on the same bolt. Talk about overkill!

[tnom]

As long as the Nylocks do not have many cycles on them you can use them without fear of loosening. Loctite is not needed. The only thing that will loosen a Nylock is a wrench, not vibration.

[BobR]

When building a plane, if the screw or bolt is important enough to have any lock washer it is important to make sure you use one that won't come loose. If you consider that silly, do your wife and all of us on the ground a favor and don't build yourself an airplane.

[dpb]

[BobR]

I read it, understood it completely and really considered you rather silly for having written it. You had nothing useful to add so you wasted everyones time.

[dpb]

BobR wrote: ...

No more than your silly comment aka "recommendation" ...

You replace every lock washer on every piece of equipment you buy since they obviously are unsafe?

--

[mm]

There is so much help here from many of you, rather than several replies, I'm going to thank everyone here -- Thank you -- and followup here.

I'm very encouraged about the nylon inserts. My one concern still is that somehow they use a different kind of nylon in China that won't work as well?

As it turns out, I bought the trailer 15 months ago and had it shipped to my brother. The instructions didn't show lock washers for any of the bolts I'd gotten to when I posted, but yesterday I got to the 4 square U-bolts that hold on the axle and the instructions said they used lock washers. But none were enclosed.

I had downloaded the instructoins from Harbor Freight, and they have changed them in the last 15 months and the new instructions show NO lock washers. Surely this isn't to save money, so they must think it's as good or better. Yet after reading all your posts, I'm still going to use them under those 8 nuts, because it seems like it can't make it worse. ??

FTR, my instructions showed a mixture of English and metric bolts, but the only bolts enclosed were metric. The new online instructions now correct some slight mistakes and also match the bolts etc. that they enclosed, except that neither mention that I need a grease or a grease gun, maybe.

There is some grease on the bearings, but after I put the hub and bearing on the axle, am I supposed to use the grease fitting to fill the whole chamber with wheel bearing grease? All it says it to fill the cap at the end with grease.

[SteveB]

WOW. From now on when I go on a plane, I'm going to look to see what kind of system they use. I really don't think I've seen a lock washer yet. Most of the stuff I see has plastic push fasteners. I must be dense as a rock. I thought they would use all sorts of fasteners depending on the application. Now to find out they use only a few. Oh, dopey me.

Steve

[BobR]

Now is that what I said or did you take it out of context knowing full well that my comments were in reference to the aircraft? You knew but you just couldn't resist making a stupid comment since you had nothing constructive to add. Now take you stupid comments and put them where they belong. As for lock washers, no I would not use them any application where safety was an issue. I have had too many of the work loose to rely on them.