I'm reading the Malone Microsport XT assembly manual (on order).

http://maloneautoracks.com/pdf/MPG460XT.pdf

In the manual, it indicates that some bolts have washers, some bolts have no washers.

Question: paranoid that I am, I was thinking about using loctite for each bolt/nut as well as lock washers.

Should I follow the assembly guide? Is it a good idea to use loctite for each bolt/nut? Is it a good idea to use lock washers for each bolt/nut; or only where washers are used; or not at all? When is it good to use lock washers and when should they not be used (or any washers -- not sure why some bolts do not use any washer)?

Back when I used to be a mechanical engineer, here's what we did.

If you properly torque a bolt, it won't come loose.

The problem is, a properly torqued bolt exerts a LOT of force.

If everything you are bolting together can take the force of a properly torqued bolt (i.e., if everything you are bolting together is metal, and either solid or with thick enough walls), then you just properly torque the bolt.

If something you're bolting is plastic or thin-walled metal or otherwise too weak to take a properly torqued bolt, then you use thread locker or a lock washer or a nylock nut (my preference).

We basically always used flat washers on everything, even if we also used lock washers. They are most important to put under the head of the bolt when the bolt-hole is very tightly toleranced to the diameter of the bolt.

Looks like all the nuts are of the self locking type.
You want at least a couple of treads showing for the lock nut to work correctly, too many washers could make the locknut not work as it should.

Loctite couldn't hurt in this case.
The bolts are probably not torqued to t
heir proper torque and are probably Chinese stuff. Also the trailer will be twisted and shaken and subject to heating/cooling, weather, etc.
Anywhere there is a nut on one end, nylock nuts would be a good idea.

Are the nylock (is that the self locking nut that comes w/ this trailer kit?) secure and heat tolerant? If this is sitting in the sun and also being submerged in water, will these nylock nuts last? Or should I use a little loctite here as well?

Just don't want the trailer to disintegrate on me while I'm rolling down the highway someday...

Also, given 3/8" bolts, I assume loctite blue is enough. Or are you guys thinking red may be indicated (especially for frame bolts)?

Proper torque is the way to go. I'm going to go against the grain and say Loctite isn't going to help if the torque isn't done right because that's going to be subject to a lot of direct vibration.

I would feel more secure with split ring lock washers.

Assuming the pictures in the attached manual really are the hardware that comes with the trailer, it looks like all the nuts are nylon insert type locknuts. There are also a number of carriage bolts which are designed to fit into the square holes in the frame, so those would probably be the ones that don't require washers. Also the previous comment about making sure 2-3 threads are exposed past the end of the nut still stands, so be careful using washers where not specified. Also I wouldn't use loctite and nylock nuts on the same bolt. Just make sure everything is properly tightened and you should be fine.

We use those lock nuts all over the Helo I worked on without issue and Helo's vibrate a lot and we deployed to areas that get really damn hot. The only issue I've ever seen is ones that get taken on and off a lot, sometimes they'll lose torque.
As far as loc-tight either would work I'd think.

quote:

Originally posted by spike86:
Assuming the pictures in the attached manual really are the hardware that comes with the trailer, it looks like all the nuts are nylon insert type locknuts.

Aka: "Nyloc" nuts.

quote:

Originally posted by navyshooter:
The only issue I've ever seen is ones that get taken on and off a lot, sometimes they'll lose torque.

The nylon, or whatever material they use, will wear with repeated assembly/disassembly. Then it doesn't hold so well any more.

The material in a Nyloc nut performs much the same role as Loctite or nail polish: It increases the coefficient of friction in an elastic manner, so it's not entirely dependent upon torque.

If the nuts are Nyloc, you shouldn't need either lock washers (split, star, spring, dish, what-have-you) or Loctite.

When in doubt, follow the manufacturers directions.
I understand the concern for your stuff and your fellow man in never wanting the trailer to fail on the road but consider there are thousands of these that are assembled following the directions.
They're still on the road. And if they did fail, they have recourse against the company because they followed the companies directions. Change them on your own and you don't.

They are giving you locking nuts for a reason, use them.
If they don't say "add loctite", don't. Those nylock nuts are the good stuff.

quote:

Originally posted by konata88:
Are the nylock (is that the self locking nut that comes w/ this trailer kit?) secure and heat tolerant? If this is sitting in the sun and also being submerged in water, will these nylock nuts last? Or should I use a little loctite here as well?

Just don't want the trailer to disintegrate on me while I'm rolling down the highway someday...

Nylock nuts are used on boat trailers without lock washers or Loc-tite (think large capacity like 18k lbs) among many other types of assemblies.

quote:

Originally posted by ensigmatic:
The material in a Nyloc nut performs much the same role as Loctite or nail polish: It increases the coefficient of friction in an elastic manner, so it's not entirely dependent upon torque.

Loctite is an adhesive - when you use it, you're literally gluing the nut and bolt together. It isn't really dependent on friction or coefficient of friction.

Nylock nuts do work via friction, but it's not really about increasing the coefficient of friction.

In nontechnical terms, the amount of force friction can resist before movement occurs between two surfaces that are touching each other is the coefficient of friction between the two surface times the force pressing the two surfaces together.

In a properly torqued nut-and-bolt connection, the clamping force exerted by the nut-and-bolt presses the faces of the threads of the nut against the faces of the threads of the bolt REALLY HARD. The coefficient of friction between two steel surfaces is pretty small, but that pretty small coefficient times the very large clamping force results in enough friction force to resist loosening from vibration.

Nylon is pretty slippery stuff. Steel-on-nylon might have a higher coefficient of friction than steel-on-steel or it might not (I would bet it can go either way depending on the surface finish and condition of the steel, plus the presence or absence of lubricants or contaminants), but it doesn't really matter. You use nylock nuts where you can't torque the fasteners down, so there isn't enough clamping force to generate enough friction to keep the fastener from loosening.

So what you do, is you make a channel inside your nut, and you put a nylon washer in the channel. The hole in the nylon washer is smaller than the diameter of the bolt. When you put the nylock nut on a bolt, the bolt compresses the nylon washer against the inside of the channel in the nut - causing the nylon washer to "squeeze" the bolt REALLY HARD. The small coefficient of friction between steel and nylon times the large force exerted by the bolt compressing the nylon washer results in enough friction force to resist loosening from vibration.

The reason this doesn't depend very much on coefficient of friction is that if the coefficient of friction is lower, you can just make it so that the nylon (or whatever) washer gets compressed more, exerting a larger force, resulting in more friction.

This also explains why repeated application of nylock nuts can result in the nuts not holding - the sharp threads of the bolt can cut into the nylon so that it doesn't get properly compressed any more, or the nylon can become permanently deformed from repeated tightening and loosening of the fastener.

Thanks guys.

Okay - if a nut is Nylock (or some nut with nylon inside) then I will use that without a lock nut or loctite.

If a nut is not Nylock, then I will add a lock washer or use loctite. And always ensure at least 3 threads are exposed past the nut.

If I ever remove a nylock nut, then I will buy new ones.

Thanks for the help. I just don't know when something is mechanically engineering sufficient and when the manufacturing is just being cheap (ignoring Murphy).

And now, on to understanding the nightmare of what I need to do, if anything, with the DMV. Confused at this point.

Do not use locktite on nylock nuts, and a lock washer is not needed.

It's untrue that a properly torqued bolt will not come loose. That's why many properly torqued bolts on aircraft are secured with safety wire...because they can come loose.

Torque is thought to be rotational force, and it's not. It involves bolt stretch, and is about tightening without breaking a bolt, as well as applying even force between fasteners on two parts. It's about stress on the parts, rather than making them tight so they don't come apart. Most mechanics don't understand this.

Flat washers are placed under a nut (not under a bolt head) to reduce rotational stress of the nut on the part being secured. It allows compression without rotation to be applied to the part.

If a lock washer is placed under a nut (not needed with self-locking nuts; ie nylock, etc) and a lock washer is desired, the lock washer should be between the nut and the flat washer. Do not place it between the flat washer and the part as it will do no good.

Do not put a lock washer under a bolt head. The only time that has value is a blind bolt application where the threaded end of the bolt is i a tapped surface (eg, places where you're not putting a nut on the bolt). In that case, use a flat washer under the bolt head, and a lock washer between the bolt head and the flat washer.

It's best not to reuse self-locking nuts, but if you do, insure that each nut cannot be rotated onto the threaded portion of bolt by finger pressure alone; if it can, consider it failed, and get a new nut.

If you have a self-locking nut which can be threaded onto the fastener by finger pressure (in other words, it's failed), do not use it again, and do not apply locktite to attempt to make it work.

Where a manufacturer has given specific directions for types of fasteners, washers, etc, it's best not to attempt to reinvent the wheel. You can quickly defeat the engineering that went into the part, and you may not know the reasons why the particular components have been called out for that assembly. Putting the wrong washer, bolt, nut, etc, can have unintended consequences and can lead to loss of torque, loss of the parts, failure of parts, stresses where they ought not, imbalance on rotating or moving parts, and so forth. Placing washers in the wrong place or even in the wrong order can cause loss of fasteners and can set in motion a cascading series of events; this faster fails, putting increased load on that, which fails, which causes another to fail, etc. I've seen that occur a number of times in various applications. Use what's specified, in the manner it's specified.

Much of the time, when problems occur, it's because someone thought they were smarter than the engineers who designed the component, part, system, etc.

The P51 that crashed in Reno, killing a number of people a few years ago, did so because of one small nut that was reused on the trim tab on the elevator of that airplane. One single nut vibrated free; it wasn't supposed to be used, but they reused a nylock self locking nut in a place they shouldn't. It came off. The elevator trim tab fluttered and drove the elevator full deflection, putting the aircraft into a hard 9G+ pull that entered a positive loop and ended up crashing into the grandstands that were full of spectators. One single misapplied nut. 9 dead. 54 injured. Follow the directions; they're in place for a reason.

quote:

Originally posted by sns3guppy:
It's untrue that a properly torqued bolt will not come loose. That's why many properly torqued bolts on aircraft are secured with safety wire...because they can come loose.

Fair enough, I shouldn't have stated it as an absolute. Of course anything can happen.

What I was really getting at is that I don't think there's much point in using Loctite or lock washers when you can properly torque a fastener. To give an example that most people see every day, the lug nuts or lug bolts that secure the wheels to your car are not used with threadlocker or locking washers.

In cases like you describe, where someone is going to die if a fastener comes loose, additional measures may be warranted.

I do absolutely agree with you that, without a really compelling reason to do something different, I would just follow the manufacturer's instructions.

Generally agree with following mfgr instructions except for all the crap that's made in China has me second guessing many things and actively wondering about ways I could harden something.

Not everything - somethings come loose or fails, just tighten or fix. NBD. But rack accessories, trailers, etc where someone might die, call me a little paranoid.

Something designed, spec'ed and made in USA may be okay. I'm not entirely comfortable with Chinese crap even if designed in USA. In my experience, things fail more often.

I just don't know when and how to harden failure points.

So, the info above is good -- I'll use nylock nuts as-is. I'll review the assembly again; there may still be a few places without nylock nuts where I still may want to use either a lock washer or loctite.

I also need to look into lift kits and wheels for this. I need to figure out what approach/breakover/departure this thing can handle with 14' kayaks hanging off the rear. I need this to work on lakeside trails and not just boat launches.

Kind of related to the topic, possibly NSFW due to language.
https://m.youtube.com/watch?v=WbLS3rGtKDM

Guys, don’t over think this.
It’s a boat trailer, not a spacecraft.

quote:

Originally posted by 220-9er:
Guys, don’t over think this.
It’s a boat trailer, not a spacecraft.

couldn't agree more put it together with an impact wrench and forget about it, I would have would have it done in an hour.

quote:

Originally posted by kx90:

quote:

Originally posted by konata88:
Are the nylock (is that the self locking nut that comes w/ this trailer kit?) secure and heat tolerant? If this is sitting in the sun and also being submerged in water, will these nylock nuts last? Or should I use a little loctite here as well?

Just don't want the trailer to disintegrate on me while I'm rolling down the highway someday...

Nylock nuts are used on boat trailers without lock washers or Loc-tite (think large capacity like 18k lbs) among many other types of assemblies.

This. You’re over thinking this. Just follow the manufacturers directions.

As for locknuts and properly torqued bolts. Properly torqued bolts are for stretch of the bolt, they still can loosen if there is a lot of vibration present (mostly rotational vibration). Thus the use of lock nuts and lock washers on various things. You shouldn’t use both together.