Ball Loosened, Use Loctite?

[32vld]

From time to time my son or I have to tow bar
his 1946 Chevrolet 2 ton rack truck. He uses it
for his food catering business.

Being it is old it breaks down once a year. So
when booked to do a party he has to get his truck
there so it is towed with a Chevy Suburban.

Well the truck just had to have the head R&R so the
truck had to be towed a few times. This time I bought
a new draw bar and 2" ball to get the tow bar level
when towing his old truck.

The problem is that the ball came loose after a few
tows. Last year we had to tow his truck for many weeks
because his engine was at the machine shop getting
rebuilt and we never had any problems using another
draw bar and ball.

I did not have a 1.5 wrench so I went to my neighbors
house, retired mechanic. He tightened down the nut
with a long combination wrench. Then doubled up the
wrench and gave it another tug.

Any ideas why it loosened?

He used anti seize grease when tightening the ball
to the draw bar. He said incase you ever have to take
it apart. I never did that before.

Could that of caused the ball to loosen?

Is it a good idea to clean off all the threads and
apply Loctite?

Thanks for your help.

Here is a link to my son's website so you can see his
truck:

http://www.pizzarita.org/

[Durb]

Many people torque the hitch ball by placing the ball mount into the truck receiver and applying downward force. When they do this the rear of the truck will squat. The energy used to squat the truck will be deducted from the the torque wrench's output thereby applying less torque to the hitch ball. This number is significant. Good technique is to place a jack under the receiver so the truck doesn't squat and the full 250 ft-lb from the torque wrench is used to tighten the nut. Dittos on a new lock washer.

[3oaks]

32vld wrote:
Of course a lock washer was used.
I guess I will get some Loctite.
Thanks

But was the nut torqued to the proper specifications? Just doubling up on the wrench doesn't get it done properly as proven by the ball coming loose after a couple of tows.

[nevadanick]

Grease the ball, the towbar is a friction wrench and with no friction it wont loosen the ball.

[JBarca]

I'll add a few things to help the cause. The ball loosening up in a few tows, points to a large problem.

From the posts, you are using a lock washer. This is good and for sure needed. If it is not a new one, consider getting a new one. The edge sharpness and strength is better on a new one. But also make sure the grade of steel of the lock washer is correct. If you do not know what grade to get, get a grade 8 lock washer.

Next is the tow ball. There is a "dry" threads torque spec for that ball as required by standards. And the torque spec changes pending the rating of the tow ball as the grade or temper of the steel changes with the rating. One torque number does not always fit all. Stamped on top of the ball is the pull rating which must be equal to or greater then the weight you are towing. Make sure the rating is correct.

There should be a manufacture on the ball top as well and then measure the thread shank size. Armed with that info, the manufactures web site will most likely have the correct torque based on "dry" threads. Or call them.

Using a lube on the threads requires the torque be adjusted down from the dry threads spec. Yes, using lube requires less torque to have the same bolt thread preload (tension). How much depends on the lube. Sometimes it may be a 15% to 25% reduction. If you use it dry, most are waxed from the manufacture and the spec they give covers this. If the tow ball is a low grade of steel, and you lube the threads and you did not adjust down the torque, you can by accident over torque the threads into the yield zone and that will allow the threads to stretch and come loose.

To create the correct amount of tightness, a torque wrench is the easiest. There is a torque to position method but this needs to be derived from a set of tests. For a towing application, I can't recommend using a large wrench with a 4 foot pipe as this may be way too much for a low strength ball (stretching the threads) or not enough for a high strength ball. (not enough preload (tension) to set the threads in the proper tension range for anti fatigue and loosening)

There is another thing not mentioned. Grease the tow ball when in use. You can use any type of wheel bearing grease if that's what you have or a white grease made for tow ball applications. This helps save the ball coupler on the trailer and scoring of the tow ball. If the tow ball and coupler are very dry, that high friction can aggravate loosening a tow ball. It does not happen all the time, but it does happen. Put a baggie on the greased ball when not in use. If not, that grease seems to have a magnetic attraction to ones pant legs.... At least mine anyway.

If you select the blue loctite, (removable) this may not fix the underlying issue. Something is not right, but what? Adding blue loctite on this fine thread step up may make the situation worse trying to ever get the nut off. It adds friction which is what it is supposed to do but after towing with it, that friction will be real high come the day several years from now trying to get it off. It may gall worse getting it off with removable loctite then just plain dry threads.

Also, is the hole in the draw bar or hitch head have a lot a play in it? Meaning someone put a 3/4" ball shank in a 1" hole? This is an issue, an adapter sleeve is suppose to be used in this case to take up the play.

Most times, a fastener loosening up like a tow ball comes from the fastener not being strong enough, (too light a tow ball for the load allowing thread stretch), lack of the proper clearance hole size, (missing an adapter sleeve create a sloppy fit), lock washer not correct for the application (maybe a weak one used) and the nut was not tighten correctly for the application. (too much or not enough torque)

Hope this helps

John

[BenK]

This is a safety issue and must comment

There is a torque specification for that ball (all with a DOT approval). Either stamped on it somewhere or label or tag when still in the box. Most never read it and/or toss the tag

Anyone with the "Farmer Tight" methodology would never be hired and if they were, would fired in an instant working on a quality organization.

Like these industries: military, airplane, automotive, people movers and a big ETC

The term "Farmer Tight" has offended a few here, but it is an accepted/common industry term. My college strength of materials and other engineering professors always used that term.



smoothstar: There's Tight. Then There's Farmer Tight.

Many of us will either break or fix stuff today. Sometimes, both at once. Many of you may be familiar with the term, "Farmer Tight". If not. It comes to us from the world of the mechanic.There are two varities.

1.Tighten it up ( a nut or bolt) until it breaks ,then back it off a half a turn.

2.Tightnen it as tight as you can with all your strength , then give it another half a turn.

Number two is sometimes called the "Template Method". Also effective. Both are related to "Whaling on it". One applies the weight of a whale to a certain endevour.( These can be applied in all walks of life )

Here's my point. Never allow a lack of experience or expertise to keep you from attempting anything. We all gotta die someday.Who wouldn't rather go in a fiery explosion? But there's no big hairy hurry either. Use your good judgement. Live and learn.

There is science to fastener's and the design/engineering of it all.

From choosing a size, how many, centers, grade and the torque for 'that' application. There is a range of torque for every application and fastener.

The calculations is based on the bolt/nut (threaded part) expected performance at max spec conditions. Max pull apart. Max shear. Max vibration (frequency and amplitude), which includes secondary and tertiary harmonics...plus some safety factor. Plus some safety factor based on warranty period (expected life span of the product)

The formula is:

T = K Fi d (This is for English fasteners...If metric, same formula, but with metric values)

where:
T = Torque required to create a desired bolt pre-load (in-lb)

K = Nut "K Factor" (dimensionless)...a constant or friction at the mating surfaces. The higher this number...the more rough/rusty the junction...the lower this number...the smoother/greased/oiled/etc

Fi = Bolt Pre-Load Force (lbf)...AKA clamping force holding the parts together. This is the engineering calculation of what clamping force is needed to hold it together while used at max specification(s)

d = Bolt Nominal Diameter (in).


Affordable 3/4" Torque Wrench...'Farmer Tighting" mentioned

Jerrybo66 wrote:


This is one topic I cannot understand. Torquing hitch components. Big time torque wrenches especially un-accurate Chinese made ones. Torque specs need to be adhered to with head bolts, manifold bolts, bearings, etc. but hitches, I don't believe it. I've been "farmer tightening" anything between the truck and trailer for over 50 years and haven't lost anything yet. There are enough specifications out there to drive an engineer crazy but in reality don't mean much to a person with half ounce of common sense. At this time I am working on the motor of my 1973 Ford PU with my Made in USA Craftsman torque wrench but my hitches are farmer tight with my Made in USA 3/4 drive ratchet. FWIW, I installed the Equalizer when I bought the trailer in '03 and haven't had to adjust any bolts. The trailer still follows wherever I go..... 🙂 .... IMO.

{edit}....there is a case where, even if tightened to the proper torque...the fastener/threaded part will NOT hold, but loosen

It is when the torque is over the tensile strength rating of either or both the bolt and threaded part. Meaning the fastener material has gone past the plastic range (where most all fasterns are calculated to be below) and into the yield range (yes, know of the ARP head studs and their torque to yield and am NOT a fan of that). Plastic range springs back and yield range does NOT...but stays stretched

And there is another component to this formula, but left it off to keep it simple...it is the grade of the bolt & threaded parts and it is tensile strength number. Like a grade 8 bolt's tensile strength is in the +140,000 PSI range...IIRC

[Tinyandthegang]

Nut was not tightened properly. When I tighten mine I use a large monkey wrench with a 4' pipe over the end and give it a good tug. In over 50 years I have never had a ball loosen.

[time2roll]

Pulled it tight by hand? Probably need to turn the shank 1/4 to stand on the wrench to achieve the the required torque. Spec is something like 250 to 450.

[ScottG]

Lock washer may be worn out. I would get a new one.
Most locktite wont do a lot for such a large nut - you have to ge the correct product. It isn't needed though. If he has the proper LW it will take a huge effort to get loose.

[32vld]

Of course a lock washer was used.
I guess I will get some Loctite.
Thanks

[N-Trouble]

downtheroad wrote:
Lock washer...

X2

[Hank85713]

I used some on my receiver hitch as I had the same problem and could not get a wrench on the nut. Had to buy a monkey wrench and jam the nut with a big screwdriver. Anyhow that was about 10 years ago and no problems since. Just get 242 (blue) not the green stuff which is basically permanent. 222 is for light weight stuff.

Yes clean all the grease off the thereads

[downtheroad]

Lock washer...