MUpde

Trailer Tongue Bolt Sheared

44 posts in this topic

Why not put another pin in instead of the bolt? 

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6 hours ago, jwl019 said:

20161031_130128.jpg

20161031_130150.jpg

looks like there is up and down movement available between the 2 pieces.

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25 minutes ago, jrvs23 said:

Why not put another pin in instead of the bolt? 

I've thought about going that route, also thought about how easy it would be for someone to pull both pins as a prank/steal while parked at a ramp too. Not that a bolt is that much more of a deterrent but at least would require a wrench or two.

2 minutes ago, oldjeep said:

looks like there is up and down movement available between the 2 pieces.

It very well may be.  The side the pin is on is actually the side the bolt was in and there are some kind of washers between the joining ears you see so it eliminates some of the movement this side the pin is normally on that doesn't have washers.  Maybe the normal pulling stress front to back and any left to right twisting due to the extra space on the one side did it. I haven't had washers on this side since I owned the boat, but maybe there should be some?

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Few comments from down under & my experience with a  Boatmate trailer.

the hinge plates are 1/4" or maybe 3/8" at best thick.

having both the locking point & hinge point at the same position I found the holes in these plates were being flogged out.

when you uncouple the trailer see how much up & down movement you have from the wear in these holes.

what causes a bolt to shear is movement. If the holes are snug to the bolt, there is no movement allowing the bolt to shear.

Now, look at current Boatmate trailers & these hinge points are now staggered, one behind the other by about 4".

my initial soloution to reduce the flogging if these hinge holes was to use a price of 5/8" threaded rod, make up some brackets to tie together the bottom hinge point.

worked a treat & when I rebuilt the trailer also rebuilt the coupling hinge to offset the hinge points.

the last few pics in this post show the hinge points of the rebuild

 

Edited by Andrew63

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Definitely interested in the pics posted by jwl because i also have the swing hitch tongue on extreme trailer. Looking at the bolt closely, it shows cad plating was not present in the thread area leading to heavy rust corrosion. Was it exposed to road salt or sea water?

Basically the bolts here were made wrong as cad should have been all over including threads. Also, the crack striations show bending fatigue propagation to failure. Highly likely hydrogen embittlement caused from salt and or wrong temper led to initial cracking.

Solution is as others stated, use longer bolt, and make sure cad plating is all over including threads. Imho anyway, glad u caught it early!

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11 hours ago, mcgreg said:

Looking at the bolt closely, it shows cad plating was not present in the thread area leading to heavy rust corrosion. Was it exposed to road salt or sea water?

Basically the bolts here were made wrong as cad should have been all over including threads. Also, the crack striations show bending fatigue propagation to failure. Highly likely hydrogen embittlement caused from salt and or wrong temper led to initial cracking.

Solution is as others stated, use longer bolt, and make sure cad plating is all over including threads. Imho anyway, glad u caught it early!

I actually picked up a new bolt yesterday.  It does have the plating all over it.  This boat has never seen salt or brackish water or road salt since it has been in TX and LA all it's life, so possibly wrong temper?

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Further to above comments, measured the dimensions on my extreme trailer found both the dimensions of the joint height and design are different than the pictures posted by jwl. It does however use one 5/8" grade 8 bolt and one plain long dowel pin. One mine, the top and bottom plate tightly nest with the tongue bridle so there is no vertical slop. Further, the bolt and pin fit tightly inside of a solid tube which forms the tongue bridle. Would post a pic here but web police wont let me I guess.

Did a joint analysis and was surprised to find out that joint is "heavily loaded". The hot spot is definitely in that thread minor diameter. Based on that, for my own self, will be switching to two longer grade 8 bolts to get the minor diameter outside the plates (and deep six the dowel pin). Will apply a snugging torque to the bolts to tightly clamp the plates to the tongue bridal. Not as convenient as having a loose pivot, but no sense in taking a risk.  Good luck!

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On 30/12/2016 at 1:25 PM, mcgreg said:

Further to above comments, measured the dimensions on my extreme trailer found both the dimensions of the joint height and design are different than the pictures posted by jwl. It does however use one 5/8" grade 8 bolt and one plain long dowel pin. One mine, the top and bottom plate tightly nest with the tongue bridle so there is no vertical slop. Further, the bolt and pin fit tightly inside of a solid tube which forms the tongue bridle. Would post a pic here but web police wont let me I guess.

Did a joint analysis and was surprised to find out that joint is "heavily loaded". The hot spot is definitely in that thread minor diameter. Based on that, for my own self, will be switching to two longer grade 8 bolts to get the minor diameter outside the plates (and deep six the dowel pin). Will apply a snugging torque to the bolts to tightly clamp the plates to the tongue bridal. Not as convenient as having a loose pivot, but no sense in taking a risk.  Good luck!

Since the load is at the bottom, the minor thread diameter, may not look as nice, put the bolts in from the bottom so you have the major diameter at the point people find the bolt shears

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33 minutes ago, Andrew63 said:

Since the load is at the bottom, the minor thread diameter, may not look as nice, put the bolts in from the bottom so you have the major diameter at the point people find the bolt shears

The bolt is under the same shear load at the top, just in the opposite direction.

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On 10/01/2017 at 6:39 AM, MadMan said:

The bolt is under the same shear load at the top, just in the opposite direction.

Agreed, but, when the holes get elongated this happens at the bottom not the top.

having a minor thread diameter with movement will allow the bottom to move more & once you allow movement the shearing action commences.

should you have the head at the bottom with the full shank diameter, this is stronger than the thread against shearing.

in the aviation industry bolt holes are reamed to close tolerances to prevent any movement as this is a much stronger connection.

once you set up a connection which is under shear load on the fixings with any movement in the holes, you are allowing the shearing action to take place which will have the weaker connection

just my humble opinion

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The bolt is too short, the threads should not be touching the hinge point.  Get a bolt where the shoulder properly terminates below the hinge and then put a couple washers on if needed to take up the slack to the nut.

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3 hours ago, Andrew63 said:

Agreed, but, when the holes get elongated this happens at the bottom not the top.

having a minor thread diameter with movement will allow the bottom to move more & once you allow movement the shearing action commences.

should you have the head at the bottom with the full shank diameter, this is stronger than the thread against shearing.

in the aviation industry bolt holes are reamed to close tolerances to prevent any movement as this is a much stronger connection.

once you set up a connection which is under shear load on the fixings with any movement in the holes, you are allowing the shearing action to take place which will have the weaker connection

just my humble opinion

So, you're saying invert the bolt to elongate the top hole also?

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I am not screwing with mine as the holes are elongated to a next larger OD diameter bolt size. I am going to enlarge both holes accordingly and install the next size larger bolt or pin. Either way bolt or pin both will be captured pieces and pivot just the same. Bottom line is because of the grade of steel used in the trailer we will be fighting this until we get rid of them.

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I find it odd that the bolt is rusted all the way through, indicating it's been sheared off and exposed for  while.??

Agree that the shoulder needs to be longer,   And if there is excess vertical play in the tongue I'd recommend a spacer , 

20161031_130231.jpg

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One more thought about putting the bolt in from the bottom, if the bolt breaks again or the nut just comes off, the bolt is probably going to fall out completely.

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On 15/01/2017 at 1:43 PM, MadMan said:

One more thought about putting the bolt in from the bottom, if the bolt breaks again or the nut just comes off, the bolt is probably going to fall out completely.

Good point. as far as the top elongating, the top usually has the support of the faces of the hinge making contact thus not allowing the top to elongate past this point of contact as it is supported. The bottom will want to open up & elongate the holes.

Maybe just use a longer bolt from the top so the thread starts just as the bolt clears the bottom plate, use a washer or two & cut off the excess thread past 2 threads protruding past the lock nut.

May be better welding another plate top & bottom to increase the thickness of the material at these hinge points to distribute the load more at this point.

Pitty there is no offset hinge/lock bolt conversion kit available which is why I made my own. May have gone over the top using 5/8" thick plate top and bottom for the hinge points with a 2" solid square bar drilled to accept a 5/8" gr8.8 hinge bolt for the hinge point between these plates. Ensured there was no thread in contact with the hinge points, only the bolt shank.

I noticed the AU made Easytow trailers have the same in align hinge points of past boat mate trailers only the top & bottom plates are 1/2" thick.

my original Boatmate hinge plates were only 5/16" which is why I believe these are elongating.

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On 12/28/2016 at 8:40 AM, jwl019 said:

I actually picked up a new bolt yesterday.  It does have the plating all over it.  This boat has never seen salt or brackish water or road salt since it has been in TX and LA all it's life, so possibly wrong temper?

Where did you get the new bolt, and what bolt did you get?

Did the new bolt cure any vertical slop?

I have some vertical slop and a rusty looking bolt and looking to fix this.

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2 minutes ago, Bozboat said:

Where did you get the new bolt, and what bolt did you get?

Did the new bolt cure any vertical slop?

I have some vertical slop and a rusty looking bolt and looking to fix this.

I picked up the bolt from a local shop that carries bolts for construction.  The bolt was just long enough that the threads made it below the lower ears and with a washer underneath, the bolt worked great.  iirc, I got a 5/8" by 7" long, grade 8.  I took my tape measure and made sure the threads would clear the ears before I bought it.  For the vertical slop, I used a large rubber washer that I found at Lowe's to slide between the ears on top and one on bottom.

 

If my local place did not have one, I was going to order one from Magnum Trailers, they had quoted me $7-8 plus shipping.  I had looked at Lowe's/Home Depot/typical hardware stores and no one had a bolt long enough in the grade 8.  I did find a regular stainless bolt at the local hardware store that would work so I bought it as well just incase I needed it (like Pete, now I have a backup for my backup).

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Fastenal would be the place to check too

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