ANOTHER broken tongue bolt!

[resqu-u]

Take a pick of your Truck/Trailer just like you would be heading to the ramp. Could it be the angle the trailer tongue sits at while towing? It doesn't take much angle to make a huge difference in a shear load. I'd be all over boatmate on this one, shouldn't be breaking the stainless pins or Fastnal G8's. Keep us posted.

 

[RedAllison]

For over 20 years I've towed everything essentially "level" or if any some trailers tow best with the tongue appx 1" above "level". I have a couple of hitches from level, to drop/raised and since last summer I primarily tow my XB21 with a 2007 Expedition EL (with autolevel rear suspension).

A G-8 bolt is much stronger than any regular SS hitch pins or usual G-5 trailer equipment. My trailer has torsion axles as well and I literally can feel and SEE the difference in ride compared to spring axles trailers. There is essentially no shock in the system. I cross the same old railroad Xings with my XB21 that I did for years with my XB03 and the torsions just float across with the boat not moving, when they would nearly send the old XB03 flying, trailer and all. There's no "rebound" with the torsions so I seriously doubt the torsions are rougher or transmit more shock on the trailer frame itself than a stack of springs. Plus the much larger boat and motor is considerably heavier than my previous boat so there would be that much more load to "jump around, bounce and shock" if the system were rougher.

Just haven't taken the time to have it welded up yet,
RA

 

[GotMyAlly]

Grade 8 bolts are measured in tensile strength I believe......how far they can stretch when tightened down before they break. The hitch pins are rated in shear strength. I don't think you can compare the two.

I'd go with hitch pins. Yes, the tensile strength rating is more on a G8 bolt. BUT...you're tightening down that bolt. It has forces on it in multiple direction. You're stretching the bolt and side-loading it. Shear and tension forces simultaneously. Plus, the clamping tension gives the side-loading forces more leverage. The hitch pin just floats in the tongue so it only gets loaded with one force.

For the bolt to overcome the 2-force problem, you'd have to crank it down tight enough to squeeze the two parts of the tongue together to create enough friction to overcome the forces the truck is putting on it when starting/stopping. That would remove the side-load. But I don't think you can possibly crank that bolt tight enough to do that.

A grade 8 that is too long, so that the non-threaded part is longer than the alignment holes in the tongue, may be the way to go if you're dead set on a bolt. That way it doesn't put any clamping forces on the tongue or stretch the bolt. In that case, it's basically just a G8 pin.

 

[IRONBLOCK]

RA, I'd be willing to bet that your bolts both failed as a result of fatigue; a microscopic crack that starts at a notch- like where the threads were cut or rolled and propagates across the surface of the bolt and not shear. Higher strength connections are much more likely to fail in fatigue (check your previous post on this subject) than low strength fasteners. If you are really worried about someone stealing a pin you could probably drill a hole through it and put a small lock on it...

Keep in mind, if you modify your trailer you assume a lot of responsibility that the trailer manufacturer would be responsible for now; same assumption of responsibility with Grade 8 bolts and pins unless supplied by Boat Mate...

Please make sure that Allison and Boat Mate know of this problem in writing and have them engineer a solution. Certainly you are not alone with this situation.

 

[RedAllison]

The bolts aren't tightened very much, just snugged up and have nylock nuts on them. "As designed" the starboard side bolt can't be tightened up very much because it's supposed to act as a hinge as well when the tongue is folded. I replaced the removable pin on the port side with another G8 bolt/nut but both are just tightened "snug" instead of with a gut busting, bolt stretching amount of force.

I just keep an eye on it everytime I stop. If it breaks another bolt then I'll have to do something, otherwise I might just run it "as is" and keep extra bolts with me until I get an aluminum trailer!!!

:help
RA