A frame fastener problem was revealed by moving trim.

[mlpeloquin]

We took a pounding crossing country, national rally, big lakes, east cost, Florida, Nashville, and finally back home to San Jose, California. The rig was weighed in Goshen and was within the designed weight. In fact the left/right and front rear tires were within 100 pounds of each other. We decided to add a washer/dryer and a new kingpin to the fifth wheel. While doing the washer/dryer prep, I broke my leg and had to cancel out on the Southern California rally in Temecula. This turned out to be a good thing. With six weeks of healing time, I ordered the new King Pin. I decided on the Flexair Trail Air over the Mor Ryde. After installing the King Pin, I hitched up. With the weight of the Fifth Wheel on the hitch, I started inspecting and noticed the side trim moved.


I did not notice the movement before, but it must have been there. Just did not notice since it moved back when the weight was off the King Pin. It moved back so perfectly, that the pointing looked good. I took the Big Horn to my local RV repair shop, RV Restore and Repair, whom I really trust. Tim contacted Heartland and sent pictures. Heartland contacted Lippart. Both wanted to see more, but did not want to authorize any labor. I authorize the removal of the trim and front skin in order to expose the frames. Turns out the fasteners had sheared off holding the sub-frame to the main Lippart frame on the driver’s side.


After pictures going back and forth, Lippart rightfully stated there wasn’t anything wrong with the frames. Heartland was not sure about paying since my Fifth Wheel is well out of warranty. I paid for the repair and went on our planed trip. Tim used larger, longer fasteners, and doubled up on them. We received a call from RV Restore and Repair while driving. Heartland offered a good will payment, which covered almost half the cost. I was a bit surprised and very happy with Heartland.

Lesson learned: Be sure to check your trim when putting the weight on the hitch. This can expose serious hidden problems.

Just got to let you know that the Big Horn has a very smooth ride with the new King Pin. What a difference. The road shock is all but gone and the bucking is suppressed. The road shock isn't being transferred to the fasteners anymore through the King Pin. Driving with the Fifth Wheel is now a pleasure. If your thinking about changing King Pins I really recommend the Trailair Flex Air.

 

[Bones]

Did you have frame damage? I can't believe you frame is flexing that much to shear off the front section of bolts.

 

[rxbristol]

Thanks for the post. I have installed the Flex Air, but have not put it to use yet...another of couple of weeks and it gets its maiden voyage.

 

[mlpeloquin]

Did you have frame damage? I can't believe you frame is flexing that much to shear off the front section of bolts.

There are two frames. The main Lippart frame which runs from the back to the King Pin, and a sub-frame which is fastened to the Lippart frame. Note that I have been told that Lippart now has purchased the sub-frame manufacture. True or not I don't know. It is on this sub-frame to main frame that the fasteners sheared off on the drivers side. It supports the front bedroom and closet in our unit including the slide. Our repair shop fully inspected the frames and they were not bent or damaged. Ordinarily in mechanical design, fasteners, bolts, etc. should not be used in shear. They should be in tension only. When shear is present in a design, it is better to use a shear pin to carry the shear or a hardened sleeve. That being said, fasteners and bolts are used in shear at times. As long as the fasteners are in tension they can hold. Note it is when they are over or under torqued that tension is removed and will be subject to stress cracking. Proper torque stretches the fastener, but not beyond the spring back point. The fastener holds because this spring tension holds the bolt and nut tight. The two frames are of two different metals. Steal and aluminum. So a possible problem maybe the difference in CTE, coefficient of thermal expansion, and the ductility of the aluminum. Through temperature changes the aluminum maybe slowly thinning under the tension of the fastener and thus reliving the tension of the fastener. The road shock from the king pin is transferred to the frames and thus the fasteners. With the tension removed the frame can move slightly and shear the fastener. Just conjecture on my part. It could be that they were under or over torqued or the fastener lot was not to proper specifications. Anyway, the new Flexair Trail Air king pin has the front floating and damping out all hard high frequency shock so I don't think it will occur again.

 

[Bones]

There are two frames. The main Lippart frame which runs from the back to the King Pin, and a sub-frame which is fastened to the Lippart frame. Note that I have been told that Lippart now has purchased the sub-frame manufacture. True or not I don't know. It is on this sub-frame to main frame that the fasteners sheared off on the drivers side. It supports the front bedroom and closet in our unit including the slide. Our repair shop fully inspected the frames and they were not bent or damaged. Ordinarily in mechanical design, fasteners, bolts, etc. should not be used in shear. They should be in tension only. When shear is present in a design, it is better to use a shear pin to carry the shear or a hardened sleeve. That being said, fasteners and bolts are used in shear at times. As long as the fasteners are in tension they can hold. Note it is when they are over or under torqued that tension is removed and will be subject to stress cracking. Proper torque stretches the fastener, but not beyond the spring back point. The fastener holds because this spring tension holds the bolt and nut tight. The two frames are of two different metals. Steal and aluminum. So a possible problem maybe the difference in CTE, coefficient of thermal expansion, and the ductility of the aluminum. Through temperature changes the aluminum maybe slowly thinning under the tension of the fastener and thus reliving the tension of the fastener. The road shock from the king pin is transferred to the frames and thus the fasteners. With the tension removed the frame can move slightly and shear the fastener. Just conjecture on my part. It could be that they were under or over torqued or the fastener lot was not to proper specifications. Anyway, the new Flexair Trail Air king pin has the front floating and damping out all hard high frequency shock so I don't think it will occur again.

Well..........All I am suggesting is that something may have been missed. If your sub frame section breaks the bolts wither in shear or tension really doesn't matter. they broke because they are seeing forces they should not see when you hook up to your truck. Something is flexing more than it should and putting bigger bolts on may not actually fix your problem and only mask it to show up at a later time.

 

[avvidclif]

My understanding is the sub-frame is there to support the floor, ergo aluminum, not be a part of the main frame. It seems to me the main frame is flexing enough to move the sub and shearing bolts. The main frame shouldn't flex that much. My 2 cents and from a non-engineers standpoint.

 

[Bob&Patty]

Marc, glad it was repaired and HL helped with the bill. BTW, the Temecula Rally is on again in October.

 

[mlpeloquin]

Marc, glad it was repaired and HL helped with the bill. BTW, the Temecula Rally is on again in October.

Well I did the broken leg thing, we are now getting over a bad flu, so I hope to be there. Anyone who has not attended Bob's rally in Temecula is missing a great rally. Thanks Bob!

 

[mlpeloquin]

Well..........All I am suggesting is that something may have been missed. If your sub frame section breaks the bolts wither in shear or tension really doesn't matter. they broke because they are seeing forces they should not see when you hook up to your truck. Something is flexing more than it should and putting bigger bolts on may not actually fix your problem and only mask it to show up at a later time.

The fastener failure started in the driver side bottom front. Improper fastener torque, contaminates in the fastener metal causing embrittelment, will cause fastener failure under the proper load that they were designed for. Once one fastener fails the remaining fasteners must carry more of the load. If the load is greater than the remaining fasteners can hold, the failures continue until all the fasteners fail. This is what I believe occurred. Since my frames were fully inspected and were not bent or twisted or the welds cracked, I don't think it is do to main frame flex. The load on the sub-frame is less stiff on the slide side, (drivers side) and is subject to shock and vibe more than the passenger side. A weakness in the fasteners do to embrittlement or improper torque etc. will show up here first. It does not take main frame flex to cause the fasteners to fail.
​

 

[TomSt]

My 2011 Greystone has exactly the same problem as in the picture. Was 'fixed' by the dealer under warranty. Went to Goshen Rally where it was "fixed" again by factory techs. they told us there is a 2x2 in the aluminum tube that is screwed to the assembly and that it splits from too many screws in it. Also when they replaced the screws said they were only one inch and should have been two inch. that being said the problem has returned for the third time

 

[mlpeloquin]

My 2011 Greystone has exactly the same problem as in the picture. Was 'fixed' by the dealer under warranty. Went to Goshen Rally where it was "fixed" again by factory techs. they told us there is a 2x2 in the aluminum tube that is screwed to the assembly and that it splits from too many screws in it. Also when they replaced the screws said they were only one inch and should have been two inch. that being said the problem has returned for the third time

My repair shop used larger longer diameter screws and doubled up on them. I replaced the standard kingpin with a new Trailair Flex Air king pin. The fifth wheel floats with most road shock and vibration not getting to the front end any more. The ride in the truck is like night and day. I was informed that there are two sets of 2X2 aluminum tubes that run down the front of my Boghorn. The new fasteners go through both. If your tube(s) are split, they need to be replace or welded back together. I would then change the King Pin to dampen and reduce the road shock and vibration. It will also reduce driver fatigue. Driving has now become a pleasure with the fifth wheel. The cost of the repair for my rig was just under 1K. But that was with time taken to take pictures, put it in storage, take it back out of storage, take more pictures. Each time the front skin had to be removed and put back. So at lest two hours of labor was messing around to have Heartland and Lippart look at the problem and come up with a proper solution. The tubes can be cut out and new ones welded in short order and the fastener and skin put back. Make sure that the main Lippart frame is inspected well to make sure all the welds are not cracked and it is not bent. Once the front skin is removed, it is easy to inspect.

I ordered my king pin from http://tweetys.com/search.aspx?find=flex+air. $1180.52 and free shipping. I used a cherry picker and 6X6 on the back of my truck to set the king pin on. Then I back it up to the fifth wheel. I lowered the fifth wheel and adjusted the position of the kin pin to align the mounting holes. I used a bar to help align the other mounting holes. I made spacers/shims from aluminum stock purchased from the hardware store to fill in 1/8" and purchased longer bolts as required. I did not want the stress applied to the welds by the bolts pulling the mount in. If you look up "How to install a Trailair kin pin" on Utube, you will notice the mount being drawn in and under stress. The welds will hold, but if you were to be rear ended, they might snap do to the tension they would be under. Make sure the bolts are the same hardness as the original. Torque them as well. You can purchase or rent a torque wrench with the proper socket.