Foretravel Owners' Forum

Even though I torque tested all Rolok bolts on the rear bulkhead according to a Foretravel bulletin, and even though I was visually inspecting the rear bulkhead on a regular basis, the last inspection on 2014 August 25th revealed that twelve of the seventeen rear bulkhead Rolok bolts had failed. There was a one inch gap between the angle iron and the body at the driver side rear suspension mount and a half inch gap at the passenger side rear suspension mount. The angle iron had been morphed from straight into a serpentine track.  The rear bulkhead joint was about to fail completely. I spent the next four days replacing all 5/16 Rolok bolts with 3/8 Grade five bolts with nuts (and washers). I followed Brett Wolfe's procedure but did drill the 1 3/8 access holes closer to the 1.5 inch square tubing then Brett suggested. I was able, with considerable effort/time, to remove all rusted Rolok bolts and did not drill any new holes.

I will soon be doing the same replacements on the front bulkhead because I no longer trust the ability of the 5/16 Rolok bolts to hold for many years in such an unfriendly and dynamic environment.

Ramblings of a mechanical mind.
Here are some thoughts from a Professional Mechanical Engineer. Some folks have indicated that they believe using a Grade 8 bolt in the bulkhead is better than using a Grade 5 bolt. I do not agree with this, even though a Grade 8 bolt is clearly stronger than a Grade 5 bolt. I believe 3/8 inch Grade 5 bolts are the best choice for replacing the 5/16 inch Rolok bolts because: a 3/8 Grade 5 bolt is stronger and provides more clamping force than the 5/16 Rolok; a Grade 5 bolt will permanently deform at 135% of working tension while a Grade 8 bolt will permanently deform at 115% of working tension, so a Grade 5 bolt will better tolerate jerk loads, a Grade 8 bolt will suffer hydrogen embrittlement (leading to a brittle break) much faster than a Grade 5 bolt; applying higher (grade 8) clamping forces to the 1.5 inch square tubing may cause the tube to permanently deform (see testing below).

Here is some testing that I did!
I did some testing with a piece of 1.5 inch square tubing in a vise using a 3/8inch Grade 8 bolt with a flared nut, a 3/8 washer, a thick 1/2 inch washer (1.375 OD). I drilled a 3/8 inch hole through the square tube, then lubricated the threads and tightened the bolt to 23 ftlb, 25 ftlb, 30 ftlb and finally 35 foot pounds. After each torque value, I disassembled and examined the square tubing for damage. There was no evidence of permanent deformation at 23 ftlb (3/8 grade 5), or at 25 ftlb, however, at 30 ftlb the sides of the tube were permanently concaved by 2/1000 inch, and at 35 ftlb (3/8 grade 8) concaved by 7/1000 inch.
 
I removed the aluminum sheet which was badly corroded due to galvanic corrosion. After removing the Rolok bolts, I drilled the 5/16 holes out to 3/8 inch and installed 3/8-16 all thread bolts which were 3 inches long. I tried 2.5 inch bolts but there was only one thread sticking out of the nut. I lubricated the threads and tightened to 250 inch pounds, even though the recommended torque for lubricated 3/8 course thread Grade 5 bolts is 276 inch pounds (23 ftlb).

Note that the recommended torque for a 5/16 Rolok bolt is 21 ftlb dry, while dry torque for a 3/8 grade 5 bolt is 30 ftlb.

Rust jacking was not the cause of the failure of my rear bulkhead. There was little more than surface rust on the angle iron and the square tubing. Two of the Rolok bolts were missing and I presume had fallen out on the road. The heads were broken off other bolts such that five bolts were holding the bulkhead together, three on the passenger side which  had previously installed, one in the center and one on the outer driver side. I managed to remove two Rolok bolts without damaging them. I attempted to torque them to 250 inlb but they both just kept turning. The diameter of the Rolok was smaller at the inside wall of the square tubing, perhaps rust had damaged the threads which were no longer capable of tolerating 250 inlb.

Removing the rusted, broken Rolok bolts involved drilling a 9/64 hole in the broken end of the bolts and inserting a broken bolt remover tool. I drilled out the hole in the angle iron with a 3/8 bit and kept drilling until the end of the broken bolt had a center mark. I then drilled into the bolt a quarter inch with a hard bit (expensive). I threaded a 6mm nut onto the inside end of the Rolok and tightened until the rusted threads broke free. I then removed the nut by holding with the easy out. One nut was so tight that I had to cut it with a Dremel to get it off. If the end of the Rolok was very rusty, a 5/16 nut worked, however, if the end of the Rolok was clean, a 5/16 nut did not work. Double nutting also did not work.

I appreciate reading your technical description of your bulkhead horror. Will written. Wish I could have been assisting you as the hands on experience would have been a valuable asset. I had the rear bulkhead repaired by xtreme graphics before finalizing the purchase. However, after reading all the posts on it, it seems to be a ever present danger. John

Roloks are made for rapid production for use in a dry environment, and are not suited for the application Foretravel has chosen for them. After considering many options, I bought a box of 50 3/8" 316 stainless bolts and not even bothering to test the remaining Roloks, have doubled up over the existing number of OEM fasteners and put washers and nuts on the opposite side. Using a borescope, I could see the interior of the rectangular tubing was rust free. If you test them with a torque wrench and they fail, there is no way to remove the remaining part. They always fail in the same location because of a combination of rust jacking and hydrogen embrittlement. The Roloks have zero corrosion protection and start loosing strength from day one.

I have done a few at a time over the last couple of years. After I finish, I will pull a few at a time and place washers between the big angle iron and the bulkhead so no moisture can collect there. Our U300 was very rust free except for the back of the angle iron.

Stainless fasteners are very inexpensive if you go on ebay and buy in bulk.

Pierce

Did you cover the access holes after you were finished?  Just curious.  By the way, in regards to the comment about stainless fasteners, stainless fasteners are significantly softer than steel.

Thank you so much for this!  This has given me the confidence to take on the bulkhead myself using this method

We probably all worry about this.  The good news is, watch it, catch it, and it is easily repaired if you don't wait too long.  A PITA, but repairable.

Forgot to mention, the day after I bought my 1990 U280, Brett saw it sitting in the roadside storage where I had it temporarily stored and stopped by.  Right after he said "Hello, my name is  Brett Wolf"  He said " you check those bulkheads yet".  I said " what bulkheads?". Been worried ever since!  I sure am glad he stopped by, I learned more about Foretravel in ten minutes than I would have found out in a year on my own.

Not all stainless fasteners are created equal... The ⅜" ARP 170K PSI fasteners I used in my repair are stronger than Grade 8 automotive.
ARP Stainless Steel Bolts 623-4000 - Free Shipping on Orders Over  at Summit (http://www.summitracing.com/parts/arp-623-4000)
Don

3/8" is much larger than 5/16" and 316 is stronger than 308 stainless. Bottom line is Class 5 fasteners are about 20% stronger than same size 316 stainless. Stainless fastners are plenty strong for the use and 1/3 the number would be more than enough. The Roloks have nothing even close to their original strength but still hold it together. Check inline with the tire spray for the first failures. Grainger has covers that will work for the holes in the bottom. And, as pointed out, there are stainless fasteners stronger than class 8 with on only down side being the price.

Since our coaches have very little corrosion protection, they need to have the undercarriage washed after driving in northern or eastern states in the winter. The angle iron/bulkhead area should be at least looked at before any major trip.

What also has to be considered is a wet bay leak can rust out much of the rectangular tubing in the rear area.

A flat chisel driven up between the angle iron and the bulkhead tubing will spread them far enough apart to get a long sawsall blade up between the area to clean out the rust.

Pierce

My experience suggests that using an appropriately rated hydraulic bottle jack, one on each side in front in front of the duallys, along with frame blocks (I suggest the 12" harbor freight 2" square hitch extensions) to spread the bullhead joint in a controlled fashion is the easiest way to gain access to address the rust between joint. In fact, if you were (and I am not suggesting that you do this) place the frame blocks in front of the duallys without blocks behind them, you will likely see the joint separate in an alarming fashion if you have already removed all the fasteners. If you have not removed the fasteners and your joint is weakened or compromised, you will likely hear the weakened roloks give way as the suspension tugs on the joint through the trailing arms.
Don

I would like to suggest that an INCH pound torque wrench be used for this procedure.

Sorry if I missed it if someone already made this suggestion.

LPS 3 works well to inhibit rust/corrosion.. pc



 

Yup, in the original writeup: Bulkhead Repair-- A Comprehensive Look (http://www.foreforums.com/index.php?topic=8645.0)

Don,

Yes, big mistake to remove all of them. I removed about 5 at a time, spread the two pieces with the chisel, used the sawsall, installed the stainless and then went to the next 5. No danger of any incidents that way. To remove the rust, you only need a very small gap, just big enough to get a sawsall blade in.

Pierce

I plugged the 1 3/8 inch holes in the fiberglas with the Hayco Plugs in Brett's excellent Bulkhead Repair article. The four holes on the driver side where the extra 1.5 inch square tubing is will be plugged with modified Hayco plugs stuck on with 3M auto side moulding tape. Temporarily sealed with tin foil butyl tape at this time.

The torque wrench I used was a small 1/4 drive 250 inchpound torque wrench which cost much more than a 150 ftlb torque wrench.

I plan to replace one Hayco plug on each side with an air vent similar to the ones which Foretravel installed for the fuel tank.

You don't specify how thick the 1.375 OD washers that you used for the test, but I would expect that if they were thick enough themselves not to deform, then the result of over clamping would be that the walls of the tubing that are parallel to the bolts would suffer a convex deformity. I did some tests as well (videos posted on youtube I believe), and that lead me to use 1 & ½" X 3/16" thick rectangular stock or 3/16" thick angle iron welded to a sisters course of ⅛" square tubing (welded to the original ⅛" thick walled transverse frame member that forms the basement side of the bulkhead joint). There was no deformity with the bolts torqued to 45 foot pounds using ARP Ultra Torque Lube. Additionally, I welded 3X5"X3/16" thick rectangular tubing with gussets to the heavy engine carrier frame member that also supports the suspension. I later found that Foretravel added similar bracing (but without the gussets) on later Unihomes, at least on the longer coaches that I have had a chance to look at. This wasn't strictly necessary, but this added support where the vertical angle iron had cracked and that is where the bulkhead hinged as it the joint separated. Hard to explain, so I will add a couple of pictures. These supports are alongside to the 3X5" vertical supports welded to the suspension shackles and (at least in my mind) help resist the pull on the joint applied with the retarder, as well as the tug just from normal up and down movement of the axle. The way I see it, these shackles connect to the trailing arm and locate the axle front to back, so any up and down movement of the axle will naturally use the shackles as a pivot point.
Don
P.S. I know the horror of which you speak and I am pretty sure I know the feeling that swept over you as you discovered the separation. I felt it too, and it ended up being very long learning process with a pretty steep curve. You seem like you were already well equipped to deal with it. I bet you are glad it is your rear view mirror now, I know I am glad that is behind me and now I can do much more fun projects ::)