bulkhead blues

Topic: bulkhead blues (Read 12047 times) previous topic - next topic

Re: bulkhead blues

Reply #100 – July 10, 2012, 10:10:39 pm

I don't know how that did the drilling, but in our coach, there was quite a bit of variability in the angle of the bolt holes. Some were significantly off of perpendicular and one ended up at the intersection of one of the longitudinal frame members. Also, the spacing was not uniform but looked pretty seat of the pants to me. The fact that the coach stayed together as long as it did, is a testament to the overall design in my view. Had our coach not had the fresh water leaks, it would probably still torque up fine. Now, I would have liked to see more beef on the axle side of the bulkhead to keep the bulkhead joint from taking the load from the trailing arms. That wouldn't have saved the coach from the rust damage, but the consequences would not have been as severe. A little bit of PM from the PO would have kept the rust away...

Don

Quote from: Chuck Pearson – July 10, 2012, 08:45:10 pm

It would be interesting to know how the factory does, or did the drilling. Suspect the angle was predrilled, the rest field drilled. Redundancy can make up for derating.

Re: bulkhead blues

Reply #101 – July 10, 2012, 10:20:59 pm

Hi Don, I whole heartedly agree about more beef in the axle subframes. I've been looking at transit bus chassis for a long time and it's very common to see an axle sub-frame cradle assembly that's self supporting with suspension torque arms attached. Foretravel took a different approach - the Colin Chapman approach. I'd like to see what Foretravel is using today. I know that they've changed their design. Anyone have any info? David

Re: bulkhead blues

Reply #102 – July 11, 2012, 12:08:48 am

It really is only lacking in one area, and that is where the top of the bulkhead meets the very heavy duty backbone that supports the engine and tranny and has transverse sections which are also very heavy duty which take the full weight of the coach via the air springs. The probelm is that the trailing arms are welded to the bulkhead angle iron and the vertical supports which go up fro there aren't (as far as I can see) attached to that backbone frame, but rather are just out board of it. this (I believe) allows the bulkhead to hinge from the top with nothing but the bulkhead joint and four 2"X1/4" pieces of angle iron welded to the backbone to hold the bulkhead perpendicular to the backbone. Those trailing arms pull on the bulkhead joint every time you use the retarder or exhaust brake. When the joint is comprimised by failed Roloks for whatever reason, those relatively small vertical pieces of angle iron (at least in my case, and in the case of Christies dream apparently) crack right where they are attached to the backbone. It really isn't just one factor, several things have to line up to allow that to happen but in my mind, fixing the bulkhead in a perpendicular alignment to the backbone without relying on the bulkhead joint would make the coach pretty bullet proof. I think that it isn't all that hard to do, and I believe that I have the plan to insure the integrity of that prependicular relationship but I am going to great lengths to insure that the basement framing forward of the bulkhead is up to the task anyway. After all, it may be required to support the weight of 112 gallons of fresh water, 164 gallons of waste, 148 gallons of diesel, maybe 3 8D AGM batteries and all our gear!
Don

Quote from: travelite – July 10, 2012, 10:20:59 pm

Hi Don, I whole heartedly agree about more beef in the axle subframes. I've been looking at transit bus chassis for a long time and it's very common to see an axle sub-frame cradle assembly that's self supporting with suspension torque arms attached. Foretravel took took a different approach - the Colin Chapman approach. I'd like to see what Foretravel is using today. I know that they've changed their design. Anyone have any info? David

Re: bulkhead blues

Reply #103 – July 11, 2012, 12:44:46 am

I would like to get a look at a complete set of frame drawings. Gam

Re: bulkhead blues

Reply #104 – July 11, 2012, 09:05:13 am

Some good ideas here, from Don, David and Gam, all excellent points. I would like to, at some point, come to a consensus regarding preferred method of repair for both preventative fixes and repair fixes in cases where a few broken bolts are found. In cases of massive failure Don's fix is, in my mind, the best. The goal is to avoid getting to that point.

If we can agree on an standardized approach then I'd like to focus on the technique of repair and try to come up with a locating/drilling fixture to simplify and precisely locate and drill for the new fasteners. Whether they are bolts or Rolocks it would be an advantage for them to be precisely and uniformly drilled. I'm thinking a fixture that would reference the angle iron with a drill that moves in two axis (Z and X) would be fairly simple to fabricate and use. I will build it, use it on my coach, and pass it along to whoever else needs it. This could also be supplemented by the purchase of a large quantity of the selected fastener, some kind of plugs for the cover panel if the nut approach is taken. A fix in a box, just add labor. I think this is a worthy goal that could benefit the group that prefers to fix their own stuff for whatever reason.

Regarding the 1/4 vs 3/8 Rolocks and the limitations of the 1/8 tubing "nut", seeing as where there are no reports of stripped Rolocks but they are all broken at the shank, might there be an advantage to the 3/8 from a durability standpoint? Being able to drive them into existing holes is appealing, I would think you should be able to back existing Rolocks out without any problem if they are in decent shape. If they are so weak that they snap on withdrawal then you haven't really lost anything. Am I right here, or is it possible that rusty 1/8 tubing could grip a good Rolock hard enough to snap it? Would the additional hole size necessary be a negative vs increased fastener density of 1/4?
Karma sent.

Chuck

Re: bulkhead blues

Reply #105 – July 11, 2012, 09:17:27 am

Quote

I'm no welding expert, but I think it's cause it's bad form to put a weld in bending: Don't Put Welds in Bending. To keep the weld bead (root, toe, and face) out of the compression and tension of bending will require a connection redesign.
David

OK That makes sense.

Roland

Re: bulkhead blues

Reply #106 – July 11, 2012, 09:38:27 am

Right. It's bad form to put a weld in bending.

I made them modify the big 2 tier emergency power battery racks in a nuclear power plant because the angle toe was welded to the post but the angle heel was not. I opined the racks would collapse in an earthquake.

best, paul

Re: bulkhead blues

Reply #107 – July 11, 2012, 10:10:46 am

Quote from: Paul Smith – July 11, 2012, 09:38:27 am

I made them modify the big 2 tier emergency power battery racks in a nuclear power plant because the angle toe was welded to the post but the angle heel was not. I opined the racks would collapse in an earthquake.

best, paul

Boy, there went your Christmas bottle of Glenlivet from the contractor....

Re: bulkhead blues

Reply #108 – July 11, 2012, 10:25:34 am

Paul They didn't have 87 lbs of documents, 47 welding procedures, and 21 signoffs for fabrication of the racks? Gam

Re: bulkhead blues

Reply #109 – July 11, 2012, 10:50:39 am

A drilling fixture would be an excellent approach if you don't already have separation in the joint. Since the trailing arms mount to what I am calling shackles that are welded to the angle iron, joint failure leading to separation allows the the bulkhead to to hinge from the top and the angle iron vertical face is no longer parallel to the transverse square tube. So the fixture, while making the hole perpendicular to the angle iron, would insure that the entry hole through the square tubing was not at the same level as the exit hole. That would of course depend on the degree of separation, but in the case of our coach, the angle iron was also bowed with the crown between the two trailing arm shackles. Since I had full access to basement side of the joint and was able to remove the old fasteners, by either double nutting (that worked for about half) or welding a nut to the end, I used the original holes to pull the joint together with through bolts before drilling the couple of extra holes.
Don

Quote from: Chuck Pearson – July 11, 2012, 09:05:13 am

Some good ideas here, from Don, David and Gam, all excellent points. I would like to, at some point, come to a consensus regarding preferred method of repair for both preventative fixes and repair fixes in cases where a few broken bolts are found. In cases of massive failure Don's fix is, in my mind, the best. The goal is to avoid getting to that point.

If we can agree on an standardized approach then I'd like to focus on the technique of repair and try to come up with a locating/drilling fixture to simplify and precisely locate and drill for the new fasteners. Whether they are bolts or Rolocks it would be an advantage for them to be precisely and uniformly drilled. I'm thinking a fixture that would reference the angle iron with a drill that moves in two axis (Z and X) would be fairly simple to fabricate and use. I will build it, use it on my coach, and pass it along to whoever else needs it. This could also be supplemented by the purchase of a large quantity of the selected fastener, some kind of plugs for the cover panel if the nut approach is taken. A fix in a box, just add labor. I think this is a worthy goal that could benefit the group that prefers to fix their own stuff for whatever reason.

Regarding the 1/4 vs 3/8 Rolocks and the limitations of the 1/8 tubing "nut", seeing as where there are no reports of stripped Rolocks but they are all broken at the shank, might there be an advantage to the 3/8 from a durability standpoint? Being able to drive them into existing holes is appealing, I would think you should be able to back existing Rolocks out without any problem if they are in decent shape. If they are so weak that they snap on withdrawal then you haven't really lost anything. Am I right here, or is it possible that rusty 1/8 tubing could grip a good Rolock hard enough to snap it? Would the additional hole size necessary be a negative vs increased fastener density of 1/4?
Karma sent.

Chuck

Re: bulkhead blues

Reply #110 – July 11, 2012, 12:18:04 pm

If during fabrication the 5/16" holes were drilled in the angle iron on a drill press. then that part was aligned to the box tubing frame and the pilot holes for the Roloks where drilled by hand,any angular miss alignment of the holes would cause a bending moment in the Rolok when it was torqued. A screw with a high tensile strength like a Rolok is brittle and with more load under one side of its head then the other ,and repeated loading and unloading (like with the retarder) will tend to fracture just past the first bolted member. If someone can send me a broken Rolok I will try and have it looked at by a Metallurgist.Gam

Re: bulkhead blues

Reply #111 – July 11, 2012, 12:54:37 pm

Don't know. Our walk down was a result of a TMI issue. TMI identified they did not have paper certifying the environmental qualification of equipment. And failure of equipment in a steam environment was a factor in the accident. Billions was spent replacing equipment.

It was then noticed that paper demonstrating earthquake qualification was lacking.

We developed specific walk down procedures for each type of equipment based on the performance of equipment in past earthquakes - such as the 1985 magnitude 8 earthquake in Chile that I did the initial rapid survey on. A later team performed the detailed survey.

This was for the 40 or so oldest nuclear power plants.

Best, paul

Quote

Paul They didn't have 87 lbs of documents, 47 welding procedures, and 21 signoffs for fabrication of the racks? Gam

joseph gambaro
1999 U295 36'

Re: bulkhead blues

Reply #112 – July 11, 2012, 01:30:03 pm

Paul I worked some at Enrico Fermi #1 for DTE in 1965. The plant that all most blew up Detroit (what a joke). Later on I worked as a mechanical and piping inspector for DTE on a project with Bechtel as the general contractor. They can generate more paper work then the NRC !!! GAm

Re: bulkhead blues

Reply #113 – July 11, 2012, 03:10:25 pm

Quote from: gam – July 11, 2012, 12:18:04 pm

If someone can send me a broken Rolok I will try and have it looked at by a Metallurgist.Gam

That'd be great Gam. The broken ones tend to be very rusty but they may still tell a story. If anyone removes any unbroken bolts maybe they too can be forwarded to Gam. Unbroken bolts may offer clues as to the start of failure. Another piece of the puzzle. David

Re: bulkhead blues

Reply #114 – July 11, 2012, 08:10:09 pm

Just sitting here daydreaming about bulkheads and I'm thinking is there anyway to get to the inside of the 1 1/2" box section? We're talking jigs to help place and drill holes precisely, but the 1/8" nut seems to be a perennial problem. What if we took an 8' length of steel flat bar or maybe two 4' sections, say 1"x3/8". We could drill and tap holes every so many inches using the same jig that drills holes into the 1/4" angle section. Each hole in the flat bar could then be tapped. The question is... Is there any way to get to the side of the box section to slide these flat bar sections inside of it? David

Re: bulkhead blues

Reply #115 – July 11, 2012, 08:14:46 pm

David,

Were you to remove fiberglass to access the box beam, you could just as easily use large rectangular washers and nuts.

The rectangular washers could easily be made from 1/8" or 1/4" steel: 4-6" long by 1 1/2" tall. Much easier to align and would give the same clamping force you are suggesting.

Re: bulkhead blues

Reply #116 – July 11, 2012, 09:26:56 pm

The tapped 1/4" flat bar scheme inside a square tube was used to secure a precision rail on the Y axis of a CNC table I built. I was not impressed with it, suspect that the rolled threads produced by a Rollock in 1/8 tube have more strength than tapped 1/4 bar. Could be I'm a lousy bolt tapper but there just didn't seem to be enough meat there.

The idea of using a larger quantity of Rollocks is appealing for a couple reasons:

Ease of installation-no cutting of body panel, no foam removal, no patching.

Quick to install, especially with some type of alignment jig.

Can possibly be upsized a bit in dia. Increased fastener density no problem.

That said, there are reports from Brett and others indicating good service and no failure from bolted connections. I think if you have separation in the joint, that level of failure, that bolts and backing plates would be the way to go due to alignment issues that have been pointed out. No reason you couldn't add a few extra of these either.

This will be preventative maintenance for me, no sign of bulkhead separation. The Rolocks, in this case will be a simpler installation.

Re: bulkhead blues

Reply #117 – July 11, 2012, 09:40:14 pm

Quote from: travelite – July 11, 2012, 08:10:09 pm

Just sitting here daydreaming about bulkheads and I'm thinking is there anyway to get to the inside of the 1 1/2" box section? We're talking jigs to help place and drill holes precisely, but the 1/8" nut seems to be a perennial problem. What if we took an 8' length of steel flat bar or maybe two 4' sections, say 1"x3/8". We could drill and tap holes every so many inches using the same jig that drills holes into the 1/4" angle section. Each hole in the flat bar could then be tapped. The question is... Is there any way to get to the side of the box section to slide these flat bar sections inside of it? David

David,

That very same thought came to me yesterday. The compartment can be opened, the white curved plastic/fiberglas can be carefully sectioned about 3 inches and then there is easy access to the 1 1/2" square tubing. I was thinking of a 1" wide flat bar, either full length or half length. It could be 5/16" or so in thickness with grade 8 nuts tacked to the far side or 1/2" and just tapped.

I was under my U300 today and was able to unscrew the last Rolock nearest the curb. There is no evidence of any rust inside the tubing as the threads are very clean except where the back of the angle iron and the bulkhead meet along with a small amount where the Rolock enters the sistered 16 gauge tubing. The failures seem to be on the outside of the tubing and it apparently very dry inside the main tube as the broken Rolocks seal the water out.

The big surprise was when I removed one Rolock in the middle of the failed field of 6. I used a long torque wrench and attempted to remove it. After applying considerable pressure, the Rolock failed with a big bang shooting the bolt head out of the torque wrench and about 20 feet away. Before this attempt, I had a gap of about a hacksaw blade thickness for several inches. Suddenly, I have a quarter inch gap for 18 inches. This could explain the sudden failure experienced last month by a member.

The other problem in inserting a bar is the Rolocks that have broken off. They are still inside and unless they can be removed, I can't see a way to get past them. A long sawsall blade could catch the first foot or so but after that if the others fail, it would be difficult.

In looking at Don's photos, the ends at each side have the 16 gauge square tubing sistered on so any bolt, even with a flat plate 5 inches long, could not be tightened to recommended torque, certainly not a grade 8. Since all of my failures are behind the double tubes, this makes the repair a little on the edge.

After today, I would say that in checking the condition of your Rolocks, the bolt head should be loosened at least a turn before tightening to the torque spec. This is the only way to check if it is on the verge of failure. Pulling it out and checking for rust 1/4" in from the head will give the best indication of it's condition.

Here is the good one I pulled.

Pierce

Re: bulkhead blues

Reply #118 – July 11, 2012, 09:56:58 pm

I considered this option, but in my case, I was unsure that the 1/8" square tubing might be too thinned out so that the wall of the tubing might fail if it was all that was holding the joint together. Also the precision necessary would be very challenging. To get at the open part of the bulkhead transverse tubing, you would need to remove the bottom extruded aluminum trim piece whereupon you will find that there is a 1.5"X1.5"X1/8" angle iron that runs the full length on both sides of the coach (except where the sewer etc. connections exit on the unicoaches) capping off the end of both front and back transverse bulkhead tubes. I replaced that piece as well as the longitudinal outer most square tubes (and many others), so I had full access to do something like this. Besides my concern for the wall thickness, there was one Rolok that I couldn't get out because it basically came through right at the junction of one of the longitudinal frame members. It was about in the middle, so I would have had to have found a way to bust it out somehow. I also considered inserting another piece of smaller square tubing inside the 1.5" transverse piece to reinforce the whole tube, but that had its own problems ( I.e., the seam present inside cold rolled steel tubing). Ultimately, I felt that doubling up all the way across and adding diagonal sections was the way to go because my utility compartment was completely gutted and I had unfettered access to all sides of the framing. By the way, the inside of the the inch and a half tube is 1.25" across, irrespective of the seam.

I had saved this a draft and see that Pierce has already talked about the broken Roloks inside the tube...LOL! Oh well, I may as well post it as is incase there is some bit that might help someone down the line... Pierce, on the Unicaoch, that outer trim piece is extruded aluminum maybe it is on yours as well. I did have a challenge getting some the screws that hold that in (several were broken already and a few others broke when I tried to remove them). Anyway, to access the end of the tube, you would need to cut the part of the eighth inch thick angle iron that runs on the outside of the framing that covers the end of the tube. That could potentially weaken it a bit. For what it's worth...
Don

Quote from: travelite – July 11, 2012, 08:10:09 pm

Just sitting here daydreaming about bulkheads and I'm thinking is there anyway to get to the inside of the 1 1/2" box section? We're talking jigs to help place and drill holes precisely, but the 1/8" nut seems to be a perennial problem. What if we took an 8' length of steel flat bar or maybe two 4' sections, say 1"x3/8". We could drill and tap holes every so many inches using the same jig that drills holes into the 1/4" angle section. Each hole in the flat bar could then be tapped. The question is... Is there any way to get to the side of the box section to slide these flat bar sections inside of it? David

Re: bulkhead blues

Reply #119 – July 11, 2012, 10:03:48 pm

Pierce. It sounds like you tried to remove the only one in that area that was holding the load for the broken ones. But the thing is the thread for that one with even that much load on it hadn't stripped or pulled out. It is looking to me like the real problem is how they where installed . Pilot hole not aligned with the 5/16" hole drilled in the frame. The fix could be as ez as a two piece spherical washer under the roloks head.Gam

Re: bulkhead blues

Reply #120 – July 11, 2012, 10:19:14 pm

Pierce,

In looking at the area where the heads of the broken ones were, can you see any indication that they were installed out of square to the material? Indications are that one Rollock was strong enough to do the job of 6 but several failed on either side of it with no rust problems. Hard to imagine an applied force that would do this.

It sure sounds like Gam's idea of misalignment is what is at work here. Pilot drill first then clearance drill, and keep it square. We all know that, right?

Chuck

Re: bulkhead blues

Reply #121 – July 12, 2012, 12:32:02 am

The Rolock in the photo was at the far outside, away from the direct spray from the wheels. The others show a lot more rust. It is apparent some rust jacking has taken place. Perhaps rust jacking as well as loss of strength from the rust may have been the culprit. So far, I have not seen any misalignment but have only remove the one pictured. The sudden failure of the one being removed seemed to be related to severe rusting in the threads next to the break in the 1 1/2" square tubing. It did not move a degree before suddenly failing. The head did show a great deal of rust at the 1/4" mark. Suspect this is the distance where rust jacking could have caused the failures in the others.

The front bulkhead has one more failed Rolock than the rear in exactly the same spot, directly where the front tire sprayed water on them. I can't help thinking this is more than a coincidence.

Can't rule out completely that the holes were drilled without a jig and misaligned but it seems unlikely judging by the quality of welds, and general quality workmanship seen underneath. The small locking ridges on the Rolocks as well as lack of any sealing or rust protection may be a factor in allowing water in. Some may have drained down between the angle iron and the bulkhead or wicked up. The rear tires throw most of the water back but enough is left in the tread to soak the area in the rain. The front bulkhead angle iron gets a constant stream on it from the tire in the rain. Could be the reason more failed up front.

Pierce

Re: bulkhead blues

Reply #122 – July 12, 2012, 01:00:26 am

Talk about going viral! Over 2100 hits in less than nine days?

Periodically new bulkhead participants stroke the alarm bells and create new theories and tangents to the bulkhead issue.
It's always possible (in making mountains out of molehills?) to lose sight of what is important to the general Foretravel population!

We could certainly make the well documented bulkhead issue into something weird enough to COMPLETELY scare away ALL potential future Foretravel buyers and cause ALL current owners to suffer irreparable sleep deprivation.
OR, we could logically, review the body of evidence and reasonably conclude that we have 99% or more of the information that we need to be perfectly comfortable.

SPECIFICALLY:
1. The bulkhead issue is easy to detect, should logically be a part of any pre-purchase body of wisdom, and routine inspection (250 in-lb. torque with a qualified tool) must be a part of each UNIHOME/UNICOACH owner's ongoing periodic maintenance/inspections.

2. We have heard from Foretravel, and their guidance is reasonable and perfectly understandable. Bulkhead Separation Can we or should we reasonably expect any more?

What's ROOT CAUSE IMPORTANT? We know that:
a. moisture/water aggravates the issue,
b. chlorides in the form of (from most to least severe) liquid deicers, rock salt and salt air aggravate the issue.
c. dissimilar metals aggravate the issue (galvanic cell corrosion)
d. Any coaches ever operated north of I-20 are automatically suspect and bear closer inspection/watching, especially if they were operated there between the months of October and May. Corrosion Article
e. If iron oxide (rust swelling) is present in the joint, the loose iron oxide must be removed and the surface area must be neutralized (eg. with phosphoric acid to turn the red iron oxide to black iron oxide (stable). This stops the oxidation, preserving and protecting the area prior to undercoating or otherwise protecting the bulkhead joint.

3. Then, thanks to Brett Wolfe's experience and wisdom, we know that once a bulkhead fastener failure is detected, there exists a comprehensive, tried and proven set of guidance on how to address the failure. Bulkhead Separation Owners that have done so (or have had FOT, MOT or Xtreme address the bulkheads) have peace of mind and VERY SOUND COACHES.

It isn't any more daunting than that and the bulkhead design should be a strong Foretravel selling point instead of the negative mystery that seems to be pursued in repeating, cyclical fashion. The Foreforums search feature yields a tremendous wealth of knowledge on the bulkhead issue (as well as speculation). Barry Beam's information condenses the vast wealth of FT knowledge into an easily searchable form that weeds out much of the chaff.

But reinventing the issue every few months doesn't create any improvement in the root cause understanding nor the action plan to address the presence of the issue. As Brett has said, "It wasn't a fun project, but neither was it mechanically challenging nor expensive." I would contend that it was a fun (DIY) project (for me), the repair has been easy to periodically re inspect and the repair has been perfectly stable since 2009.

Just my perspective, and I'm sure that it will not be universal, but I hope that this helps to tone down the severity of the alarm that is being created.

Neal

Re: bulkhead blues

Reply #123 – July 12, 2012, 01:01:32 am

One more thought . When the screw you where trying to remove failed under load the head shot out like a rocket. But for most of the failed screws the heads where still in there holes . So they didn't fail under load? The screw head just snapped off? Its 1AM and I can't sleep. Gam

Re: bulkhead blues

Reply #124 – July 12, 2012, 01:18:03 am

Expect they failed one by one so the angle iron did not move more than a few thousands of an inch each time. They stayed in place probably because they had a lot of rust. I had to pry some out of the angle iron with a screwdriver. When the last one popped, there were no others left so the angle iron jumped out. It was in the middle of the failed fasteners. I can now imagine what the highway failure must have been like last month.

10pm here. Just finished an old episode of Falcon Crest.

Pierce

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