Re: Bulkhead Separation

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Re: Bulkhead Separation

September 11, 2010, 08:59:41 am

Quote

I am wondering , if the weight of the mc carrier plus the bike would tax the structure of the coach. This could be in the range of 1200 lbs. Thinking big HD.
FT indicated the cause of one members delamination on the sidewalls was due to towing a trailer with heavy tongue weight.
With that said ,what would FT OK as safe tongue weight for the structure.

I think that blaming the delamination or bulkhead separation on tongue weight is bogus and is shifting the blame from FOT to the owner. I would be willing to bet that none or maybe one or two of the many, many bulkhead separations were from over-gross or over tongue weight situations.

IMHO, when they were building older FT's with the smaller engines, the "screws" that held the caps on were OK. When they went to the BIGGER and MORE powerful engines with BIGGER and HEAVIER coaches, the inappropriate"screws" stayed the same.

Too much torque, too much power, too much load, not enough engineering for the changes and upgrades. (Along with rust jacking, again, an engineering design issue where the fresh water overflow is designed to drain onto the cap seam).

It would be interesting to have a survey to see how many bulkhead separations there are/were out there and what they towed!

Again, as an engineer, IMHO.

Re: Re: Bulkhead Separation

Reply #1 – September 11, 2010, 09:40:09 am

Towing has nothing to do with bulkhead separation.

The bulkhead(s) is forward of the rear drive wheels. When accelerating with a heavy trailer, the rear drive wheels are forcing the bulkhead together. When braking with a heavy trailer, the trailer is forcing the bulkhead together.

So, what tries to separate the bulkhead, especially the rear one?

It is the retarder. The retarder is slowing the rear wheels but not the front wheels as would the brakes. So the rear bulkhead transfers the slowing effort to the front of the coach. This is the force that tries to open the bulkhead joint.

The only way a heavy trailer could apply the same type of force is to slow the coach by using trailer brakes only, no retarder and no coach brakes.

Hope this helps you all understand the way forces are applied to the bulkhead and what might be the source of those forces.

Re: Re: Bulkhead Separation

Reply #2 – September 11, 2010, 10:03:45 am

The more I read about the newer coaches, the more I appreciate my Old Timer. So if I understand correctly, the Oldies that don't have a retarder shouldn't have Bulkhead separation problems. Is that correct?

I have been thinking about adding the Banks Power Pack so I can pull a 24' enclosed car hauler at around 8,000 lbs. I know it will put a strain on my tanny but I was also worried about the bulkhead issue.

Re: Re: Bulkhead Separation

Reply #3 – September 11, 2010, 10:32:07 am

Kent,

A properly secured bulkhead is perfectly capable of any trailer within the gross weight limits of the coach. Our full mono-cock chassis is the strongest, lightest coach out there.

However, the rust jacking of the type of bolts selected to secure the bottom of the bulkhead compromised that system. As long as no corrosion, no deterioration of the clamping system for the bulkhead; no problem.

Before my coach bulkhead became a concern, I had James Stallings re-do the bolts and corrosion protect the joint. Plus I re-routed the fresh water tank overflow (per Barry & Cindy I think) to out the bottom of the coach and not down the back of the rear bulkhead right on the suspect joint.

The retarder exerts the same type of force on the bulkhead as would an exhaust brake or Jake engine brake. One of the mentioned devices is needed on our coaches. Just the retarder is the best of the three. Driving without one is possible but much more challenging in the hills.

Re: Re: Bulkhead Separation

Reply #4 – September 11, 2010, 01:04:55 pm

Quote from: Kent Speers – September 11, 2010, 10:03:45 am

The more I read about the newer coaches, the more I appreciate my Old Timer. So if I understand correctly, the Oldies that don't have a retarder shouldn't have Bulkhead separation problems. Is that correct?

From what I have read, any of us with the UniHome, UniCoach and what ever it is currently called chassis do have to worry about Bulkhead separation. I know on my '94 U225 that bad bolts have been found and replaced. It is not a difficult thing to fix and luckily we have great instructions from Brett Wolfe. I do think those of us who live and travel in snow country have to worry more that others, but we all have to keep watch on this!!!

Re: Re: Bulkhead Separation

Reply #5 – September 11, 2010, 01:28:39 pm

Kent,

Quote

The more I read about the newer coaches, the more I appreciate my Old Timer.
So if I understand correctly, the Oldies that don't have a retarder shouldn't have Bulkhead separation problems. Is that correct?"

Unfortunately, not having a retarder doesn't prevent our old coaches from having bulkhead separation.
My '92 U280 had significant rust jacking and separation and it only has a fairly ineffective exhaust brake.
The previous owners did pull some sort of trailer, so that may have had an effect on the bulkhead separation.

I wish

Re: Bulkhead Separation

Reply #6 – September 11, 2010, 01:38:40 pm

Yes, the bulkhead issue applies to all Unibody and all but perhaps the latest Unicoaches (where I understand the method of attachment was changed).

Again, no reason to worry or speculate.

Grab a torque wrench and verify-- 250 INCH-pounds on all bulkhead bolts. Visually inspect the joint for separation or rust. Twenty minutes and you will have the FACTS. As always on air suspension coaches, block it before going under.

I do this on 100% of the Foretravels I do mechanical inspections on-- did one on Thursday.

The repair can range from a clean and apply a 1/2 can of undercoating to seal the bolts and joint area to an extensive repair-- but it is SO easy to determine what you need that speculating is kind of silly.

Brett Wolfe

Re: Re: Bulkhead Separation

Reply #7 – September 11, 2010, 01:42:37 pm

Well now that is as clear as mud. Seriously, my understanding is that separation is probably affected by both the climate in which the coach is operated and the forces exerted by both non-service braking and or pulling heavy loads. I remember when this first came up and it sounded like a major flaw in Foretravels, but I really only heard about it on a few coaches. Last year both FOT and James Stallings told me that very few coaches showed signs of separation. Does this group know that a majority of the older coaches have this problem or is it still relatively rare.

I visually checked the rear cap bolts last year and what I saw looked fine but I am not sure I was looking at the right thing. I have not checked with the torque wrench. Brett, can you give me a link to your post on bolt inspection? I guess before I go investing in more horsepower, I should have it checked by a pro.

Re: Re: Bulkhead Separation

Reply #8 – September 11, 2010, 01:49:50 pm

Quote from: Kent Speers – September 11, 2010, 01:42:37 pm

I visually checked the rear cap bolts last year and what I saw looked fine but I am not sure I was looking at the right thing. I have not checked with the torque wrench. Brett, can you give me a link to your post on bolt inspection?

Here is the original post:

Bulkhead Repair-- A Comprehensive Look

This is on a 1993 U240, but it is my understanding that most applies to Unibody and Unicoaches.

I am not sure bulkhead is a descriptive term here. The center part of the coach is built on a strong grid system with 1 1/2" box beams with 1/8" walls at the ends (front and rear) where they attach to the 1/4" angle that is part of the frame holding the drive train (rear) and front end (front).

From the factory, the two "areas" were attached using 5/16" Roloks: (http://www.semblex.com/files/Rolok-Semblex.pdf)

The Rolok's go through the ¼" angle and torque into 1 1/2" box w 1/8" walls.

After talking with Mark Harvey at Foretravel and an engineer at Rolok, I went under the coach. First, I looked for any separation in the area of attachment. NONE-- just some light superficial rust that I will sand and undercoat.

Next, I put a torque wrench on each of the Roloks. Check torque to 250 INCH (repeat INCH) pounds. Check torque CW and CCW. If they don't hold you need to know that. If it loosens, use that hole (drilled to 3/8") to install a thru-bolt.

What I found was that 5 Rolok bolt "heads with 4 threads" broke IMMEDIATELY-- at less than 20 inch-lbs. All the rest did not move at 250. In inspecting the failed Roloks, all had been broken for a long time-- light surface rust on the sheared surface. The "4 threads" mean they were broken where they started torquing into the 1 1/2" beam. Could have been broken at installation or from sheer stress afterwards. Not sure it matters.

The fix: As well described by others, the answer is to thru-drill and install 3/8"X 3", Grade 8 bolts and nuts on either side of the "failed" Roloks. Yes, you can use shorter ones, but the 3" ones made the job a little easier. Because I wanted to be able to torque the thru-bolts to 275 in-lbs without taking any chance of crushing the box beam, I made some 1 3/8" X 1 3/8"1/8" plates to install next to the beam (cost me a piece of steel and $10 at a machine shop). So on the rear, from the rear: the 3/8" bolt, washer, 1/4" angle, 1 1/2" bulkhead, 1 3/8X 1 3/8X 1/8" plate, washer and pinch nut. All hardware grade 8 (except plate). Torque 275 in-lbs.

I used good quality Cobalt bits, progressing up one bit size at a time, using plenty of cutting oil and keeping the bit cool. Then, to access the "inside" to install the plate, washer and nut, I used a 1 3/8" hole saw to cut through the very thin fiberglass bottom of the coach. Hole was centered on the bolt left to right and the closest edge of the hole was approximately 3/4" in from the inboard edge of 1 1/2" beam. This allows access with a screwdriver to easily remove the foam core, exposing the beam and also access for the 9/16" wrench to tighten the nut. When locating the thru-bolts, use a magnet to locate the other beams in the fiberglass "floor" to the basement. Since you need access to install the plate, washer and nut, obviously, avoid areas with beams in the floor.

I wanted a water-proof plug-- driving through rain could "challenge" plugs not designed to keep water out unless sealant, etc was used.

The largest I could find was the 1 3/8" Heyco plug PN 3837 (http://heyco.com/products/sec_02/2-09.html). This really gave plenty of access.

The other suggestion is that, at least on the coaches I have seen, there isnothing keeping water from migrating in past the head and threads of the Roloks-- i.e. the 1/4" beam is drilled larger, so the Rolok threads will torque in the 1 1/2" beam. That leaves room for water to migrate in along the side of the Rolok where it goes through the 1/4" beam. I will solve that by wire brushing the beam and short metal "skirt" just inboard of it. Then put masking tape on the head of the Roloks (where a socket would fit) and use automotive undercoating to seal the area, making sure the Rolok to beam joint is protected.

I suggest to everyone that this is ROUTINE PREVENTIVE MAINTENANCE AND THE ROLOKS NEED TO BE CHECKED ANNUALLY.

It wasn't a fun project, but neither was it mechanically challenging or expensive.

Brett Wolfe

Re: Re: Bulkhead Separation

Reply #9 – September 11, 2010, 02:14:17 pm

Brett, my biggest issue is to know exactly what I am looking at. The next time you are under your coach, could you take a photo of the area and the holes you drilled and email it to me. I think your U240 chassis is the same as my U225. Or, the next time I am in SE Texas, which could be in the next couple of months, I can hire you to do the inspection. I had FOT check it last year but the way they down played the issue, I was not convinced that they did a thorough job.

Re: Bulkhead Separation

Reply #10 – September 11, 2010, 02:22:54 pm

Quote

could you take a photo of the area and the holes you drilled

There are some photos here of a couple of Foretravels Bulkhead issues
http://beamalarm.com/Documents/bulkhead_separation.htm

Re: Bulkhead Separation

Reply #11 – September 11, 2010, 02:55:11 pm

Barry, those were great. However, if I need the repair it looks like quite a job. As Brett said, challenging in effort more than skill.

Thanks!

Re: Bulkhead Separation

Reply #12 – September 11, 2010, 02:57:43 pm

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However, if I need the repair it looks like quite a job.

Check it early and often before it becomes a problem.

Re: Re: Bulkhead Separation

Reply #13 – September 11, 2010, 03:41:58 pm

Barry is correct. It usually starts as a single or pair of broken bolts. If replaced, no big deal. But if two in a row are broken it puts more stress on adjacent bolts and it progresses from there.

If you go under your coach and (looking at the rear bulkhead for example) look where the white fiberglass floor for the basement ends, there is an angle beam with bolts going straight forward. THOSE are the ones that we are talking about. Very easy to see and put a torque wrench on.

Kent, put a torque wrench on them and take a photo and post here. If you don't have a torque wrench, apply only reasonable torque (like you were installing a spark plug in an aluminum head) on the bolts. You will likely find that they either are OK, or the bolt head falls off in your hand with little more than hand torque. I have yet to "break" a Rolok in checking a bulkhead. The bolts have either been good (torque up) or they were already broken.

The way you can tell they have been broken for awhile is that the surface where the bolt is broken is rusted. And they usually break 3-4 threads in from the bolt head. THAT is where the Rolok torques into the "near side" of the box beam.

Brett

Re: Bulkhead Separation

Reply #14 – September 11, 2010, 08:23:58 pm

Here are some pictures of it from the photo/files section as well .... complements on Don Hay

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And if you are not sure what the heck is a huck bolt is

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Re: Bulkhead Separation

Reply #15 – September 11, 2010, 08:55:15 pm

Remember!
Safety block the air springs BEFORE you go under the coach , for any reason.

Re: Re: Bulkhead Separation

Reply #16 – September 12, 2010, 12:28:23 am

I have a torque wrench and it appears that I checked the correct bolts last year. I will do so again tomorrow just to be sure and I will chalk the wheels.

Thanks to all.

Re: Bulkhead Separation

Reply #17 – September 12, 2010, 07:25:34 am

Yes chalk the wheels but also block up the coach so it can not lower on you as well.

Re: Bulkhead Separation

Reply #18 – September 12, 2010, 08:33:48 am

John,

While I am certainly not recommending against blocking it up, Kent's U225 has the torsilastic suspension and mechanical jacks. Even if the jacks failed, there is still plenty of room under the coach. And the torsilastic suspension has solid metal shims for ride height adjustment-- no ride height valves or air suspension to fail. Same applies to the U240.

Your warning is absolutely on target for any air suspension coach.

Brett

Re: Re: Bulkhead Separation

Reply #19 – September 12, 2010, 10:56:52 am

I just finished my inspection of the Roloks. Although they all looked good with very little sign of rust, I did found two Roloks in the front and five in the back that would not take the torque. Of the five in the back, there were only two adjacent to one another but I will be replacing all of these bolts this week.

I do have a question. Not having air suspension, when I first read about blocking the coach I couldn't figure out what blocking meant because with the suspension on our U225's and U240's they don't squat down like the rest of the Foretravels with air ride. See, there are advantages to simplicity. That being said, with air brakes can the coach roll if for some reason the air pressure is released? Is chalking the coach really necessary?

Re: Bulkhead Separation

Reply #20 – September 12, 2010, 11:00:05 am

Kent,

NO. Loss if air pressure has no effect on the parking brakes. The parking/emergency brake is SPRING applied, AIR released. That is why you can't release the parking brake until air pressure has built to 60 plus PSI.

Brett Wolfe

Re: Bulkhead Separation

Reply #21 – September 12, 2010, 06:06:41 pm

I like the idea of a survey to see how many and what model, and year and length of coach etc.
has been affected.

Re: Bulkhead Separation

Reply #22 – September 12, 2010, 09:17:23 pm

Steve,
Is that a hard thing to do, put some sort of survey/questionaire in the forum?

Re: Bulkhead Separation

Reply #23 – September 12, 2010, 09:24:15 pm

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Is that a hard thing to do, put some sort of survey/questionaire in the forum?

To many variables on causes.
I don't know what it will really tell us.
The key is to inspect often so it does not happen.

Re: Re: Bulkhead Separation

Reply #24 – September 12, 2010, 10:02:22 pm

Quote from: Mike Baldacchino – September 12, 2010, 09:17:23 pm

Steve,
Is that a hard thing to do, put some sort of survey/questionaire in the forum?

Mike,

I believe I have it set up so any member can set up a poll should they choose. When viewing the boards topic list, next to the new topic button there should be a new poll button ... this will open up a page that looks a lot like a new post but will allow you to ask you question and any number of answers to the question, how long the poll is open etc .... The way polls work is you can supply your vote and also post about the poll like a regular topic, its a rather nice feature.

As Barry noted not sure at what point anything will become statistically relevant .. as the saying goes, lies, damn lies and statistics

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