BULK HEAD -front- 2 box beams

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BULK HEAD -front- 2 box beams

June 02, 2016, 10:29:57 pm

Last year I repaired my rear bulk head now I'm onto the front.
I researched this subject in detail last year before I started the rear, I purchased what I thought would be enough bolts and washers and straight iron for the front and back repairs. I chose 3 1/2" x 3/8" grade 8 bolts and a 1/8" flat steel strip to back the box beam.

I was surprised when I cut the belly under the front bulkhead. I found 2, 1 1/2" box beams against each other. I don't recall any body mentioning 2 beams on the front. The rolox bolts appear to fasten to the front box beam only.

My plan is to drill through both box beams with the 3/8" bolts. I should have just enough thread with the 3 1/2" length.

Is this double box beam in the front normal?.

Re: BULK HEAD -front- 2 box beams

Reply #1 – June 02, 2016, 11:36:30 pm

If you read Don's accounting of the build you will see he mentions them a few times. He even posted pics with them showing IIRC. Also the recent posting of the complete frame removal and new one will show double box sections in places.
JohnH

rusted bay floor frame

Re: BULK HEAD -front- 2 box beams

Reply #2 – June 03, 2016, 01:43:31 pm

I also noticed the double square tubing in the front when checking with a magnet so did not proceed with replacing the front 5/16 Rolok bolts. The tension loading on the front bulkhead is much lower then the tension loading on the rear bulkhead where the maximum tension happens when using the retarder, or when towing a trailer. All Rolok bolts on the front of my motorhome were present and passed the 250 inch pound torque test. Also, the Rolok bolts on the front are threaded through three 1/8 inch tubing walls, where most of the rear Roloks were threaded through just two walls. No rust jacking was happening on the front bulkhead where there was just surface rust.

Regarding grade 8 verses grade 5 bolts, here is something which I posted previously.

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

clamping forces to the 1.5 inch square tubing may cause the tube to permanently deform.

Re: BULK HEAD -front- 2 box beams

Reply #3 – June 03, 2016, 02:21:59 pm

On our 36' 99' U270, there is no double box beam on the front. I have attached a picture of the first 10' of the bottom basement skin before cleaning. You can clearly see the impressions of the framing imprinted on it. I have annotated it to make the layout easy to grasp. Different length, different year model, or different floor plan may or may not be different. It looks to me that maybe the early years of the Unicoach may have the double box beam up front...
FYI, I think you will find that the 3.5" bolts won't be long enough, especially when you include washers to catch enough thread to be secure. I double box beamed all across the rear of our coach with thicker tubing, 3/16" flat stock and use 4.25" bolts.
Don

Re: BULK HEAD -front- 2 box beams

Reply #4 – June 03, 2016, 02:30:21 pm

You are correct Don, the 3 1/2" bolts will not be long enough, I will have to order the 4" bolts for this repair.
Wyatt has good advice about the grade 5 bolts, If I went with grade 5 what are your thoughts on switching to Stainless steel bolts and hardware.
Hard to figure why Foretravel would double up on the box beams up front but go with a single beam in the rear.

Re: BULK HEAD -front- 2 box beams

Reply #5 – June 03, 2016, 02:33:17 pm

quote from Don "FYI, I think you will find that the 3.5" bolts won't be long enough, especially when you include washers to catch enough thread to be secure. I double box beamed all across the rear of our coach with thicker tubing, 3/16" flat stock and use 4.25" bolts.

I stand corrected on what Don's had but knew he had mentioned something about double boxing it. I have some doubling up across mine as I drilled into end to be able to spray some wax/oil mixture into them to help with any rust (should there be any) I took some Rolocks out and found them to be in new condition, so think all is good.
John

Re: BULK HEAD -front- 2 box beams

Reply #6 – June 03, 2016, 05:10:05 pm

Typical stainless steel bolts are roughly equivalent to grade 2 (unhardened steel sometimes called stove bolts as I recall), but depending on the alloy, very corrosion resistant. I suppose ⅜" stainless may be close to grade 5, 5/16" steel bolts, but it also depends on other factors. The Roloks are grade 5 equivalent, but are case hardened (the outside is harder than the core) so that if they aren't put in straight, they tend to weaken. So it depends somewhat on how the guy was feeling who first drilled the pilot holes for the bulkhead joint way back when. However, I think the design utilizing 17 bolts across the bulkhead has some margin for error built in. That is until corrosion becomes involved... Anyway, I used ARP (American Racing Products) ⅜" stainless steel 300 series bolts which are slightly stronger than typical grade 8 bolts (I think 170,000 psi tensile strength okay, checking... Ah, here it is!).

Quote

Material Specifications
ARP manufactures fasteners from a wide assortment of materials ranging from popular stainless steel and 8740 chrome moly to exotic alloys that have been developed to handle space travel.
You should also know that there are grades within specific alloys. For example, 8740 is available in four grades:
SDF (guaranteed seamless and defect free).
CHQ (cold head quality).
Aircraft.
Commercial.
ARP uses only the first two (SDF and CHQ), even though they cost more than double "Aircraft" quality.
Stainless Steel: Ideally suited for many automotive and marine applications because stainless is tolerant of heat and virtually impervious to rust and corrosion. ARP "Stainless 300" is specially alloyed for extra durability. It's polished using a proprietary process to produce a beautiful finish. Tensile strength is typically rated at 170,000 psi.

They are fairly expensive, but I actually paid more for Roloks from Foretravel!
Don

Quote from: Lon and Cheryl – June 03, 2016, 02:30:21 pm

You are correct Don, the 3 1/2" bolts will not be long enough, I will have to order the 4" bolts for this repair.
Wyatt has good advice about the grade 5 bolts, If I went with grade 5 what are your thoughts on switching to Stainless steel bolts and hardware.
Hard to figure why Foretravel would double up on the box beams up front but go with a single beam in the rear.

Re: BULK HEAD -front- 2 box beams

Reply #7 – June 03, 2016, 05:55:28 pm

When I refastened my bulkheads, in some places, I found doubling of the box beam usually in an area where something heavy was fastened, for example the propane tank.

Re: BULK HEAD -front- 2 box beams

Reply #8 – June 03, 2016, 11:05:51 pm

Here is the way my coach is set up. double butted box beams. I found almost all the bolts were broken, looked good from the outside. all were broke just inside the angle iron. Box beams look fine.
Looks like I have a lot of drilling to do as there is no way to double nut the broken bolts out.

Re: BULK HEAD -front- 2 box beams

Reply #9 – June 04, 2016, 01:28:21 pm

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. To facilitate this, 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 pounded on the end of the bolt with a rod/hammer to break down the rust holding the bolt. I then drilled into the bolt a quarter inch with a hard 9/64 bit (expensive).

You could also use a 1 3/8 hole saw to make an access hole where the end of the Rook bolt is.

Be sure to remove the aluminum sheet angle iron material because it will cause galvanic corrosion. I do not understand why Foretravel put it there.

Because there is unprotected iron square tubing, I see little benefit with using stainless bolts, rather then plated grade 5 bolts. The disadvantage to stainless is that what you buy at your local Home Depot will not be as strong as grade 5. You can buy strong but expensive stainless bolts on line like Don did.

Re: BULK HEAD -front- 2 box beams

Reply #10 – June 04, 2016, 05:01:45 pm

Thanks Wyatt,
"You could also use a 1 3/8 hole saw to make an access hole where the end of the Rook bolt is"
I'm not sure if I follow you on this.
The Rolok bolt terminates inside of one of the box beams, I don't know if its the first box beam or inside of the second box beam.
I don't think you meant to drill a 1 3/8" hole in the 1 1/2" box beam to gain access to the broken end of the Rolok bolt.

The Rolok bolt is hardened, Is penetrating it with a drill bit easier than drilling a new 3/8" hole between the broken bolts all the way through the angle iron and the 2 box beams?
Is there additional details on the drill bit you used?

I did not find it too difficult to drill new holes for the through bolts in the rear bulk head. It would be preferable to use existing holes rather than adding more holes in the box beam.

I think 3/8" zinc plated grade 5 bolts will work well.

Re: BULK HEAD -front- 2 box beams

Reply #11 – June 04, 2016, 05:59:13 pm

Lon,
The Roloks are 2.5" long and so terminate in the middle of the second box beam. If you were to use a hole saw from behind the second box beam in line with a given Rolok, you would be looking at the end of the Rolok (it is tapered to a blunt point, threaded to the end). You could potentially double nut it from there after using some penetrating oil, but no guarantee that it would work. If you wanted to do that, I would start with a 1 & ⅛" hole saw. Judging from the rolled edges, both of those box beams are 11 gauge .125" or ⅛" thick walled tubing, so you would want your hole not to touch the horizontal walls of the tubing. After removing the broken Rolok, you could then use the long through bolt and a ¼" X 1.5" X 2" flat stock to make a load bearing surface that spans the hole and overlaps it on each side to transfer the load to the horizontal walls. If double nutting didn't work, you could weld a nut from the access hole (I had to weld nuts onto all but one of my Roloks to remove them). Not an easy job, depending on skill level and physical flexibility, but potentially doable.
Don

Quote from: Lon and Cheryl – June 04, 2016, 05:01:45 pm

Thanks Wyatt,
"You could also use a 1 3/8 hole saw to make an access hole where the end of the Rook bolt is"
I'm not sure if I follow you on this.
The Rolok bolt terminates inside of one of the box beams, I don't know if its the first box beam or inside of the second box beam.
I don't think you meant to drill a 1 3/8" hole in the 1 1/2" box beam to gain access to the broken end of the Rolok bolt.

The Rolok bolt is hardened, Is penetrating it with a drill bit easier than drilling a new 3/8" hole between the broken bolts all the way through the angle iron and the 2 box beams?
Is there additional details on the drill bit you used?

I did not find it too difficult to drill new holes for the through bolts in the rear bulk head. It would be preferable to use existing holes rather than adding more holes in the box beam.

I think 3/8" zinc plated grade 5 bolts will work well.

Re: BULK HEAD -front- 2 box beams

Reply #12 – June 04, 2016, 06:15:11 pm

I would probably prefer to not weaken the second box beam by drilling so many large holes in it. Attempting to drill the broken Roloks out from the front seems to be a better bet. If that fails a new 3/8" hole.
Do you agree?

Re: BULK HEAD -front- 2 box beams

Reply #13 – June 05, 2016, 06:11:12 pm

I did mean to drill 1 3/8 holes in the second square tube, being careful to get right in the centre of the tube and not cut into the front or back sidewalls. I believe the double tubes in the front bulkhead are required to support the weight of the propane/diesel tanks, so I would attempt to easy out the bolts before drilling. I noticed in the pictures you published that you have removed the lower fiberglas skin and have access to both tubes, so you could drill a smaller hole in the side (vertical wall) of the second tube where a longer Rolok would have exited. You may have difficulty getting lined up on the Rolok bolts because they are not always installed perpendicular to the tubes.

I did read in a post years ago that someone thought that the Rolok was so hard that it could not drilled. This believe has some truth to it, however, the Rolok is surface hardened with a softer core which can be drilled with a hard bit. With the head broken off, you will be drilling into the softer core. Attempting to drill through the threads of the bolt would be much more difficult.

I also noticed that your front bulkhead was more damaged then mine and wonder if your motorhome was driven on salted roads during winter months.

Re: BULK HEAD -front- 2 box beams

Reply #14 – June 05, 2016, 11:35:39 pm

Wyatt,
If the inner square tubing is as I suspect, 11 gauge, a 1 ⅜" hole would cut the horizontal walls because the open space in the center of the tubing in 11 gauge tubing is only an inch and a quarter in 1.5" square tubing. If it is 16 or 18 gauge tubing like everything else in the basement framing of our coach (a 99'), then a perfectly centered hole would clear the top and bottom walls of the tubing. The reason I think it is 11 gauge (⅛" thick wall) from looking at the pictures, is the apparent radius on the corners. The thinner square tubing between the bulkhead transverse frame members on our coach have a noticeably tighter radius on the corners. In any case, most hole saws that I have used have a tendency to wander a bit, especially when worn, and makes an accurately sized hole somewhat unlikely. So, I would proceed with caution and undersize the hole a bit to be on the safe side. The hole could always be enlarged by a die grinder later if necessary. Just my two cents, adjusted for inflation...
Don

Quote from: P. Wyatt Sabourin – June 05, 2016, 06:11:12 pm

I did mean to drill 1 3/8 holes in the second square tube, being careful to get right in the centre of the tube and not cut into the front or back sidewalls. I believe the double tubes in the front bulkhead are required to support the weight of the propane/diesel tanks, so I would attempt to easy out the bolts before drilling. I noticed in the pictures you published that you have removed the lower fiberglas skin and have access to both tubes, so you could drill a smaller hole in the side (vertical wall) of the second tube where a longer Rolok would have exited. You may have difficulty getting lined up on the Rolok bolts because they are not always installed perpendicular to the tubes.

I did read in a post years ago that someone thought that the Rolok was so hard that it could not drilled. This believe has some truth to it, however, the Rolok is surface hardened with a softer core which can be drilled with a hard bit. With the head broken off, you will be drilling into the softer core. Attempting to drill through the threads of the bolt would be much more difficult.

I also noticed that your front bulkhead was more damaged then mine and wonder if your motorhome was driven on salted roads during winter months.

Re: BULK HEAD -front- 2 box beams

Reply #15 – June 06, 2016, 12:00:44 am

What would be the problem with drilling new holes spaced between the original holes through both tubes and use through bolts? It seems that there is enough distance between the rolocks to not weaken the tubing. The only issue would be to not drill into the perpendicular tubing, but since it is exposed that would be no problem.

Re: BULK HEAD -front- 2 box beams

Reply #16 – June 06, 2016, 01:50:53 pm

Wyatt,
The previous owner bought it new. He lived in Alabama. Drove it around that area of the country servicing his insurance clients, he never used it for camping.
I never drive it in winter or after the first salting of the roads.

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BULK HEAD -front- 2 box beams

June 02, 2016, 10:29:57 pm

Re: BULK HEAD -front- 2 box beams

Reply #1 – June 02, 2016, 11:36:30 pm

Re: BULK HEAD -front- 2 box beams

Reply #2 – June 03, 2016, 01:43:31 pm

Re: BULK HEAD -front- 2 box beams

Reply #3 – June 03, 2016, 02:21:59 pm

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Reply #4 – June 03, 2016, 02:30:21 pm

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Reply #5 – June 03, 2016, 02:33:17 pm

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Reply #6 – June 03, 2016, 05:10:05 pm

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Reply #7 – June 03, 2016, 05:55:28 pm

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Reply #8 – June 03, 2016, 11:05:51 pm

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Reply #9 – June 04, 2016, 01:28:21 pm

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Reply #10 – June 04, 2016, 05:01:45 pm

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Reply #11 – June 04, 2016, 05:59:13 pm

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Reply #12 – June 04, 2016, 06:15:11 pm

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Reply #13 – June 05, 2016, 06:11:12 pm

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Reply #14 – June 05, 2016, 11:35:39 pm

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Reply #15 – June 06, 2016, 12:00:44 am

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Reply #16 – June 06, 2016, 01:50:53 pm

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