A Winter Project - Slide Opening, Frame Repair (Picture heavy)

[jim44646]

John

I've been viewing your post on bending frame. Have you given any consideration to your tool box and the weight you are carrying in it hanging off the back of your frame.

 

[JohnGB]

Hi Jim,

The rear boxes, yes I revisited those early in my investigation. There is added weight there, but we need to keep it in context. The question is, is the added weight of the rear boxes that much different then weights inside the camper of other floor plans and was the weight in the rear boxes enough to be the cause of the problem?

Here is the quick answer, from my review I have come to the conclusion that, no, the added weight was not the smoking gun to cause the problem. Yes, there is weight there, but not enough to be the root cause of the problem.

Some of the background:

The T310SR is a 32 ft, 10,000# GVWR rated camper. The rear boxes make it 33' 6". From the Sunline weight sticker in the camper, the camper weighed 7,142# when it left Sunline. This leaves 2,858# cargo capacity. That is a good amount of cargo capacity and over the years I have managed to use it all when I need to haul fresh water to camp.

Next comes, where can the weight be added to the floor plan? Here is the floor plan, a rear living camper.

That rear living floor plan has a majority of the cargo capacity over the axles and in front of the axles. There is not as much storage behind the axles to help offset the front area weights. This loading effect creates the high tongue weights of the rear living floor plans with the position of the axles. The T2499 is the same rear living floor plan, just smaller and it too has the same characteristics. (I had one of them and same issues) My T310SR has a 1,600# loaded tongue weight when I am totally filled to 9,950# of GVW with water. That is 16% tongue weight. And this is with the rear boxes helping to offset some of that TW.

When Sunline was still in business and I had my T2499, I found out this same high tongue weight issue. It also lead me to trading in a really good 1500 Tahoe for a K2500 Suburban to tow the T2499 due to the high loaded TW. Once I figured out the issue, I wrote Sunline a multi page letter explaining my findings and how can I ever load this floor plan to use all the cargo capacity and not have extreme TW? I proposed my plan to add the rear boxes to that camper, still under warranty, to reduce the 22% loaded tongue weight down to 15% loaded TW. They reviewed the plans and granted me permission to do so. It was unique to this situation and this camper floor plan. It would not work on other floor plans. When I bought the T310SR I predicted the same issue and the same problem came. I then moved the rear boxes to the T310SR.

The rear aluminum boxes, the frame under it and all the cargo inside, had a max set limit of 350#. I only have 300# loaded in them. And I removed the rear tire from the bumper (~ 50#) So this 250# added to the back of the camper is split between 2 frame rails. This comes out to 125 to 150# added to the slide side frame rail of the camper 1 foot behind the rear wall. So the question now is, is 150# enough to damage a 10,000# rated camper frame? Is this 150# at it's location that much different then other floor plans that have more weight on the rear wall then this?

Using some of our own Sunline campers, here are some floor plans with the length and weight at the rear of the camper which are capable of being loaded with cargo higher then mine even with the rear boxes. These TT's are all 10,000# GVWR Sunnies on the same 10" frame.

2004, T330SR, 34' 6" Rear bedroom slide behind the axles
2004, T320SR, 33' 2" Rear bunks and bath
2004, T317SR, 31' 6" Rear bunks with super slide behind the axles
2004, T299SR, 30' 10" With option of rear bedroom slide behind the axles.

On the Sunline 5th wheels on the same 10" frame,
2004, 12,500 GVWR, F304SR, 31' 11", Rear kitchen, with super slide behind the axles
2004, 12,000# GVWR, F297SR, 31', 10", Rear bath, bunks partial rear slide behind the axles and partial kitchen behind the axles.
2004, 12,000# GVWR, F281SR, 29' 11", Rear kitchen, rear super slide very far behind rear axles.

These are just some of the long campers with floor plans that have cargo space to allow more weight behind the axles then the T310SR. The rear kitchen models have the ability to be a lot higher then the rear living floor plan. All of that kitchen is on the back wall.

Doing the stress calculations on this 10" I beam frame, there is a lot of excess capacity on the frame rails when the camper is standing still. The issue is, towing down the road. That dynamic bounce of a pot hole can be many times worse then the static standing still loads. The unknown is, what was the original design assumptions of all campers using this 10" frame rail? The RV industry on large campers uses a lot of this 10" I beam and on campers many feet longer and heavier then mine. The 10" I beam Sunline picked is heavier then many on the market today as they do offer it in at least 2 different flange sizes.

Bottom line, the extra 125 to 150# I added to the slide side frame rail was not the root cause to create the bent frame from what I have found. I feel it would of happened just the same without the rear boxes. My luck.... bad luck that is... I found the edge of the towing dynamic loads that can cause the frame rail to bend. That 15 mile section of I-88 in NY during the summer of 2010 did me no good....

I have more info if wanted on this. I was challenging myself several times and just could not see the rear boxes making a difference. The amount of added weight is not enough.

Thoughts? Again always open minded to make sure I did not miss anything.

Thanks

John

 

[JohnGB]

Hi again Jim,

I was asked your same question by a few of my good friends, so I put the numbers to what this means to help explain it to them better. Here is a recap. Again, I'm open minded and will listen to what anyone has to say. It helps me re-think through through this to make sure I did not miss something.

To add to the above post on how I came to the conclusion that the rear boxes where not the smoking gun to bend my frame, here are some of the calculations results in relation to the weights (forces) on the camper slide side frame rail. Obviously whatever road bumps I hit, they were large enough or repeated enough, to bend the frame rail initially.

My camper being a rear living floor plan does not have a lot of internal camper items at the back of the camper like a rear kitchen floor plan would or super slide along with a rear bunk slide etc. But everything is weight and how far back from the rear spring hanger the weight is, created the forces that the frame has to hold.

The camper frame behind the rear axle hanger bracket is what we call an overhung load or a cantilevered beam. The weight supported by the frame rail is acting as a force on the frame which is mimicked as a long lever creating a mechanical advantage trying to bend at the rear hanger. If the frame is strong enough, it just resists the weight and the frame springs back to the original shape when the weight (force) is removed. We call this type of stress, the elastic range of the steel and it will return to the original shape when the force is removed. If the force reaches what we call the “yield” point of the steel and beyond, the frame will then permanently bend and not return to the original shape. (we call this the plastic range)

All weight (force) behind the rear axle spring hanger creates a torque (force x distance) on the frame rail with the weakest area being just aft of the rear spring hanger. This is the area of the lower flange on my camper that buckled. All of the weight of the camper and cargo in it, make up the many forces the frame has to withstand. If we look at each of the areas of the camper and what torque they create on the frame rail, we can see the relationship of what each area of the camper has in relation to one another. Here goes…

I'll "attempt" to summarize this and make it shorter...

Using high strength low carbon steel, (A529-50) the frame metal has a yield strength of a minimum of 50,000 psi. The dimensions of the 10” x 9 lb/ft thin I beam frame rail creates a moment of inertia of 35.5 in^4. By calculating the bending stress required to “start” the frame to bend (the yield point), this comes out to be a torque of 355,000 in. lb. (29,583 ft. lb). Note: This value is for only the slide side frame rail of the camper. The door side frame rail also has the same torque limit of 355,000 in. lb.

This torque limit of 355,000 in. lb. on the slide side frame rail translates into, 3,489 lb. of a single raw weight (call it 3,500 lb. of point load force) at a distance of 102" (102" is the rear wall of my camper). If we go above that torque limit of 355,000 in. lb in any combination, either one single 3,500 lb. weight or many smaller weights at different distances which are overhung from the rear frame hanger, we can bend the frame. I managed to hit this limit...and go above it.

Armed with this data, I know what range of force it takes to bend the slide side frame rail. Let's look at the normal loads on the slide side frame rail and what torque moment each of these loads (forces) create. These forces are for only half the camper, starting at the center-line of the camper all the way to the slide side wall and starting from the rear spring hanger to the end of the camper.

Here is a chart of the weights in the camper and the location of them behind the rear axle hanger. Some of these are from actual measured data from my force jack, others are truck scale weights and some are accumulative estimations but adding up parts of the camper. They do all align and agree with each other and at this point I feel they are accurate enough to tell us what is going on.

Back ground info on the camper: (fully loaded with fresh water and WD engaged.)

• 1,600# tongue weight
• 4,340# front axle (the weight distribution hitch force lands mainly on the front axle and the fresh tank is over the front axle)
• 4,040# rear axle

----------
9,980# GVW. My GVWR is 10,000# So I'm at the limit when I haul my 42 gallons of fresh water and we do often.

Normal frame loads, (slide frame rail side):

• Rear cargo box: 150# at 111" = 16,650 in lb. of torque (point load)
• Rear slide arm holding the back of the slide: 600# x 58.5" = 35,100 in lb (point load)
• Rear wall, slide side wall and roof loads of the camper acting on the rear wall: 380# at 102" = 38,760 in lb (combo of point loads and equally distributed loads)
• Camper cargo, floor structure loads and the steel frame itself: 477# at 51" = 24,327 in lb (combo of point loads and equally distributed loads)

Summary:

• Total weight of the slide half of the camper behind the rear hanger. 1,607 lb.
• Total torque from normal loads on the frame rail in the area behind the rear hanger: 114,837 in. lb. (when the camper is standing still)

• The total torque from normal loads is 32% of 355,000 in. lb. of torque needed to reach a yield failure.
• The rear boxes are 14.5% of the 114,837 in lb. of the normal torque loads.
• The rear boxes are 4.7% of the 355,000 in. lb torque to reach a yield failure.
• The rear boxes are 9.3% of the total weight of the slide side half of the camper.

There is 68% more frame strength statically, (when “not” towing) before the frame will reach yield. If I took the rear cargo boxes off, I would have 72.7% more frame strength before we reach yield. Bottom line, the rear boxes are only 5% of the problem the frame bent.

While the boxes are at the back end of the camper, the other loads already in place are still much larger in comparison. If there is only 5% safety factor in this frame, there is not enough...

To give a real comparison on something which may be easier to relate too, if a 230 lb. guy was sitting in the swivel rocking chair at the back wall, 102”, his weight would create a torque of 230 x 102 = 23,640 in. lb. The 230 lb. guy is 30% worse on the frame than the 150 lb. of rear cargo boxes at 16,650 in lb. of torque. The frame it not that fragile.

The dynamic towing loads created forces above the 68% excess frame capacity when standing still. I still suspect the 15 miles of pot hole central on I-88 in lower NYS started this issue. A true learning for me and hopefully others about the damage that can some from this. If I would of checked my frame for any buckling after that trip, I may have been able to reinforce the frame at the first sign of the buckling and stopped this problem from advancing. Chalk it up to experience at this point.

Remember I have a rear living floor plan. They do make rear kitchen layouts which are heavier at my length and some longer than my camper. The rear living floor plan is one of the lighter back end campers. They can have very tongue weight up front, but the back is lighter in relation.

Glad to explain this more if you see something I may have missed.

Thanks

John

 

[justatourist]

Hi JohnB.


So many details to consider, whew! I think the difference between the kitchen side and those cabinet re-enforcements must have helped that side last longer than the slide side without internal reinforcement of cabinets but the added stress of the slide banging the frame. Even if only from a inch away. That slide side has surely taken a beating at or above designed limits.


About the repair, I would add some welds in the frame saw cut. Not a full re-weld of the saw cut but some one inch welds to fill the gap and then grind the weld flat. this should take some stress when loads try to close that cut.


Since repair seems to be going along quickly you probably have it all together and painted by now.


one thing is for sure and that is that after your patch you can not worry about pot holes anymore. Well, not about them bending the frame. How about re-enforcing those axles, LOLOL!


How many bolts? Placement? Close to cut and ends and between?










What does the weight of reinforcing metal make?








Great job!

 

[JohnGB]

Hi Jim,

Thanks for the good words. Much appreciated. To your questions,

Hi JohnB.

So many details to consider, whew! I think the difference between the kitchen side and those cabinet re-enforcements must have helped that side last longer than the slide side without internal reinforcement of cabinets but the added stress of the slide banging the frame. Even if only from a inch away. That slide side has surely taken a beating at or above designed limits.

About the repair, I would add some welds in the frame saw cut. Not a full re-weld of the saw cut but some one inch welds to fill the gap and then grind the weld flat. this should take some stress when loads try to close that cut.

How many bolts? Placement? Close to cut and ends and between?

What does the weight of reinforcing metal make?

The saw cut area, yes I intended to weld that area. I made this statement back on reply no 39 on the "fix it" plan http://www.sunlineclub.com/forums/f...-repair-picture-heavy-17444-3.html#post135473

Two formed angle plates will be added across the saw cut area. The saw cut will be ground for a full penetration weld prep. The inside plate will be added and partly bolted to the main frame rail at this point. Once the inside plate is in place, a vertical weld using 70ksi weld rod will be made up the saw cut line. This weld will attach to the inside plate and the 2 beam sections. The weld will then be ground and polished to remove stress risers. The weld area will be primed and painted to prevent rust between the plates.

I was intending to fully weld that saw cut joint, not stitch weld it. And then grind and polish the weld smooth. The thought process was, since this is an I beam and the way it is being used on the camper (cantilevered beam), the top part of the I beam from the center to the top is in tension most of the time and the bottom, center to the lower flange is in compression most of the time. If the beam flexes it will pull on the saw cut welded area and that area "I felt" needed to bend uniform across the entire cut area. If I stitch welded it, there would be interrupted stress during the bending. My belief is that interrupted stress could start a crack running faster then having the full length weld. Again, in this case at that area.

Keeping the welding in mind and the side effects of the heat induced, this needs to, has to, be done in multiple passes. I will let is cool back down to the touch between passes to help keep the heat as low as it can be.

What was your thoughts for stitch welding? I'm assuming heat concerns.

The bolts, there are many of them. 26 per side of the saw cut totaling 52 of them spread out along the 60" length. Since there are plates on both sides, and the original beam is in the center, this is a double shear setup which helps add safety factor. I'm not trying to cheap out on the bolts.

This joint is different then the standard joining of 2 I beams with the intent that the joint is strong enough to cover the size of the beam. In this case, I am creating the beam joint and increasing the strength of the original I beam across this entire area. Due to this, I have spread out the bolts over the full area.

It was hard to get a clear image to fit on the screen, but this should give you an idea of what I'm doing. The red phantom line in the middle is the saw cut area.

Here is the entire outside splice plate

Here is a closer view of one end.

And a black and white image

The weight of the slide side added steel totals 125 lbs. 68 lb. are the 2 splice plates fixing the bent area and 57 lb. is the lower flange reinforcement to prevent future problems. The original I beam steel weight for this length of reinforcement is just under 100 lb. as a comparison.

I could of reduced some more of this weight and I did from the first concept. However I had concerns of the new rigid sections of the frame joining back to the original and if I stopped that short, I may move the problem to that new location of very strong back to original. So I reinforced the full length of the lower flange to slow down the entire frame deflection of the over hung area. Adding the 50 lb of extra steel to help ward off that problem is better then it failing again.

The splice plates have a shape change at both ends to lower the strength zone of the splice plate before going back to the original. If you look at the splice plates drawing, the last 6" has no top flange. Having no top flange in that 6" reduces the strength.

I am going to have to remove a few items (approx 60 lb.) from the camper with this added weight to stay under the 10,000 lb GVWR, but only if I have to carry full fresh water. This will not be that hard to do. We are only at full weight on long camping trips. My full fresh water accounts for 350 lb. of cargo weight.

Thanks

John

 

[justatourist]

Hello JohnB. I must have missed the stitch-weld. My bad. One thing looks for sure and that is lots of miles on that unit.

 

[JohnGB]

Progress has slowed, but moving forward and I learned some new things.

New Learning:

After digging some more, I ran into an RV tech who has seen similar bent frame issues. However most of them had been on fairly new campers and still under warranty. (Not Sunline, other brands) Most of these bent in the area where the slide arm came through the frame hole when the hole was behind the rear axle hanger. In my case, this is not a problem and Sunline added a reinforcing plate around both slide holes.

The RV Tech suggested I contact Lippert and see what they can offer. They have mobile field crews who do the warranty repairs. So I called LCI Tech Service in Elkhart and explained my situation.

It was a really good call and I felt the guy in chassis tech service had been around a while by the conversion. I asked about the method they would use on how they would fix this and if I can hire their mobile crew?

On the fix, he asked if I could jack the frame straight. I told him I could. It takes 2,300# of lift force at the back of the frame and 3" of lift to bring the frame rail back to straight. But I'm also lifting a good amount of the camper off the ground while I'm doing this as shown by the tire contact patch changing so much. I'm almost having the rear tire lift off.

He said that is part of what they would do. They would jack the frame back to straight and then weld on reinforcements on the bottom flange area to hold it in place. They may go a little higher lift to create some excess lift so when they lower the camper any frame flex will be closer to where it needs to be. I asked, what about all that beam stress built up from the original bend and now this 2,300# of up loading adds more bending stress? He said, that is a risk and they would not know if that is a problem or not. In their defense, they have not done any calculations on this and this was a quick phone call. I was glad they helped as they could.

I asked on the mobile crew cost and I understand what field service rates are. It is about 6 hours from Elkhart to my area and the field team most likely would come from there. He did not know the rates and switched me to the field service group. I was going to ask them the same questions on how they would do the repair and an estimate on the cost. I have 3 calls/voice mails into the field service person and they have not returned my call and after a week of waiting, I not expecting they are going to call.

New Method of Measuring:

Getting ready for the Lippert call, I measured the frame differently than the 2,300# and 3” of lift to bring the frame back to straight. I pulled a long string starting 1 foot ahead of the front axle hanger and all the way to the back of the camper. The axle area of the frame is very straight and I sighted the line off this straight area and projected it to the back of the camper. Here you can see this.

Looking down the line in relation to the frame. You can see the yellow line start to bend downhill past the rear hanger.

And at the end of the frame the distance. 1 3/16” This is the amount of downward bend.

Now to, Why is it 3” when I jack up the back of the camper to get a straight frame verses a bend downhill of 1 3/16”?

The 1 3/16 is the raw amount the frame rail is bent. The 3” and 2,300# of jack force up at the back of the camper to get a straight frame takes into account the weight of the camper pushing down on the frame rail and the frame rail bending in relation to that weight. The whole side of the camper is lifting, even forward of the axles. It creates a straight frame. Learning this, it gives me a good heads up when I saw cut the frame at the bend area, I will most likely only need to lift the back end in the approx. 1 3/16 to 1 1/4” range and the bottom of the frame should come close to straight. I will not know for sure until I do it, but this is a good start.

I am moving forward with my correction method as I feel it is the best long term approach. The LCI method of jacking the frame straight and then welding on reinforcements creates more unknowns then I have now. Yes, their approach is quicker and easier, but it will leave almost 2X the amount of normal bending stress trapped in the frame from jacking the camper to create a straight frame. This stress works against the welds of the lower flange reinforcement which are there to strengthen the frame for future pothole/bump events. I cannot see long term good coming from this approach. The beam cut and straighten method relieves all the bending stress, adds some weld stress but lower flange reinforcement has full strength.

The fab shop now has the A572-50 steel plate. It was too complex to get flat bar stock so we are cutting strip from plate to create the flat bar stock for the lower flange reinforcement. A 60” wide by 120” long sheet is at that shop and this week they should be able to start shearing, water jet cutting out the splice plates and holes, bending the formed angle on the splice plates and shearing and roll straightening the sheared strips. With some luck, I might have parts late this week early next week.

In the mean time I have been dealing with the frame rust coatings and straightening out the bent flanges. First was to prime the frame after the rust conversion treatment process. I used Rust-O-leum Professional Clean Metal primer. It’s all white now.

Then to straighten the bent flanges. I jacked the back of the camper up until the frame came straight and went 1” more to put the lower flange in tension. Then a 24” crescent wrench and the flanges went back to straight real easy.

Today I finished the black top coat of Rust-O-leum Professional Black paint. The green masking tape is over the areas I will be welding to the original beam. It will be less grinding off the paint prepping for the welding when the time comes.

The inside door side.

The inside slide side

The outside slide side

In comparison, the frame use to look like this

This 3 coat process will hopefully last a good long time. I have the front half of the camper yet to do….

All for now. Thanks for looking.

John

 

[JohnGB]

I picked up my steel parts today. The fab shop did a really good job on them. Due to not being able to find the right grade of steel in flat bar short of buying a mill run worth, we sheared strips from plate. The plate is 7 gage (3/16”) thick so the flat strips ended up being 3/16 in place of 1/4”. I had to tweak the sizes to create the right area moment of inertia to make up for the lost thickness but it all worked out OK.

Here are the parts.

I have the splice plates just clamped together with a spacer to see if they line up right. They do. And all the holes are dead on.

The inside splice plate to work around the enclosed tank compartment and the 2 x 2 frame cross member.

And the outside plate

These parts where water jet cut. They use real high water pressure with a very fine abrasive (sand) and it cuts steel. This shops machine can do very thin sheet metal to 6” thick plate. All CNC computer controlled and extremely accurate. The holes are within 0.005” of true position and diameter at fab shop pricing verses machine shop. This technology and now lazer cutting has taken over the metal fabrication industry. It came on the scene about 15 years ago starting to be popular and within the last 10 years, has sort of taken over how weld shops work. They can make precision cut parts that cookie cutter fits exactly together and then just the weld them in place. Welded parts made very accurate with a lot less time and more creativity for the designer.

There are some differences to understand over older traditional methods. They make exact 90 degree corners/edges. Lazer with it's fine burn edge is worse than water jet. In a bending fatigue situation those exact 90 degree knife sharp edges are a problem. So you need to grind/sand all edges and countersink all holes to buff that death defying sharp edge off.

Here is a water jet hole.

A counter sink quickly cleans this up to a nice chamfered entry. And cleaned up ready to go

I did a test fit that it fits in the frame correctly. It does. Lines up as planned.

And the parts primed. Since these parts will be welded/bolted and the inside of the parts trapped between the beam, I need to paint them for corrosion resistance first before assembling. I have to deal with grinding off the paint at the weld areas but a wire wheel on the 4 1/2” grinder takes paint off in an instant so no problem there.

The next 10 days are supposed to be unseasonably warm, in the 50’s and 60’s so I will try and take advantage of those nice temps and get this painting cleaned up and the plates and lower flange reinforcement on.

More in the next few days.

Thanks

John

 

[JohnGB]

Some more progress.

I test fit the inside splice plate as I have to deal with the 2 x 2 cross tube by the rear axle hangers. And I have to be able to get the plate into this area. I had to trim out one of the thin frame cross members to allow the splice plate top flange to fit. I will repair this thin frame cross member once the splice plate is in its final location. I also needed to remove the square drive shaft from the slide gearing. It came out amazingly easy. I also learned the square tube on mine unit has an inner and outer square shaft. They telescope inside each other. They will for sure get greased on the inner shaft part when I put them back together. I can see these easily getting rusted solid.

The plate went right in surprisingly easy.

The inner splice plate, primed and tested for fit

View showing the frame cross member clearance needed. Look up by the wire bundle for the top flange clearance. I only trimmed one leg of the frame cross member. The top leg is still welded to the frame.

The 2 x 2 frame cross member clearance.

The 2 piece slide square drive shaft.

I top coated all the parts black. Masking taped off the weld area.

Today I started getting ready to cut the frame in the bend area. Jacks, stands and large angle iron cross brace added.

I also needed to precisely align the splice plates so the inside plate holes line up with the outside plate holes, all 52 holes. I needed to create 4, 1/4” spacer blocks so they would be the same exact height above the lower flange. Ground a heavy chamfer on the spacer to go over the 1/4” I beam flange radius.

Then I drilled 4 bolt holes in the I beam on the axle area side of the bend zone as this side of the I beam cut line is straight. The rear side of the I beam cut line is heading down hill and will move up to create a straight frame rail when I jack up the back of the camper after cutting. These 4 bolts will allow me take off the outside and inside plates and when I put them back on, these 4 holes now in the frame will line them right back up. I did not want to drill many more as there will be a level of weld shrink in the I beam that can distort the hole position when welding the saw cut web. Especially near the saw cut weld area. I now have 4 holes in, only 48 more to go, later… My body is sore from getting under and back out from under the camper so much. Not as young as I use to be...

The support setup ready for the cutting of the I beam step. This also hard to see, but the outside splice plate is on. Black on black is hard to see in pics.

Here you can see the 4 bolts on the outside splice plate with the 1/4" spacer block vise grip clamped to the lower flange. When the bolts go in permanently, the nuts and lock washers will be on the inside of the frame and not collect road crud on the threads. The nuts are on the outside just for easier setup. This high strength low carbon steel drills fairly easy. I'm using 3 steps in drill bit size to get to 1/2" holes. Also using cobalt bits for the first 2 sizes and standard high speed steel on the 1/2". The bits being sharp are the key to this going easy.

The inside plate with the 4 bolts in it and the same 1/4" spacer blocks in place on the lower flange

Again hard to see, black on black

The bolted area

The next few days and I will be well into the frame repair. The saw cut and weld up of the saw cut will be the next step.

All for today

Thanks

John

 

[Tweety]

WOW....I need to show Mr Tweety these pics. I can't follow it all, but it sure seems like a good thing you're retired! What a project! Gotta keep that Sunline going. When we nose around at new RVs we always come back to saying "it's a shame Sunline isn't still around." Camping season is just around the corner!

 

[JohnGB]

WOW....I need to show Mr Tweety these pics. I can't follow it all, but it sure seems like a good thing you're retired! What a project! Gotta keep that Sunline going. When we nose around at new RVs we always come back to saying "it's a shame Sunline isn't still around." Camping season is just around the corner!

Hi Pam, Thanks for looking. I'm drill'in holes today.... will have some more progress up within the next few days.

And yes, it is a shame Sunline is no longer. If they where, odds are high we would of ordered a custom one by now. For now, we will keep this one. A lot of camping in it yet to do!

The retired part, yes, it is nice! I tell Cindy, I'm heading to the barn. She says, "Oh going to your office today"....

The weather up here has been very unbelievable for mid February. Been 50 to 60 for the last five days and suppose to maybe hit 73 on Friday... I'm sure winter will be back...

Thanks

John

 

[Mrtweety]

John,

I actually re-joined the forum so I can follow this as only Pam could see it before. This is truly a beautiful repair. The water jet holes are gorgeous. When I look at the actual sister plates it strikes me that due to some structural features the bent flange area actually appears not continuous but is broken or comes short of spanning the entire length. Interesting to me in that as you know I was a fan of the flat plate option just since it was simpler. But I know the flange adds inertia for the piece where it is present and you have such a great vendor who fabricates this stuff.

Curious for my future reference -- What exactly is the wire brush you use to remove the rust so well?? I may need one of these.

The paint looks great and there is no doubt at all that this repair is completely solid and will eliminate the problem. I am very impressed and entertained by this. Great work !!

Steve ( Mr Tweety)

 

[Mrtweety]

Upon closer inspection it appears you trimmed the cross member to allow the bent flange to be continuous -- so it is not compromised. The absence of it at the ends will not matter much. Lovely ....

 

[JohnGB]

Curious for my future reference -- What exactly is the wire brush you use to remove the rust so well?? I may need one of these.

Steve ( Mr Tweety)

Hi Steve,

Yes, the fab shop and that water jet did a great job on the parts. All 54 holes were dead on within 0.005" of true position. They all lined up exactly. This shop has done a lot of jobs for me a whole lot more complex then these for work. A good shop at fair prices.

The splice plates have added a good amount of strength in the saw cut area. When I go to lift the frame at that area, the whole side of the camper now lifts with the jack from the start. Before, the back would sag, the wheel area would sag, and it would grunt and then go up.

I have a bunch more to post up yet and will soon. I'm now in the final fitting of the lower flange reinforcement steel and then to start that welding process. A task in itself to control distortion.

To your questions above, I have several attachments for the 4 1/2 grinder that eat through rust in short order.

2 of them are knotted wire brush wheels.

Here is one of them. This is good for large areas to buff off

Here is a link, they sell these on many brands and most places that sell the grinder
https://www.amazon.com/DEWALT-DW491...0019&sr=8-1&keywords=Angle+Grinder+Wire+Brush

I also use this one, which is good for crevices, or tight spots and knocking out slag from a weld joint. This one works more 90 degrees to the cup one up linked above which is more flat face used
https://www.amazon.com/DEWALT-DW493...0019&sr=8-2&keywords=Angle+Grinder+Wire+Brush

And they there are the abrasive flapper wheel disks. These come in all kinds of grit and they cut, so make sure you hold it or you will be through something real thin, real quick. You can see on the end of the grinder

Amazon.com

And some times these come in handy too. Flapper wheels. Think stiff emery cloth on a wheel. They have a 1/4" shank that you can put in a drill motor or die grinder

There are lots of brands and grits. Here is a hit off Amazon
https://www.amazon.com/Shank-Mounte...fkmr0&keywords=flapper+wheels+for+die+grinder

Thanks

John

 

[JohnGB]

Upon closer inspection it appears you trimmed the cross member to allow the bent flange to be continuous -- so it is not compromised. The absence of it at the ends will not matter much. Lovely ....

The cross support is a Z shape. The top is coped out and a tab of the very top of the Z is welded on top of the top flange of the I beam. This Z shape is only 1/16" thick sheet metal formed up.

I trimmed the vertical leg and left the top horizontal leg intact welded to the top flange. I trimmed it this way to not compromise the formed angle leg at the top of the splice plate which is taking a lot more load then the cross member.

The plan is, to repair the Z shape and weld the repair piece back to the splice plate creating the same strength cross support as was there originally.

Thanks

John

 

[JohnGB]

Picking up where I last left off, the splice plates had a small amount of holes and bolts added to the axle area side of the saw cut line. The inside splice plate will act as a filler plate for the saw cut weld so I needed to align the plates and hold one half in place during welding.

Next was the saw cut itself. Here you can see the cut area marked out.

A scribed line for the cut from the bottom to the stop drill hole.

Next was to do the cut. I’ll pass along the blade I used to cut this higher strength steel with. I was going to look into carbide tipped blade but did not need to go that far. These blades work well in tough applications of mild steel. The finer teeth also help make it not jump much at all.

Here is the start of the cut, the lower flange. This took about 3 to 5 minutes if that.

You can also notice the bottle jack and jack stand next to the cut line. There is also a bottle jack at the end of the camper. As the cut progresses, there is a need to tweak the beam up at the end of the frame slightly to not bind the blade. In less than 10 minutes later the cut was completed.

Then to jack the back of the frame to create a positive uphill lift to the beam where the prior bend was. To track the distance, a dial indicator is placed across the lower part of the cut line

I raised the back of the camper until a string line along the bottom flange came straight and I went and extra 3/8”. A jack was in the back lifting the frame. This created a gap at the bottom of 0.115” or little less than 1/8”. That is not a lot but you can see by that little bit, the back of the camper being 105” inches away it does not take much bend to create the problem with the slide opening.

I am using E7018AC weld rods. This is my first time using this rod so I practiced on some test metal for uphill welding and they weld good. I had no issue weave filling a wide gap. I also had to get the rods baked (heat reconditioning) as moisture from lack of a hermetically sealed can packaging at the store gets moisture in the flux and you have to recondition the rods before use. This is not a big deal, it is standard practice and it just needs to be done.

7018 weld rod needs clean metal. It creates a lot of porosity (holes in the weld) if there is contamination from paint or rust. I even ground off the mill scale to make this the best shot I could. Here is the filler plate prep

The plate now will bolt onto the inside of the frame.

Since my joint was only a little over 1/8” I had a choice of opening up wider to make the weld rod weave easier or just chamfer it and put a stringer weld up it. I chose the stringer route as the wider groove would mean more heat into this thin I beam. Here is the first pass. A little shaky but I had good penetration and filled the chamfer. This needs to be ground flush when done.

I finished the weld and ground it all smooth. Then the first “senior moment” came to me. You didn’t shim the joint! I goofed, pure and simple. All these precautions and I missed that step. What this means is, those big heavy clamps holding the joint in line, while they will hold the metal aligned to each other they cannot hold the weld shrink forces. By jamming a shim in the lower part of the saw cut, it holds the joint width during welding and during cooling. Without it, the weld shrink just pulls the joint closed. This won’t be the last time I make an error (it won’t be this one though) and I’m bringing it up so in case others attempt something like this they do not make the same mistake.

So now what? First off, sleep on it and think! So after tossing and turning all night, you reach down in your bag of “fix it tricks” and come up with a fix. When I use to work in the machine tool world at the V & O Press company, our machine shop foreman always said, anyone can make the part right, but those who can create fix, are the ingenious ones. I never forget that… So I created a fix which was to cut the beam again just outside the weld zone on the rear frame side of the saw cut. Drilling new stop drill holes at each end and using the cut off wheel on the grinder, 10 minutes later I had a new cut line.

Learning from the first event… I shimmed the joint this time and I set up 2 dial indicators on the bottom flange, one each side of the weld joint. The need (trick) is, you only put the minimal amount of heat into the joint to create proper fusion but no more. In this case it comes down to, what weld bead length do you create that will not create too much heat that the cooling shrink causes an unwanted amount of distortion?

Here is the setup

A bottle jack on each side of joint, 2 dial indicators positioned outside the bottle jacks on purpose, the axle unloaded this time and it is just hanging free with a block under it for safety to not cause shackle flop. The joint is shimmed so it cannot close up. I needed to get the upward axle spring force out of the equation.

I would put down a 1” long stitch weld, stop, wait and watch the indicators during the cooling of the weld and see if there was any beam movement. I could see both indicators rise about 0.003" and then during cooling, shrink right back down to 0.000”. Before attempting the next weld bead, check and make sure the weld area has cooled down to around 100F.

The cool down period and not getting too much distortion is major part of this working. If you keep putting in more heat from consecutive welds the amount of heat accumulates, the weld shrink get too big to control. This is a time consuming process but it works. It took a long time to weld this joint, but when I was done and the weld ground and polished, the total beam distortion was less than 0.015” from accumulated movement which I can work with.

I lost a day with the “fix” but it came out good and I learned a lot from it. Vertical welds below the neutral axis (more so then above the NA), of the I beam have the ability to create a negative camber to the beam. Horizontal welds below the neutral access has a small ability to create a slight positive camber in the beam to offset some of the vertical welding. These beams are so thin, it does not take much to create a excessive heat shrink issue. When all was done, the weld was acceptable and the beam was as straight as it was planed for.

 

[JohnGB]

Next was more hole drill’in… First was to drill all holes and bolt the axle side.

Then to do the rear of the saw cut area side and bolt the plates together. I did the drilling across 2 days just to break it up. It could have been done in 1 day, but why push it. I’m retired right... The next part may have been the most exhausting. Torqueing all 54 bolts to 120 ft lb. That is not a lot, but laying on your back under the camper on a creeper working overhead, it was plenty enough.

I started with the 1/2" torque wrench, and after about 20 bolts I had to change something. The position under the camper, pulling with one arm on the torque wrench and using the other arm to hold the box wrench became a challenge. I was running out of pulling, umph… OK need more leverage. So I went and got the 3/4” drive torque wrench. This helped on the pulling, just the wrench was so heavy it felt like I was doing bench presses. The area under the axles was just too tight on the inside to get any kind of leverage so I had to revert to torquing from the bolt heads on the outside and fish my hand around for the bolts with the box wrench. After about 3 ½ hours, I finished. So far this is the most exhausting thing of the whole repair.

Here is the inside pic

Next is to start the lower flange reinforcement flat bars. This flat bar welds on the side of the lower flange and on the bottom of them. They set in like this on the sides

These need to be fitted to work around some bolts in the back of the frame and around the thickness differences of the splice plates. Here are some of the work arounds

Cutting out pockets for bolts

How this flat bar fits in the back of the frame

And the fit around the splice plates. There needs to be a weld joint to join 2 pieces to make the length and I wanted that joint to land on the splice plate area.

I still have more fitting to do on the lower flange reinforcement flat bars and a quantity of weld prep clean up before I start the welding process.

There is one thing that I had to sort out, is how to weld on this lower flange steel and not create a large amount of beam warp. And a major one, to not weld on the beam in a largely loaded condition. It needs to hang free in its natural resting state without a lot of jack force holding it straight. While I was getting a lot of good help from the saw cut and the splice plates, the beam still will not hold itself back to straight just yet. I needed to create a way to get the beam to lay straight with no large outside forces pushing it that way. This took several days in the background thining on how to do this.

You can see here, the slide room opening now comes back to where it needs to be. The slide is parallel with the slide flange like it is supposed to be.

 

[JohnGB]

Now that the saw cut and the splice plates are on, it does not take a lot of force on the beam to get it to this state, but it will not hold it. When I weld on the lower flange steel, that will create the stiffness to hold it. I do not know if Sunline used weld shrink cambering on the top of the I beam frames. I have never seen the top of a Sunline I beam frame rail without the camper on it. I know Artic Fox does and Palomino does on their older Sabre campers. Since the camper is sitting on top of my I beam, I cannot tell. The RV industry is always pushing to use the least amount of weight and materials and in this case, they are forced to use “tricks” to make a thin beam hold the loads. And it seems to work until pot holes come…

To help explain this issue better, here is the frame droop before I started. This 1 3/16” droop will not allow the slide opening in the camper to be square enough to let the slide go in and out.

This is the frame before I did anything. A string pulled down the camper from about 1 foot before the front axle hanger to the rear.

You can see the frame bending down hill

And the 1 3/16 from bottom of frame to bottom of string

Here is where I am with the saw cut fix and the splice plates. I’m at 9/16” droop. The slide will work in this location, but I do not want to leave it this way. My goal is a true square slide opening.

So thinking on this and some calculations, I have come up with early on in the investigation that the back part of the camper from the center line to the slide and from the rear axle hanger to the back wall weighs 1,600lb. 1,500 to 1,600# is also the current force it takes to jack the back of the frame up to hold a square opening from the 9/16” location.

It then dawned on me, what is the natural deflection of this size beam with a 1,600lb load on it? Using standard beam deflection calcs from the steel construction manual, A 105” long cantilevered beam of this size will deflect at the end of it, 0.600” or a little under 5/8” with a 1600 lb point load on the end wall. If we assume the 1,600 lb is evenly distributed along the 105”, the deflection at the end of the beam is only a little over 0.120” or 1/8”. The way the camper is built, it is neither of those extremes, but more loaded something in the middle.

It then occurred to me, this 9/16” I have now, a good part of this is just the raw weight of the cargo and the camper build weight. In order to make the beam lay in a natural resting state without a jack at the end of the frame, I need to unload some weight from the beam? Then weld on the lower flange reinforcements. So I started removing weight.

• Outside the camper, I removed all the cargo in the rear boxes.
• Inside the camper, I moved anything that weighed more than a few pounds from the back of axle area to the front of the camper. Swivel rocker, fire extinguisher, little table etc.
• I removed all the cargo in the storage hole under the slide.
• I estimate this was approx. 300 to 400# of weight
• Removing this weight, reduced the droop from 9/16 to 7/16” or 1/8 less.

While I was gaining, I still needed a lot more. So I removed a good portion of the slide room weight itself from the frame.
• I loosened up the slide mounting brackets and raised the slide to take some weight off the frame rail. This helped a lot.
• Removing this weight, reduced the droop from 7/16” to almost 5/16” or another 1/8 less.

I was gaining but still needed more. At this point the front tire was on the camper bearing full weight of the front axle. The rear axle was loaded, just no tire as I had a wood block and steel shim under the axle seat. This creates leaf spring forces pushing up on the frame. OK, try removing them, so I did.
• Installed a 20 ton jack stand at the front axle hanger area. This is load bearing.
• Removed front tire.
• Removed the rear axle seat shims. Both axles are now hanging free
• Put wood blocks under each axle seat but with an air gap just to prevent shackle flop if the axle is bumped.
• Installed a red bottle jack at the rear hanger to just kiss the hanger for safety, no upward force.
• Installed a jack stand at the rear cargo box frame and shimmed height to just kiss the frame. Not holding load, just there for safety.
• Re-pulled the string. The 5/16” is now at 3/16” droop.

Here are 2 pics showing the setup

Here is the line of site at 3/16”. It is almost totally straight on it’s own.

And a piece of 3/16” square stock about the bottom of the flange

Then I went to the back of the camper and went to lift by hand on the rear bumper. I could with 1 hand lift some of the weight up. So I put a Sherline tongue weight scale under a rear jack and measured the lift force and distance.

The forces and distances are:
• 1/16” = 100# of lift
• 1/8” = 200# of lift
• 3/16” = 300# of lift

I am now close enough that with very little force on the back of the camper lifting, the beam is in its natural resting state for welding on the reinforcements. By picking 100 to 300# of lift I can create a straight frame.

Now the weld sequence on how to make the frame not move from weld shrink. Here is the plan and the order of the welds. Each will area will have dial indicators and putting down a 1” stitch length as a starting place. The indicators will guide if I can make that length longer. After each weld allow the weld to cool to the 100F area. This will take time to weld out, but time I have.

This brings me up to date on the latest activates. Next is more lower flange flat bar to prep and then start the welding process.

Thanks for looking

John

 

[Trailblazer-MGRV]

I haven't been on the board for a number of months so I am just starting to catch up in a number of posts. All I can say is WOW John, this is something I would never have thought of. When I can get access to our 5th Wheel again later this year, I have something else to check now. A couple years ago I hit the worst asphalt heave in Michigan. It was so bad it almost felt the trailer could have gone airborne. Although at the time I couldn't see any structural damage, I never considered it could have caused some small damage that would get worse over time. As always John, you have provided another great post with lots of details. Thanks for posting!

 

[Mrtweety]

John,

This is truly fascinating stuff. Amazing how sensitive the "square slide opening" is to seemingly minor beam deflections. I'm starting to wonder how they built these things correctly in the first place. Also for my next trailer I am seriously considering going back to no-slides. Slides are complicated. They leak, they rot, introduce motors and gears as well as unnatural gaping holes in the trailer wall with associated fit / mech issues such as you are encountering. In this sense I think Airstream gets it right - but at ridiculous cost.

Anyway - can you expound a bit on the lower flange welded bars you are now working with? Could this have been accomplished with adding a lower flange on the sister plates? I do see how these plates nicely incorporate the lower flange of the original beam and tie it together with the sister plate. They also have the effect of stiffening the original beam lower flange to resist lateral bending. I've seen these plates used on other campers where the spring hangers are attached I presume for just that reason. I also see how you are using them to weld / secure the final assembly in a low stress natural state. What other thoughts did you have on these lower plates ?

Steve