Ford F350 Cracked Frame

HMS Beagle wrote:
There is another engineering issue with typical air bag mounts not mentioned above. Some of these mounts cantilever out from the C channel frame (the newer ones not as much). This puts a twisting stress into the frame channel. If you look at the spring attachments, they are also cantilevered out so what's the difference? Usually there are cross members placed right behind or very nearly behind the spring mounts. These cross members resolve the twisting stress produced by the spring mounts. There are no cross members where the aftermarket bag mounts attach.

The Ford engineers aren't stupid (well generally speaking anyway :)), but they cannot engineer the frame to allow for anything some aftermarket supplier might think up. The problem is that the aftermarket suppliers very often do very little engineering at all.

I fully agree with that.

On this particular F550, no air bags were being used. It was a well drilling truck, with leveling outriggers at the rear of the bed. The upward pressure of the outriggers on the tail of the frame induced a downward force farther forward on the frame, above the axle. The frame cracked at it's weakest point, where the scallop is located. The frame web height is also shortest above the axle.

There is another engineering issue with typical air bag mounts not mentioned above. Some of these mounts cantilever out from the C channel frame (the newer ones not as much). This puts a twisting stress into the frame channel. If you look at the spring attachments, they are also cantilevered out so what's the difference? Usually there are cross members placed right behind or very nearly behind the spring mounts. These cross members resolve the twisting stress produced by the spring mounts. There are no cross members where the aftermarket bag mounts attach.

The Ford engineers aren't stupid (well generally speaking anyway :)), but they cannot engineer the frame to allow for anything some aftermarket supplier might think up. The problem is that the aftermarket suppliers very often do very little engineering at all.

That is exactly where my frame cracked. I added StableLoads to take some pressure off the bags. So far no more problems. I run a LOT less pressure in the bags now.

Dale

BigToe wrote:
Just for the record, many Ford pick up truck frames have a moon shaped cut out in the lower flange to provide clearance for the shock absorber.

Frame cracks on Fords equipped with air bags typically initiate from this lower flange cut out area, which is very near where the air bag mounting apparatus is bolted. The crack propagates upward, until arrested by an existing hole in the web of the frame. Very common.

The most important two parts of a C channel truck frame are the upper and lower horizontally oriented flanges. The vertical web of the frame's main purpose is to keep these two highly loaded flanges at a prescribed distance from each other. Ford permits drilling into the vertical web, but forbids drilling or modifying the all important horizontal flanges. The upper and lower flanges are subjected to the greatest proportions of compression and tension.

So it is not surprising that an already scalloped lower flange cracked when subjected to a concentrated load placement (from the aftermarket airbag) in an area of the frame that was not designed to bear that load. The frame is designed to take the load at the spring hangars, not at a mid point between the spring hangars.

All the air suspensions on big semi trucks and trailers are completely irrelevant to this discussion. The issue isn't air or bags. The issue is placement of stress on a specific area of the frame that was not only not engineered for it, but is in fact actually weaker in that specific area due to the half moon shape scallop out of the lower flange for the shock clearance.

For this reason, if more rear spring capacity is needed, then a heavier overload spring might be a better way to go on certain Ford pick up frames.

This is exactly correct.

I have welded up the frame of an F550 that cracked on both sides, both starting in the middle of that scallop in the lower frame rail. I end drilled the cracks to keep them from running, beveled them out and welded them up. Then I cut out 2 half circles of 1/4" plate, which I used to fill in both of those scallops. Next, I fish plated the frame on the outside webs. Finally, I cut off both upper shock mounts and spaced them inboard about an inch, to allow clearance for the shocks with the frame scallop filled in.

All Ford had to do to eliminate this common Superduty frame cracking problem was move the upper shock mounts inboard about an inch, like I did. That would have allowed the frame to have a full width lower flange, with no cutout for shock clearance. The shocks would clear and operate fine and the frame strength would be increased many times.

Amazing what these engineers come up with for solutions to problems that don't exist, thus creating problems that weren't there to begin with...

Big Toe, that is exactly where mine cracked. It ran for 9 years before it did.

By adding the Stableloads, more of the load is transferred to the overload springs much earlier than previous.

Tici2,

The procedure is a little too long to detail here, but basically you turn off the fridge, unplug everything and remove the board cover. All will be unplugged except the big multi wire plug, then plug the 12v hot and ground back in, turn the fridge back on and ground pin #15 in the large plug with a jumper wire. Pin 15 is the 2nd from the left on the top row. There is no wire in this pin hole. Ground for about 5 seconds. Then plug it all back in and turn the fridge on.

I am pretty sure there is a thread already on this site, I will try to find it and post a link.

EDIT:
check this link

http://www.ehow.com/how_7679848_reset-norcold-control-board.html

Dale

bookmaker wrote:
One other discovery was made on that trip. The refrigerator quit the night before we got to Oshkosh. We got a service man out and he had it going in just a few minutes. He showed me a reset procedure.

I think it is blowing out on the road, trying to relight, blowing out again causing it to lock out.

When we got home, I decided to check the procedure on the original board we had replaced a couple years ago when it quit on the road. Sure enough, it fired right up.

Now I have the original board, a spare Dinosaur board and a 2 way board (that was installed in an emergency a couple years ago).

I think I have spares covered.

Dale

If you care to share that procedure it would probably be helpful to others . A new topic would be good .

Just for the record, many Ford pick up truck frames have a moon shaped cut out in the lower flange to provide clearance for the shock absorber.

Frame cracks on Fords equipped with air bags typically initiate from this lower flange cut out area, which is very near where the air bag mounting apparatus is bolted. The crack propagates upward, until arrested by an existing hole in the web of the frame. Very common.

The most important two parts of a C channel truck frame are the upper and lower horizontally oriented flanges. The vertical web of the frame's main purpose is to keep these two highly loaded flanges at a prescribed distance from each other. Ford permits drilling into the vertical web, but forbids drilling or modifying the all important horizontal flanges. The upper and lower flanges are subjected to the greatest proportions of compression and tension.

So it is not surprising that an already scalloped lower flange cracked when subjected to a concentrated load placement (from the aftermarket airbag) in an area of the frame that was not designed to bear that load. The frame is designed to take the load at the spring hangars, not at a mid point between the spring hangars.

All the air suspensions on big semi trucks and trailers are completely irrelevant to this discussion. The issue isn't air or bags. The issue is placement of stress on a specific area of the frame that was not only not engineered for it, but is in fact actually weaker in that specific area due to the half moon shape scallop out of the lower flange for the shock clearance.

For this reason, if more rear spring capacity is needed, then a heavier overload spring might be a better way to go on certain Ford pick up frames.

One other discovery was made on that trip. The refrigerator quit the night before we got to Oshkosh. We got a service man out and he had it going in just a few minutes. He showed me a reset procedure.

I think it is blowing out on the road, trying to relight, blowing out again causing it to lock out.

When we got home, I decided to check the procedure on the original board we had replaced a couple years ago when it quit on the road. Sure enough, it fired right up.

Now I have the original board, a spare Dinosaur board and a 2 way board (that was installed in an emergency a couple years ago).

I think I have spares covered.

Dale

Update on frame and improvements:

Frame was welded by frame shop and I added Stableload blocks. Took a 2,400 mile round trip from the Florida Panhandle to Oshkosh, WI for EAA AirVenture. Great trip. 550,000 attendees and thousands of campers. Estimated 10,000 planes.

The Stableload blocks definitely allowed lower pressure in the airbags. I went from 90+ lbs to less than 40. The ride was about the same. Ugh, I-65 in Birmingham, AL is the pits. Shook everything loose that it could, including me. Otherwise a great trip and the truck worked fine.

We have another trip planned to the Dayton, Ohio area soon so it will get another test.

Dale

bookmaker wrote:
No pics of the repair. Welded, but not plated. The frame shop indicated that plating was not considered necessary due to the location of the crack and that it only went from the bottom of the frame up to the lowest hole. There is however a LOT of weld on the inside of the frame.

I have added the Stableloads to eliminate much of the load on the bags. I had been running them 10 years at 90+ lbs pressure and finally had a problem. I am hoping the stableloads will allow much decreased pressure in the bags - and no future problems.

Dale

The weld should be stronger than the original frame, if it was welded properly.