Wheel Bearing size needed.

[mainah]

Most common cause of broken leaf spring is overload. They generally break at the center pin. When I first got my camper pretty much everything that moved on the springs were worn out. Rocker beam plastic bushings were gone. I drilled and taped the rocker beam and used real bushings and grease fittings. The bolts on the rocker beam were obviously worn so they got replaced but that was it.

[JimS]

I did torque the spring pack in an x fashion. I did it in three steps, final one at 60# ( axle flip instructions said between 45-70). About 100 miles retightened. At about 600 miles, I was surprised that they needed retightened again. At about another 500 I checked again with just a tiny bit here and there needed. Checked again at another 1500 and all was good.

I’m sorry to say by the time I asked the last question I had disassembled the broken spring and didn’t get the torque on the that spring pack nuts. I did take it on the ones that were still left to do, and they all read between 55-60#.

Now on to possible reasons that I wonder about when I did the axle flip:
I flipped the center pin in the center of the spring pack when I did the axle flip. I didn’t torque that much, maybe 20-30#, as to what info I could find on that said it needed only snug tight. The new springs I bought, I tested the torque on the center pin before turning that pin over. They were at 50#. So did I not tighten those pins enough the first time?
Next, Instead of using plastic sleeves in the spring eyes, I had put in brass sleeves. They fit really tight, so much so that when I put the greasable shackle bolts thru it was a tight fit. So was this a contributing factor? Taking everything apart now they are actually loose, so they wore in very quickly.
And next, My order of assembly of the parts I did by attaching the springs to the frame, then I lifted the axle to the springs and attached with U-bolts. The axle flip instructions did say attach springs to axle then attach springs to frame. Was this a factor?
And next, going from shouldered shackle bolts to non shouldered. Don’t think this was a cause, but it’s possible I suppose.

This trip was a tough one. Lots of stuff along the way, some of which might have contributed to the spring failure. On the way home, I was on a two way highway in the rain, semi truck coming from the other way, and while going by the semi, a bunch of stuff came at me. Enough to break apart the bug guard, dent the van hood, break the headlight fixture, and put a big dent in the front of the camper. The next day the electric brakes started giving me problems, going out at random times. The following day from that is when the spring broke. Any coincidence? Did something get under there and mess stuff up? Who knows. About a few hours before the spring broke, I was on a pretty rough interstate that was under construction. Lots of bumps/humps. Probably a big contributing factor.

At the time of failure I was coming off the interstate, crossing a bridge. At or near the bridge seam in the road, I heard the large pop. Wasn’t a very noticeable bump there, if any at all.

I have purchased new springs, and they are now 1750#, instead of 1250#.

My torques on things the second time around:
Center pin thru springs @ 50#
Shackle bolts @ 30#
Spring pack u-bolts @ 60#, increased in 5 steps.

My neighbor has worked professionally with metal his whole life. I showed him the break and said it was from overload. The metal was probably weak from age and couldn’t hold the rated weight any more. He says the top of the spring was damaged first, then the bottom half finally gave way.
I will take a picture of the spring pack when I get a chance.

- Jim

[JohnB]

Hi Jim,

A quick note, more later but I go to go now. The center pin torque at 50 ft lb sounds way high. BUT, this first starts with confirming the bolt size you have. My foggy memory recalls the ones on my T1950 to be a 5/16" grade 5 bolt by the head markings. The key at this point, what diameter is yours? 5/16, 3/8"? Any head markings?

Traditionally, a fastener that has been tightened, does not have the same exact un-torqueing torque to it. So you can torque up a bolt at say, 70# and if you take the nut off, it may come off higher closer to 80 to 90# The friction is different in the tightening action then the loosening action and with the lock washer in the mix it adds more difference.

Make a phone call to Dexter or the spring manufacture of the brand you bought and ask them for the correct torque. Just measure the bolt size first so you have that and many of them are fine thread.

Point being, if yours is 5/16", 50 ft lb dry threads may put the bolt close to over over the yield point. Lubed threads at that torque is even worse.

The tight fit spring pins and bushings, the tightness on the spring pins on the hangers, the brakes issue loosing the brake, I'm not seeing any connection of them to the failed spring. The really bad rough road maybe a factor with age, weight etc, and they I want to talk more on if the suspension went into extreme max or over max suspension travel. Your metal guy saw the first fine crack followed by a total break though. He has good eye and has been around.

Yak more later, go to go now

John

Also where did the spring crack? At the center pin or the edge of the U bolt plate?

[JimS]

please ignore the blue paint on the one end of the smaller piece. It’s the result of human error ☺️.

The fan shaped marks on the top half of the top spring are what the neighbor says is the injuries. The small blacks lines radiating thru each fan are tiny cracks. Then the bottom half of the bar that is darker grey is what snapped all at once, when the top part wasn’t doing its job any more.

1A70F3DB-F93D-4C79-AC11-604085AA38E1.jpg

7729A333-075E-4EAC-820C-8F40EA74BA74.jpg

[JimS]

Originally Posted by JohnB

My foggy memory recalls the ones on my T1950 to be a 5/16" grade 5 bolt by the head markings. The key at this point, what diameter is yours? 5/16, 3/8"? Any head markings?

3/8”

Originally Posted by JohnB

Traditionally, a fastener that has been tightened, does not have the same exact un-torqueing torque to it. So you can torque up a bolt at say, 70# and if you take the nut off, it may come off higher closer to 80 to 90# The friction is different in the tightening action then the loosening action and with the lock washer in the mix it adds more difference.

Hmmmm. Here is how I came up with 50#. I loosened two of the nuts (four new spring sets), both came off with the torque set at my lowest setting of 20#. Then the other two nuts I kept increasing the torque by 5# at a time until the nut started to tighten (instead of loosen).That didn’t happen till I got to 55#. I wondered if this made sense, so I took some spare shop bolts and did the same thing. Tightened them up to 50#, and it only took about 20# to loosen.

You mentioned lock washers. I was wondering about this. Should the spring pack have lock washers? There was none that came with the axle flip kit, and it seems like the nuts aren’t lock nuts.

Originally Posted by JohnB

Also where did the spring crack? At the center pin or the edge of the U bolt plate?

Neither.
See post above.

[JohnB]

Jim, some more thoughts.

Originally Posted by JohnB

My foggy memory recalls the ones on my T1950 to be a 5/16" grade 5 bolt by the head markings. The key at this point, what diameter is yours? 5/16, 3/8"? Any head markings?

Originally Posted by JimS

3/8” ]

OK, if they are 3/8 and fine thread, (check they are fine thread) they can take more torque. My T1950 is out with a family member right now camping, so I cannot confirm it's center bolt size. Not sure if all manufactures use the same size center bolt in this range of spring. But, now we know yours is 3/8" The next unknown is the grade of the material.

3/8-24 grade 5 bolt with dry threads (K=0.2) uses 35 ft # dry to get to 75% of yield strength.

3/8-24 grade 8 bolt with dry threads (K=0.2) uses 49 ft # dry to get to 75% of yield strength.

My source is from Fastenal guide book here. Use the K=0.2 column for dry threads. https://www.fastenal.com/content/mer...ce%20Guide.pdf

Originally Posted by JohnB

Traditionally, a fastener that has been tightened, does not have the same exact un-torqueing torque to it. So you can torque up a bolt at say, 70# and if you take the nut off, it may come off higher closer to 80 to 90# The friction is different in the tightening action then the loosening action and with the lock washer in the mix it adds more difference.

Originally Posted by JimS

Hmmmm. Here is how I came up with 50#. I loosened two of the nuts (four new spring sets), both came off with the torque set at my lowest setting of 20#. Then the other two nuts I kept increasing the torque by 5# at a time until the nut started to tighten (instead of loosen).That didn’t happen till I got to 55#. I wondered if this made sense, so I took some spare shop bolts and did the same thing. Tightened them up to 50#, and it only took about 20# to loosen.

You mentioned lock washers. I was wondering about this. Should the spring pack have lock washers? There was none that came with the axle flip kit, and it seems like the nuts aren’t lock nuts.

OK this is good info, part of the way you did your testing may explain the 20# removal, more on that shortly. But, your increasing torque by 5 # and 55# starting to move the nut I feel is valid and it helps point to that your center bolts are stronger then a grade 5 bolt. And your center bolt can be more closer to the grade 8 which a 3/8-24 bolt dry threads would be 49 ft lb.

Seeing that, I agree your new springs came with an approx. 50ft # torque range on the center bolt.

I also just tested that same increase the torque on a known 100 ft # 1/2" bolt will take torque at about 103 ft #. So I confirm your 50 ft lb range on the center pin with 3/8-24 threads is a good number.

More on the rest to explain the greatly lower removal torque shortly as I have to load some pics.

Be back soon.

[JohnB]

Originally Posted by JimS

3/8”

Hmmmm. Here is how I came up with 50#. I loosened two of the nuts (four new spring sets), both came off with the torque set at my lowest setting of 20#. Then the other two nuts I kept increasing the torque by 5# at a time until the nut started to tighten (instead of loosen).That didn’t happen till I got to 55#. I wondered if this made sense, so I took some spare shop bolts and did the same thing. Tightened them up to 50#, and it only took about 20# to loosen.

You mentioned lock washers. I was wondering about this. Should the spring pack have lock washers? There was none that came with the axle flip kit, and it seems like the nuts aren’t lock nuts.

I went out in the barn and repeated part of your test to see if I can figure out the large difference in 20 # to remove while 50 range for tightness.

First off, my memory of years of testing is getting mixed up a little. I did a lot of testing at work dealing with stainless bolts tested to failure. We had to have custom made high strength stainless as off the shelf grades were not strong enough. During this testing we need to see the torque to failure (bolt starts stretching) to confirm the failures we were seeing in the machines.

During this testing we also removed the nuts. The 300 series stainless we where using can gall badly under high friction and tightening up bolts creates high friction. In this case with stainless, loosening a pre-torqued bolt could create higher removal torque due to galled stainless in the threads or the nut to the steel. Carbon steel bolts do not have this characteristic as badly. So my example of needing higher torque to remove is only applies to stainless steel bolts on stainless metal.

To back into what you were seeing with the 20# removal and 50# application range, I started with 1/2" grade 8 bolts and nuts to get the torque higher to see if I can find out how your difference is so large.

Here is the first setup. New 1/2" bolt held in the vise, 1/2" clearance hole in a piece of stainless plate to clamp between the nut and bolt, and a 1/2" new nut. I wanted the plate in the middle of the nut and bolt to simulate a clamped joint. Friction has a lot to do with bolt torque.

I torqued the nut to 100 ft #. The bolt did not spin at this point during the tightening. I started at 50 ft # to remove which did nothing. I jumped to 60 ft # and the nut started to loosen. H'mm OK what is up here?

I repeated the test two more times and similar results, 100 ft # applied, 60 to 65# to loosen.

Here is the setup


It then dawned on me the test setup was not good. The plate is rotating when I start to break the nut loose. So I changed the setup and clamped the plate. See here, I did 2 tests like this with the plate clamped. One without the wrench holding the bolt, the other test with the wrench under the bolt head holding it as shown.


Plate clamped, no wrench on bolt. I torqued to 100 Ft #, then did the loosen test. This setup helped but I was still getting low in the 60's # for removal. I noticed the bolt was starting to spin as the 60# removal torque started to break free the nut.

The third test I added the wrench to the bolt and locked it against the vise. The plate cannot spin, the bolt cannot spin, the nut can spin as needed.
Torqued to 100 Ft #. Removal at 90 Ft # This test repeated itself 3 times.

Then I changed the plate to aluminum and repeated the same tests. See here. Plate in vise, no wrench to start with.


The no wrench to hold the bolt verses using the wrench results, repeated as it did with the stainless plate with a slight shift change in the final removal torque with the wrench in place.

Aluminum plate, bolt held by wrench, plate held by vise, nut free to spin. Torqued to 100 Ft #, removal at 80 ft #. The test repeated 3 times. Without the wrench, the removal was in the 55 to 60# area

Friction is alive and well in these tests. Once the bolt or plate started to move any, that change the pre-load in the bolt and the nut loosens with low torque. When the plate or bolt shift/turn there may only be a slight off parallel of the joint taking place, but the fastener tension changes. When the bolt and plate remain stationary when removing the nut, the removal torque is high. The friction difference between stainless and carbon steel is different then aluminum and carbon steel and the nut spinning off the different plate material changes the torque.

With all that, did you hold the center pin from rotating when testing and was there a non movable plate of something between the nut and bolt?

As to using locking fasteners on the U bolts or the center bolt. For U bolts, it is common not to use locking fasteners. The Sunline campers or other brands I have worked on, do not have locking fasteners on the U bolts. My F350 does not have locking fasteners on the rear leaf springs U bolts. It appears the industry has accepted on normal U bolts on traditional leaf springs do not require it.

On the center bolt, I do not recall them having a lock nut either. I must say, I have had more U bolts apart then spring packs, so I can't say how many spring packs do not have the locking fastener on the center pin.

There are places that always use a locking feature and others that do not. It depends on the application. There is no one size fits all rule on this that I know of. I can site many examples for both needs. Traditionally, machined parts, with high strength fasteners do not use a locking feature unless extreme vibration exists. High vibration applications always uses locking fasteners. It is the middle of the road applications that use a locking fastener as standard practice, just because it is believed to be needed and most times is.

John

[JohnB]

Originally Posted by JimS

please ignore the blue paint on the one end of the smaller piece. It’s the result of human error ☺️.

The fan shaped marks on the top half of the top spring are what the neighbor says is the injuries. The small blacks lines radiating thru each fan are tiny cracks. Then the bottom half of the bar that is darker grey is what snapped all at once, when the top part wasn’t doing its job any more.

Attachment 9122

OK it broke on the end of the lower leaf support. Great picture!

I blew it up some to look closer


I can see a few things going on.

There are many little fishers of what might be cracks coming down from above and the metal color is slightly different, like rust may have been in there. Corrosion pits have been known to start a crack when high flexing stress comes along. It is hard to tell from here if this is the case.

The crack happened over many flexing cycles. It was not one big instant overload. In order to count the cycles you need a very good microscope, electron scanning microscope.

The crack line started where the leaf used to be on top. That same bottom leaf in your pic used to be on top of the main leaf, now it is under it. Years of rubbing, rust, corrosion at the joint, fatigue, now heavier loads even if not over the spring limit, and then your really rough roads may have set the perfect storm to create this.

If the suspension went into max travel over very rough roads, this can also aggravate the situation. Campers do not seem to ever have overtravel stops. While I have seen overtravel stops on auto's, I have not seen them on a trailer, even a non camper trailer. Some may have them, but it is not a common thing.

Good to hear you are putting in the higher rated spring. That will help for the future.

[JimS]

Originally Posted by JohnB

With all that, did you hold the center pin from rotating when testing and was there a non movable plate of something between the nut and bolt?

John

YES!!!!!!
I only held the center pin, and the stack of springs were free to turn. Makes perfect sense now.
I love it, understanding the small details. Looks like you too need to figure out things with actual results, instead of just accepting what is written.

It’s a lot of work to do what you do with a post like this, but I’m thinking you enjoy it. Thank you.

[JimS]

Originally Posted by JohnB

The crack line started where the leaf used to be on top. That same bottom leaf in your pic used to be on top of the main leaf, now it is under it.

Whoooaaaa?????
I’m hoping this is wrong. Perhaps you were in a hurry and mistyped? Or am I not understanding the wording?

Or I did not do something right in a big way!!!!

I did not change the stacking order of the spring pack. I only flipped/turned over the center pin bolt.

- Jim

[JohnB]

Originally Posted by JohnB

The crack line started where the leaf used to be on top. That same bottom leaf in your pic used to be on top of the main leaf, now it is under it.

Originally Posted by JimS

Whoooaaaa?????
I’m hoping this is wrong. Perhaps you were in a hurry and mistyped? Or am I not understanding the wording?

Or I did not do something right in a big way!!!!

I did not change the stacking order of the spring pack. I only flipped/turned over the center pin bolt.

- Jim

Hi Jim,

No mistype, I just plain goofed...sorry. You are correct, the spring pack remains the same. Not sure what I was thinking. I should of confirmed it first. Any time someone see something not right, please ask. I'm human too.

This is mine, but yours is the same.

The original underslung setup. Main leaf on top


After the under to over conversion. The main leaf is still on top


The corrosion pits is still a valid thought, The flex and stress would be higher where the main leaf and the one under it stops. Since we know the spring crack started on top, and the crack is a tension snap from an upward flex, the main axle went up from a road bump etc and the spring flexed up trying to control the amount of up movement as it always does. The end result, the crack started and once a crack in steel starts, time and more flexing into the same area that started the crack, keeps ripping a little more metal every flex cycle until failure.

I keep thinking about this, and I am still coming to the same conclusion, this crack would of still happened if you never did the over to under conversion. There is no travel stop on the original setup nor is there on the new one, or any new camper with the spring pack on top.

Any corrosion, the added weight even within limits, fatigued steel, the high degree of more flexing, the mega road bumps and the problem happened. Just think what could of happened if you did not have any extra wheel clearance line on the original setup? The crack initiation could of been there before you even owned it.

If you really want to know how the crack started, I know a good metallurgy shop we used for part failure analysis. They have the equipment to back into exactly what happened and you get a really nice report on it. The issue is the cost. You could buy a new small camper for the cost of the report. Sure glad work was paying for this stuff.

Curious, which end of the spring broke, the end by the equalizer or the end by the spring hanger?

[JohnB]

Originally Posted by JimS

YES!!!!!!
I only held the center pin, and the stack of springs were free to turn. Makes perfect sense now.
I love it, understanding the small details. Looks like you too need to figure out things with actual results, instead of just accepting what is written.

It’s a lot of work to do what you do with a post like this, but I’m thinking you enjoy it. Thank you.

Thanks Jim, you are very welcome.

Yes, there is gratification in helping and digging into the details to better understand the real issue at hand. I can stop thinking about it, unless I understand it better or totally. It's hard to shut the brain off thinking about this stuff when it does not add up.

[JimS]

The left rear spring broke. It broke closest to the rearest most point by the hanger. Over all I feel that is the lightest part of the load in my camper design(I think?). The water storage tank is on the right side. On the left side is the fridge, closet, bathroom, and furnace.

Yes, think how much it would have torn up my fender, AND that would have shut me down right in the place it occurred. Also, the suspect of the springs having fatigue in support of load is more evident now.

In hindsight, it seems a lot of things lined up in my favor with this incident. One major one is the brakes going out. I think if the brakes had still been working, every time I used them would have put more stress on the parts still holding the axle on. Then when I lifted the trailer up to repair, as soon as the weight was off the axle it all kind of fell apart and out of alignment. My thought was good thing I didn’t go over a big hole where it would have dropped and all fell apart.

[JohnB]

Originally Posted by JimS

The next day the electric brakes started giving me problems, going out at random times. The following day from that is when the spring broke. Any coincidence? Did something get under there and mess stuff up? Who knows. About a few hours before the spring broke, I was on a pretty rough interstate that was under construction. Lots of bumps/humps. Probably a big contributing factor.

Yes Jim, with the original wheel clearance to the fender, you would of really tore up the fender.

Now to the brakes going in and out of working.

A few thoughts to look into.

The chassis grounds on the camper are a classic rust to the point they do not work. Especially on the brake circuit. If you loose the ground connection from the 7 wire cable at the front of the camper due to a rusted connection, then at the brake area, the brake wire to the chassis is all corroded up, nothing works. Short term, clean up the ground connections to the chassis. Long term, consider running a dedicated ground wire starting at the 7 wire cable ground all the way back to the brake area. that wire should be 12 awg or heavier in my view. Maybe 14 awg on your shorter camper but for sure, nothing less.

Next is the axle area. If you are still using the 2 wire cable inside the axle tube to cross over to the opposing side, that 2 wire cable is a classic for chapping the insulation through and then touching the inside of the axle tube. If the ground wire touches, not so much an issue. It the hot wire touches it will short out the brake coil connection and that brake will not work. The dead short may give your brake controller fits too. Those wires get brittle on the insulation an cracks making it worse with water creating a path to ground connection. Long term, suggest abandoning the 2 wire cable in the axle tube and go to new wire strapped to the outside of the axle tube on the back side, so weeds don't beat it up. Or run new wire over attached to the floor and then down to both wheels. Or run new separate wire from the front of the camper down each side to each wheel.

Also check the connections where the axle wire joins to the front long wire. You must of had them apart to do the axle flip change.

The 7 wire plug at the truck is also suspect. I had this issue on my flat bed trailer. It was a nice built trailer but had junk for trailer wiring including the 7 wire plug. Every time I turned, the 7 wire had a good chance it would unhook the trailer brakes. My controller come back with trailer disconnected. There was plenty of wire flex, just the plug was so bad any sideways pressure and it did nt make contact. We gave up on it and put in a new all molded in one 7 wire cable and plug. They had the screw terminal type with individual wires. The new molded cable solved the problem.

Hope this helps

John