3500lb axles bad design

[Lynnmor]

Probably most medium size trailers have the 3500lb axles and 10" brakes. The design of the spindles has little to no shoulder to locate the inner bearing. When I looked up the blueprints, I found that the spindle shoulder has a contact area against the ground surface of the bearing of about .020" and can be as little as zero using the print tolerances. That extremely small contact area can cause burrs, seal damage, loss of bearing adjustment and bearing alignment.

Today, I pulled and serviced all four hubs and found contaminated grease in two of them. The metal wearing away from the spindle contact area was the issue. The ground surface of a bearing is where it is to take the load, not the roughed in clearance radius.

To show you what I am talking about, in this photo is the blackened grease and a narrow band of metal which is the contact area that takes the lateral load of the trailer.


Here is a photo showing the result of the bearing radius carving its way into the spindle shoulder.


This photo shows the bearing with bluing so that the contact area can be found. Of course the bearing is on the spindle backwards for its photo op. The narrow dark blue band is the only support designed into this spindle. The lighter blue areas are where the roughed in radius is now locating the bearing.


I do not have an easy fix for this design fault. Short of replacing the axles with 5200lb units, all we can do is frequent bearing cleaning and repacking. For those that choose to use the grease fittings, just remember that the metal shards will be pushed to the outer bearing and the bearing adjustment still needs to be done frequently.

Here is a view of the metal shards I am talking about:

[wilber1]

What make of axle? Lippert axles have been notorious for grease covered brakes. 215 so far on the Grand Design forum alone. Word is they have switched to Dexter.

[time2roll]

So get new spindles already. What brand are these with trouble?

The grease on my AL-KO 3500 axles was mostly red after 10 years.
I saw no issues on mine.

[Lynnmor]

mike-s wrote:
The design is fine. It's just you.

Here is a bit more, if you can stand it:

[mike-s]

The design is fine. It's just you.

[Lynnmor]

mike-s wrote:

Lynnmor wrote:
Here is a photo of an actual bearing, it measures 1.651" where it contacts the shoulder.

OK, so the shoulder (1.72) minus your measurement (1.651) = 0.069 difference in diameter, so the overlap is half that, 0.0345. From the drawings, I came up with 0.032 as a minimum.

So, what's your point, and explain why no one else is having this problem.

Oh, and what did you base your claim about the contact being "about .020" and can be as little as zero using the print tolerances." What has a tolerance of .020, or even .010?

My point is that folks like you never recognized the issue and go about their merry way not knowing or caring about things mechanical. As long as the telephone poles keep coming at them, they never had a problem. I show actual photos and describe what I see and, for some reason, I am the villain. But I knew before posting that the finger pointers would come out in force.

You neglected to take into account the radius on the spindle shoulder. You also didn't understand that I said it was one of the better samples that I measured.

Now the real question is why would anyone take such things personally and come to the defense of such a marginal design.

[mike-s]

Lynnmor wrote:
Here is a photo of an actual bearing, it measures 1.651" where it contacts the shoulder.

OK, so the shoulder (1.72) minus your measurement (1.651) = 0.069 difference in diameter, so the overlap is half that, 0.0345. From the drawings, I came up with 0.032 as a minimum.

So, what's your point, and explain why no one else is having this problem.

Oh, and what did you base your claim about the contact being "about .020" and can be as little as zero using the print tolerances." What has a tolerance of .020, or even .010?

[RinconVTR]

Interesting thread. I do not see any problem at all.

Except for the person who said the inner race is suppose to spin...yeah...that's wrong. The inner race is NOT suppose to spin on the axle under load.

[Lynnmor]

Here is a photo of an actual bearing, it measures 1.651" where it contacts the shoulder. Note that the manufacturers undercut the radius area so that the surface to be ground stands proud and eliminates increasing the contact area. The pictured example is one of the better ones that I have seen.

[Lynnmor]

I have done the research, the math and the actual measurements, if you think that the tiny surface is sufficient, fine. One thing that should be considered is that the load is not even across the entire area due to clearances and attempting to find the yield is just a guess.

[mike-s]

keymastr wrote:
In that drawing R is a radius, not a measurement of a contact surface. Just describes how sharp the curve is.

R is a maximum radius. It places a limit on what material can be removed. This might help you understand:



That 1/2" in the leftmost drawing? That's the radius, and not coincidentally, also the distance beyond which no material has been removed. They're one and the same for a right angle corner.

Here's a rather large image, which may make it even easier for you to understand.

[keymastr]

In that drawing R is a radius, not a measurement of a contact surface. Just describes how sharp the curve is.

[mike-s]

#84 spindle has bearing id of 1.376 and a shoulder of 1.72. That's a difference of 0.344 in diameter. The shoulder is 0.172 bigger than the bearing in radius.

Here's the bearing, per Timken:


The critical measurement is R, which is 0.14 max. So an L68149 on a #84 has an overlap of 0.032 (min), and a contact surface of ~.14 sq in (min). It has a thrust rating 1890 lbs, which would result in 13500 psi (aka 13.5 ksi).

A cheap and common mild steel alloy, cold drawn 1018, has a yield strength of 54 ksi. But the spindles are likely better steel. I've found references to 1040 and 1045 being used for spindles (71 and 77 ksi).

If the spindle is deforming, it's because the bearings were installed too loose and it's getting hammered.

These spindles have been around forever and are very common. If the design were a problem, it would be a widespread issue. It's not.

[Ozlander]

WNYBob wrote:
Were the bearings tightened properly? Looks like the inner race was turning, and it is not supposed to do!

Yes it is supposed to rotate. Evens out the wear.

[greydog]

So sleeve the seal surface to increase seal diameter and provide a flat, perpendicular shoulder for the inner race to seat against. I've done this to renew seal surfaces many times. The sleeve is a shrink fit then turned to diameter. Good to post the issue you have seen and I'll have a close look at mine. In truth, I would like to see a slightly heavier axle on many trailers. When a trailer is listed as having a GVW of 6980Lbs, I don't think two 3500's is quite what should be on the trailer but that's the way things are, I reckon. GD

[Lynnmor]

Ralph Cramden wrote:

Lynnmor wrote:


This is a #84 spindle and is used by all the axle brands, it is poor design and has nothing to do with the quality of my work. I posted about this several years ago, only to have the thread locked in a matter of hours.

Not knocking your work or your theory but I have had 4 different campers with 3500 lb axles, and over the years somewhere in the neighborhood of 20+ equipment trailers with 3500 lb axles that I was ultimately responsible for. I have never had the issue you describe.

Why not email your theory and pics to Dexter? Those guys are usually very responsive. I would like to know what they say about it. As you said, the design is used on a lot of trailers, and has been for what? 50 years or longer? It's been used for so long I have had the bearing numbers memorized since the 1980s.

Why did you previous thread get locked? Probably turned into a typical forum cluster####?

Actually it isn't a theory, it is a statement of fact, there is little to no ground surface contacting the spindle shoulder. I didn't have an "issue" the trailer still moved down the road.

The previous thread was locked supposedly because I mentioned brakes, bearings and spindles in the same post. It wasn't up long enough for the "never-had-a-problem" folks to post their snide comments. It is one of the reasons that I gave up on starting threads. So I tried again and expect it to continue downhill.