Projects Soft axle? What's going on here?

You guys geeze
Ok soft is the wrong word???
Aluminum is soft
Lead is soft
Gold is soft
Brass is soft
Toilet paper is soft too, but im sure this thing is not worthy of wiping my ass with.


Maybe I should have said flaccid instead of soft- not to be confused with placid because this thing gets to some groovy gyrations once you get it excited. It might be more fun for yous, or you'uns probably a y'all in there as well.



The funny thing is, I'm not sure what color to paint it yet.

 

i wonder if you could test the "flex" by clamping both bell axles in a vice, in the same place on one end. then add a little weight and measure the deflexion of both of them?

 

Or remove the axle, put it in a press all different ways and watch the guage when you apply pressure noting at what pressure it deflects and how much. ?? I don't know how much pressure it takes for a certain metal composition of axle but a stock ford axle could be used for comparison maybe? Then again it could just be junk . Lippy

 

Metal flexes when you apply force. How much it flexes depends on shape, how thick and long it is, and how much force you apply. Steel axles flex. Cast axles flex. It's normal behavior.

 

Pitch that baby and get one of those trick dropped tube axles from the Bchopit guy on the Gasser thread

He can build you anything you want, they are bullet proof and great weld beads as he knows his stuff

DND

 

If that amount of movement truly is normal then I need a different plan here.

Actually I'll need to rethink my very existence.
If the wheel base can vary up to 3/8 of an inch at its whim or its own discretion why bother getting it right. If the camber can change by a couple degrees on each side any time it wants to why bother measuring it. When the camber changes thru the king pins it takes the toe with it so why bother with setting that?

How much force for the deflection?
There's an equation in here someplace.
It takes approximately 5lbs of force into a 15" diam steering wheel. Coupled to a mopar manual box( not sure of the ratio. 6" pitman arm and the steering arm is 7" out by 5" up.

What I can say is that axle flexes all of its flex that's measured here in the pics before the wheels begin making any motion to turn. The other way I see that is that the wheels are free to do what they want within that flex zone before the steering wheel has any input towards control of the wheels. Like hurting cats.
Tires have a 5" contact patch.

 

Forged axles do that. Set it on the floor and turn it hard to the left. You will notice that the left part of the axle from the kingpin outward is bent forward and the axle on the pass side will be bent backwards.

 

Like a wet noodle! I would send it to Super Bell to see what they have to say. I'm sure they rather that than have their product come apart on the road potentially killing someone. Are these axles cast in the USA?

 

That would make a mean crossbow.

 

My thoughts exactly.

 

It's really difficult for us to see what's happening. We can't watch how every part is moving, and you probably can't either, because you can't be everywhere at once observing, while you're moving the steering wheel. Instead of rethinking your existence, look at each part, while someone else moves the steering wheel, and see what is moving or twisting, and how much. Maybe there's something loose? Think about the loads on the axle, is the movement appropriate for that much load?

 

Sorry I didn't understand fully before hand with my earlier reply . But there is something to be said as mentioned before by others about such an offset as you've replicated. Just for sh**'s and giggle's as a test. Try a normal steering arm and mock up some type of drag link that will work well enough for just testing to see if this doesn't happen any more.

 

I understand that, but I also believe that common sense should be applied as part of eliminating the variables to some degree to be more expedient. You can always go back to something you might skip over if all else fails. And that was kind of my point here - he is describing a major amount of movement and my feeling is a hairline crack would not cause that ~ it would be more than that to create what it seems to me he is describing. If nothing else finds the cause and effect, then he can still always maganflux the axle - and maybe that will be the cause - but i don't think so from the facts I have read so far. Just another way to go about solving the problem.

 

The axle stiffness is more due to geometry of the design than elastic modulus. Yes, steel is higher modulus than aluminum. Steel is approx 3x higher, or can also be interpreted as 3x stiffer given the same geometry.

I think you may have movement in other areas, but also agree that some flex of the axle is expected and normal. The key is to figure out each joint area, or metal area, and how each is contributing to the ultimate flex at the wheel.

 

Okay, so after reading all of this I know all axles flex. My question is, if Car A left the West side of town at the same time Car B left the East side of town, who's axle would have flexed more by the time they met in the center of town?

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An I beam axle has little torsional stiffness...and things like the drop, and the raised steering arm, put a lot of torsional load on the axle.

Good points

 

Guess I'll not drop the axle on my '40

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All I beam dropped axles flex, Henry Ford's and aftermarket.
What you are seeing is not unusual.
Looking at the pictures, I'd be more concerned with the "bump steer "
created by the hairpins & cowl steering.

 

PWood from the pictures I see that the steering arm and the hairpins are close to the same arc so maybe "Bump Steer" will be at a minimum. No?

 

My grandma left some Double Bubble in her candy dish long enough to gain a Rockwell hardness of HRC 62 and when 43 kilograms of bite force was applied, involuntary tooth loss resulted.

 

Methodical process of elimination has begun.

Swapped out the front end, and measured movement , It's about 1/2.
Swapped out steering arm and movement dropped 1/2 again. So about 75% less movement.
At this point it drove fine and without issue.

That tells me that the 2 axles are indeed different. However that's an entire front end swap not just the axle. That also tells me the steering arm contributes some. The amount depends on the elasticity of the axle.

So swapping back in the offset steering arm now.

I'll report that test drive experience.

 

Agreed that I beam axles will twist and flex as part of their makeup.
To fix/eliminate or reduce this put in a front panhard bar or a dead perch on one end of the spring instead of a shackle.

 

Im thinking you start looking at everything so close because of some "death wobble" driving issues? if not, don't bother reading my noise.

I got quite a few hours chasing steering oscillations on different applications and have come to the conclusion its never 1 or 2 things, its how everything works together. Some cars like alittle pre-load on balljoint/king pins, some it don't matter at all. some need 6 or so minimum caster, but I've seen them drive fine a 0-2 degrees. toe-in/tire diameter/wheel offset in the wrong (or perfect) combination can cause it also.

 

Went for a ride with the different front end set up and the raised steering arm.
And It drove fine.
Brought it back in tweaked the caster and then it drove great.

We dissected the first axle ( the one pictured in first posts) and went over everything with a really fine tooth comb. Here's what we found,,,,

The first axle does flex more than the other.
I know There's at least 5 years difference between the purchase of them. Not sure how long between manufacture dates but I'd guess it's a bit more. maybe there was a manufacturing change in that time frame?

The first axle's perch holes and pins are a little sloppy by a few thousandths.

The first axles king pins have a few thousandths more slop to them than I'd like. I'm very puzzled as to why I couldn't tell when assembled but it's easy to feel this slop when broken down on the bench. It was here but I didn't put this assembly together. It came out of the box brand new and went together .

The pins drop right in just like you dropped them on the floor. I usually like to have two thumbs pressure to get them started and a rubber mallet tap to send them home. Without the brake assembly on the spindles the king pins push right up with pinky pressure. In a relative way they fit like a hot dog down the hallway. The only thing I can possibly figure is that the pin/ spindle bearing masked the movement from me when assembled.

If it smells like king pin bushing it probably is

 

I figured there might be a better explanation, than the axle being made of bubble gum. Thanks for the report

 

Just goes to show you theres always an answer, sometimes just takes a bit to find it. Glad you got it handled. Lippy

 

The word "flacid" would have doomed this thread.

 

I had a Super Bell axle break in the 80s. I had picked up the axle at the Suber Bell store. I think it was in Fresno. The axle broke near the center. The steering arms also failed. Super Bell replaced the axle and i then put a Mor-drop axle in its place.
The axle came with 2 1/2 " spring perch pin width that I had cut to 2" for my 36 ford. The machinist told me that he wouldn't put the axle on any thing he was riding in because it was too soft. He was right.

 

Years ago my '33 Ford with a nicely done dropped Ford axle and an F1 box had the same flex (displacement of the top of the kingpin) when turned. It never manifested itself as shimmy or wobble but it didn't look right to me even at 20 years of age. I considered having the top of my kingpins drilled and adding Heim joints and a support strut the same length as my split 'bones. Instead, I pulled the whole mess and went with IFS. Over the years I have come to realize that they all flex to a certain extent, especially when the car's not moving.
This looks like the perfect storm for axle failure; a deep drop ductile iron axle with a tall rise steering arm and longitudinal steering. I would swap in a forged axle and reduce the height of the steering arm to the minimum required or change it to cross steering.
Sounds like you found the problem. Thanks for posting this obviously frustrating scenario. Interesting that you found fundamental differences in axles that were made at different times. I'm glad you caught this when you did or we might have been reading another "Rebuilding after the Crash" thread.