What's new
What's new

Squaring up trailers.

There's nothing inherently wrong with triangulation with the coupler. But cutting the tongue off to correct a miniscule error is a lot of wasted effort. Unless the couple is off center by inches, the user is never going to even notice
 
I think you missed the point and are not visualizing any of this well?

Key points-

1- side-side offset of coupler has dick to do with offset of trailer in the lane past the actual (meaningless) offset of the coupler as it relates to the centerline of the trailer.

2- The axles are squared to the trailer's frame or it's "center of mass". There's no imaginary radius from the ball coupler. That's just dumb. It adds a whole nuther level of error into the problem. Axles square to frame; trailer's travel direction will align with it's centerline.
Ha ha.

So you pulled out the “that’s just dumb”defense….

The radius from ball to center of axle isn’t imaginary.
It is specifically defined for every trailer and the error being described in this thread is that radial miss alignment on that circle.
The axis defined is 0 degrees on square to the center of a line drawn between the hub centers.

The axles are not in fact squared by necessity to the trailers frame.
What would one do if the trailer is an elliptical in shape to some degree, made with the frame elements out of parallel or any other permutations of shape.

What happens is a mechanic does in fact square to some elements of the trailers frame and the rig still crabs.
This is due to not having established the critical geometry of the coupler having minimal radial error.
Forget the frame- it is perfectly meaningless.
 
Last edited:
Ha ha.

So you pulled out the “that’s just dumb”defense….

The radius from ball to center of axle isn’t imaginary.
It is specifically defined for every trailer and the error being described in this thread is that radial miss alignment on that circle.
The axis defined is 0 degrees on square to the center of a line drawn between the contact points of the tires.

The axles are not in fact squared by necessity to the trailers frame.
What would one do if the trailer is an elliptical in shape to some degree, made with the frame elements out of parallel or any other permutations of shape.

What happens is a mechanic does in fact square to some elements of the trailers frame and the rig still crabs.
This is due to not having established the critical geometry of the coupler having minimal radial error.
Forget the frame- it is perfectly meaningless.

OK smart guy. How do you get a <.050" location measurement of the ball coupler center and the contact patch of the tires?

I said the center of mass of the trailer and using plumb bobs.

You can't effectively measure what you are talking about. You can find the center of the trailer and locate the axles square to that centerline. That's how you do it.
 
OK smart guy. How do you get a <.050" location measurement of the ball coupler center and the contact patch of the tires?

I said the center of mass of the trailer and using plumb bobs.

You can't effectively measure what you are talking about. You can find the center of the trailer and locate the axles square to that centerline. T

It is relatively easy to establish through measurements if a isosceles triangle is present in the axle(s)/coupler alignment.

What to change in a built trailer where it is not present.

Well one has to decide.

Look at it this way, one of the roles of the trailers frame is to serve as a fixture to establish and maintain the required geometry of the axle/coupler.

In this role the trailer can be of any shape (and often is..) while the axle/coupler geometry is required to hold to specific constraints.

So let me ask you.

You state:
“You can find the center of the trailer and locate the axles square to that centerline.
That’s how you do it.”

So what is done in the case where the coupler is not found on that centerline?
 
Last edited:
.

You state:
“You can find the center of the trailer and locate the axles square to that centerline.
That’s how you do it.”

So what is done in the case where the coupler is not found on that centerline?

If it's a small amount, you leave it be. 1" out isn't worth the labor of cutting a tongue off as long as the frame will stay visually in line with the lane.

3" out is worth cutting off and fixing.

If you're building from scratch, it doesn't cost anymore to make it right. If you're fixing something existing, every little thing you fix costs you customer a significant amount, so way better to charge them only for relocating spring shackles than to charge for relocating spring shackles and replacing a tongue.
 
Design and make up universal adjustable spring shackles. Have them on the shelf, customer comes in, doo the job once and done.
 
Last edited:
I believe a trailer's axle can be welded on square to the side rails, but that the whole trailer frame can be bent or out of square. This can cause the trailer to track crookedly. I have cut bent trailer frames, pulled them straight and rewelded them.

I believe by far the biggest cause of trailer oscillation is improper loading, usually with too little tongue weight.
 
Axles need to be square to the frame and parallel to each other..............that's all that matters. Coupler location will not determine if the trailer runs straight down the road..................think of a swather or a pull type chopper.............hitch is not centered and the implement pulls straight behind the tractor................
 
The axle thrust angle must be kept to very close tolerance.
That angle is what the OP is contracted to correct.

-If the trailer has straight frame elements which are parallel.
And
-If the coupler is on a centerline between those elements.

Squaring the axle to that true frame will minimize thrust angle error.
If the trailer isn’t sorted moving the axles square to its elements won’t do squat.

Forget the frame when trying to remedy dog tracking.
Figure the trailer is a disk with an axle mounted to it.
Verify the error in thrust angle FIRST and then look to how to correct it.
 
Last edited:








 
Back
Top