Lightnin's Simple Alignment Test

Secrets, tips, tools, design considerations, materials, the "science" behind it all, and other topics related to building the cars and semi-trucks.
Post Reply
User avatar
LightninBoy
Master Pine Head
Master Pine Head
Posts: 201
Joined: Mon Feb 20, 2012 10:09 pm
Location: St. Paul, MN

Lightnin's Simple Alignment Test

Post by LightninBoy » Sun Mar 27, 2016 10:20 pm

Hey Folks,

Several people have asked me to repost my earlier video showing the alignment test with a tuning board and square. So I made this video. Hope this helps!




Speedster
Pine Head Legend
Pine Head Legend
Posts: 1331
Joined: Sat Feb 18, 2012 2:48 pm
Location: Toledo, Ohio

Re: Lightnin's Simple Alignment Test

Post by Speedster » Tue Mar 29, 2016 11:09 am

Great job on the video. I've been using it at our workshops ever since you did the 1st video. The scouts Love it. I do too.



chromegsx
Master Pine Head
Master Pine Head
Posts: 164
Joined: Wed Jan 18, 2012 10:25 pm
Location: PA

Re: Lightnin's Simple Alignment Test

Post by chromegsx » Tue Mar 29, 2016 1:27 pm

This is a great method to help understand alignments. Wish I had it when I was first learning. could have saved me a few hours of frustration and sleepless nights right before a race or two.

Digging a little deeper into alignments. It should be noted that this makes some assumption of how high the nose of the car will sit and doesn't necessarily account for the change in toe effects of putting the dominate front wheel/axle in at the desired drift amount. So if your nose ends up a little lower or higher than this test you may be changing your rear toe angle if using canted drill job or bent axles. Great place to start though.



Speedster
Pine Head Legend
Pine Head Legend
Posts: 1331
Joined: Sat Feb 18, 2012 2:48 pm
Location: Toledo, Ohio

Re: Lightnin's Simple Alignment Test

Post by Speedster » Tue Mar 29, 2016 2:34 pm

I install the DFW and measure the height with a caliper. Remove the DFW and set the car height the same.



User avatar
Gtdhw
Master Pine Head
Master Pine Head
Posts: 113
Joined: Fri Jan 15, 2016 2:47 pm
Location: Galveston, IN

Re: Lightnin's Simple Alignment Test

Post by Gtdhw » Tue Mar 29, 2016 2:52 pm

Speedster wrote:I install the DFW and measure the height with a caliper. Remove the DFW and set the car height the same.

This is how we plan on doing our new district build in the next couple of nights, for our first try using this method.

Excellent info.


I wish I was the man that my dog thinks I am.

chromegsx
Master Pine Head
Master Pine Head
Posts: 164
Joined: Wed Jan 18, 2012 10:25 pm
Location: PA

Re: Lightnin's Simple Alignment Test

Post by chromegsx » Wed Mar 30, 2016 7:34 am

Speedster wrote:I install the DFW and measure the height with a caliper. Remove the DFW and set the car height the same.
:thumbup:



User avatar
Stan Pope
Pine Head Legend
Pine Head Legend
Posts: 6888
Joined: Sat Jul 05, 2003 7:01 pm
Location: Morton, Illinois
Contact:

Re: Lightnin's Simple Alignment Test

Post by Stan Pope » Sun Apr 03, 2016 12:06 am

I have two concerns with rear alignment that this method does not address:
1. Assurance of correct alignment of the more lightly loaded rear wheel, and
2. Assurance that the rear wheels are tracking "off the rail."

Here are proposed solutions for those concerns:

1. Since the more lightly loaded rear wheel contributes drag but not directional control, its input can be forced. Do this by running the tests with front end support pin located left of center and then right of center. (Confirm with scales that the chosen pin locations do, in fact, cause the rear weight distribution to shift sufficiently.)

If the ballast is centered, then supporting the front end left of center makes the right rear wheel dominant, and it is the one that should be adjusted to affect rear alignment. And vice versa.

You should be able to identify pin locations that are suitable for all of your cars unless you really push the CM left or right.

2. To assure that the rear is tracking correctly (off the rail), draw two lines down the board, parallel to the edge. One should mark the location where the right front wheel would be if it were guiding the car. That is used for the pin located right of center. The right rear wheel should track approximately 1/8" to 3/16" to the right of the line.

The other line should mark the location where the left front wheel would be if it were guiding the car. That is used for the pin located left of center. The left rear wheel should track approximately 1/8" to 3/16" to the left of the line.


Stan
"If it's not for the boys, it's for the birds!"

User avatar
LightninBoy
Master Pine Head
Master Pine Head
Posts: 201
Joined: Mon Feb 20, 2012 10:09 pm
Location: St. Paul, MN

Re: Lightnin's Simple Alignment Test

Post by LightninBoy » Tue Apr 05, 2016 9:54 pm

Regarding concern #1 - There are likely several improvements that could be devised to make this approach more friendly to aligning bent rear axles. I've only aligned a couple of cars with bent axles with this technique so there are probably others more qualified than I here. But the challenge I had with it was simply around isolating which axle was off and therefore knowing which to adjust. The test as shown does a good job of exposing that something is wrong, but doesn't tell you which axle to adjust. So what I did was bias the weight/pin to isolate one axle. Adjust. Then isolate the other axle. Adjust. Then center the weight/pin again to see the results. It would normally take a few attempts and still feels more like an art than a science to me.

Regarding concern #2, if this is about detecting a dog tracking alignment, then that has been easily visible when pushing it down the board and pulling it up. Backing up, in particular, is highly sensitive to it because once the car goes off angle it just gets progressively worse as you pull up. Drawn reference lines might help but don't seem necessary. I used to beam a laser down the board at the center of the car to help detect dog tracking but it never exposed anything I couldn't already see with the naked eye so I stopped doing that.

Those are my experiences. I'd be interested in hearing other's experience because I do expect there is room for improvement particularly as it applies to adjusting bent rear axles.



User avatar
Stan Pope
Pine Head Legend
Pine Head Legend
Posts: 6888
Joined: Sat Jul 05, 2003 7:01 pm
Location: Morton, Illinois
Contact:

Re: Lightnin's Simple Alignment Test

Post by Stan Pope » Tue Apr 05, 2016 10:49 pm

Great, LB!

I didn't find where you described biasing previously. :) If I understand, we described identical solutions for #1. This is important since the forward/reverse roll test is difficult with preferred tight hub-body clearance! And, I think, that test loses accuracy as the camber angle increases in magnitude. (Max V published some tests a couple years ago suggesting that increasing the camber beyond 2-1/2 degrees was advantageous.)

By moving the car body left and right on the pin you force a particular rear wheel to be dominant. Adjustment of bent axles in this procedure is always done to the dominant rear wheel. Reduces the need for "art." :)

Regarding #2, a common accident when drilling axle holes is that the drill press table has rotated slightly. Drilling against a fence produces compensating errors in each rear axle hole ... the holes are parallel to each other, but not perpendicular to the car's centerline! The result can be accidental, but otherwise excellent, dog-trot alignment which you may or may not catch "by eye"... a small error in tracking can put a rear wheel hard against the rail!

Further comparisons of methods:

1. Rear wheel load biasing can be obtained with this method without increasing the total rear end load. This would avoid flexing the axle camber angles if the body were to flex under the additional load. I have not noticed this actually happening, but it is a risk.

2. The method appears to require that the DFW be removed in order to use the method. This would be a problem if one were simply trying to prove that rear alignment was still good. By comparison, my weight biased method can use the race-ready DFW toe-in without change. However, I believe that raising the front end by 1/8" (to lift the DFW off the board) changes the rear axle angles too minutely to cause the test results to change. (Rotating the body 1/8" at 5" is 1.4 degrees. Since the rear angle changes from 0 (when the body is level) to 2.5 deg (when the car body is vertical), the error introduced in the rear axle is well less than 1.4 degrees.) I must make one of your boards to test these guestimates! :)

3. The slow motion relative to my weight biased method should be much easier to evaluate. As my eyes get older, that ease will be appreciated!


Stan
"If it's not for the boys, it's for the birds!"

User avatar
Stan Pope
Pine Head Legend
Pine Head Legend
Posts: 6888
Joined: Sat Jul 05, 2003 7:01 pm
Location: Morton, Illinois
Contact:

Re: Lightnin's Simple Alignment Test

Post by Stan Pope » Sat Apr 09, 2016 10:52 am

LightninBoy wrote:Regarding concern #2, if this is about detecting a dog tracking alignment, then that has been easily visible when pushing it down the board and pulling it up. Backing up, in particular, is highly sensitive to it because once the car goes off angle it just gets progressively worse as you pull up.
This needs to be tested. I question it because the forward pull establishes the rear wheels ready to roll straight back on the reverse roll. The body is askew, but the axles are oriented correctly for a clean backward roll!

Regarding compensating error due to drill press table not perpendicular to the quill. Yes, the axles come out parallel, but the error introduces a dog trot alignment, risking that one of the rears may not track off the rail. My spreadsheet indicates a 1 degree error in the drill press table shifts the rears 0.087" (assuming a 5" wheelbase). By comparison, indenting the DFW 1/16" produces only a 0.063" rail clearance for the wheel following the DFW. Adding in the 1/32" hub-body clearance for the rear wheel still leaves that wheel at risk. Now, admittedly, 1 degree is a pretty large error on high precision equipment, but most of us are not so well equipped!


Stan
"If it's not for the boys, it's for the birds!"

Post Reply