Ideas on homemade tire alignment device

[jclaudii]

I'm sure many of you have had to get a wheel alignment on your vehicle before, and on some vehicles where there is a limited amount of adjustment that can be made it should be even easier!

I would like to start off with just a front end alignment device that is capable of telling one their Toe in/out first. After that, I would like the device to graduate to be able to find caster/camber.

For example, My Jeep has a solid straight axle and the default adjustments that are easily made are only Toe in/out. The castor and camber require more work and would be beneficial to know as well. A easy way to measure almost ANY vehicles toe in/out is to use the "string" method. This usually requires a helper and you measure a string or tape measure on the same point on the front and back of both front wheels at the exact same point...weather it is outside edge, center, or some type of bolt on device that mounts to the wheel (like a straight piece of aluminum so one can measure precisely from).

Now, I was thinking of using an arduino fro this project, but I'm not sure what components I would need. I figure I will tap into the knowledge of users here to ask what is a better distance measuring device at less than 10 feet. Would this be the easiest way and just use a laser distance measuring device or a ultrasonic device and compare the front and back distance of the two front tires together. Or would a rig of some sort that sits in front of the car and gathers the sensor data (this design is more in tune with how it is done at an alignment shop).

Anyways, I'm sure I'll have more to add soon, but wanted to get the idea started out there as soon as possible. Thanks for any and all advice!

 

[Grossel]

I'm pretty sure you know that you'll need at least one weight cell.

I'll say that the hardest part is the physics and how to use the values from the weight cell and calculate the weight.
I think that most alignment devices calculate the need for weights on both side of the tyres, wich makes it more difficult.
Therefore I'll say that you need at least two weight cells.

The second hardest part I guess is to make a shaft attached to a weight cell by a near friction free bearing.

 

[KeepItSimpleStupid]

A component to think about would be a linear photo array such as these: **broken link removed** and a laser. I belive these are available in two dimensions too.

An idea for one of them out would be something that mounts with precision shafting and a precision level. Once you have something (sliding bar)attached to say the rear wheel and level in both directions. Do the same for the front wheel with it in the center of the hub.
Move the slider up and read the position of the laser from the linear array.

This is just an idea to run with. It seems to be both mechanical and optical.

 

[unclejed613]

i once replaced a tie rod, and to keep the toe-in the same, i counted the threads on the old one, and set the new one to the same number of threads. what i didn't know is that the new part had a different thread pitch, so the wheels were toed-in about an inch. i went through 2 pairs of front tires in about a month. when i saw the knife-edging on the tread of the tire i figured out what was wrong. it took a long time of adjusting to get it right (measure, twist the coupler, measure again, etc...). i came up with an idea for a pair of laser pointers (actually laser sights for a pistol would be better because you can adjust the X/Y deflection on them ) mounted on magnetic mounts theat would seat just inside the lip of a rim. if you know the distance between the rims, , the distance the mounting points are from a facing wall, and the required toe-in (on many cars it's zero, which makes things much simpler), you can figure out where the lasers should land on the wall, put a couple of markers on the wall, and adjust until the lasers are on the marks.

the reason you may need to adjust the X/Y deflection of the beam is so that you can make sure the beam is parallel to the axis of the magnetic mount.

 

[OlPhart]

I've thought about this as a project as well... purchased systems are SO $.
It comes down to angular measuring vertical, both front/back and side/side on each side and horizontally side to side relative for the front. Rear provides relative horizontal angle front to back, for each.

Between accelerometers and laser/photo arrays, it's doable, but not trivial. G.H <<<)))

 

[unclejed613]

I'm pretty sure you know that you'll need at least one weight cell.

I'll say that the hardest part is the physics and how to use the values from the weight cell and calculate the weight.
I think that most alignment devices calculate the need for weights on both side of the tyres, wich makes it more difficult.
Therefore I'll say that you need at least two weight cells.

The second hardest part I guess is to make a shaft attached to a weight cell by a near friction free bearing.

you're thinking of tire balancing, which is a bit different...... toe-in is the one thing that is easiest to get out of alignment, since tie rods are relatively thin , and are also an item that need to be replaced more often than other front end components. it's usually the easiest to adjust. caster and camber are usually adjusted with shims, so the parts the shims go between need to be disassembled and reassembled until the correct shim thickness is found. caster and camber usually don't need readjustment unless the car has been in an accident or the ball joints have been replaced.

 

[alec_t]

I would rule out ultrasonics. The speed of sound varies too much with temperature etc, so measurements would be inconsistent. Laser alignment, as suggested above, would be preferable.

 

[jclaudii]

Are there any laser devices that are capable of measurement in the price range of the ultrasonic devices?

My next idea is going way outside the box, what about a "simple" device like a measuring string?
**broken link removed**

Basically you just run it from each side of the solid mount that is on each tire. it has some electronics that may be able to "hack" in and get some data to arduino to be able to output the fr/rear and the toe in/out reading in a +- format.

Seems castor/camber may be easier now days with the use of a 3 axis accelerometer or old wiimote hacking.