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Old 02-15-2007, 05:56 PM   #1
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Default Calculating static Camber and toe

As fast as eye balling the wheels and setting the alignment is, it's not quite accurate. If you're like me and don't want to fork out $100+ for an alignment rack then we must find other alternatives.

I was thinking I could calculate the front wheel's static negative camber and toe using trig. Check my method to see if it's accurate.

Measurement of total wheel/tire diameter = 2.557"

Assuming I have the car on a flat surface, I take the end of my dial micrometer and measure from the ground to the top of the wheel--keeping my micrometer edge perpindicular to the ground, I get 2.487"

Then drawing a right triangle using 2.557" for the hypotenuse, and 2.487" for the adjacent leg, I can use the inverse cosine to solve for the negative camber.

Neg camber = acrcos(2.487"/2.557")= 0.234 degrees

Now I can adjust the camber turnbuckles, and make the measurements again, until I get the desired negative camber.
-------------
Does this work?

--------------------
As for the front toe out, this was a little more involved:

I measured the front inside distance between the front two tires: (5.281")
Measuring the back inside distance between the front two tires: (5.254")
Total diameter of wheel/tire assembly = 2.557"

Then I draw a trapazoid diagram with the 5.254" side on top, and 5.281" as the bottom side.
5.281"-5.254"= 0.027"

0.027" is how much longer the bottom side of the trapazoid is. Dividing 0.027" by 2, I get 0.0135". (This is toe out distance the wheel is from straight ahead.)

Now drawing my triangle putting 2.557" as a leg (wheel dia.) and 0.0135" as the other leg, I can use the inverse tangent to find the angle.

toe out = acrtan(0.0135"/2.557") = 0.302 degrees.
-----------------------------------

Obviously 0.302 degrees toe out is too little toe out, so I'll probably try to get it to 1 degree or so.
Negative 0.234 degrees of camber probably is probably WAY too little for an agile car, so I'll probably try to get that closer to 1.5 degrees.

Sorry for all of the boring math.
What do you guys think? How do you dial in alignment?

Thanks!

-Andrew
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Old 02-15-2007, 06:33 PM   #2
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Default Eye ball ........

I know for a fact that most not all paid drivers DONT use set-up stations, they use there eyes with a straight edge like a droop gage..

Set up stations are wack, they are no good after you put your racing tires on and check your car ..

I call tell by my eye how much 1 or 2 degrees of camber is when the car is at rest with all racing gear on the car..

No one has a better eye at this than Chris Tosolini ..

When you have your car race ready , motor, batteries, and tires on the car use a straight edge to check your camber all around.

Check it..

side note: its an R/C car its not rocket science..
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Old 02-15-2007, 06:36 PM   #3
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Quote:
Originally Posted by PseudoScience
As fast as eye balling the wheels and setting the alignment is, it's not quite accurate. If you're like me and don't want to fork out $100+ for an alignment rack then we must find other alternatives.

I was thinking I could calculate the front wheel's static negative camber and toe using trig. Check my method to see if it's accurate.

Measurement of total wheel/tire diameter = 2.557"

Assuming I have the car on a flat surface, I take the end of my dial micrometer and measure from the ground to the top of the wheel--keeping my micrometer edge perpindicular to the ground, I get 2.487"

Then drawing a right triangle using 2.557" for the hypotenuse, and 2.487" for the adjacent leg, I can use the inverse cosine to solve for the negative camber.

Neg camber = acrcos(2.487"/2.557")= 0.234 degrees

Now I can adjust the camber turnbuckles, and make the measurements again, until I get the desired negative camber.
-------------
Does this work?

--------------------
As for the front toe out, this was a little more involved:

I measured the front inside distance between the front two tires: (5.281")
Measuring the back inside distance between the front two tires: (5.254")
Total diameter of wheel/tire assembly = 2.557"

Then I draw a trapazoid diagram with the 5.254" side on top, and 5.281" as the bottom side.
5.281"-5.254"= 0.027"

0.027" is how much longer the bottom side of the trapazoid is. Dividing 0.027" by 2, I get 0.0135". (This is toe out distance the wheel is from straight ahead.)

Now drawing my triangle putting 2.557" as a leg (wheel dia.) and 0.0135" as the other leg, I can use the inverse tangent to find the angle.

toe out = acrtan(0.0135"/2.557") = 0.302 degrees.
-----------------------------------

Obviously 0.302 degrees toe out is too little toe out, so I'll probably try to get it to 1 degree or so.
Negative 0.234 degrees of camber probably is probably WAY too little for an agile car, so I'll probably try to get that closer to 1.5 degrees.

Sorry for all of the boring math.
What do you guys think? How do you dial in alignment?

Thanks!

-Andrew
If you don't want to spend alot of money on a set-up station. For $20.00, you can buy a ride height guage and camber guage fron rpm. Your math just takes way too long to figure out at the track.
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Old 02-15-2007, 06:39 PM   #4
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an oldschool trick we do when we set-up 1:1 cars on the track without the benefit of expensive and bulky laser alignment rigs is a long piece of nylon sting. we just wrap the sting around the car centered on the wheel hub. you can then check wheel toe depending on how far the front or rear of the tire is from the string. works on camber as well (how far or near the top of the tire is to the string). might not be exact but you could check your tires for wear and determin if you need more or less camber.
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Old 02-15-2007, 06:56 PM   #5
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Quote:
Originally Posted by CAlbrecht
side note: its an R/C car its not rocket science..

Tell that to the guys with their TRF 415's with tire warmers, tire balancers, and Lipo saddles, sick brushless motors, and infared laser thermometers.


Anyway, I guess my mechanical engineering major is making me too much of a tech-nerd.
I've heard about the plum and string method too, I'll look into that.
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Old 02-15-2007, 06:59 PM   #6
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[QUOTE=VooDooPH]an oldschool trick we do when we set-up 1:1 cars on the track QUOTE]


Hey VooDooPH, in what part of the Phillipines were the tracks? I have family in Manila and Luzon and visit the PI sometimes.
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Old 02-15-2007, 07:07 PM   #7
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[QUOTE=PseudoScience]Tell that to the guys with their TRF 415's with tire warmers, tire balancers, and Lipo saddles, sick brushless motors, and infared laser thermometers.

Look at the results over the last year at ALL big races were are the TRF guys at.? Buying all the crap that wont help you at all, its all driver and not what everybody is running.

Temp gun is the second most useful item to check camber overall..

I only use a temp gun when my tire wear is really bad, other than that use your eye BALL.


Racers tip of the day...Dont buy Tamiya's if you want to run with the Big Boys..
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Old 02-15-2007, 08:02 PM   #8
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Quote:
Originally Posted by CAlbrecht

Racers tip of the day...Dont buy Tamiya's if you want to run with the Big Boys..
Here's a video of the TITC 2006 Modfiy A Main, with Marc Rheinarc driving a TRF 415 beating Andy Moore driving a cyclone.

http://www.youtube.com/watch?v=zDxXB5PrSD0

Here's the standings:

FINAL :: 19 Feb 2006 :: MODIFIED
Pos No. Name Total Points Final 1 Final 2 Final 3 Car
1 2 MARC RHEINARD 20 9 10 10 TAMIYA TRF 415 MSX
2 1 ATSUSHI HARA 19 10 9 9 HB CYCLONE
3 3 ANDY MOORE 16 8 8 8 HB CYCLONE
4 4 SURIKARN C. 14 7 6 7 HB CYCLONE
5 10 THOMAS PUMPLER 13 3 7 6 HB CYCLONE
6 7 TAKASHI KATO 10 2 5 5 YOKOMO BD
7 9 PAPHON C. 8 4 4 4 TAMIYA TRF 415 MSX
8 HIROSHI KAMIBAYASHI 8 5 3 3 HB CYCLONE
9 5 KAZUO MURAMATSU 8 6 1 2 HB CYCLON
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Old 02-15-2007, 08:32 PM   #9
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If you do your calculations for a triangle with one side being 12", its a lot more accurate to lay a ruler along the edge of the front wheel.
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Old 02-15-2007, 08:51 PM   #10
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Quote:
Originally Posted by PseudoScience
Here's a video of the TITC 2006 Modfiy A Main, with Marc Rheinarc driving a TRF 415 beating Andy Moore driving a cyclone.

http://www.youtube.com/watch?v=zDxXB5PrSD0

Here's the standings:

FINAL :: 19 Feb 2006 :: MODIFIED
Pos No. Name Total Points Final 1 Final 2 Final 3 Car
1 2 MARC RHEINARD 20 9 10 10 TAMIYA TRF 415 MSX
2 1 ATSUSHI HARA 19 10 9 9 HB CYCLONE
3 3 ANDY MOORE 16 8 8 8 HB CYCLONE
4 4 SURIKARN C. 14 7 6 7 HB CYCLONE
5 10 THOMAS PUMPLER 13 3 7 6 HB CYCLONE
6 7 TAKASHI KATO 10 2 5 5 YOKOMO BD
7 9 PAPHON C. 8 4 4 4 TAMIYA TRF 415 MSX
8 HIROSHI KAMIBAYASHI 8 5 3 3 HB CYCLONE
9 5 KAZUO MURAMATSU 8 6 1 2 HB CYCLON
Big deal dood...If your dad was the Tamiya importer in Germany you would have run Tamiya dont you think..Marc can drive a shoe box any time any day and still be in it..R/C is 95% driver you do the math..

On a club level Tamiya's are for the enthuesist (sp) when its your job to drive for Tamiya its all about the Money.

Team Orion will be in Chapter 11 in the next couple of years when all there drivers are gone..If your company dont have a face you cant sell anything..

You can thank Oscar for Rienhart going to Checkpoint ..
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Old 02-15-2007, 09:24 PM   #11
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You're right about the marketing and promotion. Right now it's the lower center of gravity thing.
So...there's nothing in engineering in these tamiya's? Uh huh.

And I actually do appologize for the math stuff guys, i'll try to illustrate it better next time.

Iceracer, with the ruler method, is that for measuring camber or toe? I was thinking a protractor sitting behind a translucent ruler would work well.

Thanks for the replies guys!
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Old 02-15-2007, 10:51 PM   #12
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Quote:
Originally Posted by PseudoScience
Hey VooDooPH, in what part of the Phillipines were the tracks? I have family in Manila and Luzon and visit the PI sometimes.

OT: I'm from Manila. we have a couple of tracks here (Speedzone at The Fort, and JP Raceway along C5).
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Old 02-16-2007, 12:09 AM   #13
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Quote:
Originally Posted by PseudoScience
As fast as eye balling the wheels and setting the alignment is, it's not quite accurate. If you're like me and don't want to fork out $100+ for an alignment rack then we must find other alternatives.

I was thinking I could calculate the front wheel's static negative camber and toe using trig. Check my method to see if it's accurate.

Measurement of total wheel/tire diameter = 2.557"

Assuming I have the car on a flat surface, I take the end of my dial micrometer and measure from the ground to the top of the wheel--keeping my micrometer edge perpindicular to the ground, I get 2.487"

Then drawing a right triangle using 2.557" for the hypotenuse, and 2.487" for the adjacent leg, I can use the inverse cosine to solve for the negative camber.

Neg camber = acrcos(2.487"/2.557")= 0.234 degrees

Now I can adjust the camber turnbuckles, and make the measurements again, until I get the desired negative camber.
-------------
Does this work?

--------------------
As for the front toe out, this was a little more involved:

I measured the front inside distance between the front two tires: (5.281")
Measuring the back inside distance between the front two tires: (5.254")
Total diameter of wheel/tire assembly = 2.557"

Then I draw a trapazoid diagram with the 5.254" side on top, and 5.281" as the bottom side.
5.281"-5.254"= 0.027"

0.027" is how much longer the bottom side of the trapazoid is. Dividing 0.027" by 2, I get 0.0135". (This is toe out distance the wheel is from straight ahead.)

Now drawing my triangle putting 2.557" as a leg (wheel dia.) and 0.0135" as the other leg, I can use the inverse tangent to find the angle.

toe out = acrtan(0.0135"/2.557") = 0.302 degrees.
-----------------------------------

Obviously 0.302 degrees toe out is too little toe out, so I'll probably try to get it to 1 degree or so.
Negative 0.234 degrees of camber probably is probably WAY too little for an agile car, so I'll probably try to get that closer to 1.5 degrees.

Sorry for all of the boring math.
What do you guys think? How do you dial in alignment?

Thanks!

-Andrew
Simple and Cheap!
Get an old "cigarette packet" and lay it up against the wheel with your chassis on a table.
Then check the gap at the top (hopefully) of the wheel; 1mm gap is a ballpark 1' Negative Camber, 2mm gap is 2' Neg, 3mm gap is 3' Neg.
Surprising how accurate this is, also requires minute brain power.
Once you have this fantastic set-up tool in the pit box you'll never go back.

This setup tool can also be used to measure "toe in", by taking off the front bumper of your car and standing it vertically on your table with the wheels touching, you can measure by the same method the toe in and toe out.

And an added bonus for someone such as yourself studying mech eng; make a close inspection of that new set-up tool. Upon consideration you will certainly appreciate the level of precision required to emboss, print, cut and fold that little packet in about 0.5 of a second. Certainly more technology goes into producing that little cardboard throwaway packet than most RC parts.

Regards,
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Old 02-16-2007, 03:47 AM   #14
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Quote:
Originally Posted by Matt Dall
Simple and Cheap!
Get an old "cigarette packet" and lay it up against the wheel with your chassis on a table.
Then check the gap at the top (hopefully) of the wheel; 1mm gap is a ballpark 1' Negative Camber, 2mm gap is 2' Neg, 3mm gap is 3' Neg.
Surprising how accurate this is, also requires minute brain power.
Once you have this fantastic set-up tool in the pit box you'll never go back.

This setup tool can also be used to measure "toe in", by taking off the front bumper of your car and standing it vertically on your table with the wheels touching, you can measure by the same method the toe in and toe out.

And an added bonus for someone such as yourself studying mech eng; make a close inspection of that new set-up tool. Upon consideration you will certainly appreciate the level of precision required to emboss, print, cut and fold that little packet in about 0.5 of a second. Certainly more technology goes into producing that little cardboard throwaway packet than most RC parts.

Regards,


I am on the ground laughing my guts out

because its so true!!!!!!!!!!!!!!!!!!!!!!!
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Old 02-16-2007, 11:14 AM   #15
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Quote:
Originally Posted by PseudoScience

As for the front toe out, this was a little more involved:

I measured the front inside distance between the front two tires: (5.281")
Measuring the back inside distance between the front two tires: (5.254")
Total diameter of wheel/tire assembly = 2.557"

Then I draw a trapazoid diagram with the 5.254" side on top, and 5.281" as the bottom side.
5.281"-5.254"= 0.027"

0.027" is how much longer the bottom side of the trapazoid is. Dividing 0.027" by 2, I get 0.0135". (This is toe out distance the wheel is from straight ahead.)

Now drawing my triangle putting 2.557" as a leg (wheel dia.) and 0.0135" as the other leg, I can use the inverse tangent to find the angle.

toe out = acrtan(0.0135"/2.557") = 0.302 degrees.
-----------------------------------
Thanks!

-Andrew
Andrew, I think you may have made an error in your calculation of Toe, please see the attached pictures. You put the overall tire size as a leg of the triangle, when I think it really should be the hypotenuse.

Also, all these values are effected by where a measurement is taken. I agree with the other posts that you should look into getting an inexpensive RPM gauge, as it is much easier to get a quick angle measurement than breaking out your trig.

Nick Malinoski
Attached Thumbnails
Calculating static Camber and toe-slide1.jpg   Calculating static Camber and toe-slide2.jpg  
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