| Using a laser level to measure caster [message #306934] |
Sun, 11 September 2016 10:11  |
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RF_Burns
Messages: 2277
Registered: June 2008
Location: S. Ontario, Canada
Karma: 3
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In straightening up the shop I came across my DeWalt self leveling laser. It Projects a laser line horizontal or vertical or both together. I got to thinking I could use this to easily check the Murray's caster to some degree of uncertainty.
I posted some photos
http://www.gmcmhphotos.com/photos/g6974-measuring-caster-with-a-laser.html
Setup the laser level for a vertical line just ahead of the front wheel. Now just measure back to the center line of the upper and lower balls joints (I used the center of the bottom of the bolts). You need to hold your measuring tape level to get a proper measurement.
Also note the point on the where you measured the center line from. You will need to measure the vertical distance between these points on the knuckle.
The photos are not the actual measurements. Hard to hold the camera, tape and read. You are only concerned with the difference between the bottom and top measurements, not the absolute measurement.
I read a difference of 2cm on the passenger side with a vertical measurement of 30.5 cm's between the ball joint bolt centers . The driver's side was 1.6cm difference with a 30 cm vertical distance. Not sure why the 0.5 cm difference, but it was a eye-ball measurement.
Using trigonometry I get 3.75 degrees on the passenger side and 3.0 on the drivers side.
Since the laser level gives a plum vertical line, I needed to compensate for the slope of the shop floor. Again using the Dewalt laser now set to a horizontal line. I measured at the rear bogie point from the floor to the laser line. Sorry for the tape being out of focus in the picture. Also measured from the floor to the laser at the front wheel.
I measured 5.9 cm difference on the passenger side which using the wheel base of 160" = 406.4cm and some trig that equals 0.79 degrees
On the drivers side it was 7cm difference which = 0.99 deg.
So my total caster passenger side = 3.75 + 0.79 = 4.59
Drivers side = 3.0 + 0.99 = 3.99
so rounding gives 4.5 and 4. and some uncertainty of maybe +/- 0.25 degrees
So by my calculations I have a fair amount of caster, however it likely should be more balanced.
What say yeah on my methodology?
Bruce Hislop
ON Canada
77PB, 455 Dick P. rebuilt, DynamicEFI EBL EFI & ESC.
1 ton front end
http://www.gmcmhphotos.com/photos/showphoto.php?photo=29001
My Staff says I never listen to them, or something like that
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| Re: Using a laser level to measure caster [message #307026 is a reply to message #306934] |
Mon, 12 September 2016 08:45  |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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Senior Member |
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Seams like a larger L to R difference than I would like. So then you have to settle for best attainable so maybe 4.0 to 4.25. Unless it doesn't pull then leave it unless camber is not zero. Any of these tweeks need to be followed by rechecking the toe. The trade off is you can only add so much caster before camber starts to go neg, then you have to stop and one side will limit you. I don't know about the math as I have the Jerry Work kit.
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: [GMCnet] Using a laser level to measure caster [message #307033 is a reply to message #307026] |
Mon, 12 September 2016 09:07 |
Ken Henderson
Messages: 8726
Registered: March 2004
Location: Americus, GA
Karma: 9
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Senior Member |
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Bruce,
The theory and procedure seem good. I'm not sure it's as easy as measuring
camber with the wheels turned, but it's probably more accurate. It would
be interesting to compare the two methods, but your level doesn't have a
digital readout, does it?
Maybe we could check with both your equipment and mine at Mansfield?
Ken H.
On Mon, Sep 12, 2016 at 9:45 AM, John R. Lebetski
wrote:
> Seams like a larger L to R difference than I would like. So then you have
> to settle for best attainable so maybe 4.0 to 4.25. Unless it doesn't pull
> then leave it unless camber is not zero. Any of these tweeks need to be
> followed by rechecking the toe. The trade off is you can only add so much
> caster before camber starts to go neg, then you have to stop and one side
> will limit you. I don't know about the math as I have the Jerry Work kit.
> --
> John Lebetski
> Woodstock, IL
> 77 Eleganza II
> Source America First
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
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Ken Henderson
Americus, GA
www.gmcwipersetc.com
Large Wiring Diagrams
76 X-Birchaven
76 X-Palm Beach
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| Re: Using a laser level to measure caster [message #307035 is a reply to message #306934] |
Mon, 12 September 2016 10:06 |
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RF_Burns
Messages: 2277
Registered: June 2008
Location: S. Ontario, Canada
Karma: 3
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Senior Member |
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Ken,
I'm just using the laser level to set a perpendicular line to measure the distance back to the upper and lower ball joints. Taking the difference between these 2 measurements, plus the vertical between the two points on the knuckle, I can use trigonometry to calculate the caster in degrees.
In my neck of the woods they would not allow me to pour a level shop floor, it must slope towards the overhead doors. So I again used the laser level to measure the slope between the front and back wheels on each side and added that to the measurement to get my actual caster value.
The laser I'm using has no readouts. It just gives a horizontal or vertical "level" laser line.
It was fast and easy if you have something similar.
Bruce Hislop
ON Canada
77PB, 455 Dick P. rebuilt, DynamicEFI EBL EFI & ESC.
1 ton front end
http://www.gmcmhphotos.com/photos/showphoto.php?photo=29001
My Staff says I never listen to them, or something like that
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