| [GMCnet] Alignment kit nearing completion [message #140021] |
Fri, 19 August 2011 13:19  |
glwgmc
Messages: 1014
Registered: June 2004
Karma:
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Senior Member |
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I am just putting the finishing touches on the do-it-yourself wheel alignment kit and a paper describing how to build one. My hope is that members in our various clubs will build and donate such a kit to the club for the benefit of all their members.
In researching this topic and evaluating different components one thing has become clear. The suspension system on our coaches takes a long time to settle into the attitude it will take while being driven down the road. The work procedures used by most professional alignment shops that I have observed as part of putting this paper together involves lifting the wheels and or the coach off the ground several times during the alignment process. Most will attempt to wiggle the coach by pulling it down by hand or with some sort of mechanical device, but that is not enough to bring most of our coaches to the attitude they will eventually take in five or ten miles of driving. To the tech doing the alignment, everything can look spot on and the owner gets a false sense of precision via the printout they are handed at checkout. The problem comes in a few miles of driving when the coach suspension finally does settle in causing the alignment adjustments and specs to be off, someti
mes wildly so. All this is exacerbated by the interaction between the rear air bag auto leveling system and the front torsion bars. Rear ride height has a bigger impact on front ride height than most would imagine.
This may be a major factor in why some owners report their coaches drive easily "one finger on the wheel" while others report they wander all over the road and are blown around by passing trucks. From what I have learned so far the only way to accurately measure ride height and alignment front and rear is after the coach has been driven for five or ten miles and before the coach or the wheels are lifted off the ground. I plan to do a simple test at some upcoming rallies by measuring the front and rear ride height as the coaches come in. My guess is we will find the front and/or rear ride height way off on a large number of them. If it is, then the alignment will likely also be off. I will let you know when the numbers come in.
In the mean time, this kit is simple enough that even mechanically challenged owners can check all the key alignment specs at home or at a rally anywhere there is a reasonably level paved spot. Ride height, camber, caster, toe, steering centering and parallelism on the front wheels along with camber, toe and parallelism for the rear bogies can all be checked quite accurately without lifting the coach or the wheels off the ground using the kit. I have everything finished and tested except for the laser gun sights that will be used for testing parallelism. Those should be here next week.
BTW. I have tested a number of different manufacturer's digital angle gauges (Sears, Wixley, CMT, Bosch and some no-name cheapies) and none so far have passed the 180 degree test. If you place them on a flat surface like the machined tops on my industrial woodworking equipment and zero the meter, then turn it 180 degrees and put it back down in the same spot, the reading will be off by at least 0.2 or more degrees. Some will pass the test once in a while if you place them on a non-magnetic surface. These things will be accurate enough for our use in this kit, but don't get lulled into a false sense of accuracy just because the indicator shows tenths of a degree. Just for the record, all of my Stabula and Festool bubble levels do pass the same 180 degree test as far as my eye can discern.
Once the paper is finished I will publish it on my web site in .pdf form and give permission to bdub and mrerf to place copies on other pertinent GMC sites they deem appropriate. I will also give permission for any of the clubs to put a copy or a link in their web sites and/or news letters as well. It is copyrighted material so you will be able to build a kit for your own personal use or to donate to your club, but you will not be able to produce a version for sale without my express written consent. Thanks.
Jerry
Jerry Work
The Dovetail Joint
Fine furniture designed and hand crafted in the 1907 former Masonic Temple building in historic Kerby, OR
Visitors always welcome!
glwork@mac.com
http://jerrywork.com
541-592-5360
Founder of the Southern Oregon Guild
www.southernoregonguild.org
Member of the Siskiyou Guild
www.siskiyouguild.org
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Jerry & Sharon Work
78 Royale
Kerby, OR
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