Chenowth Explorer A-Arm Build

jim.fernish · Post by **jim.fernish** » Fri Feb 10, 2012 9:46 pm

Devastator wrote:FWIW, I have 7 deg. caster and 0 deg camber throughout full travel, and a 10 deg. KPI. My arms do, however, swing slightly forward as they go up.

I am new to this topic, go easy on me. You stated that 0 deg of camber and the spindle has 10 deg, does this mean the wheel starts at 10 deg of camber and holds this angle thought out the motion from full droop to full bump? From viewing the photos of the chenowth frame, it appears that the bolt holes are angled at both the front and side where the A-arms connect the the frame. I was guessing the offset bolt holes will cause the camber & caster the change as wheel moves from full droop to full bump. Is this a proper assumption?

59Bisquik · Post by **59Bisquik** » Fri Feb 10, 2012 10:23 pm

Probably a proper assumption. Looks like it should swing in a slight arch.

Devastator · Post by **Devastator** » Sat Feb 11, 2012 6:50 am

I don't want to hijack this thread or anything, but I'll answer your question the best I can.

jim.fernish wrote:I am new to this topic, go easy on me. You stated that 0 deg of camber and the spindle has 10 deg, does this mean the wheel starts at 10 deg of camber and holds this angle thought out the motion from full droop to full bump? From viewing the photos of the chenowth frame, it appears that the bolt holes are angled at both the front and side where the A-arms connect the the frame. I was guessing the offset bolt holes will cause the camber & caster the change as wheel moves from full droop to full bump. Is this a proper assumption?

I was referring to the A-arms i built for my sandrail. The wheel is not at 10 degrees per se. The KPI, (king pin inclination angle), is at 10 degrees. So long as your mounting holes at the opposite end of the A-arms is at the same angle as your KPI, the arms will not change in camber as the swing up and down. My arms swing slightly forward, however, because of my rear mounting location. I don't think that the frame in this build thread will have that issue quite as pronounced as I do. Also, as long as the same caster present at the spindle is incorporated in the A-arm mounting points, it will not change as the arms cycle. Avoiding bump steer is, IMHO, the most challenging part of building an A-arm setup.

jim.fernish · Post by **jim.fernish** » Sat Feb 11, 2012 8:44 am

Devastator & 59Bisquik, thanks for sharing your experiences with your projects. I am going to convert my sand rail from a stock VW beam style to A-arm style and have been following your projects. I am trying to take what your both have learned and apply this to my own project. I hope my asking questions is not considered to be hijacking this thread.

Devastator · Post by **Devastator** » Sat Feb 11, 2012 8:52 am

jim.fernish wrote: I hope my asking questions is not considered to be hijacking this thread.

I think that Q&A is what we are all here for. I just felt weird answering questions about my sandrail on 59's thread.

59Bisquik · Post by **59Bisquik** » Sat Feb 11, 2012 9:11 am

Its all good guys! We are all here to learn and build!

Getrdone · Post by **Getrdone** » Sat Feb 11, 2012 8:31 pm

just FYI for someone who may be going to mock up on this type of design. It is common on sand to due the track width changes inherent in that setup. Sand allows the spindles to survive and not get folded under at travel limits. All the types of arm design and give and take are purpose built. Of the failures I have seen with that type of design (not cheno though) have been at the HAZ area of the upper arms fore/aft bar. A gusset here would cure it. Before you final weld, let us know how it cycles. I would shoot for some camber gain.

Devastator · Post by **Devastator** » Sun Feb 12, 2012 8:04 pm

Getrdone wrote:just FYI for someone who may be going to mock up on this type of design. It is common on sand to due the track width changes inherent in that setup. Sand allows the spindles to survive and not get folded under at travel limits. All the types of arm design and give and take are purpose built. Of the failures I have seen with that type of design (not cheno though) have been at the HAZ area of the upper arms fore/aft bar. A gusset here would cure it. Before you final weld, let us know how it cycles. I would shoot for some camber gain.

All of the unlimited off road cars run A-arms.

jim.fernish · Post by **jim.fernish** » Mon Feb 13, 2012 3:12 pm

Hey 59Bisqulk, would you mind measuring your a-arm frame holes for the front and side of your frame? Earlier you said the front top holes were 11" apart & bottom holes were 9.5" apart making an offset of 3/4" if I am understanding the prior post. What is the virtical distance between the holes? Would you also provide the horizontal and vertical distances for the a-arm holes on the side of the frame? Lastly, what is the length of the side a-arm, assuming the measurement was at a 90 degree angle to the front arm? I would like to model your values in the a-arm suspension geometry calculator at http://www.racingaspirations.com/?p=286
Thanks

Getrdone · Post by **Getrdone** » Mon Feb 13, 2012 5:01 pm

Devastator wrote:
Getrdone wrote:just FYI for someone who may be going to mock up on this type of design. It is common on sand to due the track width changes inherent in that setup. Sand allows the spindles to survive and not get folded under at travel limits. All the types of arm design and give and take are purpose built. Of the failures I have seen with that type of design (not cheno though) have been at the HAZ area of the upper arms fore/aft bar. A gusset here would cure it. Before you final weld, let us know how it cycles. I would shoot for some camber gain.
All of the unlimited off road cars run A-arms.

Dev, I am refering to parallel fore aft a-arm setup.

59Bisquik · Post by **59Bisquik** » Mon Feb 13, 2012 5:09 pm

The vertical distance between the holes on the front of the frame is 6 3/4"
The vertical distance between the holes on the side of the frame is 6 3/4" with an offset of 1 3/4" (lower is forward)
The side arms measure at 27 1/2
The spindle is 3/4" wider at the bottom and a 7 1/2" spacing
Top arm is 24" with the bungs and bottom is 26" with bungs

Getrdone · Post by **Getrdone** » Mon Feb 13, 2012 5:38 pm

The only two a-arm failures I have seen at Ocotillo have been here.

Devastator · Post by **Devastator** » Mon Feb 13, 2012 7:31 pm

Getrdone wrote:The only two a-arm failures I have seen at Ocotillo have been here.

Maybe I should add a gusset there on mine.

Getrdone · Post by **Getrdone** » Mon Feb 13, 2012 8:04 pm

There are some cooler gussets out there, just cant find them now.

jim.fernish · Post by **jim.fernish** » Mon Feb 13, 2012 10:13 pm

59Bisqulk,
I converted the values you provided into the a-arm suspension geometry calculator. It appears the camber does not change much (1 or 2 degrees) when cycling the arms with 15 inches of travel. How much camber are you getting at full droop and amount of change are you seeing when cycling the arms? What amount of travel are hopping to get?
Thanks, Jim

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