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Old November 11th, 2011, 09:31 AM   #1
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Default Math geeks and engineers...

So the new crawler is coming together on paper and I'm in an bind. I think my math is right but need to bounce it off some other people. Here's what I'm planing.
I going to do a horizontal watt's links mounted above the rear axle housing. The Axle have a total suspension travel of 14" 4" of compression and 10" of extension. I want to mount a 18" Dia Watt's link on the top of the axle and use 24" arms to both sides. So if you good with math/engineering keep reading.......

For 15" on travel (just a little buffer) the 24" rods should have a delta of 3.785 in length resulting in 24 deg of rotation of the watts link. The angles are important because my heims will only take 32deg before binding.
Before I cut some steel.....What's your take??
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Old November 11th, 2011, 09:41 AM   #2
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Move this to the tech section and post a layout drawing.
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Old November 11th, 2011, 09:43 AM   #3
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Or leave it here and post some pictures of your wife/girlfriend! ;)
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Old November 11th, 2011, 10:52 AM   #4
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More information needed. Total width frame mounting to frame mounting. height difference frame mounting to frame mounting (if not 0), height difference frame mounting point to axle mounting point at design height.
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Old November 11th, 2011, 10:56 AM   #5
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More data please
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Old November 11th, 2011, 11:27 AM   #6
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At ride height the laterel links will be slightly above level like +5 deg. The mounting points on the frame will be 42" apart leaving the arms to be slightly over the CL of the Watt's. This going to be mounted horizontal on the top of the Axle...Not on the rear. Raising the roll center closer to the CG to keep weight trasfer to Min. I will see if I can find some pics of what I'm thinking.
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Old November 11th, 2011, 12:03 PM   #7
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Please stop trying to describe it and lay it out.
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Old November 11th, 2011, 12:13 PM   #8
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pics or a drawing we be a visual people on gl4x4
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Old November 11th, 2011, 12:36 PM   #9
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Even more data please.
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Old November 11th, 2011, 02:07 PM   #10
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Where are the heims and how are they oriented?
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Old November 12th, 2011, 07:26 AM   #11
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Alright you asked for it..... The heims used on both end of the laterals are going to be 3/4's The heims have misalignment spacers that will allow 30deg before binding. Rotation of the watt's will be on a 9" radius. Math is included
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Old November 12th, 2011, 07:43 AM   #12
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A couple quick comments. From the "short" amount of searches I did, it seems everyone is mounting the pivot arm vertical rather than horizontal like you are and using it in a road course application. Mounting it horizontal, you add a lot more bind into the heims. I also didn't see anyone doing it in an offroad application where there is extreme articulation.

Have you searched Pirate?
Do you have any links of anyone doing it for an offroad application?
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Old November 12th, 2011, 08:12 AM   #13
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Quote:
Originally Posted by Torg38 View Post
So the new crawler is coming together on paper and I'm in an bind. I think my math is right but need to bounce it off some other people. Here's what I'm planing.
I going to do a horizontal watt's links mounted above the rear axle housing. The Axle have a total suspension travel of 14" 4" of compression and 10" of extension. I want to mount a 18" Dia Watt's link on the top of the axle and use 24" arms to both sides. So if you good with math/engineering keep reading.......

For 15" on travel (just a little buffer) the 24" rods should have a delta of 3.785 in length resulting in 24 deg of rotation of the watts link. The angles are important because my heims will only take 32deg before binding.
Before I cut some steel.....What's your take??
What was your question?
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Old November 12th, 2011, 08:13 AM   #14
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oh and you may be overthinking this a bit.
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Old November 12th, 2011, 08:18 AM   #15
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Quote:
Originally Posted by whiterhino View Post
A couple quick comments. From the "short" amount of searches I did, it seems everyone is mounting the pivot arm vertical rather than horizontal like you are and using it in a road course application. Mounting it horizontal, you add a lot more bind into the heims. I also didn't see anyone doing it in an offroad application where there is extreme articulation.

Have you searched Pirate?
Do you have any links of anyone doing it for an offroad application?
I've seen it done on some off road racing trucks. As for more of a bind in a Horz. postion. The rotation of the watt's is the same rather you mount it vertical or Horz. Just the roll center changes height by putting it on top. By putting the RC closer to CG I minizime the level arm that creates body roll in turns. The other issue is the roll steer created by using a track bar. By swapping to the Watts's I have a stright drop without the dog tracking effect of the rear bar.
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Old November 12th, 2011, 08:23 AM   #16
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http://forum.britishv8.org/read.php?7,13029
http://www.toymods.org.au/forums/tec...re-height.html
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Old November 12th, 2011, 09:16 AM   #17
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I don't think you can compare a race car to an offroad vehicle. A race car never sees that much articulation or suspension travel. Yes, I see a huge difference between vertical and horizontal.

Vertical - the watts linkage only has to compensate for one direction of travel as it compensates for suspension height and body roll. Other than a very small difference in angle, the 3 links are virtually in line when measuring front to back.

Horizontal - the watts linkage has the same motions as in a vertical position PLUS the angle change added by moving the axle up and down 14" from the frame mounts. Now you are dealing with compound angles. In addition, the long links will potentially interfere with your springs and or shocks.

If you don't like a panhard bar, why don't you just 4 link it? You have way more complexity and at this point, I don't see the advantage of it. Although you called it your crawler, you have never actually said what your intended usage for this vehicle is. The watts may be great for road racing but I don't see the benefit of it for crawling.
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Old November 12th, 2011, 10:09 AM   #18
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And to add a non engineer, but made a couple of link suspensions opinion, a properly made track bar does not allow the axle to move out of sync that much. At least not enough to notice and especially not in our application. When your one front tire is on a 4 foot rock does it really matter if your axle shifted 1/2 an inch one way or the other?
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Old November 12th, 2011, 10:25 AM   #19
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Quote:
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And to add a non engineer, but made a couple of link suspensions opinion, a properly made track bar does not allow the axle to move out of sync that much. At least not enough to notice and especially not in our application. When your one front tire is on a 4 foot rock does it really matter if your axle shifted 1/2 an inch one way or the other?
14" of travel your axle would be 2.20" shifted
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Old November 12th, 2011, 10:40 AM   #20
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Quote:
Originally Posted by whiterhino View Post

If you don't like a panhard bar, why don't you just 4 link it?
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