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Unread 03-01-2013, 02:25 PM   #241
sirhk100
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Quote:
Originally Posted by Sundowner View Post
It's like a Watts linkage running longitudinally...
I guess???? Not really...



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Unread 03-01-2013, 02:47 PM   #242
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Unread 03-01-2013, 03:21 PM   #243
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Quote:
Originally Posted by sirhk100 View Post
????? Looks like a Currie housing or similar with a rotated center section. The pinion angle is probably fine. I'm not trying to say I know all or anything by anymeans but I'm having a really hard time seeing the issues with that rear setup. Everything there looks good in my eyes with exception of I don't see bumpstops and personally am not a fan of using my shocks as my limiters.
As the axle moves, the axle end of those arms are going to spread apart or come together. The pinion is forced to rotate up or down accordingly. In that particular rig, the limit strap probably keeps the pinion from getting too far out of line on droop. I'm sure it could be engineered to keep the pinion in perfect alignment. I can't say for sure how it will react to off-camber articulation, but in my head I don't see it working too well. Basically on one side the axle wants to rotate clockwise, and the other side want to rotate counter-clockwise.

Imagine this animation happening in opposite direction on a rigid body.
watts_linkage.gif  
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Unread 03-01-2013, 03:56 PM   #244
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I can see what you're showing in that animation but you also look to be heavily exaggerating the amount of vertical travel the center of the axle would see (not counting articulation) Just roughly holding me fingers to the screen you're showing a vertical travel of something equivalent of the length of the link arms which I just don't see being realistic. Like I said, I have nothing to base on other then that picture posted but I'm betting the 10-12" of vertical travel that thing sees, the pinion angle doesn't change enough to harm it. As for the pinion on articulation, I don't see how it would be any different then a standard link setup. They all tend to duck walk, especially when you get into the 20+ inch travel range. (I own a 3 linked truck pulling 23" all home built for reference) The axle is still going to pivot around that upper link point and it really I think would still work the same. With the fuel tank being a physical block for where the links would need to run this in my eyes seems like a very viable alternative.

Like I said, I know for a fact it's been done before very successfully so I'm not sure why it couldn't be applied to the confines of a Jeep. I'm guessing that's a 4door JK and not wanting to deal with gas tank solutions it seems like a great alternative.











Basically at extremes I agree that your animation is true but within the limits of a real suspension and amount of travel it will see I don't see it being an issue. I don't think I'd be swinging 24" of travel out of that but 10-12" of vertical movement is probably well within reason. I'd bet the toyota pictured above is in the 18" range and living. Now granted, even with a 2 piece shaft I bet his drive line angles are a bit easier to work around being a longer driveshaft.
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Unread 03-01-2013, 04:04 PM   #245
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Quote:
Originally Posted by sirhk100 View Post

I guess???? Not really...
No, really; that's what it looks like, to me.
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Unread 03-01-2013, 04:26 PM   #246
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Quote:
Originally Posted by sirhk100 View Post
I can see what you're showing in that animation but you also look to be heavily exaggerating the amount of vertical travel the center of the axle would see (not counting articulation) Just roughly holding me fingers to the screen you're showing a vertical travel of something equivalent of the length of the link arms which I just don't see being realistic. Like I said, I have nothing to base on other then that picture posted but I'm betting the 10-12" of vertical travel that thing sees, the pinion angle doesn't change enough to harm it. As for the pinion on articulation, I don't see how it would be any different then a standard link setup. They all tend to duck walk, especially when you get into the 20+ inch travel range. (I own a 3 linked truck pulling 23" all home built for reference) The axle is still going to pivot around that upper link point and it really I think would still work the same. With the fuel tank being a physical block for where the links would need to run this in my eyes seems like a very viable alternative.

Like I said, I know for a fact it's been done before very successfully so I'm not sure why it couldn't be applied to the confines of a Jeep. I'm guessing that's a 4door JK and not wanting to deal with gas tank solutions it seems like a great alternative.

http://i5.photobucket.com/albums/y16...g/P1020015.jpg
http://i5.photobucket.com/albums/y16...g/P1020016.jpg
http://i5.photobucket.com/albums/y16...g/P1020040.jpg
http://i5.photobucket.com/albums/y16...g/P1020286.jpg

Basically at extremes I agree that your animation is true but within the limits of a real suspension and amount of travel it will see I don't see it being an issue. I don't think I'd be swinging 24" of travel out of that but 10-12" of vertical movement is probably well within reason. I'd bet the toyota pictured above is in the 18" range and living. Now granted, even with a 2 piece shaft I bet his drive line angles are a bit easier to work around being a longer driveshaft.
Thats a wikipedia animation (they're usually a good source for .gifs), no idea about the lengths of any of that, but the proportions don't look even close to what they should be for control arms.

The limit strap on the very first pic looks like there's very little down travel left. I suspect the geometry used means there is a smaller than usual margin of desirable pinion angle.

I'd have to do some 3D modeling (or 2D) to find the appropriate separations. I doubt there's enough room in any Jeep for arms long enough to get 10" of travel.
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Quote:
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JF taught me that the 2.5L, Ax-5 and D35 together are so powerful that angels weep when I shift into 4LO.
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The only thing a bicycle inner tube is good for, is tying a knot in the end of when you run out of condoms.
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Unread 03-01-2013, 04:44 PM   #247
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So I just pulled up the geometry that I built my system off and my pinion angle dips down a hair on both compression and droop which I guess would be opposite of what that would be doing. I'd still think though that depending what your driveshaft setup is it would still possibly work fine. I had to pull up the file again cause I couldn't remember if mine was pivoting upwards or downwards thru it's cycle.




Mine isn't on a jeep though and I had a lot more room to work with and longer arms to work around. I also was looking to pull much larger travel numbers.
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Unread 03-01-2013, 05:03 PM   #248
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bored here at the end of my work day... I just pulled these numbers outta thin air! no clue if they're close to what could actually be fit under a 4 door JK.

The 3 horizontal lines on the left are 5" increments so you've got 10" of vertical travel. The long blue line at the bottom is just a horizontal reference line to measure pinion angle change from. Maybe I'll screw around and put some real numbers in based on space available sometime but just really quick...

Bump...



Ride



Droop




You can see the degree change in there. The extreme is 6 degrees of pinion change basically and that's with just numbers pulled outta my XXX... I'm sure I could spend some time and get this within reason if I change the spread between mounts and lengths of arms. But like I said, this is fake with no limitations of reality. Just saying though, I think it's possible to dial it in if someone really put some effort into it.
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Unread 03-04-2013, 08:38 PM   #249
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Quick noobish question... is it advisable to use run the smallest sized JJ's on a 4-link. Specifically on a rig that will be beat on pretty good?
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Unread 03-05-2013, 06:11 AM   #250
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Originally Posted by Kodiak17 View Post
Quick noobish question... is it advisable to use run the smallest sized JJ's on a 4-link. Specifically on a rig that will be beat on pretty good?
2.0" joint with 0.75" shank? Only seen them on uppers. 2.5" joint with 1.00" or 1.25" shank is what I see on lowers.
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Quote:
Originally Posted by HurricaneRZA View Post
JF taught me that the 2.5L, Ax-5 and D35 together are so powerful that angels weep when I shift into 4LO.
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Originally Posted by mrblaine View Post
The only thing a bicycle inner tube is good for, is tying a knot in the end of when you run out of condoms.
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Unread 03-05-2013, 06:59 AM   #251
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Quote:
Originally Posted by Kodiak17 View Post
Quick noobish question... is it advisable to use run the smallest sized JJ's on a 4-link. Specifically on a rig that will be beat on pretty good?
I wouldn't and I don't see why you would. Considering you're moving past the stock suspension setup, you're moving past the stock mounts. Therefore, you don't have to be stuck with the stock upper mounting width. In a 4 link the uppers are seeing more stresses than they are in stock form due to the lack of a track bar. I'd use the big joints there and everywhere else for continuity, simplicity and strength.
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Unread 03-05-2013, 10:18 AM   #252
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I wouldn't and I don't see why you would. Considering you're moving past the stock suspension setup, you're moving past the stock mounts. Therefore, you don't have to be stuck with the stock upper mounting width. In a 4 link the uppers are seeing more stresses than they are in stock form due to the lack of a track bar. I'd use the big joints there and everywhere else for continuity, simplicity and strength.
Plan to use Savvy arms in stock locations, then using those JJ's for a 4-link down the road. So maybe not the smallest JJ's, but whatever Savvy supplies in their kit.
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Unread 03-05-2013, 10:33 AM   #253
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Quote:
Originally Posted by Kodiak17 View Post

Plan to use Savvy arms in stock locations, then using those JJ's for a 4-link down the road. So maybe not the smallest JJ's, but whatever Savvy supplies in their kit.
Or, shell out for the big stuff and then sell your Savvy setup to recoup a portion of the cost.
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Unread 03-05-2013, 10:35 AM   #254
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Quote:
Originally Posted by Kodiak17 View Post
Plan to use Savvy arms in stock locations, then using those JJ's for a 4-link down the road. So maybe not the smallest JJ's, but whatever Savvy supplies in their kit.
Savvy supplies standard JJ's from Currie. The small 2" dia x 2" mount width with 3/4" shank in the uppers and the bigger 2.5" dia x 2.625" mount width with 1" shank in the lowers. I use 1.25" shank big JJ's all around.

You're better off selling the Savvy arms when it's time and building new ones and going with 2.625" width mounts. Trying to make those small JJ's hold up in that application will be a waste of time, at least IMO.
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Unread 03-05-2013, 10:48 AM   #255
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Or look at the monster 3" joints. They're on Currie's site. That's a joint worthy of a Rockwell.
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Quote:
Originally Posted by HurricaneRZA View Post
JF taught me that the 2.5L, Ax-5 and D35 together are so powerful that angels weep when I shift into 4LO.
Quote:
Originally Posted by mrblaine View Post
The only thing a bicycle inner tube is good for, is tying a knot in the end of when you run out of condoms.
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