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Old 02-05-2007, 07:30 PM   #1 (permalink)
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I think I screwed up somewhere...

I posted this over on the newbie side for a day, but no answer. So here it is with the flame invitation.

After more than 2 years farting around with a truggy build, I finally pulled it out of the garage under it's own power yesterday. I noticed on several occasions when jacking it up and down in the garage that the wheelbase changes by about 2 inches as the body goes up and down. This is to be expected due to the 43 inch long arms going down at a 20 degree angle. The arm swings through an arc that pulls the axles closer together as the axles droop and pushes farther apart as the suspension compresses.

When I pulled into the street with 4x4 engaged and turned right, the entire truck lifted and lurched hard left. As in, the body rolled left almost as far as the suspension travel would allow. I initially thought that I forgot to bolt in a control arm or something and the suspension had fallen apart. When I climbed out and looked, everything was correctly connected. When I switched to 4x2 and drove around some more, the truck stayed mostly level. In analyzing this, it seems that the shorter track of the back axle in a turn pushes forward against the slower front axle and causes the above mentioned arm swing arc to raise up and tilt the truck. The Detroit rear would further add to this phonomenon on the inside of the turn since it tends to drive the axle straight forward and would explain the left tilting. Is this just something that people get used to in a crazy travel off-road suspension or should I be lowering the angle (reduce the lift / lower the frame attaching points) and/or adding sway bars? The truggy sits on 12" travel air shocks right now with 4-links front and back. Due to mounting locations and angles of the shocks, wheel travel is about 18 inches front & 21 inches rear. Steering is via full hydraulic.
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Old 02-05-2007, 07:41 PM   #2 (permalink)
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First time i pulled mine out of the driveway after linking it with rockwells i dropped both driverside coils as it jacked over turning into the street. I think i was in 4wd but not sure, added limit chains, including center limits with only about 2 inches of slack and all is good. FWIW mine is 1 link rear welded diff and radius arm front detroit locker.
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Old 02-05-2007, 07:48 PM   #3 (permalink)
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Ahhh the ancient Chinese Air shock mystery! I think we will need pics of said motion. And one more beer!


Back momentarily,
Easy....
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Old 02-06-2007, 08:44 PM   #4 (permalink)
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Video coming

I'll get it back down off the trailer in the next day or two and have somebody video it. I think I found part of the problem by doing some reading though. The instant center point is too close to the axle. If I move the lower control arm mounting point down about 2 inches the upward pitching tendency should be reduced somewhat. Hopefully this link will get a picture to show up: <a href="http://members.cox.net/mrpilotron/buggypics/index.htm"> build pics </a>
<img width=640 height=480 src="http://members.cox.net/mrpilotron/buggypics/100_3389.JPG">

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Old 02-06-2007, 08:58 PM   #5 (permalink)
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I think you found part of the problem ( lowers are tied into the seat mounts! ) And the biggest contributing factor is the 10 inches of shaft showing. Lower it down at least 5 inches and try again. it should make a monumental difference. Then look into sway bars. Also move your front shock mounts farther out on the axle if you can.

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Last edited by Easy Rick; 02-06-2007 at 09:49 PM.
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Old 02-06-2007, 08:59 PM   #6 (permalink)
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First thing, why the body lift? Isn't one of the reasons for a truggy to lose sheet metal so you can avoid large lifts?

2nd, were you driving it with the joints not bolted tightlike in the pics?

3rd, I would think that you would want to tie your axle trusses into your third members. and maybe some more support on your rear frameside shock tower.

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Old 02-06-2007, 09:12 PM   #7 (permalink)
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The bodylift was to clear the back of the engine and transmission. I couldn't leave the body down low and still use the factory gas pedal. As it is, I still had to carve out most of the firewall and move the body back 3 inches.

As far as the bolts and bracing goes, I did tighten the bolts before driving and I want to use the minimum weld possible prior to working out the angles and bugs. I won't go crawling until there is significantly more reinforcement and gussetting welding all around. Unwelding is easier that way.

I also have a whole lot of exo-cage to build yet...

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Old 02-06-2007, 09:17 PM   #8 (permalink)
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The bodylift was to clear the back of the engine and transmission. I couldn't leave the body down low and still use the factory gas pedal. As it is, I still had to carve out most of the firewall and move the body back 3 inches.

As far as the bolts and bracing goes, I did tighten the bolts before driving and I want to use the minimum weld possible prior to working out the angles and bugs. I won't go crawling until there is significantly more reinforcement and gussetting welding all around. Unwelding is easier that way.
1. Cut out the floor section to accomodate trans/t-case without a body lift.

2. Remove body lift

3. Fabricate new gas pedal assy.

4. Lower ride height as per Rick.

Two years to do that?
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Old 02-06-2007, 09:28 PM   #9 (permalink)
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Two years to do that?
Hey, I have 3 real jobs too! This thing gets ignored for weeks or months at a time...
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Old 02-06-2007, 09:31 PM   #10 (permalink)
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Hey, I have 3 real jobs too! This thing gets ignored for weeks or months at a time...
I understand... Just giving you a little shit , and hopefully some motivation
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Old 02-06-2007, 10:08 PM   #11 (permalink)
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the body lift is a non issue
there is so little wieght in a body
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Old 02-06-2007, 10:30 PM   #12 (permalink)
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the body lift is a non issue
there is so little wieght in a body

yeah maybe just the body itself, but when you start adding up all the things that go into it, the wieght starts getting pretty high....
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Old 02-06-2007, 11:10 PM   #13 (permalink)
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your problem must have to do with your (instant center point) as well as well as your link lengths. if you read up on it youll find that with out your links hitting appro at your (icp) your truck will lift or lower when put under throttle depending on how far off you are. antisquat
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Old 02-07-2007, 07:10 AM   #14 (permalink)
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Holy Anti-Squat Batman!

Those link angles are going to be miserable... they're going to make your rig "stand up" under throttle in the rear, and if they're this steep in front, your rig will have significant difficulty climbing any ledges... the suspension will raise and tires will stand still until reaching it's flex limits, and only then will the tires begin to climb...

I know this because when I rolled my rig out for the first time, I too had too much link angle... I had 20* - you have a lot more than 20*. I lowered mine 4 inches, lengthening the wheelbase and reducing my link angle to 15*... works great now, but it was miserable before.
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Old 02-07-2007, 07:25 AM   #15 (permalink)
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if you read up on it youll find that with out your links hitting appro at your (icp) your truck will lift or lower when put under throttle depending on how far off you are. antisquat
The links always converge at the instant center. That's how it's defined.
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Old 02-07-2007, 07:30 AM   #16 (permalink)
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Try lowering the frame mounts for the lowers to the bottom of the frame, and the uppers to as level as possible and try again
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Old 02-07-2007, 07:39 AM   #17 (permalink)
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man, that thing needs some work.

don't get me wrong, i know how shit can escape you. i will be starting a thread shortly on just this, but those rear links are mounted way too high under the frame and way too steep, both sets of them, not just the lowers. the uppers should be nearly horizontal and the lowers should be half the angle they are, if not less than that. also, try to match the front link angles when you redo them, if necessary, redo them all. remove the body lift, cit the sheet metal and redo a floor/tunnel from sheet metal. those look like pretty short air shocks, i'd just mount them a little lower and lower their ride height, add bumpstops if you don't already have them and lean them forward a little as well as their current angle inward and finally, add a sway-bar, at least to the front. i run a stock 80's grand waggy sway-bar on mine, it's easy to fit and it's a good stiffness vs. flex for the street, but too stiff for the trail, it gets disco-ed. i had a similar problem when i got mine out of the garage for the first time, but a lot of little redo's got it working pretty well, it's all about trial and error. it'll still lean some if i don't run the swaybar on the street, but not too bad. and it will still bind due to the rear being welded and trying to crawl up into the front, but not as much either. and putting a winch on the front helped to level things out a bit too.
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Old 02-07-2007, 09:09 PM   #18 (permalink)
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Why do you have your links so high on the frame end anyway? It looks like they are welded to the cab floor! I am going to assume they aren't though. Definately lower the frame ends of the links first and lower your ride height a little.
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Old 02-07-2007, 10:10 PM   #19 (permalink)
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It kinda hard to tell but from the looks of it in the pic, it looks like the upper mounts at the frame are below the lowers..... As stated before drop lower all your mount at the frame, and raise the uppers at the axle......
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Old 02-08-2007, 11:17 AM   #20 (permalink)
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I would raise the lowers at the axle as well as lower them on the frame. It also looks like the uppers are very short compared to the lowers.
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Old 02-08-2007, 12:29 PM   #21 (permalink)
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strokeddodge would run it
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Old 02-08-2007, 08:22 PM   #22 (permalink)
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strokeddodge would run it
Fuggin A' right he would!
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