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Author Topic:   Left Rear 4 Link Video Footage
jammin
Dirt Administrator

Total posts: 6243
posted June 27, 2004 02:58 AM  
Excellent footage, Jam! Interesting how the spring just kinda sits there under acceleration. I thought spring behind gets loaded from both ends from indexing and body roll.

sdracer12
Dirt Maniac

Total posts: 180
posted June 27, 2004 10:01 AM  
Incredible video!! I always thought the LR spring did SOMETHING on accel. but once up on the bars, the lr spring just floats. We have put spring rubbers in LR to help forward bite on dry slick, but now it looks like they really don't do much.

What kind of LR upper and lower bar angles (static), are in this car?

Also, very interesting how the shorty bar actually loses angle on acceleration as the front of the pinion rises, and then drops on decel. Now I can see how the short bar will stick the RR on entry.

THANK YOU!!!!

jammin
Dirt Administrator

Total posts: 6243
posted June 27, 2004 12:36 PM  
Yep thats what it looks like...kinda what i have been thinking since i started working with a bar car. Then one night after losing my lr spring on the first lap and was able to finish the race no problem...except entry was a bit loose but once it got back up it wasnt to bad. Here is somthing else to ponder allot of people stiffen the lr spring to help load the tire....well we see how that works. Now if you stiffen that lr to like a 250 or 275 what happens when you get out of the gas and set the car for the turn...it stays up on the bars because the spring is so stiff. Now if you run a 200 or 175 lr when you get out of the gas the car will drive the lr into the ground making the car rotate off of that tire. ( push a gokart with a locked axle in a straigt line now jump on the lf of the gocart what does it do? ) You have to remember to do somthing like put a 175 lr you need to check all things to make sure that nothing hits...or the driveshaft wont pull out.

JT54
Dirt Maniac

Total posts: 170
posted June 27, 2004 07:48 PM  
Hey jammin how much travel are you getting on your pull bar? looks like allot......I am getting 4 inches on mine on a three link ...do you think that is too much?

jammin
Dirt Administrator

Total posts: 6243
posted June 27, 2004 10:00 PM  
thanks ,maybe you could look at some of my more recent posts and offer some advice....keep the vidios coming they are verry interesting.

NJantz
Dirt Forum Champ
Total posts: 755
posted June 28, 2004 05:38 AM  
thanks for another great video.

driver27
Dirt Maniac

Total posts: 194
posted June 28, 2004 06:35 AM  
Looks like the coilover eliminator might be topping out. I wonder if you put an extension on it, if it would allow the car to get up on the bars even more. Just a thought. I too thought the lr would be loading the spring, but it doesnt. very good job, and very informative.

PEDDLER
Dirt Freak

Total posts: 446
posted June 29, 2004 10:18 AM  
TTT
Keep together

de94wcc
Dirt Forum Racer

Total posts: 87
posted June 29, 2004 06:09 PM  
Is it just me, or is the rear end coming in contact with the underslung? When it's all the way up on the bars, it doesn't look like the rear end oscillates at all. Could it be that since it is up on the bars it basically has an infinite spring rate and is therefore not able to move? This looks like a Dirt Works car and I know they put about a 15 degree bend in that bar. Does anyone think there would be a benefit to redesigning the chassis in this area to completely eliminate the underslung in this location?

dirtbuster
Dirt Forum Champ
Total posts: 2007
posted June 29, 2004 06:16 PM  
You have to have something down there to stop it or the reared would drop out of the car under acceleration. Dirtworks put the bend in theirs to allow more travel. Even a car without the underslung bar needs something to stop the rearend besides the shock otherwise you risk pulling the shock apart. I have seen latemodels with a chain to limit travel then its adjustable for how much you want to allow it to drop and walk forward. Look at the underslung bar on most 4 link cars and i bet you'll find it looks beat up from the rearend rubbing on it under power.

uforacing51
Dirt Forum Champ
Total posts: 570
posted June 29, 2004 09:14 PM  
94wcc,
On my Harris, the frame was notched by the previous owner and made a bunch nicer by Harris when it was there last year. It doesn't hit any more but I think it was when the frame wasn't notched.

MOD75D
Dirt Freak

Total posts: 236
posted June 30, 2004 05:55 AM  
Thanks for the video Jammin. I can't wait to see a LR video of a swing arm Z link. Thanks again for the great learning tools.

NJantz
Dirt Forum Champ
Total posts: 755
posted June 30, 2004 06:03 AM  
Thanks for taking the time to present the video. I saw something that I'm now changing on my car to correct a problem with the left rear spring seating against the top spring plate on the eliminator.

Mudslinger
Dirt Roller

Total posts: 18
posted June 30, 2004 12:04 PM  
Jammin, may I ask if the shock and spring are clamped to the rearend housing or are they connected and floating with the birdcage?

From what I can see, it looks like they are clamped up to the rearend. If that's the case, I can see why the spring is being unloaded. When the housing indexes the tube rotates towards the front of the car which in turn unloads the spring since it's in the back.

If the shock and spring were attatched to the floating birdcage, when the car hikes up on the bars, the indexing of the birdcage should jack pressure back into the spring creating wedge which would be more benificial than loosing all of the wedge with the spring unloaded.

Any thoughts?

BTW, great video, I'm really learning alot!! Keep it up.



dirtbuster
Dirt Forum Champ
Total posts: 2007
posted June 30, 2004 01:55 PM  
Even with the spring on the birdcage it will still seperate on most cars under full suspension travel. When your up on the bars it doesnt really matter much what the spring is doing all the weight is carried on the bars the spring is just in there floating.

zeroracing
Dirt Forum Champ
Total posts: 1875
posted June 30, 2004 02:13 PM  
my car indexes a ton so that the spring is always loaded, some cars pick it up off the spring, i keep mine loaded.

jammin
Dirt Administrator

Total posts: 6243
posted June 30, 2004 07:46 PM  
It also appears that when the car is "unloaded" that the bottom bar is at an uphill angle. I think that is what contributes to the improper indexing (spring coming out of the pocket). Both bars uphill is only going to pull the rear end ahead. Have you tried to get some footage with a more conventional setup? Do you think it would even make a difference? I have some pictures of a 3-link car we used to run with the LR clamped in front, and I noticed the same thing, about a 2" gap from the spring to the top of the pocket, when the car was hiked up. You never really mention how you liked your car on this particular night. Did you think it was fast up on the bars like that?

jammin
Dirt Administrator

Total posts: 6243
posted July 01, 2004 12:05 PM  
Car came from 18th to third in less than 20 laps.

dirtbuster
Dirt Forum Champ
Total posts: 2007
posted July 01, 2004 03:13 PM  
More angle in the lower bar will help the car get up on the bar and bite quicker. It will not index the BC as much though. You are relying on the bars to carry the car and build bite not the spring. Checked out a buddies late model and they have about 10 degrees in the bottom and 20 in the top at ride height.

MIDWEST MOTORSPORTS
Dirt Full Roller

Total posts: 50
posted July 01, 2004 03:40 PM  
footage was awesome by the way. what was the right side setup? and how was the right rear sprung. and is this a dirtworks?

secondly- underslung cars that have enough travel room from the bottom of the housing are just as effective and have a stronger tail. a limiter strap will actually want to bust the left rear loose when it tightens the chain. i have heard a limiter strap is for the birds, but each driver is different. if the underslung car has enough clearence, it will allow the birdcage to index to the complete extension of the shock thus meaning that a proper dip in the underslung is virtually the same as an overslung car. ive never heard of the left rear ripping the guts out of a shock under full extension.

but this video was very very cool.

[This message has been edited by MIDWEST MOTORSPORTS (edited July 01, 2004).]

#13 mod
Dirt Full Roller

Total posts: 72
posted July 02, 2004 08:35 AM  
The small holes on the hats on a slider are for retaining the spring to the hat with a zip tie. That way the slider can use the shaft as a guide and you don't have to worry about the spring coming back into the hat correctly. If your slider dosen't have holes in the hats, make some. It works very well.

dirtbuster
Dirt Forum Champ
Total posts: 2007
posted July 02, 2004 09:25 AM  
Thats exactly what we did on our old car. Made it so the hat slid on the shaft with the spring then when it seperated the hat would move but not come loose from the spring. We had a LR spring get wedged under the hat once before. It was just like putting 2" or so more preload on the spring. You can about imagine what it handled like.

star1modified
Dirt Maniac

Total posts: 102
posted July 08, 2004 01:56 PM  
Yeah I had that problem dirtbuster...this weekend against that car inthe clip.

star1modified
Dirt Maniac

Total posts: 102
posted July 08, 2004 02:00 PM  
quote:
Originally posted by dirtbuster:
You have to have something down there to stop it or the reared would drop out of the car under acceleration. Dirtworks put the bend in theirs to allow more travel. Even a car without the underslung bar needs something to stop the rearend besides the shock otherwise you risk pulling the shock apart. I have seen latemodels with a chain to limit travel then its adjustable for how much you want to allow it to drop and walk forward. Look at the underslung bar on most 4 link cars and i bet you'll find it looks beat up from the rearend rubbing on it under power.

yeah gotta be careful with no underslung I pulled my elimnator apart.

Ells949
Dirt Full Roller

Total posts: 28
posted August 01, 2004 12:59 AM  
quote:
Originally posted by jammin:
I know this one everyone will enjoy This one is a 4 link left rear...3 wheel type setup...shorty bar to left side of pinion, short lower arm. The rest is pretty viewable
Jammin,Is there a video of the left rear on a clamp missing? http://www.thedirtforum.com/album/Chassis%20Movies/6_27_04.WMV

Enjoy!
jam



Kromulous
Dirt Forum Champ
Total posts: 796
posted August 02, 2004 02:59 PM  
Anyone else notice how much that shorty panard bar was flexing? It had to be flexing on the chassis end a good 2 inches or better. I bet that piece will become fatigued in not time at that rate, long as its fast thou !

Is it me or does the LR lower bar look awefull close to the panard bar mount? Looks like it actually hits it when its up on hte bars. Could be the viewing angle thou, *shrugs*

[This message has been edited by Kromulous (edited August 02, 2004).]

paulickr
Dirt Maniac

Total posts: 110
posted August 04, 2004 01:26 PM  
hey jammin, what bar angles are you running and what pullbar spring, we only get about 2" of pull on a 600-1200 progressive spring, i cant get to 3 wheel with my 4-z at all, ron

jammin
Dirt Administrator

Total posts: 6243
posted August 04, 2004 08:13 PM  
wow hey thats quite a show, what holes are you running your links in??
i want to get more left lift on mine, i have a dw8 4-z

you seem to have a ton of bite, what pullbar spring? i have been using a 600-1200 progressive and it seems touchy and not enough reaction only 2"

my e mail is ron.paulick@hydrite.com

thanks ron

o5racer
Dirt Freak

Total posts: 402
posted August 08, 2004 09:43 PM  
Hey Jammin, any chance of getting that clip in a MPEG format?

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