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Post by vrtfarms on Nov 2, 2013 22:15:31 GMT -6
changing leaf spring mod to 3-link. using swedge tubes on bottom, bisket bar top of rear end, coil sliders, clamps to run left spring in front, right in rear of axle and j bar. can I run a 15 inch spring on left and 13 inch on right ? reason i'm asking is I have a 200-15 and 175-13. also my frame has 2 verticle lines of 3 holes to mount front of swedge tubes about 1 inch apart. When setting rear end up straight ( not worrying about trail or lead ) is there any advantage to having either tube 1 inch longer ? Reason I'm asking is I'm a old fart getting back into racing with the vintage guys and all I ever raced were sprint cars and leafspring stockcars. Don't no a hill of beans about these 3 links,4bars ect. Have been told this is the best forum to get good answers and believe me I will have more ?? Thanks in advance, vintagemod750 |
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Post by confused on Nov 3, 2013 9:53:26 GMT -6
Spring length doesn't matter as long as they don't bind or hit anything. A 200lb spring has the same rate, doesn't matter if it's a 20inch spring or 10inch spring. Springs are rated on ponuds of compression per inch of travel.
A shorter tube will act on a tighter radius. I don't think a 1 inch differnce will be very noticable. When we ran a 3-link car, the LR bar was 2 inches shorter than the RR bar. It helped with on throttle roll steer. The track was a very tight 1/4 mile. Also, raising or lowering either bar will affect the way the rear end moves in the car. Right side usually affects entry and center. Left side affects center and exit(on throttle).
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Post by vrtfarms on Nov 3, 2013 14:44:57 GMT -6
Thanks confused for good reply. I'm going thru archives to get a basic starting setup and will post it later for feedback. Will also provide more info about car. I have 2 more ? now. When people talk about angles on bars and top link is that angling down from frame to rearend/? Do I want to angle lower bars a bit to left on frame end ?
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Post by confused on Nov 3, 2013 14:54:47 GMT -6
The top bar is angled down from the housing to the frame mount. The lower bars can be angled up or down from the rear end. That just depends on the track and what the car needs. Angling the RR down will tighten entry and center. This is because the RR wheel is being pulled forward slightly from body roll. Angling the LR up will increase forward bite some but will also increase loose rollsteer.
I would prefer the front mounts of the lower bars be toed in a little towards the frame. As the car rolls over to the right, with a left side mounted j-bar/panhard bar, the rearend moves to the left. With both lower bars pointing left, the rearend will move slightly back and then forward as it passes through this arc.
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Post by vrtfarms on Nov 3, 2013 20:53:25 GMT -6
Thanks again. Getting archive setup overload. So another ? Assuming I set my clamp brackets on rearend centered the same place as old leafspring mounts ( taking into consideration pinion angle ) where should top slider mounts be in relation to bottom mounts ? In,Out, forward,Back , How many degrees ? On left side? On right side ? Should shocks be the same ? Sorry for so many  ?
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Post by confused on Nov 4, 2013 17:34:28 GMT -6
The tops should be inboard from the bottoms. The RR about 12-15 degrees. The LR about 10 degrees. I would mount them going away from the axle, front to rear. Meaning the RR should be leaning back, if mounted behind the axle, about 5 degrees. The LR leaning forward about the same. Make sure niether hits the rearend at any place. That will cause a bind and mess up the handling.
I would mount the shocks at the same angles as the sliders, right to left. Front to rear, mount the close to verticle. This is all at correct ride hieghts.
You haven't asked anything about the pull bar yet. Install the mounts, on the rear end, in the center of the rear end. Space them 4-5 inches apart. This will be a tuning point later. Also have it where the pull bar is mounted 2-4 inches ahead of the centerline of the axle and 11 inches above the center of the axle. The higher the mount, the softer the biscuits need to be.
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Post by vrtfarms on Nov 4, 2013 22:10:19 GMT -6
thanks for very understandable answers ( even the ?s I forget to ask ). If you have time for 2 more here goes. Not quite sure how to word these. How do you figure out right length for sliders and shocks ( distance between top and bottom mounts ) and what is proper way to figure out where to mount J-bar frame mount ? I hope I worded them right
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Post by confused on Nov 5, 2013 19:37:59 GMT -6
I would have them mounted at half of the measured travel distance. Maybe a little less on the left side. Use a 9" shock and standard length sliders. Measure the extened height and subtract the compressed height from that number. Devide it by 2 and you have the installed height for each. If more compressed height is needed, spread the mounts farther apart. If more reboud is needed(LR), bring the mounts closer togethor.
The j-bar frame mount will depend on how long of a j-bar you use. The pinion side is usually mounted on the passenger side of the pinion. The frame mount will be to the left side of the chassis. One important point, Have the frame end mounted about 1-1/2" forward of the pinion mount. As the LR raise and the rear end moves to the left, the pinion also moves forward.
Try to look at some other cars to get a better idea of what to build.
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Post by vrtfarms on Nov 6, 2013 21:54:43 GMT -6
Thank for all the good advice. I'll build top slider mounts ect. with some up / down adjustability. Time to get the welder fired up!
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Post by Krooser on Nov 17, 2013 15:01:50 GMT -6
got any good pix of that fast boys set-up?
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Post by vrtfarms on Nov 28, 2013 15:48:04 GMT -6
Krooser, this is just a basic 3 link. I used to have a stock car with fast boys setup. I't pulled the left front tire so far off the ground you couldn't see a car next to you. L.O.L. My dad gave me this how to drive it advice. Yuz the same advice I gave you on how to drive our old grain truck with 8/71 Detroit diesel, Act like you slammed your hand in the door when you got in and drive the Sh*t out of it!! Looking back now that probably DIDN'T HELP ! A real YeeHaa ride but you can't win a dirt track race with a bucking bronco ! Don't no how to post any pics. sorry
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Post by Krooser on Dec 6, 2013 9:58:32 GMT -6
I have some good pics of the FB deal… that has me intrigued. I have a dirt super stock in stock that I want to try that on but the $$$ is too tight for next year so it's on the back burner.
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