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Jacob ladder


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6 replies to this topic

#1
PoleCar

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Does the length of the jacob ladder ( 13 1/8, 13 3/8, 13 5/8, 14 inch ) really make any different to the handling of the racecar?

Thanks

#2
larryo

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laugh.gif I would say yes.

1) What size jacobs ladder came with your race car initially?


2) I would say the chassis mfg had a reason to install a certain length jacobs ladder
in your particular race car.

a) They say and I have read there is a certain length for the straps compared to the length
of ladder and the angle between the too is important if not imperative.

cool.gif I have seen two different books say their "length" and their "length" of the straps is the
geometrically correct one, but they are different in length and the staps are a different
length????? Who is right? I can't answer about the angles but I think the 14 inch ladder
had a 30 degree angle to the straps and the straps were 7 inches long.


3) If I had to guess a longer ladder promotes less change in the rear end from High CG to low
CG through roll in the corner. A jacobs ladders loosens the car through roll in the
corner. A panhard rod tighten it up! Big difference.


4) So I would rekon a shorter ladder would loosen the car up quicker in the corner and
promote more bind in the rear end suspension. Do you want to loosen up your car or
tighten it up? Do you have a binding problem now?


5) Lastly we had a adjustable jacobs ladder in our FF midgets. It made a big difference if you
lowered or raised it. It was one of the most important chassis aid we had.


Check out this ling for modified Watts lingage? Interesting brake also.

http://www.tsmmfg.co...tts_Linkage.htm

Also another link talking about CG and the Jacob/watts linkage.

http://www.scrafan.c...1.html#assembly

Larry "O" wink.gif

#3
larryo

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laugh.gif I was hoping somebody would comment about the jacobs ladder.

I have been thinking about it a lot lately. Every time I buy a new issue of
circle track those guys keep pounding the same subjects over and over again.

I have posted some rear view videos of our FF midgets, which shows the jacobs ladder in
action for heat races and main events.

This is what I have learned. The jacobs ladder "indirectly locates the "bird cage".

And what is located on the bird cage? The shock and the torsion bar/spring.

What have you learned about the placement of the shock and torsion bar/coil spring on any axel?

So without even trying,..... by putting on a different lengh jacobs ladder, you have changed
the rate of the shock and spring/torsion bar on the RR of the car by the distance it is placed out
away from the frame.

Then you can start talking about CG, moments, rear steer and radius rods.

Larry "O" rolleyes.gif

#4
RonnieW33

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So I went ahead and modeled a couple scenarios with some of my sweet engineering software and here is what I came up with:

The vertical position of the birdcage in motion will not differ with shorter or longer jacob's ladders.

The rotation of the overall jacob's ladder increases with added length. This is because the center of rotation is moved inward towards the centerline of the chassis.

So, no I do not believe that the length of the jacob's ladder directly affects the handling of a racecar as long as the placement of the rear axle is not changed.

What did you find when raising or lowering the jacob's ladder Larry? My computer keeps crashing when I try and model that. I have a feeling it works similar to a pan-hardt bar.

Just my two cents,

Ronnie



#5
Tony Main

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I have never tired anything with a different length ladder, but I have ran different length straps. I belive it would have the same effect as moving the ladder on the birdcage, to help give you more forward or side bit.
www.purdue.edu/pmaPurdue Motorsports Association

#6
Midgetcc

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In regards to raising and lowering you ladder there is a huge difference. Lowering that ladder (ie. small lower straps or lowering clevis on birdcage) will change the rool center nad hooking car up drastically.

This is not bad if your track is smooth. But I will speak from expeience when I say lowering that ladder on a somewhat rough track will cause you to have a bad bucking bronco to deal with.

Raising the ladder (ie. small upper straps or raising clevis on birdcage) will do the complete opposite. This will unhook car by raising center of gravity. This is good when you have a rough track or extremely tacky track.

Hope this helps

#7
mcjc21

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Changing the length of the jacobs ladder will change the roll center in the rear of the car.
You can move it towards the left or right depending on the length of the jacobs ladder used, or you can raise or lower the roll center by either raising or lowering it on the birdcage, or by using different length bars top and bottom to make more subtle changes.
I've tried it and it works well.
BUT, I still prefer a panhard bar.




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