jacobs ladder/watts link

Discuss Technical things here, gearing, tires, motors, chassis, ect.


jacobs ladder/watts link

Postby beer16 » Wed Jan 05, 2011 1:32 pm

Is there an advantage or dissadvantage to longer or shorter watts link from strap lenght to the actual center peice lenght?
thanks
2009 IOWA MICRO OUTLAW POINTS CHAMPION
F5 Twister
FendersCycle.com
beer16
Feature Winner
Feature Winner
 
Posts: 156
Joined: Wed Jan 30, 2008 10:45 pm
Location: Norwalk, Iowa
Reputation point: 0

Re: jacobs ladder/watts link

Postby DD 76 » Thu Jan 06, 2011 2:52 pm

IF the 3 pick up points don't move, then a longer center and longer straps would make a bigger arc when the axle moves up and down. I would think that would be an advantage since the point of the ladder is to control side to side movement. You want the biggest radius possible. I would think if you got too long though you're gonna end up binding the center and straps.

http://www.spitzracing.com/index_files/Page724.htm

and another
http://www.indianaopenwheel.com/showthread.php?t=14475
DD 76
Feature Winner
Feature Winner
 
Posts: 190
Joined: Mon Jan 14, 2008 12:40 pm
Location: Des Moines, IA
Reputation point: 0

Re: jacobs ladder/watts link

Postby wild bill » Mon Jan 10, 2011 11:41 pm

beer16 wrote:Is there an advantage or dissadvantage to longer or shorter watts link from strap lenght to the actual center peice lenght?
thanks


I think your strap length is 50% of you ladder lenght squared horizontaly across from the mounting point at the birdcage to a vertical line eye to eye on the strap pickup points. I believe changing the geometry would cause the ladder to push or pull the axle left or right in the chassis as the suspension works up and down, this could create major bind or chain alinment issues. you could raise or lower the pickup point on the birdcage or the strap mounting point to the frame to change your rear roll center. :chug:
wild bill
Rookie
Rookie
 
Posts: 34
Joined: Wed Dec 30, 2009 3:11 pm
Reputation point: 0

Re: jacobs ladder/watts link

Postby Gaerte » Tue Jan 11, 2011 2:16 am

A watts link is a very miss used term in micros and many other forms of racing. The watts link is like 2 panhards hooked to a joint in the center giving you perfect up and down movement. I am not aware of anyone using WATTS LINK on a micro. see photo

751_WattsLink.jpg
751_WattsLink.jpg (17.92 KiB) Viewed 2155 times


Watts link is used in our micros to keep the rear axle in place front to rear like in a Stallard or PMP were some cars use a 4 link or buggle bar.

As for the ladder the longer straps make for less side to side axle movement but change your roll center! The roll center is what will change chassis handling the most!
In a panhard system the roll center is half way between the 2 joints and can be moved up and down by moving the bar up or down but not side to side.
With the ladder system the roll center is were the 2 straps would cross and it moves side to side and up and down as the ladder moves. see photo

rollcenter.jpg
rollcenter.jpg (46.48 KiB) Viewed 2155 times
Go Faster = Go Gaerte
User avatar
Gaerte
Points Runner Up
Points Runner Up
 
Posts: 286
Joined: Mon Apr 14, 2008 3:15 pm
Location: Avilla, IN
Reputation point: 23

Re: jacobs ladder/watts link

Postby woody » Tue Jan 11, 2011 3:18 am

Gaerte's right.
It should be called a Modified Watts Link. Because the connecting arms are a different length. Now, I'm referring to the Rear radius rods vs. the rear torsion arms. These are the items that keep the axle from moving forward & aft. Stock car guys call it a "Z" link(cause when you're laying down looking straight at it.....it looks like a Z).
Now the item that keeps the rear axle from shifting side to side is actually called a Roberts Mechanism. Not sure how it came to be known as a jacobs ladder...but such is life(I would like to know....I just don't). This device differs greatly from a "Pan hard bar" (NASCAR guys call it a track bar). In pan hard movement, the axle moves in a arc to the frame. At the point where the pan hard is level in the chassis, the axle is in a specific location. As the chassis takes off moving(rolling over), and the panhard goes either up or down...you guessed it the axle actually moves side to side. Now before I get pounced on...this is EVER so slight! Remeber micros only have about an inch to an inch & a half of shock travel...so I'm not talking about a ton. But it does move. Changing the vehicles roll center is very easy and very dramatic in a pan hard system. Up = Less roll, Down = more roll.
Now for the Roberts Mechanism or jacob's ladder. If designed as I beleive Mr. Roberts intended, it would cause the axle to travel perfectly straight up and down regardless of the number of inches traveled, thus keeping your axle right where you set it in the shop, while you go hauling off into turn 1 at 80mph. However, that perfect line requires the "Straps" of the ladder and the "Paddle" or center section of the ladder, to be the same length! I'm unaware of any car that has them the same length. Therefore, one can only deduce that there is something to be gained from a longer paddle to strap ratio! Where that gain is, and what that ratio is, depends on many other contributing factors(i.e. where other stuff is mounted in the chassis). Changing the roll center on a chassis using a jacobs ladder require you to move the point that connects to the axle either up or down. Or more commonly referred to "Spiking The Ladder" this is where the racer hooked the paddle lower on the RR bird cage and thus changed the vehicles roll center!
I hope I've helped and not muddied up the water even worse!!

Sonny
woody
Feature Winner
Feature Winner
 
Posts: 144
Joined: Mon Jun 16, 2008 11:24 pm
Reputation point: 16

Re: jacobs ladder/watts link

Postby Gaerte » Tue Jan 11, 2011 10:11 am

Dang it Sonny pullin out those big words! lol Its a modified Roberts lol only a straight line Roberts if the math is as follows.

This mechanism designed by Richard Robert has the proportions (a) = 1, (b) = 1.2, (c) = 2 and (d) = 1.09 any other math will create an arc.

roberts.jpg
roberts.jpg (8.9 KiB) Viewed 2103 times


In a sprint car we always use "(d and c)= twice as long as (b)" "(a) is = to (b)" this is done mostly because it puts the roll center near the center of the chassis.
Moving the paddle up and down on the birdcage is new the older form of adjusting the ladder was to change (c) allot of chassis still have multiple holes at (c) some ladders have diff holes in straps to change strap length. Any changes to the math will move the roll center and change the arc radius.

As for the word Jacobs ladder it came from Genesis in the bible talking about a ladder to heaven. It was later used in naming an ancient toy see photo I think this is were the simular look gave our sprint car part its nic name

jacob.jpg
jacob.jpg (157.75 KiB) Viewed 2089 times


:geek: :biggrin:
Go Faster = Go Gaerte
User avatar
Gaerte
Points Runner Up
Points Runner Up
 
Posts: 286
Joined: Mon Apr 14, 2008 3:15 pm
Location: Avilla, IN
Reputation point: 23


Return to Technical Q&A

Who is online

Users browsing this forum: Jkh9228 and 3 guests