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Author Topic:   Rear Suspension Model...
msnead
Dirt Forum Racer

Total posts: 77
posted June 22, 2005 01:30 PM  
You guys amaze me with all of your knowledge and theory of the various suspension setups. I read on one of the posts that to really understand the 4-bar rear suspension, you should build a model to see what changes do what.

Does anyone know how to build a model that would actually be worth the time to build it? If so, what materials did you use? What scale did you use (if any)? Do you have pictures?

Also, is there software that can show the same results?

We finally bought a modified and if all goes well, we will be hitting the track on July 2nd. Now, I need to learn how to set the darn thing up!!!

Thanks for the information!

m

Kromulous
Dirt Forum Champ
Total posts: 796
posted June 22, 2005 02:09 PM  
It will help, build it about 1/4 scale so its easy enough to sit on a desktop or bench and play.\

Heck i usually just take the springs & shocks off the car and use a floor jack and jack stand and run it thru its travel. Sit there and study it.

Read this site throughly as well, lots of good info hear.

rpm20
Dirt Freak

Total posts: 338
posted June 22, 2005 02:14 PM  
HERES WHAT I DID TO BUILD A MODEL,
I HAVE A 48"X 48" PEICE OF CARDBOARD, THATS MY DRAWING BOARD ,IF YOU WILL.

THEN I TRACED OUT MY BIRDCAGE , HOLES AND ALL ( SMALL HOLES LIKE THE SIZE OF A NAIL OR SCREW)ONTO A SMALL PEICE OF CARDBOARD AND CUT IT OUT.

THEN I MADE 2 PEICES OF CARDBOARD ABOUT 2" WIDE BY 24" LONG TO SIMULATE MY LINKS

NOW I PUT ALL OF THIS ONTO MY BIG DRAWING BOARD BUT NOT BEFORE I MARKED CENTERLINES UP AND DOWN AND SIDE TO SIDE.

I PINNED THE CENTER OF MY BIRDCAGE (CARDBOARD) TO THE CENTERLINE ON MY DRAWING BOARD (BIG PIECE)

THEN I PINNED ONE END OF EACH OF MY LONG PEICES TO THE TOP AND BOTTOM OF MY CARDBORD BIRDCAGE.

I THEN DECIDED WHAT LENGTH BARS I WANTED AND MARKED THAT LENGTH ON MY LINKS AND PUT HOLES IN THOSE SPOTS SO I CAN PIN THEM WHERE EVER I WANTED ON THE BOARD.

THIS MODEL ALLOWS YOU TO SEE THE LINK ANGLES , BIRDCAGE INDEXING AND REAREND TRAVEL OF ANY CONFIGURATION , 4 LINK Z-LINK, 3 LINK ETC BY PINNING A PEICE OF PAPER BEHIND THE BIRDCAGE PART AND INSERTING A PEN THROUGH YOUR AXLE CENTERLINE AND TRACING THE ARC AS YOU MOVE EITHER UP OR DOWN.

TRY IT AND YOU WILL BEGIN TO GET A GOOD VISUAL, THE ONLY THING THIS DOENT TAKE INTO ACCOUNT IS WHEN THE LEFT SIDE REAR STEERS TO THE FRONT AND THE RIGHT SIDE REAR STEERS TO THE REAR AND EXAGERATES THE REAR STEER EFFECT. IT REALLY HELPS TO UNDERSTEND THINGS THOUGH.

[This message has been edited by rpm20 (edited June 22, 2005).]

Chad
Dirt Freak

Total posts: 269
posted June 22, 2005 02:15 PM  
If you want to purchase a very good simulator, here is a website: www.suspensionsimulator.com

If you want to build your own, place a piece of cardboard behing the upper and lower frame mounts (tracing them together on one large piece of cardboard). Transfer the mounting points to plywood. Then measure the distance between your bird cage mounts, they should be centered over and under the rearend tube. Use this measurement to make a replica of the birdcage with a small hole representing the center of the axle. Then drill out the the mounting holes of the frame and birdcage, make trailing arms out of flat stock or wood to match the size of your bars.

To use, start with the lower link at level, place a pencil/pen in the center of the birdcage replica with paper underneath and move the jig through compression and extension travel (you need to measure at least 3" of extension travel- moving the birdcage jig downward to represent the LR and 3" of compression travel-moveing the birdcage jig upward for the RR). Change the position of your frame mounts, one at a time, and redo tracing the axle movement. It will become clear real soon how indexing and axle movement is effected by the angle of the bars.

Alltel
Dirt Maniac

Total posts: 180
posted June 22, 2005 04:26 PM  
Two Words: Tinker Toys

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