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Author Topic:   swingarm help
WPP
Member
posted June 09, 2002 10:05 AM
I HAVE JUST GOT MY NEW SWINGARM RAYBURN STYLE AND WAS NEEDING INFORMATION ON HOW MUCH ANGLE TO PUT IN THE SWINGARMS I ALSO HAVE 30INCH REAR CONTROL ARMS AND THEY ANGLE DOWN 5 DEGREES I PUT THE CAR ON JACKSTANDS AND TRIED TO CHECK THE STEER IN THE CAR AND COME UP WITH WITH THE LEFT REAR MOVING FOWARD ABOUT 3/4 AND THE RIGHT REAR MOVING BACK 3/4 THAT IS THE SWINGARMS MOUNTED IN THE TOP HOLE THE SWINGARM ARE 14 3/8 LONG I JUST THOUGHT I HAVE DONE SOMETHING WRONG WHEN I CHECKED THIS ALSO DOES THE ANGLE ON A SWING ARM AFFECTED FORWARD BITE I HAVE ALWAYS HEARD THE PULL BAR GIVE MOST OF THE BITE ON THESE SUSPENION


Tom Asmus
Member
posted June 09, 2002 12:55 PM
I got a new car too with that same style swing arm setup. I do know that the angle of the the swing arms influences traction. But I am gonna be in the same boat as you are with the learning part. Which brand of chassis did you get! Mine is a Custom Performance!


awkwardjeff
Member
posted June 09, 2002 03:22 PM
sounds like a McDonald car.....as for the angles affecting forward bite......because the left rear lifts during cornering the angle is what is pushing down on the left rear tire (not the spring).......

These cars tend to need lots of static left side bite........like about 300 pounds over the right rear............

I will say that the rear roll center becomes very critical in this type car......if you are off the side bite/forward bite will be off.........you will go from push to loose at the appex without the proper roll center location.

I will say that a McDonald car the front mount of the swing arms are level with the axle centerline.......and these are the exact numbers as for arm length.....

[This message has been edited by awkwardjeff (edited June 09, 2002).]

WPP
Member
posted June 09, 2002 07:03 PM
Mine is a dirtworks about that rollcenter i almost for sure if it is too low withalot of angle it can make this suspenion it can make it loose because of to much body roll and putting more rear steer in the car were is a good starting point


Tom Asmus
Member
posted June 09, 2002 10:26 PM
So jeff what your saying is that the panhard bar is going to be the part that will be adjusted the most to get this type rear suspension to work.


andykmod
Member
posted June 11, 2002 04:22 PM
What would a typical spring set-up be for this type of rear suspension (RATES),also would it be better to mount the shocks on the swing-arms also and what would be a good starting point for them? Why does this type of set-up need to have over 300lbs of bite,is it because the lr spring is being extended during roll? What if you run a short-panhard bar mounted to the lr chassis left side pinion plate,this seems to load the left rear more,would you need less lr bite? thanks


awkwardjeff
Member
posted June 11, 2002 09:24 PM
Tom, I'm not sure what Richard used in your car for a pan-bar......where it mounts both sides and length......I can say a McDonald car only has one mount for the swing arm and only one mount for the rear arm.....until this year, But in the past this was the arrangment......it kept a guy from getting too far off. I would think Richard is the one to talk too about his chassis.

Andykmod, the standard spring package is 350 left rear, 275 right rear.....a little softer if you run IMCA tires.....

I thought I explained why this style needed soooo much bite ......body roll unloads the left rear........as for the pan bar....YES a short bar mounted left of the outside rail, attached to the center of the rear end is what they run............the rear roll center is located 11 inches left of the center of the chassis..........this does push down on both back tires.......it plants the whole rear end to the ground.....that is why these cars need lots of rear steer and/or stagger......to get them through the center of the turn.


Your last question???? would you need less left rear bite??? alot of people are dropping the left rear bite and going fast right now. they have picked up time going into the corner and in the middle on a dry slick super slippery track........they have added side bite to get the car to hold a straight line to help them off the corner....




CUSTOMPERFORMANCE
Member
posted June 11, 2002 11:36 PM
I used that same lengths for the barsand i set the frame mounts with 3 holes each for adj and the panhard bar mounts just to the right of the hump on the rear end on the flat part. I felt the reason those cars j made in the past wihtout adj had to use 300lb of bite because of the lack of adj to make the car tighter or looser.


WPP
Member
posted June 11, 2002 11:58 PM
Thanks for the info guys as i checked my pan hard bar and it was 2inches under the center line should it be closer to the center line of the axles mine is also mounted the left side and to the leftside of the pinion with alot of rake on the chassis it is about 7inches on the mount and the pan hard bar is 15 1/2 inches long again thanks for info


awkwardjeff
Member
posted June 12, 2002 02:51 PM
Rich, where do you mount the frame side of the pan-bar?? how long is the bar ?? what i'm trying to figure out is where your rear roll center is located in relationship to a Jay car.........the reason I ask is someone is asking me in my email about your cars....they CLAIM to have one....but when I direct them to you they keep asking me questions.....which I don't care to get in the middle of.......you and your customers.

I try to help everyone, no matter who built his car.......But I don't care to be in the middle.....I think I may BLOCK that person on my email box......

quote:
Originally posted by CUSTOMPERFORMANCE:
I used that same lengths for the barsand i set the frame mounts with 3 holes each for adj and the panhard bar mounts just to the right of the hump on the rear end on the flat part. I felt the reason those cars j made in the past wihtout adj had to use 300lb of bite because of the lack of adj to make the car tighter or looser.



andykmod
Member
posted June 12, 2002 04:18 PM
I am running 250 lr 200 rr springs on the swing-arms right now but lack forward bite is this because the springs might be to soft.The car seems to transfore weight.I only run 120 lbs of bite and have noticed that when we jack the car up under the left front frame that the spring comes loose in the slider.I would think that with this happening that it would(unload)that corner weight.I know by adding bite this will correct this problem but now when we scale the car if we go over 120lbs of bite the lf becomes lighter then the rf (with out me in the car) i heard not to run with the lf lighter it tends to carry the lf wheel is that true? I know we could add lead to get it but hate to do it(little motor).Also we are running a short pan-hard bar about 11 inches with very little angle,we ran it with some good angle a few times(it stuck lite glue) and liked it but had alot of latteral movement in the rear-end the whole lr wheel was sticking out the wheel well.
ANY ideas to get some forward more bite? thanks........ Andy


CUSTOMPERFORMANCE
Member
posted June 12, 2002 06:01 PM
Jeff the person in question has one of my cars and we used the same lengths for the trailing arms but not having the panhard bar measurement he measured one at a show before he welded the rearend mount on. Panhard frame mount is to a 2x2 square on leftside with a sliding clamp on mount outside the frame.


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