Beam to A-arm Conversion?

[Wendell #527]

I have a 1985 12 car I've been racing in Sportsman class. It has inboard hubs in the rear and I'm thinking of getting mid-boards so I'll have longer axles and can increase travel from 15.5" to about 22". If I do that the front will be what slows me down. It's an older car so I only have about 12" of travel on the 4" longer arms. I could possibly change the chassis to be taller in the front end so I'd have better travel, but at that point I might be better cutting off the front end and giving it A-arms. Does anybody make a "kit" that has basically a 10-car front end and I just have to mate it to the chassis? Maybe it wouldn't be worth it, I'm just askin.

[TUBETECK]

As far as I know, no one make a "conversion kit" to switch a beam front for an A-Arm front end. Your lookin at major reconstruction. Its not bad if you know how to do it but its impossible if you dont. The worst part is building the bulk head and then re-engineering the entire chassis to withstand the twisting stresses that an A-Arm front end deals with. Learn to live with it or buy a new chassis with the front end that you want.

[TauMau]

http://eagleperformance.com/AArmConversionKit.html

www.a-arm.com

Since this is a race car we're talking about, I'd cut off the front end and just start from scratch. Neither of those kits really offer enough travel to make it worth it.

Is there a reason you don't update the car and race class 12?

[16004leyef]

look at this thread from the show and tell this guy had a single seat 12 type car and converted it to a arm and the car turned out bad ***** http://www.race-dezert.com/forum/showthread.php?t=49563

[Wendell #527]

http://eagleperformance.com/AArmConversionKit.html

www.a-arm.com

Since this is a race car we're talking about, I'd cut off the front end and just start from scratch. Neither of those kits really offer enough travel to make it worth it.

Is there a reason you don't update the car and race class 12?

I'm currently running a 2771 type IV motor, so I couldn't race in 12. I could change the motor, but with 15.5" of travel in the rear modern 12 cars blast past me.

Good comments everybody. Thanks for the input.

[SteveinAZ]

Wendell, I built the front end on my car with a retrofit in mind. The upper and lower arm mounts, steer box mount and shock mounts are one unit that is built on the bench so all of the geometry is set. The parts are all cut from 4130 plate and welded up, then grafted onto the car. The a-arms and spindle uprights are all plate items as well...spindles and hubs/brakes are 2" Kartek bolt ons. This set up gives me 22" of wheel travel and <3/8" toe change - I do not recall the track scrub, but it is pretty small.
To mount it on most beam cars this would be to cut the main rails (lowers) at one of the forward most crossmembers, and mount the "box" tieing it into the lower chassis. Then you will need to tie in the upper part to the upper rail of the car and some good triangulation to the base of the windshield/upper frame rail area.

If you are interested, let me know – PM me your email or phone number.

Steve

[philofab]

Can someone explain to me why an a-arm car would have more twisting forces than a beam car over the same terrain?

[TauMau]

Can someone explain to me why an a-arm car would have more twisting forces than a beam car over the same terrain?

If this is in fact the case, the only reason I could see this being true is:

When the trailing arms on a beam car begin to move through their travel, the load is primarily displaced by pulling on the subframe tubes attached to the upper beam tube, and pushing on the subframe tubes attached to the lower beam tube. With a-arms the load is just all forced upwards hence the twisting. Here's a pic:

http://img.photobucket.com/albums/v491/P8ntballing890/beam-aarm.jpg

I believe this issue can be very successfully combated and possibly eliminated by a properly built bulkhead/similar design which will isolate the upwards force to the front end (ie shock towers) rather then having it transferred throughout the rest of the chassis/subframe...if that makes any sense.

[TUBETECK]

If this is in fact the case, the only reason I could see this being true is:

When the trailing arms on a beam car begin to move through their travel, the load is primarily displaced by pulling on the subframe tubes attached to the upper beam tube, and pushing on the subframe tubes attached to the lower beam tube. With a-arms the load is just all forced upwards hence the twisting. Here's a pic:

http://img.photobucket.com/albums/v491/P8ntballing890/beam-aarm.jpg

I believe this issue can be very successfully combated and possibly eliminated by a properly built bulkhead/similar design which will isolate the upwards force to the front end (ie shock towers) rather then having it transferred throughout the rest of the chassis/subframe...if that makes any sense.



Thank you: I'm glad that someone can put a drawing to what I was saying. Unfortunatly I'm not one of those guys that are computer savy, but I do know what I know and that is a beam car and an A-arm car twist differently and are engineered differently. I've seen "re-engineered chassis" that have been changed from beam to A-arm and the first question from the owners is "what did I hit that cracked the frame in five places from font to back".

[Ziggy]

Can a 96 I Beam Ford p/u full frame be converted also?

[Steven_Tolbert]

Can a 96 I Beam Ford p/u full frame be converted also?

Sure why not anything can be done if you put your mind to it.

[Prerunin554]

Can a 96 I Beam Ford p/u full frame be converted also?

You can do anything you want, this is what my buddy did to his:

[Steven_Tolbert]

You can do anything you want, this is what my buddy did to his:
That is sweet!!!!