tubing size for a-arms?

[Matt@Lateral Dynamics]

Most guys I've talked to don't use 4130N for weldments because they're scared of welding it. Seriously. It's prone to hot cracking and brittle welds, so they just don't bother. Given the prices of steels now days, 4130N isn't that much more expensive than DOM is.

And.... 1 x .219" wall???? Damn.

[TravisB]

Originally Posted by Matt@RFR

And.... 1 x .219" wall???? Damn.

Ya I know I looked in the book and on the website to make sure but thats what it says......

[62fairlane]

thats why I as looking at LARGE diameter tubing 1.375" since it will handle the bending forces better but have room to go high as 1.5" (I just feel this will be getting TOO big) well using the 1"x.219" tubing as a guide I can run FEA on those then base my tubing size on the strength comparison.

[Musclerodz]

The only advantage to using chromoly over DOM is weight savings due to strength to weight ratio. If weight is not the issue stick with DOM. I use chromoly all the time repairing vintage aircraft but I gas weld it only.

Mike

[62fairlane]

well I only have access to both a TIG and Gas torch. I heard you just shouldn't MIG weld the 4130?

[TravisB]

Originally Posted by 62fairlane

I heard you just shouldn't MIG weld the 4130?

correct the mig welding process makes the 4130 brittle and is more proned to cracking.......

[62fairlane]

so would the 4130 be fine on a street car if welded with a TIG or Flame torch? bacily I am looking to drop some weight if I can (less unsprung mass to worry about)

btw I rehased the geomtry today (had too much kingpin at 14* and reworked it down to 9* which is making everything work much nicer!!) I have much nicer camber curve now and just tweaking in a little more ackerman (before was nearly none)

[TravisB]

Originally Posted by 62fairlane

so would the 4130 be fine on a street car if welded with a TIG or Flame torch? bacily I am looking to drop some weight if I can (less unsprung mass to worry about)

btw I rehased the geomtry today (had too much kingpin at 14* and reworked it down to 9* which is making everything work much nicer!!) I have much nicer camber curve now and just tweaking in a little more ackerman (before was nearly none)

If properly tig welded yes it should be fine....

[Musclerodz]

Tig will also crack as well, just not as prone. Don't ask me how I know. "If it was me", I would PRE-HEAT entire cluster with a rose bud, TIG weld, and POST-HEAT entire cluster to normalize the weld. Pre and post heating will emliminate the stress risers next to the welds that cause the cracking.

Mike

[Kendall Burleson]

Hey guy
You don't want to use 4130 on the street thin wall or heavy wall .4130 will not last very long on the street because memory compare to mild steel .take a one foot peice and bent it and will not bend back to a netural state many time before failure. compared to mile steel DOM have a good memory that is why NASCAR used it in all their rollcage. because went one those 3800lb car flip over and over the cage is still in one piece bend but not broken (DOM mild steel).A NHRA top fuel car crash the chassis will some time break in half because it weight 1900lb (4130 chromemoly) they are looking for lite-weight.you take 11/2x.085x12 long(4130)has more strengh that 11/2x.125x12 long but the 4130 is lighter but it will work harded and break.Indy car will only use 4130 on chassis parts only and small prop air planes. I hope this help you

kendall