Be Careful How You Box Steel 944 A-Arms!
#62
Originally Posted by M758
The ball joint is the main weak spot on the aluminum arm.
TD is right about catastophic failure. I believe he felt the car being "off" before the arm actually broke. Aluminum will tend to feel fine unit it breaks.
TD was I wrong on this?
TD is right about catastophic failure. I believe he felt the car being "off" before the arm actually broke. Aluminum will tend to feel fine unit it breaks.
TD was I wrong on this?
#63
Race Director
In my first 944 spec race I had a control arm bushing blow out. It was the black weltmeister that goes into the control arm where your broke. Anyway I ran the racing and after one tight right I would have to wiggle the steering to get the car to run straight. Everything seemed fine after that and I was in the lead so I just kept running that way for 25 laps or so. (1:10-1:11 laps).
After the race I noticed the nearlly missing bushing. Dodged a bullet on that one, and was able to replace it for sunday's race.
I find it realy interesting how crappy a car you can drive if you blindly thing "everything is fine" then you realize why the car was "off" and you are scrared like hell to drive it any more.
After the race I noticed the nearlly missing bushing. Dodged a bullet on that one, and was able to replace it for sunday's race.
I find it realy interesting how crappy a car you can drive if you blindly thing "everything is fine" then you realize why the car was "off" and you are scrared like hell to drive it any more.
#64
Originally Posted by M758
I find it realy interesting how crappy a car you can drive if you blindly thing "everything is fine" then you realize why the car was "off" and you are scrared like hell to drive it any more.
I put the car up on stands, and again could not find anything (apart from it looking like one side of the car had more camber than the other). I was so frustrated by the "too slow" comment that I forced myself to go out again, with the same evaluator, and then got warned not to be too aggressive
I did get my sign off though. Good thing that happened or my paranoia might have led me to put the car up on the trailer and go home.
There has to be a balance, but yes, I take the safety issue very seriously.
#66
Addict
Rennlist Member
Rennlist Member
Alloy Arms -
The alloy arms will rarely fail in any way but catastophically. They fail in three main ways;
A) The ball joint pulls out of the socket. This can be from either excessive wear in the joint, or from a car lowered so far that the axial travel limit of the socket is exceeded and the pin binds against the socket. If this situation persists, the wear of the socket is accelerated and the ball eventually pops out. THIS CAN BE FOUND VISUALLY/PHYSICALLY IF YOU INSPECT THEM OFTEN.
B) The top of the pin snaps at the keyway. This is generally from a spindle clamp that has been left loose, allowing the hole to become ovalized internally. The pin will rock back and forth and snap at the bolt recess. THIS CAN BE FOUND VISUALLY/PHYSICALLY IF YOU INSPECT THEM OFTEN.
C) The arm snaps at the sway bar mount area. This is generally thought to happen on cars with heavy sway bars and soft springs. The soft springs allow excessive body roll, and the over active bar pulls excessively on the alloy arm, eventually snapping it due to fatigue. THIS USUALLY DOES NOT PRESENT ITSELF VISUALLY OR PHYSICALLY. IF YOU'RE REALLY LUCKY, YOU MIGHT SEE A CRACK.
THESE ARE ALL CATASTROPHIC FAILURES.
The steel arms usually only fail catastrophically in the way Todd's did. Otherwise, they usually just bend. Nice still having 4 wheels on the car, even if all of them don't quite point in the same direction. You genrally can get lots of warning that a steel arm is going to fail, but you have to look for it specifically.
The alloy arms will rarely fail in any way but catastophically. They fail in three main ways;
A) The ball joint pulls out of the socket. This can be from either excessive wear in the joint, or from a car lowered so far that the axial travel limit of the socket is exceeded and the pin binds against the socket. If this situation persists, the wear of the socket is accelerated and the ball eventually pops out. THIS CAN BE FOUND VISUALLY/PHYSICALLY IF YOU INSPECT THEM OFTEN.
B) The top of the pin snaps at the keyway. This is generally from a spindle clamp that has been left loose, allowing the hole to become ovalized internally. The pin will rock back and forth and snap at the bolt recess. THIS CAN BE FOUND VISUALLY/PHYSICALLY IF YOU INSPECT THEM OFTEN.
C) The arm snaps at the sway bar mount area. This is generally thought to happen on cars with heavy sway bars and soft springs. The soft springs allow excessive body roll, and the over active bar pulls excessively on the alloy arm, eventually snapping it due to fatigue. THIS USUALLY DOES NOT PRESENT ITSELF VISUALLY OR PHYSICALLY. IF YOU'RE REALLY LUCKY, YOU MIGHT SEE A CRACK.
THESE ARE ALL CATASTROPHIC FAILURES.
The steel arms usually only fail catastrophically in the way Todd's did. Otherwise, they usually just bend. Nice still having 4 wheels on the car, even if all of them don't quite point in the same direction. You genrally can get lots of warning that a steel arm is going to fail, but you have to look for it specifically.
#67
Three Wheelin'
Hi guys,
Sorry to dig up an old thread. I am welding up the control arms for a 944 spec car that a few of us are putting together. From eraly in this thread-
So is this an acceptable way to reinforce that barrel? If not, where can I get the factory procedure for reinforcing them?
TIA for any input.
Sorry to dig up an old thread. I am welding up the control arms for a 944 spec car that a few of us are putting together. From eraly in this thread-
Correct procedure for boxing the a-arms (per the factory) includes reinforcing that barrel. All the 933 a-arms I've seen had that wrapped as well. Likewise, when I went into the wall last with my unreinforced a-arms, it did start to tear there. Of course, it relieved most of the stress elsewhere - a well-engineered component, IMO.
TIA for any input.
#68
Addict
Rennlist Member
Rennlist Member
Hey;
As long as it looks the same on the other side, that's just fine, Kevin. As Todd's pic shows, they fatigue right after the weld. Strapping over it solves that. Here's another example. The green arrow points to the vulnerable area, boxed in solid.
As long as it looks the same on the other side, that's just fine, Kevin. As Todd's pic shows, they fatigue right after the weld. Strapping over it solves that. Here's another example. The green arrow points to the vulnerable area, boxed in solid.
#73
Mr. Excitement
Rennlist Member
Rennlist Member
BTW Please, for god's sake stop grinding stressed and critical welds.
#74
Three Wheelin'
Thanks for the input guys. I agree that it needs to be wrapped fully to prevent the failure that started this thread. Here's how mine came out (please no comments about my lack of welding skill- the picture makes the weld look worse than they are.) It looks like it would have been better to extend the side reinforcements all the way to the barrel. Maybe I'll do that on the other side.