broke spindle

[455bird]

Have any of you seen this happen? My spindle broke in haft at the biggest part. As you may be able to see it broke flush but if you look real close it look like it had so metal fatigue in it. Look down the center of it. What do you all think?

[fabr]

I'm no expert but when I was running my automotive machine shop we had an occasion to need a valve failure analyzed.  The fracture have looks identical except it has begun in 2 places instead of 1.  See the dark areas at the top and bottom of the stub?  That is where the problem began.  It was likely a stress fracture happened as it was cooling from the welding in those areas.  It then flexed in an up/down fashion and then it simply fell off after enough cycles.

[Engineer]

I agree with Fabr.  It is hard to tell from the pictures, but it looks like the fresh break (rough area) is just a narrow strip across the middle. 

I am not sure but it looks like the spindle was turned down in size right where the break occured.  If there was no radius where it was turned down it could have caused a stress point.  Also the weld could have caused stress as well as carbon buildup, especially if the spindle is 1045 which many are.

I have heard the crome process can cause problems as well, but I don't know the details.  Many NHRA teams quit croming parts, but I am not sure exactly why.

To aleviate the problem, radius all diameter changes, and preheat the spindle before welding on it, to reduce stress risers.

[VLADD]

What Fabr and Engineer said,
It's surprising how a small radius can improve the strength of a part I was schooled in that the hard way myself designing my own spindles 

[fabr]

The reason for not chroming highly stressed parts is that the chrome is very brittle and any flexing of that part will likely crack the very hard chrome and allow that crack to easily spread into the base metal.If I'm not mistaken NHRA banned chrome on cage and suspension parts many years ago for just that reason.

[dsrace]

I bought 3 pair of weld on spindles from prowlers speed and custom first of Jan 08. these spindles were supposed to be 4130 chromoly but turned out to be mild steel. there rep told be they were made out of 1045 cold rolled shaft or at least he thought.

the first set of spindles made two days before they bent down, smoked a set of spindle bearings and began cracking in the exact same spot your did in the pic above. the other two pair of spindles were on v-6 rails and didn't even survive two pass's on the dirt track before they began to bend.

in my opinion you have to use at least 4130 chromoly on the spindles. I personally use 4140 and have had no problems in 8 years, until I got tired of making them myself and tried to use prowlers speed and custom's weld on spindles. When I called them 6 different times, they wouldn't do anything about it. in fact they said they have heard of this problem before but it's rare.

[fabr]

Well if you wouldn't abuse them they'd be fine! You know keep the buggy  in the parking lot as bitch bait. LOL!!

[Dunebound69]

Not to run off track but it looks like 455 bird has studded heims in his a-arm.  Watch out for thoses studded heims. I took them off my car. They would pound themselves out. I thankfully caught it before they let go.

[Admin]

The reason for not chroming highly stressed parts is that the chrome is very brittle and any flexing of that part will likely crack the very hard chrome and allow that crack to easily spread into the base metal.If I'm not mistaken NHRA banned chrome on cage and suspension parts many years ago for just that reason.

actually you are wrong on that theroy, I will find the technical shit, When you chrome something it encapsulates a gas in the part, which causes fatigue later on, You have to heat treat a chrome part to make it strong again...I dont remember all the specifics but i will dig them out...

[fabr]

WOW,good call on the heims.I totally missed that.

[fabr]

[Admin]

I'm always up for an education update.

I have read about this time and time again in the hot rod scene...

How it works...
Tensile strength is the pulling of a material until it tears apart. The higher the tensile strength, the more susceptible it is to embrittlement. When you chrome a part, hydrogen is soaked into the material as it is plated, the plating then holds it in. Once inside it will spread to all areas, where it is relatively harmless. When stress is applied, the hydrogen re-distributes itself, concentrating on the point of stress. Think of it as trying to escape, and its only way out, is a crack. Metallurgists do not know how a crack is formed. That is still in debate. The moving and concentration however,  is not. "Presently this phenomenon is not completely understood and hydrogen embrittlement detection, in particular, seems to be one of the most difficult aspects of the problem. Hydrogen embrittlement does not affect all metallic materials equally. The most vulnerable are high-strength steels, titanium alloys and aluminum alloys."

When enough hydrogen accumulates, and a crack is established, it focuses on the end points of the crack. Until it becomes so weak that the end of the crack moves, the hydrogen then follows to the new highest stress point. The new end of the crack. Until the whole thing fails suddenly.

Low allow steels (LAS), like 4340, and 4130(chrome-molly) are the MOST susceptible material to this phenomenon. Strangest part of hydrogen embrittlement is that the stronger the material, the more likely it will fall victim. The new Supertherm, Platinum OX, and Reynolds tubing, is just modified 4130, with an even HIGHER tensile strength.


There is a fix...
Only its not pretty.. Literally. The most common method is to bake the parts. Baking a part at 375 +/- 25 deg. F. for 3 hours will usually correct most of it. Now, your thinking you can just put your frame into your oven..  Wrong.. It MUST be done within 1 hour of plating.  This only works if the plating is porous enough, and it will make the chrome turn bluish. Ever see chrome headers on a car...  Not to mention, since its decorative chrome, it will likely NOT be porous enough, and will drive the hydrogen deeper into the tubing. Making things worse.

[Dunebound69]

Experience can be one hell of a teacher. She shows no favorties.

[fabr]

OK I hear your theory and completely understand hydrogen embrittlement but chroming is done at a much lower temp than welding so why or how would the base metal be effected by the hydrogen gas in the plating process? Just asking and would be very interested in reading more on the subject. Can you provide any links to more info? 

[Admin]

OK I hear your theory and completely understand hydrogen embrittlement but chroming is done at a much lower temp than welding so why or how would the base metal be effected by the hydrogen gas in the plating process? Just asking and would be very interested in reading more on the subject. Can you provide any links to more info?

I will find some more, The chroming process encapsulates the hydrogen, it cant get out, were as just welding the gas likely burns off and escapes..