crop

Hi all, I start this topic because I'm going mad on the frequently worn out cup joints. The stock ones in center drivetrain simply worn out in 5 tanks so I replaced them with so called "hardened" ones
here's the link:http://www2.towerhobbies.com/cgi-bin...&I=LXFYL1&P=ML
in the hope of getting rid of the quick worn out issue once for all, but I felt screwed when I notice a slight bite on the surface only after a tank of running,.the unlucky feeling didn't last long when I found they worn out bit by bit each time I ran my savage, as fast, if not slower, than the stock ones. Now I've been through several pairs of these "hardened" cupjiont. A couple of days ago a friend recommended me for some hardened diff cups
[link=http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXGJU3&P=ML]click here to see[/link]
,and I bought 2 sets since the stock ones have been working over 1 year and worn out ever since. To my disappointment, they wear again, from the edge, I know they can't last long enough.
My question is, why are they making this piece of junk and call it"hardened" yet they keep wear out as fast as stock ones in spite of its's shining rather than black? I notice my friends' savages all suffer this issue, but those with LST won't. There must be something wrong, either I or HPI.
Tell me how's the jiont cups going on on your savages and feel free to share your comments, thanks.

Wizz Kid

what motor do you have?

Starcraft-IX

Wow, I've got 2 or 3 gallons on my savage and I can definately see wear, but it isn't bad at all yet. Wearing them out in 5 tanks? Are you running in sand? I can't imagine anything that would cause them to wear that quickly. Are you sure nothing is binding in your drive train?

crop

Well I found this issue since my first brand new SAVAGE SS with s-25 engine, I swear I ran it OK and didnot bash too hard, most of the time I run it in the track, some on grass and pavement. Yes it didnot wear that fast, neither so slow. Then I shifted to SH 28, now STS 28, the cups are eaten up fast as if they are made of sh**. I take much care of my car and I do inspection everytime before running, there's nothing binding, gear mesh OK, the wheels can spin freely. Man, I'll going crazy on this issue, they are not cheap, and I have to take the car apart from time to time to replace them. BTW, I didn't mean they are so worn out as to lead a failure in drivetrain, they can still work, but I hate the "bling bling" noise made by the dogbone clicking in the cupjiont and I know everytime they hit the cupjiont hard they cause a sudden impact to the whole drivetrain, leading to a premateure failure of CVDs and diffs. It's noticeable when I pull the trigger, the engine howls but car doesnot move instantly:the dogbone take some time to hit the cupjiont during which it accelerates, and when it hits the cupjoint, the car jerks in a sudden and move out. All I want is a smooth running and a longer drivetrain life, but I find now way to get rid of this problem.

DaveG55

Well, If you're having trouble with the hardened cups as they are then maybe you could try retreating them.
The cups would need to be heated to 900 deg. C then dunked in water. That will make them extremely hard BUT brittle. Next you need to temper them. To do that they need to be heated slowly to 200 deg. C and left for 1 hour at that temp then allowed to cool naturally.
It may be extreme to try this yourself but if nothing else is working...........what have you got to lose?
For more info, do a google search on "tempering steel".

crop

Thanks Dave, that's exactly what I plan to do. I'll try a pair of them as an experiment.Thanks for the information

MBX5T Maniac

My Feedback: (-1)

how exactly would you heat the things up to 900 degrees?

tmodlin

Oxygen/Acetylene torch.

DaveG55

That's how my daddy taught me to do it. Also, every temp has a specific color that the metal turns. My father was VERY good at judging temp from color. I am not, I just try to get close. and, I would not even attempt to try to describe the color that needs to be reached on an internet fourm board.

gerwen

What effect does this have on the steel?

I know about heating and quenching to harden. I know you can also case harden by using powdered carbon in the process.

It would seem to me that the heating and slow cooling would remove some of the hardness that you achieved with the high temp/quench hardening. Is that what it's doing? Backing off the hardening process a bit so the finished product is a little more flexible (less brittle)

Also, I'd like to explain to the others, that when you said brittle, you meant brittle for steel. It's still very very hard, and won't deform with less force than it originally would have. When the original steel would bend, the hardened steel may break.

/in a hurry, so if i'm hard to understand, sorry.

DaveG55

Gerwen,
Yes, exactly, partially reheating the piece and allowing it to cool naturally (tempering) gives the piece a bit more resilence by removing some of the "hardness".
A couple other intresting points.
If you are unsatisfied for some reason you can reheat the steel to 900 deg.C and let it cool naturally and it will return to it's natural, unhardened state.
You can also use other liquids, like oil, for quenching to acheave different properties in the steel.

tmodlin

Like Dave said, if you heat up to a high temp and immediatly quench in water or oil or whatever else you will harden it and also make it more brittle. The second step that he refered to keeps the hardness but removes some of the brittleness. Yes the steel will still be strong but it will be more brittle and could crack on a bad landing of something. The hardness helps with wear and tensile strength not impact resistance.