Last post on Aug 28, 2003 at 4:11 PM
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Aug 27, 2003 (8:30 am)
I've worked on small aircraft and the standards are considerably higher for mechanics and what they are supposed to do and not do. Also, everything on a plane is light AND strong. It's the "AND" part that makes the parts expensive, not the "light" part. Some automakers get the light part right but not the strong part.
My personal opinion is that rotor thickness plays a large part in rotor life. That thickness can be achieved a number of different ways (design-wise) but I have seen some pathetic rotors on certain new cars. They seem more interested in making them look nice than in giving them durability.
Aug 27, 2003 (9:32 am)
The aftermarket is quick sand! We can pay anywhere between $27 and $106 for what to the layman looks like the same rotor.....Weight of rotor [same style can vary by 2.25 pounds] and the ratio of metal to air space to metal is the clue in vented units.
#33 of 40 workmanship has to count, too
Aug 27, 2003 (10:21 am)
after all, you can cast a lot of voids into a rotor that will crack or shatter if you don't give a (hoot). a reputable parts house won't continue to stock creepy crud in which half of the product sold comes back as DOA the same week.
Aug 27, 2003 (9:11 pm)
Comparing aviation to automotive is like comparing apples to oranges.
There are alot of requirements in aviation.
Those requirements are not there in automotive.
Not everyone carries torque wrenches, but EVERY tire shop should have them. If nothing else for liability concerns.
I have torque wrenches that range from $150-$650 (1/4" dial to 3/4" 600 ft/lb.) and all of them are sent in every 6 months for re-cal.
If I pull a tire, I may use a torque wrench or a torque stick, but all lug nuts get torqued.
#35 of 40 Rear drums
Aug 27, 2003 (9:22 pm)
Funny thing this, I had my wheels rotated and some months later my car started to pulsate when braking lightly at low speeds. The car a Cavalier which, by the way, has given me good service for 4 years, has discs up front and drums at the rear.
Now I would have thought that the discs had been warped. Not so - the rear drums were the culprits. I proved this by lightly pulling on the parking brake while rolling to a stop.
A new set of drums solved the problem. I also noticed that the cheaper drums were pressed out and were manufactured in a South American country. The story I got was that these countries buy the stamping dies cheaply from manufacturers after they go out of specification after so many operations.
So either the drums had become out-of-round or the mounting surface had become warped. Anyway, it beats the heck out me as to why it happened. For sure, the lugnuts were over tightened but I still can't fathom out the mechanics of the process taking place when nuts are over torqued.
#36 of 40 ever see a set of stamping dies?
Aug 27, 2003 (9:28 pm)
big monstrous chunks of steel, forklift weight, I have never seen a die set that wasn't two feet square, unless you are talking about electrical connector forming dies. and those were the size of boxer's fists. they are treated like crystallized dynamite. worn dies are filled with new metal by one of several welding methods and reground. tooling is expensive and kept in shape.
I doubt they are selling production dies overseas. rather, we have some folks doing reverse engineering overseas from a sample, and their products are at best three stages removed from US production.
BTW, drums and rotors are cast metal in the case of every car I have ever bought. check 'em out for balance holes drilled in various odd places, a hallmark of casting parts that need to be balanced.
the parts you had malfunction were cheap cheat jobs.
#37 of 40 brake drums
Aug 28, 2003 (6:13 am)
Well, that's the story the counter man gave me about the dies and who am I to argue? Anyway, he also showed me the cheaper drums and it was pretty obvious that they were stamped out.
After stamping out the drums are machined and you could clearly see where the the chuck of the lathe had gripped the outside of the drum. It's possible that at this point where the mounting for machining is critical, that any offset will be reflected in a wobbly or egg shaped drum.
No - there were no balance holes drilled in the stamped out drums.
No - the drums that got warped on my car were factory fitted drums and not cheap cheat jobs. There were balance holes and weights fitted to them - a sign that they were cast. I bought the car new in 1999.
#38 of 40 can't believe they try to sell stamped brake drums
Aug 28, 2003 (10:48 am)
might as well offer a paper-mache set.
good to see you weren't taken in by the scam.
#39 of 40 stamped discs and drums
Aug 28, 2003 (1:03 pm)
It was pretty clear that they were stamped out because the 5 mounting holes had sharp edges where the the punches had exited and the counter man told me that they were indeed stamped out.
Which brings to mind another thought. Any stamped out drum or brake disc must of necessity be softer than a casting. If you are going to stamp out a part the material has to be malleable hence softer.
A casting can be made of high carbon steel and a good brake drum or disc can crack if given a hard enough blow. You cannot stamp out a form made of high carbon steel. I suppose stamped discs and drums will just dent if given the same blow. Maybe that's why discs and drums don't last so long any more. They're too soft. I'm no expert on the subject so please correct me if I am wrong.
#40 of 40 well, you are absolutely going to warp plate steel as drums
Aug 28, 2003 (4:11 pm)
absolutely, it will happen... when heated, steel tries to return (poorly, but it tries) to its original shape, following the grain. cast metal is more resistant.