Homocineticas reforzadas.-

[Gonzalo Bravo]

Estuve leyendo por ahi que algunas de las famosas Marfield, Longfield o como se llamen, son una homocietica tipica que le soldan o un anillo o simplemente rellenan con soldadura, para luego hacerle un tratamiento de temperatura y asi darle mas cuerpo.

Yo probe los anillos prensados y no me funcionaron. Entonces, si es tan asi porque no hacerlas uno? Mis dudas son:

Se puede desarmar una homocinetica Toyota, eso es, sacar el canasto y las bolas?
Se podra soldar armada?
Porque podra ser que el tratamiento de temperatura de las que venden (Longfield) es de 53RW (escala de Rockwell) si el de las originales es de 63RW?
Las Longfield se puden sacar como las originales sin sacar el Knucle?

Seria bueno si alguien puede averiguar en Santiago el tema de los tratamientos de tº para que entendamos como es. No creo que mientras mas duro sea mejor, ya que se quebraria mas rapido. Alguien puede?

[Gonzalo Bravo]

Ummm, aqui me fregaron :?

"Everyone who has wheeled a Toyota, knows about the birfield joint. It is the joint in the front axle housing of a 1979-85 Toyota pickup that connects the inner axle shaft to the locking hub enabling the wheels to turn from side to side. It is also the weak link; in the Toyota drivetrain. If you are a hard core 4 wheeler and choose to drive a Toyota, you have no doubt broken a birfield joint while on the trail.

A few people have tried to improve the birfield joint by reinforcing the outer shell. This makes the outer shell stronger, but does nothing to improve the strength of the inner and outer bearing cages, located inside the shell. The bearing cage usually fails, damaging the outer shell beyond repair. This has always been the problem with stronger birfields.

The second fix for the birfield problem is the birfield eliminator kit. So far, 2 companies have tried using a Spicer #297x u-joint in place of the birfield with fairly good results. The only problem is, both companies have discontinued selling the kit for various reasons other than reliability.

2 weeks ago, virtually out of nowhere, came a guy named Bobby Long, from Graham Washington. He claimed that he has designed an unbreakable birfield. Infact, he is so confident in his birfield design, he is offering it with an unconditional, free replacement guarantee if it fails for any reason other than just plain wearing out.

As I was rolling my eyes and saying to myself Yea right, Another unbreakable birfield, my fellow club member called Mr. Long and got him to send us a set to field test out at the legendary Hammer trails located in Johnson Valley, Ca.

When I unpacked the Toyota super axles I found that they were a stock Toyota birfield joint with a ring welded on the outer lip of the shell just like the first generation Marfield joint that Marlin Crawler marketed a couple years ago. I had heard rumors that these birfields limited turning radius, and since birfields usually break when they are turned, that is how they were getting them to hold up so well. I put one side by side with a stock birfield and placed an axle shaft in each. When I moved both birfields until the axle shaft contacted the outer cage, I found that the stock birfield would let the axle shaft move a lot farther than the super birfield. It was also obvious that even though the ring on the super birfield was limiting how far the axle moved, it WOULD NOT limit steering when it was installed in the knuckle because it would still move farther than a Toyota knuckle ever would.

I installed the super birfields in my axle housing and adjusted the steering stops to where the front tire would just contact the front of the leaf spring when turned, then I headed for the Hammer trails. We met up with the guys from All-Pro off road and found out that Terry Baker was testing a set of Bobby´s super birfields also. My rig has a 22re with 150:1 crawl ratio, ARB in the front, spool in the rear and 38.5x14.5x15 Super Swamper TSL/SX tires. Terry's rig was set up similar with 37" tires.

We ran Wrecking Ball with no problems at all. That night I ran SledgeHammer and the next day I ran JackHammer. With other peoples rigs popping birfields, rolling over and breaking (Dana 60) axles, I had no problems at all. I didn't intentionally try to break these super birfields, but at the same time I wasn't being easy on them either. I bound it up a few times (like only the Hammers can do) to where a stock birfield would have failed. To my surprise, I completed the weekend with the same birfields that I arrived with.

When I returned home, I called Mr. Long and asked him what makes his Super birfields hold up so well. He replied "heat treat". He told me that a stock birfield was heat-treated to a 65 Rockwell hardness (that is as hard as a file). He explained that he re-heat treats the inner cages to soften them and then he has them cryogenic hardened. Cryogenic hardening is done by dipping the part in liquid nitrogen and freezing it to -300 degrees. He also re-heat treats the outer shell and at a certain temperature, he stick welds the outer ring on with a "special rod". All of this produces a "Super birfield". These birfields have been tested on a special machine and were able to withstand 10,000 pounds of torque at a 30 degree angle without breaking. Pretty impressive I must say.
With all this information, and even testing them myself, I would like to be able to tell you that these are the "end all, be all" solution to your birfield problems. But I know better than that. Let me just give you the facts. The positive things are:
- These super birfields are stronger than a stock one.
- They come with an unconditional, free replacement warranty.
- They cost ½ the price of any other alternative. If one breaks, just replace it with a stock one and you're off.

The negative things are:
- The next weak link will either be an axle shaft or a ring and pinion."

[José Manuel]

Empezado por Gonzalo Bravo

No creo que mientras mas duro sea mejor, ya que se quebraria mas rapido. Alguien puede?

En cuanto a tratamientos de calor, la teoría dice que mientras más duro es un material más fragil es. Por lo tanto, con un aumento de dureza puede que el material no resista la torsión que se produce.