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We broke one at 6K, back in 76, but it was at 720HP.....
The owner told me he couldn't believe it! (Although he was happy as HELL TOO!)
*I* wasn't happy because he charged ME for the u-joint and shaft replacement!
Haven't been in a dyno room since, well, I did walk through KSR's dyno room, but it was quiet then.
Don
"Let me say it as simply as I can: transparency and the rule of law will be the touchstones
of this presidency,".. Barack Obama January 21, 2009, 30 minutes before he signed the law
sealing all his personal information....
Class 11 streeter wrote:The Dodge Power Wagon crowd absolutely WORSHIP Dana/Spicer drivetrain parts as being "unbreakable". Jeep freaks use that stuff too........no wonder, that $h*t's expensive! Wait till someone tells them about this!
Yea but whens the last time a Dodge or Jeep powertrain saw 6300 RPM at the driveshaft!
Well, for once I can chip in with some usefull information, based on my earlier "profession" as a farmer!
Billy is about right on ! - these needlebearing "poweraxles" are NOT designed to work at such high rpm for longer periods of time. Short bursts, OK.
The reason´s are that the grease simply cannot stay "in position" at the G force at the given rpm. Therefore is seeks outwards and leaves the needlebearings dry. After a while with this kind of load the bearings get a little worn hence creates a little slack that develops a slight misbalance. Which again creates a vibration at a node about ½ the rpm of the shaft. This ultimately BREAKS the eyes of the jaw.
These types of axles are not designed and normally cannot endure constant load of that amount at more than about 2500 rpms. But below that, they can handle A LOT of torque.
So, in order to avoid this happening again, replace the needle bearings at say 150 hrs. 200 max. along with keeping them greased with f.i. Shell S4000 grease (High density "longhaired" grease)
If you want equivallent products in other brands, let me know and I´ll convert the #´s to you.
Torben
I use Mystik JT8 grease on the entire dyno... The U joint did not break, the yoke snapped right off, I could see a hairline crack that had been there for a while but we never caught it till it snapped.
The u joints have been on for 2 years and 3 months... the aft U joint was removed and inspected and was still fine. The front yoke simply yielded from me dropping the hammer so hard all the time.....
I'm going to have the shaft, joints and yoke cryoed next week after this is all done.
I´m not familiar with Mystik, but I´ll look it up.
But I am pretty sure that the small crack of older date that you can see, relates to the nodes I´m talking about.
I´ve seen this happening at just over 2k rpm´s at that rpm rate it´s visible, at least when the torque pull is high. Something like a constant max pull of a 200 hp turbocharged tractor pulling through a 1-2 ratio to create the rpm. The shaft simply starts swinging with the node. (These were much longer shafts though. Up to 7 feet) But still quite scary.
T.
One thing that can be seen on the pictures is that the yokes on each end of the shaft is at an 90 degree angle to each other, i think they should be paralell too avoid vibrations.
You need to have at least a 7 degree angle with U-joints. Not only for the grease to travel, but for the harmonics, they become extreme on a straight/level axle. I'd be willing to bet that it was the harmonics caused at that amount load.
I would run a Datsun 280Z axle, shortnend. They are good for at least 400HP and you don't have to worry about greasing the damn thing. It has STRONG CV's. Angle is not very important with them either. Bolt pattern is easy to drill, trust me, you'll like it. I've seen beetle drag cars running them with 250+ HP turbo motors and launching with slicks.
