Half A Burnout żżż
Senior Member
Joined: Feb 2000
Posts: 1,544
Likes: 0
From: Kalamazoo, MI, USA
In order for your truck to be able to turn left/right without scrubbing a tire (due to the difference in radii that the two wheels take in the the turn), your ring gear carrier contains another set of four gears -- each mounted on a common "cross" -- which is mounted in the carrier -- and rolls with the carrier.
The four gears (also known as the "spider gears") on the cross (a.k.a.: Spider) are there so that the left axle can turn at a different speed from that of the right axle during turns.
Due to a simple gearing concept that is not so simple for me to explain, the spider gears force the combined speed of the two axles (and, of course, the two tires) to be the same as the speed (rotation) of the ring carrier.
What this means is not immediately apparent -- but is really important -- and I'll give a couple of examples.
Suppose you're doing a nice burnout -- and your speedo (assume it gets it's signal from the transmission) tells you that you're spinning at 70 MPH -- but you know that you're not moving (cuz you've got your foot on the brake and the truck's not moving -- and your left tire is not turning -- but your right tire is smokin' like crazy).
Your spinning tire is actually spinning at 140 MPH because your other tire is stopped -- and the formula constant is:
Ring Gear RPM = (Fast Wheel + Slow Wheel)/2
So if you're spinning at an indicated 70 MPH and your slow wheel (and vehicle) are moving at 10 MPH, your fast wheel is turning 130 MPH.
If you're spinning at 70 MPH and your slow wheel is spinning 30 MPH, your fast wheel is spinning 110 MPH.
You get the picture?
What is not immediately apparent is that the little spider gears are spinning like crazy on the spider (a.k.a. cross) -- in order to do that "divided by 2" part of the formula -- with the significance being that they are designed to rotate only during vehicle turns where the wheels are rotating at slightly different radii.
In English, this means:
You'll Fry Your Spider Gears!
This is called "Spin-out" damage.
It is difficult to properly lubricate gears spinning at those fast speeds -- and the gears can actually turn blue from heat, friction-weld to the cross (spider), or change the heat-treat properties such that some day when you least expect it, they simply crack and disentegrate -- with the result usually being that no torque is applied to the wheels.
In short -- single-wheel burnouts are risky -- and the sudden stop of the spinning wheel while under power really adds shock to the spider and gears -- and the spider (cross) frequently cracks/breaks.
(I enjoyed the burnout pix, however.)
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Y2K Jim - N8JG@Hotmail.com
Toreador Red, Keyless XLT SC SB 5.4L E4x4 4wDisc/ABS, 3.73LS, Skid, HD 7700# Towing, LT-245's on Chrome, Tube-Steps, Captain's, 6CD, Tonneau, named: "Nick"
The four gears (also known as the "spider gears") on the cross (a.k.a.: Spider) are there so that the left axle can turn at a different speed from that of the right axle during turns.
Due to a simple gearing concept that is not so simple for me to explain, the spider gears force the combined speed of the two axles (and, of course, the two tires) to be the same as the speed (rotation) of the ring carrier.
What this means is not immediately apparent -- but is really important -- and I'll give a couple of examples.
Suppose you're doing a nice burnout -- and your speedo (assume it gets it's signal from the transmission) tells you that you're spinning at 70 MPH -- but you know that you're not moving (cuz you've got your foot on the brake and the truck's not moving -- and your left tire is not turning -- but your right tire is smokin' like crazy).
Your spinning tire is actually spinning at 140 MPH because your other tire is stopped -- and the formula constant is:
Ring Gear RPM = (Fast Wheel + Slow Wheel)/2
So if you're spinning at an indicated 70 MPH and your slow wheel (and vehicle) are moving at 10 MPH, your fast wheel is turning 130 MPH.
If you're spinning at 70 MPH and your slow wheel is spinning 30 MPH, your fast wheel is spinning 110 MPH.
You get the picture?
What is not immediately apparent is that the little spider gears are spinning like crazy on the spider (a.k.a. cross) -- in order to do that "divided by 2" part of the formula -- with the significance being that they are designed to rotate only during vehicle turns where the wheels are rotating at slightly different radii.
In English, this means:
You'll Fry Your Spider Gears!
This is called "Spin-out" damage.
It is difficult to properly lubricate gears spinning at those fast speeds -- and the gears can actually turn blue from heat, friction-weld to the cross (spider), or change the heat-treat properties such that some day when you least expect it, they simply crack and disentegrate -- with the result usually being that no torque is applied to the wheels.
In short -- single-wheel burnouts are risky -- and the sudden stop of the spinning wheel while under power really adds shock to the spider and gears -- and the spider (cross) frequently cracks/breaks.
(I enjoyed the burnout pix, however.)
------------------
Y2K Jim - N8JG@Hotmail.com
Toreador Red, Keyless XLT SC SB 5.4L E4x4 4wDisc/ABS, 3.73LS, Skid, HD 7700# Towing, LT-245's on Chrome, Tube-Steps, Captain's, 6CD, Tonneau, named: "Nick"