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post #1 of (permalink) Old 01-06-2005, 10:28 PM Thread Starter
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Drunken Gear Ratio Torque Physics Question

Alright, I've had a few beers and am trying to figure this out.

In a series of gear reductions, are u-joints more likely to brake before or after a gear reduction. (asuming the joints are in the "straight" position)

I have heard guys that run 9" mogs say that the u-joints in the hub sections are "shielded" by the gear ratios and are less likely to break. ... Why?

Isn't there more leverage given to the drivetrain by a gear reduction to blow stuff to crap? Or is the shock load from a bounce transfered inversely throught the reductions?


Any thoughts?


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post #2 of (permalink) Old 01-06-2005, 10:34 PM
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Re: Drunken Gear Ratio Torque Physics Question

I would have to be drinking to answer that.... Only thing I can see is wouldn't the ones at the hub have less of a shock load on them?? You know engine up/down/up/down,,, Who Knows give me a beer.
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post #3 of (permalink) Old 01-06-2005, 10:49 PM
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Re: Drunken Gear Ratio Torque Physics Question

i would say there prolly more risk AFTER the gear reduction..... there more torque there so thinks break more......before the reduction theres less torque but they are moving faster

its the same idea behind why you need thicker shafts after gear reduction .....hence why your axles break before the output of your engine

so if the U joint was before the planetary then it would in fact be shielded

its late here but i think im right
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post #4 of (permalink) Old 01-06-2005, 10:56 PM
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Re: Drunken Gear Ratio Torque Physics Question

in reply to Jeff's......

the U joints earlier in the drive train would be more likely to fail due to high cycle fatigue (high repetitions of a smaller load ammount) while the u joints after the gears would be more likely to fail from Low cycle fatigue (lower repetitions of a more dramatic load)
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post #5 of (permalink) Old 01-06-2005, 11:59 PM
 
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Re: Drunken Gear Ratio Torque Physics Question

I was of the understanding that the portal box is part of the knuckle, and therefore after the u joint?

That means less torque on the U-joint (stress) but more wear and tear due to cycle fatigue [img]images/graemlins/smile.gif[/img]
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post #6 of (permalink) Old 01-07-2005, 02:15 AM
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Re: Drunken Gear Ratio Torque Physics Question

Try reading THIS...
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post #7 of (permalink) Old 01-07-2005, 02:57 AM
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Re: Drunken Gear Ratio Torque Physics Question

[ QUOTE ]
I have heard guys that run 9" mogs say that the u-joints in the hub sections are "shielded" by the gear ratios and are less likely to break. ... Why?


[/ QUOTE ]
The reductionbox inside the wheel comes after the U-joint, So the torque is less on the U joint and full inside the wheel where no U-joints are needed as the box is inside the wheel. Instead of only a reduction in the TC, a Unimog has 4 extra. 1 Inside each wheel.
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post #8 of (permalink) Old 01-07-2005, 04:51 AM
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Re: Drunken Gear Ratio Torque Physics Question

you just need to stop thinking... this is obiviously interfering with your drinking...
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post #9 of (permalink) Old 01-07-2005, 07:17 AM
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Re: Drunken Gear Ratio Torque Physics Question

[ QUOTE ]
you just need to stop thinking... this is obiviously interfering with your drinking...

[/ QUOTE ]

my thoughts exactly!
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post #10 of (permalink) Old 01-07-2005, 09:36 AM
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Re: Drunken Gear Ratio Torque Physics Question

heres another factor though.....
I have seen folks with very low gears walk up sheer faces of rocks, and right behind a guy with high gears blew his driveshafts apart.. why???? well.. I have a theory...
the guy with low gears kept the tires turining very slowly.. the stress never bound .. never accumulated. the guy with high gears had to gas it.. gas it.. gas it.. till finally there was a tremendous amount of stress on the drivetrain and the driveshaft failed.... I was thinking this is because the wheels of the low geared rig didn't have to turn nearly as much as the wheels on the high geared rig to move each vehicle... the high gears were trying to move a whole lot at once...
sooooo...
would portals make less stress on u-joints???
yes. the gear reduction in the portals would cause the tires to turn less.... effectively needing less work for the desired movement.
this might only be in a situation where the wheels are wedged..
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