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Unread 01-01-2014, 02:45 PM   #106
mrblaine
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Quote:
Originally Posted by Necromancer_tat View Post
Yes, as my speed was lowered to 65 mph, I never again had any kind of wobble at all going over the same section of bumps on the highway. I agree that with greater speed the angular momentum increases when hitting something that makes the tires deflect. That's why in other motorsports circles it's called "speed wobble" instead of "death wobble" but Precession by itself doesn't sit well with me when I picture the entire ovrall event that is DW, I'm sure it does play a part, but I don't think its as significant as you hold it to be.

Picture a man on a unicycle, he's riding down the road and hits a bump that bounces him one way or the other... if he's skilled at riding he'll just cope with the bounce, lean whichever direction he needs to correct things, and keep pedaling down the road. If precession had such a violent effect as you're hypothesizing, the unicycle rider would go into violent shakes every time he hit an uneven surface.
Once you find an example that supports your position, you just find it almost impossible to move past it, don't you? Your buddy on the unicycle is atop a wheel that is smallish diameter and weight comparatively with a much lower speed. The angular momentum that develops in your scenario is much less than what even a normal bicycle has to deal with.

All the examples I've dug up for you are based on a perfectly balanced gyro with enough structure to support them so we can see the effects direction change has to create precession.

What size would that support structure have to be with a 35" tire on a steel rim spinning at 60mph with one tire out of balance? Would you even want to be in the room with it?

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Unread 01-01-2014, 04:23 PM   #107
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Originally Posted by mrblaine View Post


What size would that support structure have to be with a 35" tire on a steel rim spinning at 60mph with one tire out of balance? Would you even want to be in the room with it?
Funtech#3 lol

Thank you guys for teaching me what precession is, I didn't know, quite interesting.
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Unread 01-01-2014, 05:33 PM   #108
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Quote:
Originally Posted by mrblaine View Post
Once you find an example that supports your position, you just find it almost impossible to move past it, don't you? Your buddy on the unicycle is atop a wheel that is smallish diameter and weight comparatively with a much lower speed. The angular momentum that develops in your scenario is much less than what even a normal bicycle has to deal with.

All the examples I've dug up for you are based on a perfectly balanced gyro with enough structure to support them so we can see the effects direction change has to create precession.

What size would that support structure have to be with a 35" tire on a steel rim spinning at 60mph with one tire out of balance? Would you even want to be in the room with it?
There are a lot of other forces that come into play on the front end of a vehicle other than precession. I agree that it's there, and I agree that with larger tires and higher speeds the force it's able to exert into the system is higher. I just don't think it's the primary culprit.

Picture an IFS mud truck running 44" Swamper bias ply tires that just got done playing in the local mud hole. Said truck is driving home with 10 lb's of mud inside each front rim and the tires are wildly off balance. IF precession was the primary culprit, said mud truck would have two bad cases of DW with each one of his front tires trying to wobble themselves right off the spindles.
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Unread 01-01-2014, 05:36 PM   #109
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Originally Posted by Necromancer_tat View Post
There are a lot of other forces that come into play on the front end of a vehicle other than precession. I agree that it's there, and I agree that with larger tires and higher speeds the force it's able to exert into the system is higher. I just don't think it's the primary culprit.

Picture an IFS mud truck running 44" Swamper bias ply tires that just got done playing in the local mud hole. Said truck is driving home with 10 lb's of mud inside each front rim and the tires are wildly off balance. IF precession was the primary culprit, said mud truck would have two bad cases of DW with each one of his front tires trying to wobble themselves right off the spindles.
Again, not if the components are strong enough to withstand the forces acting upon them.
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Unread 01-01-2014, 05:50 PM   #110
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Originally Posted by mrblaine
Again, not if the components are strong enough to withstand the forces acting upon them.
And in the case of the IFS mud truck the pitman/idler assembly would fail and you'd have DW... This has been a great conversation, reaffirmed many beliefs I have had regarding DW but didn't have the technical knowledge to really express it or fully comprehend.
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Unread 01-01-2014, 05:53 PM   #111
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Again, not if the components are strong enough to withstand the forces acting upon them.
I agree. Even if it was invisible trolls shaking the tires from side to side, if the components are strong enough to handle the forces there won't be any wobble.
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Unread 01-01-2014, 06:00 PM   #112
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Originally Posted by mrblaine View Post
You said that wrong. Will he be missing something?
Now that was funny!...
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Unread 01-01-2014, 06:01 PM   #113
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Lols sorry I missed the action, a few funnies I was driving all day to the inlaws for the rest of the week

Necko, swap's all wrapped up. Motor seems good. Having the front driveshaft rebuilt locally and then I am hoping to get back to working on the Jeep because I WANT to rather than because I NEED to.

To the recent on topic, I have witnessed DW in an IFS....I was all like "WTF?" Lol.
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Unread 01-01-2014, 06:53 PM   #114
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Wow what a thread.

I had my front body mount break and I didn't notice it was broken for quite sometime and the only way I knew it was broken was when I hit a big bump which caused the front end to shift which busted my fan shroud. I never had any sign of DW before during or after the repair.
Tough to believe the busted body mount could cause DW.
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