If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below. |
|
|
Thread Tools | Display Modes |
#1
|
|||
|
|||
Those go-roundy-roundy things in the front (4WD)
I've heard them called "front U-joints" and I've heard them called
"Constant Velocity (CV) joints". Which is the proper term? I know in FWD vehicles they're called CV joints, but I don't know why; it seems to me their velocity should change as the vehicle speed changes. Same for 4WD. -- Gordon S. Hlavenka http://www.crashelectronics.com "If we imagined he could _find_ the car, we could pretend it might be fixed." - Calvin |
Ads |
#2
|
|||
|
|||
For many years, U-joints were de riguer for the front driving axles (a
U-joint being the standard cross and cup we see on driveshafts... though there are also the ball and trunnion types as well). Universal joints have a limited range of motion and rob horsepower at high angles. The big problem with cross and cup joints is physics. As the angle through the joint increases, the part of the U-joint passing through the inside of the 'corner' must travel at a different speed than the part passing through the outside of the 'corner'. This causes the joint to oscillate and adds vibration. There are several different styles of CV joint but two are most common. The inner joint is generally a tripot joint ( a variation on ball and trunnion using three ball assemblies riding in a three groove "tulip") . This type of joint has 'plunge' capabilities and is used to allow for half shaft length changes as the suspension bounds and rebounds. It's range of motion is better than a cross and cup but still not sufficient to allow for high turning angles. Brings us to the outer CV joint.... no plunge capabilities but it does allow high angles without binding. As the name implies, the joint is in a state of "constant velocity"... i.e. the part of the joint at the inside of the corner travels at the same speed as the part of the joint passing through the outside of the corner. Even at high angles, the joint remains stable and requires much less power than the cross and roller type. While CV joints are, technically, universal joints, we still use the different terms to differentiate between those that aren't constant velocity and those that are. As for which term is correct depends on the style of joint and how it reacts at high angles of deflection. HTH "Gordon S. Hlavenka" > wrote in message m... > I've heard them called "front U-joints" and I've heard them called > "Constant Velocity (CV) joints". Which is the proper term? > > I know in FWD vehicles they're called CV joints, but I don't know why; > it seems to me their velocity should change as the vehicle speed > changes. Same for 4WD. > > -- > Gordon S. Hlavenka http://www.crashelectronics.com > "If we imagined he could _find_ the car, > we could pretend it might be fixed." - Calvin > |
#3
|
|||
|
|||
half shafts
"Jim Warman" > wrote in message news:cTFhd.41494$E93.28072@clgrps12... > For many years, U-joints were de riguer for the front driving axles (a > U-joint being the standard cross and cup we see on driveshafts... though > there are also the ball and trunnion types as well). Universal joints have > a > limited range of motion and rob horsepower at high angles. The big problem > with cross and cup joints is physics. As the angle through the joint > increases, the part of the U-joint passing through the inside of the > 'corner' must travel at a different speed than the part passing through > the > outside of the 'corner'. This causes the joint to oscillate and adds > vibration. > > There are several different styles of CV joint but two are most common. > The > inner joint is generally a tripot joint ( a variation on ball and trunnion > using three ball assemblies riding in a three groove "tulip") . This type > of > joint has 'plunge' capabilities and is used to allow for half shaft length > changes as the suspension bounds and rebounds. It's range of motion is > better than a cross and cup but still not sufficient to allow for high > turning angles. > > Brings us to the outer CV joint.... no plunge capabilities but it does > allow > high angles without binding. As the name implies, the joint is in a state > of > "constant velocity"... i.e. the part of the joint at the inside of the > corner travels at the same speed as the part of the joint passing through > the outside of the corner. Even at high angles, the joint remains stable > and > requires much less power than the cross and roller type. > > While CV joints are, technically, universal joints, we still use the > different terms to differentiate between those that aren't constant > velocity > and those that are. As for which term is correct depends on the style of > joint and how it reacts at high angles of deflection. > > HTH > > > "Gordon S. Hlavenka" > wrote in message > m... >> I've heard them called "front U-joints" and I've heard them called >> "Constant Velocity (CV) joints". Which is the proper term? >> >> I know in FWD vehicles they're called CV joints, but I don't know why; >> it seems to me their velocity should change as the vehicle speed >> changes. Same for 4WD. >> >> -- >> Gordon S. Hlavenka http://www.crashelectronics.com >> "If we imagined he could _find_ the car, >> we could pretend it might be fixed." - Calvin >> > > |
#4
|
|||
|
|||
Perhaps I have misread Jim's post about the problems with u-joints and the
advantages of CV joints. As I understand one of the primary physics issues with the two, a u-joints out put speed (velocity) is constant ONLY when the input and output shafts are on the same axis. As the angle between the two increases the speed (velocity) the output shaft becomes more and more sinusoidal. A 'constant velocity' joints output shaft speed is constant, it does not vary with the angle of deflection. Hence there is no vibration due to the varying speed. Just my $0.02 worth. Tim |
#5
|
|||
|
|||
That's the turn of phrase that I was looking for....
Just a FYI (another one of those semi-useless little factoids we can use to amaze friends and relatives).... single cardan universal joints prefer the angle through the joint to be < 3 degrees - double cardan joints between 6 and 7 degrees. |
#6
|
|||
|
|||
Jim Warman wrote:
> (good explanation) > ... > While CV joints are, technically, universal joints, we still use the > different terms to differentiate between those that aren't constant velocity > and those that are. As for which term is correct depends on the style of > joint and how it reacts at high angles of deflection. So, as I understand your description, my '94 Explorer 4WD has U-joints in front. Right? -- Gordon S. Hlavenka http://www.crashelectronics.com "If we imagined he could _find_ the car, we could pretend it might be fixed." - Calvin |
#7
|
|||
|
|||
IIRC, your 94 will have twin I beam front suspension.... in that case, it
will have 3 U-joints.... one at each knuckle and one roughly in the centre (in the long drive axle)... "Gordon S. Hlavenka" > wrote in message om... > Jim Warman wrote: > > (good explanation) > > ... > > While CV joints are, technically, universal joints, we still use the > > different terms to differentiate between those that aren't constant velocity > > and those that are. As for which term is correct depends on the style of > > joint and how it reacts at high angles of deflection. > > So, as I understand your description, my '94 Explorer 4WD has U-joints > in front. Right? > > -- > Gordon S. Hlavenka http://www.crashelectronics.com > "If we imagined he could _find_ the car, > we could pretend it might be fixed." - Calvin > |
#8
|
|||
|
|||
I believe the term you are looking for is "constant velocity joint"
Gordon S. Hlavenka wrote: > I've heard them called "front U-joints" and I've heard them called > "Constant Velocity (CV) joints". Which is the proper term? > > I know in FWD vehicles they're called CV joints, but I don't know why; > it seems to me their velocity should change as the vehicle speed > changes. Same for 4WD. > |
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
how did Dilbert learn in front of all the kettles? We can't nibble plates unless Alexis will daily recollect afterwards | [email protected] | Technology | 0 | January 15th 05 01:56 PM |
Can a cop pace you from the front | jaybird | Driving | 22 | January 7th 05 04:52 PM |
Q:Right-Lock lockers | Zenteren | 4x4 | 16 | January 16th 04 08:57 AM |
Hum/Vibration in front of of '95 Explorer | Mr. Knowitall | 4x4 | 0 | December 17th 03 11:28 PM |