What is the power/torque lost through a u-joint?
What is the power/torque lost through a u-joint?
(OP)
Gentlemen:
I have been through 20+ of my engineering books and a web search and I cannot find anything regarding torque or
power loss through a u-joint. Also, I am trying to
calculate the radial load for a bearing adjacent to
the u-joint. Can anyone direct me to a source of info
or provide info as well as the basis?
Thanks...
I have been through 20+ of my engineering books and a web search and I cannot find anything regarding torque or
power loss through a u-joint. Also, I am trying to
calculate the radial load for a bearing adjacent to
the u-joint. Can anyone direct me to a source of info
or provide info as well as the basis?
Thanks...
The more you know, the more you
know you don't know....





RE: What is the power/torque lost through a u-joint?
B) Free body diagram.
Cheers
Greg Locock
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.
RE: What is the power/torque lost through a u-joint?
Per Greg: Free body diagram.
Straight shafts would be very close to zero.
Severe angle would have significant loss while stressing the joint.
Bearing load would have similar answer.
RE: What is the power/torque lost through a u-joint?
If I remember correctly, if you have a single U-joint connecting two shafts at an angle, then the angular velocities of one or both vary as they go through a revolution. That could throw in more force than friction, as well as vibration.
RE: What is the power/torque lost through a u-joint?
TygerDawg
RE: What is the power/torque lost through a u-joint?
RE: What is the power/torque lost through a u-joint?
RE: What is the power/torque lost through a u-joint?
A minimum of 1/2 degree is recommended by most for lubrication and sealing.
I'm not so sure about manufacturers supplying power consumption information. They have not exactly been in competition to lower the values, and they very likely don't want to be.
As mentioned, it's affected by angle, bearing friction, speed, drive arrangement, etc.
RE: What is the power/torque lost through a u-joint?
The power loss can be as high as 30%-50% depending on the cofiguration.
I believe the minimum offset per joint is 5-15 degrees.
Have a look at a drawing of a rear driveline of any auto and you should find the bearing and seal info.
Good luck on the calculations, I think its just the matter of building it and testing.
Cheers
RE: What is the power/torque lost through a u-joint?
Recommended offset for a UJ is 4 degrees
Old 4wds like say Landrovers or Jeeps had no speed restriction
The power does not lag
The unbalanced mass of the UJ is not responsible for high rotational speeds.
Other than that, yes, great post.
Cheers
Greg Locock
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.
RE: What is the power/torque lost through a u-joint?
RE: What is the power/torque lost through a u-joint?
The number was probably on the high side, too.
rmw
RE: What is the power/torque lost through a u-joint?
Thank you all for your valuable input. For those still
interested I found a source who has an empirically
based formula.
To= Torque Out
Ti= Torque in
a= Operating angle of U-Joint
To= Ti*cos^2 a
Also suggested for reference was an SAE publication
" U-Joint and Driveshaft Design Manual".
Thanks again to all...
Terry
The more you know, the more you
know you don't know....
RE: What is the power/torque lost through a u-joint?
Cheers
Greg Locock
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.
RE: What is the power/torque lost through a u-joint?
I had on old International Travelall 4x4 locking hubs and on the dash a warning sign was posted, "Do not to exceed 30 mph (50kph) in 4 wheel drive". I did it once and almost shook my poor, dead and buried, grandfathers teeth out.
The mass vibration problem comes into play when the rpm exceeds >1500 rpm. Wheels of autos and drivelines rarely exceed this, as 1000 rpm is ~ 132kph. The phase orientation is important (2uj) to cancel the lead and lag of the individual joints. Dynamic balancing is done on drive shafts prior to installation in two planes.
Have you ever tryed to turn the chute on a snow blower and find it sticks on part of the revolution, this is part of the lead/lag problem.
Based on Strider17's equation 10 degree tir would only amount to a 3% loss, however if begin approach 45 degrees you get a 50% loss and 90 degree is a 100% loss. This can be proved using a uj on a ratchet assembly.
Theres an idea, torque a bolt to say 50lbf straight up, then apply a certain angle to a uj c/w torque wrench and see how many lbf it takes to rotate the bolt further. Might help to prove the formula.
Bearings and seals take a kicking, if you try to over build the thing, bigger in this case is not better.
Beer time
Cheers