Coefficient of Friction between Lifting Trunnion and Wire Rope
Coefficient of Friction between Lifting Trunnion and Wire Rope
(OP)
In the Moss book, torsional moment was not included in the design of a Type 3 trunnion (no lug). I think torsional moment due to friction should not be neglected.
For those who design lifting trunnions, what coefficient of friction do you normally use in calculations?
I don't design lifting trunnions. I just like to have a "feel" on how big the trunnions and repads would be for a tower I'm currently working on.
For those who design lifting trunnions, what coefficient of friction do you normally use in calculations?
I don't design lifting trunnions. I just like to have a "feel" on how big the trunnions and repads would be for a tower I'm currently working on.





RE: Coefficient of Friction between Lifting Trunnion and Wire Rope
Let us know what you come up with.
RE: Coefficient of Friction between Lifting Trunnion and Wire Rope
I guess the torsional load is insignificant compared to the bending loads. I may still need to determine the torsional load to check the weld sizes. I'll try a CoF of 0.15.
The tower is 85 m [279 ft] high x 5.5 m [18 ft] diameter, with an erection weight of 650 tonnes [1,433 kips]. Trunnions would be attached to a 19 mm [3/4"] thk shell. Distance of trunnions from COG is 27 m [89 ft]. COG is 42 m [138 ft] from base.
I have not ran the numbers yet, but I have a hunch the local stresses on the shell will determine the size of the trunnion.
RE: Coefficient of Friction between Lifting Trunnion and Wire Rope
RE: Coefficient of Friction between Lifting Trunnion and Wire Rope
I guesstimate the trunnions to be around 900mm diameter with stiffening rings at the top and bottom.
RE: Coefficient of Friction between Lifting Trunnion and Wire Rope
RE: Coefficient of Friction between Lifting Trunnion and Wire Rope
Yes, I did study the trunnions in the video and for sure there were torsional loads on them. On the tower I'm working on, I assumed a CoF of 0.15 and used an impact factor of 1.35. The effect of the torsional moment on local stress was negligible. (bernoullies123, you're right. They are negligible.).
chicopee, by bottom attachment, do you mean the tailing lug? Anything special I need to know about them?
The tower i'm working on is very similar to the one in the video below, except below the trunnions, the tower will be "dressed" as much as possible.
http://www.heavyliftspecialist.com/cranes/transpor...
RE: Coefficient of Friction between Lifting Trunnion and Wire Rope
Just wondered where you came up with a COF for steel to steel of 0.15? That's nealy the limit value for PTFE to Stainless Steel(polished). Steel to Steel is significantly greater then PTFE to SS otherwise why use low friction bearings (PTFE/SS)?
RE: Coefficient of Friction between Lifting Trunnion and Wire Rope
0.15 is for lubricated steel to steel. That's just my assumed value for the CoF between wire rope to steel. Some references say it is lower than that, say 0.08.
RE: Coefficient of Friction between Lifting Trunnion and Wire Rope
RE: Coefficient of Friction between Lifting Trunnion and Wire Rope