7 replies to this topic

[heavetahoe]

can anyone give me the formula to find the torque value of brakes on a fixgrip chairlift? i believe there is a formula.....

[cjb]

Mb1= (D*u/i)*((20*Vr*n/sl)-s)


Mb1= Braking moment (torque),ft-lb
D= Bullwheel diameter
u= coeffecient of braking force
i= gearbox reduction ratio
sl= slope length
Vr= Vertical rise, ft
n= number of passengers, uphill side
s= number of sheaves, uphill side

This is from the Yan product manual.
I would however suggest you contact someone associated with your lift company or an independent engineer.

[Kicking Horse]

Greetings,

I have a question,

Why do you need to know the number of Sheaves on the uphill side?

[heavetahoe]

we found some of the information needed in our riblet book it is a riblet chair by the way... i asked more so senior mechanic and the number of sheaves has to do with the friction created by the sheaves. each sheave has a friction value. dont ask me what that is or how to find that out?

[liftmech]

Sheave friction is calculated using a constant. It has to do with bearing friction and force required to turn the sheave from a motionless state. I have it written down somewhere but 0.03 % sounds familiar.

[Kicking Horse]

Ok, Why is the downhill / light side not part of it?

[Kelly]

A key reason for only using the heavy side in counting the sheave turning coefficient is that it (a fixed coefficient factor) is only valid for a "nonchanging load" on a sheave.
You can add the “lightside” factor to reduce the final figure but I am willing to guess the smaller coefficient for the lighter load (sometimes 0) plus the smaller number of sheaves on the downline in the final amount would not be convincing enough to use.
Another version –
(Rise x PPH) / 3500 = ft lbs
My experience is that the formula gets you into the “ballpark range” – actual testing torques are usually quite higher before any slippage occurs…and when things begin to slip it’s a very subtle movement, not the ziiiing ka-pow you might be thinking of.
If it slips before the amount is reached either the formula math was done incorrectly or the shoes are contaminated with paint, oil or ice.
You do the test – rig, attach, turn, observe then record and go to the next check…for the most part these are nonevents hardly worth mentioning…but still important.

…one of the first documentation of friction and its coefficients (reduction factors) is Leonardo di Vinci, see image below.
 Friction da vinci studies.jpg (145.6K)
Number of downloads: 25

[Kicking Horse]

Thanks Kelly for taking the time to explain.