Skidding winch

[4570Man]

I thought pto winches had different lb rating then electric winches, meaning on pto if winch it is rated 6000 lbs it would be the same on first wrap to the last wrap so all power rating is up to the tractor and cable.

As the drum diameter increases the gear ratio decreases and the pull decreases.

 

[goeduck]

As the drum diameter increases the gear ratio decreases and the pull decreases.

Right. Each full turn of the drum retrieves more feet of cable as the drum fills, decreasing the effective pull force. Like a variable gear ratio.

 

[guitarman]

Yep simple mechanics

 

[guitarman]

Power and gear ratio
Yes pto winches are rated differently but whether it's a drum or spool as the cable wraps on the actual diameter increases which changes the ratio which calls for more power if the driving power is static the pulling power decreases, with a pro you have the option to use more throttle to compensate. On winches made for skidding from what I have found they are rated as per a full spool

 

[Oldpath05]

As the drum diameter increases the gear ratio decreases and the pull decreases.

Oh that makes since even I can understand that, short and simple for people who suffer with ADD..............:thumbsup::teacher:

 

[Oldpath05]

Power and gear ratio
Yes pto winches are rated differently but whether it's a drum or spool as the cable wraps on the actual diameter increases which changes the ratio which calls for more power if the driving power is static the pulling power decreases, with a pro you have the option to use more throttle to compensate. On winches made for skidding from what I have found they are rated as per a full spool

Another good explanation, I'm most likely the only one here that didn't get the wrap equation on pto winches. So would you say that with a 6k electric winch as wraps increase the power cant be increased so therefore you loose pulling power? But on a 6k pto winch as the wraps increase to maintain pulling power at 6k, increasing the tractor's rpm will maintain 6k pulling power or until cable breaks?

 

[guitarman]

To john_mc I was posting on my phone and for some reason it wouldn't let delete the extra post

 

[guitarman]

Here is a link that goes into depth explaining it all

EMCE | Every Winch a Winner

Physics

Power

As*stated power is expressed in kW (kilowatt). In physics Watt can also*be expressed in J/s (Joules/second). Joules can also be expressed in Nm (Newton metre), therefore Power can be expressed in Nm/sec.

This makes power more understandable, since we know the required*Nm (line pull x effective drum radius) to move the load and the required speed at which the load has to be moved. The higher the speed (at a given load), the more power we need.

The calculations behind this look as follows: P(kW) = F(N) x V(metres/min) / 1020 x 60** In which P = power in kW, F = Force (line pull) in Newton, V = Line speed in metres/min, 1020 is a constant and 60 is a translation from minutes into seconds (Nm/sec).

Torque

With the required amount of power (kW) determined, the amount of torque (Nm) involved in the application must be determined. Depending on the effective drum radius and the load the torque at gearbox and motor level can be calculated. The amount of torque at gearbox level is important to make sure a sufficiently strong gearbox is chosen, and at motor level to make sure the load can be actually moved.

The effective drum radius used in this calculation is the distance between the*centreline of the active rope layer and the centreline of the drum. For winches with only one layer of rope this is a constant factor. For winches with multiple layers the distance is a variable, and depends on the amount of rope wound on the drum. Please*see Fig. 3-2 for the influence of the number of rope layers on the effective drum diameter.

[https://emce]

a) Drum radius proper -*b) Effective drum radius with one layer of rope - c) Effective drum radius with four layers of rope.

Note:*The rope diameter (required for the above calculation) follows from the nominal winch load, the required safety factor and the type of rope selected.

 

[CobyRupert]

So.....let’s say tractor has a constant (fixed) rpm input to winch.
This makes a constant reel rpm, and would be a constant cable speed, but as the effective reel diameter increases the cable speed increases.
This means more power is required from tractor.

While more tractor power is required, it’s still at same PTO speed, this mean the torque that is passing through winch’s clutch is increasing. Clutch limits the Torque passed to drum.
Clutch also limits the power TO the drum, when tractor’s PTO is operating at a fixed speed.
Power OUT of the drum (cable) is also fixed. (Because power in =power out, ignoring losses ) Thus, if the cable pulling Power stays constant, the torque (pulling Force) decreases as the pulling speed increases (as effect reel size increases).
That makes sense and as expected.
And confirms that the pulling rating (in lbs) is dependent on if it’s first cable turn on reel or last.
And has little to do with the rpm your running winch at.

 

[Sawyer Rob]

Another good explanation, I'm most likely the only one here that didn't get the wrap equation on pto winches. So would you say that with a 6k electric winch as wraps increase the power cant be increased so therefore you loose pulling power? But on a 6k pto winch as the wraps increase to maintain pulling power at 6k, increasing the tractor's rpm will maintain 6k pulling power or until cable breaks?

You don't have to increase the tractors RPM, the tractors governor kicks in and "maintains" the RPM you have set.

The added fuel from the governor, increases the torque that the engine puts out, to compensate for the added load.

SR