Thread: Winch on a winch!

Originally Posted by muddymech

my theory on winch to winch is that the winch on the vehicle not moving will have the added force of the winch being pulled in on the moveing vehicle.
so if winch on stopped cvehicle pulls a 2500kg car then it has a 2500kg force on it, excludeing friction, now if the car being pulled attaches its winch onto the the other cable and pulls in at 1000kg force then the car that is stopped would now have a 3500kg force on the winch.

some one must know a college proffesor who can work this out woith some clever maths.

No clever maths needed. When you attach the cable of the stopped vehicle (vehicle A) to the winch cable of the car which needs a 2500kg pull to move (vehicle B ), what stops the cable from just spooling off Vehicle B's winch drum? Nothing, unless you somehow lock Vehicle B's drum. The lock would have to withstand a force of 2500kg if it is to resist the pull of Vehicle A's winch.
If you remove the lock, and engage Vehicle B's winch, it will have to pull back the other way with a force of 2500kg to resist the cable winding off it's drum. If it can only pull with 1000kg force and this isn't enough to move the vehicle, then it will be forced backwards by the pull of the other winch (and probably burn out). In this situation the tension in the cable will only reach whatever force winch B can apply to it while being turned backwards.
You can't escape the fact that the tension in the cable is the same IN BOTH DIRECTIONS.

Coop

i decided to go to the experts so e mailed warn see if they had an answer, surprisingly they replied quickly:

Good day Ian,

Thank you for visiting the WARN web page.

There are a couple different things that are occurring here that need to be taken into consideration when pulling loads with a winch. Take a look at the diagram below, a winch pulls rated load when spooling the first layer of wire rope onto the drum. So when you pull more wire rope off the drum, the winches load pulling capacity will be higher.

Now look at the lower chart that shows the line speed and motor current draw, and on the far right the pulling capacity by layer to better understand the first diagram.

Lets say the load being pulled is 3000 lb and you will be pulling off the 2rd layer in your single line pull scenario to start the pull. When making a single line pull, the winch will have more wire rope off the drum, so the winch will have a higher pull rating, so it will be drawing fewer amps and have a higher line speed.

When hooking the two winches together, each winch will see the same 3000 lb load, but they will be pulling off the 3th layer, and then the 4th layer more quickly, so the winch will have a lower pull rating, this will cause it to be pulling a higher load, drawing more amps and have a slowing line speed. The two winches should still be faster than the one, but not by much I don’t think.

Having the two winch hooks connected together and winch both winches in at once would not double the pulling capacity like using a snatch block, there is no mechanical advantage in this scenario.

The dynamics of a DC Series wound motor is they like to run at high RPM’s, they will run longer and cooler if the RPM’s can remain higher. Years ago an engineer told me that in almost every scenario our winch motor would run longer and pull more weight if the load was double lined compared to single lined when pulling the same weight. I would like to see an XD9000 pull a load single line. The two XD9000’s pull the same load hook to hook like you guys were suggesting, and then pull the same load double lining with a snatch block and record the results just to see what the outcome would be because I’m not exactly sure what they would be…

I’m going to ask one of our engineers your question also and see what he comes up with as well, but it may take a couple days to get a response back. I’ll pass on what I hear from him too.


================================================== ================================================== ================================================== ==
XD9000 12 Volt Winch Specifications

12V DC PERFORMANCE SPECS

Line Pull
Lbs.(Kgs.)

Line Speed
FT./min(M/min.)

Motor
Current

Pull by layer
layer/Lbs(Kgs.)

0

38(11.6)

70 amps

1/9000(4082)

2000(910)

14.4(4.39)

180 amps

2/8190(3715)

4000(1810)

11(3.35)

255 amps

3/7500(3402)

6000(2720)

8.67(2.64)

330 amps

4/7010(3180)

8000(3630)

6.88(2.10)

415 amps

9000(4080)

6.38(1.94)

460 amps

================================================== ================================================== ================================================== ===

Best regards,



Steve Schoenfelder
WARN Industries