I was reading through a few winch threads lately, and saw much discussion on speed vs heat. Being a curious engineer, I did some digging on Warn's site and found some interesting info to share.
My theory is: with a DC motor, the closer you get to stall, the higher the amperage, the higher the heat, and lower the efficiency. This is due to lack of back EMF and lower speeds. So there must be some sweet spot between max line pull (lowest line speed) and max line speed (lowest line pull).
This study will focus on efficiency - achieving the best pulling power (force and speed) with the lowest amp draw on your electrical system. If you simply want all out pulling power, grab a Warn 16.5 and a snatch block!
1) I found with older winch designs, efficiency drops sharply with increased line pull. Let's look at the 8274:
Look at the specs for 4000 and 8000 lbs, notice anything interesting? The line speed for 8000 is roughly half of 4000, implying similar work being done, but somehow it takes 200 amps more! It's 68% less efficient to pull at 8000 with this winch.
But what if we used a snatch block to achieve an 8000 lbs line pull? So now the winch sees half the load (4000 lbs) and therefore pulls at 16.4 ft/s using 286 amps. Cut the speed in half (due to snatch), and we have an effective 8000 lbs pull, at 8.2 ft/s, and use 200 amps less than doing it with the winch alone - almost like free power!
2) A larger winch pulling at lower line pull, is much more efficient than smaller winch at higher line pull. This is because a large winch uses lower gearing, and therefore spins the DC motor faster (more efficient).
Let's compare a Zeon 12 and 9.5xp, both doing an 8000 lbs pull:
Zeon 12
9.5xp
With the Zeon 12, we pull at 7.8 ft/s using only 321 amps
With the 9.5 XP, we pull at 7.4 ft/s using 413 amps
This is similar to my first example, except think of the gearing advantage of the Zeon 12 as an "internal snatch block".
Even though the Zeon 12 is very advanced, if we push it to its max, its efficiency suffers as well. Let's compare it to the 16.5ti, both at 12000 lbs line pull:
The Zeon 12 pulls at 4.5 ft/s, using 446 amps
The 16.5ti pulls at 4.4 ft/s, using only 393 amps
What's interesting though, is the newer generation winches don't suffer nearly as much from efficiency drop at you approach max line pull, as the older gens. For instance, compare the 9.5 XP above, to the XD 9000:
Like the venerable 8274, when you go from 4000 lbs to 8000 lbs, your amp jumps from 252 to 423, while doing almost the same work (line speed halves while pull doubles). Making the winch 68% less efficient, bang on with the 8274.
With the 9.5 XP, line speed drops from 11.8 to 7.4 ft/s, while amps climb from 248 to 413. If you do the math, it's only 33% less efficient. Wonder why? Perhaps better motor technology?
So what's the conclusion here? Well, for most of us that simply wants to extract ourselves once, it probably doesn't matter much, as long as you have enough line pull. But say if your battery is seriously undersized, or if you are doing lots of continuous pulls to extract others, then you want to use the least amount of power.
In this case, it's often advantageous to use a snatch block if you have an older winch. It's much more efficient to pull at 4000 lbs, using a snatch block, than strain your winch at 8000 lbs. Your pulling speed is nearly identical (not losing any time), but you amps are 68% lower.
If you have the newer generation winches, then the snatch block doesn't gain as much efficiency (only 33%). However, it's better to get a bigger winch, run it at lower line pull, to take advantage of the lower internal gear ratio (and spin the DC motor faster, with more back EMF).
Feel free to add to, and / or correct anything if you see any mistakes in my calculations. Hope that was useful to people trying to pick a winch, and like geeky calculations!
My theory is: with a DC motor, the closer you get to stall, the higher the amperage, the higher the heat, and lower the efficiency. This is due to lack of back EMF and lower speeds. So there must be some sweet spot between max line pull (lowest line speed) and max line speed (lowest line pull).
This study will focus on efficiency - achieving the best pulling power (force and speed) with the lowest amp draw on your electrical system. If you simply want all out pulling power, grab a Warn 16.5 and a snatch block!
1) I found with older winch designs, efficiency drops sharply with increased line pull. Let's look at the 8274:
Look at the specs for 4000 and 8000 lbs, notice anything interesting? The line speed for 8000 is roughly half of 4000, implying similar work being done, but somehow it takes 200 amps more! It's 68% less efficient to pull at 8000 with this winch.
But what if we used a snatch block to achieve an 8000 lbs line pull? So now the winch sees half the load (4000 lbs) and therefore pulls at 16.4 ft/s using 286 amps. Cut the speed in half (due to snatch), and we have an effective 8000 lbs pull, at 8.2 ft/s, and use 200 amps less than doing it with the winch alone - almost like free power!
2) A larger winch pulling at lower line pull, is much more efficient than smaller winch at higher line pull. This is because a large winch uses lower gearing, and therefore spins the DC motor faster (more efficient).
Let's compare a Zeon 12 and 9.5xp, both doing an 8000 lbs pull:
Zeon 12
9.5xp
With the Zeon 12, we pull at 7.8 ft/s using only 321 amps
With the 9.5 XP, we pull at 7.4 ft/s using 413 amps
This is similar to my first example, except think of the gearing advantage of the Zeon 12 as an "internal snatch block".
Even though the Zeon 12 is very advanced, if we push it to its max, its efficiency suffers as well. Let's compare it to the 16.5ti, both at 12000 lbs line pull:
The Zeon 12 pulls at 4.5 ft/s, using 446 amps
The 16.5ti pulls at 4.4 ft/s, using only 393 amps
What's interesting though, is the newer generation winches don't suffer nearly as much from efficiency drop at you approach max line pull, as the older gens. For instance, compare the 9.5 XP above, to the XD 9000:
Like the venerable 8274, when you go from 4000 lbs to 8000 lbs, your amp jumps from 252 to 423, while doing almost the same work (line speed halves while pull doubles). Making the winch 68% less efficient, bang on with the 8274.
With the 9.5 XP, line speed drops from 11.8 to 7.4 ft/s, while amps climb from 248 to 413. If you do the math, it's only 33% less efficient. Wonder why? Perhaps better motor technology?
So what's the conclusion here? Well, for most of us that simply wants to extract ourselves once, it probably doesn't matter much, as long as you have enough line pull. But say if your battery is seriously undersized, or if you are doing lots of continuous pulls to extract others, then you want to use the least amount of power.
In this case, it's often advantageous to use a snatch block if you have an older winch. It's much more efficient to pull at 4000 lbs, using a snatch block, than strain your winch at 8000 lbs. Your pulling speed is nearly identical (not losing any time), but you amps are 68% lower.
If you have the newer generation winches, then the snatch block doesn't gain as much efficiency (only 33%). However, it's better to get a bigger winch, run it at lower line pull, to take advantage of the lower internal gear ratio (and spin the DC motor faster, with more back EMF).
Feel free to add to, and / or correct anything if you see any mistakes in my calculations. Hope that was useful to people trying to pick a winch, and like geeky calculations!
