My next project.

[12bolts]

Phil, I think there is an error in your calculations there. .......

Terry,
I didnt check a printed reference book for that, but from http://en.wikipedia.org/wiki/Horsepower "quote" The mechanical horsepower, also known as imperial horsepower, of exactly 550 foot-pounds per second is approximately equivalent to 745.7 watts.
And from http://www.kylesconverter.com/power/horsepower-to-foot--pounds--force-per-second Enter your value of 2HP and in the solve box is the result 1100 ft lbs force/sec

cheers Phil

 

[David S]

For sure we are mixing terms here. Phil is talking power and quotes foot-lbs/ sec. That is not torque that we are used to i.e. lb-ft. Power is torque X rpm...so you can have hi rpm and small torque or low rpm and hi torque to get the same power.

 

[12bolts]

I think we have to work backwards. The winch is rated at 2200 lb, so as long as the load doesn't exceed that rating then it really doesn't matter what the ultimate torque the engine and gear reduction can deliver. Sure it may be capable of delivering more if you hook 4000 lb on to the winch, but then that is sort of like attaching a long bar to the winch handle and overloading the winch manually. The estimate of 60 rpm at the winch handle is probably not too bad. Now just come up with the 175:1 reduction and clutch.

David, you are assuming that the motor can deliver a nice smooth variable increase in torque. A 2 stroke motor has very little low down power. You need high revs to get anything out of them, and once the power curve comes on it rises dramatically. A heavy load might require substantial RPM just to get it moving. By the time that happens due to inertia you might have easily exceeded the SWL of the winch/cable. A prime consideration here is that it does matter what the ultimate torque delivered could be.
Attaching a long bar to the handle just makes it easier to turn regardless of the load. If you hook 4000 lbs on, its overloaded, whether you crank it by hand, extended lever or mechanical means
The reason we needed a 175:1 gearbox is because of the max RPM. If you want to work backwards then you need to know what torque is required to get your 2200 lbs out. From there you need to know at what RPM your power source will deliver the required torque, and then a gearbox to suit those RPM's.
But this still all ignores the fact that this winch is designed for human horsepower. The application of which is gradual and easily controlled, and can sense by feedback whether we are straining/struggling perhaps getting close to design limits. As I said in my first post, this is an accident waiting to happen....

Cheers Phil

 

[DAN_IN_MN]

David, you are assuming that the motor can deliver a nice smooth variable increase in torque. A 2 stroke motor has very little low down power. You need high revs to get anything out of them, and once the power curve comes on it rises dramatically. A heavy load might require substantial RPM just to get it moving. By the time that happens due to inertia you might have easily exceeded the SWL of the winch/cable. A prime consideration here is that it does matter what the ultimate torque delivered could be.
Attaching a long bar to the handle just makes it easier to turn regardless of the load. If you hook 4000 lbs on, its overloaded, whether you crank it by hand, extended lever or mechanical means
The reason we needed a 175:1 gearbox is because of the max RPM. If you want to work backwards then you need to know what torque is required to get your 2200 lbs out. From there you need to know at what RPM your power source will deliver the required torque, and then a gearbox to suit those RPM's.
But this still all ignores the fact that this winch is designed for human horsepower. The application of which is gradual and easily controlled, and can sense by feedback whether we are straining/struggling perhaps getting close to design limits. As I said in my first post, this is an accident waiting to happen....

Cheers Phil

Phil

Did you watch the video in my first post?

This isn't my first time around the block. I will cautiously test/try things and then modify to make it work. Many people will not try the things I do.

 

[David S]

Phil I think we are on the same page actually. I know you have to keep the rpms up on the small gas motor. And do agree with your gear ratio suggestion. The point that I was trying to make.. unsuccessfully.. was that one must work within the SWL of the winch. In the video it could be that the "clutch" provided enough slip to get the load moving.

 

[Terrywerm]

Terry,
I didnt check a printed reference book for that, but from http://en.wikipedia.org/wiki/Horsepower "quote" The mechanical horsepower, also known as imperial horsepower, of exactly 550 foot-pounds per second is approximately equivalent to 745.7 watts.
And from http://www.kylesconverter.com/power/horsepower-to-foot--pounds--force-per-second Enter your value of 2HP and in the solve box is the result 1100 ft lbs force/sec

cheers Phil

I was thinking about this all day today, and it was bugging me, you know how some things just sort of nag at you in the back of your mind?? Well, I thought it through, went through the math: 1 HP = 33000 pounds lifted one foot in one minute. 33000 divided by 60 seconds = 550. So, one HP = 550 ft/lb per second, as you came up with. Your math was correct. (I won't tell that you cheated and used a converter) :donttell: Anyway, I realized that something was amiss, however and finally figured it out. We were calculating direct force in ft/lbs, and rotary force or torque is measured in ft/lbs also, but the two measurements do not carry directly over from linear force to rotary force or vice versa if I remember correctly, thus the confusion.

 

[jererp]

If you could get a power curve for your chainsaw engine, you would see that it develops a max torque at a certain RPM. That max torque number is what gets multiplied when you go through your gear reduction.

I would concentrate on designing for RPM, and let the torque be what it may be. As long as you don't hook it to an object that grossly overloads your original winch design load, you should be OK. If you are worried about overloading, you could always add a shear pin for safety.

 

[NEL957]

Some one set up "the-little-winch-that-could" out of a lot of work and time. The only thing I would not want to be that close to that cable if it decided to turn loose. I have seen cables like that one almost cut a person in half. There is nothing like a cable under too much of load. If you were to build one the biggest thing I could recommend is to have some distance between you and that mochine. Just be carefull.
Nelson Collar

 

[melsdad]

Reductions are easy. Here are some examples.

Drive gear has 12 teeth, driven gear has 48 teeth. 48 divided by 12 is 4, meaning that the reduction is 4:1 The driven gear will turn 1/4 the speed of the drive gear.

Another way to arrive at the same conclusion: 12 teeth divided by 48 teeth equals .25 meaning that the driven gear will turn at 1/4 the speed of the drive gear.


Now, if you have multiple reduction ratios, let's say the first reduction is 4:1, the second reduction is 3:1, and there is a third reduction of 2.5:1 you can calculate the total reduction by multiplying all of the ratios as follows:
4 x 3 x 2.5 = 30 meaning the overall reduction is 30:1. The final drive speed of the spool would be 1/30 the speed of the input to the first reduction. If the engine speed was 6000 RPM, and the overall reduction was 30:1, then the spool speed would be 200 RPM.

Inversely, if the engine puts out a torque of 100 in/lbs, the torque after reduction would be 30 times greater, or 3000 in/lbs which equals 250 ft/lbs

Awesome information!!!! Thanks Applied!