How much force is actually exerted on the wrist during a sledge lever?

[MikeF.]

Hey all! 

Curiosity has hit me hard regarding this factor of sledge levering. I haven’t found anything at all on the subject, and I’m wondering if anyone here has any idea how this is measured, or is aware of any other research into the subject.

When levering sledgehammers, while holding the end of a standard 36” handle, how much force is actually needed to control the hammer in the lowering phase and contracting phase back to starting position? The Krahling Method is used to measure the force needed to bend a short bar to 30 degrees, and I’m curious how force is measured with sledge levering as well. I’m also wondering how much it changes when levering 10, 12, 16 etc pound hammers. 

Thank you all! 

[matek]

On 4/23/2023 at 4:33 AM, MikeF. said:

Hey all! 

Curiosity has hit me hard regarding this factor of sledge levering. I haven’t found anything at all on the subject, and I’m wondering if anyone here has any idea how this is measured, or is aware of any other research into the subject.

When levering sledgehammers, while holding the end of a standard 36” handle, how much force is actually needed to control the hammer in the lowering phase and contracting phase back to starting position? The Krahling Method is used to measure the force needed to bend a short bar to 30 degrees, and I’m curious how force is measured with sledge levering as well. I’m also wondering how much it changes when levering 10, 12, 16 etc pound hammers. 

Thank you all! 

I don't think measuring is necessary in the case of sledgehammers, because the head's chemical composition is essentially irrelevant. Unlike with steelbending, there are no "batches" (I mean, it doesn't matter) and the manufacturer is also not important. The weight and the grip distance on the handle should be enough to measure progress or establish order between people. But one can model the twisting force to have just one number to assess "how much force is exerted on the wrist" as you described. 

I will assume you're talking about levering when first, the arm is held straight and the sledge is lowered only by bending the wrist. Then the wrist is straightened lifting the sledge back up. This is a little bit complicated scenario, so there are some assumptions for the model below. For example, the assumption that the handle is always perpendicular to the grip (so all the movement is done by the wrist), the elbow is straight (no 'cheating'), the arm is perpendicular to the body, etc.

*check the attached pic here, then continue reading*

Let's assume that the distance between the wrist and the grip is 3.15" or 0.08m, but this will be individual. Let's say you're leveling at 20" (0.51m) a 10lbs (4.54kg) sledgehammer. The torque on your wrist at 40 handle degrees (1.57rad) will be 15.11Nm. Same sledgehammer, same angle but holding it at 36" (0.91m) will result in 28.76Nm. Same sledgehammer, same distance of 36" but only 60 degrees would be 17.18Nm. Same distance of 36", same degree of 60, but with a 15lbs (6.8kg) sledgehammer would be 25.73Nm. You get the idea.   
It is important to note that 0Nm is not at the starting position of 90 degrees because that's not when the sledgehead's center of mass is directly above your wrist. There is 'load' there, but a different kind of load. Therefore, after passing the wrist (to the other direction, including 90 degrees), this model will give negative values, but this is not important here. Btw ignoring the distance between the grip and wrist (c=0), the model would be much simpler, but less accurate. 

 

Edited April 26, 2023 by matek

[matek]

Additional note because somebody asked me. Direction is the key, and that's why we can have negative values to the "other side of the wrist"; torque is a vector quantity. 

[Blacksmith513]

38 minutes ago, matek said:

Additional note because somebody asked me. Direction is the key, and that's why we can have negative values to the "other side of the wrist"; torque is a vector quantity. 

I’ve got nothing to add other than you are a Hungarian living in Japan with way better English than me.

[matek]

1 hour ago, Blacksmith513 said:

I’ve got nothing to add other than you are a Hungarian living in Japan with way better English than me.

Just written English. I still have a very nice Central/Eastern European accent when speaking 

Btw I still don't know why I calculated this, probably too many beers. Literally nobody cares. 

[Blacksmith513]

1 hour ago, matek said:

Just written English. I still have a very nice Central/Eastern European accent when speaking 

Btw I still don't know why I calculated this, probably too many beers. Literally nobody cares. 

I care!

[steeve tremblay]

according to my calculation if the handle is 36 inch with a weight of 12 lb you multiply the line of the hands where you hold the weight if it is 15 then =180 lb of leverage force at 240 if I am wrong then say it Me

[Tom Flesher]

On 5/5/2023 at 11:59 AM, matek said:

… probably too many beers. Literally nobody cares. 

The only dangerous amount is none.