physics (lever) question

[fishhead]

I'm going to build one of those scissor action body grip trap setters.

I'm wondering if having the pivot point 1/3 distance from the end doubles the squeezing power applied with that end.

In other words the pivot point would be at 10" from the end leaving 20" on the other side of the pivot. Does that double the force applied with the squeezing end since your hand is squeezing a point at twice the distance?

If that is true would having a 10" 'work' end generate three times the force if the other end was 30" and so on?

[Cabin Fever]

The mechanical advantage is more related to the distance traveled by one end of the "scissors" compared to the other end. Here's an example, if for every 1" the 20-inch end closes the 10-inch end closes say 1/3", the mechancial advatage is 3:1. I'm not sure if that is clear. Does it make sense to you?

[fishhead]

Yes. I was just looking at comparing handle lengths to the other side of the fulcrum. That calculator let me do some comparisons and it's as I expected.

[Cabin Fever]

I thought more about this last night in bed and the advantage is 3:1 for your set-up....the same as you had original theorized.

Here is what i came up with. If the trap setter was set so the two arms were 90º from each other, you would have two 45-45-90 degree triangles on both sides of the pivot point. The working side would be a triangle with two 10" legs, and the handle end would be a triangle with two 30" legs.

So, what you would have to calculate is the distance that both sides move when applying force. That distance is the hypotenus of the triangles. One would use this "rule" to find the hypotenuse of 45-45-90 triangles.



The hypotenuse of the setting side with the 10" legs is 10 x (sq. root of 2) = 14.14"

The hypotenuse of the handle side with the 30" legs is 30 x (sq. root of 2) = 42.42"

The mechanical advantage is 42.42/14.14 = 3

After going thru all those girations, I realized the ratio between the length of the arms on either side of the pivot point is also 3

[Ed Norman]

Mine seem a few inches too short on the long end, and a little short on the short end. They have to open really wide and I always feel the excitement of possibly losing some teeth while squeezing them. I could measure them to let you know the bare minimum for a 330 size. The trouble is, if you make them a comfortable length to use, they are getting too long to pack around.

[fishhead]

Originally Posted by Cabin Fever

I thought more about this last night in bed and the advantage is 3:1 for your set-up....the same as you had original theorized.

Here is what i came up with. If the trap setter was set so the two arms were 90º from each other, you would have two 45-45-90 degree triangles on both sides of the pivot point. The working side would be a triangle with two 10" legs, and the handle end would be a triangle with two 30" legs.

So, what you would have to calculate is the distance that both sides move when applying force. That distance is the hypotenus of the triangles. One would use this "rule" to find the hypotenuse of 45-45-90 triangles.



The hypotenuse of the setting side with the 10" legs is 10 x (sq. root of 2) = 14.14"

The hypotenuse of the handle side with the 30" legs is 30 x (sq. root of 2) = 42.42"

The mechanical advantage is 42.42/14.14 = 3

After going thru all those gyrations, I realized the ratio between the length of the arms on either side of the pivot point is also 3

Yes. KISS works the best for me. The length ratio between the 2 ends is the mechanical advantage. Now I have to figure out where to put the fulcrum.

Yes Ed. If you get a chance get a measurement on them. I'm going to make it to comfortably fit the 220 and barely usable on the 330's. I plan on carrying them during latter grouse season as insurance against those blasted bucket sets that some trappers are putting out in our woods. I'm also going to try to teach my new dog to stay the heck away from them.

[Ed Norman]

I haven't used them on 220s, I just hand squeeze those.

They are 22" with a 7.5" pivot. Material is 1"X3/16".

You know how to set them with rope, right? Stick it in the top loop, then thru the bottom loop. Drop the rope coming out the top and step on it, or better yet, tie a loop for your foot. Grab the rope coming out the bottom loop and pull up, the spring will collapse.

[fishhead]

Thanks. For some reason I have a lot more trouble setting a 220 than a 330. It might be because I use my body muscles more on the bigger ones.

Yes I've set them with a rope but my focus is on having a pair for an emergency this fall should I not be able to teach my new dog to avoid buckets. I don't see many but I found one that was set within 10' of a trail I hunt. Even a dog on a leash would probably have reached it and my dog will range at least 50' or more even if I get her well trained.

[Ed Norman]

I'll try it on a 220 today, and I'm sure it will work fine.

[foxtrapper]

To your original question, yes. The leverage advantage is the ratio of the arm lengths. 10" on one side, 30" on the other, yields a 30/10 ratio.