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# Yes, indeed!

April 19 2017 at 12:15 PM
Crosman Forum Member

Response to A Modest Proposal: I think the recent discussion of pump link length...

The diminished reduction is so slight.

Approximate figures here:

UNIT A pump arm with 2" pivot distance and a toggle 2.75" long @ 90 degrees open lever will yield 2.75" stroke.

UNIT B pump arm with the same 2" pivot distance and toggle 3.5" long at 90 degrees open lever will yield about 2 5/8" stroke.

Minimal reduction in sweep volume, yes, for the exampled layout (more reduction the longer the link is). However, if we were to use the above examples and fatten the tube enough where their sweep were equivalent, say it is UNIT B we do this with.

Yes, there will be the values that will never disappear, pressure multiplied by surface area of the piston, the longer link and its reduced angle of attack to move the piston does reduce the effort in comparison.

Back to that test sled mentioned earlier. It is, or was, (may assemble it again and do a video) like so:

Lever is 24" long, pivot 4" test load of 500lbs. Link #1 4" long link, #2 8" long link. The test conducted with the lever itself set to 90 degrees.

Using a heavy pull spring scale and a ratchet system to move the lever, Link #2 was greatly easier to move the load exhibiting much less weight on the scale (effort to us).

The test itself was not used to measure build pressure of a tube/vessel, but rather to experiment with what ME was gained by the longer link in any given position moving a fixed amount of weight.

Did not believe a difference would be noted at all, as the assumption has historically been that our levers fall into one of the three classes of levers. They do not, as I, II, and III levers have a fixed MA. Our levers and their toggle arrangement throw another element of MA into the mix.

While studying efficient and easy levers on the physics forum (do believe you are on there Steve?) someone proposed the longer link theorem. After looking deeper, and learning the math to better ease my mind, it was decided to just build a test jig.

I was sold for my particular project, that is near completion now.

 This message has been edited by Duane35 from IP address 208.87.234.201 on Apr 19, 2017 12:26 PM

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