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All Springer/NP/PCP Air Gun Discussion General > "Bob and Lloyds Workshop"

A New Method for Increasing the Efficiency of a PCP - the SSG

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rsterne:
Here is a comparison of the cocking effort of three springs.... a 10 lb/in. with negative preload, an 8 lb/in that just touches the hammer, and a 6 lb/in which is preloaded to just 2 lbs and fitted to a guide that clears the hammer by 0.1".... In all cases the hammer stroke is 1", and the average hammer force is the same....



Two things to note.... First, the maximum cocking force is less with the preloaded, weaker spring.... Second, if the hammer rebounds from the valve with a force of 1 lb., it won't compress the 6 lb/in preloaded spring.... but it can compress and store energy in the other two.... I hope this explains the difference....

Bob

rsterne:
Scott, yes, a change in preload will change the depth of the end of the guide inside the hammer.... so you will need to adjust the large bolt to reset that.... In practice, you will find that once you get the preload you need, you could cut the end of the guide off flush with the nuts and forget adjusting it.... The main adjuster will then give you all you need.... As you back if off, increasing the distance of the end of the guide from the inside of the hammer, you reduce the distance the spring is compressed, and lose power in a hurry.... A fine thread on that bolt would be a very good idea....

Bob

Motorhead:

--- Quote from: rsterne on December 31, 2015, 03:01:10 AM ---Scott, yes, a change in preload will change the depth of the end of the guide inside the hammer.... so you will need to adjust the large bolt to reset that.... In practice, you will find that once you get the preload you need, you could cut the end of the guide off flush with the nuts and forget adjusting it.... The main adjuster will then give you all you need.... As you back if off, increasing the distance of the end of the guide from the inside of the hammer, you reduce the distance the spring is compressed, and lose power in a hurry.... A fine thread on that bolt would be a very good idea....

Bob

--- End quote ---

It now is clear ....
Once preload known to get at OR above target power, any BACKING off on preload has the stop rod actually bottoming out on head of preload bolt sooner and the length of hammer coast to poppet impact actually increasing .... Cleaver indeed !

Joe Brancato:
Bob, Very informative. Thanks for sharing.

Happy Pneu Year to all.

SpiralGroove:
Hey Bob,
Thanks for bringing to the Masses what the Custom Shops are already doing 8).
I need to think about working this into some of my guns ;). 
A 74% increase in efficiency is like having two days of Christmas ;D.
Kirk

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