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Forums10
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Mar 29th, 2024
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Joined: Feb 2012
Posts: 19
Boxlock
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OP
Boxlock
Joined: Feb 2012
Posts: 19 |
hello all
Can someone explain the principle of "over-center" that is often used in armory and if possible give exmples
thank you
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Joined: Apr 2011
Posts: 610
Sidelock
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Sidelock
Joined: Apr 2011
Posts: 610 |
I think the term might be used to describe the position of the break open lever. Left of center the hook, or pin are worn; right of center means usually OK.
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Joined: Apr 2002
Posts: 6,812
Sidelock
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Sidelock
Joined: Apr 2002
Posts: 6,812 |
If you're talking about the "over center" principle, it's a mechanical device which conserves and redirects the force placed upon a lever or spring attached to a cam such that a movement "over center" (point of no return) is converted to a further automatic (not requiring further effort) movement of the lever. Common examples: the Southgate ejector mech in AyA doubleguns, opening mech of common jacknife, the toggle lock mech of the sliding breech in the Charlin double shotgun. All over center devices have in common resistance to motion in both directions of the toggle or lever.
To illustrate the possibilities of the over-center principle, an authority on French sliding breech shotguns has stated that the sliding breech of a Charlin cannot open on firing despite the absence of a locking mechanism other than the position of the toggle relative to the cam when totally housed in the breechblock body.
Last edited by rabbit; 10/15/12 04:39 PM.
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Joined: Dec 2001
Posts: 12,743
Sidelock
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Sidelock
Joined: Dec 2001
Posts: 12,743 |
To add just a bit to Rabbits description, this reversal of action is quite often used as a lock. Examples of this are the toggle actions of the Henry, Win 66 & 73 rifles; the Luger pistol etc. On all of these actions once the hinge of the toggle has passed center & reverse force applied the lever is stopped from further movement thus locking the bolt against the breech of the bbl to resist bolt movement on firing. In the case of the Henry/Winchester the gun is then opened by simply moving the lever downward, while in the Luger semi-auto action the bbl & bolt recoil locked together until the hinge is forced back up above center by cam rails, the bbl then stops & the bolt continues rearward ejecting the fired case & picking up a new round.
The term "Overcenter" really has nothing to do with the position of the opening lever on a break open gun. The lever goes past center or left of center but there is no over center camming involved.
There are many clamping devices used in industry for rapid parts change in machining which use the over center principal.
Miller/TN
I Didn't Say Everything I Said, Yogi Berra
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Sidelock
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Sidelock
Joined: Apr 2002
Posts: 6,812 |
How about the later Winchester lever rifles, Pipes? How does their locking mechanism depart from the earlier rifles? How about dropping block rifles like the Farquharson and Ruger 1? What locks the breechblock in these?
jack
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Joined: Dec 2001
Posts: 12,743
Sidelock
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Sidelock
Joined: Dec 2001
Posts: 12,743 |
Jack;
Beginning with the John Browning designed model 1886 Winchester the lever was connected to locking bolts which fit in grooves in the sides of the receiver. Opening the lever dropped the bolts releasing the Breech bolt & closing it raised them either behind the Breech bolt or in grooves in its side. This resulted in a much stronger locking than the toggle linkage design of the earlier models. Winchester did not have an action capable of containing the .45-70 Govt cartridge until Browning designed the 1886 action for them. The 1876 was also a toggle action, don't recall off hand if there were any others or not. The 1886, 1892, 1894 & variants of each as well as the 1895 all had the stronger locking bolts.
The dropping block rifles are secured by the receiver walls behind the block, they only have to be held up to remain closed, but there is virtually no downward force on them in firing.
Miller/TN
I Didn't Say Everything I Said, Yogi Berra
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Sidelock
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Sidelock
Joined: Apr 2011
Posts: 1,850 |
Just my opinion but I think that the 1886 Winchester was their finest lever action. 
Practice safe eating. Always use a condiment.
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Joined: Apr 2002
Posts: 6,812
Sidelock
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Sidelock
Joined: Apr 2002
Posts: 6,812 |
Thanks Pipes. I should have known that no such arrangement was necessary to the Ruger 1 due to the breechblock sliding in dados in the receiver wall.
jack
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Joined: Dec 2001
Posts: 12,743
Sidelock
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Sidelock
Joined: Dec 2001
Posts: 12,743 |
J R B;
I have never persnally owned an 1886 so not really qualified to comment, but I do know that a lot of folks would agree with your assessment of them. As I recall the 1892 was based on a scaled down version of the 1886, while the 1894 had some design changes, but still carried some of the same principals.
Miller/TN
I Didn't Say Everything I Said, Yogi Berra
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Joined: Dec 2001
Posts: 775
Sidelock
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Sidelock
Joined: Dec 2001
Posts: 775 |
I think that the reason for Winchester not making a toggle link action in .45-70 was probably more due to the length of the action that would have been required, rather than the strength of the design. The model 76 was built in .45-75 and .50-95 calibers which would probably have just as high pressures as the original .45-70. The model 76 is a very heavy gun as it is, so lengthening the action to handle cartridges of the .45-70 class just wasn't practical, in addition to the model 86 and later Browning designs being much stronger and suitable for the smokeless pressures that came later.
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