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Squaring Arm Linkage

Started by Rougespear, February 14, 2016, 05:03:41 PM

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Rougespear

I have three fold-down style squaring arms that I'd like to connect with a linkage so a single hyd cylinder can accurate all three.  Contrary to conventional "saw mill construction", I want to make the connecting linkage a weakpoint so that it will bend before the squaring arms do.  I was thinking of using some 1x1x1/8-wall tube or simply some 1"x3/8-thick flatbar in the vertical orientation.  Any thoughts on whether these profiles would collapse or fail under a push scenario?  (Obviously under a pulling condition they would be fine, but the cylinder has to push on the linkage to raise all the squaring arms)  What do the WM mills use?
Custom built Cook's-style hydraulic bandmill.

Ljohnsaw

Quote from: Rougespear on February 14, 2016, 05:03:41 PM
I have three fold-down style backstops that I'd like to connect with a linkage so a single hyd cylinder can accurate all three.  Contrary to conventional "saw mill construction", I want to make the backstop connecting linkage a weakpoint so that it will bend before the squaring arms do.  I was thinking of using some 1x1x1/8-wall tube or simply some 1"x3/8-thick flatbar in the vertical orientation.  Any thoughts on whether these profiles would collapse or fail under a push scenario?  (Obviously under a pulling condition they would be fine, but the cylinder has to push on the linkage to raise all the backstops)  What do the WM mills use?

My understanding is the backstops are the squaring arms.  Are you referring to the log clamps/log dogs as the squaring arms?
John Sawicky

Just North-East of Sacramento...

SkyTrak 9038, Ford 545D FEL, Davis Little Monster backhoe, Case 16+4 Trencher, Home Built 42" capacity/36" cut Bandmill up to 54' long - using it all to build a timber frame cabin.

Rougespear

Backstops = squaring arms... sorry for the terminology misunderstanding (I'll edit the original post).
Custom built Cook's-style hydraulic bandmill.

Ljohnsaw

OK, that makes more sense.  You could pull the arms into position with the push, pushing them over center and down.  I don't have hydraulics but I would think you might want the arms to nudge the log back over if necessary so they should be strong.  Keep in mind that due to the surface areas, the push is slower but more power than the pull.

You could mount the "arms" on the backstops with a single bolt, rather then weld in place.  Whether pushing or pulling, that connection could/would slip if sufficient resistance is encountered by the backstop.  Make sense?
John Sawicky

Just North-East of Sacramento...

SkyTrak 9038, Ford 545D FEL, Davis Little Monster backhoe, Case 16+4 Trencher, Home Built 42" capacity/36" cut Bandmill up to 54' long - using it all to build a timber frame cabin.

Ox

Why not limit the pressure the hydraulics will supply?  They make adjustable pressure relief valves.  You could then adjust the pressure sent to the ram to whatever you want it to be.
K.I.S.S. - Keep It Simple Stupid
Use it up, wear it out, make it do or do without
1989 GMC 3500 4x4 diesel dump and plow truck, 1964 Oliver 1600 Industrial with Parsons loader and backhoe, 1986 Zetor 5211, Cat's Claw sharpener, single tooth setter, homemade Linn Lumber 1900 style mill, old tools

etroup10

This is how I did it, right now they are just hooked up to a lever that I operate. I will probably put them on a cylinder eventually but for right now the lever works great. You could make the bolts week points(maybe use 1/4" bolts) or do what Ox said by adding relief valves.


NHLA 187th class, lumber inspector. EZ Boardwalk 40 with homemade hydraulics; Gafner Hydraloader; custom built edger, Massey Ferguson 50E, American Sawmill 20" Pony Planer; Husqvarna 55 Rancher

Brucer

The side stops on a Wood-Mizer mill are made from 1" thick plate, about 2" wide. The linkage is either a solid rod or thick-walled tubing. The cylinder relief valve will activate long before anything bends.
Bruce    LT40HDG28 bandsaw
"Complex problems have simple, easy to understand wrong answers."

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