Bandsaw blade guides

When I built my sawmill I used the ball bearing blade guide design of my Delta 4" x 6" metal cutting bandsaw, which has proven less than ideal on the
sawmill, so I'm looking for alternatives. These appear to be popular: http://cookssaw.com/standard-roller-guide-assembly/
As I understand it, they should be positioned to lower the blade 1/8" to 1/4" below its free position to help it resist twisting in the cut. It concerns me that the blade back rests on and rubs the flange rather than a separate ball bearing. Does anyone have experience with operating and maintaining a bandsaw lumber mill?
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On 5/21/2020 10:01 AM, Jim Wilkins wrote:

I don't , but from what I've seen you post about it would seem trivial for you to design a guide with the features you want ... Use that basic design you posted the link to , but replace the flange with a ball bearing . I'm thinking something like a scaled up 4x6 guide with 2 bearings per side in a sleeve roller and a back bearing , single but also sleeved . Maybe use 4140 for the rollers .
--
Snag
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"Snag" wrote in message
On 5/21/2020 10:01 AM, Jim Wilkins wrote:

I don't , but from what I've seen you post about it would seem trivial for you to design a guide with the features you want ... Use that basic design you posted the link to , but replace the flange with a ball bearing . I'm thinking something like a scaled up 4x6 guide with 2 bearings per side in a sleeve roller and a back bearing , single but also sleeved . Maybe use 4140 for the rollers .
--
Snag

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"Jim Wilkins" wrote in message

This clearly explains the problem: https://woodgears.ca/bandsaw/resaw.html and this compares a variety of guide designs https://woodgears.ca/bandsaw/guides.html
The 2-directional curvature of the blade is also the reason why bandsaw blades and flat leather belts track to the center of crowned pulleys. An off-center band twists, bends and moves toward the higher side.
His buckling beam model has pinned ends (although the demo doesn't), free to pass the deflection past the guides to the wheel side. The "beam" ends can't be fixed because the tooth side which deflects forward out there won't tolerate running on guide rollers. The guide blocks or rollers can't press tightly against both sides of the blade due to the sawdust, some of which can carry around to the infeed guide if the wood is green or pitchy.
On a sawmill the usual answer is to increase tension and offset the blade downward slightly with the guide rollers to stiffen it. It can't move very far or the blade will crack.
I was using guides with skate bearings as rollers on one side and fixed rubbing blocks on the other, and a backing bearing. They worked well with a sharp blade but deflection started to be a problem once the blade dulled to half the amount I can tolerate, based on lowered cutting speed. So I cut wide planks with sharpened blades and then edged them or slabbed logs as the blade dulled. The salvaged motorcycle's speedometer shows blade speed and mileage.
The mod I'm designing now is 2" rollers with larger bearings, somewhat similar to the well regarded Cook's guides but with a backing roller or washer instead of the integral flange. I design home machinery for easy maintenance or modification instead of long wear life. Hopefully they will let the blade tolerate more downward deflection. Before disassembling the saw last fall I set the guides to barely touch the free-running blade to record its position for reference.
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On Sat, 23 May 2020 09:31:05 -0400, Jim Wilkins wrote:

[...]

With a reasonably fast micro, eg Raspberry Pi4, and an ok camera attached to it, plus a bunch of controlled motors and attached mechanisms, it's feasible nowadays to make an active sharpener, to touch up the teeth while the bandsaw is running. Feasible means possible to do; it doesn't mean easy. :) It would be a project that could last a few years longer than the several days of work your larger-bearings approach will take, and could cost a couple of magnitudes more dollars, depending on how many sawmills got wrecked during development.
--
jiw

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"James Waldby" wrote in message [...]

With a reasonably fast micro, eg Raspberry Pi4, and an ok camera attached to it, plus a bunch of controlled motors and attached mechanisms, it's feasible nowadays to make an active sharpener, to touch up the teeth while the bandsaw is running. Feasible means possible to do; it doesn't mean easy. :) It would be a project that could last a few years longer than the several days of work your larger-bearings approach will take, and could cost a couple of magnitudes more dollars, depending on how many sawmills got wrecked during development.
--
jiw
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"James Waldby" wrote in message
Feasible means possible to do; it doesn't mean easy. :)
============================================Or it means some dreamer thinks it -may- be possible.
Sometimes I/we could make it work, sometimes not. I had fun trying.
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"James Waldby" wrote in message
With a reasonably fast micro, eg Raspberry Pi4, and an ok camera attached to it, plus a bunch of controlled motors and attached mechanisms, it's feasible nowadays to make an active sharpener, to touch up the teeth while the bandsaw is running. Feasible means possible to do; it doesn't mean easy. :) It would be a project that could last a few years longer than the several days of work your larger-bearings approach will take, and could cost a couple of magnitudes more dollars, depending on how many sawmills got wrecked during development.
--
jiw

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