Another build thread... JoshNZ

[Crusarius]

Take a look at my pictures. the top of my carriage extends past the uprights and my bracing is on the outside of the frame. Works pretty well. 

[btulloh]

Add in round tube torsion bars.  Big diameter, thin wall.  Exhaust pipe and emt are my go to for light duty stiffness increasers.

Interesting. Where would these be placed?

[JoshNZ]

I thought I'd come back here and probe the knowledge base again. I need to stiffen my carriage to stop it racking side to side while cutting up high, it's driving me nuts.

The saw runs pretty flawlessly up to about 400mm cutting height and below. For opening cuts and first few flitch cuts on descent sized logs above this, the cutting force has a decent lever to torque the whole carriage around its feet if that makes sense. This causes the carriage to flex away from the cut and then eventually gets into a rocking harmonic.

What it needs is an angle brace from corner to corner to restrain this movement but obviously that runs right through where your log is sitting. Any ideas..? I have braced the carriage legs at the corners but I assume the problem is the thin 3mm wall 50x50box flexing below this brace point.

Is welding on doublers a waste of time?

Crank the head up quite high and try pushing on it to see if you can cause it to sway. If so, weld some cross pieces just above the largest diameter log your mill can handle. Maybe first try clamping some pieces across to see if the sway goes away. Mine uses 38 X 38 X 5mm tubing and it is rock steady.

I have actually tried exactly this already and if anything it made it worse, prevented that racking movement but exacerbated another problem where the carriage shimmys on the tracks. I.e. one side of it advances more than the other, then vice versa, and develops a harmonic rocking in that direction.
I'm not really sure why this happens whether it's the legs twisting/walking or if the whole carriage is rotating. I thought a good idea may be to add a power feed so the legs are tied to the same point, then add the cross brace. But that's getting on towards territory where it might be better to just sell it on and start again. I'm gagging for a set of hydraulic levers to handle logs hah!

[RAYAR]

I thought I'd come back here and probe the knowledge base again. I need to stiffen my carriage to stop it racking side to side while cutting up high, it's driving me nuts.

The saw runs pretty flawlessly up to about 400mm cutting height and below. For opening cuts and first few flitch cuts on descent sized logs above this, the cutting force has a decent lever to torque the whole carriage around its feet if that makes sense. This causes the carriage to flex away from the cut and then eventually gets into a rocking harmonic.

What it needs is an angle brace from corner to corner to restrain this movement but obviously that runs right through where your log is sitting. Any ideas..? I have braced the carriage legs at the corners but I assume the problem is the thin 3mm wall 50x50box flexing below this brace point.

Is welding on doublers a waste of time?

Crank the head up quite high and try pushing on it to see if you can cause it to sway. If so, weld some cross pieces just above the largest diameter log your mill can handle. Maybe first try clamping some pieces across to see if the sway goes away. Mine uses 38 X 38 X 5mm tubing and it is rock steady.

I have actually tried exactly this already and if anything it made it worse, prevented that racking movement but exacerbated another problem where the carriage shimmys on the tracks. I.e. one side of it advances more than the other, then vice versa, and develops a harmonic rocking in that direction.
I'm not really sure why this happens whether it's the legs twisting/walking or if the whole carriage is rotating.

This is starting to sound like the carriage wheels are fixed in that they have no ability to move a bit sideways on their axle to compensate for any slight track width differences. The carriage wheels on one side need to have this ability to roll down the track smoothly, otherwise, they are trying to climb and it would cause a side to side walking as you are experiencing. I can't remember if this was brought up during your build.
Actually, even if your tracks are perfect, the flexing in your carriage frame could still cause this walking effect if the carriage wheels on one side have no lateral movement ability to ride the rails as intended. Also, any bit of sawdust compaction on the track and wheels can cause shimmy as you roll the carriage down the track.

[mike_belben]

Interesting. Where would these be placed?

Wherever the builder determines that the current structure is experiencing a torsion issue.  If we are talking in the language of a solidworks build, the uprights are coincident to a plane or planes, and plumb and square to each other yada yada.  His racking oscillation is a case of leaving coincidence then spring back past it then springing back before it then...  



So it needs a torsion-cancelling member to dampen the oscillation, which round tube is superior at.  Looking at how tall the legs on that giraffe of a carriage are, consider the leverage that the hoof end is putting on the tubes that make up the torso. There is a lot of multiplication in those long legs and any force in them is acting against the horizontal top pieces.

  The chinup bars up there are not resisting the torsion between two legs trying to walk 2 ways at one time so each is being allowed to.  The chinup bar twists up and untwists.  


Sister those up with round tube to cancel it. Youll see an immediate stiffness increase when you find the issue.  

[JoshNZ]

I thought I'd come back here and probe the knowledge base again. I need to stiffen my carriage to stop it racking side to side while cutting up high, it's driving me nuts.

The saw runs pretty flawlessly up to about 400mm cutting height and below. For opening cuts and first few flitch cuts on descent sized logs above this, the cutting force has a decent lever to torque the whole carriage around its feet if that makes sense. This causes the carriage to flex away from the cut and then eventually gets into a rocking harmonic.

What it needs is an angle brace from corner to corner to restrain this movement but obviously that runs right through where your log is sitting. Any ideas..? I have braced the carriage legs at the corners but I assume the problem is the thin 3mm wall 50x50box flexing below this brace point.

Is welding on doublers a waste of time?

Crank the head up quite high and try pushing on it to see if you can cause it to sway. If so, weld some cross pieces just above the largest diameter log your mill can handle. Maybe first try clamping some pieces across to see if the sway goes away. Mine uses 38 X 38 X 5mm tubing and it is rock steady.

I have actually tried exactly this already and if anything it made it worse, prevented that racking movement but exacerbated another problem where the carriage shimmys on the tracks. I.e. one side of it advances more than the other, then vice versa, and develops a harmonic rocking in that direction.
I'm not really sure why this happens whether it's the legs twisting/walking or if the whole carriage is rotating.

This is starting to sound like the carriage wheels are fixed in that they have no ability to move a bit sideways on their axle to compensate for any slight track width differences. The carriage wheels on one side need to have this ability to roll down the track smoothly, otherwise, they are trying to climb and it would cause a side to side walking as you are experiencing. I can't remember if this was brought up during your build.
Actually, even if your tracks are perfect, the flexing in your carriage frame could still cause this walking effect if the carriage wheels on one side have no lateral movement ability to ride the rails as intended. Also, any bit of sawdust compaction on the track and wheels can cause shimmy as you roll the carriage down the track.

I definitely turned bushes so none of the wheels could slide on their axle, so that is interesting. I'll drop the bushes out of both the wheels on one side and see how that goes.
What're you saying in practical terms Mike? Where would the addition of tubes go exactly if you were to stiffen the chinup bars

[mike_belben]

Post a few good clear closeups of your carriage top from a few angles, particularly top down please.

[JoshNZ]

Here you go @mike_belben better late than never, I put it in the too hard basket back then, one thing about having the mill offsite on piles under a roof is it's really hard to get motivated to do major maintenance on it. Until today when the carriage fell flat on its face =/. Photo below.

So it's in the workshop, I've got a list of things to do to it. I think the problem we were talking about is because, the moment about the carriage wheels caused by the bands force is enough to deflect the skinny legs, simple as that. I need to stiffen them. Which is a real pain being that they're painted. Ends are sealed so would be tricky to put tube up inside them too. Add flat bar to sides of tube?



 

 

I showed up today to do some milling, it took me about 45 seconds to completely wreck my day hah  :.

I went to drag the carriage to the end of the bed, I saw a little offcut maybe 1/2x1" laying across the bed, thought it'll either move or snap and carried on. The little stick reared back then let all its spring tension go sending the carriage into a turning wheel stand, the wheels slightly missing the track on the way back down and of course splatting on its face. I couldn't believe it, anyone watching would've sworn it was designed to do it it happened so quickly. Real David and Goliath moment. The machine I designed to slice 2ton chunks of wood was foiled by a twig haha.

Anyway, crushed all the guards, and bent the guides, that's the worst of it. I thought I'd be rebuilding both but I've spent the evening working on it with a rubber mallet and will just call that good enough.




It frustrates me that I didn't make it captured by the bed. Would he really hard to do now without just converting to linear rails. I'm thinking 2.0 will be on the way later next year, and don't want to get into that.

I am most of the way through my pile of logs, still a pile but it's small enough that I can look at them all and know what I'll do with each one and when roughly, rather than see a giant unweidly pile I might never get to the end of.

I modified my ltaga sharpener to take big 150mm chainsaw grinder stones. I couldn't for the life of me source a woodmizer stone so had to figure out something else. I actually bought another chainsaw chain grinder, pinched the motor and binned the rest as it was cheaper than sourcing a motor in NZ.. machined the arbor and modified the guard to fit everything, it goes really well now anyway, twice the power at least and is producing good results when the bands go on. I have got a CBN wheel on the way for when I get started on my pile of kasco 4 degree bands that arrived last week. Still a dozen or so of these nonames to get through.



 



The slab pile has got away on me, we've started stacking them into a frame, strapping then chainsqwing straight into firewood bins. Just realised how much is there, 20x what I can use/store myself so will have a big firewood day with friends sometime soon. a wood splitter is the next project on the list!

[mike_belben]

Wow that was a trainwreck. Glad you werent hurt.

 I think youve got a balance issue to sort out from all the components to one side.  Either lengthen the feet toward the saw to get the toes under the body more, or hang ballast weight on the back side.  I would hang test ballast to see if your racking has been a case of a saw trying to fall over while in the cut. 

I will have to review the other part later, im up with a sick kid right now.

[Crusarius]

Josh, I forget how you made your rails. I was very concerned about what you just mentioned so I added a small hook to go around my rail. not perfect but it has saved me from doing that exact thing you just did.

[JoshNZ]

Yeah I can't do that not without cutting and removing some stuff. The mud guard brackets and the travel flaps. I could probably put both on the inside. Or I could make a cam follower inside the bed that'd prob be easier

[Crusarius]

doesn't take much to hold it down. Definitely worth doing.

[JoshNZ]

It would take a lot for me because of the work involved. Cutting and repositioning and repainting. And our country is in a kneejerk lockdown I couldn't get material for a while either. Better to just get it running again I'm actually really busy on the thing I can't cut it fast enough at the moment. I think once these logs are done I'll sell it and start again, I should have a new workshop completed and moved into by the end of summer, will be a great next project. Some part of me knows it's happening already as there is a collection of rams/hoses etc gathering in the shelves haha. I sure wouldn't be pushing the carriage or handling logs manually if I had any idea I'd be in this situation 2 years ago. Brilliant hindsight.

[RAYAR]

I showed up today to do some milling, it took me about 45 seconds to completely wreck my day hah  :.

I went to drag the carriage to the end of the bed, I saw a little offcut maybe 1/2x1" laying across the bed, thought it'll either move or snap and carried on. The little stick reared back then let all its spring tension go sending the carriage into a turning wheel stand, the wheels slightly missing the track on the way back down and of course splatting on its face. I couldn't believe it, anyone watching would've sworn it was designed to do it it happened so quickly. Real David and Goliath moment. The machine I designed to slice 2ton chunks of wood was foiled by a twig haha.

Anyway, crushed all the guards, and bent the guides, that's the worst of it. I thought I'd be rebuilding both but I've spent the evening working on it with a rubber mallet and will just call that good enough.

My mill also just sits on the rails by gravity, nothing to keep it from tilting off. I've run into many things on the tracks and the carriage just stops instantly, I never noticed it try to tip. I've thought about this often, and looked at what can be done to remedy this problem. Maybe I can move my traveling carriage lock downs to the inside of the frame rails so they don't interfere with adding carriage anti-tilt on the outside edges of the frame rails. Will have to look at my mill again with this idea in mind.

[JoshNZ]

I've run into things too, clunked into the log dog handles laying on the tracks while trying to gig back (that's a bit of a gotcha with my mill), jammed wheels with trimmings, rammed the guide adjustment bolts into back stops, gone too fast into the bed end stops, etc etc. Never seen it tip. You can imagine my disbelief when the entire thing splattered from a stick it was flat on its face before I could mutter what the fa...

I don't think it would be far off centre balanced laterally, and I designed it to be pretty well balanced on the lifting screws, which I had to do since it only has one linear block per side. Which is a little forward, but pretty central.

With the thing on the workshop floor I can push across the carriage and get a bounce going, it racks laterally.

I was thinking today I could add RHS to the sides of the rear posts and to the front of the forward posts. Would take a bit of fiddling with but it might be worth it.

Also thought of a pretty easy way of adding a cam follower. I just don't know if I will. I've got another couple of weeks of sawing to finish this pile then I might even sell it. And start hoarding for 2.0

[mike_belben]

I think i would put the carriage on a concrete floor and use a 2x4 on edge like a rafter to find and make the balance point on each side.  It may be that getting that neutral with ballast solves much of your cogging issue. ?

[JoshNZ]

This is the movement here that I'm trying to eliminate, and it's obvious how the blade creates the same force I'm applying from the side.

racking - YouTube

Not discrediting it could be a balance issue but I don't understand how myself, I think it's purely a strength/stiffness issue.

Removing the bushes from one side's wheels seems to have fixed the other issue I was having, no more walking effect.

[Ljohnsaw]

My head does the side to side shake when cutting some logs - usually the wide ones.  If I adjust the cutting speed or push a little to the side as it heads my way to cancel it out.

[Old Greenhorn]

Yeah, that is flex in those vertical members. Yeah, I know it's painted already, but adding some 1/4 x 1-1/2 flat bar welded edgewise to those verticals will do wonders for rigidity. Now the twisting you will get in the cut will be more challenging. ;D I am still trying to figure that one out.

[Hilltop366]

Wondering if you could make the side a truss by adding a piece of rod down the side that forms a triangle with a few up rites?

Trying a few different ideas could be done with some clamps and vice grips instead of welding.

[JoshNZ]

Mine only does it in large logs too but it's not because they're large, it's because they're tall. I can take a 35" wide cut 6" off the bed and it glides through it, makes me smile. But I can do a 10" wide opening slab cut on a 35" diameter log up at 32" high and the thing acts like it's made out of cardboard sometimes.

I can sometimes adjust feed speed or angle of pushing or bounce against it myself or whatever and settle it, but sometimes it just gets into a harmonic and a bit unweidly and I have to stop and let it settle, then carry on.

I could do basically anything to the rear posts as they've got nothing around them. But the forward posts have linear rails on the back, bolt heads from the linear rails on the front (could drill access holes or tap threads for bolts) and blade guard frames/wheels etc all around it. I've got enough room to add a 1x2" rhs to the side of one post and the front of the other post.

Also thought I could make a truss like section on the back. Could just stitch the rhs on its long edge to the sides of the rear posts.

I'm just wondering is it all worth it or is it gonna do it to some extent regardless.

[RAYAR]

If you can take the flex out of it, then it should be rock solid afterwards.

[JoshNZ]

I have a 40ton press behind it that would argue, anything is flexible xD. It would be nice to know for sure if this will be worthwhile before I start burning paint. I think I've gotta have a go.

I could add a 2" SHS to the back post's sides and, a 1x2 rhs to the front of the forward left post on its flat edge and one to the side of the forward right post on its flat edge (so not as stiff).

Then paint it again I suppose. Maybe with a brush without dissembling

[mike_belben]

Gonna need you to spell out the abbreviations. Rhs, shs?

Problem is so obvious now.  got a pretty easy fix for this.. Lemme go sketch it. 

[mike_belben]

So your problem is those long legs arent rigid enough to dissipate the vibrations without taking on a harmonic.  The saw is grabbing wood and pulling the frame to the log then the wood tears and the frame, which has loaded up with energy, springs back away from the log over and over creating a frequency.


That why sometimes its fine (at the attenuation frequency) and sometimes its out of control (at the amplification frequency) and why you can sometimes nudge around and stop it .. Because you are becoming a human damper which sometimes prevents the machine from hitting resonant frequency.  If you dont catch it soon enough it achieves resonant frequency and goes bananas.  


You are sorta fighting a tuning fork that gets more sensitive as you raise the head because the unbraced length of those legs gets longer as the head is raised.  Length causes leverage against the legs and thus disadvantage to resist force of the saw pulling into the wood.


How do you stop a tuning fork from ringing?   Hold your hand over the legs.  Either squeeze them together lightly or pull them apart lightly.  They cant oscillate and your hand is now dampening them anyhow.  

So either build a fixed truss around the current frame to make it rigid enough, or build a lighter, cheaper tensioning frame with a turn buckle to pull them apart just a hair.   This is limited because the head wont lower if you spread too far.  But it could be as simple as rebar or cold roll rod. It will be in tension only if you do it right. 1/2" rod tensions buildings against 70mph winds. 





If your rollers have a lot of float on the axles look into taking that out if possible.  That should also help the bed dampen some of the frequency.