Another build thread... JoshNZ

[Crusarius]

I like the eccentrics. I see a bunch of space to do threaded bolt there. all I did was drill and tap a piece of 1/2" x 1" stock then welded it to the plate next to the pillow block bearing. Just ran a bolt with a nut through it to tighten it.

[JoshNZ]

That's all I've got there. I started to do it but realised there is just no room, I could barely fit a bolt head + 12mm plate let alone a locking nut too, it's even tighter on the other side which I haven't got to yet.



 

I must have been tired or drunk this after noon I drilled out the M12 bolt holes in the plates and tapped for M14 hoping to get a bit more torque on them, and it looks as though I did it while standing on my head or something. Hopefully crooked bolts won't harm it.

Do you have adjustment bolts on both your forward and rear pillow block or just one of them? I hoped to set the eccentrics centred on the front pillow, align wheel by sight by adjusting rear pillow, torque it up, then fine tune with eccentrics without touching the other block. Which will work providing the rear pillow block doesn't creep along on its own as tension come on. I haven't got my gauge on the jack yet so I have no idea where I'm at with tension, I took it up the other day until the blade made a ping noise when flicking it and all I did was drag the pillow blocks along their slots. Maybe that's way over doing it though I don't know yet.

One thing has got me stumped looking at the cooks roller guide assemblies. What the heck is going inside the block behind the roller. It would make sense if it were just one whole shaft but it looks like a key/shaft at the back, and zerk bolt at the front are two pieces  ???. I'll have to scurry off to your thread and see how you did it

[Crusarius]

I used 3 adjuster bolts and one fixed pivot for the pillow blocks. That is one area in the Linn plans I did not vary from.

I would definitely make an eccentric for each bearing, except the one that has the fixed stop. This is another one of the linn parts I kept. This is just and eccentric with a bolt to hold it in place. It is surprising how this little bit of holding has made a world of difference for not allowing any movement.

[JoshNZ]

What am I looking at in that photo?

[Crusarius]

that is the adjustable blade guide arm. the black circle is the eccentric for keeping it in place.

loosen the t-bolt then slide the guide in and out.

[JoshNZ]

That's what I thought. I'm ok with the positioning of the guide it's more the angle adjustment I'm confused about. I think I have an idea in my head though.

I ended up putting those eccentric bolts on both pillows of each side. I'm actually really happy with them. I only had a 4mm end mill which I thought was big but turns out you can poke a screw driver into them sideways and get a ton of leverage on it, they seem to work great.

I turned roller guides today out of the left over 40mm 4140. Will try and put together some kind of shaft/tube tomorrow.

Did you put rubber under your engine or straight metal on metal? And.. I was watching some of cooks videos and heard him say ideal adjustment for guides is with the back of the band running at about the end of the first groove (in my case, ~2mm from the lip of the guide). I would have thought you'd bring the guide up to the back of the band so it's barely touching when unloaded?



 

[btulloh]

Maybe it's just the perspective in the picture but those guides look too wide for the blade width.  If the blade moves back any more it will take the set out of the blade.

[Crusarius]

My engine is straight metal on metal. Even if I put rubber there the bolts would have held it tight so it did not matter. Plus my engine is in slotted holes for belt tensioning.

You definitely want more than 2mm spacing on the back of the blade. When you push the blade will deflect and contact the flange. This is not good. I have a little over 1/8" on both.

I do have to agree with btulloh about the guide width.

[JoshNZ]

I can remount and knock a bevel off the front if needed but it must be close, the blade is against the back of the guide in the photo and reaches maybe 1mm short of the gullet. How far back should it be?

I had the idea in my head the blade rode that flange for support. Like a workshop wood bandsaw. Lucky

[btulloh]

If the blade is behind the gullet, you're ok.  Might be worth checking with Cooks to see what the official story is.

[JoshNZ]

It is definitely behind the gullet but you're right it is close, maybe .5mm.

Might be a bit rude calling cooks seeing I've not purchased anything from them hah. Will see what others here think. A bevel on the nose of the guide won't harm anything will it. That'll give up to 2-3mm more relief if I had to.

Thanks for mentioning it!

[btulloh]

Seems like a bevel would cure it, if it's a problem.  Most I see have more blade forward of the rollers.  

A Woodmizer manual would have something about it, if you want to check that.  No doubt some others will chime in this evening, so that should clear it up anyway.

If it's at the back flange in the picture, it can't move any further back, but you might find yourself running a blade with a deeper gullet some day.

[Magicman]

Be sure that the blade guides have some horizontal tilt so that if/when the back of the blade contacts the flange, the blade is pulled into contact with the guide by the flange.  Yup, a bit of scraping takes place as the blade passes under the blade guides.  In the final setup the guides will exert about ¼" deflection below the bandwheels and be absolutely parallel with the sawmill bed.

[JoshNZ]

Got it, that makes sense.

I pretty well copied the cooks guide loosely. I bull-nosed a drill bit for round-tipped bolts to hold the front of the shank and flats at the back for the guide bolts (after rounding the flats too then filling with weld   hence its new colour)



 


 


Rather than using front bolts to set the roller height I made the whole arm telescopic. I've not welded it together but there's an idea of how its going to work.




 



Just the sliding guide to go and I'll be able to run a test cut I think

[JoshNZ]

I tracked the blade today and ran the engine up. The whole band gets a pretty wild standing wave in the top of it 

Not sure where to start with it, it seems like an engine vibration type frequency rather than wobbly wheels or something. I may have to make isolation mounts for it?

[TreeStandHunter]

Josh you should post a video of the wave. Does the blade have proper tension?

[JoshNZ]

I still haven't got my pressure gauge yet so not sure what I'm running. I tried varying it from loose to solid. The engine does cause a rattle in the whole frame at about 3600, if I push passed it to 3700 it smooths out.

Will take a video in daylight tomorrow. I've just been looking at bobbin mounts they look like they'd prob be worth having anyway?

[Magicman]

I'll have to look for a picture but the top gets a "damper" between the bandwheels.  Mine is an adjustable bolt but some mills use a wood block adjusted about 1/8th inch above the blade.

Edit:  Nope, I do not have a picture.  Guess that I was remembering what is in my operator's manual.

[Old Greenhorn]

Harmonics in fabricated structures can drive you mad if you let them. You need pretty fancy software to predict resonant frequencies in such things and frankly I don't think it's worth it. The condition exists. The good news is that these can be countered in strange and simple ways such as MM indicates. That is a direct method and probably the best and simplest. A spring load idler wheel would likely work too. The other alternative is to change the resonant frequency, but given that it is a long blade it could get very complicated because I suspect it is low frequency. The top of the blade is non-functional so how far do you want. or need to go? Your solution could be as simple as a few small weld gussets to shunt the vibration in a different direction. Just discussing here to give you some different thoughts. Likely you have already run these through your head. Given your skills, I have have no doubt you will nail it down.
 Good luck, I am enjoying your build!

[JoshNZ]

I've run all sorts through my head but by all means don't stop the suggestions haha.

I think I'll do three things, I'll take the engine back up to 3700RPM where the frame is happy and re size the last pulley to suit. Put it on bobbin mounts which can't hurt. And I'll see what I've got by then if it's still making a wave I'll figure out where the nodes are and put an idler beside one

[Crusarius]

Did you cut anything? you will find that once the blade enters the log the bounce goes away.

[JoshNZ]

I wouldn't have gone near it in a bomb disposal suit never mind cut anything, I'm talking a standing wave with a 2+ inch amplitude .

I've learned a few things one being the jack was creeping. I don't know if it had a bubble in the cylinder that had to leak out past the ring or if there was a bit of crap in the seat but it doesn't seem to be doing it now. I took the engine up to 3700RPM and with the jack staying put it seems to be a lot better. I have added a video below, can you guys tell what sort of tension I'm at from a tap? I've never actually seen a sawmill in flesh and have no equipment yet so I'm absolutely guessing.

The band is still a bit fuzzy but that's with no guides yet.

I think I could probably find a set of these bobbins for $100. I know why you wouldn't if your belt drove your drive wheel but I do have a jackshaft with an idler, I think it'd prob be a well spent hundred..?



 

Runup - YouTube

[JoshNZ]

I got most of the other guide done today. Just a piece of turned rod sliding in some tube with a bit of angle iron slotted on one side for vertical adjustment and the other for forward/back. I'm going to add a rod of the same size running along the beam and support it from that also, maybe by a brass bush in split clamps or something I'm not sure yet.



 


 

It's got about every adjustment other than time travel...

How close do the guides need to be able to get? I just eyeballed a piece before putting it on the lathe and I'm wondering if I've come up a bit short now. Say 15 inches?



 

[Ljohnsaw]

15" is probably fine.  I have mine set at 20-25" and I just don't adjust it much at all.  Even when I'm down to slicing off 2x4s.

I do have a question:  How are you keeping the rod from twisting and messing up your roller angle?

[Crusarius]

Can't ask for much smoother than that.

I agree 15" is fine. lots of times I just leave the guide all the way out and keep cutting. Seems every time I move it in I forget and have to stop cutting to move it out then resume my cut.

I really like how your guides came out. My version 2.0 will be using something very similar.