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HM126 Drive Belt Tension

Started by Johnkeller1979, November 17, 2019, 11:26:46 PM

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Johnkeller1979

Quote from: mtoo747 on November 20, 2019, 09:17:59 PM
John, are you using a torque wrench when you set your band tension to 25 ft/lbs? I was using an old school beam type when i first got my mill last fall and couldn't really get consistent results so i finally bought an inexpensive click type (like $30) and have much more confidence in the consistency of my band tension now.
How long have you had your mill and did it ever run well for you? I know the frustration you are having but keep after it and when it does all come together it will be worthwhile and a lot of fun.
mike
Hey Mike, yes sir. Ive always tensioned with a torque wrench. 
I've had the mill for about 6 months, I've sawed about 10 logs. It ran good when I first set it up. Then slowly over time it's gotten worse. So I have hopes and it makes sense that I'm just not quite back where it needs to be  notand it's like a lemon or whatever. 
Just hit some road blocks along the way. Might be my personality, but I kinda dig it that in learning how every little part of it works, I think it's valuable information for the future. 
And thanks! 
HM 126 Learning..

btulloh

I just got home and read the latest additions. I'm getting a good idea what's going on now.  I have a few questions and a long reply, but I have to add that in the morning when I fire up the computer. (I'm on an iPad now and typing on it is too slow.). Plus I'm beat. Don't make a move until I can get back to this in the morning. Definitely don't switch out those bolts on the engine mount. That would put us further down the rabbit hole.

Ill be back in the a.m.  

Zzzzzzzzzzzzzzzzz
HM126

btulloh

Ok, back at it now . . .

First a couple questions:

- The saw was aligned and sawing fine initially and then things started going downhill, right?

- You said you've sawed 10 logs - how big and what kind?  How many bd ft would you say you sawed?

- how many blades did you go through to saw the 10 logs?

- The alignment an tracking were ok originally, but not after you replaced the wheel bearings?

HM126

btulloh

If it was OK and then something changed and the alignment is off now, so lets dig into what changed.  After replacing the wheel bearings, you started to have alignment issues and vibration, if I read everything correctly.  That tells me to look at the wheels and bearings and see what's different or got missed.

I looked at the exploded view in the manual.  There are no washers or shims behind the wheels, so that's not the problem.  I see that the bearing retainer ring faces OUT.  Did the wheels get reinstalled with the retainer ring facing IN?  That would change the offset and put things out of alignment for sure.

The motor mount was OK before, so it should be OK now.  Using smaller bolts so you can move it back would be correcting a problem that started somewhere else.  It would also make it hard to keep the engine from skewing when tensioning the drive belt.  Those should be a fairly tight fit both on the engine bosses and the mounting plate.  That keeps things aligned when tensioning.  For the record, I haven't any issues with the engine skewing when putting tension on the drive belt.  It stays in alignment pretty well.  

Things happen and two different mills can act a bit differently, but I've sawed several hundred logs up to 26" and haven't had any bearing issues or anything other than normal maintenance to keep up with.  It seems unusual that you would run into bearing issues that early on.

I suspect that the degradation in sawing performance was from a dull blade
HM126

btulloh

to continue . . . (the keyboard stopped working - restart)

So anyway, blade starts dulling, working harder, drive belt stretches a little due to normal break-in, cut quality degrades . . .  It would be normal with a brand new saw for the belt to stretch and maybe initial alignment drift a little.  Then it's time t0 re-tension the belt and touch up the alignment.  Does any of this sound about right?

I'm curious to see what you were sawing and how far you pushed your blade.  I rarely can get more than 200 bd ft out of a blade.  These saws run a little lower band speed and are bit under-powered, but that's the nature of things.  Mine is only 9.5 hp - the bigger engine was not available at the time.  I accept the trade offs that come with buying the lower end saw. That means we can't get as many bd ft as the bigger saws with the 25-30-35 hp engines.  Also we're cutting bark usually, and the bark has trapped dirt etc even if the logs weren't skidded.  That takes the sharp out pretty quick.  A tree growing for 50, 60, 70 years or so gets a lot of wind-blown dirt embedded in the bark, and this is quite abrasive.  If the logs were skidded and picked up dirt or mud, even worse.  So sawing into bark drags the abrasive dirt through the cut and dulls the band quickly.  

 - - got off into the bark thing there.  Maybe preaching to the choir.  Sorry if this is old news.

On checking the throttle cable:  The easiest way to make sure it's still correct is to grab the handle and go full throttle, then reach over and try to increase the throttle lever on the engine.  If it picks up speed, the cable has stretched a little.  (Just making sure - we can't afford to lose any rpm's.)

 

HM126

Johnkeller1979

Quote from: btulloh on November 21, 2019, 09:01:14 AM
Ok, back at it now . . .

First a couple questions:

- The saw was aligned and sawing fine initially and then things started going downhill, right?

- You said you've sawed 10 logs - how big and what kind?  How many bd ft would you say you sawed?

- how many blades did you go through to saw the 10 logs?

- The alignment an tracking were ok originally, but not after you replaced the wheel bearings?
I really appreciate this! 
The saw really did run great when I first set it up, followed all the procedures and it worked just as it was supposed to. I know I pushed the blades past their limit. This might of caused alot of stress to the machine. Some of the logs were fairly good sized, cottonwood, pines, ash - I get most of my logs from the tree dump here in Nebraska (home of Arbor Day, home of worlds largest man made forest, but not too many trees available haha.) And probably alot of dirt and sand on them. 
And no, the tracking was a mess before the bearings, I thought the bearings were fine, but at the time I had some advice about switching out the bearings and figured the diesel I was using that had deteriorated the belt, beyond use, might have effected the bearings too. But the bearings are seated and snap washer is facing out. I honestly felt really confident that the belt being worn down to the metal on the bandwheel was the problem, but new belt(s), and still problems, Im just not sure if its the same exact problem. I dont think I looked at things as close as I am now back when I thought it was the belt. 
Thats a really good point on why I would need to change the mount if it worked before.. Unless it never was lined up properly from the factory, maybe thats part of why the original belt wore out in such a short amount of time? Partly? 
Im going to head out there and look at things again. 
HM 126 Learning..

Johnkeller1979

Okay, so I think im getting closer! 
Vibration was indeed from the throttle, thought it was wide open, but the stop-set screw was in a little too far, Im guessing it simply vibrated out of place, or maybe the motor just wanted to be running at a bit higher rpm due to the colder weather. 

I got everything tracking really well, the belt aligned really nice and with the old blade on, it just hummed like a bee! 

I made a cut just to see what she would do and I could feel the blade was really dull, I think it decided to pop off only because it pushed it back off the wheel. 

So I got my new double hard blades today and ran back out to see how they would react with the machine. I noticed while putting them on that they are quite a bit larger than the lennox. Now I cant get them tracked, just a minor adjustment one way or the other sends them too far forward or backwards. 

I didnt have much time to investigate, but just wanted to say thank you so very much to everyone that helped get my machine this far, I think its right where it needs to be just need to get the new blade situation figured out. 

A many thanks again!!! 
HM 126 Learning..

WoodyPhyseter

Quote from: btulloh on November 20, 2019, 09:00:25 AM
Good info from @mtoo747 , especially the throttle cable.  Mine stretched also early on.  It's easy to miss but easy to check and correct.

I'm also surprised your wheel bearings needed replacement so quickly, but it is what it is.

Reading some other threads about belts, it sounds like the belts from Woodmizer are a better breed of cat.  I'm going to try some.  All the belts I've tried from various sources don't seem to be as good as what they are describing.

You have the right attitude: "It's going to work!". And it will.  Just a little fiddling required to get there.    My experience with the HM126 has been just like the vertical bandsaws in my shop.  Adjust and re-adjust until it runs right, then things work well from then on.

I'm curious about what you said measuring the tilt and alignment of the wheels:  Were they under full tension when you were checking them?  Your results in the vertical and horizontal checks sound like things are still pretty far out.  

I finally went and checked my manual this morning.  The reference to the left side (drive side) vertical adjustments only talk about loosening the bolts slightly to allow the shaft to move during horizontal adjustment.  There is no procedure outlined for checking the vertical tilt and adjusting.  This would mean that it's expected to be correct when you receive it.  I don't remember doing anything initially other than the procedure outlined in the manual for initial tracking adjustment, so mine must have been ok.  Seems like advice from the factory tech is the best course there.

One thing about the overall tracking adjustment though.  The drive side and the follower side do interact and you have to go back and forth.  It's a little tedious because you have take the tension off to adjust.  You can leave the "vertical bolts" slack on the drive side while you're doing this.

At some point in this process, the blade will track ok (staying put and staying on) but the overhang/offset may be slightly different on the drive side and the idler side.  I had to readjust the drive side a little at this point to get the same overhang on the blade.  Then re-adjust the idler side.  After a couple back-and-forths, they were both equal.  Life has been good ever since.

It sounds like yours is pretty far out right now, but it should come into adjustment pretty quick.  The process is a little annoying because of the walking back and forth and the release and re-tension of the blade each time.  

You only have to spin the wheels by hand a couple revs to see how it's tracking.  Good or bad tracking shows up real quick.  

One thing I did early on which really payed off:  I reversed the bolts holding the blade guard in place so the heads were on the inside.  Then I stopped hitting them with my gloved fingers when spinning the wheels.  Maybe that's just me, but life is better with the bolts turned around.

Good luck today.  Stay after it 'til it obeys your wishes!  Once it's right it should be smooth sailing.  

Looking forward to a report on those double-hards after you've got it dialed in.

BT  
Hi, I don't know where to talk about my worries with my 2019 hm126 portable.
You seem to know a lot so I'll try my luck here.

I've been very meticulous to follow all the proper tracking instructions fro the very first time I used my Woodland sawmill hm 126.  So I've got the tracking on point with the first three  days of milling.  Now (probably 30 hours of milling in) today I had my blade slip off for the first time.  It's partly my fault for not opening up the head before starting up from the day before.  I figured it was because of excess sawdust on the tracking side that got in between the blade and the wheel that made it slip off.  I havn't checked recently for loss of tension while milling,  but I'll do that.
Now...  when I was putting on my next brand new blade (wiped clean of course), I tracked it as I always do,  but on the BELT SIDE of the blade always seemed to come out of the wheel almost half way.  This was too much for my comfort and really messed around with the tracking,  going back and forth,  small 1/8th of a turn sometimes to see if anything would get rid of the OFFSET ON THE BELT SIDE WHEEL.  But nothing significant.  Then I thought that loosening the guide bolts weren't enough maybe and that the wood-gunkiness what keeping it too tight so i backed it up completely (but on the belt side) and tested it out at higher speed.  Stopped it.  Then I tightened by backing up the engine,  properly measuring that it's loose what "no more than 1/4 inch".  I'll note that I most likely did not have 25lbs of tension on the blade while I did this (then read in the 2020 manual on the woodland website that they need the tension on while you adjust the belt, it's a different mechanism though,  with a tensioner pulley, nothing to do with my 2019).  So tracked it back as best at I could,  leaving the tracker a little more backup to give the blade a chance of doing just that...

Third cut in and brand new blade came off.  So I called it a day, cleaned up and came searching on the net.
The troubleshooting in the manual says that one of the plausible causes of the blade coming off with a worn belt...  any thought on that,  it doesn't look at all that worn.  There is a little bit of a wobble if I try to shake the belt side wheel,  But i feel like that's normal...  I might be wrong.  I fallowed the rule of not playing with the belt side tracking and now I'm wondering what to do next.

Hopefully somebody who will have read trhough my problem will discuss this with me or redirect me to a thread that I didn't find.

Thanks everybody, 
this looks like a very nice comunity.

Jonathan, Arborist and hobby-timberframer.

mtoo747

Hello Johnathan and welcome to the forum! I had this reply written once and somehow managed to erase it so i'll try again. You should add your location to your profile as there may be someone close to you who can help. I doubt that you have a worn belt at 30 hrs on the mill and you are right to not mess with the drive side tracking. Sounds like you have a tracking or interference problem. Start by backing the blade guides back so that the rollers are not pushing the band forward. Put the band on both wheels so that the back of the band is flush with the back of the each wheel using only enough band tension to keep it in place. If you can't get it flush on both wheels you have an interference problem possibly those pesky little bolts holding the top clamp to the sheet metal guard. The band needs to be under those bolts not in front. Once you have the band flush to the back of both wheels apply your 25 lb tension using a torque wrench. Then turn your idler wheel slowly by hand to see if the band starts to walk. If it does, reposition the band flush again and with the T handle backed off one turn from full tension loosen the 24mm nut and make your tracking adjustment, tighten the 24mm nut, re tension the band and try it again. It may take a couple of adjustments but you should be able to run the band all the way around without it walking and it should stay flush with the  back of the bandwheels. Once this is set, reset your band guides so that you have correct clearance on the rollers and you should be good to go. Good luck. I will check back on this tomorrow.            mike

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