Wm spring blade tensioner conversion

[Crossroads]

I have a 1984 lt30 that has a spring to tension the blade and I can't help but to think that has something to do with some of the dips and waves that happen on occasion. Has anyone converted the old spring tensioner over to the new hydraulic style?

[Ben Cut-wright]

"dips and waves" can happen for numerous reasons.  Happily, checking band tension is one of the easiest factors to eliminate.  Converting to hydraulic adjustment has its benefits but I like the spring.  First, have you replaced the spring?  Next have you measured the stretch of the band to determine its proper tension?  After getting a baseline it is simple to add or subtract tension from measured stretch.  Adjusting tension may or may not alleviate the waves and dips, but getting proper baseline tension goes a long way toward eliminating one cause.  All that said, IMO, if you cannot overcome the wave and dip by properly adjusting the spring, chances are the hydraulic won't fix it either.   

[pineywoods]

The wm hydraulic tensioner is a real neat piece of design work. Simple and elegant. The real plus is it has a gauge that shows the actual tension, and it will vary as the blade heats up. With a spring, you are just guessing at best..Building your own would be simple enough. Arnold113 came up with a homemade design using the cylinder and pump off a cheap floor jack. My mill has the hydraulic tensioner, if it didn't, I would be building one post haste..

[Ben Cut-wright]

Happy Birthday, Sir!

Did you mean to state that the "hydraulic gauge shows the actual band tension"? 

If stretch-measurement of a particular band is correlated with either hydraulic gauge reading or spring measurement, one may use those indicators to set tension of this particular band. Please set me right if I am incorrect.     

[Kbeitz]

This is what i use...



 

[Crossroads]

I've not done any band stretch measurements or replaced the spring. I have made sure that everything has been squared up as stated in the manual. I thought I had it pretty well under control, but did a job last week cutting some fir that was pretty dry. I ran 4* blades and it seemed like 8-10' into the cut it would dip or dive following the grain or going around knots. I'm pressure washing the logs so,they are clean and change blades regularly. I'm running straight water on the blade, but the dripper gets plugged with sawdust quite often. Could it be that my blades are getting hot and either changing the tension or flexing and changing the set on the teeth?

[pineywoods]

The wm tension  gauge is actually a 0-3000 psi pressure gauge with the recommended pressures high-lighted. Yellow arc for 035 blades, orange for 042, white for 045, The hydraulic cylinder has a bore of 1 inch, makes it easy to calculate the actual blade tension if you so desire..The real advantage is you can see the pressure drop off when the blade heats up and expands. Sunshine on the head frame will cause the frame to expand enough to cause the pressure, thus the blade tension, to rise.

[Crossroads]

I looked in Arnold113 gallery and saw one picture of his tensioner, I need to look to see if there are any more pictures that show more of it. By the way pineywood my hydraulics are working great! The clamp and back stops being powered have sped things up a lot. The 6.5 hp gas engine runs the pump very well.

[york]

https://www.youtube.com/watch?v=nQhExWJrirw

[D6c]

I have an '87 LT40 that I'm doing a number of mods to, and the hydraulic tensioner is one of the things I'm considering.  I did talk to WM a little about it and they seemed to think it could be done fairly easily.
Would be very interested to see how it goes if you decide to do it.

[Ben Cut-wright]

I've not done any band stretch measurements or replaced the spring. I have made sure that everything has been squared up as stated in the manual. I thought I had it pretty well under control, but did a job last week cutting some fir that was pretty dry. I ran 4* blades and it seemed like 8-10' into the cut it would dip or dive following the grain or going around knots. I'm pressure washing the logs so,they are clean and change blades regularly. I'm running straight water on the blade, but the dripper gets plugged with sawdust quite often. Could it be that my blades are getting hot and either changing the tension or flexing and changing the set on the teeth?

Thinking it would be wise to find the cause of your complaint before buying parts that may or may not correct the problem.  Not trying to discourage you buying any component you desire.  The springs do become fatigued, a new one is cheap.  Even with a new spring or a hydraulically tensioned upgrade, the band should be measured for more exact tension. 

If you suspect the band is getting hot, stop and examine it at the moment when the cut becomes unstable.  If the band is hot, if your adjustment indicates tension is less, if the band has become coated, if your "dripper" is plugged,  then you have facts you can work with.     

[Crossroads]

I've not done any band stretch measurements or replaced the spring. I have made sure that everything has been squared up as stated in the manual. I thought I had it pretty well under control, but did a job last week cutting some fir that was pretty dry. I ran 4* blades and it seemed like 8-10' into the cut it would dip or dive following the grain or going around knots. I'm pressure washing the logs so,they are clean and change blades regularly. I'm running straight water on the blade, but the dripper gets plugged with sawdust quite often. Could it be that my blades are getting hot and either changing the tension or flexing and changing the set on the teeth?

Thinking it would be wise to find the cause of your complaint before buying parts that may or may not correct the problem.  Not trying to discourage you buying any component you desire.  The springs do become fatigued, a new one is cheap.  Even with a new spring or a hydraulically tensioned upgrade, the band should be measured for more exact tension. 

If you suspect the band is getting hot, stop and examine it at the moment when the cut becomes unstable.  If the band is hot, if your adjustment indicates tension is less, if the band has become coated, if your "dripper" is plugged,  then you have facts you can work with.   

I totally agree, I guess that's why I've asked the questions so, I can learn what I don't know. I'll definitely do some measuring next time I run it. I don't have one of the fancy clamp on dial indicators like what's pictured above, but I have a digital caliper that I can clamp on like I saw in arnold113 gallery. Also, I'm going to add a pump to my watering system so, I can keep a consistent amount of fluids on the blade. The blade tensioner indicator is pretty crude so, measuring will definitely be a  lot better. I guess the next question is, how much stretch do I want? Thank you

[pineywoods]

Unfortunately there will be no updates to the arnold113 tensioner. Arnold passed away suddenly a couple of months ago. From his pics and personal conversations, it looks like a fairly simple deal. A cheap hydraulic floor jack and a 3000 psi pressure gauge is all that.s needed.

[Kbeitz]

Unfortunately there will be no updates to the arnold113 tensioner. Arnold passed away suddenly a couple of months ago. From his pics and personal conversations, it looks like a fairly simple deal. A cheap hydraulic floor jack and a 3000 psi pressure gauge is all that.s needed.

But how does someone know where to put the pressure gauge ?

[pineywoods]

Unfortunately there will be no updates to the arnold113 tensioner. Arnold passed away suddenly a couple of months ago. From his pics and personal conversations, it looks like a fairly simple deal. A cheap hydraulic floor jack and a 3000 psi pressure gauge is all that.s needed.

But how does someone know where to put the pressure gauge ?

S W A G  ;D If you mess up, can always plug the hole and try someplace else  :
Actually anyplace that taps into the base of the cylinder should work...

[Crossroads]

While searching for the picture I saw where Arnold113 had passed, that's to bad, he seemed quite creative. I'm going to measure the stretch this afternoon, how much stretch should be my target? In the first picture of a gauge above, I see the markers are at .031" is that the right amount of stretch? Thank you

[Ben Cut-wright]

While searching for the picture I saw where Arnold113 had passed, that's to bad, he seemed quite creative. I'm going to measure the stretch this afternoon, how much stretch should be my target? In the first picture of a gauge above, I see the markers are at .031" is that the right amount of stretch? Thank you

Looks like he lived in the River Valley, just over the hill from me.  Wish I had known. 

This link should help you measure applied tension.   

https://forestryforum.com/board/index.php/topic,7923.0.html

[Magicman]

Arnold113 was a very talented man and also a very Special Friend.


 
Pictured here showing Pat his sawmill's homemade setworks.

[Crossroads]

I'm
Sorry for your loss magicman

[Magicman]

Thanks but it was actually a Forestry Forum loss because he readily shared his expertise. 

[Crossroads]

Okay, so I clamped a caliper to my blade then ran it up to the tension where I've been running it. Not even slightly close! It was .0005", the spring is apparently worn out, I basically had to bottom it out to get to .005" of stretch. I'm going to be doing a job tomorrow so, I'll crank it up and see if it's an improvement.

[pineywoods]

Thanks but it was actually a Forestry Forum loss because he readily shared his expertise.

Arnold offered me the drawings and software for his home-made setworks..I thought I didn't have time to purse it, now I wish I had...

[Crossroads]

Thanks but it was actually a Forestry Forum loss because he readily shared his expertise.

Arnold offered me the drawings and software for his home-made setworks..I thought I didn't have time to purse it, now I wish I had...

I saw that he had your clamp on his mill, where he had 3 holes griped in the arm, was that so he could change the reach on it. Or was he searching for the best spot? The way mine ended up, I'm limited to about a 28" log, but that's not such a bad thing.

[pineywoods]

Yeah, them 3 holes are there because he took pics of mine and copied everything including my uh-oh's.  : That setworks he had developed is more than a normal setworks, it is a complete automation system, saws boards with no human intervention.

[Ben Cut-wright]

Okay, so I clamped a caliper to my blade then ran it up to the tension where I've been running it. Not even slightly close! It was .0005", the spring is apparently worn out, I basically had to bottom it out to get to .005" of stretch. I'm going to be doing a job tomorrow so, I'll crank it up and see if it's an improvement.

There 'ya go.  Easy and quick to measure tension no matter how it is applied.  A worn out spring may not 'react' properly but it should be good enough for your test run. 

[Magicman]

When Arnold and his wife visited us December 21st, he was excited that he had just sawed his first portable job.  He died ~two weeks later.


 
His sawmill is/was for sale.

[Pabene]

About blade tension.

I have noticed that the blade manufactures recommends a tension for their blades as are close to 10% of the load when it breaks.
To fulfill that recomendation means the blades will be prolonged by the tension force, the same amount, regardless of the blade dimensions. (If the steel quality is of the same sort in the blades body.)
It is important to see that the tension force needed, is different for different blade dimensions.
A tension-meter shows how much the blades are stretched out (prolongs).
To check the tension in the blade works with a caliper as are described here.
To get a higher accuracy in the check you can clamp the end of a longer rod on the free part of the blade. At some distance from the other end of the rod you can clamp a piece of steel, like a nut. Measure the distance from the other end to the nut before and after you have tensioned the blade.
At the recommended tension you will see that the blade is stretched very close to 1mm/1000mm.
To reach such tension in the blade, you need a stiff and stable saw frame. (My log band saw is to week to run the best blades at correct tension.)
In a report from a university here in Sweden, it was stated that a system with a spring was the best to create the tension for the blade. In my opinion hydraulic, weight or screw systems are good, but the best is to have a spring (or an "air pillow" like Wood Mizer) in the end, close to the idle wheel slide.
So, what I want to say here are: I think many saws shows a blade tension as are good for the saw, maybe not the best for the blade. After you have calibrated the gauge in your saw with a blade tension meter you can trust your saw gauge.
If you are going to a thicker and wider blade, be careful to increase the tension to much, so you don't overload your saw.

[Kbeitz]

So I wonder why builders don't use a hydraulic spring (accumulator) ?

[Crossroads]

The jury is in! After running the mill for 10 hours yesterday, there were only a couple of dips dives or waves and they were caused by either a dull blade or the blade guide hitting the edge of the log. Thank you all for the tips, I haven't really had time to study the mill to see how I can adapt Arnold's hyd tensioner, but will be looking at that.

[Pabene]

Screw- Hydraulic- and Weight-system, without any spring, as the last link to the wheel, are stiff and ridgid. There are no forgiving function in such design. When you are going on in a cut and a fragment of bark goes in between the blade and the wheel, it can cause extremly load to the blade in that moment. The saw frame can be deformed or the blade can break. If there is a spring or air-pillow as a transfer part to the wheel slide, the saw will take that like a car passing an obstacle on the road. It is also reccomended to have a "scraper" just in front of the fixt guide-roller to reduce the risk for fragment to go in under the roller and wheel tire.

[Crossroads]

Installed a new tension spring today and it didn't make any remarkable difference. I still have to bottom it out to get .005" of stretch. I can get .004" without bottoming out so, Sunday I'm going to do some sawing and see how it does there. Next step will be to find a small bottle jack and start modifying.

[Kbeitz]

I got thinking about making one for my mill.
I want to use a Hydraulic jack pump off a truck cab lift.



 

[Crossroads]

I got thinking about making one for my mill.
I want to use a Hydraulic jack pump off a truck cab lift.



 

Keep us posted! What s the pressure rating on that pump?

[Magicman]

You may have to position a bottle jack correctly for it to pump horizontally.

[pineywoods]

Bottle jack may not function reliably in a horizontal position..The main problem with them tho is physical size and shape. I greatly appreciate outside the box design, the wm tensioner is just that. 2 aluminum blocks with a one inch hole, 2 short piecs of 1 inch rod, 2 o ring seals and a big bolt..I'd bet Kbeitz could make one from scratch in a few hours. Someone mentioned such a system being rigid and unforgiving..In theory yes, but in actual practice there will always be an air bubble, think the wm designer even thought of that, there is no practical way to get the pump/cylinder completely full of oil..Pure genius..

[ladylake]

 I'd put  a accumulator rated for the pressure or a spring rated for the pressure on my mill..  I've heard enough of the pressure dropping off when the band gets warm to shy away from just a hydraulic tensioner. Mine is getting converted to the heavy spring(already has the heavy spring)  with acme treads soon like the new TK mills, then it should take 4 half turns to tension up.   Steve 

[Kbeitz]

I got thinking about making one for my mill.
I want to use a Hydraulic jack pump off a truck cab lift.



 

Keep us posted! What s the pressure rating on that pump?

I don't know the pressure rating yet. If it's low I will just use a larger dia. cly.

[Crossroads]

I haven't tried it yet,  it would assume a bottle jack would work as long as the handle/pump was on the bottom and operates horizontal?? The spring wood Mizer sent me is green, is there one rated at a higher tension?

[Kbeitz]

What I was hoping to find and I'm still looking for is a screw in
hydraulic pump...

[pineywoods]

K, that is exactly what the wm tensioner is, a screw in hydraulic pump and a displacement type cylinder all in one piece. I have parts explosion in my manual, but it's copyrited, not nice to post it. Find yourself a nearby wmlt40 owner and borrow his manual...The design is pure genius, you could probably build one in a few hours, the seals are off=the shelf stuff and the rods are short pieces of hydraulic cylinder rod..

[Kbeitz]

K, that is exactly what the wm tensioner is, a screw in hydraulic pump and a displacement type cylinder all in one piece. I have parts explosion in my manual, but it's copyrited, not nice to post it. Find yourself a nearby wmlt40 owner and borrow his manual...The design is pure genius, you could probably build one in a few hours, the seals are off=the shelf stuff and the rods are short pieces of hydraulic cylinder rod..

Thanks... I have seen them before on other machines.
I just don't know what they are called or where to buy one.

[Kbeitz]

I found this when googling "hydraulic tensioner"

https://forestryforum.com/board/index.php?topic=12610.20

[Larry]

Here ya go.

https://forestryforum.com/board/index.php?topic=70576.msg1058962#msg1058962

Building the assembly looks to be easy.  Designing the "O" ring groove would be the hardest and slowest part for me.  The groove has to be just right dimension and shape so the "O" ring will have the proper squish to work properly.

Fortunately Parker has put all their technical design documents online.  They even have engineers that might assist if you can catch one in the right mood.

Parker O Ring Handbook

I've been making a few pneumatic assemblies and one low pressure hydraulic assembly with excellent results using their guidelines.

Larry, who much prefers the spring tensioner.

[Ben Cut-wright]

So I wonder why builders don't use a hydraulic spring (accumulator) ?

Hydraulic systems can be, some already are,  provided with "surge absorbers/suppressors", similar to water hammer suppressor valves, somewhat similar to bladder in water tanks.  This device provides X amount of 'give'  in an otherwise rigid fluid system.  This "give" does not come free, there will be a sharp rise in hydraulic pressure when the valve is forced to operate.  Like the spring, imo, better than forcing the rigid components to flex.

[Pabene]

As stated in the report I wrote about, It is the quick forgiving action you are looking for. If you have to transfer the wheel slide movment, (to "swallow" a bark passage between the wheel and the blade) by an oil flow through a pipe in to the bladder, you are lost. It is a to stiff and slow system. A spring or air filled rubber pillow, close to the slide is the right way. I think also the homebuild saws with wheel from cars or motorcycles, as have air filled tires, take care of this kind of problem already in the wheel tire.
The force you need to create the blade tensioning can be convinient to do by a hydraulic system but if the saw has ridgid wheels you need a spring to save your blades.

[Crossroads]

As stated in the report I wrote about, It is the quick forgiving action you are looking for. If you have to transfer the wheel slide movment, (to "swallow" a bark passage between the wheel and the blade) by an oil flow through a pipe in to the bladder, you are lost. It is a to stiff and slow system. A spring or air filled rubber pillow, close to the slide is the right way. I think also the homebuild saws with wheel from cars or motorcycles, as have air filled tires, take care of this kind of problem already in the wheel tire.
The force you need to create the blade tensioning can be convinient to do by a hydraulic system but if the saw has ridgid wheels you need a spring to save your blades.

I believe I have proven your theory correct, although on a 1985 machine, then blade may no be the weakest link. I mentioned earlier about running the spring bottomed out. I did that for a day, but started hearing a hearing getting rough so, I started bottoming it out , then backing off one revolution. I started a job on Monday and by 2:30 the pillow block bearing on the wheel side of the idle wheel sounded so bad, I shut down and bought 2 new 1 7/16" bearings based on the parts list in my manual. Took the assembly home and removed the bad old bearings, cleaned up the shaft and discovered that on the early lt30, the shaft and bearings are 1 1/4". No problems, I was at the hearing shop early Tuesday morning and traded the wrong ones for the right ones and put everything back together on the job site. Made about 6 cuts and everything was sounding good, them boom the blade came off about 7' into an 8' cut. After 3 attempts to put the blade back on and line it up failed, I went looking for another problem. Low and behold the drive side bearings had failed. I believe the damage was done on the short time I ran it bottomed out. The drive side is kind of a pain to change out and the next 2 bearings had to be ordered and won't be here until Thursday.

[Ben Cut-wright]

"I believe the damage was done on the short time I ran it bottomed out. "

Testing with the spring completely coil-bound, rigid, seemed to provide enough tension to resolve your cut complaint.  Perhaps these bearings were near the end of their lives and the extra strain exceeded their last limits? 

There must be some cause/fault if the new spring had to be bottomed out to attain proper tension.  Bad bearings alone would necessitate so great a dimensional change, (distance between axle centers),  that this fault would be impossible to overlook, imo.     

[Kbeitz]

You can buy pillow block bearings with a wide inner ring.
It's a much stronger bearing if you have the room for it.

https://www.thebigbearingstore.com/m2000-series-1/

[Crossroads]

Ben, it's very possible the bearings were at the end of their life cycle, I believe they are original. Until the major failure, the wear would have only been a few thousands and wouldn't make any substantial enter to center differences. I could be wrong, but there is plenty of adjustment to compress the spring and as long as the spring is compressed, the tension should be there regardless of the center to center distance.

K, I've already got the new bearings on order. I have access to a machine shop and will probably make new 1 7/16" shafts for next time. I may make the shafts stepped in order to use the larger bearings, yet not have to replace the sheaves and brake. I will check into the heavy duty 1 1/4" bearings too when I'm not on a timeline trying to finish a job.

[Ben Cut-wright]

You are correct about center to center differences.  I did not do a very good job expressing myself regarding that matter.  Should have constructed my paragraphs more sensibly.  I actually thought you were giving the bad bearings some blame for having to compress the spring past its useful range.  Thanks for your reply and I hope our dialectic will help resolve your problem-s.

Those bad bearings could be a huge contributor to your poor cut quality.  But....that still does not answer why the spring has to be compressed so drastically.  Replaced my tension spring maybe 6 times over several years.  Never once because a spring had bottomed out.  Only one broke, the rest were simply maintenance items, replaced because 'springs fatigue and do not provide exact performance'. 

Not being critical of your skills in any way, is there any chance the (recently learned measuring procedure--converting stretch to tension) might have any errors?  I use this same method to determine tension so I know there are potentials for errors. Properly set up, it is not too difficult to expect fairly exact repeatable results. You didn't say this but if all or most of your tension shows up at the bottom of the spring compression, the spring does not behave as a spring anymore.  When the new spring behaved pretty much the same as the old spring, it was apparent there was more to this.   

[Crossroads]

Hi Ben, sorry for the confusion. I agree, the bearings could certainly be part of my cut problem, I just replace my guide rollers today as well. I'm pretty confident in my ability to read the measurement, however there could. S flaws in my process lol. I'm clamping it at 6" then tighten just to the point that there is no slack in the band, then zero the caliper and start cranking down on the tension.

[Crossroads]

Just got the mill put back together, checked head tilt, set deflection and leveled the blade. I still had the cant on the mill that I was cutting when it came apart so, I went ahead and cut it up. All is well! Now I just have to wait for days off to go finish the job I started last week.

[Ben Cut-wright]

All is well!

What was the precise fault which necessitated the extra spring pressure?

[Crossroads]

All is well!

What was the precise fault which necessitated the extra spring pressure?

I was getting wavy cuts, then I figured out that I wasn't running enough tension

[Pabene]

My English isn't good enough to explain but here is a try. To check the blade tension with higher accuracy you can do it this way: Take a flat bar 40" long, lay it on the blade upper part (or on the lower if the blade guides are taken out). Clamp the left end of the bar to the blade. Clamp a nut (or similary) on the blade, about an Inch from the right end of the bar. Now you can use a Caliper to measure the distance from the right end of the bar to the nut. With this set up you can measure the blades prolonging over a longer distance. I have learn that the prolonging in the blade, by the suitable tension force, would be one mm for 1000 mm length. In this case you would see a difference on the caliper of 0,040" between "zero tension" and "max tension". In my oppinion it is a safer and more accurat method. Remember the blademanufacture has his recommendation and the saw manufacture has his own recommendation for the tensioning, it is not always the same.

[Crossroads]

What I did today was to clamp the caliper to the blade at 6" zero, then tightened the hand until the spring bottoms out. This gave me .0048" stretch, then I backed the tension off on full revaluation, this brought my stretch down to .0043" of stretch and it seemed to cut well. Well until I hit several strands of wire that had grown into the seccoia that I was turning into 1x6" fence boards:(