Hydraulic Tensioner

[jrokusek]

Still slowly working on my homemade bandmill.  I was going to tension the blade with a threaded rod.  I think I read here or somewhere else that may not be the best option since the blade heats up and stretches and you can loose some of your tension that way.

Someone mentioned to me that using a hydraulic tensioner may be the way to go.  Specifically, using a cylinder from a hydraulic jack may work.  I'm not sure if that would be any better or not.  I'm guessing that hydraulic tensioners on bandmills work differently than a simple hydraulic cylinder.  Now before I grab my grinder and cut out the hydraulic cylinder from my floor jack.....can someone enlighten me?

Jim

[flip]

I am using a "mini" ram from Northern Hydraulics ($20)?  and a master cylinder from Napa (single line rebuilt $25) I can make up to 3500psi on my blade if needed.  Kinda like you, I'm still in the building phase of my mill but this tensioner works like a charm ;)  I wish I knew how to post pics :'( >:(

[Buzz-sawyer]

flip

Go to the home button then click on Behind the Forum.look for a post Dang started I put pics in there to show ya how....look for how to post pics

[jrokusek]

I am using a "mini" ram from Northern Hydraulics ($20)?  and a master cylinder from Napa (single line rebuilt $25) I can make up to 3500psi on my blade if needed.  Kinda like you, I'm still in the building phase of my mill but this tensioner works like a charm ;)  I wish I knew how to post pics :'( >:(

Do you use the master cylinder to pump up the hydraulic ram or is is just for holding the fluid?  I guess I'm asking if you use a Hydraulic Ram Pump or just the master cylinder alone.   Do you have a guage?  Is it obvious I don't know a great deal about hydraulics?

Jim

[slowzuki]

I suspect he uses the master cyl to pressurize the other cylinder.   I think that is a great idea as opposed to my big honking lever pump.  I could just have a threaded handle push on the master cylinder to pressurize my little tensioner :P.

[flip]

Bingo!  I have a threaded rod that pumps up the cylinder and keeps tension on the ram.  You have to be careful not to use oil because it will damage the MC seals and no brake fluid because it will take out the seals in the ram--Silicone at NAPA.  I have a guage to tell me pressure, but I will have to move stuff around now that I have guards on, dang! >:(

[slowzuki]

Ya know once I had a little incident out in da woods with a loss of brake fluid and ended up using ATF to get back home... I wonder what the seals look like now?

Bingo!  I have a threaded rod that pumps up the cylinder and keeps tension on the ram.  You have to be careful not to use oil because it will damage the MC seals and no brake fluid because it will take out the seals in the ram--Silicone at NAPA.  I have a guage to tell me pressure, but I will have to move stuff around now that I have guards on, dang! >:(

[flip]

Here goes...

OK well I give up.  If you want a couple of pics. of how my hydro. system is set up send me your email address, too much trouble to post a pic here, sorry.

flip

[jrokusek]

Ya know once I had a little incident out in da woods with a loss of brake fluid and ended up using ATF to get back home... I wonder what the seals look like now?

In my youth I accidentally put power steering fluid in the master cylinder.  BAD DEAL!  All the rubber seals swelled and all needed to be replaced and the system flushed.  Had to rebuild each wheel cylinder (slave cylinder) also.

Jim

[mike_van]

On my mill, I use a large die spring I bought from Mcmaster-Carr. I can't remember off hand the tension, but a 5/8" bolt goes through it, it's about an 1 1/4 in dia.  When it compresses x amount, it gives x amount of force.  Of course, always back it off when through sawing. Been on there 10 years anyway.

[flip]

OK I have the pictures in my gallery now what?  It says I can't post them because they are in JPEG form.

[Furby]

Real close!
Go to your gallery and click on the pick you want.
After it opens in a new window, look for the line: Click to copy photo insertion code
Just click on the words in that line and then go to your post and hit "paste".
It will copy the code, hit "preview" to see the pic.

[Tom]

clicking on your picture will give you this image.
clicking on the words "click to copy photo insertion code" will put the highlighted line (URL) on your notepad.

go to your update window and "paste" where you want the picture.  You can also use Cntrl V to paste.

When you do a preview or post the message, the picture will appear in the post.

[flip]

DOES DAT WORK?

[D._Frederick]

Don't forget to measure the diameter of your hydraulic cylinder so you can figure the force you are applying to the saw blade.

[jrokusek]

OK.  I now understand the basic concept. Does a hydraulic cylinder really have an advantage over a threaded rod?  It would seem that both share the same limitations - can't adjust for band stretch.  I guess you could glance down at the pressure guage on a hydraulic system and see what's happening.

I think I'm still going to use the screw tension method and adjust it by using a caliper like on this thread:  https://forestryforum.com/board/index.php?topic=7923.0       Probably not a perfect system but I'm kind of considering this a "prototype" sawmill anyway.   

Thanks for all the help!
Jim

[D._Frederick]

J-,

If you plan on doing much sawing and need to change a lot of blades, the hydrualic tensioning will save a lot of time. Unless your blades are all the same exact length, you will need to dig out your calibers everytime you change blades.

[mike_van]

photo [I hope] of the blade tension spring I use. It may be too small to see well, if anyone is really interested, email me & i'll send a full size one. 

[mike_van]

My error on the source for the spring [funny how the memory fades]  It came from Travers Tool Co.  in Flushing N.Y.  # 79-201-036   it's 1 1/4" dia with a 5/8" bore.  load in pounds is 1190 & the deflection is shown as 1.57 in.  When I first made this mill up, I had a solid bolt to tighten.  I did  break quite a few blades.  Much better with the spring.   My Travers catalog is so old, there is no web site listed on it!!!!!!So, i've been sawing pre dotcom. :D

[dail_h]

   The abvantage of spring,and or hydraulic,is that as your blade heats and streches,they both tend to maintain a more uniform tension. Also if a chunk of bark or somthing goes  'round the wheel,there's some give.Y'all already knew that,I'm sure. My Norwood mill uses a spring,wit a tension mark on the frame-ok,but I don't know how much pressure I'm putting on the band. Ahydraulic cylinder and guage would give you a way to keep optim tension all the time. You'de just have to do the math

[Rockn H]

One reason I would have to go with a hydraulic gauge, or some type of gauge that would show your band tension constantly. Maybe a manual tension gauge that you could attach you tensioning bolt to.  I know Grainger had some .  That way you can monitor the temp of your blade while you cut.  If the pressure drops you know your blade is getting hot so you can make corrections to your sawing right then.  Heat will dull a blade quick.

[countrysaw]

just a thougt,  has anyone ever thought of getting an accumulator to hold hyd. pressure, so that when the blade gets hot and "stretches" you would hold a constant pressure on the blade?  we have had good luck with accumulators in varying load conditions, where the force applied has to stay the same.  Pretty simple to use too, to tune the pressure, just fill with fluid, attach a valve to the line, and screw a gauge into the end of it, and figure out what pressure the cyl needs for the blade, and take it to a shop and have it filled with dry nitrogen, and open the valve and have them fill until it is at the pressure you need, this should avoid all of the extra pumping and fine tuning.  i looked around and found a small one too
http://www.surpluscenter.com/item.asp?UID=2005061104364921&item=9-6127&catname=hydraulic
you will still need a pump and gauges, and i would reccomend the valve on the tank so you can releive pressure and stop leakdown after done sawing

zach

[sprucebunny]

Here's a picture of one part of the hydraulic tensioner on a Champion sawmill. I don't know how the other end works....yet ;D

[Buzz-sawyer]

Hey Spruce
Do tell some more about that hydraulic jack/tensioner........ is the gauge mounted in the lift? Did they drill and tap a seperate output, does the jack still go up?
Buzz

[sprucebunny]

Buzz    I don't think anything goes up...it looks like they tapped the top of an ordinary bottle jack. You can see the T fitting and the hose to the adjuster coming out.
I know that pictures help me think about things and I thought a picture might help someone else ;D

[Buzz-sawyer]

Yep...more ideas=more projects :D

[Left_Coast_Rich]

The only real grip I have about my WM is the blade tensioner  It seems like I do the btdance way to often for the amount of wood that gets cut.  Cooks saws seems to have a good system for keeping the blade tight.  If I remember correctly theirs is  tensioned by a hinged spring and controlled by a mark on the hinge.  Set the pressure and the spring will keep it close to that level during the temp changes of cutting.  I was impressed.  Don't know if it worked, but I bet it is better than what I have.  LC Rich

[Kirk_Allen]

LCR -  I would bet you may have other issues going on that you may not have yet identified if your having to adjust your tension a lot.

When I first started sawing I thought the same thing and then after lots of expert advice from this forum I found several things wrong that was causing my problems.

The first was not enough set in the blade, which caused sawdust to rub on the blade and get hot.  As it got hot the blade expanded and the tension dropped. 

Another was rust build up on the crome cylinder causing it to hang. If I tapped on the assembly it would break free.  Cleaned and polished the cylender and all was good.

Sawing to slow!  I was afraid to go fast early on.  Now I cant go fast enough ;D

Sawing logs that were dead standing for several years.  They were much dryer and tougher to cut.  More lube cured that problem.

Sawdust build up on the belts.  If you have build up and adjust to a proper tension you will see the tension drop when that sawdust comes off the belt.  I whipe my belts off every blade change and turn them around every other blade change.

There may be a few other things but these are the ones that I have experienced.

I rarely have to touch my tension now!  8) 8)

[Larry]

Broke down last night and thought of this thread when I pulled the tension gadget off this morning.





As the "T" handle is tightened on the bolt it pulls the band tight (the cylinder fits into a bulkhead on the mill) and compress's a ram into the cylinder.  A gauge displays the pressure.

Quite simple tension device...reliable, accurate, and easy to use.  This is the first attention it has had in eleven years...gonna get two new "O" rings.

Kasco would sell ya one iffen your really interested.

[jrokusek]

I like it.  I like it a lot.  Is this the same place?  http://www.kascomfg.com/

I'd like to contact them and see what they get for this sucker...but what is the name of this tensioning widget?  Is it just called a hydraulic tensioner? 

Thank you for the info!

Jim

[Larry]

Thats the place and your right on the name to...hydraulic tensioner.  Hope the price is within reason.

[Rougespear]

I realize this thread is old, but there are some great ideas here I'd like to visit.  Given I've had problems with my conventional-styled porta power hand pump to actuate a hydraulic ram for blade tension, I'm considering other ideas.  The bottle jack idea in this thread (mentioned at the top of this page) peaks my interest, but not as much as the screw-type job forum member Larry posted just above.

I really like this idea.  It looks like it could be made from a portapower ram by cutting off the end of the ram and using the seal/plunger assembly.  I like the idea of using the screw to tighten the assembly (by compressing oil in one cylinder with a screw, the cylinder at the other end would actuate and tension the blade).  However, my brain is stuck on how to set up the screw device.  Has anyone else done something like this as a homebrew, or know of anywhere online its been done?  Can someone offer some suggestions on how I could set up the screw to compress the cylinder?  I have welders and such if needed.

Thanks folks!

[bandmiller2]

Screw shaft and big spring, sometimes simple is best. A lot of big springs around farm machinery and their dealers. Frank C.

[pineywoods]

You need to visit a woodmizer lt40 and look at the hydraulic tensioner. Couldn't be any simpler, would be easy to fab one. The pump and ram is all one piece. (well 2 pieces bolted together). WM might even sell you one, wouldn't hurt to ask..
Otherwise..
Bottle jacks don't work too well in the horizontal position. The pump and ram out of a cheap floor jack would work nicely. Drill and tap a hole to accept a 2500 psi pressure gauge. That will save you a lot of grief from tension changes while sawing. You might pm member arnold113. He might send you a pic of his.

[caver]

The device looks like a hydraulic knockout punch for putting holes in electrical panels.
Greenlee and others make such a device. Probably big $$$ if the Greenlee name is on it.

[ladylake]

Do hydraulic tensioners have any give like spring tensioners do.   Steve

[bandmiller2]

Steve technically no, but they all have some spring due to even the heavy duty frames flexing. Belted bandwheels insert some give into the operation. I have never operated a steel wheel bandmill but there I think they would be aided by a heavy spring or polymer or accumulator to factor in some "give"  to compensate for heat in the band or running over a chip with the band. Frank C.

[MSSawmill]

Thought I had a good picture of it, but I don't... We used the cylinder from a cheap floor jack. It has worked really well so far. I have a gauge to put on it, but haven't installed it yet. This replaced a threaded rod tensioner on the old design. The cylinder head allowed us to get a lot more tension with a lot less effort, and it has made blade changes faster. I wouldn't go back now...

[4x4American]

   The abvantage of spring,and or hydraulic,is that as your blade heats and streches,they both tend to maintain a more uniform tension. Also if a chunk of bark or somthing goes  'round the wheel,there's some give.Y'all already knew that,I'm sure. My Norwood mill uses a spring,wit a tension mark on the frame-ok,but I don't know how much pressure I'm putting on the band. Ahydraulic cylinder and guage would give you a way to keep optim tension all the time. You'de just have to do the math

What he said!

I would go with a spring too.

[ladylake]

If using hydraulic use some sort of a cushion like a accumulator as Frank mentioned (Surplus center might have one) or a have the cylinder push on a heavy spring.    The spring tensioner on the TK 2000 tension's up easy and fast.   Steve

[xlogger]

Larry on #28 the pics you showed, did you just add on the line and new gauge on your 2000? I've gone threw two gauges and just measure the spring now. I set it at about 1 7/8". What does your gauge say if you set it near that? 4X4 or anyone with a 2000 can probably answer that question. I break more blades than I should when cutting cedar. I get too much loose bark off the cedar going around the band wheel is what I think the problem is.

[Rougespear]

Right, so I'm hearing you all loud and clear on the spring thing.  Seeing how I'm readdressing this issue of how to tension the blade, let me see if I can work in the spring idea. 

I will begin by saying that I will be staying with the hydraulic ram tension method.  At this point in time, my plan is to buy another porta power ram, unscrew the end nut and remove the cylinder, cut the cylinder rod a few inches shorter, reassemble, weld a piece of 1/2" plate to the end cap screw, tap the plate with 1/2" x 20NF, and thread in a bolt so that as the bolt is threaded in further, it engages with the cylinder rod, thus compressing the ram and developing pressure in the system.  How does that sound to all?  The below photo is an OLD photo, but nothing as changed in the fabrication of the structure.



Therefore, I'd like to install a die spring at the blade tension ram end of the system (i.e. in the saw head framework).  As seen in the above picture, when the tension ram is fully retracted there is about 2" between it and the sawhead slider (i.e. extending the tension ram approx. 2" tensions the blade).  So I have an area of about 2.5" around and 2" long that I could fit in a spring here.  Does all that make sense?

However, I know NOTHING about die springs.  I understand Cooks uses an 850lb spring... but I dont see them rated by poundage, but more about their component size.  Can anyone shed some light on what kind of spring I should use?  (I like pictures to conceptualize stuff).

Thanks

[Larry]

Larry on #28 the pics you showed, did you just add on the line and new gauge on your 2000? I've gone threw two gauges and just measure the spring now. I set it at about 1 7/8". What does your gauge say if you set it near that? 4X4 or anyone with a 2000 can probably answer that question. I break more blades than I should when cutting cedar. I get too much loose bark off the cedar going around the band wheel is what I think the problem is.

That picture is an old one of the gauge on my Kasco which is a different setup.  They do look similar.

There is no way a gauge can survive on a TK.  They should just quit installing them or do it right.  I measure 1 7/8" like you and it works well.

I do like the spring more than a hydraulic gauge.  A airbag like some use on industrial mills seems like it is the ultimate.

[4x4American]

How'd your gauges break?  Of natural causes?

[4x4American]

Larry on #28 the pics you showed, did you just add on the line and new gauge on your 2000? I've gone threw two gauges and just measure the spring now. I set it at about 1 7/8". What does your gauge say if you set it near that? 4X4 or anyone with a 2000 can probably answer that question. I break more blades than I should when cutting cedar. I get too much loose bark off the cedar going around the band wheel is what I think the problem is.

I'll go measure after lunch n get back to ya.

[Magicman]

You do know that hydraulic gauges are normally filled with glycerine as a dampener to prevent failures? 

[Ga Mtn Man]

There is no way a gauge can survive on a TK.  They should just quit installing them or do it right.  I measure 1 7/8" like you and it works well.

I installed a snubber on the gauge of my TK2000 about a year before I sold the mill and the gauge was still good when I sold it, having survived numerous blade breakages.  Here's a pic:



 

[4x4American]

What's the snubber GMM?  I guess I don't see what it is.

Ricky- when the spring is at 1-7/8" the psi is around 1125.

[Ga Mtn Man]

It's the large brass hexagonal device between the black collar and the gauge.

[bandmiller2]

Usally a snubber is just a small orifice that gives a gauge time to react to large fluctuations and steady the needle. As Majic says sometimes its done with a glycerin filled gauge. Frank C.

[Magicman]

From Paul's picture I would venture to say that his is glycerine filled.   

[Ga Mtn Man]

The TK2000 is notorious for destroying pressure gauges (glycerin filled).  When the blade breaks a pressure shock wave hammers the gauge, which can only handle a few of these events before failing.

Orifices are one type of snubber.  On pressure systems that have rapidly increasing or decreasing pressure spikes, orifices lessen the effects of these energy pulses by blocking the wave energy using restricted flow.  They are recommended in dynamic pressure applications with mild pressure spikes.  The snubber shown in the picture is a piston snubber designed to protect gauges from large pressure spikes.  The primary purpose of filling a pressure gauge with glycerin is to dampen the movement of the dial indicator in applications where vibration or pressure pulsation is an issue.

[xlogger]

Paul, where did you get the snubber from? Also did you put it on after your gauge went out and got a new gauge or used the old one? Ricky

[bandmiller2]

You can use a small needle valve as a snubber , close it and just crack it open, you may have to adjust it several times to get it just right. Frank C.

[Ga Mtn Man]

Paul, where did you get the snubber from? Also did you put it on after your gauge went out and got a new gauge or used the old one? Ricky

I got it off of eBay, NOSHOK #1325, paid about $12 including shipping.  I installed it along with a new gauge after my second gauge failed.

[4x4American]

Wow.  Thanks for the good info.  I've only broken one blade so far.

[Larry]

I got it off of eBay, NOSHOK #1325, paid about $12 including shipping.  I installed it along with a new gauge after my second gauge failed.

That cost is less than all the gauges TK sent me when the mill was in warranty. ???

[4x4American]

Did they warrant the gauge?  I think I'll rig me up a snubber thanks for the tip, GMM