setting proper blade tension?

[ray299]

I know tension is important,but how to measure it besides "feeling"?
I have a 1.5" wide, 194" long blade on 15" car tires for wheels. Any rule of thumb for big blades like this?
Just have to make my lub system for the blade and its testing time :-)

[Ox]

You can't get a whole lot of tension with car/trailer tires anyways.  Don't go too much more pressure than what's max on the tire sidewall and eventually the blade tension will overcome the tires outward pressure and the tires will start caving in.  I'd consider that your max tension.  You'll rely on your blade guides more than tension for straight cuts.  Keep a sharp, well set blade on and she'll cut straight.  Good luck!

[Den-Den]

My mill uses tires (195-75R14), I run ~40 psi in them.  I have a hyd cylinder that applies the tension (with hand pump), I pump it up to 2000 psi and then lock in that tension with a threaded rod before releasing the hyd pressure.  Any more pressure causes me tracking problems.  I have not yet broken a blade.
My suggestion is to come up with a repeatable method of applying tension (might be as simple as a torque wrench turning a threaded rod) and then use trial and error to determine how much tension you can apply and still be able to adjust the tracking correctly.  Using the same tension each time avoids having to adjust tracking after each blade change .

[Kbeitz]

You can buy one of these if you want to be right on...



 

[ray299]

looks like a dial indicator in a jig. I could make one of those... but how does it work? lol
I'll have to look for more info on it...

[Kbeitz]

looks like a dial indicator in a jig. I could make one of those... but how does it work? lol
I'll have to look for more info on it...

It's a jig made just for the job of tensioning the blade.

https://www.toolcenter.com/62126.html

[warren46]

You do not need a jig.  Take a 6" dial  calipers and extend it to just under 6".  Zero the calipers.  Clamp both ends of the calipers to your band when it is not under tension so that you can measure the strain (stretch) that occurs between the jaws of the calipers.  Tension your band until the caliper reads .005".  Now note the compression of the tension spring or the hydraulic pressure or the torque on the tensioning rod or what ever your mill uses to get repeat proper tension in the band. 

[ray299]

You do not need a jig.  Take a 6" dial  calipers and extend it to just under 6".  Zero the calipers.  Clamp both ends of the calipers to your band when it is not under tension so that you can measure the strain (stretch) that occurs between the jaws of the calipers.  Tension your band until the caliper reads .005".  Now note the compression of the tension spring or the hydraulic pressure or the torque on the tensioning rod or what ever your mill uses to get repeat proper tension in the band.

Awesome. I'll give it a shot and see how it cuts. Should be done with the lub system today... Then its final inspection and test!

[ray299]

You do not need a jig.  Take a 6" dial  calipers and extend it to just under 6".  Zero the calipers.  Clamp both ends of the calipers to your band when it is not under tension so that you can measure the strain (stretch) that occurs between the jaws of the calipers.  Tension your band until the caliper reads .005".  Now note the compression of the tension spring or the hydraulic pressure or the torque on the tensioning rod or what ever your mill uses to get repeat proper tension in the band.

I tried this method just now.. but I'm afraid to tighten it any further. I feel like the threads may strip. I'm at the point of using two hands with a wrench to tighten it. So far I have moved the dial .003... How much tension are these blades normally under? Seems like an aweful lot trying to tighten this.... just afraid of tightening it too far... Check out my set up...
I think the way it works is pretty self explanatory, right? Wondering if I need a hardened threaded rod instead of this one I put together...

 

 

[Magicman]

Don't be concerned about over-tensioning the blade with that setup.

[Kbeitz]

You do not need a jig.  Take a 6" dial  calipers and extend it to just under 6".  Zero the calipers.  Clamp both ends of the calipers to your band when it is not under tension so that you can measure the strain (stretch) that occurs between the jaws of the calipers.  Tension your band until the caliper reads .005".  Now note the compression of the tension spring or the hydraulic pressure or the torque on the tensioning rod or what ever your mill uses to get repeat proper tension in the band.

I tried this method just now.. but I'm afraid to tighten it any further. I feel like the threads may strip. I'm at the point of using two hands with a wrench to tighten it. So far I have moved the dial .003... How much tension are these blades normally under? Seems like an aweful lot trying to tighten this.... just afraid of tightening it too far... Check out my set up...
I think the way it works is pretty self explanatory, right? Wondering if I need a hardened threaded rod instead of this one I put together...

 

I use a long nut so I dont strip anything...



 

[Rougespear]

For your reference: my 1" cylinder hydraulic system properly tensions the band at about 1800-2000psi if I remember right (I need to redo the test and check as it's been awhile and I can't fully remember).  However, I do remember also thinking to myself: "wow, this sure seems like a lot of pressure".  I suppose this is why 1.5" and larger bandwheel shafts are preferable!  Here is an older photo of my setup, but it's fundamentally the same:



I have read about the interwebbs that getting proper tension with the tire bandwheels is not always possible for various reasons.