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dynamic or static tension

Started by charles mann, August 04, 2019, 02:26:44 AM

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MAF143

Still sprinkling a little, but the sun is out.

The threads to tension the blade on this mill are 3/4-10  surprised me since everything else is metric.  Hope this helps you out.



Always having a great day!
Husky 357 self ported, MS 250 MM, MS 362  MM, HM-126, Ferguson TO-35, '04 F-250 wood cuttin' truck, splitter, Woodland Mills Grindlux 4000 sharpener, Vogelzang Ponderosa keeping us warm

petefrom bearswamp

Dont know that much about the physics of what has been discussed here.
I crank my WM LT40 till the needle is nearly vertical and saw.
I'm thinking that the V belts on the wheels must take care  of any instant increase in tension due to  a chip or piece of bark engaging the wheels.
Works for me.
I guess the Cooks steel wheels are spring loaded to accomplish the same thing, Is this an accurate assumption?
Kubota 8540 tractor, FEL bucket and forks, Farmi winch
Kubota 900 RTV
Polaris 570 Sportsman ATV
3 Huskies 1 gas Echo 1 cordless Echo vintage Homelite super xl12
57 acres of woodland

charles mann

@MAF143 
thanks, ill take a look see on their site. 
Temple, Tx
Fire Fighting and Heavy Lift Helicopter Mech
Helicopter and Fixed Wing Pilot

Pabene

Petefrombearswamp, You describs the function very good. I have steel wheel in my mill and would like to add a springpackage, unfortunatly it is complicated to do in my mill. I protects my mill by a skraper as acts as a guard against sawdust and bark between blade and wheel.
The reason for me to suggest a longer spring package is that it would give a more linear tension force during the movement from a heated blade or instant pinched bark. That way the blade will survive better. I like bellewille washers as it is a lowcost solution, if you would end up in a too low force you can just rearange the package of washers insted to buy a new expensive toolmaker spring. 
I have experiance from Pilous saw mills with Bellewille washers in the tension system. I have checked the tension on a lot of Pilous mills with my tension meter. The tension are equal, within few percent, from mill to mill. Insted of a torque wrench they use the length of the compressed package as is the reference. It will give you a higher accuracy as the variation in friction in the threads is bypassed.
Woodmizers spring solution with a airfilled rubber ball looks also good, I think it meets all you need.

John Bartley

Quote from: charles mann on August 04, 2019, 02:26:44 AM
granted a hydraulic ram (port-a-power, or short stroke horizontal bottle/floor jack) with a psi gauge could greatly minimize the need for using the tensionmeter, but its 1 more thing to worry about, throwing a temper tantrum and sending very sharp things at very high speeds everywhere. but so could a spring, which is why I'm asking is dynamic would even be a logical method of tensioning.


A hydraulic ram is what tensions my Champion mill.  The ram has a pressure gauge on it, and as long as I keep the pressure close to my optimum number, all works well and has been for eleven years with no shrapnel or other bad things happening.

When I got my mill I learned about band tension, strain vs psi etc.  I then clamped a vernier across the band and tensioned to see what pressure got me the correct strain.  That's the psi that I run ....
cheers
Kioti DK35HSE w/loader & forks
Champion 25hp band mill, 20' bed
Stihl MS361
Stihl 026

JoshNZ

Probably better to go in this thread than my build sorry Charles XD

I only skimmed it sorry if it's been said but how does one go about tapping the cylinder of a jack? I did pull the top off one at home here, the outter wall is not the cylinder wall it is the reservoir and the cylinder is nested inside that. So you would have to drill the wall, and cylinder, tap the cylinder, screw in the output nipple then weld or seal the nipple to the outter wall somehow?

Has Arnold been around here lately I wonder how he did his? Am I on the right track?

Also.. could you force the cylinder to hold a wee pocket of air as a spring/dampening system or are they designed to bleed this out when you let up?

charles mann

@JoshNZ 
I think the drilling of the cylinder was explained in a sub link to a link provided, i think maybe on page 1. Ill look when i get off tonight. Iv got 5 web browsers open, with 3-6 pages per window. You might find it faster in you go the provided link and read through it till another link is posted. Its either in the sec link or another link provided within the sec link. Just gotta read through the stuff like did and stumble across the info. 
Temple, Tx
Fire Fighting and Heavy Lift Helicopter Mech
Helicopter and Fixed Wing Pilot

charles mann

@JoshNZ here are the links i read through. 

Wm spring blade tensioner conversion in Sawmills and Milling

Tensioning method for homemade bandsaw mill in Sawmills and Milling

Hydraulic Tensioner in Sawmills and Milling

after sign through these, plus what others left on my thread, i found the info i was looking for. now i just have build it in a way that will work on my set up.
Temple, Tx
Fire Fighting and Heavy Lift Helicopter Mech
Helicopter and Fixed Wing Pilot

JoshNZ

Are you referring to the post with the gauge tapped in the top of the cylinder? The cylinder is not full of oil in the jack I have here, the seal is at the bottom of it and the top has a threaded 'foot' as a means of taking up slack before you get the jack working which is great if it's used as a jack!

charles mann

Quote from: JoshNZ on August 11, 2019, 05:34:53 PM
Are you referring to the post with the gauge tapped in the top of the cylinder? The cylinder is not full of oil in the jack I have here, the seal is at the bottom of it and the top has a threaded 'foot' as a means of taking up slack before you get the jack working which is great if it's used as a jack!
IDK, i didnt go into depth about the gauge on the jack bc im not going that route. I simply provided additional links that might yield info for you. I did see a gauge on a jack, dont remember which link it was and wasnt going to read through them to find out bc i didnt have the time and i wasnt going that route.
Im sure there is something within those links or links within those links that might be beneficial for your purpose.  
Temple, Tx
Fire Fighting and Heavy Lift Helicopter Mech
Helicopter and Fixed Wing Pilot

charles mann

so, after watching this guy's vid https://www.youtube.com/watch?v=_5HeE_b7IMg  several times, writing the formula down, do ing the math and taking numerous measurements. i came out with 4,096.6 (4,100) pounds of force being exerted on the blade, which I'm sure is about the same amount being exerted on the idle box too. NOW, I'm not sure, but after talking to woodmizer, and their recommendation of 30,000 psi of tension, which equates to 3900 psi on the gage i tee'ed in with on the port-a-power, and using a lenox tension meter, to get the 30,000 psi. am i suppose to do the formula using the manfc. recommended tension psi, or using the psi i got from the measurements i did and the formula, which is 36,000 psi? if using WM recommendations, my spring rating needs to be 3420 pounds. if using the measurements i got of 36,000 from the formula, the spring rating needs to be the 4,096 pounds. I'm thinking getting 1 of each, trying the lower rating first and hope it doesn't come off the wheels or get pushed into the back of the blade guide rollers and break. 

Suggestions? I'm near completion. well, close enough, so i need to kick this mule in the butt and get moving. i can almost taste the sawdust.
Temple, Tx
Fire Fighting and Heavy Lift Helicopter Mech
Helicopter and Fixed Wing Pilot

JoshNZ

You'll def taste sawdust once you get going, no rush for that hah.

Not sure I'm following your setup, might just be me... If you have a pump and gauge measuring the force required and you know you're at the right tension, I'd go with that. I don't know what the spec of a spring is actually measuring, where it starts deforming  or what... I doubt it's linear as it compresses

I'd go on the higher end of spring too, it's not like an auto shock where it will be completely uncompressed until a certain force is exceeded, you'll have spring support by the time you're at tension even if you go way over with the springs spec.

charles mann

Quote from: JoshNZ on September 21, 2020, 01:26:44 AM
You'll def taste sawdust once you get going, no rush for that hah.

Not sure I'm following your setup, might just be me... If you have a pump and gauge measuring the force required and you know you're at the right tension

I'd go on the higher end of spring too, it's not like an auto shock where it will be completely uncompressed until a certain force is exceeded, you'll have spring support by the time you're at tension even if you go way over with the springs spec.
Im wanting a dynamic tensioner to help absorb any shock to the blade/wheel from debris and to help keep tension as the band warms up. For now, im just gonna run with hydraulics, but still be able to bolt on a new bracket to capture either a spring or airbag. 
Temple, Tx
Fire Fighting and Heavy Lift Helicopter Mech
Helicopter and Fixed Wing Pilot

scsmith42

How about a plate with a few die springs?

These are rated for a maximum load of 999 lbs per spring, and they are only 17 bucks apiece.

https://www.travers.com/diemax-xl8482-die-spring/p/79-322-421/

When I built the chain tension system on my slabber, I sandwiched 4 springs between two plates, with a rod running through the springs to keep them aligned.  The combined tension was set for what the chain tension should be.  Worked like a charm and kept the chain properly tensioned as it heated up.



 
Peterson 10" WPF with 65' of track
Smith - Gallagher dedicated slabber
Tom's 3638D Baker band mill
and a mix of log handling heavy equipment.

charles mann

Quote from: scsmith42 on September 21, 2020, 08:32:23 PM
How about a plate with a few die springs?

These are rated for a maximum load of 999 lbs per spring, and they are only 17 bucks apiece.

https://www.travers.com/diemax-xl8482-die-spring/p/79-322-421/
i was looking at tavers. the closest i can find would 4 of these
https://www.travers.com/diemax-xl8482-die-spring/p/79-322-411/  
and 4 of these
https://www.travers.com/diemax-xl8482-die-spring/p/79-242-226/
to cover both weight load requirements. i would just have adjust the stroke by 1/2", which isn't a problem, i have a 5" stroke ram. 
i still have to weld a top plate on my idle box and drill/tap to allow for different dynamic tension aids. i will have to do any and all welding first, before adhering the uhmw sheets to the box. my previous box was extremely stiff to my, especially if i hadn't oiled the saw beam. with a clean beam, dry of any oil, the uhmw made the new box tighter and slicker than owl poop on a hickory limb. 
Temple, Tx
Fire Fighting and Heavy Lift Helicopter Mech
Helicopter and Fixed Wing Pilot

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