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Tension setting for those with 'economy' mills

Started by beerguy, August 06, 2004, 06:54:51 PM

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beerguy

Gentlemen,

How do the folks (like me) who have to set tension on their blades manually accomplish this? I have a big bolt that pushes the wheel outboard when tightened, and I use a torque wrench to apply the pressure. How much do you tighten a 221" blade? It is a long way between guides, so is 70 ft/lbs out of the question? When working on aircraft rigging, there is a tool to measure tention from the rigging cable.  Any such animal?
Feel free to talk amongst yourselves....

dail_h

   My Norwood has got a spring that you compress ,keeps the tension right when the band streches
World Champion Wildcat Sorter,1999 2002 2004 2005
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music_boy

My 18" "economy" Hudson mill requires 40 to 60 lbs torque. I usually use the 50 to 60 range with good results. The blade is 132 " if that matters.
Hope that helps
Rick
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D._Frederick

Beerguy,

If you want to spend the $$, the big saw companies (Simond ) have a tension measuring device that clamps on to the blade and measure the stretch in the blade with a dial indicator. I thought about buying one for my manual mill, but the cost were about equal to the price of hydrualic components to build a hydrualic tensioning system.

twoodward15

that thing is a tensiometer.  I use one checking the rigging on airplanes as well  (KC-135E models as a matter of fact)  They work quite well.  If you really think you need one, I may be able to dig one up around here.  Let me see what I can find!!!
108 ARW   NKAWTG...N      Jersey Thunder

EZ

My mill also has the screw spring adjustment and in the beginning it was a guessing thing. Then I found out about the fluddering test and it work out well for me.
I put some tension on the blade, start the motor and slowly get the fpm up to max. I then tension the blade until the fludder is gone and turned the tension screw one full turn. After that I shut it down and counted how many turns it took to back the blade off to slack. As for mine it takes 7 turns. I run a 14 ft 6 inch blade. Hope this helps.
EZ

Kirk_Allen

Twoodward15:

I too have used the tensiometers on the C-130 aircraft rigging cables.  It was the same as the one we used on the transient KC-135, C-141- C-5 aircrafts.  

I may be wrong, but I dont think the ones we use on cables is going to be sufficient for band blades.  I would bet a tensiometer for a band blade would be much wider than a cable tensiometer.  It would have to be wide enough and deep enough for the tension device to be applied to the center of the balde width.  

I bet that the brand of those meters are stamped on them somewhere and if so, the company that makes them for cables may have also made them for other applications.  

I no longer have access to a cable tensiometer (Retired AF) but if you do check the brand name and and we could try to contact the company that made it.  If you cant find the company name I may be able to contact some of my friends at Little Rock AFB and get the info.........provided they are back from Iraq.


Gilman

If you want to make a dirt cheap tension gage, you can clamp a 6" dial caliper to your blade.  You can get the correct stress to run your blades from the blade manufacturer.  Open the caliper to 6.000", clamp in place, and then tension your blade until the blade strains the correct amount over over the original 6".  I could help with the calc's if anyone wants to try this.  I'll just need the blade width and thickness and gullet depth.

Duh, I don't need all those dimensions.  :P Strain is strain. Get that dusty old engineering book out engineer boy!  All I need is how many psi the band manufacturer recommends.

The cheapest dial calipers can be found at http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=47257


Only $15.99 for a 6" digital caliper.
WM LT70, WM 40 Super, WM  '89 40HD
Cat throwing champion 1996, 1997, 1999. (retired)

Fla._Deadheader

  OK, guess it's me. How does this work?? Where do you clamp it, and what reading do you get ???

  Lets say that I want 1600 PSI on the blade tension.???
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   First, it is ridiculed;
   Second, it is violently opposed; and
   Third, it is accepted as self-evident.

-- Arthur Schopenhauer (1788-1860)

Gilman

I gave Simonds a quick call and they said their Red Streaks should be stressed 25,000 to 30,000 psi.

Thus:

Stress = E * Strain
25,000 psi = (29,000,000 psi) * Strain
Strain = 0.00086 in/in

Having a distance of 6" gives 6" * 0.00086" = 0.005" deflection.

So, clamp the caliper, opened to 6.000", on your band with zero tension.  Then tension your band until it reads 6.005".  This will give 25,000 psi in the band.

For 30,000 psi your caliper should read 6.006"

Hope this helps,

Gilman
WM LT70, WM 40 Super, WM  '89 40HD
Cat throwing champion 1996, 1997, 1999. (retired)

Gilman

I called Woodmizer this morning and was told I needed to talk to John Storm to find out how many psi their blade should be set at.  Unfortunately he is in meetings this morning.  If anyone gets info from Munks or other band manufactures, please post it here.  I'll do a quick little chart for the group.
WM LT70, WM 40 Super, WM  '89 40HD
Cat throwing champion 1996, 1997, 1999. (retired)

Gilman

Ran outside and did a quick test.  I'm running 0.042" x 1 1/2" bands, but the strain should remain the same no matter what thickness or width.

Mounting the caliper, Don't try to get exactly 6.000", way too difficult, just get it close and then add 0.005" to it.


Band set to Zero tension.


Band tensioned.


Caliper reading after tensioning.  I got 0.0045" of deflections, thus I guess I need to be running in the high red with the 1 1/2" bands.


Hope this helps out.
WM LT70, WM 40 Super, WM  '89 40HD
Cat throwing champion 1996, 1997, 1999. (retired)

beenthere

Gilman
Good method.  and cheap too. (IMO)
Seems one could just clamp the digital caliper to the band at 6 ", and then zero it out at the "untensioned" starting point, and then read the 'stretch' needed when tensioned.

Saves trying to set exactly at 6.0000" to start, and just use the direct reading of 'stretch' needed to get the desired reading.  

south central Wisconsin
It may be that my sole purpose in life is simply to serve as a warning to others

Gilman

That's a good idea, it will also increase your accuracy.
WM LT70, WM 40 Super, WM  '89 40HD
Cat throwing champion 1996, 1997, 1999. (retired)

LeeB

I like it. Thanks for the idea. Now if I could just remeber which blades are which. LeeB
'98 LT40HDD/Lombardini, Case 580L, Cat D4C, JD 3032 tractor, JD 5410 tractor, Husky 346, 372 and 562XP's. Stihl MS180 and MS361, 1998 and 2006 3/4 Ton 5.9 Cummins 4x4's, 1989 Dodge D100 w/ 318, and a 1966 Chevy C60 w/ dump bed.

Fla._Deadheader

  Thanks for the lesson, Gilman. I will try that in reverse next time we go to the camp. 8)
All truth passes through three stages:
   First, it is ridiculed;
   Second, it is violently opposed; and
   Third, it is accepted as self-evident.

-- Arthur Schopenhauer (1788-1860)

beerguy

Thanks, guys. This takes the mystery out of it. My torque wrench has been out of calibration for some time, and I have the tools for this measurement.

highpockets

Gilman,

I found your information on blade tension which was very informative.  I had calculated my needed blade tension and bought a proper die spring when I built then mill some 6 years ago.  Since I have lost my calculations.  I like the dial indicator method, thanks.

Louisiana Country boy
homemade mill, 20 h.p. Honda & 4 h.p. for hydraulics.  8 hydraulic circuits, loads, clamps, rotates, etc.

jrokusek

Maybe I'm thinking of a different thread...but I believe this method was only for those people who had actual bandwheels or sheaves.  I though I remembered reading that it didn't work for guys like me who used trailer tires. 

Jim

isassi

Mike from Mr Sawmill gave Bill instructions on tensioning using 1 revolution on the pull bolt, back off 1 to change, return to original setting. Now I know he said the blades are accurate, but how can they be sure each and every blade is exactly the same length? I think the caliper idea is an easy and effective way to do it.

eagles nest


highpockets

I think the discussion on blade tension is about as wide as it is long.  I am not saying that I am an authority but I have seen things and like to share others ideas. I have built several saws over the past twenty years and I always go to the Lennox engineers for info such as wheel size, spacing, etc.  My first bandmill was in 1999.  At the time I had the proper data and designed accordingly.  Since that time I have lost this data in swapping from a gazillion computers. To me the importance of this thread is that is gives a basis for one to do his own checking of tension versus his idea of his tension. 

I read where this guy says that he has to use xxx ft/lbs of torque, or xx lbs of hydraulic pressure.  For those with homemade or some store bought mills, the design is different such torques, and hyd pressures.   There is a spring out there sold by Danly Die Set,  www,danly.com .  They sent me two catologs with all of their springs in them.  You can get a spring that gives exactyy so much pressure for each 1/10" of compression.  I think MSC Supply carries some of these springs.  The kicker is that one needs to know and calculate the distance from the pivot point of the wheel bracket, center of the axle, and the point the spring is placed.  I believe that this was for a 1 1/2' blade and one needs to find out what one needs for an 1 1/4" blade.   

I have never been around any mills that run rubber tires so I am not sure how this will work for them.  Since I have gotten this mill back in the shop after some years, I have been experimenting with many different things.  There was a thread that mentioned tightening the blade until the flutter came out then thighten a little more.  I think I have found that this is a good way to do it.  I want to compare this tension with a dial indicator. 

Thanks to everyone.  This forum is really good.





Louisiana Country boy
homemade mill, 20 h.p. Honda & 4 h.p. for hydraulics.  8 hydraulic circuits, loads, clamps, rotates, etc.

thecfarm

I guess I really don't know what I'm doing or just DanG lucky.I just tighten the blade until I think it looks good,than take my thumb and push down on the blade and I can tell how tight the blade is in this manner.I run the blade and I make sure it's running smooth,no flutter.I haven't sawed 100,000 bf,but I've sawed quite a lot and this works for me.
Model 6020-20hp Manual Thomas bandsaw,TC40A 4wd 40 hp New Holland tractor, 450 Norse Winch, Heatmor 400 OWB,YCC 1978-79

highpockets

Thecfarm,

It is in what works.  That is kind of what I do. 
Louisiana Country boy
homemade mill, 20 h.p. Honda & 4 h.p. for hydraulics.  8 hydraulic circuits, loads, clamps, rotates, etc.

wiam

thecfarm, that is my gauge on my homemade also.

Will

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