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Part 2 - Mechanics of Woodland Mills Sawmill Blade Tension: Measuring Blade Tensile Stress
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- Опубликовано: 11 сен 2021
- In part two of the series, we use a simple method to measure strain (i.e., relative stretch or elongation) and calculate tensile stress in the band blade on a Woodland Mills HM-122. We compare the measured values back to the theoretical estimates from part one and make some comments.
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Here is a link to part 1 of this video series: • Part 1 - Mechanics of ...
There are those who just want to know the "how" of doing something...and then there are those who want to understand the "why" behind the "how'. This kind of detailed, and yet easily understood, illustration of the mechanics of blade tension will be invaluable when it comes to a situation where things are not quite going according to expectations. It will help decide where to go from the "standard" settings to adapt to challenging conditions. I, for one, appreciate this kind of video presentation. You have provided a balanced mix of theoretical and practical to help one understand the topic at hand. Well done!
I too agree that it is always good to see the theory behind recommended practices, Of course it is only useful if it is understood, and you are a super teacher in taking us through these laws of physics and calculations with clear explanations, just enough details so that someone like me, with not much more than high school physics notions, can follow the logic. I am so glad I came across your channel, and I hope that you can find the time to continue for a long time. Thank you Jack.
In any venture both technical and practical information are equally valuable. I look forward to your next uploads because you are not a one song band, you mix it up very well. Well done Sir.
Thank you for the videos!! I wouldn't know where to start. I was able to follow along and you explained it very simply. Thanks again from Northern Wisconsin!!
So Yes, the theory breakdown as it applies to practice is really a value. I would have gone down my own rabbit hole figuring it out, but you saved time for me, as well as shown a simple working setup should I decide to make some measurements or comparisons. I don’t have my mill yet, so this knowledge is being used as advanced wisdom. I’d like to hear how you decide the forward cutting speed as it relates to stress on the blade or other components.
Very interesting video. Bringing back memories from almost 40 years ago when I was in college.
I don't have a mill yet, but it's in my plans.
great video! I have a harbor freight mill which is very similar to the woodland mill and have had problems with blade breakage for years and come to find out using your dial ind. rig I was over tensioning my blade by two or three fold!! keep up the great videos
Appreciate the engineering…I’m 5:35 old school slide rule mechanical engineering setting up a HM-122 Great Job 👍💪🏞
Very interesting and valuable, and it certainly leaves no doubt that you are a qualified mechanical engineer.
I am really glad I subscribed! Mixing theory and practice is the essence of knowledge. You are wise to show both sides. Looking forward to your next video!
Super job. After the 1st video I was looking forward to seeing how closely the empirical data approached the theoretical data. Well done. And as far as voting on whether the technical pieces in the video are appreciated, I'm a retired Mechanical Engineer so for what it's worth, I vote yes.
I have subscribed in hopes of continued referencing to your engineering background and experience, which I regard to be more accurate than generally opinionated suggestions and faster than trial and error type answers and solutions.
I'm an Engineer too, so I like all your videos, especially cause my discipline is Electrical.
I too tend to use the “over thinking” method of things during setup and operations on my homestead. Drives my wife nuts when I use the Pythagorean theorem when laying out her chicken coops or raised garden beds, Haha! But I can’t help it; as a machinist, making things Square and accurate to within Thousandths is just a part of who I am. Certainly slows projects down a bit, but it sure looks good when completed!
Nonetheless, I know this is an older video, but as a new Saw Mill owner, and within a day or two of making my first cut…(had to get the Mill bed square and level😉), I’m curious if you’ve considered the blade tension changing after making a few passes. When heat enters the blade, surely the tension would lessen due to elongation from increased heat. That’s simple metallurgy.
- Have you ever tested tension with heat in the blade?
- if so, what were the results?
I perceive this could even be substantial, and require adjustments to blade tensioning.
Additionally, to ensure blade longevity, it seems one would need to be mindful of blade cooling as well so as not to allow over tensioning. Again, I tend to overthink a bit, but you seem to ponder things similarly, so I figured I ask. Thanks in advance if you find time to answer. I’ve subscribed in hopes of finding additional videos of the same caliber. Have a great day sir.
I too thank you for this video. Understanding anything is always handy when proper operations are desired and questionable results arise.
Great stuff as always, I just sent Northwest Sawyer over here to watch this video.
thanks for your video i think basics are more helpful but this is very useful too most of the math was over my head and like you said diff. blades will change setting there are more than blades than you can count wood mizer has loads of them alone. i have a woodland mills hm-130 max ordered still over 2 months out. i think if you were young and was going to try and make a living milling the big cook's mills would be the way to go. i think you have the best video on mill leveling i will have to re watch it when my mill comes. thank you again take care, be safe and well.
Enjoyed the video. Thanks
Might be a good idea to remove the tensioner handle, spring washers and shims once a year to examine, clean and lube them up. I have replaced many broken or worn out Belleville washers in other applications where they were not up to the designed task. These come in a variety of thicknesses and materials, try a bearing supply house or big online industrial supply.
This video series was outstanding! Even though my band saw mill has not yet arrived, and it is of a different brand, I found this absolutely fascinating! So with that being said, I'm all for this type of video mixed in with the practical hands-on stuff! I appreciate you sharing your years of experience and knowledge. I did want to ask if you, by any chance, had plans available for your sawmill shed and the base you built for the sawmill? Thanks so much! 👍
Thanks. No plans for the shed, it basically just fits the mill plus a few feet of sheltered walk around space on all sides. About 8.5-9' wide and 25-26' long.
The base is custom to the mill rail spacing and footpads, so that will vary with brand/model, but the height is the main benefit that will work for every mill. The lumber base is about 18-20" high and the log sits another 6-8" above that, for a working deck height of 24-28" ballpark. Similar to trailer-mounted mills. That can be customized to taste based on your habits and height, but the important thing is to get the mill up off the ground to save your back.
There are videos on both the shed and base.
@@Lumber_Jack Thanks!
Would a .015 feeler guage be adequate for a set up as yours if you don't have a dial caliper for a 1 inch x .042 blade
So is 25lb. To much i was curious to know. What ft. Lb. Would you recommend on the mill.
Well, all I can say is that what I have been doing (setting thrust bushing flush) equates to ~20 ft-lb on my mill, and it's always worked great. Doesn't mean it's perfect or right, and may not apply to everyone, but I will stick with what works.
20
Does the length from the clamp on the left to the l bracket on the right cone in to play. I went to sleep and misted that part
Does the word land have a spring in the tention screw if so they calculated for the correct spring
Nice video.
I have a question. How do you account for things like the thickness of the blade and the width if you have a different blade? I may have missed it but I don't think I saw you measuring the thickness or the width of the blade and calculating the mass of metal those two measurements would yield.
I've seen the instruction for the Lennox tool. They don't seem to be able to account for those variables either. And yet I am quite certain that if my hunk of metal is thicker and wider it'll take more stress to get it to movie any given amount.
The tensile stress is proportional to strain alone. Under the same force, a thicker and/or wider blade will stretch less, have less strain, and thus less stress. It would be equivalent to spreading the force over the larger cross sectional area, so it all should agree overall.
A bit off topic but my 126 14hp will up on my built up table and fired up tomorrow morning. My crazy question is what did you use to attach your sawmill feet or leveling stands to your table? I can't find nothing on what's best to use anywhere.. I just don't want my sawmill sliding all over the place lol..
Definitely need to fasten it down good. Seen too many people run their mill without doing that and the track gets out of whack quickly. I used 1/4" lag screws with a phillips head. Really worked well to hold the footpads down.
Sorry if noob question but why not a tension spring to compensate for heat build up elongation?
The tensioner mechanism on the sawmill has a strong spring to maintain positive tension under a variety of conditions/issues.
what about the distance between mounting points? A24 in band will stretch more than a 6 in band at the same pressure.
Strain is based on the ratio of stretch to original length. For an elastic material, the ratio will be the same no matter what original length -- the amount of stretch scales up with the original length. So we always look at the ratio for these calculations.
Theory is a little too deep for me. Comparing the three methods and using an average would be sufficient for me to do occasionally. I'm hoping the adjustment using the thrust bearings will be accurate enough, saving time. Good video for theory of blade tensioning for engineers.