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"Easy Way Out" Is No Fun At All!!

"Easy Way Out" Is No Fun At All!!

"Easy Way Out" Is No Fun At All!!

(OP)
I had originally posted a similar thread on another forum, but there is merely a sub-forum for restoration work & shop related questions. As a result, I have made progress in some areas of this intellectual exercise. I will do my best to format my posts reasonably well, as some may be a bit long.

Foreword.
How MaCGyver would spend his time after retiring. If Rube Goldberg was just a bit more to the point. If Tim Taylor were less well-equipped, and had spent time in the U.S.M.C. ("adapt & overcome!"). Or maybe just the b@$tard child of all of the above!

This, in a nutshell, is what has become a hobby of its own for myself. It is a mental exercise, in the same sense as when SWMBO & I pause "The Walking Dead" to discuss how WE would handle a dire scenario. With the difference of there being no zombies, and I'm basically trying to "make do" with scrap and/or trash. Most of the time, I find it both entertaining and rewarding, mentally.

There have been a few challenges in this hobby that basically snowballed into existence out of what started as an avalanche called "self reliance". Self reliance -> self educate about various prepping topics -> "What about shaving?... Is there a way to shave without throwing away money (cartridges) every month??" = straight razors etc. -> the current topic of indulging my curiosity*. One such challenge is pacing myself in order to not agitate my wife too severely.

With every year, the words of my father ring louder in my head: "If it's worth doing once, it's worth doing right the first time." I am also never afraid to ask a stupid question or four! I openly admit that I am strange and/or odd. I down right love thinking outside the box! And when one of my hair-brained ideas works out, or proves true a solution, I feel a sense of pride, and sometimes a bit exhilarated. But enough about me!

Many of my obstacles during these endeavors stem from a lack of knowledge of materials, not knowing how to proceed or what technique is needed, or a general lack of funds.

So I have spawned this thread to implore you to assist my mental exercises. I would greatly appreciate any help you can lend me, as I reason & logic my way through a metaphorical labyrinth I generously call "possible solutions". Comments, questions, and criticisms are also welcome (as long as you aren't flagrantly insulting thumbsup2).

I encourage anyone else with likewise curiosities to post them here as well! Let's get brainstorming. This is gonna be a blast fun (preferably no "blasts" stronger than a firecracker...)!

*= No small thanks to "Star Trek", and the way it openly embraced the natural curiosity we have as a species!!!

The most entertaining & ambitious project I have going right now is what started out as a bicycle powered table saw. After some development, a more accurate description for it would be a bicycle powered sawmill. It is worth mentioning that this contraption will only be mechanically powered, no electricity involved.

I snagged a couple boxes of random metal from an estate auction (needed the hand plane blade) for $8. Among my haul was well over a dozen pulley wheels of various sizes. This became the first pieces of the puzzle.

Here is a (very) rough sketch of of the drive train.


The scribble in the top left is me trying to keep track of the various pulleys.

Here is a rough sketch of the intended table bracing members, meant to secure the workpiece. Along with what I call a "mule": pulls the workpiece across the table.


Obviously, there is more to this. But I am currently between 12hr shifts, and my phone needs to charge while I recharge.

Problem solving, thinking outside the box, and creating as a hobby.

RE: "Easy Way Out" Is No Fun At All!!

Handheld standard 7 1/4" saws pull 13 amps. I believe that's in the neighborhood of 2hp.
If you're actually looking to build a sawmill to process logs, you need a whole lot more power. See http://www.sawdesigner.com/powcalc.php.

-handleman, CSWP (The new, easy test)

RE: "Easy Way Out" Is No Fun At All!!

Interesting question.

Would you run a table saw on a 1/4 hp motor? That's supposedly the most an average person can sustain for any length of time. There is a reason that pre-steam era wood cutters used two-man pit saws or water power.

Would a band saw would work better with your limited power budget? The circular saw blade will be pushing back against your feed mechanism.

RE: "Easy Way Out" Is No Fun At All!!

Perhaps a heavy flywheel could be used to store the energy.

RE: "Easy Way Out" Is No Fun At All!!

With sharp blades, the power used by a saw is closely related to the amount of wood being removed. A very thin kerf band saw uses much less power than a thicker circular saw.

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: "Easy Way Out" Is No Fun At All!!

The numbers quoted are for standard circular saw blades, which are on the order of 1/8th inch thick. Any thinner, the blade potentially can break or snap, resulting in serious flying metal. You could possibly minimize the power by using a blade with higher teeth count, say, 140, instead of 60, but it'll ostensibly take twice as long, as each revolution is removing less than 1/2 the material.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg
FAQ731-376: Eng-Tips.com Forum Policies forum1529: Translation Assistance for Engineers Entire Forum list http://www.eng-tips.com/forumlist.cfm

RE: "Easy Way Out" Is No Fun At All!!

(OP)
To answer a few questions and concerns...

Regarding the blade itself:
I have been in contact with a leading saw blade manufacturer that has a real R&D department. The gent who responded to my inquiry gave me some very helpful info.

First, as circular saw blade diameter increases, the minimum RPM required for it to "run true" (see: proper blade tension) decreases.

A larger blade also achieves higher linear feet per minute for every RPM. An antique sawmill blade over 3' across is not a practical option...

Yes, I plan to select a blade with a thin/hollow ground kerf, with a "finishing" tooth count.

Feasibility:
I am well aware that this is not an efficient method for cutting wood. I actually picked up a table saw in another estate auction about a year after conceiving the bikemill, so this isn't even necessary at anymore. Now, I am doing it just to prove I can!

The focus should be less on quantified "power output", and more on linear FPM. Through the multiple pulleys, there will be mass for some energy storage.

The feed-rate will be an important detail. Slow is the goal, because the workpiece will act as a brake (obviously). This will likely incorporate a scotch & yoke mechanism between a pulley and a ratcheting device.

I plan on getting a universal tachometer with halo proximity sensor, to satisfy my statistical curiosity.

Later (possibly a day or two), I will post some references & muses.
Safety:
This will not be attempted "half cocked". There will be dry runs, and calculations. I will be using scrap plywood sheathing as blast shields for the first several attempts, in addition to the usual PPE.

Problem solving, thinking outside the box, and creating as a hobby.

RE: "Easy Way Out" Is No Fun At All!!

MaCGyvers Workshop,

Try to think about why you would use a circular saw. Most motors rotate. Most motorized saws take advantage of this. If you think about it, a circular saw has poor leverage around the shaft. Motors have the required torque. Almost all manual saws reciprocate because we humans are efficient moving things back and forth. If I am playing with any circular saw, I want to position the saw, and keep my fingers, any dangling clothing, cats and the power cord out of the saw blade. If you are frantically peddling, you are not focused on where that saw blade is.

--
JHG

RE: "Easy Way Out" Is No Fun At All!!

(OP)
Those are fair points, but there are further considerations.

A bicycle is extremely efficient at converting our reciprocal motions into rotation. Plus, that 26" rim is the largest pulley wheel I have at my disposal lol.

Maybe I didn't explain it thoroughly enough, but there will not be anyone within reach of the saw blade while it is active! That is why I said a more accurate description would be a bicycle powered sawmill. Fences, guides, braces, winches: adjustable and lockable.

Oh, and as part of the "added challenge, just for kicks!", I am using as many off the shelf parts, or scrounging materials, as possible. A ten foot linear reciprocating saw blade that might have been used in an even older sawmill would be even more difficult to acquire... 14" circular saw blades? Not so much.

Thanks for responding, gents! And thanks for being patient while I gather and post the pertinent information!

Problem solving, thinking outside the box, and creating as a hobby.

RE: "Easy Way Out" Is No Fun At All!!

"A larger blade also achieves higher linear feet per minute for every RPM. An antique sawmill blade over 3' across is not a practical option..."

That's because it's moving more blade per unit time. The work required by the blade per tooth remains the same, so if there's more wood cut per unit time, the power generated must go up. There is no free lunch here. Moreover, a slower rpm actually makes it harder for something that isn't over-powering the blade to maintain momentum.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg
FAQ731-376: Eng-Tips.com Forum Policies forum1529: Translation Assistance for Engineers Entire Forum list http://www.eng-tips.com/forumlist.cfm

RE: "Easy Way Out" Is No Fun At All!!

(OP)
No free lunch, indeed... what I meant with that statement was: larger blade affords me a lower minimum RPM for proper blade performance, as well as a higher Lf/M... or as you said: "moving more blade per unit time". Even with all these pulleys, and a mountain of sweat & optimism, 7,400 RPM (7-1/4" recommended speed) at the blade might be pushing it.

Sawing is removing material per tooth (for the sake of argument, lets omit things like cut depth h tooth size). Regardless of saw blade shape, more teeth (run through material) per unit of time will mean more material removed per unit of time. Please, correct me if I am wrong.

Getting a slow enough feed-rate, with a high enough Lf/M saw speed will the key indicators for success.

Problem solving, thinking outside the box, and creating as a hobby.

RE: "Easy Way Out" Is No Fun At All!!

You may get that blade moving at light speed... but the moment you put a piece of wood to it, if there's no mass to the system, you're going to halt that blade in a very short distance. I can bog down my 3hp bandsaw, if I try. 1/4hp isn't going to do much more than cut a 2x4 at slow feed rates.

Dan - Owner
http://www.Hi-TecDesigns.com

RE: "Easy Way Out" Is No Fun At All!!

Maybe I missed it, but how would you physically sit on the bike and still be in a position to pull/push a piece of wood through the saw? It seems like the bike itself would present a physical barrier to getting close enough to the saw. That assumes its a one man operation of course. Not sure I could get my wife to pedal the bike while I used the saw.

RE: "Easy Way Out" Is No Fun At All!!

I did a little consulting for a couple of sawmills. I no longer have access to the appropriate reference library but I do remember a couple of relationships.
The power to run a saw is directly related to the amount of wood removed in a given time.
That is width of saw blade x thickness of cut x length of cut.
The old large circular blades typically had a kerf (width of cut) of 11/32 of an inch. This was rounded off to 1/3 of an inch. The sawyer allowed 1 inch for every three cuts. The error per cut was about 0.001 of an inch.
In the small mills, the sawyer may be setting based on the indication of a gauge moving with the carriage and about five to ten feet away from the sawyer. The gauge was marked in 1/3rds of an inch.
Setting by eye to an indicator marked in 1/3rds of an inch and typically 6 or 7 feet away to an accuracy of 0.001 of an inch?
Good luck.
Close enough was close enough.
But I digress.
Compare the 11/32" kerf to some modern band saws with a 1/8" kerf. (I have in real life.) You can now cut about three times farther at the same thickness with the same KWHR of energy.

Rotational speed of the saw blade:
A large diameter saw blade expands slightly at speed due to centrifugal force. The rim expands more than the center. This causes the saw blade to flutter. The saw blade is hammered on an anvil to dish the blade slightly. This was an art. Properly dished or hammered, the saw would run true at speed and cut straight.
This is not so important with a 7 1/4" blade as with a 54" blade.
Many 7 1/4" blades have radial slots to relieve the centrifugal forces and running speed is unimportant.
I am sceptical about the usefulness of your project to cut wood.
However I encourage you to continue and applaud the value of your project as a learning tool.
With success or failure, you will learn first-hand about pulley ratios, belt friction losses, torque versus speed, inertia and a few other relationships.
As a learning exercise your project will be a success.
Carry on.
Some tips:
7400 RPM may be the maximum speed rather than the recommended speed for a 7 1/4" blade.
The higher the speed the more steps of drive you may need. Each step increases belt friction losses.
Try to reduce the number of drive steps.
A flat belt or a timing belt has less belt friction than a Vee belt. Important at higher speeds and lower available torques.
A flywheel will be much more effective on the higher speed steps than on the lower speed steps. Try it and see.
Good luck.

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: "Easy Way Out" Is No Fun At All!!

Quote (waross)


...
As a learning exercise your project will be a success.

glasses

--
JHG

RE: "Easy Way Out" Is No Fun At All!!

(OP)
I suppose you might describe my frame of mind as this: I am not interested in "If", I actively seek "How"!

Here are a few of the references that I've bookmarked, not including various calculators and dozens of other sites/pages read.

One website that I dug up some info on...
http://www.900mpg.org/electric_building.php

It really helped with some curiosities I had about RPMs in regards to bicycles. It also explained the math behind it good 'n proper.

I found the following article quite interesting, and the website as a whole is very informative.
http://www.lowtechmagazine.com/2011/05/pedal-power...

I found a bit of old school inspiration in this fairly detailed video about the Salamander Sawmill (Europe, can't remember exactly what country).
https://www.youtube.com/watch?v=Q6FxG3ll-lw#action...

Here are some works by other people that have been part of my muse.

https://youtu.be/MegM0oKWCKs

https://youtu.be/kvQVwR8DKU8

https://youtu.be/3PMBf1SGVn8

https://youtu.be/RnxinyxHlAw

This, in one form or another, has been done before. I'm not trying to reinvent the wheel. It's just a blast to create something from practically nothing!

Problem solving, thinking outside the box, and creating as a hobby.

RE: "Easy Way Out" Is No Fun At All!!

A single V-belt and two sheaves loses about 7-1/2% of the power it transfers. You have six and will be losing about 45% of your 1/4hp.. (!)

Keith Cress
kcress - http://www.flaminsystems.com

RE: "Easy Way Out" Is No Fun At All!!

You must be joking not knowing what country the Salamander mill is in - really? Windmills, wooden shoes...hmm.

Treadle powered lathes and sewing machines ought to be on your list also.

RE: "Easy Way Out" Is No Fun At All!!

(OP)

Quote (Waross)


...
As a learning exercise your project will be a success.

Self-education is a common thread that connects most of my hobbies. To have a better grasp on requirements & potential capabilities, I have been crunching numbers...

Circumference = diameter * π
26"(π)≈82"
7.25"(π)≈23"
10"(π)≈32"

So, a 7.25" blade with a circumference of 23", at 7,000 rpm would = 161,000"/min.

Input.
82" * 773 (revolutions) = 1 mile.
773 * 20 mph = 15,460 rev./h = 257 rpm.
257 * 82" = 21,074"/min.

Ratios.
161,000" ÷ 21,074" = 7.6397
23" ÷ 7.6397 ≈ 3.0106
82" ÷ 7.6397 ≈ 10.7334

Having looked up some equations, I did a bit of reverse engineering, because none of the sources I came across were dealing with a similar situation. As such, would the following be (more or less) the the correct pulley diameter on the shaft with 7.25" saw blade??
10.7334 ÷ π ≈ 0.9583"

A v-belt pulley smaller than an inch is silly/not feasible. So I will need to get actual measurements of the pulleys I have, and do the math to establish what pulleys will get the job done.

Numbers for a 10" blade.
32" * 4,000 rpm = 128,000"/m.
128,000" ÷ 21,074" = 6.0738 (ratio)
32" ÷ 6.0738 ≈ 5.2685" circumference.
5.2685 ÷ π ≈ 1.6770" diameter.

The math is correct, but the application might not be lol. I have no tutelage or the likes at my disposal to check my work, so it awaits you, the firing squad...
thumbsup2

Problem solving, thinking outside the box, and creating as a hobby.

RE: "Easy Way Out" Is No Fun At All!!

If you want to turn X rpm into Y rpm then you divide Y by X to get the pulley ratio.

RE: "Easy Way Out" Is No Fun At All!!

Quote (MaCGyvers Workshop)

A v-belt pulley smaller than an inch is silly/not feasible.

So is a bicycle-powered sawmill. I encourage you to pursue the 1" V-belt. Don't think "If", think "How"!

RE: "Easy Way Out" Is No Fun At All!!

A few relationships and limits on saws in sawmills.
Saw speed: With large saws, the saw is dished so that at running speed the centrifugal forces will both straighten the saw and give it rigidity. With a large diameter blade the speed is critical.
With a slotted 7 1/4" blade, the speed is not critical and the speed may be slower than the maximum safe speed.
Cutting speed or feed rate: There are two limits on cutting speed;
The first limit is power. Too fast a feed rate will stall the prime mover.
The second limit is gullet capacity. The material removed by a saw tooth accumulates in the gullet until the tooth comes free of the kerf and the gullet can clear itself for the next pass through the kerf.
Two fast a feed rate and the gullets will be overloaded and friction losses will increase and efficiency will drop. The saw blade may be damaged by high friction generated heat.
This won't happen with manual power.
With a manually powered saw you are going to be severely power limited.
I suggest that with a given amount of power, there will be the same maximum feed rate, regardless of the saw speed.
I doubt that you will reach the gullet capacity limit until the RPM drops into the double digits and possibly the single digits.
Why loose precious power with belt losses and at higher speeds, windage losses.
Try a couple of very slow saw speeds. I believe that you will find the maximum allowable feed rate to be largely independent of the saw speed.
Forget gearing up the saw speed. Run the saw very slowly. You may well find a sweet spot between saw speed and feed rate but I suspect that it will be at a very slow saw speed.

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: "Easy Way Out" Is No Fun At All!!

Well, you say that this has been done before, and we have no reason to doubt that, but the results of those efforts can only be accurately described as "wood was cut".

Much good info has been given by others pertaining to aspects of blades and cutting with toothed blades, but this is hardly a complete and accurate description of the action and power requirements of toothed blades for cutting woods. You haven't clearly defined the cuts you will attempt, or set any limits, except human power and torsional delivery of that power.

Therefore, I can reasonably recommend your construction or adaptation of a mill using a band blade, because of the far greater energy efficiency afforded by superior friction characteristics and tooth efficacy. Since you haven't placed minimum or maximum workpiece dimensions, I'll select a range of 0-0.750" workpiece thickness, and you can determine the maximum distance from edge for your cuts by your selection of blade length. Your blade must have 4TPI, OR varied to obtain no more than 4 or less than 3 teeth in the workpiece. Your feedrate will be less than the 1/8" per foot of blade motion.

It'll work just fine. Now just build it!

.

(Me,,,wrong? ...aw, just fine-tuning my sarcasm!)

RE: "Easy Way Out" Is No Fun At All!!

A major waste of time.
Call it a 'mental exercise' and instead do something useful.

Keith Cress
kcress - http://www.flaminsystems.com

RE: "Easy Way Out" Is No Fun At All!!

At the end of the day this arrangement will probably give the best efficiency, smoothest action and fastest cutting.
No energy is lost in gearing or belting.
Normally a hand saw is used with one hand. This will allow the other hand to help also by pulling on the offside pedal.

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: "Easy Way Out" Is No Fun At All!!

Without getting into vast detail I tend to agree with the last two.

Basically this revolves around Power ( or lack therof) and how you apply that power.

A human powering a cycle can get to around 150W max for relatively short durations.

My 7" electric saw has a motor power of 10 times that, so even assuming near perfect speed increases, you're looking at an effective cutting power of less than a 10th for a person.

Only if you power up a flywheel using some kind of geared system could you get an short term increase in available power - the most efficient number of RPM for the human leg is around 80-90 rpm so a geared system would be best to continuously increase speed and hence energy in the flywheel. Seems far too much bother for the benefit to me.

Alternatively turn cyclical motion back into reciprocal motion or use some sort of pulley arrangement to pull a saw back and forth using your legs in motion.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

RE: "Easy Way Out" Is No Fun At All!!

I wish I could understand my own brain. And I say this of myself honestly in self-reflection... I don't understand why this project grates on my nerves so much. It's not highly likely to kill or injure anyone. It may be a "waste of time", but isn't that what hobbies are? I have no doubt that this build will not yield a useful sawmill. But what is the "use" of a model train? Or a working 1/12 scale V8 engine? Or a completed game of golf? Or https://24hoursoflemons.com/ ? Intellectually I understand all this. And yet... Grrrr.

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