This 12th Century Table Saw Is A Huge Force Multiplier!
HTML-код
- Опубликовано: 31 май 2024
- Thanks to DeleteMe for sponsoring this video. Check them out at joindeleteme.com/HTME for a special offer!
The trusty handsaw is great for making small cuts but cutting lumber from logs with them is tedious and difficult work that yields less-than-ideal results. The pole spring saw doesn't just make big cutting jobs easier, but also more precise. In this episode, I build the next step in my ongoing sawmill project.
Help us make more videos ► / htme
Instagram ► / htmeverything
Discord ► / discord
Merch ► shop.spreadshirt.com/HTME
H2ME (Second Channel) ► bit.ly/2GTcrcG
▾ Our Camera Gear: ▾
► GH5s: amzn.to/3BzY9Id
► GH5: amzn.to/3Eu0juJ
► Lens: amzn.to/2XXkVvM
► GoPro Hero 5: amzn.to/3EFkxSr
► Dracast Light Panels: amzn.to/3vUY2W4
▼ Send Us Some Mail ▼
How to Make Everything
PO Box 14104
St. Paul, MN 55114-1802
▼ Special Thanks to our Patrons at $15+ per month ▼
Ted L, Dominik S., Bryce Suchy, Potato, James Daniels, Edward Unthank, Steven Stowe, Dave Jones, dangerimp ., Kat PH, Emerson Propst, Jonathan Krailler, Jason Resha, Nathan Losee, Kyle Lauritzen, Jake Carpenter, Stray_Sparks, Craftsta64, Victoria Eads, Jeffrey Luck, Arishaig, Ian Miller, Kevin Shuttic, Erik Språng, Lee Schnee, Iain Bailey, alex latzko, Stephen DeCubellis, Adrian Noland, Tiffany Bennett, Estoky Designs, David George, Emmanuel Fillers, Benjamin Maitland, Larry Ullman, Dylan Rich, Jason Kaczmarsky, Jason Lewis, Andrew Nichols, Susan M. George, and Daniel Laux
▼ Credits ▼
Created and Hosted by Andy George
Primary Editing by Emerson Rice
Music by Taylor Lewin: taylorlewin.com/htme
The sawblades being the correct orientation would help a lot. Can't wait for the water version.
I commented about this too, I think it's a bidirectional blade, or straight teeth that cut in both directions. Having downward angled teeth should help.
was just going to say that.
Definitely if the teeth appointed downwards, the push will have a lot more force
Also incredibly thick blade!
I'm assuming the cut direction UP was to make the spring bow do most of the work...however since he had an open top table, he did more effort just trying to hold down the wood...eventually placing rope binders.
I would like to see a run on either side of the log, one with the blade reversed. This is basically a pit saw, but in a pit saw the man on bottom is doing most of the cut, while the man on top is guiding the blade line.
@@1234567890CAB probably also need a 1in4 or 1in5 tooth that do nothing other than pushing out the grinded off material
The obvious solution to the problem of the blade pulling the wood up, would be to have sawteeth angled, like on any push or pull saw, so it pushes the timber down
A better sawblade is probably the biggest improvement he could make without changing the design.
@@Coffeepotion It did look like he switched to a commercial blade by the end, but an asymmetrical tooth pattern would also make a big difference
Regardless the saw blade is still upside down
@@russellgeisthardt9828 Yeah, stop at 6:55, and you can even see the manufacturer label on the saw that he ended up using.
Yeah, just reverse that saw blade to fix this issue
On any vertical blade setup, the teeth should always be oriented to cut on the downstroke.
You may want to consider that it wasn't uncommon in the era these tools were used that the master would guide the work, and an apprentice/apprentices would provide the labor. This was a big part of how apprenticeship worked.
Also, the saw pit setup with top dog/underdog would have been the most common way to make long cuts simply due to its superior efficiency - but it takes a lot of mastery. Your attempt wasn't a failure - it was the same result any novice from this era would have achieved. Both dogs have to know how to follow their marks, push/pull seamlessly, and pace themselves despite phenomenal cardio. The blade would have been lubed or waxed even on kerfed blades.
Btw, the guy in the pit having to deal with perpetual sawdust down the shirt and in the eyes etc is where we get the term underdog as someone disadvantaged.
Yes.. All that lumbar could have built my house.
@Daniel Bonnar
👍 In 🇭🇲 the 'top notcher' gave us 'top notch'
what’s up dog
Cant believe you waited 8 centuries just to make this video about this magnificent table saw
Are you aware that we are currently in the 21st century?
@@PolyChromium no
BRO, why r u everywhere?? ur were on nileblue's vid
@@hummus2275 just seen him here, nileblues and sebastian lagues earlier haha
@@hummus2275 I figure this guy is either a bot or every stereotype ever. I just saw him commenting on viva frei minutes ago.
something to keep in mind too, when making structural wood that had to be precise, is that the wood was first cut into rough-hewn rectangular beams first, then shaped with smaller tools such as adzes, chisels, and finer blades. I believe also the sawblades used to be larded to help with binding. That all changed after larger-scale mills were built and didn't use raw manpower.
Two huge improvements you can make is the blade teeth orientation and the length of the blade. Currently you’re cutting on the up and down strokes and only really using the center portion of the blade. When it makes more sense to cut with just the downstroke and with the entire length of the blade. So angling the blade points down and sloping upwards would allow the wood to slide off the blade upon the upstroke. This would be an increase in efficiency and keep the wood from binding as much and hopefully nearly eliminate the wood from jumping up. Doing this may make it a little tougher to physically push the pedal down, but the yield and speed would make it twice as fast.
Also reducing friction everywhere there are touching moving parts might increase efficiency too, maybe beeswax would work
The teeth need to be angled slightly so that the cut is slightly wider than the blade to prevent binding.
@Proud2bmodest that's true. In an alternating fashion. I haven't picked up a hand saw in a while, lol.
@@Proud2bmodest commonly known as "set"
another problem i saw was that the guide was really wide, there wasnt really anything to keep the blade straight.
One way you can solve the lifting issue is only use downward angled teeth, however the blade would then mainly be cutting on the down stroke. If you go this route the bow on top wouldn't have to be as strong because there would be less resistance on the upward stroke. How it is set up right now, stepping on the pedal provides the cutting energy going down, and stores extra energy in the bow for the cutting going up. If all the teeth were angled down, you would only need to put in enough energy for the downward cut because less energy would be needed for the upward stroke. In other words downward angled teeth would be less effort but would require more strokes. I believe it could still save time because less interruptions, improved technique, and thus higher sustained speed.
Of course he is cutting on the down stroke. he is using his leg to push it down to cut. So yeah. Upside down saw.
@@laserbean00001 : No, _not_ upside down, his saw cuts in _both_ directions, so no matter which way he arranges it he'll get the same problem. OP is saying that he should switch to a saw that does all of it's cutting in one direction.
@@absalomdraconis Even though it technically cuts both ways, it's standard knowledge to know that it cuts most when going against the saw blades.
@@laserbean00001 yes... on a single direction blade. no for his blade which is just equilateral triangles. his cuts on both the up and down stroke equally.
\|\|\|\| = single cutting direction blade, cutting in this direction >
|/|/|/|/ = opposite cut direction <
\/\/\/\/ = cutting in both directions, as his blade does, equally
the standard knowledge you speak of, only applies to the 1st 2. most blades are like this, which is why its standard knowledge, however bidirectional blades are non standard and pretty inefficient due to the insufficient rake angle of the blade versus the piece, but they cut equally on both strokes.
@@seanflynn2507 look at 7:34
This is a pretty neat build.
Some moveable guides for the lumber would help with straighter cuts, and should be pretty easy to add.
Yeah, that was my thinking as well.
A good addition to help too is adding a longer bed, you can control it better if your not having to hold up the entire piece as well as control its direction. Also the addition of wheels on either side can aid in helping hold the wood down without having to extert too much force.
or just an infeed and outfeed sawhorse
And a guide.
How bout a sled 4 the workpiece?
And the blade frame should not be too much taller than the depth of stroke.
The hold down could be 2 wheels on a spring loaded horizontal.
If the log was pulled into the blade by the sled ratchet n gear system, he would be mostly free to jog away on a double treadle (left up blade, right down) like an elliptical workout machine.
@@ralph3333 that would even be better
More blade tension, wax it, and use a windlass as a sort of feather board hold down. If you angle it right it will also prevent the piece from moving back toward you.
you need to turn the sawblade around, right now it does the sawing on the up stroke, you want it to do the sawing on the down stroke
It saws on _both_ strokes, flipping it _won't_ help. He needs a different style of blade.
While I do believe you can LEARN everything through history, one big advantage you’d have in different times of history would be people. Realistically, it wouldn’t just be two people working so much labor alone.
Great video! My five year old and i have been watching your show for years. He loves it and learns to make things. Much better then movies:) ✅👍😊
To stop the binding you can try to and a bigger kerf to the blade and add a fence to try reference of, if you were able to heat treat the blade to keep it sharper or just sharpen it through out the cut if possible. Great video
Have you tried lubing the sawblade sides with a lubricant of some type, (beeswax maybe) to see if it helps with the kickup?
Only slightly more wonky than the big box 2x4s! Great work!
Your woodwork skills have gotten seriously sick! This channel is as much as seeing you grow as seeing the tech you build 😊
The reason why the wood was binding was because the flat part of the teeth on the saw were facing up, if you flip the saw 180 degrees it should bind on the way down if it binds at all. Keep up the great work mate!
The blade he is using has no "flat part", or rake. It is an omnidirectional farm cut pattern blade. The tooth has the same angle on both sides. So flipping the blade around would accomplish nothing. Being as the angles are identical on both sides. Although some aliasing in the video can make the teeth appear to have a rake to them. They in fact do not.
I've always thought the soul of this project/channel was the exploration of the concept of "making the tools to make better tools to make the tools to make even better tools"... watching you cycle through the hand saw, auger, chisels, and various other tools you've had to make and iterate on to make this new saw, along with the lathe(s), and other recent projects really show just how far you've come.
That was invented by RUclips. Over half the YT shop videos are about improving the shop and tools! Real craftsmen that do a lot of work often have the messiest shops and worn-out tools.
So glad to see the vast improvements in your carpentry and construction skills over the years, keep up the hard work man 👍
It would help to have a larger table and a saw stop on it. The next project should be a large plan.
Got a good giggle at 7:34 when you show the sawblade mounted upside down, and all the while complaining about how hard it was to hold the wood to the table! 🤣🤣🤣 Yeah, that'd definitely make the job harder! 🤣🤣🤣
On a side note. With the joint holes you make, you could make them undersized and then use a heated iron of the correct size to burn them to a tighter fit. Same with the ends that go in the holes.
Something that may help is having the blade the other way up, should hopefully prevent it lifting the peice your trying to cut
It's a bidirectional blade, so it cuts in both directions, so flipping it _won't_ help. He needs to switch to a unidirectional one, with the teeth slightly angled outwards.
One of the things about the pit saw and related stuff is how fast it can become with practice. A team of four or five guys can easily put out 20 or more 20 foot 2x4s in a day. Though the average, if I understand correctly, is 5 to 15, depending on quite a few factors. The key is to have 3-5 people rotating throughout the task. That way, you can go all day without taking more than a lunch hour. After a few weeks or months, you'll find yourselves popping out one or two, sometimes up to four or five, an hour. After a few months, the biggest factors are the wood and how well you maintain the saw.
They have competitions around it in the loggerodeos in my area. A loggerodeo is exactly what it sounds like. A rodeo that adds a bunch of logger-related competitions. Our area has always been real big in farming, ranching, dairy, and logging, so I grew up on things like that pit saw. You're judged on speed, team coordination, and the straightness and quality of the cut. A family, up north in Whatcom, "cheated" by hiring local boys from their High School to work in their lumber mill. They, being one of the oldest families in the area, also maintains - or at least used to maintain - one of the oldest lumber mills in the country as a working museum. They would encourage their employees and the Agrisciences and Forestry students they hired part-time to volunteer to work in the museum mill in their free time. The result was a competition team that was one of the toughest competitors in several old hand sawing and milling competitions. From beam hewing with a trio or quartet of Axemen (trios did one side at a time, quartets would do two sides at a time) to pit sawing to competitive sharpening (handsaws, teamsaws, power mill saws, and several types of axes), that team was VERY hard to beat; even for guys and teams that compete professionally.
The main reason it was binding and pushing/pulling the wood up, is because of the directionality of the saw. This saw seems to have the teeth half-V, so if you flipped it so the teeth are half-A, I think that would solve the problem. I think you should give it a try the next time you use the table saw. For the next saw you make, please make a flywheel for it. You could even try to make the flywheel double as a grindstone, even if you make it out of cement. A flywheel would also help, because you can first store some energy in the flywheel, then take your time to make sure the cut is straight.
And if you try to make a grindstone out of cement, then it would be useful to reduce the quantity of quicklime to 10% to 15% of the mixture, have 5% more water than cement, 5% to 15% crushed terracotta (powder) or dry sieved dirt baked into terracotta powder, have the rest be sieved dirt or mud, if you're not using mud then add the water after mixing the sieved dirt and quicklime, and try to compact the finished mixture like you would when making Rammed Earth. You can make it a circle/wheel from the beginning, or you can ram it down then cur the wheel and the center hole before it completely hardens.
Nice job! Your board actually looks exactly like the ones I’ve seen at home depot. 😂
Love your work.
exactly what I was looking for. make a frame that will take two blades and with adjustable widths and you can then slice the center slabs straight out of logs!
Thanks for making these saw/milling videos! You put a ton of work into it! I am grateful!
have you tried to turn the blade around? It's asymmetrical and the aggressive direction should be the down stroke.
It's _not_ asymmetrical, which is part of his problem.
I love this channel but coming from a family of carpenters, millrights, and bricklayers your craftsmanship sometimes hurts, but is always forgiven, keep up the good work
Super sloppy, but I guess he doesn't need to make it functional. Only needs to prove that it kinda works.
@@Rudy97 I feel that if he had to make it work better, he would. I think this whole series is a proof of concept that it all theoretically works.
This isn't Louis the XIV furniture. So refined joinery and French polishes will not be found here.
Let’s see them do it better
@@Rudy97You need a certain quality to make something worth the effort. I just watched the lathe video. If you don't get to a certain degree of precision it shows nothing. The first steam engine was so inefficient that there wouldn't have been an industrial revolution.
I absolutely love these videos! They give me everything I need to add the periphery to my ttrpg.
Andy getting both mad woodworking skills and huge leg gains
This is such a fascinating series. Only gets better as times goes on.
Good to see more precision in the craftsmanship overall!
At 2:09 the blueprint figures include both a blade guide (rollers) and a fulcrum/pivot to back whatever you are sawing. The reason for so many blade binds is you have no blade guide, so the blade just tracks wherever the slack happens to be (another feature in the blueprint is saw frame guides above and below the main table), and the reason you got such sketchy/wavy cuts along the length of the board is you had no fence or pivot. Many optional/additional resaw attachments for modern bandsaws have such a pivot, usually 6'' or taller, to back the material up just at the leading edge of the teeth. Having absolutely no guides for the blade, the saw frame, or the stock you were working with - I am honestly amazed that you didn't hurt yourself beyond what a band-aid or even ER could deal with. On that aspect, ummm, good job. Apart from that, slow down, do more research, and definitely go over the blueprints of any such contraption much more thoroughly next time else eventually you will get hurt, like, the you stay hurt for life, can't un-do that hurt, kind of hurt. You seem like way too nice of a guy for anyone to want that for you.
That's not a blueprint. It is an etching. They're called plates.
@@1pcfred Now, armed with that knowledge, I move forward to take over the world, Leroy.
Watching this series is such a nice journey. So many new things to learn. Such a nice presentation. Good for you and good luck for the future.
Long awaited project and can't wait until we get the waterwheel!
Really cool to see you advance into some proper power tools. Excited to see what they can achieve
I like to see how far you have come so far; you look so confident in producing quality equipment by hand. Right on!
I'm so proud of you dude. Your craftsmanship has come really really far, you'd have been a valuable guy in the pre-industrial world
Have to admit, you falling into the cranberry bog was just too funny.😂
Great video. 😊 keeping this series going is truly a labor of love.
I like it when you have projects that are mostly woodworking. Scratches that itch. An integrated clamp. more than the rope, or a riving knife after the blade might help keep cuts straighter.
I dabble in woodworking, simple projects or things I need, and I massively appreciate having power tools to do the hard work for me.
What I love about this type of video is how much our ancestors achieved with nothing more than basic tools and hard work.
Anyone who works in the trades and watches this and doesn't have a deep respect for the tradesmen of the past is lacking in imagination and understanding.
My trade is electronics, I learnt at a time when it was still considered important to know different techniques of soldering. I spent many, many hours heating cricket bat soldering irons in gas burners, soldering anything from fine guage wires, to tinplate boxes, lead, copper, etc, in fact anything I might come across in the army.
I don't remember hating it, but I don't remember loving it either, however in the 40 years since I learnt to solder, I have never failed to solder the things I needed to solder. I've sealed lead sheet, boxes, plumbed houses, gas pipes, countless wiring, and PCB jobs, it stood me in good stead for life.
I was offered a commission when I 18, which I refused, I'm pleased I did, learning a trade was probably the best decision I ever made.
Making the blade and keeping it sharp would be a challenge. Great vid.
The professor on Gilligan’s Island would be very proud of you.
So interesting to see how things used to be done and the upscaling that needed to happen to get more out of the tools.
This is so cool! 👌🏼
Thank you for sharing all your hard work with us dude ☺️
Outstanding Andy, a step improvement in both productivity and precision, both of which are vital to your endeavours. I would mount the saw blade the other way up though to improve the cut and reduce binding. At the moment it’s trying to cut more on the up stroke, which is less powerful.
andy you have come long way with this new sawmill i can't wait for water powered one
I am consistently impressed with your determination. I would have given up a hundred times by now. I can't wait to see you continue to make progress towards automation.
I think you ought to do a video on the various kinds of non-material technologies as well. Things like knot tying, materials knowledge, measurement and drafting/layout methods, teamwork and separation-of-labour techniques- that sort of thing. Man was figuring out how to lash sticks together long before he even figure out flintknapping, I'd wager.
Oh, also stonemasonry would be AWESOME.
Great show. I became interested in such things many years ago watching The Woodwrights Shop with Roy Underhill
you definitely need a outfeed table. that would allow the wood to have a support to combat the binding and wobbling.
Please make more things like this, this is genuinely so cool
HTME man has finally worked up an appreciation of modern technology.
it would probably be worth adding a fence to the saw (like on table saws) to help with cut straightness, and of course make the angle on the teeth steeper so they slide better on the return stroke.
looking down the length of the blade it also looks like the blade slides at least a centimeter sideways throughout the process of the stroke, so theres definitely some substantial room for improvement in tolerances
Just one of many suggestions, but if your blade was connected to a flywheel in the same offset way as the foot treadle of your lathe at :24 seconds into the video, this would pull the teeth away from the workpiece on the upstroke and may help resolve the issue of the board being lifted. Nice project.
An exceptionally cool project to watch getting made! Interesting how much of construction was subtractive (trimming the bow after mounting, for instance.)
You might consider "inking" the teeth of your saw to prevent binding on the blade. Inking is slightly bending the teeth in an alternating pattern. This makes the opening wider than the blade. However, if the teeth are bent out wider or are sharper on one side the saw will tend to cut in their direction, producing a curving cut which is useful in some applications. Oil and water can also be used as lubricants. However, both can cause staining and water can cause swelling. Depending on if the wood is hidden in a wall the staining may not be an issue.
you need to offset each saw tooth 1 left 1 right 1 left 1 right and so on, you'll only need a little offset to stop the saw binding happy evolution!
Looks like he has substituted in a commercially produced blade. It should already have the correct kerf on the teeth.
Yes kerf
@@MichaelOnines wasnt talking about the substitute blade speaking of to me it takes some of the magic out of build it yourself kinda stuff would love to see a video of him trying to improve his own saw blade instead of buying one
@@WiseOldRafikiYT I can understand the sentiment, but that mindset is what bogged this channel down in the first place and is what required the rules reset. Now he can "unlock" a technology and use commercially produced versions of it in order to explore the next thing.
As an aside, if you watch his original sawblade video he does strike the teeth to alternating sides to create a kerf.
I’ve seen a lot of comments about blade orientation and length which are both problems that need to be addressed. But also ensuring that you have the right amount of tension on the blade is super important in keeping your cuts straight and smooth. It’s hard to tell from the video but it looks a bit loose.
This dude really is the Doctor Stone of youtube, been seeing his videos on and off over time and love the progress
leaning the top of the saw ~1-5 degrees toward the operator will help prevent a good deal of the lifting as the saw comes up. using runners on either side of the foot lever will help keep the saw strait.
another method i have seen is to use a small wheel at the bottom of the blade so that it oscillates forward into a downward stroke.
Andy, you're pretty strong! And you have knack for building. Great job! I'm loving this episode!
I cannot wait! Man these last episodes have been REALLY good. Thank you! (id, watch 20min of that)
People are saying to use downward angled saw teeth to fix the problem, but there is another solution that is even easier and doesn't lose half the cutting power. Just get a cross beam that can be re-positioned and will physically restrain the piece you are cutting from moving in a vertical direction. You could just simply get another piece of wood and tie it to the horizontal supports that the piece you are cutting is resting on. Or you could get fancier with it if you want but it doesn't have to be that sophisticated to do the job.
Sawmill/waterwheel sounds pretty cool
Hey, love the design. I believe if you flip the blade of the saw it should help with the binding and pulling the wood up but down.
You really should heat up the saw blade and quench it to stiffen the metal/ harden it hence sharp edge lasts alot longer. Very cool channel. Love it.
FINALLY! I love this project, loved that video.
Good fix - flip the saw teeeth the opposite direction, then you can leverage your leg strength and the downward cutting motion helps secure the piece.
So there's a lot of people suggesting a different saw blade geometry and tooth geometry but i would also suggest considering hanging a sandbag or sunch on the cut end. If you think about it like a lever then especially at the start the saw has all the leverage against you to work like a wheelbarrow. I think having either a sandbag on the opposite side or some kind of hold down mechanism would be beneficial.
Another option could be to oil up the saw blade and consider alternating the teeth left and right so that the kerf is wider than the blade itself.
1:14 straighter than some 2x4's i've seen at home depot
The sawteeth blade is upside down(at 7:38 you can see it).Instaled the correct way it pushes the workpiece into table..Much easy'er and less dangerous.Also when blade is installed correctly do not push on the wood during upstroke.(keep that also in mind with inventing the water powered saw).Subcribed
I was a carpenter. In the early 70s. We built houses using nothing but handsaw. No electricity at the homes no next door neibours. Cut everything with an 8 tpi handsaw you could cut 1 inch per stroke 5/8 inch plywood . 96 strokes to rip a sheet of plywood. Sure was nice when they started getting electricity out on them jobs.
Awesome video thank you 👍
Put a hold down bar on the outer frame using holes in the frame with dowels and wedges to get the correct hold down height.
yesss I love all these wooden framed machinesss
I'm glad to see a return to the technology tree.
I dont know anything about saw blade designs but some sort of vice or clamps would be a great addition to this saw to hold pieces down
if you way the slide area for the saw it will work easier. Some folks advocate waxing the blade periodically also. I always did that with my hand saws. Also adding a wedge to the end of the cut can prevent binding.
I’ll never get tired of that cranberry bog clip.
Dimensional lumber is one of those luxuries of the modern age that many people just take for granted.
Could you please make a playlist with all the woodworking and tool making videos? I'm new to the channel and I'm a bit overwhelmed.
Edit: what an amazing journey this is!
Looking forward to the 12th century water jet!
You may want to experiment with a slightly wider saw set to aid in binding.
I have been tinkering with a 5ft logging saw and once I got the saw sharp and set it was suddenly a joy to use.
He needs to fix the basic sharpening first.
Just a few helpful tips. Orientation of the blade is important, also look into using weight and a heavier spring, meaning a spring that takes 200 lbs to bend it and putting 150lbs of weight on the bottom of the peddle. That way it has alot more weight and force behind the saw blade. Also if you put a guide on the side of the cutting blade you could make it alot straighter
Lovely work.
something i can suggest from what ive seen to make it less intensive is too move the pivot point for the foot tredle, move it forward so you are pushing it more like a car pedal with your ankle than whole leg and increase the length to increase the potential energy. That should hopefully reduce strain on your leg making it easier to endure for a longer period :)
You could (lathe) turn an upper press-roll, and tension with a lower spring (adjust for thickness in the rope) ... maybe a simple hourglass roll for rounds, and a straight roll for edging.
You need to devise a bench clamp, I'm squirming... 🤣 Great video.
This is the kind of videos i love, i just wish you would show more details
Being a bit pedantic, but I'd consider it more like a precursor to the Bandsaw than the table saw.
They also had a bigger version hooked up to a water wheel, which solves the effort/scale and straightness issues you had breaking down a log manually.
why not add a vertical stabilizer/clamp to stop the wood from rising? You could use push pins.
Agreed
Tension your blades! Seriously making so much more work of it, even with the modern commercial ones. Historical bow saws etc. all had a method to tension blades. Some time studying techniques of use as well as design and construction would be well worth it too.
There is a reason why place for sawing timber was called "saw mill"... It used water power same as one for grinding grain. BTW, consider round peace of stone as crankshaft to keep movement speed steady. Instead of bow, I would go for greased metal pulley and counterweight. You could fix if on house beam and it would be very durable.
Great design, great execution, and saw itself upside down :D my man!
Correct me if I'm wrong but it looked too me like your saw blade either cuts on both strokes or is one way and put in upside down? One that cuts in only one direction oriented to cut on the down stroke will stop that jumping almost completely with proper pressure technique and give you much better control & speeds.
Also: pretension your bow a little to help the return speed and force.
Roy Underhill would get a kick out of using this! 👍