How crowned pulleys work
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- Опубликовано: 30 сен 2024
- woodgears.ca/ba...
Showing how flat belts stay centered on crowned pulleys. Before V-belts were invented, flat bets were used to transmit power to all kinds of machinery. Flat belts can run faster, and offer higher efficiency than V-belts commonly used. But they need more tension, and need to be set up more precisely to successfully track.
Got that shout out Matthias!
Love your videos, great to see steve feels the same.
I'm starting to wonder why I ever went to school. Should have just tuned into this channel.
2:29 and headphones are not a good combination :)
Yup, exactly what I thought too. First "ah ok that's not too loud OWW OWW OWW NOW IT'S LOUD!..." :x
Then again, it should have been expectable. 11k RPM is a LOT, I got a Dremel and that thing's tiny and makes already a lot of noise, this thing's several times bigger so yeah, should have expected it, but didn't...
A brilliant explanation. Thank you.
Ah, thank you for making your intelligence level clear. I always wonder what sort of geniuses leave comments like that. Now I know :)
whos from steve mould?
Thank you for explaining this. In the old days before there were combine harvesters, farmers used to use threshers to separate the grain from the chaff, and they were powered by pulleys without flanges, so I always wondered how they stayed straight and didn't just fall off the pulley.
Hey! I'm from Portugal and I'm 44 years old now. When I was about 8 years old I asked myself just that too watching farmers around my grand parents country house.
Then everyone turned to new machines and that old doubt just kept on until today when I watched this video.
2:30 headphone warning
Thx
too late :
NO KIDDING
What was that thing?!
It sounded gr8 though
Yes, large belts work the same way
I looked at that very page, and it doesn't actually explain how it works. There isn't an adequate explanation out there, which is why I wrote a page about it and made a video.
Those Sorting by New: 2:30 headphone warning
Does this mean that a reverse crown (the lowest part of the pulley is in the center and the sides of the pulley are higher) would be unstable and counterintuitively throw the belt off the pulley with a minor disturbance?
Steve Mould just did a video on that!
a belt won't climb an out of alignment pulley, actually. So its really misleading.
Please watch my videos on bandsaw construction.
And FYI - steel does stretch, just a lot less.
Oh, and guess what - it DOES work with sanding belts.
2:27 Headphone users, turn your volume down now...
Got it at a surplus store many years ago. Used it for the wasp sucking contraption. Also used it as the blower in the air engine video (its actually quieter than a vacuum cleaner, and about as powerful)
No need to try it. A lot of European table saws use flat belts already.
Well, that was anti-climactic. "I found this rubber band on some broccoli" to paraphrase
there is no broccoli
Wow. Never really put any thought into how this worked, but that is a brilliant explanation of it. Kudos.
Thank you, that was interesting. I assume the same principles apply to the large belts used by farmers on the old power-take-off style found on threshing machines, steam engines, etc.
What does your fan do?
Very cool...I've always have wondered how that worked. Thanks.
I finally learned about this when I was trying to keep rubber tracks on a treaded robot. I added flanges to the sides of the wheels but the tracks came off faster than without the flanges. I tried making a crowned pulley and it worked better than the stock wheels.
Mr. Mould reference
How many RPM can a bunch of broccoli take?
I'd say a solid 60 rpm
Thank you, I often wondered about that.
With a flat belt, the contact surface is running at the same velocity or speed across the width of the belt. So it is relatively friction-free.
With a V shaped cross-section the big end of the V travels at a different (faster) surface velocity then the small end of the V. This means the V belt is trying to travel at many different speeds at the same instant. Most of the contact surface is either sliding and skidding against the sides of the pulley or sheave grooves.
It also has to slide into and out of the grooves as the sheave rotates.
Wow... that was quite informative...
Wow, Amazing! I'm building a sawmill and I was wondering how the blade keep track on my pulleys. Thanks.
It's a bit counterintuitive. My intuition said to use a concave pulley 🤦♂️
The belt flew right of😂
So.. they explanation of “How” crowned pulleys work is … magic?
You showed they do work, but didn't really explain how or why.
They are super cool though, and very counter intuitive physics.
Very nice, my dad showed me how it worked when i was young. :))
just thinking out loud" see, that's why I subscribed". thank you
Short, concise, engaging. Loved it ♥️
(i just realised how old the video is lol)
What happens if the belt is wider than the crown. can it still track?
I was brought here by Steve Mould. I've been MW follower for quite a while.
Just came to say I was a fan before you got name dropped by Steve Mould!!
Great explanation and very helpful!
that was great....also very loud when you turned that on :-P
thanks,
Few people understand and pay attention to it
Back when Matthias had a store-bought bandsaw
Angus from Maker's Muse brought me here.
Centrifugal force I am told.. you say curvature.. hmmmm.. well centrifugal, centripetal force does help tracking at speed. At low speed tension is the key I guess...
After wondering about this for a long time, and watching Acorn to Arabella building a wooden boat, I went looking for the answer to the "belt question." Why am I not surprised when your video popped up Matthias? Great job and thanks.......DD
Matthias could you do a video that is a simple explanation on "Pulley Basis" for Band saws. Larger Pulley faster smaller pulley slower or vice versa????
Thanks
I was watching your videos for almost 10 years, but never seen this one. Coming here from Steve Mould recent video ;) Love it.
That was extremely interesting. You have a very clear way of communicating information, thanks!
Do you know if this principle can be used on cogged belts without messing up the belt? I want to try this on my 3d printer, but I am worried it will distort the belt. I'm wondering if there is a formula for determining the amount of optimal crown you can get away with... (Off to google I go...)
I have never seen this used for cogged belts. Probably doesn't work on cogged belts.
The effect of the curvature is pretty counter-intuitive. You'd think that curve edges would cause the belt or blade to fall off more easily but has the opposite effect. Pretty interesting explanation in the video.
I have been fighting a small metal cutting saw with badly worn wheels, time to fix the profile on the lathe,Thank You!
You're correct. It doesn't explain it. (Just suplimental for your viewers I guess)
It's a nice problem.
I have to imagine it as a "want" of the belt to restore stress equilibrium across the belt width. i.e. the only way it can do that is to fall off the pulley or climb onto it. There is more friction on the uphill side so tendancy is to remain there. I'm sorry I can't give a reasonable description in 500 characters. I "think" I almost understand it.
Thanks very much for replying
Cheers
Your explanation with the pictures on your website is better than your video imo. Thank you.
whether the two rollers should be conical
I really enjoy your educational videos (well, most of your videos are educational anyway, I mean those that teach one isolated concept explicitly)
Oh thanks. Now I know what I made wrong on the drive-pulley on my new beltsander.
@MufinMcFlufin - unlike the belt shown in the example, which is flat on both sides, a v-belt has ridges running along the length of the inside of the belt. These ridges fit into valleys cut into the pulley face to stop the belt slipping off sideways. If you can have a look under the bonnet of a car, in all likelihood the belt driving the fan in front of the engine will be a v-belt.
Hi Mathias - Like you say - tension is kind of key.
When you knock the belt to one side in your vid, draw the line of force(tension) in the belt. It may be that the line is no longer perpendicular to the pulley axes.
I wonder if the line is always directed in the direction of the crown pulley centre, if so, the belt will tend to follow it.
To test this, i guess you could build a wide crown pulley and offset the belt a lot to see if there is a point where it wont re-centre.
Just waffling here
Thanks a lot, I wondered since quite a while why and how this works. Great explanation!
I'm amazed that you're a bass player and you say that steel doesn't stretch. Um, why do you think a bass guitar has tuning knobs? Of course steel stretches!! That's why your bass strings go out of tune and you have to re-tune your guitar. Ever played a gig outside vs. inside? Does cold and humidity make a difference in the tune of a guitar?
Hi Mathias - This is a very interesting phenomenon, (& I can't yet explain it simply).
If you google "how it works crown pulley" you should see 1st result is from Ihup. edu
This page is posed as a question and more or less repeats what you mentioned. It does introduce the paradox though which requires a robust explanation.
Very interesting stuff.
Good vid 5* Thanks very much
In theroy yes you can but in a frictional world nothing can run forever, because matter can be not made nor distroyed so friction takes energy slowely out of a system slowing it down, thus no forever,
would be nice and clean though
PS - The "out of alignment" pulley's on that webpage mentioned, is not an equivalent problem to a crown pulley. i.e. in the "out of alignment" pulleys, the wheel is pushing the belt off from the side - a sideways thrust if you like.
So it looks a similar situation, but it isn't
But a steel blade won't stretch.
hah I am blind. I got answer of my yesterday`s question here. thanks ;d
I have old 5.25 inch floppy drives that are driven by flat belts. Just like your demo.
When I am rich and can buy whatever the hell I feel like, I am gonna have a monster of a woodshop. Also, great videos!
Do you write anything you say in your videos beforehand? It is all very clear and whatnot.
I Had little idea! Seems kinda counter intuitive to have an surface that arcs inwards to put a band on, but it helps with tracking! very cool! I will certainly have to think long and hard about this.
Excellent explanation. I love the comment about the "belt" coming from a head of broccoli ;)
That fan sounded like a jet engine when you powered it up -- what secret device are you building now?
Thanks for the explanation, It was something that I always wondered about ever since I seen a tractor drive a belt. But they had a twist in the belt and I have no idea what that was about.
uuuuum sound warning?
This is cool, but I still don't know what a v-belt is. I was kind of hoping near the end you would show a side by side comparison of the flat belt and the v-belt.
How do i make a pulley anyway i Need it for design tech
a flat belt pulley is always crowned that keeps the belt in center they always track to high spot
That seems so bizarre to me
i allways wondered how the sawband of a portable lumber mill maintains to center the blade. this explains it pretty good. thank you!
Learned something new!
Aren't the pulley or wheels of a bandsaw the same as those pulleys
Belt sander would be an obvious tool for demonstration.
Never heard of that before. Your demo was very interesting
geekiest but coolest channel. some actual down-to-earth and practical engineering here.
This is awesome, but I think you broke my ears when you turned on the machine.
Can you please explain by some more details?
Watch the video -- that's plenty of detail.
If sanding belts don't stretch, then why do they make low-stretch belts?
...great explanation and demonstration!
wonderful explanation sir ji
Who needs the Discovery Channel now that we've got you, Matthias?
So glad I watched this before attempting to make my homemade belt sander. I will certainly put this principle into practice for my design. Thanks Matthias!
Also if the belt tension reaches danger levels the flat belt will pop off the crown before it burns. Safety mechanism of sorts.
they should use this in school
Thanks
Awesome Explanation!!!!!! :D wood wizard is always the best
Your bandsaw demonstration actually was not very safe I was adjusting the tracking on my bandsaw once while it was on and suddenly I heard a loud bang, the blade came off the wheels and snapped, thank god the the doors were closed (there is a little window on the side)
Do you really?
It's magic
Fascinating
3:37
lol that lookskinda dangerous to do :P
My ears😰
lool oooh clever nicely done
Cool
Wow!
Lego
I can't find a tilt adjust control on my bandsaw. blade tries to walk off the bottom wheel. it's centered on top wheel. any suggestions?? I'm afraid the blade is gonna jump off and eat my fingers.
it's a late 80's craftsman tilting bandsaw. it's also a 2 speed saw & I'm not real sure which is faster. large drive pulley to smaller wheel pulley or the opposite? was my fathers. he passed away. any help would be much appreciated
a bigger pulley on the motor, and smaller pulley on the wheel will make the saw go faster. idk about the tilt control knob on ur saw.