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View Full Version : How does this pedal-powered machine work?



winchman
02-17-2013, 04:13 AM
It's a food processor, but it's the drive mechanism that I cannot figure out.
http://www.ecofriend.com/student-designer-creates-pedal-powered-food-processor.html

http://ecofriend.com/wp-content/uploads/2012/07/pedal-powered-food-processor_3_C9ZMo_69.jpg

http://ecofriend.com/wp-content/uploads/2012/07/pedal-powered-food-processor_7_BeoQc_69.jpg

I suspect it's to increase the torque for getting the flywheel turning and to keep from having a pedal with no resistance when it is turning. Maybe you can explain what's going on.

I'd sure like to see the other side of the large chain wheel.

Astronowanabe
02-17-2013, 04:30 AM
I wonder if the small wheel ever lifts the chain off the big wheel
allowing the pedal to re-position?
(I dont see how, seems chain will touch the big gear at two points when small gear is
in line with big gear axle opposite flywheel axle)

or as you suggest just increasing the leverage on the powerstroke

The Artful Bodger
02-17-2013, 05:00 AM
350 Watts! 400RPM, have they got Lance Armstrong on the pedal?

Charles Lessig
02-17-2013, 06:40 AM
Here is what I think it is. All the sprockets are in the same plane. The flywheel sprocket has a ratchet.
As the pedal gets near the bottom the eccentric sprocket increases the ratio and pulls the idler arm and its spring.
The spring pulls the pedal back up for the next stroke. Maybe the ratio change makes it work better.

winchman
02-17-2013, 09:51 AM
I hadn't thought about the possibility that the smaller chainwheel is fixed rigidly to the larger chainwheel. If that's the case, the first part of the downward pedal stroke will have more leverage and torque, and the last part of the stroke would give more speed. You can push harder near the bottom of the stroke than you can near the top, so you get maximum output over the entire stroke.

They could have accomplished the same thing with an elliptical chainwheel, but maybe that wasn't readily available.

The spring you can see is just to keep the chain tight, since it's attached to the idler sprocket arm. There must be another spring you can't see connected to the pedal/chainwheel assembly to make the pedal return.

Black_Moons
02-17-2013, 10:09 AM
Yea im guessing it provides more torque at the start and more speed at the end, and there is a freewheel between the last sprocket and the huge wheel

My guessing is it would provide a hard resistance at the end of a stroke, giving you feedback on when to stop. It would also allow you to get it going a little faster by doing shorter strokes near the end of the stroke length

It can't go around 360 or it smashes into that support arm, I assume the whole pedal has a clockwork spring somewhere.

John Stevenson
02-17-2013, 10:19 AM
Using the big sprocket with the cutaway and smaller sprocket on a larger pitch circle is just a cheap way of making an eccentric sprocket so you have variable ratio.
If you look at the second pic you can just see the return spring behind the large sprocket. The driven sprocket or bevel gear will have a one way roller clutch fitted to allow the drive sprocket [s] to return for the next stroke.

Look at the mechanical advantage of eccentric gears or sprockets.

http://www.youtube.com/watch?v=zOmSrePm_UM

vpt
02-17-2013, 10:30 AM
Here is what I think it is. All the sprockets are in the same plane. The flywheel sprocket has a ratchet.
As the pedal gets near the bottom the eccentric sprocket increases the ratio and pulls the idler arm and its spring.
The spring pulls the pedal back up for the next stroke. Maybe the ratio change makes it work better.

Thats exactly what I think, like a compound bows cams kind of. Guy couldn't make teeth on a cam so he had to use two sprockets and cut one up to install the smaller to create the cam.

A.K. Boomer
02-17-2013, 11:02 AM
You guys are all overthinking it, it's just about the most basic form of providing pedal power to something without having to run into the problem of the old treadle type machines that you can't start at TDC or BDC,,,

You push down and pull the chain and propel the wheel and stretch the return spring at the same time - you release and a one way sprag disengages the wheel and the return spring sucks back the chain ready for the next "push"

that's it - no magic, You may not be making any power on the return stroke like a treadle type machine but you also get to stand up in one spot and work with your hands while providing power - something that would be hard to do while standing and treadling and near impossible if trying to complete a full pedal stroke.

most treadle type machines are utilized whilst sitting down cuz it takes impeccable timing to achieve good power and it's a great benefit to have your phat little a$$ anchored to a seat of some kind...

Edit: Now i see why you guys are getting screwed up - the two pictures are a contradiction in terms,

Only the top picture is functional - the lower one is simply the weight of the apparatus coming to rest without the crank arm, the reason for the second smaller sprocket is simply to introduce a variation - this is nothing more than a ramp up to take up the chain on one side and the spring on the other side then stretches - it's a way of keeping the chain continuous - it would be inop. without the smaller sprocket as the pedal would not return - but there is no real reason for this - it's overcomplicated - alls that's needed is the large and small wheel sprocket and 2/3rds the chain - and you just link the spring directly to the one dead end of the chain - the other end is wrapped around the sprocket and it's dead end is bolted to the sprocket itself...

If there's some kind of thinking about the stroke being eccentric for easy start at the top then no prob. just mount the large sprocket off center accordingly....

A.K. Boomer
02-17-2013, 02:01 PM
This is the example im talking about - half the sprockets - less chain - same results... and like i stated before if it's ease of start at the top of the stroke your after then just mount the large sprocket eccentric accordingly...

beer top cap and half of hand rolled cigarette are for size comparison purposes only...




http://i146.photobucket.com/albums/r249/AK_Boomer/DSC03046_zps85cbf112.jpg


the unit in full use with one happy customer;

http://i146.photobucket.com/albums/r249/AK_Boomer/DSC03049_zps28ee9801.jpg


tune in next week for "honey - does this juicer make my a$$ look phat"?

adnbr
02-17-2013, 02:34 PM
Here's a video of the device in action:


http://m.youtube.com/watch?v=zyM6PJdycUc

Black_Moons
02-17-2013, 02:40 PM
http://www.youtube.com/watch?v=zyM6PJdycUc
For people who want to watch it on a desktop, For some reason the other link wanted me to go to some rtsp:// website or something and clicking 'desktop' just brought me to youtube.com, weird.

rohart
02-17-2013, 07:21 PM
I once had a bicycle with elliptical chainwheels. It was rubbish. I can see how this Amish food processor gets a kick towards the end of the pedal stroke. Might as well ditch the coffee grinder and mount a small lathe there. Get the wife to use instant.

What if she wanted to bake a cake. Does hubby have to sit there pedalling for half an hour ?

John Stevenson
02-17-2013, 07:47 PM
Watched the video, just as I said in post #7, a cheap way to use off the shelf sprockets instead of making an eccentric one. Roller clutch at the top.

Richard, can't be Amish, they have a web site. :rolleyes:

No good using it to drive a lathe, if you were screwcutting you would get a variable pitch thread :cool:

winchman
02-17-2013, 07:48 PM
Thanks for finding the video. That really helps.

You really don't need the second chainwheel. All you need is something to increase the radius from the pedal shaft to the last point where the chain touches. The teeth on the other part of the chainwheel will keep the chain from slipping.

oldtiffie
02-18-2013, 08:11 PM
As an aside, here is an old treadle and belt-driven quite old lathe that is surprisingly smooth and easy to start and keep moving - it is preserved for "show" now.

http://i200.photobucket.com/albums/aa294/oldtiffie/Old%20machinery/Old_lathe1.jpg

http://i200.photobucket.com/albums/aa294/oldtiffie/Old%20machinery/Old_lathe2.jpg

http://i200.photobucket.com/albums/aa294/oldtiffie/Old%20machinery/Old_lathe3.jpg

http://i200.photobucket.com/albums/aa294/oldtiffie/Old%20machinery/Old_lathe4.jpg