(1) Anybody know what two common materials (when slid against each other) have really low friction? Please, water and oil don't count as answers - I need solids!
(2) Anybody know if WM2D has any issues with representing friction correctly?
Comment: sliding a non-rotating disk along the edge of a curved polygon in WM2D seems to work in WM2D, but my skills in the garage are lacking.
Regarding JEEBessler's comment on the clues webpage of besslerwheel.com: "...axis, which in its turn must also move." - does that mean the "axis" is rotating, or moving in another way?????? hmmm.
Thanks.
Randall
Low Friction Materials, and WM2D Friction Question
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ken_behrendt
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re: Low Friction Materials, and WM2D Friction Question
Randall...
Hmmm...low friction solids? How about steel on some hard plastic material? Or steel on glass or Teflon?
I can not comment much on WM2D and friction because, aside from air resistance, I never set the friction on my model's pivots. I think that for most small physical prototypes of devices, the various bearing and pivot frictions are so small (especially if you are using silicone lubricants as I prefer to use) that they can be treated like they do not exist.
About the "moving axis" quote...that is supposed to be the axle of one of Bessler wheels. It is a solid piece of wood to which the internal superstructure of the wheel's hollow drum was attached. The axle and the hollow drum turn together as one piece and there is no relative motion between them.
See my sketch below.
ken
Hmmm...low friction solids? How about steel on some hard plastic material? Or steel on glass or Teflon?
I can not comment much on WM2D and friction because, aside from air resistance, I never set the friction on my model's pivots. I think that for most small physical prototypes of devices, the various bearing and pivot frictions are so small (especially if you are using silicone lubricants as I prefer to use) that they can be treated like they do not exist.
About the "moving axis" quote...that is supposed to be the axle of one of Bessler wheels. It is a solid piece of wood to which the internal superstructure of the wheel's hollow drum was attached. The axle and the hollow drum turn together as one piece and there is no relative motion between them.
See my sketch below.
ken
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- Without the oiled cloth covering, the axles may have looked like this...
On 7/6/06, I found, in any overbalanced gravity wheel with rotation rate, ω, axle to CG distance d, and CG dip angle φ, the average vertical velocity of its drive weights is downward and given by:
Vaver = -2(√2)πdωcosφ
Vaver = -2(√2)πdωcosφ
re: Low Friction Materials, and WM2D Friction Question
Thanks for the quick reply, Ken.
I was thinking that inside the drum the axle may not exist as a straight piece across to the other side, in that way the axle may move.
In the attached drawing (of low calibre artistic endeavor), The first one shows that the shape of the axle may be varied. It could even be like pedals on a bicycle - not shown in the drawing.
In the drawing on the right, maybe the weights rest against a sleeve "axle" around the real axle which is free to move differently than the axle of the wheel.
I was thinking that inside the drum the axle may not exist as a straight piece across to the other side, in that way the axle may move.
In the attached drawing (of low calibre artistic endeavor), The first one shows that the shape of the axle may be varied. It could even be like pedals on a bicycle - not shown in the drawing.
In the drawing on the right, maybe the weights rest against a sleeve "axle" around the real axle which is free to move differently than the axle of the wheel.
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- axle "moves" inside drum - two possibilities
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ken_behrendt
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re: Low Friction Materials, and WM2D Friction Question
rmd3...
The interior axles that you have proposed are, perhaps, all possible. But, there was a reference made by Bessler to how he used to let visitors to see his early one directional wheels reach in and "grope" their axles. I'm sure if the axles were anything other than a continuation of the visible external pieces, then someone would have noted this and it would have become "common" knowledge. I do not think Bessler would have allowed the axles to be groped if they had some sort of unusual shape inside of the hollow drum.
I've committed myself to exploring designs which have no connections made to the wheel's internal axle section. It seems clear to me that the "works" of Bessler's wheels were very near the rim.
ken
The interior axles that you have proposed are, perhaps, all possible. But, there was a reference made by Bessler to how he used to let visitors to see his early one directional wheels reach in and "grope" their axles. I'm sure if the axles were anything other than a continuation of the visible external pieces, then someone would have noted this and it would have become "common" knowledge. I do not think Bessler would have allowed the axles to be groped if they had some sort of unusual shape inside of the hollow drum.
I've committed myself to exploring designs which have no connections made to the wheel's internal axle section. It seems clear to me that the "works" of Bessler's wheels were very near the rim.
ken
On 7/6/06, I found, in any overbalanced gravity wheel with rotation rate, ω, axle to CG distance d, and CG dip angle φ, the average vertical velocity of its drive weights is downward and given by:
Vaver = -2(√2)πdωcosφ
Vaver = -2(√2)πdωcosφ
re: Low Friction Materials, and WM2D Friction Question
rmd3,
You could try a polished steel with ceramic. Also a molybdenum powder or grease. I think they also make this in solid shapes.
David
You could try a polished steel with ceramic. Also a molybdenum powder or grease. I think they also make this in solid shapes.
David
re: Low Friction Materials, and WM2D Friction Question
Ken,
You mentioned that you never played around with the friction value of your pivots in WM2D. I'm actually not thinking of a pivot - I'm just trying to figure out how these two surfaces in WM2D (a non-rotating disk and a polygon curve edge) reflect reality.
See the image attached which basically forces a non-rotating disk along the edge of a polygon curve.
David,
Thanks for the suggestions.
You mentioned that you never played around with the friction value of your pivots in WM2D. I'm actually not thinking of a pivot - I'm just trying to figure out how these two surfaces in WM2D (a non-rotating disk and a polygon curve edge) reflect reality.
See the image attached which basically forces a non-rotating disk along the edge of a polygon curve.
David,
Thanks for the suggestions.
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ken_behrendt
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re: Low Friction Materials, and WM2D Friction Question
rmd3...
Try to avoid having a circle up against or resting on a concavity in a polygon in WM2D models. This arrangement can result in what appears to be perpetual motion as the circle, somehow, begins to be kicked about by its contact with the polygon.
Several months ago, I was convinced that I might have found a perpetual pendulum / rotor using such an arrangement. After deeper analysis we all realized it was a glitch in the WM2D program.
Below is a screenshot of my "OU pendulum / rotor" device that was only running due to the glitch.
ken
Try to avoid having a circle up against or resting on a concavity in a polygon in WM2D models. This arrangement can result in what appears to be perpetual motion as the circle, somehow, begins to be kicked about by its contact with the polygon.
Several months ago, I was convinced that I might have found a perpetual pendulum / rotor using such an arrangement. After deeper analysis we all realized it was a glitch in the WM2D program.
Below is a screenshot of my "OU pendulum / rotor" device that was only running due to the glitch.
ken
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- Beware of WM2D models with circles contacting polygons...
On 7/6/06, I found, in any overbalanced gravity wheel with rotation rate, ω, axle to CG distance d, and CG dip angle φ, the average vertical velocity of its drive weights is downward and given by:
Vaver = -2(√2)πdωcosφ
Vaver = -2(√2)πdωcosφ
re: Low Friction Materials, and WM2D Friction Question
Ken,
Was the bouncing of the circle in your pendulum sporadic, or was it smoothly gliding along the surface?
Can you elaborate a bit more. It's not clear to me what the nature of the glitch is. How do I identify it?
Bottom line is this: I just want a smooth curved surface interaction - maybe I should try the curved slots, but I've not had luck figuring out how to shape the curves how I want them.
Thanks,
Randall
Was the bouncing of the circle in your pendulum sporadic, or was it smoothly gliding along the surface?
Can you elaborate a bit more. It's not clear to me what the nature of the glitch is. How do I identify it?
Bottom line is this: I just want a smooth curved surface interaction - maybe I should try the curved slots, but I've not had luck figuring out how to shape the curves how I want them.
Thanks,
Randall
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ken_behrendt
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re: Low Friction Materials, and WM2D Friction Question
Randall...
The bouncing action of my circles with the polygon was a subtle, hard to notice thing. But, as a result of it, the circle would get a little bit of a kick with each contact that then raised its kinetic energy. In order words, the contacts were adding kinetic energy to the system which it should not have had.
Apparently, this problem only happens when you use the polygon tool on the left side of the WM2D Workspace. But, it does not happen if you actually make a polygon using the Properties box to supply the X and Y coordinates on the surface of the polygon. Also, one can "import" polygon shapes from other CAD programs that will not have this glitch in them. You will need to do some experimenting until you find what proceedure works best for you.
Using the curved slot tool requires some practice, but it can be used to make some interesting shapes that can restrict the movement of another part to following a curve and the other part, if it is a circle, will not pick up any unwanted extra kinetic energy in the process. I made extensive use of closed curve slot joints in the model I made of Sanjay's wheel.
ken
The bouncing action of my circles with the polygon was a subtle, hard to notice thing. But, as a result of it, the circle would get a little bit of a kick with each contact that then raised its kinetic energy. In order words, the contacts were adding kinetic energy to the system which it should not have had.
Apparently, this problem only happens when you use the polygon tool on the left side of the WM2D Workspace. But, it does not happen if you actually make a polygon using the Properties box to supply the X and Y coordinates on the surface of the polygon. Also, one can "import" polygon shapes from other CAD programs that will not have this glitch in them. You will need to do some experimenting until you find what proceedure works best for you.
Using the curved slot tool requires some practice, but it can be used to make some interesting shapes that can restrict the movement of another part to following a curve and the other part, if it is a circle, will not pick up any unwanted extra kinetic energy in the process. I made extensive use of closed curve slot joints in the model I made of Sanjay's wheel.
ken
On 7/6/06, I found, in any overbalanced gravity wheel with rotation rate, ω, axle to CG distance d, and CG dip angle φ, the average vertical velocity of its drive weights is downward and given by:
Vaver = -2(√2)πdωcosφ
Vaver = -2(√2)πdωcosφ
re: Low Friction Materials, and WM2D Friction Question
Ken,
Thanks a bunch. That cleared things right up for me. Now, I need a free CAD program to so I can try to import the shape I want and give it a go.
If anyone knows of one, please post a link.
Thanks,
Randall
Thanks a bunch. That cleared things right up for me. Now, I need a free CAD program to so I can try to import the shape I want and give it a go.
If anyone knows of one, please post a link.
Thanks,
Randall
re: Low Friction Materials, and WM2D Friction Question
Search posts by author Tinhead he posted up a free CAD program IIRC a month or two back.
Re: re: Low Friction Materials, and WM2D Friction Question
Here you go -> http://www.emachineshop.com/download/index.htmrmd3 wrote: Now, I need a free CAD program to so I can try to import the shape I want and give it a go.
There are more out there, but this one is really easy to use. Starting a drawing it will ask you to define a machine type, select wirecutting or lasercutting. Otherwise you can ignore that message :)
Cheers,
Rainer
re: Low Friction Materials, and WM2D Friction Question
Randall
You made me think, but I can tell you that the lowest friction between two materials would be a piece of steel and a bearing.
Yes this has been the search for hundreds of years.
Steel sliding on steel!
Even though you can hardly measure the amount of wear and friction, it still is happening as the bearing turns
The other is an air bearing, but I am not sure if you count air for an answer, but something to think about.
Thanks for the question
You made me think, but I can tell you that the lowest friction between two materials would be a piece of steel and a bearing.
Yes this has been the search for hundreds of years.
Steel sliding on steel!
Even though you can hardly measure the amount of wear and friction, it still is happening as the bearing turns
The other is an air bearing, but I am not sure if you count air for an answer, but something to think about.
Thanks for the question
JB Wheeler
it exists I think I found it.
it exists I think I found it.
re: Low Friction Materials, and WM2D Friction Question
Randall
Another company offers a demo version called "Alibri Design" A Google search at
http://www.google.com/search?ie=UTF-8&o ... bre+Design will lead you to downloading and licencing, There is no fee for the demo, but expect to get email from them occasionally wanting you to by the full version.
Ralph
Another company offers a demo version called "Alibri Design" A Google search at
http://www.google.com/search?ie=UTF-8&o ... bre+Design will lead you to downloading and licencing, There is no fee for the demo, but expect to get email from them occasionally wanting you to by the full version.
Ralph