I have 3 concepts that I would like to present for your consideration. I'm specifically looking for constructive criticism.
This is the first concept. Hopefully, self-explanatory but I can describe the action in a follow-up response.
So when the left-hand side descends around the little wheel, it slides along that slope causing the opposite side to go out?
Quote from: noonespecial on May 08, 2008, 08:55:41 AM
I have 3 concepts that I would like to present for your consideration. I'm specifically looking for constructive criticism.
This is the first concept. Hopefully, self-explanatory but I can describe the action in a follow-up response.
What are you trying to make it do?
lol I am trying to make it swing like a pendulum, sorry if I?m talking nonsense, I had no sleep last night :p
It looks an interesting device, but you see how the weights are attached, even though they are more to the left, I am not sure weather that will make a difference because no matter where that weight is, it is still attached to that very spot, also the bottom weights might have to be slightly more heavy in order to keep those weights in position...
Sorry....I had to go out for the day....
I've removed the center wheel and connecting rod because they were just there to show the transfer from lever action to rotary motion.
Overview:
There are 2 cylindrical weights...A and B. I've made them out of 3/4" copper tubing filled with solder. They sit on platforms that are allowed to tilt about 5 degrees left and right above the main beam. Both platforms are tied together by the lower rod beneath the main beam. There is 6" of travel from left to right. Weight "A" is 3" further out from the pivot point and weight "B" is 3" closer. There is also a counterweight hanging under each pivoting platform that is fixed to the platform.
Function:
As shown, weight "A" will fall lifting weight "B". The counterweight beneath weight "A" is pushed outward by the falling weight and the angle on the base. This in turn tilts both platforms to the right (they are tied together). Weight "A" rolls inward 6" and weight "B" rolls outward 6". Weight "B" is now further from the central pivot point than weight "A" and a mirror image of the previous action occurs.
Quote from: noonespecial on May 08, 2008, 08:55:41 AM
I have 3 concepts that I would like to present for your consideration. I'm specifically looking for constructive criticism.
This is the first concept. Hopefully, self-explanatory but I can describe the action in a follow-up response.
I see what you're trying to do, but if your pivots are free to pivot, then moving the balls to the other side of the trays does NOT alter the balance and tip the contraption in the other direction.
On the other hand, if you glue the pivots so that they can't pivot, then moving the balls DOES alter the balance and tip the machine, but then the trays will tip, and moving the balls back will require energy.
Quote from: Mr.Entropy on May 08, 2008, 05:08:54 PM
Quote from: noonespecial on May 08, 2008, 08:55:41 AM
I have 3 concepts that I would like to present for your consideration. I'm specifically looking for constructive criticism.
This is the first concept. Hopefully, self-explanatory but I can describe the action in a follow-up response.
I see what you're trying to do, but if your pivots are free to pivot, then moving the balls to the other side of the trays does NOT alter the balance and tip the contraption in the other direction.
On the other hand, if you glue the pivots so that they can't pivot, then moving the balls DOES alter the balance and tip the machine, but then the trays will tip, and moving the balls back will require energy.
That's correct. I think you responded just before my last post.
Think of the tray and counterweight arm as one assembly. The counterweight is sized so that when weight "A" is at its furthest point either left or right, the tray (and arm) maintains a 5 degree angle throughout the arc of motion.
IMO, both A & B 'T' bar pendulums will move to their respective balance points i.e. where their individual CoM/CoG is beneath their pivot - because they are linked via a parallelogram arrangement they will find a position of equilibrium between them - there will be some movement of the main teeter-totter from inertia re: action & reaction, & the T bars will continually adjust their balancing points below their pivots - the CoG of the whole arrangement will seek & find its lowest Potential Energy [it only initially moves because you have arranged it in a favourable position, to start with more PE than it would otherwise have] - when the momentum of seeking the lowest PE is used up by friction & windage etc the apparatus will stop its dampened swing & stand stationary with its CoG directly beneath the center pivot.
As far as I can tell the arrangement will act as an dampener of movement [leading to stability] rather than creating a constantly unstable device [leading to instability - an un-natural state].
I agree with Fletcher's opinion (as usual :--) , although I would have stated it some what different.
The two pendulums are symmetrical pinned to the cross arm. I recommend you study the principles and effects of the:
http://en.wikipedia.org/wiki/Roberval_Balance http://www.lhup.edu/~dsimanek/museum/roberval.htm
Ralph
Quote from: rlortie on May 08, 2008, 05:59:14 PM
I agree with Fletcher's opinion (as usual :--) , although I would have stated it some what different.
The two pendulums are symmetrical pinned to the cross arm. I recommend you study the principles and effects of the:
http://en.wikipedia.org/wiki/Roberval_Balance http://www.lhup.edu/~dsimanek/museum/roberval.htm
Ralph
Hi Ralph,
Thanks for the reference. However, unless I'm missing your point my mechanism CAN tilt whereas the balances in the reference article cannot. The traditional balances shown are pinned in the center of both arms but mine only on the main beam. So I don't see the similarity.
Quote from: fletcher on May 08, 2008, 05:34:48 PM
IMO, both A & B 'T' bar pendulums will move to their respective balance points i.e. where their individual CoM/CoG is beneath their pivot - because they are linked via a parallelogram arrangement they will find a position of equilibrium between them - there will be some movement of the main teeter-totter from inertia re: action & reaction, & the T bars will continually adjust their balancing points below their pivots - the CoG of the whole arrangement will seek & find its lowest Potential Energy [it only initially moves because you have arranged it in a favourable position, to start with more PE than it would otherwise have] - when the momentum of seeking the lowest PE is used up by friction & windage etc the apparatus will stop its dampened swing & stand stationary with its CoG directly beneath the center pivot.
As far as I can tell the arrangement will act as an dampener of movement [leading to stability] rather than creating a constantly unstable device [leading to instability - an un-natural state].
Thanks for the positive critique. I have a small confession at this point....I have about 90% of this completed. The change in position of the weights is rather violent and I'm actually
looking for a way to dampen the change in position. I think if you study this a little more you will see that it would almost impossible to reach an equilibrium point. Both weights would have to somehow roll to the center point of both trays at the exact same time and stay there.
I was going to suggest you build it - it seems easy enough - let us know what you discover - the balls will find & stay on one side [no favoured bias if constructed acurately] but the system CoG will be directly beneath the center pivot in the mechanism balanced position i.e. no torque position.
Felt in the bottom of the containers may dampen the oscillations.
Better still - make it a rolling steel ball in an oil bath [frictional viscosity].