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Author Topic: Jhula principle - increase speed by applying brakes.  (Read 55129 times)

xnonix

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Re: Jhula principle - increase speed by applying brakes.
« Reply #15 on: March 29, 2007, 11:36:43 AM »
hey prajna,
I modified the lever and pendulum masses. Now it works with an air resistence of 0.3 or more.

I only take reads of rotational speed in this case.

Have fun!

prajna

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Re: Jhula principle - increase speed by applying brakes.
« Reply #16 on: March 29, 2007, 01:01:09 PM »
@xnonix: That is fantastic. I think that there is further optimisation to do in terms of biasing the system so that disadvantageous forces from the pendulum are reduced and advantageous forces increased.  This is a matter of slowing the pendulum at the correct moment so that its maximum swing force (cetrifugal force) is alligned at 90 degrees or less to the centerline of the counterweight.  It is all a matter of timing.  We have got it half right with the latching mechanism at present.

@bluesgtr44: You are right, gravity does always want to win but here we are playing off centrifugal force against gravity and gravity wants to win over not one but two centres of mass that are tied together and oscillating about each other.  When gravity adds momentum to the system we accept its effort gratefully and when it is being a nuisance we trade some angular momentum to counter its effects.  That is the principle that we are aiming at here.  We are basically swapping energy from one part of the system to another and looking for a formula that will allow us to always move the energy 'uphill'.  That is a matter of timing the maximum centrifugal force so that it is at a useful angle to the overcentre of the two bearings and so that it seldom occurs when the pendulum is more in-line with the axis of the counterweight. That timing can be effected by retarding the pendulum swing at favourable moments.  Sure, we lose a little momentum on the pendulum but we have traded that for applying that force at a greatly advantageous point.

You are also right that there was no (or very little) air resistance in the model but when we are examining the effect on a theoretical basis it is considerably easier to see if we have a net gain of momentum if such energy sinks are removed from the system.  Yes, a practical system will have to take air resistance (and many other factors) into account but a theoretical model is considerably simpler when we leave them out.

xnonix

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Re: Jhula principle - increase speed by applying brakes.
« Reply #17 on: March 29, 2007, 01:15:57 PM »
The latching system is good enough as is now. We know the system is accelerating. We can construct it in real with easy off the shelves parts and no logic.

We need the mechanism (2 of them) of the rear wheel of a bike to construct it.

One aplication for fun:
« Last Edit: March 29, 2007, 01:40:58 PM by xnonix »

prajna

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Re: Jhula principle - increase speed by applying brakes.
« Reply #18 on: March 29, 2007, 02:06:05 PM »
xnonix, I'm very impressed! Nice model. Sure we have acceleration at present and we are using straight mechanics with no other logic but does it not appear to you that there is a heap more energy available from this system if we can increase the asymmetry? We capture a little more of the gavitic effect on one side of our cycle than the other but there is a strong centrifugal force that sometimes adds tons of angular momentum to the system and sometimes robs it of an equal amount. Perhaps there is a simple mechanical way to bias this equasion too.

prajna

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Re: Jhula principle - increase speed by applying brakes.
« Reply #19 on: March 29, 2007, 03:19:16 PM »
xnonix, I've taken your model, dropped it to the floor and reset all the velocities to zero. It still works after that dreadful abuse :) and shows acceleration.

prajna

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Re: Jhula principle - increase speed by applying brakes.
« Reply #20 on: March 30, 2007, 07:07:43 PM »
I've updated http://declarepeace.org.uk/jhula/.  Playing around with new simulations has produced a variety of very interesting models.  Some show chaotic run-away acceleration.  It looks like this is a runner.  Is anyone building out there?  All you need are a couple of bicycle rear axles and some weights.  I would advise adding a braking system as well since this machine does appear to accelerate to destruction.

barbosi

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Re: Jhula principle - increase speed by applying brakes.
« Reply #21 on: March 30, 2007, 07:39:30 PM »
It looks good!
I would encourage you to give some construction details. I'm sure there will be people interested in builing it. It would be valuable for you their feedback.
Regards.

prajna

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Re: Jhula principle - increase speed by applying brakes.
« Reply #22 on: March 30, 2007, 07:47:10 PM »
barbosi, there is nothing particularly important in terms of construction; weights and measurements are not critical.  Some first approximations are avaiable from the WM2D models (you can download a trial version from their website, linked from my page).  The device simply consists of two pendulums, one connected to a fixed point via a one-way hub (like you find as the rear axle of nearly all bicycles) and the second pendulum similarly connected to the first.  I believe that there is enough information on my website for any moderately competant mechanic or engineer to assemble a device.  Obviously some experimentation will be needed to get the best out of any device.

prajna

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Re: Jhula principle - increase speed by applying brakes.
« Reply #23 on: March 30, 2007, 08:33:14 PM »
I'll do it later this evening, mramos.  I look forward to hearing how you get on.  Meanwhile, if you look at the two connections on the model (marked contraint motor) they are actually freehubs (bile back axles).  One connects a pendulum to a frame and the other connects the second pendulum to the first.

prajna

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Re: Jhula principle - increase speed by applying brakes.
« Reply #24 on: March 30, 2007, 09:03:07 PM »
Cool.  Sure it runs in the simulator but the weights are set extremely high to overcome air resistance.  Quite how it will work in practice I am not sure yet.  The first version (really xnonix's version) seems to be a little too stable but we haven't really found out what makes a successful version yet.  Most versions will run if you take air resistance out or increase the weights so that it is not a significant factor.  All we can do is experiment.  I have been experimenting with sims and most of them run; some go completely off the scale and some run even with a really high air resistance (think of it in terms of load on the system).  I can't say what are the optimum ratios, weights or measurements, it will take experimentation in real life to find out.

prajna

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Re: Jhula principle - increase speed by applying brakes.
« Reply #25 on: March 30, 2007, 11:43:53 PM »
Ok, here is a drawing with some labels...

It doesn't even have to be that sophisticated.  Something similar to xnonix's version should be fine.  Experiment with the various parameters (positions of freewheels, weights, lengths.  I will try to get one working with two simple blocks like the counterweight in the first version and xnonix's mod. When building, though, it is likely that people will come up with their own engineering solutions so that they can adjust weight, length etc.

prajna

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Re: Jhula principle - increase speed by applying brakes.
« Reply #26 on: March 31, 2007, 12:48:41 AM »
It rotates around the pivot.  Look at the animation.

prajna

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Re: Jhula principle - increase speed by applying brakes.
« Reply #27 on: March 31, 2007, 02:13:45 AM »
Living in the UK, mramos.  Not visiting the US. Police state. Sick country. UK is bad enough. Don't want to be treated as a criminal and terrorist just for travelling. Sorry. When you dudes get Bush and Cheney to fess up and drop all this international terrorism then I might consider it.

Rosphere

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Re: Jhula principle - increase speed by applying brakes.
« Reply #28 on: March 31, 2007, 06:41:11 AM »
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« Last Edit: April 02, 2007, 02:18:45 AM by Rosphere »

Rosphere

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Re: Jhula principle - increase speed by applying brakes.
« Reply #29 on: March 31, 2007, 06:47:28 AM »
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« Last Edit: April 02, 2007, 02:18:39 AM by Rosphere »