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A test rig for simple circular NdFeb configurations

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Sun Nov 12, 2006 8:40 pm PostPost subject: A test rig for simple circular NdFeb configurations
avid_engineer
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I have begun constructing a simple rig for testing various configurations. As you can see in the progress pics i intend to keep it fairly simple for the moment.

I have currently built a mild steel base and 1 bearing mount for the arm, this device will hold a single arm for testing purposes only. It was my intention to use some bearings i already had in the workshop, but at the last minute i decided to try the platter mount out of an old hdd instead. It seems to be very well built and low friction - these things are designed for over 7000rpm Smile

Another thought ocurred to me, that i might be able to use this motor as a crude way of measuring rotational speed (measuring millivolts) or applying a small current to the motor to overcome magnetic bumps.

The pictures show a single bearing and mounting plate (machined for accuracy). I intend to build another similar mount to be placed opposite. Also pictured are two types of Neodymium i intend to use, 10mmx10mm cylinders and 25mmx18mm cylinders with hollow core for mounting.

I intend to machine the arm out of aluminium or delrin, and have two discs which can be used to clamp magnetic configurations between them to form the rotor. Stator magnets will have to be positioned by some other means.... probably an extension of the steel base, still thinking about that.

What would be really great is if someone with experience using the type of angle encoder Steorn are using, could provide me with details of how to use that equipment... i would definitely invest in a reasonably priced unit if i knew how the data aquisition worked. Perhaps a torque sensor would be more usefull though, seing as though we are trying to measure the strength of the magnetic effect. Cost is always an issue with kit like that however Sad

Whatever the case, with 1 arm I need a way of measuring the fields effects. Any electronics buffs here? or other suggestions?




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Sun Nov 12, 2006 8:44 pm PostPost subject:
avid_engineer
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BTW. Feel free to poke holes in my ideas / design. I would welcome any ideas people have at this point, hope the pictures are clear, and my description reasonable.

If anyone has questions about the rig, ill try and answer with diagrams. It's all in my head right now, apart from a couple of rough sketches.
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Mon Nov 13, 2006 12:51 am PostPost subject:
clovis ray20
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i would love to see those sketchrs
when you get time to do them.

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Mon Nov 13, 2006 2:45 am PostPost subject:
babcat
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It looks great to me! It's a fantastic start. Great work!

This is an idea of mine that might sound wierd, but I will give it anyway. Are there any cheap mechanical "arms" that you could mount on the stator that you could move around into basically any position and then lock into place somehow? I mean something like the neck of those desk lamps that let you bend them in all kinds of wierd positions. Something like that would be flexible enough for you to adjust easily, but then you would just need a way to secure it in place each actual experiment.
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Wed Nov 15, 2006 10:14 am PostPost subject:
babcat
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How is the test rig coming along?
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Wed Nov 15, 2006 12:54 pm PostPost subject:
avid_engineer
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I havn't had much time since the weekend to work on it. I've made a start on the second bearing mount and will machine it and heat fit the bearing when i get the time (probably this weekend). Next step is to make a start on the arm, i intend to turn one out of aluminium and devise a connection to the HDD spindle motor out of delrin.

A couple of thoughts i have had...

1. Change the framework design slightly so that some threaded bar that can be used to mount and adjust stator magnets.

2. Manufacture the HDD spindle mount so that weight can be added, creating a flywheel effect if desired for the test setup.

I hope to make more progress this weekend, and ill post pics accordingly.

BTW. Nice idea about the flexible arms, not sure if they would be stable enough for some test setup's though.
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Wed Nov 15, 2006 6:11 pm PostPost subject:
avid_engineer
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Evenin peeps,

I have a small request i was hoping somebody could help me with. It's with regards to the shaft (angle) encoders and sensory hardware that Steorn are using.

As mentioned before, i would love to start experimenting with some shaft encoders and/or torque sensors - whatever i can get my hands on for reasonable cost. Shaft encoders are easily and cheaply available on eBay, but they are useless without some kind of data aquisition hardware / software.

Steorn have posted on their forum that they are using the National Instruments PCI-6281 DAQ card interfaced to their sensors. Find the spec here...

http://sine.ni.com/nips/cds/view/p/lang/en/nid/14685

At 1000 they are way outside the budget of my experiments!

Im just thinking ahead a little, and considering the possibilities of a small electronics project utilising a PIC of some kind to interface encoders with a PC via the serial port (for example). Problem is that my knowledge of electronics is not currently up to this sort of project and i was hoping to find some info on the net.

Hardware aside, i am quite a competent software developer and could come up with a software solution fairly rapidly... just need the data / pulses from the encoder.

Ideas anyone? Im gunna keep scouring the net, but it's not been promising so far.
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Thu Nov 16, 2006 12:23 am PostPost subject:
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You can pickup a basic stamp at any radio shack for ~100 USD. Though I don't know if it'll be up to task.

www.parallax.com
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Fri Nov 17, 2006 6:22 pm PostPost subject:
avid_engineer
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Ok, so i've been thinking about the rig a lot this week (more than i should be, lol). I decided to do some concept drawings before I continue just to build on the design a bit. No point in rushing to build something which turns out to be useless when we learn a little more from Steorn.

The images are 1024x768 so ive linked to them rather than posting directly. Please feel free to modify and repost if you have any idea's on how to improve or add to the design...

http://www.fictionary.co.uk/images/rig/framework.gif
http://www.fictionary.co.uk/images/rig/arms.gif

BTW. Thanks drichardson for your PIC suggestion, i've been reading a little about what they have to offer.
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Fri Nov 17, 2006 8:45 pm PostPost subject:
WhiteLite
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Excellent stuff avid! It's good to see you're taking this seriously. I really look forward to how you get on and keep us posted. Cool
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Sat Nov 18, 2006 8:45 pm PostPost subject:
DaveHoward_
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[quote="avid_engineer"]Evenin peeps,

At 1000 they are way outside the budget of my experiments!

Im just thinking ahead a little, and considering the possibilities of a small electronics project utilising a PIC of some kind to interface encoders with a PC via the serial port (for example). Problem is that my knowledge of electronics is not currently up to this sort of project and i was hoping to find some info on the net.

Hardware aside, i am quite a competent software developer and could come up with a software solution fairly rapidly... just need the data / pulses from the encoder.

Ideas anyone? Im gunna keep scouring the net, but it's not been promising so far.[/quote]

Hi avid_engineer,

First, nice work there both on physical parts and drawings.
Second, re: DAQ cards,

This maybe of interest including the basic connection diagrams
they go around 300-350 USD, so with GBP/USD around 1.85 it should retail you less than 200 GBP
http://www.sensoray.com/html/421data.htm

These are also nice, pretty reliable for entry level multyfunction:
http://www.omega.com/ppt/pptsc.asp?ref=OMB-DAQBOARD-500&Nav=dasd01

A note: It maybe easier to have more input from readers if you could be more specific on what you are aiming to do, eg. test a specific principle, replicate an existing design.. etc.


I hope the above helps.
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Sun Nov 19, 2006 3:04 am PostPost subject:
clovis ray20
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a e
I'm glad you have taken the lead, and have gotten us started on the road to having an working model
in the near future . keep up the good work. if i can help with research work or anything else just say it and i'll do my best.

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Sun Nov 19, 2006 11:42 am PostPost subject:
babcat
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I must admit you guys are far beyond my mechanical or physics skills. I admire the work all of you are doing, but I know nothing about torque sensors or other such devices.

I have said this on other threads, but my hope is the flash presentation (which is supposed to be updated Monday) will give enough information to help you go in the right direction with your testing rig.
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Sun Nov 19, 2006 1:42 pm PostPost subject:
avid_engineer
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Thanks for the links Dave, i will continue to read up on the encoders and DAQ's your links are very helpfull indeed.

While i would like to be more specific on the prinicples involved in my tests, at this stage i really have no more insight than any of us here do. Therefore my main aim is to design a rig which can be made flexible enough to test a variety of configurations and i think that the key to this probably coming up with an inovative way of mounting the stator / rotor magnets which allows for simple adjustments of the magnetic configurations without remachining the mount every time.

I am learning on the fly with this project, so suggestions are valued greatly. So far i think the rig has potential, but given the nature of the stop start movement in Steorns tech i guess at some stage electronics will have to become involved. That means stepper motors, stepper controllers, torque sensors and shaft encoders will eventually be required to observe any kind of OU effect. All of which i have no experience with, and will rely heavily on eBay for parts due to cost.

From all i have read, i gather Steorn's OU claim is far from straight forward. I am not really expecting to have a machine which runs itself in its mechanical entirety. But getting the mechanical problems out of the way seems to be the first step. Then we can experiment a little with simple arrangements and move onto more advanced measurements when the electronics stage of this project has been worked out (and when i can afford to, lol).

It would appear that we will get the final word from Steorn on monday regarding their test rig's. Lets hope this is enough to keep us from straying off track to much Smile
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Sun Nov 19, 2006 8:38 pm PostPost subject:
avid_engineer
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I've been thinking about stepper motor control systems for the test rig this evening and am having trouble picturing how this might work, perhaps someone can help me clarify the mechanics...

First lets check out this picture to get a clear view of whats happening.



We now know (thanks to TylerD1) that we have a Mdrive17 stepper motor, attached to a 3:1 ratio pulley, driving a 50:1 gearbox which is somehow attached to the measurement arm to provide control over its movement. Sean stated as an example, that for every 1 joule of energy applied to the arm it should produce 3 joules (approx) or a net result of 300%.

So this means that the stepper control system initially puts some momentum into the arm, lets say it turns the arm by 120. The magentic configuration has to provide the force to achieve the remaining 240 of the turn.

If the stepper motor control system was attached directly to the arm itself then any turning force achieved by the magnetic configuration would also have to turn the stepper motor, pulley and gearbox. We dont want this to happen, it is wastefull.

So. Are there any theories or Steorn forum sources that detail how the stepper system drives the arm?
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Sun Nov 19, 2006 8:52 pm PostPost subject:
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Well the stepper motor/arm assembly basically moves the rotor motor into a position and holds it there. While it is held there the torque sensor measures in which direction the rotor is being pushed or pulled. When they have taken that measurement they move the rotor magnet into a slightly different position, (following the natural path the rotor has to take to achieve OU), and measure again. When the path is completed they can add up all the pushes and pulls and if the device is Unity they should all cancel each other out. If they don't then you have Over Unity, (or Under Unity).
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Sun Nov 19, 2006 9:07 pm PostPost subject:
avid_engineer
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Ok so this rig is simply measuring torque, and is not built to actually observe OU in action right? Fair enough, that makes sense.

But i recall Sean stating somewhere that the stopping and starting during a cycle is required in order to transfer energy from one arm to the other. It sounds to me like there is still a degree of control over this process... or have i gone off on one again Laughing
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Sun Nov 19, 2006 9:15 pm PostPost subject:
WhiteLite
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Lol, no you haven't gone off on one Smile

You can use the test rig to measure Over Unity, Under Unity or just simple Unity. Look at the device I made. It has a stop/start cycle, (whether it is OU or not), anything that moves in one direction and then turns 90 degrees has to stop, even if it is just a fraction of a second. The stopping and the starting of the test rig is just so they can get loads of tourqe measurements throughout the whole cycle.
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Mon Nov 20, 2006 10:06 am PostPost subject:
avid_engineer
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WhiteLite wrote:
Lol, no you haven't gone off on one


Ahh good. My mind is a bit like a Steornator, i'd like to think its more productive than not, but may yet be proven wrong Smile

TylerD1 has just updated the images thread with some more great pics, so i think i've got it sussed now. Cheers. Lets hope the new flash info can confirm things for us.
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Mon Nov 20, 2006 2:13 pm PostPost subject:
babcat
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I'm still hoping they will update the flash presentation today. It would really help me feel better after the chaos that went on this morning.
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Fri Nov 24, 2006 9:41 am PostPost subject:
pcstru
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avid_engineer wrote:
Evenin peeps,

Im just thinking ahead a little, and considering the possibilities of a small electronics project utilising a PIC of some kind to interface encoders with a PC via the serial port (for example). Problem is that my knowledge of electronics is not currently up to this sort of project and i was hoping to find some info on the net.

Hardware aside, i am quite a competent software developer and could come up with a software solution fairly rapidly... just need the data / pulses from the encoder.

Ideas anyone? Im gunna keep scouring the net, but it's not been promising so far.


Do a search on PicAxe - they are PIC processors with a preprogrammed BASIC interpreter and can be had for a few quid. They are very easy to set up and use - a basic circuit simply consists of a battery pack, a couple of resistors and a cable for interfacing to the PC. Certainly a good way to get started in electronics interfacing and cheap as chips.
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