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Member Since 08 Nov 2001
Offline Last Active Oct 13 2016 01:00 PM

Posts I've Made

In Topic: Spring couplings

13 October 2016 - 12:59 PM

If what you are really interested in is a detailed model of a tonewheel organ, why don't you just measure the movement of the gears in an actual device? High frame rate video and audio acquisition doesn't seem difficult. You can also experiment with replacing the springs in the photo.

Heh! Exactly that had long occured to me, sure it would be nicer to only replicate the action where it happens, not all the stuff before that.
But for that, you'd have to actually have such an organ. Do you have an idea how monstrous those things are? And not exactly cheap either. If I had a house, I might buy one, but I haven't ;)

In Topic: Spring couplings

12 October 2016 - 12:51 PM



connected by such a spring to the other axle


You mean like a big rubber band?  That would work like a torsional spring.   The motor would twist it up (apply torque), the springiness would untwist it,  applying torque to the connected axle. Assuming the backward turning resistance of the engine always exceeded the turning resistance of the axle, the spring would turn the axle, not the motor.


Coil springs use F=k*s. I don't recall the analogous formula for tortional springs,. You can look it up. So your engine will input a torque into the spring system, then your spring will output a torque to the axle.


Eventually it should hit a steady state where the spring has "loaded up" and is essentially a solid link for purposes of forward thrust over smooth surfaces. IE torque in = torque out.



Ah, silly me, I could have included illustrations.



I only now discover the two springs on the left, holding the disc on the motor together with what I guess is a flywheel - yet another coupling I overlooked.
I was initially talking about a coupling like on the center right of the image. You can see (red arrow) the 90° bent end of the coil spring stuck through a hole in the small disk, so rotational force will turn that spring. The whole apparatus has several of couplings like that, but since that's the main axle, this one is especially big.


As for that funky motor, here's a gif of how it works:
Pay attention to the flipping of the poles of the electro-magnets. A 1-phase sine voltage is applied, with opposite polarities, to those two coils, i.e. the fields repeatedly flip. The fixed magnets on the rotor are relatively low in number, you can imagine how that thing will output not a constant,  but rather "pulsating" torque. (it can't even start by itself, needs a starter motor)
EDIT: Also, this is driven directly by mains voltage frequency, which also has some fluctuation.

What is all this?
It is a electro-mechanical, "tonewheel" organ (e.g. Hammond).
I am currently going along all routes which I suspect provide reasons for why my emulation sounds so much more sterile than the real thing.
There are groups of {2 tonewheels sharing one axle}, and each tonewheel is coupled by an own spring to that axle. Then, each of those 2-tonewheel-axles is coupled by 2 gears with a certain ratio to another axle, which is in turn coupled to the motor by that big spring. (or maybe it's even more complex, I haven't seen a complete system drawing, only pieces here and there)
You see, the whole system is quite a bit more ;) So in my initial post I started with subsets of it to start getting the hang of that first.


Well, there has to come some variation from somewhere in there, to produce that lively sound (and I don't mean the rotational speaker cabinet).
I suspect that all that multiple spring loaded monstrosity has some minute variations in the movement of each single tonewheel (each one has different mass and spreading of that mass into space, so fluctuations in torque may not make them react exactly the same on their springs).
Maybe I'm wrong and the effect of this is so minute that it does not actually contribute to the sound, but I'd like to explore this :-)

In Topic: Nintendo DSi game for 1200 points - please recommend :-)

28 June 2016 - 03:06 PM

Okay, so I realized when starting the dsiware shop on my DSi, in the premium list, there isn that much. About 80 games.

I ended up downloading "Elite Forces: Unit 77", looks the most like a "real game" coming from a pc gamer ;)
Now I have 400 points left for really small stuff ^^

In Topic: WP 8.1 ePub reader with scrolling

27 June 2015 - 06:44 AM

Apparently, FBReader cannot open ebooks from sdcard yet, so it's useless.


But your mentioning the infamous bloatware producer Adobe made me look whether there might be a mobile version of Foxit reader - and indeed there is!  (for WP8, Android, iOS).

It works as expected.

In Topic: Mouse axes sensitivity, forcing unwilling game ?

27 June 2015 - 06:39 AM

Okay, so the software for the G700 does this, but apparently not storable as profile (the X / Y sensitivity distinction), only globally, which is quite an annoyance but works...
Apparently the older logitech software (forgot the name) was better in that regard, but it doesn't recognize my mouse.