water analogy- a simple calculator

Rich Grise:

In Italy the best selling mopeds in the '70s and '80s where the Bravo and Ciao, both equipped with V belt "variatore". I think that modern scooters' transmission is still made that way, but I never "opened" one.

he

r in

some

r

Yeah sure that's how I drive a car.... If my car went back and forth and I wanted to stop it, I'd apply the brakes at the turn around point where the velocity is zero.... I guess I'm just saying I don't get the (hic) analogy.

x,

n r m

Sure. If there was energy loss (from say the thread sticking?) right at the turn around point wouldn't the amplitude have to undergo some sort of 'step' change in amplitude? The energies all in the spring at that point. I'm not sure what the thread is at one point we were using 'spider' wire. (use for fishing.) It's rubbing against an 1" diameter Al rod, There are two strings each touching for maybe 45 degrees of the circle. We first tried a complete wrap of string and that was much to much friction. I think there's ~100 grams hanging on each string.

me

I was looking at some other data today. The amplitude looks a lot more linear.

We 'attempt' to do that too. I've never tried fitting the data, but at least it's different than exponential. We put two ~2 foot long

1/4"diam. aluminum tubes through the rotor with paddles one the ends. ... I was just thinking one way to test the v**2 depenedence would be to drive it and look at the response.

Yeah, feel free to 'resist' me any time.

Thanks, grasshopper.

t- Hide quoted text -

Ther was one thermal simulator, called Sauna, that was based on connecting an array of dots in 3-space with (thermal) resistors in a cubic matrix, and caps to ground, and then running a Spice-like sim.

I've used Spice to simulate thermal systems. This works pretty well:

ELECTRICAL THERMAL

1 amp 1 watt 1 farad 1 gram aluminum 1 volt 1 degree C 1 second 1 second 1 ohm 1 degC/watt

John

They were doing some pretty sophisticated thermal analysis on 100-chip, 1kW and higher, packages.

1 henry 1 ????

;-)

ng?

My car is a 2002 Corolla. But I do have a cool little ride'm lawn mover. You have two levers, that connect to the back wheels. The front wheels are like those on shopping carts and free turn where they want. The levers are like those on a tank. The clutch mechanism is ''tangentail' spheres. (I certainly can't describe it.) But it's a dang fast way to cut grass in summer. (My son's been driving it since before I'm free to mention.)

We've finally got a bit of snow here. Two feet up the east coast and we only get six inches, sigh.

George H.

ws in

ll

n n t

Yeah, I was thinking about zeners (which I think John F mentioned) if they are low voltage so it's kinda the same in both directions.. then at high voltage there's 'always' a zener+diode drop which looks like my requested constant amplitude decrease.

Does that work? (I've got a growing list of 'fun' useful measurements to do... )

George H.

Ahh it's nothing but shameless advertizing.

You've got to scroll down till almost the end, Look for Damping.

n r

Hmm, this all looks like 'work' to me. Mind you I mostly enjoy going to work. Do you do electronics for a living?

Digital sure.

George h.

in

Ya, I have no idea how to make it all work.

George H.

ansfer

.

Yeah I do it with one resistor and one cap.. (Well I usually break the resistor in half.)

When I have to explain thermal circuits to people I love to use the 'electronic' analogy. (I'm not sure it helps them, but it's how I understand it.) Of course capacitors don't have phase changes.

Oh the Farad is equivalent to the heat capacity. Joules/deg K. (I think that's right. RC is time, seconds in both 'units')

George H.

Deceleration of a braking car is due to sliding friction, but for a given normal force on the brake pads, the deceleration isn't constant. I'm not sure why that is, but it clearly shows that the coefficient of friction model isn't always adequate as the speed goes to zero.

You wouldn't get a noticeable discontinuity on each start because when the stiction lets go, the rotor accelerates smoothly from 0. There might be something visible when it stops each time--another of those square-root decelerations.

Cool. As I said, it's a great demo. Nothing like a bit of data to discourage pontification.

;)

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal
ElectroOptical Innovations
55 Orchard Rd
Briarcliff Manor NY 10510
845-480-2058

email: hobbs (atsign) electrooptical (period) net
http://electrooptical.net

transfer

Unfortunately, most useful thermal systems are diffusive, unlike lumped electrical circuits. And the diffusion is usually among nasty

3D shapes. So the modeling is ugly finite-element stuff, basically a many-element 3D hairball of resistors and capacitors.

Interestingly, there is no thermal equivalent of an inductor. So thermal systems don't ring or oscillate, unless you sneak in some nonlinear mechanical or transport phenomenon.

I wish I had some nice little thermal resistance calculator, even a 2D one.

John

We don't have grass. I hate grass.

There's only, officially, 48" of snow on the ground in Truckee. But some of the mounds tossed up by the snow plows are easily 12' high. And the year is young!

John

Well, the Farad is the unit of capacity, which we geeks call capacitance. ;-)

Cheers! Rich

apart from the fact that it's elastic and behave more like a long straight wire with lots of parasit capacitance it's a good analogy, you can even make a boost converter based on it.

--
?? 100% natural

George Herold:

Why scroll? :-)

I guess so.

I don't even go. I live in it.

Just power and interface for my embedded contraptions.

That's how I know to do it. I wish I was able to do it in a more elegant way, but my knowledge and "time to market" don't allow for better solutions.

;-)

-- You can't fix stupid. You can't even put a band-aid on it, because it's Teflon coated.

Rich Grise:

Someone proposed, for inductance, a turbine with a flywheel. What about a second turbine in the "inducted" pipe?

Coupled crosstalk is easier, since a higher pressure in one hose will expand it, so that it will squeeze the other one, that runs parallel to it.

John Larkin:

:-)

The hydraulic analogy is also useful with switchers, to show that it is possible to divide the content of one bucket in two buckets, so it is possible to make a divide-by-two buck converter with two capacitors, a few switches and no inductors. But the efficiency, given the fact that we lowered the top half of one bucket to ground, wasting most of the energy, would be lousy.

resistance.

--
That's like saying that you don't understand analogy.