What is it? CXIX

[R.H.]

The latest set of photos has just been posted:

[Leon]

691. Pilot training glasses for instrument training. 694. Outside Caliper 695. Oil Pump. Too big but looks exactly like the one in an A6 Axial GM AC compressor. The old one.

[Leo Lichtman]

"Leon" wrote: 694. Outside Caliper ^^^^^^^^^^^^^ Leon, it has the overall shape of a caliper, but due to the fact that it was hanging on an overhead nail when photographed, some of the details are hard to distinguish. It looks to me like the place where the caliper opening would be is actually a closed loop. Then, at the other end, where the handle is, is a crank turning a threaded spindle, which could push things toward the loop. But the spindle is too short to close down all the way to the loop.

So, this is my guess--it is slipped over a round thing of some sort, and the crank is used to press in something like a dowel.

[Buddy Matlosz]

693 - hemorrhoid remover

B.

[Ned Simmons]

Gerotor is a contraction of generated rotor. There are both gerotor pumps and motors. The low speed, high torque hydraulic motors (e.g., wheel motors on mobile equipment) are gerotor motors. Some automotive in-tank fuel pumps have cute little gerotor assemblies about the size of a quarter.

I built a couple pieces of equipment for WH Nichols (inventor of the gerotor) shorly after they were acquired by Parker in the mid-eighties, for assembling and testing pumps and motors. The gerotors in the products I worked on were either broached or powdered metal. The only lapping that I'm aware of was on the thickness of the parts. Volumetric efficiencies are much higher than gear pumps.

Simmons

[Leon]

"Perfection In Wood @hotmail.com>" >691: Pilot's IFR training blinder.

Never would have guessed???? I have never had training or seen the glasses but have heard of them and recognized them.

[Lloyd E. Sponenburgh]

Hey! There's a _reason_ they call it "hood time" vs. "'actual' time".

LLoyd

[Leo Lichtman]

"R.H." wrote: 695. Gerotor pump, maybe Leo can tell us a little more about it. ^^^^^^^^^^^^^^^^^^ I know a lot more about it now than I did when I sent it to Rob. I had not heard of a Gerotor pump before. Nor a "hypozykloidal" pump (posted by Nick Muller) either. Is hypozykloidal German for hypocycloidal?

I told Rob (TIC) it was a cylinder for a Wankel revolver.

[Nick Müller]

Yes, thats what I meant. But I was wrong! It is a trochoid and those pumps are known as "Eaton pumps".

HTH, Nick

[Nick Müller]

After having posted that answer and rethinking, I wouldn't like to bet my head about the "trochoid". It might be a hypocycloid. But the eaton pump still stands. (until I am corrected :-))

BTW: The trochoid is known from the Wankel engine.

Nick

[Mark Brader]

According to the definitions at mathworld.wolfram.com, "trochoid" is the generic term for the path traced by a point attached to a circle that rolls along a straight line; trochoids are classified as cycloids, curtate cycloids, or prolate cycloids, depending on whether the point is on, inside, or outside the circle. So it doesn't apply either to this pump or to the Wankel engine, unless there are alternate definitions out there.

From the same source, the generic term for the path traced by a point attached to a circle that rolls along *the inside of another circle* is a "hypotrochoid"; and if the point is on the rolling circle, it is a "hypocycloid". So if we consider the points on the rotor to touch the cylinder it rolls inside, then they follow a hypocycloidal path; if we consider them as not quite touching, it's just hypotrochoidal.

The rotor itself might have a form like a hypocycloid, but since its concave surface doesn't touch anything, there's no requirement for it to have an exact shape.

(By the way, if the rolling circle rolls along the *outside* of another circle, you get an "epitrochoid", and if the point is on the rolling circle, it's specifically an "epicycloid". And the generic term that includes all these curves, which I'd never seen before, is "roulette".)

[Mark Brader]

Of course this applies to the pump, but not to the Wankel engine, whose rotor is convex. To tell the truth, I forgot about that when posting.

[Leon]

For what it is worth, ;~) The pump center piece spins and is driven by a rotating shaft. Notice the key slot to prevent slipping. The outer ring is driven by the inner piece in a path similar to the rotor in the Wankle except that it spins inside a circle instead of an oval shaped cylinder. The outer side of the outer ring moves the liquid.

[Nick Müller]

The rotor or inner "triangle" _is_ a hypotrochoid, the outer part _is_ a epitrochoid.

It doesn't touch anything? There are no seals? Guess you have to rethink that.

Nick

[Norman D. Crow]

Um . . . Leon, beg to differ with your last sentence. The liquid is not moved by the outer side of the outer piece. It is pumped by ports opening into the "open" area of the gearset. Looking @ the picture, one tooth is firmly meshed with the outer ring, with it's opposite firmly against the "dwell" on the outer ring. As the inner piece rotates, it is constantly "opening" and "closing" the volume of space on the two sides. The "opening" part sucks the fluid in through a port on the end of the housing, then the "closing" volume area pumps the fluid out through a similar port in the end of the housing.

[Mark Brader]

Mark Brader:

Ah, never mind, I was just totally wrong there.