Gear Pump

[steamer]

No worries Derek...We do this stuff...not to make a profit...( god no!....I don't want to think what I've spent on my shop !)  We do it to challenge our minds and have fun....


....stepping down from the soap box....

[steamer]

My Sister put it best Derek.....

Engineering....it's not a profession....it's a personality trait!.....

guilty as charged!


Dave

[philjoe5]

Dave,
Excellent writeup on your gear pump.   There seems to be a lot of undiscovered gold (to me) in this mine.

Cheers,
Phil

[Jo]

My Sister put it best Derek.....

Engineering....it's not a profession....it's a personality trait!.....

Dave

  Sadly true 



Jo

[fcheslop]

Going to have to strip a Faema gear pump now to find out how they lift 3 to 6 feet hundreds of times a day .These pumps are only about 35mm dia so if you want any pics just ask
Not been critical just curious

[steamer]

Going to have to strip a Faema gear pump now to find out how they lift 3 to 6 feet hundreds of times a day .These pumps are only about 35mm dia so if you want any pics just ask
Not been critical just curious

Don't know...would like to see that myself...got a part number?....

Every reference I have says to put the gear pump at the bottom of the system, and in several commercial products, I have done so...with success...the biggest lift being a few inches...as these pumps wear, their performance goes down pretty quickly....both intake and delivery.


Dave

[fcheslop]

Hi Dave, fully agree when Faema changed from Peristaltic pumps to geared I thought ooppps and the milk box can be under counter and the pump is in the machine not in the refrigerated box.The reason for the change was not solely cost it also improved the quality of the drink
Recently changed a pump that had done 185,000 drinks delivering 350ml per vend then the pump is reversed to blow out the line.
Not a great volume for a pump I know but it was the motor that had gone.
Part No 533-198-900 Faema Grand Italia X1/X2 or X54
I will strip one over the week end and put some pics up on another thread to save taking this one of track
cheers
 

[Brian Rupnow]

My Sister put it best Derek.....

Engineering....it's not a profession....it's a personality trait!.....

guilty as charged!


Dave

I like that quote.---Brian

[Brian Rupnow]

Here we go with the pump housing. Do NOT copy this file. It is preliminary and may change. Updated drawings will be published here at completion of project. What do I see as the problem areas?--Well, two actually, both concerning the cavity for the gears. That .297" rad. gives a diameter of 0.594". (The o.d. of the gear is 0.583". ) So--the holes at each end will have to be bored--There is no standard endmill to give that, So--that and the fact that the bottom of that slot will have to be very smooth.

[Brian Rupnow]

My plan at the moment, concerning the gear cavity is to set the material up in my milling vise with a pair of parallels under it for some clearance, drill and ream the two 0.25" through holes and set the X axis mill stops up so that I can crank the table back and forth between the two hole positions without worrying about reading the dials all the time. Then I will use a 4 flute 1/2" diameter end mill and plunge cut to .375" deep at the center of each of the previously drilled and reamed 1/4" holes. Then I will back the cutter up vertically until it is just clear of the material, then lower it in .010" to .015" increments and crank the table back and forth between the pre-set stops until the material between the two 1/2" holes is removed. Then I will make a steel "test shaft" about 1" long with the major diameter at 0.594" diameter and 1/2" at one end turned to 0.25" diameter.---Are ya with me so far? --Then I set up my boring head and poised over the center of one of the holes, keep dialing it larger and larger and take full depth 3/8" plunge cuts until I reach a point where my "test shaft" will fit into the 1/4" reamed hole and fit into the bored hole. then I will back the boring head up until it clears the top of the material, move the table up to the next table stop and fully plunge cut the other hole at the same setting. Then back the boring tool up vertically again to clear the material, advance it in .010" to /015" increments, and "walk it back and forth" between the two holes to remove the material between the holes, to the point where the slot matches the dimensions on the drawing.  If the bottom of the slot isn't nice and smooth, I will chuck up a piece of .594" diameter steel shaft and "burnish" the bottom of the slot with a bit of 600 grit lapping past.--Does that sound like a reasonable approach?

[b.lindsey]

Sounds reasonable to me Brian. The only thing I might do different is to leave .003-.005" in the bottom so that on the last (full depth) cut with the boring head, as you walk it across the cavity it would help clean up the bottom. May not be necessary though if you get a good smooth finish with the bottom of the end mill to start with. Just see how it looks and adjust accordingly.

Bill

[Jasonb]

Brian, I did similar on my Nemmet but rather than drop the boring head and go back & forth I wound it 0.050 to the side, plunged, wound, plunged etc. The very small sccallops left on the side were not a problem.

[Brian Rupnow]

Well Sir!!! I'm happy with this!! Somebody on another board insisted that a .594" hole was too big when running a gear .583" diameter. I'm not sure if I believe him or not, but I tightened the hole up to .587" diameter. Laying in the foreground is the "test shaft" with a large diameter of .587" and a small diameter of 0.25". I plunge cut the cavity with a four flute 1/2" endmill (after putting the 1/4" reamed holes through it.) Then I snuck up on it with the boring head until I could just get the big end of the test shaft into the hole. Then I traversed 0.5" to the other hole center and plunged full depth again at the same setting. Then I took a series of full depth plunge cuts all the way over to the first end in .050" travel increments , as Jason suggested. The test shaft fits in there, snug as a mouse's ear!!

[Brian Rupnow]

So---That's enough silliness for one day. The pump body is finished. The brass tubes are just pushed in by hand to make a pretty picture. It don't look like much, but that simple pump body has used up most of my day. Maybe I'll cut the gears tomorrow. I wanted to cut the cavity in the pump body first, so that I can make the length of the gears "to suit".

[philjoe5]

so that I can make the length of the gears "to suit".

Are you referring to the center-to-centerdistance here Brian?  It will be interesting to see how closely the gears need to mesh for the pump to work. 

I'm following with great interest

Cheers,
Phil