Author Topic: Gear Pump  (Read 19869 times)

Offline Brian Rupnow

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Re: Gear Pump
« Reply #30 on: January 10, 2015, 10:04:02 PM »
No, I'm talking about the length of the gear. In a perfect world, the pocket in the pump body would be exactly .375" deep and the gears would be exactly .374" long, so the fluid doesn't bypass between the end of the gear and the pump body. In my world, the pocket is currently .388" deep. and no, I have no idea how that happened, but I suspected that it might. I seem to have trouble machining pockets to a very close depth tolerance. The center distance "is what it is"---(0.5" for these specific gears, as they are 0.5" pitch diameter.) Unless somebody gives me a really good reason not to, I'm going to make the gears out of bronze. I have a whole bunch of weird shaped bronze offcuts. The only bad thing about it is that I will have to change the lathe over to my 4 jaw chuck to "persuade" some of these weird shaped pieces into .583" diameter rounds to cut gear teeth on. It's a pain in the butt changing chucks.

Offline Steamer5

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Re: Gear Pump
« Reply #31 on: January 10, 2015, 11:42:32 PM »
Hi Brian,
 Following along! We have a couple of small gear pumps at work, run  duty standby, on a 3 week, 1 week rotation. I can't remember the dia of the rotary but guessing that they would be 30 mm max. The rotors are rubber. I think we have a couple of "spares" so if you like will grab some photos. The may also be some spare pumps, photos of those also if you like.

Cheers Kerrin
Get excited and make something!

Offline Brian Rupnow

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Re: Gear Pump
« Reply #32 on: January 11, 2015, 12:21:30 AM »
Thanks Steamer, but things are moving way too fast for me to wait. I have the bronze turned to size and I'm ready to cut gears tomorrow morning. If I really wanted to see what the inside of a gear pump looks like, I have one here that I could take apart.  I am limited as to what I can build in terms of gears. I have a complete set of 24DP cutters, so that is what my gears are going to be. I don't care enough about this project to even think of making some strange single point cutter to produce a new and wonderful gear tooth shape. ---Brian

Offline Brian Rupnow

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Re: Gear Pump
« Reply #33 on: January 11, 2015, 02:23:54 PM »
A good way to start the morning!! When I got finished with the rotary table, divider plates, and gear cutter I had an even number of teeth left. Now if I can just cut them to the right length---

Offline Brian Rupnow

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Re: Gear Pump
« Reply #34 on: January 11, 2015, 04:58:19 PM »
Everything fits and goes round and round when driven by electric drill. That's a good thing. There certainly isn't an overabundance of clearance anywhere. The shafts are temporarily Loctited to the shafts just for test run. I may build the cover side this afternoon. Depends on what my good wife has planned.

Offline Brian Rupnow

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Re: Gear Pump
« Reply #35 on: January 11, 2015, 05:14:49 PM »
This is where I'm going next. Again, I caution you--don't copy this drawing. It will be "proofed" as I make the part, and some dimensions may change.

Offline b.lindsey

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Re: Gear Pump
« Reply #36 on: January 11, 2015, 05:20:49 PM »
Looking good Brian and I am hoping it works as well as it looks also.

Bill

Offline Roger B

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Re: Gear Pump
« Reply #37 on: January 11, 2015, 07:16:23 PM »
Following along with interest  :popcorn:  :DrinkPint:  Tolerances are probably less critical with viscous fluids like lubricating oils.
Best regards

Roger

Offline Brian Rupnow

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Re: Gear Pump
« Reply #38 on: January 12, 2015, 02:17:17 PM »
Now, if you squint your eyes a little bit, and look really, really hard, you will be able to see where I have cross drilled the drive gear and shaft and Loctited a 1/16" diameter drive pin thru the hole. The other gear floats on the shaft, which floats in the bearings.  You can also see the recess in the cover for the o-ring which seals the shaft. Then a second cover bolts into the big recessed slot in the main cover to retain the o-ring.

Offline Brian Rupnow

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Re: Gear Pump
« Reply #39 on: January 12, 2015, 02:59:24 PM »
And here we are "running in" the gearpump. I intentionally left both gears about .005" too long, so when I tightened down the cover, I reached a point where the gears would no longer turn freely. Then I backed the screws off 1 turn and ran it on the mill for 2 minutes, with lots of WD40 on the gears. After it started to run freely, I tightened all 4 screws and repeated the run in. I did this in 1/4 turn increments until the screws were all completely tightened. so---there shouldn't be any end gap between the gears and the case now.

Offline cfellows

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Re: Gear Pump
« Reply #40 on: January 12, 2015, 03:47:14 PM »
Interesting project, Brian.  Wonder if something like this would work as a fuel pump...

Chuck
So many projects, so little time...

Offline Brian Rupnow

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Re: Gear Pump
« Reply #41 on: January 12, 2015, 05:24:01 PM »
In this picture you can see the inlet and outlet tubes finished to size and Loctited into place, the plugs Loctited into the back side of the main pump body to prevent any oil drip from potentially sneaking past the shafts on that side, and in the other picture you can see the scuff marks on the inside of the cover plate, from "running in" the gears on my mill.


Offline Brian Rupnow

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Re: Gear Pump
« Reply #42 on: January 12, 2015, 05:25:14 PM »
Chuck--I will be making a video of it {hopefully} pumping lubricating oil, and of it pumping water.---Brian

Offline Brian Rupnow

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Re: Gear Pump
« Reply #43 on: January 12, 2015, 08:02:33 PM »
Here's a quick picture of the rubber o-ring seated down in it's home.

Offline philjoe5

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Re: Gear Pump
« Reply #44 on: January 12, 2015, 08:14:47 PM »
Quick work on this project, as usual Brian.  :ThumbsUp: Good luck with the pump on its trail run.  If I make one of these I'll use module 1 gear cutters that translate to 25.4 dp.  A 12 tooth gear will be 0.551" OD, close to where you're at.

Cheers,
Phil
If you pick up a starving dog and make him prosperous, he will not bite you. This is the principal difference between a dog and a man.  - Mark Twain

 

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