# Gear pump



## Brian Rupnow (Jan 8, 2015)

I may build a gear pump, just for interest sake. I finally bought the last cutter for my 24 DP gear set which will let me cut 12 and 13 tooth gears, and I have never built a gear pump before. The drawing isn't finished yet, so don't shoot me. I haven't put the shafts in, nor the near side cover, but I will get to it. If you are interested, then follow along.---Brian


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## Herbiev (Jan 8, 2015)

Looking forward to this project. I've been wanting to build one for some time now.


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## Brian Rupnow (Jan 8, 2015)

This may explain things a bit better.


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## Brian Rupnow (Jan 8, 2015)

The only difficulty I foresee is end clearance between the end of the gears and the inside of the housing. I have some "real work" thanks to my new Solidworks installation, but I still need a "play project". It may be quite a stunt. If the gears are too long, the cover won't bolt on tightly enough and fluid will leak out the joint between the main pump body and the cover. If I make the gears too short, then fluid will bypass around the ends of the gears, resulting in no pressure. I suppose that if a gear was made a bit short, a round piece of shimstock the outer diameter equal to the gear o.d. and the center hole equal to the gear shaft hole could always be used to remove any end gap. My initial thoughts were to make the gears of brass or bronze so they wouldn't rust if I used them to pump water, (and because brass or bronze is MUCH easier to cut than steel). I was going to make everything else except the steel shaft from aluminum. I believe that brass or bronze is more wear resistant than aluminum, so the gears could actually be made .001" to .002" too long and then have them "wear in" to the cover and main pump body to give an almost "0" gap condition. (If I can actually work to that close a tolerance.)


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## velocette (Jan 8, 2015)

Hi Brian
A clearance of 2 to 4 thous will not go amiss on the gears to housing 
The velocette manual for 1930's motor cycle oil pump advised that if the pump fitted with steel gears and housing that if the pump did not turn smoothly by hand.
You could bed it in with a mixture of fine brick dust  and oil and run it in turned with a drill or lathe until it turned freely.
Dismantle and clean thoroughly before refitting.
Oil gallerys from the outlet side to the body to the bearings will help with lubrication.
Nice drawings do not be suprised if it is not widely copied in lot's of home workshops.

Eric


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## Rustkolector (Jan 9, 2015)

Brian,
If you want to make a gear pump you might want to look at Jerry Howell's design for ideas. He had a cleaver way of supporting the drive shaft in belt drive side loaded applications. He used them for oil and coolant. I use his design for coolant pumps and they have been very reliable at 160-180F. For all my coolant pumps I use .500" OD brass gear stock. I vary the gear width to get the flow I need. Using a nominal OD gear stock ie, .500" allows me to use a .500" end mill to plunge cut the gear pockets after pre-drilling. After cutting the pockets, I move the cutter horizontally from one pocket to the other to get a nice flat gear face on the inside of the housing. I use brass for the gears and housings. I aim for zero+ gear to sidewall machining clearance. A few minutes of pumping WD-40 establishes a nice smooth running clearance. Tight gear side clearance isn't at all critical for pumping coolant. Not sure about oil. O-rings don't do well in higher speed rotary motion. I keep mine below 1000 RPM and they have done well. If the red ball in your drawing is a check valve, I believe you can do without it for either oil or coolant. My pumps will normally lift coolant 12" at very low RPM after run in. 

Jeff


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## Swifty (Jan 9, 2015)

After looking at the first drawing, I did wonder how you were going to seal the shafts. If O rings don't work, although I think they will on your application, you could always try to get some small oil seals and possibly use hardened dowels for the shafts.

Paul.


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## honghaiqu (Jan 9, 2015)

Hello Brian, i am just in the areas of pumps, not only gear pumps, but also centrifugal pump, rotary pump and screw pump.

Your project looks great. 
Can i know what area will your gear pump used for?

You may check my website www.chinaoilpumps.com and find the pumps. Would you like to share more knowledge in CAD work, i am looking forward to hearing from you.

Happy new year!


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## Charles Lamont (Jan 9, 2015)

Brian Rupnow said:


> My initial thoughts were to make the gears of brass or bronze so they wouldn't rust if I used them to pump water, (and because brass or bronze is MUCH easier to cut than steel). I was going to make everything else except the steel shaft from aluminum.



Using copper and aluminium based alloys together in contact with water would be asking for corrosion trouble because of the large difference in the electrochemical potential of the two metals.


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## Mechanicboy (Jan 9, 2015)

Gear pump house and gear is often made of bronce if water/saltwater is used. Oil as fluid no problem in other material than bronce such as aluminium or cast iron house with steel gear, plastic gear or bronce /brass gear. Some time we can find the house in plastic material with brass or plastic gear. The drivingshaft can be made of steel, stainless steel or bronce depending on which fluid is pumped into the gear pump. The antireturn ball is not neccesary if the pump is soaked in fluid or under level of fluid if mounted outside the tank.


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## gus (Jan 9, 2015)

Hi Brian.
I'll be on making a gear pump pumping the lube oil for the Howell V-2 Gas Engine. Will be 6 months away. Will read up and give you some second hand tech advice.
Looking forward to follow your thread.
You may have to lap both gears in a separate set up to get a good sealing finish. Know nuts on gear pumps but been using same bought for Hydraulic Power Packs for my hydraulic projects 20 years ago.

Good Luck.


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## Brian Rupnow (Jan 10, 2015)

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.


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## Brian Rupnow (Jan 10, 2015)

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?


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## Charles Lamont (Jan 10, 2015)

Well you could just make intersecting round holes - the flat sides to the cavity serve no purpose, and it is often better to avoid dead space in pumps.


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## mu38&Bg# (Jan 10, 2015)

Remember that endmills are not flat bottom. Though, I don't think it's enough to matter here. It's not necessary to clear the web between the bores for the gears. If you do, it doesn't have to be full width or depth. The initial 1/2" cut would be plenty. Would this be easier to do in a lathe? I'd be cheating with a CNC mill, but if I was going manual it would be in the lathe.

How much will this pump flow? Last time I calculated a gear pump for single cylinder oiling, the volume was tremendous, even driven off the cam with tiny 0.5M gears.

Greg


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## Brian Rupnow (Jan 10, 2015)

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. The test shaft fits in there, snug as a mouse's ear!!


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## Brian Rupnow (Jan 10, 2015)

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".


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## Herbiev (Jan 10, 2015)

Wow. By the time I read this article and get my head around it you're already half way there. Great post Brian.


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## Brian Rupnow (Jan 10, 2015)

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.


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## gbritnell (Jan 10, 2015)

Brian, 
You can make gears from almost any material the only caveat is that both gears not be made from the same material. When made from the same material they wear a lot faster than mixed metals. How much faster I can't say but I'm sure you found the frictional properties of metal if you've ever tried to slide a close fitting aluminum rod into an aluminum bore. Now take the same aluminum bore and slide a rod of any other material into it. Voila!
gbritnell


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## Brian Rupnow (Jan 10, 2015)

gbritnell said:


> Brian,
> You can make gears from almost any material the only caveat is that both gears not be made from the same material. When made from the same material they wear a lot faster than mixed metals. How much faster I can't say but I'm sure you found the frictional properties of metal if you've ever tried to slide a close fitting aluminum rod into an aluminum bore. Now take the same aluminum bore and slide a rod of any other material into it. Voila!
> gbritnell



George--I can't say I have knowledge about the wear properties of dis-similar metal gears, but I do know that they seem to run quieter when made from two different metals. This little pump won't see long hours of service. It's more of a "Gee, I never made one of those before!" project. I'm sure it will pump. I just don't know what pressure it will achieve (if any) nor what volume it will pump, nor what rpm it will run at. It is intended more as a little "fun research project" than anything.---Brian


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## Brian Rupnow (Jan 11, 2015)

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---


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## Brian Rupnow (Jan 11, 2015)

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.


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## Brian Rupnow (Jan 11, 2015)

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.


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## Brian Rupnow (Jan 12, 2015)

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.


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## Brian Rupnow (Jan 12, 2015)

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.


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## Brian Rupnow (Jan 12, 2015)

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.


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## Brian Rupnow (Jan 12, 2015)

Here's a quick picture of the rubber o-ring seated down in it's home.


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## Brian Rupnow (Jan 12, 2015)

Everything is done and all buttoned up. I have to make up a gasket yet, and I want to make it from the thinnest possible material. I searched all over town today and nobody carries the really thin Teflon gasket material that Gail in New Mexico always recommends. My business card stock is .010" thick. Ordinary printer paper is .003" to .004" thick, but it is too fragile. I will root around a bit and find something for a gasket, then make up a pulley, and we'll try this thing out!!


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## Mechanicboy (Jan 12, 2015)

Use RTV silicone instead gasket. Apply thin layer and away from gear.


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## Brian Rupnow (Jan 12, 2015)

I ended up using a .007" piece of oil treated light cardboard as a gasket. I have tried the pump out using the mill to power it, but the test was inconclusive. I will make a proper set-up tomorrow and run it off my side valve engine. I didn't have a 3/16" steel ball for the check valve---the balls I had that I thought were 3/16 turned out to be 7/32" diameter, so I ordered some 3/16" balls and they will be here tomorrow. Preliminary indications are that the pump will not lift oil up from a lower elevation, but I will know better tomorrow. EDIT--I just realized as I posted this that my test today was probably inconclusive because the 1/16" diameter hole thru the pump body for the ball retainer rod was open--the rod hasn't been installed yet!!!


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## Mechanicboy (Jan 12, 2015)

_Preliminary indications are that the pump will not lift oil up from a lower elevation,_

The pump will not lift fluid in a height due clearance between gear and pumphouse make airleakage, better to have pump soaked in the fluid or under level of fluid if the pump is mounted outside the container for fluid. Gearpump work very well with fluid inside.


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## Brian Rupnow (Jan 12, 2015)

Things are looking up!!! I plugged the 1/16" hole and retried the pump. The vessel full of oil was 4" below the pump, and I started the pump dry, with no prime. It sucked the oil up from the vessel, and then was able to pump it 24" vertically (that's all the tubing I had). It is sucking air somewhere, because I am using clear tubing and I can see a lot of air bubbles entrained in the oil coming out of the discharge side of the pump. However, the pump does work. I don't know yet how good or how consistently, but it does indeed work.---More tomorrow.


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## Brian Rupnow (Jan 13, 2015)

This is what I hope to put together today for a test rig driven by my side valve engine.


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## Herbiev (Jan 13, 2015)

Next project. Hydraulic ram for small log splitter ??


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## Brian Rupnow (Jan 14, 2015)

We are ready to Rock and Roll!!! By the time you see this, the first test will be underway. I dismantled the pump and put in a 3/16" diameter ball for the check valve, and it works great according to the "Suck and Blow" test. The 1/16" ball retainer pin has been Loctited into position, and a dab of Loctite put on the #6-32 o-ring retainer plate bolt threads to seal any air leaks. I salvaged a 1 7/8" diameter pulley off some old project (it was a 5/16" bore but I sleeved it down to 1/4".) I used a piece of 1" o.d. steel tubing for my oil reservoir, and that funky looking curved part is just a solid 3/16" rod to support the upper brass spigot that my clear flex line attaches to. From the centerline of the pump gears up to the top of the loop in the clear flex line is a total of 9". The first test will be conducted using some cutting oil, because that's what I have handy. It is very cold out in my main garage where I test run all of my engines, so I will probably conduct this test in my warm little machine shop, using my mill for power. If it works as good as I am hoping for, then I will move the operation out to the main garage, turn on the furnace out there, and make a video of the pump being driven by my side valve engine.


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## gbritnell (Jan 14, 2015)

Brian,
The picture in post #23 which shows the gears in place looks to me like it will cause a problem. The reason being is that the gear teeth seem to be too thin and won't seal when rotating. The mechanics behind this type of pump is when the gears are rotating they carry the oil around the inside of the housing. Once the oil gets to the opposite side of the pump the close meshing of the gears seals the exit route for the oil and pushes it through the outlet. 
To have any kind of pressure efficiency all of the dimensions need to be as close as possible, O.D. of gears to housing, width of gears to cavity, and mesh of the gears. 
gbritnell


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## Brian Rupnow (Jan 14, 2015)

Yowzahhhhhh!!!!
[ame]https://www.youtube.com/watch?v=zUoXAUPtAhY&feature=youtu.be[/ame]


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## Brian Rupnow (Jan 14, 2015)

One message to all those who have pointed out that this gear pump will not create much pressure because of the gear tooth shape. I didn't set out to make a high pressure pump. I set out to make a pump.  I have a set of 24 DP gearcutters, and that is what I used. I know that there are specially designed gears to work with fluid pumps to create high efficiency and high pressures. When I began this project, my intent was to make a pump that would lift a fluid from a low elevation to a higher elevation, using what I had. If it had much pressure, well, sure, that would have been a bonus.---But--I never intended nor expected it to be a high pressure pump.


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## canadianhorsepower (Jan 14, 2015)

Brian Rupnow said:


> One message to all those who have pointed out that this gear pump will not create much pressure because of the gear tooth shape. I didn't set out to make a high pressure pump. I set out to make a pump. Period!!! I have a set of 24 DP gearcutters, and that is what I used. I KNOW that there are specially designed gears to work with fluid pumps to create high efficiency and high pressures. When I began this project, my intent was to make a pump that would lift a fluid from a low elevation to a higher elevation, using what I had. If it had much pressure, well, sure, that would have been a bonus.---But--I never intended nor expected it to be a high pressure pump. If I had wanted a high pressure pump, I would have marched my fat old butt down to the hydraulics store and bought one. This pump is an absolute success in my opinion. It fulfills the function I had intended it to.----Brian


 
I&#8217;ve seen better reply to group members opinion then this one 
Specially after asking group member's opinion in post #4 and #13:hDe:


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## Brian Rupnow (Jan 14, 2015)

Here we are as promised, driven by my side valve engine. Chuck fellows had asked in an earlier post if this pump would be suitable to pump fuel. I told him that I didn't know, but I would try it with water instead of oil when it was finished. I substituted plain tap water for the oil, and it pumped plain tap water at the same rate it was pumping the oil. 
[ame]https://www.youtube.com/watch?v=VvsOyoBthuo&feature=youtu.be[/ame]


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## gbritnell (Jan 14, 2015)

Sorry Brian,
It will limit my responses!
gbritnell


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## Brian Rupnow (Jan 14, 2015)

gbritnell said:


> Sorry Brian,
> It will limit my responses!
> gbritnell



Nah George--I'm sorry. My bad. I post on 3 forums and somebody on all 3 has warned me about the fact that my tooth form is not right for a pump and I shouldn't expect any pressure. I must have taken my ugly pill this morning. When I grow up, I want to be as good a machinist as you are.---Brian


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## Brian Rupnow (Jan 14, 2015)

And should anyone want to build this pump for themselves, just keep your tolerances fairly tight, and don't expect it to be a high pressure pump.---Somebody let me know if the download link works, please.---Brian
http://www.mediafire.com/download/0pdg7jfpx3qnvd9/GEAR_PUMP.zip


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## Swifty (Jan 14, 2015)

Great job Brian, you certainly proved what you set out to do.

Paul.


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## Brian Rupnow (Jan 14, 2015)

I must have taken my grumpy pills this morning, because I gave a couple of grumpy a$$ed responses in this thread. I apologize. Generally, I'm a lot nicer.---Honest!!!


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## Lathejack (Jan 14, 2015)

Hello Brian.

A very interesting thread. I have long been fascinated with gear pumps, and it's been one of those projects I planned to have a go at one day.

So this may spur me on to finally have a go, just as your bicycle dynamo project did.

I wonder, can you feel even the slightest pressure if you put your finger over the oil pipe outlet while the pump is running?

I have hoped to make one that does produce some pressure, as I plan to use it in an I.C. engine. They do require close clearances all round and are certainly trickier to make successfully than a plunger pump is.

I remember I once bought a new oil pump for a 1975 Triumph Trident motorcycle I was rebuilding. This was a double gear pump with scavenge and feed pump gears. It was a new non genuine pump, so I bench tested it first. It was totally useless, being unable to develop any pressure at all, the internal clearances were just too big.

 I stripped, cleaned and carefully reassembled the old original genuine Triumph pump, and when bench tested this was light years better than the rubbish new one. When refitted to the engine it produced 92 PSI at idle.

I am actually working on the refurbishment of a full size gear pump at the moment for a friend. This is from a 1940's A.E.C. double decker bus he is restoring. It is powered by a straight six diesel engine. I have noticed that the edges of the teeth on one side of one of the gears have a slight bevel. The edges     should be sharp, so that's one area where pressure will be lost.

Anyway, I am off to find suitable materials for my own gear pump.


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## Brian Rupnow (Jan 14, 2015)

Lathejack--Yes, when I block off the flow with my finger there is "some" pressure, but not a lot.  I am going to investigate a "lip seal" as a replacement for the o-ring. It sticks in my mind that some lip type seals are sized to be almost an exact interchange for o-ring seals.---Brian


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## bmac2 (Jan 14, 2015)

Cool pump. Looks like it would defiantly keep a water cooled engine happy. Um . . . One little thing . . . Please tell me thats not what your tap water looks like.


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## gus (Jan 14, 2015)

gbritnell said:


> Brian,
> The picture in post #23 which shows the gears in place looks to me like it will cause a problem. The reason being is that the gear teeth seem to be too thin and won't seal when rotating. The mechanics behind this type of pump is when the gears are rotating they carry the oil around the inside of the housing. Once the oil gets to the opposite side of the pump the close meshing of the gears seals the exit route for the oil and pushes it through the outlet.
> To have any kind of pressure efficiency all of the dimensions need to be as close as possible, O.D. of gears to housing, width of gears to cavity, and mesh of the gears.
> gbritnell



Hi Gbritnell.
You are right.
Been putting together Hydraulic Power Packs for the 200 ton Deep Draw Presses.It is true that gear profile is thicker,higher and mesh very close to give very good sealing with the hydraulic fluid to prevent leak back.For high pressure you sure need this precision. For liquid transfer,Brian's gear pump worked well with positive head. The test comes with negative head.
Will have to DIY a gear type lube pump for the Howell V-2. Will be fun.
for hydraulic pumps. Brian has demonstrated his gear pump moved oil.


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## ShopShoe (Jan 15, 2015)

Brian,

Thanks for another interesting project with well-documented post. You seem to be on a roll with several things right now. I like all of 'em.

--ShopShoe


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## vederstein (Jan 15, 2015)

Brian,

Congrats on your success.

Twelve years ago I was tasked at work to design a low cost hydraulic pump to develop approximately 1000 psi.  I initially started with a gear pump design with limited success.

Eventually I went to a geroter (look it up) and stuck to the design guide's recommendation.   Again limited success.  It was only after further R&D adjusting rotor clearances did I meet then exceed my goal.

So I can appreciate your accomplishments with what you've done.

Again, congrats.

...Ved.


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