OH Yeah! Gear Pump repair part 2
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- Опубликовано: 20 сен 2024
- Welcome to part two gear pump rebuild for the K&T mill. It didn't go the way I wanted but it did go the way I expected. Guess we may have a part 3 coming soon. If you would like to make a onetime shop donation or monthly follow the link below to my PayPal
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/ stevesummers
Put a check valve in that suction line. Simple fix.
Yes oil can't leak back to sump and I use it on dieselpumps witch are not self primed.
Yes a simple old brass flapper valve in the suction line. But it must be installed horizontally. So a 90 degree bend then the flapper valve then another 90 degree to the screen. This will give the easiest suction threw the valve. ( the flapper hanging vertically) This should keep coolant primed in the pump.
But be were if the pump can be run backwards you will have a hydraulic lock that can break things.
@@johnlemmey7698 A ball type can run vertically and just replace that suction tube. McMaster stock item.
Rambozo Clown that would be my suggestion too. The pump works fine,good flow and pressure, so any work on the gears would be a waste of effort. Even with new gears there is no guarantee oil would not still drain back when left unused. An in line valve or perhaps two, one before and one after the pump, would surely be the easist and most reliable fix.
Wasn't there a flapper in the delivery tube? If so you might just glue a peice of soft rubber to it and be done. Considering the slow rotation of the pump anything other than perfect gears and housing will probably have a hard time self-priming.
The edges of the gears should be a sharp edge or you increase slippage past the gears. I used to rebuild precision metering pumps. The gears are generally ground and lapped with the gear plate (middle plate) in a 3 plate setup. This is to ensure the gears seal against the top and bottom of the cavity. That is why you also need to keep the gear tooth edges sharp to prevent a leak path. You should not have broken the edge on the housing either. That also creates a leak path. Yours just does flow so some slippage might not matter, but will make it lose its prime easier.
As for the clearance between the gears and the walls, they should ideally be within a ten thousands of an inch or so.
Gear pumps do not self prime either fyi. If it is losing its prime, then it is probably the check valve. Wipers would probably mess with the meshing on the gears. You could make a spring loaded shoe to ride on the gear teeth at the outlet side. Think a v shape that is curved to match the OD of the gear. This is used as a wear compensator on commercial gear pumps already for transferring fluids without lubricating properties such as water. You only need to seal the last few teeth (maybe a quadrant or so), the rest are not important.
Agreed. Back in the 70's I worked with a millwright/mechanic who re-machined oil pumps for obsolete antique engines as a side line. Watching him sit and hand lap those parts always fascinated me with the precision that was required.
I agree with your comment except this is not a hydraulic pump this is a COOLANT pump that needs to handle particles of metal. It needs those 0.025" clearances to keep from jamming on the junk suspended in the oil it must pump. It all has to do with the time it takes for the particles to fall out of suspension. Junk under 0.02" may not drop before it is re-circulated. Steve's 0.005" clearance is too close, particles that small WILL NOT drop and WILL be circulated by the pump.
The edge beveling is a real problem. The edges should have been left sharp! The slope on the edges will funnel larger metal chips between the gears and face of the case. This could cause the gears to jam or bind.
Video part 3... regrind the gears to remove about 0.010" from each side of the gears to open the gap and get a sharp edge again.
@@chuckinwyoming8526 if you are getting particles large enough to need .025 wall clearance than they will bind the pump where the teeth mesh. Proper screening to filter them out will prevent this anyway. The clearance also makes it more likely to get junk in between the gears and the walls. No matter what, a gear pump is one of the worst types of pumps to use in this application. They are for precise metered flow or for high pressure applicarions. A flexible impellar pump is really what should be used.
@@anonymic79, I could pull the pump out of my machine and measure the clearances. As I recall they were very large. I suspect much of the 0.025" tooth clearance Steve measured was original to the pump. My 2HL is a direct predecessor to Steve's mill with many similar parts and design.
Unless you have run a K&T mill and had the wondrous fun cleaned all the crap out of the sump you don't have a feeling for just how much fine metal chips the coolant carries back into the sump. On my mill the drain tube from the table returns 8" from the pump sump (possibly baffled into a much longer path or diverted to the brass screens) .
I agree with you how a gear pump SHOULD be built and it's tight clearances. That doesn't apply here with very low pressure output of thick sulferized cutting oil full of metal particles.
NerdByDesign makes a great point that a gear pump is a poor choice for a dirty coolant pump.
Stainless steel sleeve to decrease gear side clearance
Put a non-return valve on the suction side of the pump, so it’s always primed
You got it, also known as a pump foot valve.
Just what I was going to suggest....
I'm thinking here that there are too many solids suspended in the oil to allow the seats to seal properly. Might work initially but will fail in time.
@@peterhaan9068 Should be OK with a soft seat and a weak preload spring
@@peterhaan9068 A finer screen should help with that, you just can't go too fine or it will clog too easily, though filtering the return oil could reduce any clogging but I don't know if that would be easy to do on this machine.
I would probably try nickle plating the gears to build up their clearance. I have no idea if it would work but maybe you could use it to build up the housing bore too? Worth a shot and I think the least cobbled solution to rehabbing what you have. :-)
I really enjoy your presentation of the subject at hand.
Keep on making more for sure.
I think it was a complete success, thats plenty of flow for milling operations. Well done
Steve “Fix absolutely everything“ Summers
Cheers from France 🇫🇷
Steve, that was an excellent job of describing the problem, explaining what you planned to do to try to make it better, and then clearly recording the work and testing of the fits and of how it pumps. Everything was clear to see, easy to understand your plan, and what results you might expect from the work you did. You have set a new higher standard with this video. Everything was done as close to your plan as might be expected, and without showing off, just getting it done while teaching your audience what exactly you were doing and why. I hope many other You Tubers out there will study this video and improve the execution of their own work, and the videos that explain it all to the watchers. Thank you!
When Steve pressed out that shaft and it went "BONG!" before sliding out, I was reminded of a Vintage Machinery.ORG video where Mr. Rucker had to push out a very stubborn shaft from an old pulley center and he had to do all sorts of things to finally get it out; it did more than just go "BONG!", though, it went "WHAM!" several times, in a way that was scary. It was somewhat amazing...
Steve...
Load up the inside side walls of that pump with solder...
Get it so the gears will drop back in then reassemble it and bench run it dry with a Leccy drill....
Them gears will profile & gap the walls perfect...
Strip...
Deep clean & inspect...
Reassemble...
Enjoy good flow rates...🇬🇧🙂
Man, that is radical!
Nice job Steve. Using a feeler to get close on your surface grinder is a fool proof method that works.....but try this. Put a white card on the left end of the table wall. Bend over and look at the white card from behind the wheel. Bring the wheel down until the white goes away. Been doing it that way since an old toolmaker showed me. When the white card become dirty just change it. Keep up the good work!
Gday Steve, I know this has been mentioned but put a check valve in line and I believe the issue will fixed, great video mate, ATB matty🇦🇺
As a FYI for your parts washer I have used Varsol with several gallons of water for years. The idea of adding water is to serve as a crud trap and it also save you on buying as much Varsol, just make sure your pickup is a couple inches above the water in the tank. A buddy of mine uses a #10 can as a sump for the pickup but while our machines both started off as the same brand machine years ago they both have been modified as well over the years. I also have a second smaller capacity parts washer that I use on parts after I finish scrubbing them clean in the “dirty” parts washer, that for a number of years has been an old kitchen sink I built a stand for that 5 gal can that served as a drain and a 5 gallon rigid aluminum fuel tank that I installed a couple of 3/8” fittings in one has a pressure regulator on it so I can pump a couple of pounds of shop air to it via a hose and a ball valve the second has a check valve in case something happens and more than 5 PSI is pumped into the tank and the third has a ball valve that hose and simple nozzle end on it to rinse the parts with the clean solvent. When the stuff in the dirty washer gets to trashed out to use it becomes starter fuel to burn brush etc, the slightly dirty stuff from the clean parts washer is used to fill the dirty parts washer after it gets a good cleaning and the cycle begins all over. I tried several water based parts washer fluids and even have a table top one with the stuff in it but regardless of what the manufacturers I have found flash rust to be a problem. I use the water based one to clean anodized, blued, coated, or non metallic parts in but keep raw metal parts of any sort generally away from them. Maybe there are better water based parts washer fluids than the ones I tried so far.
The best thing about a parts washer in the shop is how much less “Gum-Cutter” and Brake-Kleen that you use in the shop and besides being expensive most people don’t realize just how nasty both of those chemicals can be on your repository and circulatory systems.
Definitely my favorite engineering channel. You have the most agreeable manner. Thanks for sharing.
Think a minute about a well pump. They have to have a foot valve to maintain the prime. So, you are a machinist, make a foot valve using a ball bearing, a very light spring and a really great seat that all will fit in the pickup! Come on, you can do it! Greg
Excellent work dear friend
I agree with some of the previous comments on the check valve. Maybe you should work on the existing check valve and see what the problem is with it. They probably put it there for exactly that reason. If it seals than the pump wont loose its prime and your good to go.
Looking at Part 1, It appears the brass flapper would block any reverse flow that might prime the pump. A check valve on the input side and a drive shaft seal if necessary would allow removal of the brass flapper.
Hey Steve, just try putting a ball valve as low as possible in the system above the pump and use that for your cut-off when you shut down. Keep the valve at point of use for actively regulating flow. You'll trap probably several ounces of oil up top and that should be enough to prime the pump when you start up. Start her up and open both valves and I'll bet a dollar you'll get oil pumping. Worth a try, really cheap.
Handy tip for pressing pulleys or gears onto a shaft is to machine the shaft a few thousands ( the amount of the interference plus one ) smaller and about 0.020 wide so what you are pressing on shelf aligns. I learned that from a wise machinist who builds aircraft landing gear. He also taught me that taking off is optional but landing is not. 🤔
In the Navy we used oil paper gasket material for those pump flanges, but when we didn't have that we just used regular paper cut to shape.
Air in the pump body compresses and decompresses unlike the oil that it is meant to pump. Either increase the oil sump level to reduce the suction needed to prime and/or install an effective check valve just below the pump. The pump itself is working as designed, good job on the rebuild.
Slot the gears and add whatever material works the best. Enjoyed your work very much, you have talent indeed.
Steve, I absolutely love the detail and footage of this video series. Also, how cool is that of having a viewer send you that parts washer?! You have such a great viewership. Keep the videos coming. Take care.
You sure have a lot of experts giving you good suggestions. As a non-expert I vote for the check valve and/or resleeve the pump housing. Great job so far
Something I noticed while you were putting the pressure pipe back on, (where the check valve goes), is a recess or an O-ring groove for the check valve to seat? Is there any way you can check to see if the check valve is even seating properly? My guess is that all you need to do to get the pump from loosing its prime is to just fix the check valve that is already there.
Great work Steve. Keep the videos coming.
Is that check valve on the proper port of the pump? Steve is *removing* the valve to manually prime the pump (Part1 ruclips.net/video/TDxYFJvN3Ow/видео.html )
I also noticed that air seems to be getting into the oil when running it after priming the pump and taking the nozzle off. (31:38). See how milky it looks? Hear the popping sounds?
On the drive side of the pump, where the shaft goes threw the top plate, is there any kind of a seal on the shaft? If not, this may be where it is pulling air in when running and allowing air in when not running and allowing the oil to leak back into the sump.
I also think Dennis Williams has a great idea, raise the oil level in the sump may help.
I think you are all onto the problem with this pump. The check valve above the pump keeps or slows the drain-back above the pump. Ideally, there should be a (light)spring loaded check between the pickup foot and the pump body. That would keep fluid in the pump body above the sump level. Maybe there was one there at one time and it just got replaced by the pipe nipple.
@@ramosel The "spring" that forces the check valve to close is the 30 inch column of oil in the riser pipe above the check valve (and the weight of the heavy brass flapper itself). That should be more than enough to force the flapper in the valve closed when the pump stops. It works the same as the flapper in a toilet tank (which has less than 8 inches of water closing its flapper).
All the discussion about pump clearances is irrelevant. He only needs to make certain the flapper can form a good seal, AND he needs to ensure there aren't any leaks (in the pump case or the pickup tube) which would break the suction when the pump stops.
That sound right to me. Also I am thinking that "This Young Steve" is on to it too because he was rather insistent that we watch Part 1. That's fair, if he has some fun at our expense. We get plenty of enjoyment from his tireless endeavors.
Maybe try re-sleve the pump housing... seems like the less tedious way to reduce the wear
That's what I was thinking.
Yes, make a sleeve to take up the excessive clearance.
Re-sleeving twin overlapping cylindrical cavities would be a complete bitch! How would you even go about creating such a part, assuming you knew in advance the correct dimensions and required tolerances (which we don't)?
@@afriedli a strip of shim stock, curved into the outline of the 8 shape. Wouldn't even need to close both middles. Could probably even adhere it to the walls with loctite
I think that putting in bronze sleeves would be the best. Way easier than focusing on the teeth. Yes a lot of indexing but basically boring bar work.
Steve somehow put in a check valve in the pickup to keep the coolant from draining back into the sump. (simple one would be a ballbearing and spring) Or a flapper valve from a plumbing supply
very good with simple equipments !
I would blueprint the existing housing, and then fabricate an entirely new housing from a block of material.
But then I'm the type of person who enjoys such a lengthy process, as well as the satisfaction it brings. 👍🏼
Hello Steve, As a Pro machinist in a Hydraulic design and repair shop for 30 years I've a little advice, No1, check valve after the pump and before the pump will keep it wet, simple Gravity biased Marble design will work. No2 if you want to fix the tooth clearance issue simply machine off the housing altogether so you end up with a bearing plate and the use a block of Ally, and bore two holes of the correct diameter to match the gears you have, you then make alignment plugs to align the bearings to the new housing and fit dowel pins it's 6-8hours work and will be as good as new, done hundreds of these.
All the best
Rick
Perfect job for your shaper Steve, slotting the ends of the gear teeth using an indexer, for an interference fit of soft metal as a wiper. Copper? Brass? Bronze? Or some kind of poly type material. Enjoying this project. If nothing comes, then its a great learning experience. Thank you.
A new housing... from scratch! Now there's a project. 😆
This is a very good episode in the continued saga of Revival of Old Betsy.
I think a synthetic/polymer vanes are a good idea. A complex machining effort perhaps. A better idea would be a pair of sleeves in the bore.
Just remember, the gears may not touch the cavity walls but something wore out the cavity.
Steve, I had lots of fun working on my 1942 K&T 2HL and getting it running again. I suppose that is why I enjoy watching these videos. Mine was in much worse condition than yours when I re-built it.
I installed a T in the coolant outlet pipe at the top of the casting with a second valve, an elbow and short section of vertical pipe, open at the top that I can fill with coolant to prime the pump. You may want an easily removable dust cap on the pipe.
As you commented on in the video the coolant pump must be able to handle some trash. This is NOT a clean hydraulic system and you don't have any filter to remove small particles. I questioned if your 0.005" clearances on the gear face is too close. Particles that small will stay in suspension in the coolant for a long time. How viscus is the coolant you are using and was this pump designed for really thick sulferised oil?
Today we want to push a button and have everything running. That is not how these machines were designed. They require an operator to setup, startup and keep them running.
Nice job on the pump. Is there a check valve between the pick up and the pump? If not, that might help maintain the prime.
As for the solvent tank, used that same model for over 30 years. Still on the original pump and it's used daily. As for solvent, low odor mineral spirits works pretty well.. Expensive through Home Depot or Lowes. Might be cheaper through a Petroleum Wholesaler in bulk. It doesn't turn stinky here in the southwest heat which is a big plus. In addition, adding a screw-on diesel fuel filter between the pump and the brush hose extends both the life and quality of the solvent.
Steve Summers, really enjoying the channel, love how you represent fellow RUclipsrs by wearing their shirts, so where’s the Steven summers shirt? Maybe one with a Avatar of you and your wife, huh maybe. Keep up the Quality content!!!
Order yourself the Dremel EZ Lock cut off wheel kit. It's expensive but you will never go back. The wheels last surprisingly long. The cutter is driven but floats on the end of the mandrel so if you bind it in a kerf, there is no blow up. It will just run off axis and keep cutting.
Hi Steve you could slot the ends of the gear teeth and insert a floating graphite piece that would push out with the centrifugal force and press up against the sides of the body. this will ensure virtually zero gap between the teeth and the housing. this is how the scavenge fuel pump on aircraft work. just a thought. Thanks for the great videos and interesting content.
Really enjoiying the repair. I'd like to see the housing to gear clearance tightened up but I agree with most about putting in a check valve. Keep the repair content coming!
Grind that pump case down to reduce that .0055 down to about .0015. Touch the gears back and leave the edges sharp, same with the case. Get rid of the screened pickup and put a ball check on the end of the suction tube. That is what I would do next.
I ran a PSI screw supercharger on my alcohol dragster. I sent a BRAND NEW PSI & had it epoxy coated in the hsg. & the screws; they then "run it in" with lubrication, (just like lapping) & it improves the screw's performance about 10%. Epoxy spray your housing & gears, then run in the pump with some lube. You'll be amazed.
I like the idea of slotting the teeth (like an eccentric vane air horn pump). Guaranteeing that one won't go squiffy at some point and jam up the works will be a challenge. Jet engine vanes have a complicated "slot" in the hub, but obviously turn at slightly higher rpm than your oil pump. Good Luck 😃, love your videos.
I agree with Dennis Williams. If you can, raise the oil level in the sump. This will create net positive suction head. The pump will then self prime.
Use a sleeve.
Bore out some of the cast iron material from the pump housing and then insert a sleeve ( of course you have to cut some of the sleeve material a way for the inlet and outlet area ), but this would tighten the area around the sides of the teeth allowing your pump to build more vacuum.
Nickle plate the housing and gears then machine for clearance (make sure gear teeth and chamber walls have uniform wear or re-machine before plating).
Would plating be thick enough?
@@googleuser859 Nickel & nickel chromium is applied in "d" layers of about 0.0005".
I would make sure the check valve is sealing first before I did anything else. Like your channel keep it up.
Your usual top $ job keep the vids coming to the cold wet uk. Thanks
That initial POP is always a shock. SQUIRREL! That is my favorite Dremel cut-off wheel, too. I hate the new ones with the twist lock arbor. That was some great work to rebuild the pump, too bad it didn't work better. I have no experience rebuilding pumps, so my first thought was a good check valve in the suction foot. Good luck, and looking forward to seeing what ever you do.
enjoyed as always
Silver solder to build up the gear teeth. It is reasonably hard and low temp and easy to do. Won't affect the temper. You could also use it to fill the ruts in the housing but it would be trick to bore it flush. Minimum investment in time/money. No guarantee, but I think you always start with the easiest method. Good luck whatever you do. Oil pumps in aircraft engines are exactly the same so I am watching this with interest.
If you can spray weld, I think you could can mask, weld, and then turn the gears. Here's something interesting. Vintage Norton and BSA motorcycles use an oil pump like that just much smaller. They have the opposite problem. The oil tank is above the pump so the pump is never dry, but oil leaks past the gears when the engine is not running, filling the crankcases over time. When that gets bad, we lap the covers to remove any wear and the body to reduce the clearance to nearly zero - want as little clearance there are possible without binding.
WOOHOO, , , Saturday with Steve. Looking great bud. I did a bush fix on one of these pumps once with various sand papers and an old mirror. It took me almost 2 weeks to do but as far as I know it is still in service 6 years later. Great refit my friend and what a great gift in that washer. You have some fine friends bud. 900 likes is really impressive Steve. Well done fella. I am on your side with doing the inserts. Poss some hard brass liners as well. OR you can just make a primer reservoir for the pump to give it a shot to get it going. Seems it will hold a prime for a bit eh.
Great video and thank for the guy who send you the part cleaner, the next thing to make live easy is a sandblaster so you can clean part from paint, as always thump upp :-)
Learned a lot from this video and the excellent comments below. Thanks Steve and all commenters.
Tell that guy on your shirt to get back into the swing of things!!
Thanks for the upload Mr. Summers
As someone else mentioned, use JB-WELD to build thickness on the side wall of the pump body. Set it up and resurface the bores with a few tenths clearance. I did a spool from a 16 head filling machine to better fit the valve body, worked great. I used the one with metal in it. It cures hard and is good to machine. Also mentioned is a check valve. Good luck. George
Put multiple layers of polyurethane paint or varnish on the pump chamber walls to fill in the wear grooves and build up the walls. This will be a multiple stage process with some sanding in between. Any high spots will be self corrected by the gears and won't cause any wear on the teeth. Then put a better pre-filter on the pump to help reduce the particle size going into the pump. Lastly, put a cheap centrifugal pump (like a marine bilge pump) in the coolant tank to feed the main pump to help it prime.
great vid, my vote is for the NRV also. At a pinch you could bond PTFE liners into the bores and rebore, but that sounds like a pain and you will probably end up with something that will still not self prime.
My suggestion is to try the easiest and least destructive fix first. Then proceed in that order. From what I see in the video, the pump is working.
Great video as always. Good to see that you keep it real with the outcomes as they happen. Keep the video's coming!!!
Probably the best fix will be to make a blanking plug for the idler gear, and get a rubber impellor to replace the drive gear. Looks about the right size for a common boat coolant pump gear, and as those do flex, it will both self prime and also handle solid bits fine, plus bore wear is not too much of a problem. You might have to change coolant to a different type, or get an oil resistant gear, but that will be both cheap, easy to do and reliable, just order impellors in batches of 5, as they do fail with little warning other than the rubber flake count rising rapidly. You could even buy genuine parts ( Evinrude, Yamaha, Mercury) or one of the multitude of aftermarket parts. You even get those pump impellors in dairy applications, where they need to handle fat without issue, so are made from a variety of synthetic rubbers as well.
How about drilling two holes in the tip of the gear and use two dowels (tapping those gears might be difficult) and pin a strip of brass to the outer edge? maybe do some kind of fancy reverse chamfer on the end of the dowels to help hold the brass, maybe just a touch of sealant between them just to take up the gap. No heating required, then turn them down to get them perfectly circular.
If you took out the check valve and put a longer “head” above the ball valve; as when it is running with fluid, you shut the ball valve off, the line will hold fluid so when you want to use it again, open the ball valve and the fluid left in the line above the pump will drain back, priming the pump. That would be an easy fix without fixing anything.
Thanks for sharing your progress. My thought is mill a narrow slot for a teflon blade in each tooth.
Can't wait to see your solution. Keep up the good work!
Well, you asked for our thoughts. The hydraulic pumps that I have worked on have much tighter end clearance. .005 seems like a lot. The pumps that I worked on were .001-.002. Also, the pressure will push the gears towards the inlet side of the pump housing. The gears will rub a little on the side of the pump housing. Think of the tips of the gears like a cast iron piston ring. The only other thing to seal the teeth to the pump is the molecular structure of the oil. If your bushings are too tight the teeth cant seal against the housing. Hope this helps. I'm sure that there is more to it.
I was gonna say sleeve the pump, but it’s been said - my add on idea, is make the sleeves out of brass. Also, probably a good idea to make that pickup screen a little finer, keep some garbage out :-)
Steve, I would begin by boring out the case as much as possible. I'd then bond in some Turcite (or similar material) and machine it to achieve the desired clearance with the gears.
Hey Steve, love the problem solving and solutions you come up with and enjoying this repair/restoration!! As a solution to closing the gap around the gears in the case, couldn't you open the bore of the case up on the lathe, cut a 45 degree bevel on the front for a weld bead, machine 2 cast iron sleves that pop in, weld/braize them in and turn them to the required bore? Just thinking adding anything to the teeth would cause them to foul each other where they mate unless you machine the teeth deeper? Just an idea 👍 keep up the great work and content 😎
This seems like a reasonable idea, what am I missing?
This might be a long shot but what if you put a sheet of copper or brass inside the housing to close up the gap, maybe glue it tight? Treating the teeth doesn´t sound that nice to me but maybe this is doable. No heat and the gap closed- What do You think?
Nice shop, by the way. And You´re such a humble fella- if we even were on the same continent I´d like to work for You, I´d have a blast just broom the floor :) There are alot of machine shop channels but Yours is kinda special. Good, good job with the old mill. Please don´t re paint it, i like when something looks a little worked but i belive the energy of the person who rebuilds something matters way more than paint to me, it gives them things some soul.
Steve: My rule has always been "don't scream til you get hit". You have taken a lot of the slop out of the pump and it basically worked before. Put it back together and see if the improvement is enough. If not, you might be able to get the gears hard chromed.
Good luck!
Hey Steve,
how about a non return valve to stop the oil draining from the pump. Sure a simple ball on seat or a disc valve would be effective and easy for you to fabricate in the pick up pipe. I’m from an automotive background and some of the pumps I’ve come across must be built with grease or they never prime. Obviously you can’t do that, but a valve would stop drain back from the pump could be a simple option.
All the best, I enjoy your efforts,
David
Thank you for the excellent videos Steve, please keep them coming. Like suggested below, I would consider a liner of some sort in the pump housing around the gears, or if you're dead set on adapting the gears, build the tooth edge up with your tig welder. Perhaps less heat that brazing, but the tooth would probably harder than ever.
Your notion of slotting the teeth was my first thought. But I think the inserts will interfere where the gears mesh. You could use flat brass shim stock, bent around the gear bore. It could be made to stay in place by bending the ends and drilling corresponding holes/slots to retain the ends. Good luck Steve.
If you wanted to tighten up the radial clearance without making a giant project out of it, you could bore and install speedi-sleeves with some loctite, then cut out the center part where the gears meet. They have the sleeves in stainless, in stock. Might be easier to just press in som pcs of sch 80 pipe and rebore
That surfacing machine really grinds my gears... :)
Steve....I like your idea of slitting the ends of the gear teeth and inserting Teflon 'wipers' to increase the pressure. I say Teflon because it's flexible enough to be set to 'wipe' the inside of the pump housing without permanently deforming.....and increasing the likelihood of maximum pressure. Honing, or even re-boring, the interior surfaces would probably help, too, and the 'wiper' solution would adapt best to that, I think. Really enjoying your videos. Thanks! :-)
I like the idea of wipers on the tops of the gears just because it’d be cool 😎
As others have commented, I would go after the outlet check valve. If it is sealing correctly, the oil should not run back to the sump. Seemed to be an issue on the old Triumph 750 where the oil pump check valves would leak and cause issues. I've never had mine apart, but I believe there is a ball bearing, seating against a brass(?) seat. Punching the ball against the seat would restore the seal. You could always plug the end of your outlet hose, when you turn the pump off... come back after a while and see if the prime is still there.
Steve,
About 30 years ago there was a product called Belzona and they had what was called a liquid metal. It was a two part compound like epoxy but as strong as steel. Was used to paint the inside of pump walls then machine the walls back to proper dimensions. Wonder if there is a similar product you could use to paint the edges of the gears to build them up and then turn them in the lathe to tighten up the clearance.
JB Weld?
Excellent mini series Steve. I wonder if it's possible to bore it out and make 2 partial sleeves. It'd be an interesting job considering the figure eight shape.
IF you have access to a sheet roller, roll a strip of soft shim stock to cylinder ID dimensions, then permanently attach the two pieces to two cylinder walls with Permatex metal epoxy. A quick re-sleeve job
My K&T self primes no problem, I also worked with loads of gear pumps in the petroleum industry, try adding the check on the suction side and yes the rotor tip clearance is too big, add some tig bronze on the teeth and get the fit as tight as possible.
Another thought, right now the way it is the pump has to create enough pressure to force the air up opening the check valve with oil above pushing down, you might try first removing the check valve and letting all the oil drain back. The next time the pump is started it will not have to over come the oil pressure in the vertical pipe above the pump, it just might be as easy as that. So if the pump can create enough vacuum to raise the oil up to the pump it will be a bunch easier to do without the pressure on it's output side.
I watched part 1 This Old Steve!
Did you see a brass flapper valve in Part 1? What is that for?
Raise the oil level in the sump up to the gear pump. If the cutting oil is up on the pump it will self prime then
LOL
that is the ticket :) just keep the pump fully submerged.
Keeping a simple gear pump submerged in the oil has been done for ages, it's simple and it works. Really enjoy your channel, keep up the good work.
Steve, If you groove the gear teeth and put a wiper blade in them, me thinks you would have to silver solder them in to keep them from working loose and wearing excessively and possibly working out of the slot an jamming the pump. Just a thought from an old retired GI, non-machinist.
Make a non-return valve from a bit of plastic, ally or brass and a ball bearing. If that doesn't work then build up the teeth with braze and reprofile. Great videos. Thanks. Mike
try a nonreturn valve on the lift pipe to stop runback Steve.
Steve, sigh I had my fingers crossed. Epoxy coat the walls and then machine to size. There are epoxies formulated for fuel tanks,.etc. Less expensive than plating as someone else mentioned although I'm preferential to plating.
Great watching your videos Steve. To fix the pump you could decrease the diameter of the pump housing walls. I don't recall what your gap is but I would take some precision shim stock and trim it to fit then use some green loctite to stick it to the walls of the housing. Probably need to turn a couple of short bars to clamp it in place while the green loctite sets up. I have some xtra shim stock coming your way shortly.
A foot valve is what you need, as others have said. My waste oil furnace pickup line has one, and if it gets stuck open, it won,t pump.
I would sleeve the housing with bronze and glue the sleeves in with green loctite bearing retaining compound. Then bore to finished size (mill boring head or four jaw on the lathe).
Great content on machining and precision measuring. All I have for an easy suggestion has already been made, a check valve in the pick up tube if one will fit. Unless you can find original dimensions for the gears to see if they are the problem or if it is the case. Anyway, keep up the great videos.
I would think that opening up the chambers in the body to enable sleeving ,then final machining would be the most logical way Steve . .Have a look at the shop manual for a 60 year old Harley etc. and see what sort of clearance they aim at for tooth to chamber and end clearance for the two gears. I'm sure You are almost there other that the tooth clearances. Good luck.
Did you mention sleeving the bores for the gear teeth? (metal, plastic?) There is very little pressure developed by the pump so you could glue or screw the sleeves in place before boring them to fit the diameter of the gears. Having the sleeves come loose could be catastrophic.
Or you could replace the pump with an automotive one attached with rubber hoses. Try putting an easily retrievable magnet(s) in the sump to catch magnetic debris. You might be able to take up enough clearance in the pump for it to prime by inserting a small bar in the gear housing circumference to take up the clearance for one gear tooth on each gear as the tooth passes by. That way you could get momentary suction as each tooth passed the bar. You could play with the pump on the bench turning it with a drill motor. You could make a plexiglass cover for the pump to determine the proper clearance for it to prime.
A bronze pin made a standard sized welding rod or bar stock could be easily replaced in case of wear or damage.
Grind a slot on the end of the gear teeth and then insert rubber into the slots. Doesn't cost anything (assuming you have a thin cutoff wheel for one of your grinders) and the rubber is sacrificial and can be replaced when worn.
nice working
Hi Steve, clean the housing, grit blast the area where the gear OD's touch and apply ceramic repair epoxy paste. Let it cure thoroughly and rebore to the gear od size.
ATB, Robin
The case bores and gear teeth are worn fairly bad. I agree on building up the case. I'm going to try a check valve on the inlet 1st. I almost feel like a check is cheating 😁 even if it works.. if it fails I'll build the case up and re machine the case. Thanks for stopping by Robin👍. You should do a quick YT video on the boring bar you showed on IG. Its simple and a idea worth sharing I think.
a ceramic rod... I have never seen that before. Nice
always enjoy your vids... all the best from Ohio. My suggestion is to make two "bushings", press them into the pump (making new housing walls to mesh the gears).. just cut the extra radius off the gears, maybe attach them together somehow (low/no heat)... seems a better fix than to work on each gear tooth seperate