JV Puleo

My 1910 Mitchell "parts car" project

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Joe, for what  it's worth, here is my thoughts after studying your photos. The photos you posted on Thursday 1st January look as if the vane on the left hand side of the photo has distorted quite a bit. Or, is it the photo that makes it look as if it has distorted? I agree that the vanes should be thinner as mentioned before. I also think you maybe better off making the vanes in steel or cast iron as the phosphor bronze ones are rubbing against a similar material. Which, from memory, is not good practice? Mike

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Thanks, Mike... we are obviously on the same page because I'm making the new ones longer, thinner and out of steel so it looks as if we've both come to the identical conclusions. I would like to get as high a polish as possible on the mating parts. That will discourage wear as well.

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Hello Joe, Everyone has the "two cents" comments and I will share mine.  I came from a dairy farm background of which vacuum pumps were the big part of our livelihood.  Later I worked for years as a journey mechanic at a Power Generation Station.  Vane pumps were used there for many widely divers applications.  The vanes for our vac. pumps and also the rotary transfer pumps were always a dense fiber material, (varied per application of the pump).  Yes, these pumps were rebuildable and yes it is way more desirable to replace the vanes, considered consumable,  than to replace the pump barrel.  This type pump, that you are engineering, does have many applications and have been used across industry for many decades.  Respectfully, I disagree with Mike on the type of materials suggested for use as vane material.  Mike please pardon my differing opinion, (I do agree with your thoughts on similar materials and wear rates).

Al 

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Hi Al,

I do have phenolic resin sheets  - the dense red fiber material that is used for electrical insulation. I once made a distributor cap out of a big block of it.  If I can find some of the right thickness I'll make a set of vanes out of that for test purposes but it is tough to machine and probably impossible to surface grind. I do wonder about the weight. If the pump is to work on centrifugal force as I'd like, that will be a function of the speed of the pump and the weight of the vane and the fiber vanes will be lighter. I do think it is worth trying though. I confess I hadn't thought of that but until recently I'd never even heard of this type of pump so I'm certain your experience trumps mine by a great deal.

 

Another problem is that when it is in place the pump will be unreachable without pulling the flywheel so making it simple and durable is important... on the other hand if a set of fiber vanes lasted 10,000 miles that is probably more than I'll ever drive and the engine will not be difficult to take out or put back - maybe a lot easier than trying to rebuild it in the car.

 

And thanks for the ideas guys... I don't claim to be an engineer (or a machinist for that matter) so there is a lot of experimentation going on here.

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Joe, One follow up comment to your statement on weight of rotor vanes and centrifugal forces.  Most vac. pumps had lite compression springs located in the bottom of the vane grooves to keep light tension outward on the vane.  These were nothing scientific and were intended to keep a flexible tension on the vane to assure smooth but easy contact between the vane and the case.  Using the springs removed the need to rely wholly on centrifugal forces especially at lower RPM's of which you will be running.  Our dairy vac. pumps running wide open and for 6 to 8 hours a day, (and running good vac. oil) would last 5 years between rebuilds/vane replacements.

Al

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Hi Joe & Al, no problem regarding different thoughts. The idea of these posts is to pass on knowledge and tips to help others. I have come across fibre vanes before, used in compressed air motors for sanders, etc, I just thought fibre may not be suitable for using with oil, and may wear away too quickly. That is why I suggested steel or cast iron as Joe has phosphor bronze bore to the pump body. With phosphor bronze valve guides in a  BMW 4-cylinder race engine, is often the harder valve stem that wears, rather than the valve guides themselves - which I find strange.

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Posted (edited)

I have given thought to using flat springs. My concern is a spring breaking and the two pieces falling on top of each other. Unless there is enough clearance below the vane to accommodate double thickness of the spring the pump could jam. I may well be overthinking this because with the reduced size of the camshaft there might be room for this. I also have had a difficult time finding a short, flat spring that would work and be suitable for a very high number of cycles. I'm reluctant to make them myself, at least using one of the many do-it-yourself spring tempering techniques. If I have to use springs I will make them but I'll have a friend of mine, with a digitally controlled heat treating oven, do the hardening and tempering. There are a host of spring manufacturers that solicit special orders but no one is going to set up to make a dozen springs... I'd have to buy a few thousand. That's the reason I want to try centrifugal force first. The saving grace here is that we are not talking about high pressures and at the lowest RPMs a pressure of only two or three pounds may be fine. The early pressure lubricating systems relied far more on volume than pressure... my goal of 15 lbs may be too high as I may also have seal problems at the front and back of the engine. It could be that 4 or 5 pounds with sufficient volume are what I really need.

 

Al, since you've obviously seen the inside of far more of these than I have, what do the springs look like? If you know of a pump with a 1/4" wide vane perhaps I could buy some ready-made as replacement parts. I see lots of ads for those as well but they never include the dimensions.

 

In any case, I'm taking my time with this. It's important that I work the bugs out and realistically I'm still a year or two from starting the engine. Actually, I hadn't planned to attack the oil pump again until I got back from the UK in March so I'm already ahead of the game.

Edited by JV Puleo (see edit history)
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Since I posted the above last night I've done some more searching and found at least one ad for "vane springs" - which turn to be coil springs mounted in exactly the same manner as I used in my first rotor. The problem is putting two tiny holes, drilled to a precise depth, in the underside of the vane. The holes have to be no more than 1/8" in diameter. I'm not great at tiny parts. My machines are really not designed for that type of manufacture but I did have an idea for a fixture that would help me to do it. So, I'm going to test the centrifugal force pump but if I have to add springs I think that is now doable.

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Need the depth be precise? As it is a spring it should not matter about the precise depth. Think about adjustable spring platforms on suspension to get corner weights correct on race cars. Hole diameter for the spring also will not need to be precise as long as the spring can compress and decompress without fouling on the sides of the hole.

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Right on Mike!  It is not unusual to see 4 or 6 of these small ports drilled, into the rotor, to accept the small coil springs that are just strong enough to keep the vane in contact with the barrel  and no more.  It does not need to do any more work than that.  Joe, I think you are headed in a very good direction with this rotary vane pump you are engineering/building.  You will be taking centrifugal forces out of the equation which will result in a fully functioning vane pump at low RPM's.

Al

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The problem with the hole diameter is that if the vane is only 1/4" wide it has to be a very small hole and since there is so little room to work with it really has to be in the center of the vane. That's one of those "easier said than done" jobs. Besides, I'm a bit obsessive about precision - perhaps because it's such a challenge to me. If I had more experience I might be a bit more relaxed about it!

 

jp

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It is very easy to break a twist drill when drilling tiny holes. You might look for pivot drills for this job. They are a spade shaped bit. They are used by clockmakers to drill a hole in a clock arbor to repivot it. I learnt about them after breaking a 0.7 mm drill, nearly at full depth, while attempting my first repivoting job.

 

If you put two springs on a vane, I think you are right in needing the holes to be exactly the same depth. You also need the springs to be the same strength and length, thus high quality springs. I would expect that in the long term, any difference in applied force will result in differential wear so your vane will start to "tilt".

 

This seemingly simple piece of kit turns out to be more complicated than we think!

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Posted (edited)

Hello Joe,  Do you happen to have a long shank 1/4" four flute end mill?  If you do and can do your calculations which would involve the length of the compression spring, how deep you hole needs to be to seat the spring and be deep enough to allow for compression with out binding, I would not hesitate.  You certainly have the skill set and equipment.  You are also right about being a "machinist" we do tend to be a bit OCD about some things.  I find myself being a "machinist" even when I do carpentry work, (and not needed!).  A good friend of mine, that has helped tutor me as needed on some of my more detailed projects, keeps reminding me.....are you building a Swiss Watch here or just doing it right?   That question always helps me to really evaluate the over engineering that I tend to do also and make adjustments so I can get things done!  Spinneyhill, I don't see a serious problem with using only two springs and I do agree that you would want the spacing to be the same and also the hole depth and proper springs.  This type compression spring shouldn't exert too much pressure on the vane, as that is not needed, you would just want the vane to be held to the ID of the barrel.

Al

Edited by alsfarms
addition (see edit history)
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That's just about what I had in mind!

 

j

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Posted (edited)
2 hours ago, Spinneyhill said:

It is very easy to break a twist drill when drilling tiny holes. You might look for pivot drills for this job. They are a spade shaped bit. They are used by clockmakers to drill a hole in a clock arbor to repivot it. I learnt about them after breaking a 0.7 mm drill, nearly at full depth, while attempting my first repivoting job.

2

 

I think we call them "flat drills" of "spade drills". They are actually the type of drill that was used before twist drills were invented. I have a few big ones made by Brown & Sharpe. They drill straighter holes than twist drills do but they can't expel the chips so you have to keep withdrawing them to blow the chips out. I've drilled big holes with them as an experiment - they are excellent for cast iron. They were also easy to sharpen and to adjust the size.

 

I was actually thinking of using a 1/8 center cutting end mill as a drill. That would give a flat bottom hole.

Edited by JV Puleo (see edit history)
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Been following the posts and I would use a 1/8" end mill to make the holes for the springs too. On the vane material; I believe my 31' chevy's original vane oil pump had fiber vanes. I know the vane slots were not straight 90d from center out but angled from the rotor cross line. Not sure though and might try to find that pump and take some pictures. The vanes in that also have springs in them. I always enjoy every post of this thread! 

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I do like Al's comment " . . . . .are you building a Swiss Watch here or just doing it right?" I shall have to remember that. I think we all strive for perfection, even when a part is hidden from view. We all want parts to be 'the best we can make'. I wish we had had forums like this in my early days. They would have saved me lots of time and grief! Mistakes were, and still are, a very good way to learn. Keep up the good work Joe, I really enjoy all your posts and have learnt a lot, even at my old age.

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8 hours ago, Mike Macartney said:

I do like Al's comment " . . . . .are you building a Swiss Watch here or just doing it right?" I shall have to remember that. I think we all strive for perfection, even when a part is hidden from view. We all want parts to be 'the best we can make'. I wish we had had forums like this in my early days. They would have saved me lots of time and grief! Mistakes were, and still are, a very good way to learn. Keep up the good work Joe, I really enjoy all your posts and have learnt a lot, even at my old age.

While many of us here Mike do exactly as you say,  and won't settle for anything but our best work, there are many these days who are very satisfied with the "good enough" thought process. My dad always said to me it usually takes no more time to do something right than doing it fast with little thought as doing right means you will most likely only do it once. Doing it to just get it done and get it done fast often results in it having to be done again, taking more time than doing it right in the first place. My son is 28, an electrical foreman in a large company, doing HD industrial work in big mills and power plants. I told him exactly what my dad told me and it is how he does his work. This simple work ethic has quickly propelled him within his company to his current position. He tells me how frustrated he is with many who work under him  and are in the trade who have the "good enough" attitude as that sort of attitude doesn't cut it when dealing with thousands of volts in an industrial setting. He tells me this is not just with the younger workers but the older guys (my age, my son reminds me of! LOL) that just seem to care less about having pride in their work. I understand the younger workers being that way as many have been raised in the time of everyone gets a trophy and no one stays back in a grade but the older guys shouldn't be that way but they are. Many wonder why other countries manufacturing goods are making better products than those made in the US and simple worker self pride in workmanship is one reason. Not sure how things look over your way but we've been seeing it for years. 

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Of the dozen or more antique machine tools I've owned ALL  of them have been abused at some time. The trick is to find one that wasn't too badly abused. I suspect the "good enough" attitude has always been with us - it's just recently that it's been given credence. That said, in my working life I always strove to be able to do any job in the shop as well or better than my employees... surprisingly, that wasn't too hard.

 

I've been working on the radius turning tool "2nd Edition" This one is a lot simpler and I suspect I should have done it this way to begin with. The first step was the base,  made from a square of aluminum 4" x 3-1/2" x 1"

 

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Here it is the base fitted with the plate that will secure it to the lathe compound.

 

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The rest of it is much the same as the holding fixtures I've made... here I'm putting in center holes for the clamping bolts.

 

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And center holes for the cap screws that will hold the vertical part to the base. That extra hole you see is a mistake on my part.

 

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Assembled to make sure everything lines up. Tomorrow I'll bore a 1-1/2" hole in the center and put in an oil hole - then it's time to test again.

 

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I started this morning by setting the radius turning tool up in the lathe and drilling a hole to start the boring bar.

 

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I took it out to about 7/8" then set up the boring head.

 

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This part went smoothly. Here's the finished product. I hit the size dead on.

 

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I never milled one end of the 1-1/2 square pieces because getting them perfectly to length is a PIA. Instead, with the tool assembled I fly cut the side where they were unever. This won't make the tool work any better but it does look better.

 

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So, here it is. I had intended to make a split bushing so I could adjust tension on it but when I assembled everything the tension was just about perfect as is. I can always do that later if it needs it but for now, this is fine.

 

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I also discovered that I have to take the tool apart in order to mount it - something I hadn't anticipated but not a major problem.

 

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I tried it out with a boring tool and then with a 1/2: end mill as a cutter. Neither worked although the tool itself functioned exactly as it should. The problem is cutter shape... and grinding cutting tools has never been one of my strong points. Despite the fact that it didn't cut well there was no vibration in the tool itself so I'm convinced that when I find a cutter that works the entire thing should be fine. I did see something on youtube - I hate watching youtube videos but I do have to admit that occasionally I find a good idea there. In any case, tomorrow I'll try it. If it doesn't work, I have to go on to another job I promised a friend for another brass car so I will probably post some photos of that project as well.

 

I did have a couple of near misses though - I forgot to measure the radius of the boring head itself. Fortunately, it fit albeit with a very small clearance. I did have to reduce both the width and the diameter of the set screw collar to get it on but overall, I'm satisfied.

 

Edited by JV Puleo (see edit history)
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The cutting tool I saw on youtube was made from a piece of 1/4" round tool steel. The only things I had at hand was this box of single flute cutters probably made for a Gorton pantograph mill. They don't have the right shape tough so I needed a way to grind them accurately.

 

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Then this morning, on the way to work it occurred to me to try using my valve grinder.d That worked a charm. I put the cutting bit in the tool I made to hold the diamond point that is used to true up the wheel. I also discovered that the oil pump on the machine has died but decided to use it in any case... the cuts were very light.

 

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I had to make a small tool holder to hold the tool since the hole in the boring head is 1/2". From the start, it was making smooth cuts although it's tedious to use because the adjustment is on the bottom where you can't see it. Nevertheless, I was pretty pleased with the result.

 

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I had thought this piece was ruined but kept at it for practice. Oddly enough, I made a miscalculation in the size of the big end that gets turned into a ball so, in the end, I was actually able to save the piece. It's about .015 undersize... not bad considering how many times it's been in and out of the machine.

 

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It certainly did. What I especially like is that I found a use for the not-so-good boring head I bought three or four years ago and that's been on the shelf ever since I got a really good one.

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Nice job!

 

I used to frequent a machine and tool maker's shop in Petone, Wellington. From memory of 25 years ago, from one not familiar with lathes at that time, his ball turner seemed to be a centre bolt in the cross slide with a curved L-shaped tool holder. One leg of the L went horizontally through the pivot and there was a square hole in the vertical leg for a cutting bit with a grub screw to hold it in. The curved piece continued above the bit for maybe 80 mm: this was the bit he held onto to turn the thing around. I didn't see it in operation and have no idea how he set it to accurately turn a ball of a set size, or even it this is a good summary! It seemed a very simple arrangement though. I suppose the pivot would have to be set under the centre of the ball but how he did that is a mystery to me too! I doubt I can ask him, either: he wasn't so young back then.

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That is the basic idea behind the first one I made although mine is much more complicated. I wanted to get away from the business of controlling it by hand...but I've now found that isn't as much of a problem as I'd thought. The major problem I discovered after I'd done all that work is that when the tool rotates horizontally it requires a lot of room between the chuck or collet in order to reach the back. That's not a problem if you are making a threaded ball - you can just attach it to a longer threaded rod but in this case, the part that holds the ball is also part of the finished item and there just isn't much room back there. When the tool moves vertically you can work with much less space because all you have to allow for is the width of the actual cutting tool.

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