JV Puleo

My 1910 Mitchell "parts car" project

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I'm not either which is probably why I was never attracted by engineering. As it is, I keep two calculators on my workbench, double check ALL my numbers and make written notes as well and I still make errors.

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Starting the re-design. The first step was to take a piece of 1" bar and turn it down to .750 + .001

 

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Then I put it back in the lathe, faced off the bit end and drilled it through at 3/8"

 

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I then turned it around and threaded it 3/4-16 - the standard 3/4 fine thread since I don't want to be bothered making a nut in an odd size.

 

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I was lucky I had a fine thread nut to test it with. Otherwise, I'd have to have ordered some and wait to do this part.

 

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Then I drilled it about 2-1/4" with a 7/16 drill. This is only to serve as a guide for the broach. I'm only broaching the head of the pin...there is no need to try to force it through the whole length.

 

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I started the broach in my arbor press then moved over to the larger press...

 

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And that's it. Now I have a pivot pin that is .001 oversize. This went much more smoothly than most jobs...

 

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The metal is 12L14 - free machining steel. Were this an industrial job you'd want a tougher metal, probably hardened and ground but how much is this going to be used if it does work? I can't imagine wearing it out but if I do, I'll just make another.

Edited by JV Puleo (see edit history)
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With the new pin finished, I now have to get the other parts ready. The first thing I did was correct the odd error I made in milling the radius on the lower section of the tool. The 1-1/2" end mill I used was tapered. I've never seen a tapered end mill aside from one for cutting dovetails and the taper is very shallow. In the end, this actually was a help because it forced me to make the slide larger and to work n the dovetail I made but I wanted to correct the problem where it showed. To center the piece I used this 3MT center, turned down to 3/4".

 

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Which allowed me to set it up on the rotary table so that the radius would be uniform. You can see the odd tapered cut clearly here.

 

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I then reassembled the pieces and clamped them up in the drill press to drill and tap a hole for a bolt that will attach the upper and lower pieces securely, The idea is to get them so solid that when I drill and ream the holes for the pin it will be as if I was drilling a solid piece of metal. This is the only way to keep all the pieces in perfect alignment. First I drilled a 5/16 hole through both pieces.

 

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Then swiveled the upper piece out of the way and tapped the lower one.

 

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I drilled the upper piece out to 3/8" and bolted them together. With them securely in place, I was able to get a good reading for the depth of the bushing I'll have to make.

 

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I'm making this bushing out of aluminum just because it is easier to work. The depth is calculated to allow for a .125 bronze thrust washer between the bushing and the gear.

 

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All of which takes a lot less time to explain than it did to make it. I always have a problem reading my depth micrometer - it works backward from a conventional mic and for some reason, I always find it confusing. In any case, I took my time and it came out to exactly the measurements I wanted.

 

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This was made to be a very tight press fit. I think it's OK... the real test is to see if I can put the pin back in with everything bolted up.

 

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Which, thankfully, it did although it isn't as loose as it was. This is a good example of trying to make something that is actually more precise than the machines I'm making it with. That is really the essence of manufacturing...unless we could do that, we'd still be in the stone age.

 

 

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Now I have to set everything up in the drill press again, drill and ream the hole for the pin, press in bronze bushings and lap the holes so that the new pin has an extremely small clearance.

 

 

 

Edited by JV Puleo (see edit history)
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I like quiet days in the shop... which this is because everyone else is off doing Christmas stuff. With the two pieces of the radius tool clamped and screwed firmily together, I located the center of the pin hole.

 

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And using that setup, drilled and reamed the holes to 7/8". I then pressed in 7/8 x 34 bushings... but it looks as if I forgot to take a photo of them. I did discover that the press fit reduced the ID of the bushing very slightly so that the hardened shoulder bolt now fits somewhat closer than it did. I've decided to test it with that bolt in place rather than hone the bushings for the new one I made. If it works, all is well. If it doesn't, I still have an alternative. At this point, I'm waiting on a thrust washer which was supposed to be delivered today but since the building is closed up, I suspect I'll have to wait until Wednesday for it. In the meantime, I decided to drill and tap the holes that will hold the offset plates in place.

 

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I was going to clamp these together but the press is so tight that I took a chance and drilled the holes as is. These are 5/16" holes, the drill size for a 3/8-16 thread.

 

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Then removed the upper plate and tapped the holes.

 

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The other plate was then drilled to 3/8"

 

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And the holes counterbored for the heads of the cap screws.

 

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They look pretty good. The fit is so tight that I doubt any welding will be needed.

 

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Here it is set up on the lathe saddle.

 

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Next I have to do the lower section. This is a little more tricky because it's longer and has a rounded end. I have to give that some thought but at this point I think that as soon as these holes are in place and the thrust washer arrives I'm ready to test it.

 

 

Edited by JV Puleo (see edit history)
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Looks great!  Seeing it on the lathe gives a lot of context.  What's the big slot on the bottom for?

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The piece that swivels is attached there. The whole thing is cantilevered so that it fits under the piece being turned.

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I then drilled and tapped the holes in the lower plate. In this case, because the end is rounded, I had to use this old B&S Milling vise so I could put a square up against the side to get it straight,

 

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Then, because I had time, I put a hole in the center of the short piece... just to lighten it a bit and for looks. As you'll see, this was a mistake.

 

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Because I then did a trial assembly...

 

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And discovered that I'd miscalculated the offset... it's about an inch low. If I hadn't drilled that hole, I could just shorten the piece. Now I have to make it over.

 

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You're just making the cantilever piece over, right?   Obviously you'd like it to be perfect the first time, but making that piece again isn't too bad.   When you make it a little shorter, might you also add a piece to rest against the saddle?  Perhaps make the piece that hangs down thicker such that it naturally rests against the saddle?  Looks like that would provide a lot of support to offset the downward force from the cutting tool... though I may not understand how it works.

 

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That's a good idea. I'll make a piece that will go up against the front of the compound when it is all bolted up. After I posted the above the thrust washer I needed arrived so I was able to fit it and do a quick adjustment. I don't think it could have come out any closer...there is about .003 to .004 clearance between the upper and lower pieces. I still have a slight binding problem but I think I'll remedy that with a little lapping.

 

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The replacement part is all set up in the mill but its the end of the day and I don't want to make another error so I'll leave that for tomorrow.

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Here's the old piece and the new piece. I learned something here. When I made the original piece is was very careful to mark the holes precisely although they were drilled with the piece they attach to. When I made the new one, of course, the threaded holes were already in place and I was worried that the new holes would be ever so slightly off and it wouldn't go together as it should. I was very relieved to find that the new piece fit perfectly.

 

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Then I assembled the device on the lathe. Now is the real crunch. I have to test it. It certainly looks good... whether it works as well is yet to be discovered.

 

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It works - but not very well. There are some problems I will have to address but I want to give it a rest and come back to it rather than charge in.

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49 minutes ago, JV Puleo said:

It works - but not very well. There are some problems I will have to address but I want to give it a rest and come back to it rather than charge in.

 

That's fairly typical when I create something of that complexity.  I figure if I can get it close to working then a few tweaks will usually get it all the way there.  Hopefully that's the case for you as well... it certainly looks like a solid tool.

 

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I am reasonably certain I can get it to work but there is a problem with tool geometry that I hadn't anticipated... because of the diameter of the headstock spindle, it is hard to get the cutting tool to the back of the workpiece. I have an idea - and I'm going into the shop today to fiddle with it. If it works it is so simple I'll be having one of those "DUHH!" moments.

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It looks as if missed a crucial element of design in my radius turner. They are mostly used to make balls with threaded holes for machine handles. When you do that, you drill and thread the hole first and then screw the piece on to a bolt or threaded rod which can be held in a chuck or collet. What I failed to notice was that in almost every case the ball projects some distance from the chuck. The problem I have is that I'm making Banjo fittings. There is no threaded hole and the projecting piece that I have to hold the ball with is short. The trick is getting a tool that will work in the small space available. So, I'm now making a different type of device using a boring head. Fortunately, I have an extra boring head - a cheap import I bought years ago. I used it a few times and then decided that if I wanted to do precise work, I had to get a good one. The old one has been on the shelf ever since so the expenditure for making this thing is minimal. This type of ball turner won't make concave surfaces but I think the need for that is minimal and not difficult to do in other ways.

 

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Rather than beat my head against a wall I've decided to try a much simpler radius turning idea. It relies on using a boring head and, as luck would have it, I have an extra one. It's a relatively cheap import. I used at a few time and decided that if I wanted to do better work I needed a better boring head. The one I'm using on the mill was welded to its holder meaning it will only work in a 50 taper machine - which is what I have and why I got it fairly inexpensively. This one has been on the shelf for two or three years. The arbor is 5/8" - the largest collet my old vertical milling head could handle. In order to be able to adjust turning pressure, I wanted a larger radius so I bored out a piece of 1-1/4 ground stock and made a sleeve to fit over the arbor. It is secured with 4 flat head set screws sunk below the surface. Unfortunately, I didn't have the stock I need to finish this and had to order it and, with the holidays, it will probably be late next week before I can proceed.

 

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Posted (edited)

I'm still waiting on some materials to finish the ball turning device so, rather than waste time, I decided to take the oil pump apart. I ran it aproximately10 hours on its test stand at which point it developed a clicking noise and would occasionally stick. Obviously, something was wrong but I didn't want to tackle it until I'd finished the ball turner. It looks as if the oil mixed with abrasive wasn't a very good idea... I also think that the vanes are too short, which presents a problem but I think I've got a solution. The sticking vane put a ridge in the lining of the pump housing. I'll simply bore this out. There is plenty of bronze to take another .025 off and get it smooth again.

 

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You can see how the abrasive ate away at the vane...

 

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So, I designed a new rotor that I think will be a major improvement. This time I'll have 4 vanes, they will be thinner and longer. The one drawback is that I'll have to turn down the end of the camshaft to 3/4" but I don't think that is much of a problem since it has to be modified in any case as it is too long. When we made it, we copied a camshaft from a later car and somehow I failed to notice it was longer than the original. The cam lobe spacing is identical so it is just a matter of extra length on the back end.

 

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Since the volume of oil the pump delivers is the difference between the diameter of the housing and the area of the lobe, this one should also deliver more oil. It is a bit tricky to make but I made some good progress today.

 

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The new rotor is on the right. The square piece of aluminum next to it will be an alignment tool to make sure I have the piece absolutely vertical on the mill table. I'm going to be using the dividing head this time to index it but it will have to come out and go back in at least once so it is important to be able to get the slots for the vanes vertical.

Edited by JV Puleo (see edit history)
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I do think you will end up with a more balanced system using four vanes and having them thinner in cross width.  All the vane pumps, I have been involved with, had 1/4" or thinner vanes and fit deeply in the rotor to stop the potential binding as they loaded and unloaded during rotation.  Keep up the good work!

Al

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Thanks Al. I'm certain you are right. It may be that I was interpreting the early illustrations I was looking at too literally. They were really just to show how the pump worked and not necessarily what any real pump looked like.

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I think you should not have a "hole" at the inner end of the vanes. You want maximum support for them as Al said so that when they wear a little, they don't rotate in the slot like the last ones did, probably increasing the wear rate. Long and narrow. Think of how piston rings work.

 

Maintain full control while lapping the vanes to the pump body if using an abrasive.

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I wondered about that too but the holes are copied from a pump I have - and that I only "discovered" this past week. It's been laying on the floor of the shop under the line boring machine for some time and is one of those things my friends drop off saying something like "you'll find something to use this for." (Which does happen occasionally) I suspect they have something to do with lessening drag on the vanes if they are going to work by centrifugal force but, not being an engineer, that is just a guess. In any case, I have enough material to make this several times and, since the rest of the engine is a long way from being complete I have time to keep trying to get it right.

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Here's the vertical alignment tool having the edges milled. The idea is to get them perfectly perpendicular to the holes. I don't think it worked as well as I'd hoped.

 

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When it was done, I checked each side on the surface place. One of them was virtually perfect so I've marked that with an X. I also made an alignment fixture for reboring the pump body. The hole isn't exactly round due to the wear the abrasive caused so I chose this method over using a neat tool called a coaxial indicator... which works fine but depends on the hole in the center actually being round.

 

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I got out the fixtures I'd used to make the pump body and set it up. I aligned the 1" hole in the fixture with a 1" tool holder. When you do this, you can get it close by moving the table then wiggle it a bit by hand and tighten the hold downs. It works quite well. Boring shows up the wear on the lining of the pump body...

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I had to take it out about .035 to .040 to get the surface completely round again.

 

 

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Seems like a lot of wear, were you expecting that much or was that part of the problem?  Will you change the mixture when you  break it in the next time or run it for a shorter period?

 

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Posted (edited)

I certainly wasn't expecting that much wear. I was surprised by it. I'm not bothering with the abrasive next time around. I think I can get the sliding surfaces perfect enough so that no "break in" will be needed and I'll test it with just 20W30 motor oil. If I was going to do the abrasive thing again, I'd probably go with rottenstone – which is finer – but I don't think I'll need to.

 

Edit: I just did some quick calculations. In the 8 or 10 hours it ran on the test bench the rotor turned between 250,000 and 360,000 times. I'm guessing the abrasive - as fine as I thought it was, was much too coarse.

 

Edited by JV Puleo (see edit history)
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I've also decided to take Spinnyhill's suggestion and make a rotor without the holes at the base. The setup to cut the slots will be identical so making 2 rotors will not be much more work.

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