JV Puleo

My 1910 Mitchell "parts car" project

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On 12/27/2019 at 8:22 PM, JV Puleo said:

Time and patience are the only commodities I have in abundance.

They’re usually the only commodities I can afford!

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Here it is bored out to 1.850. The leading edge is a bit thinner than I'd like. I feel as if I pushed it as far as I dared. Fortunately the strength of this saddle is dictated by the middle which is about 1/2" thick and connected directly to the web of the crankcase. My concerns are probably more cosmetic than mechanical.

 

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Nevertheless, I took a light facing cut to flatten the edge.

 

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Then dismantled the boring bar. It will all have to go back together to bore the bearing.

 

This is a better view of the saddle. The critical element here is the diameter and I have no way of measuring it accurately. The only thing I've thought of is to make an aluminu7m bearing in the diameter it should be. I will put that in with some Prussian Blue on the faces and seat it under the torque I intend for the bearing. If it contacts all around, so much the better.  If it doesn't, I'll have to make another until I get the exact dimension. That dimension will be used to turn the OD of the bronze bearing. I will also have to make a cap to go over the top of the bearing and everything will be held in place by a bolt passing through the threaded brass sleeve. My intention is to make a special 1/2" bolt with a 1/4" projection that will go into the actual bearing. With that in place it should be impossible for it to shift in any direction. It is not under a great deal of stress so once tight it should stay that way.

 

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Edited by JV Puleo (see edit history)
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The next step was to get an exact measurement for the diameter of the saddle. I started by turning a piece of aluminum to 1.850 - the measurement I aimed for in boring it.

 

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It slipped right in but I had the feeling it was just a very small bit loose.

 

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The bearing will be held in place by a special bolt, under tension so it will press against the saddle. If the measurements aren't perfect the hole in the center will be slightly off. To test this I made a test bolt from a piece of 1/2-20 threaded rod.

 

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Screwed it in and tightened it against the test bearing.

 

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It wasn't bad but under tension there was a slight drag in turning the boring bar passing through it. My guess was that it was about .002 small but discovered I was out of 2" aluminum bar to make another one. So, I ground some flats on the piece of bronze that will be the bearing. These are for registration purposes. They will disappear when the piece is turned.

 

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And in rummaging around, I found another piece of aluminum with a 3/4 reamed hole in the center so I turned that one to 1.852 - I was aiming for 1.853 (adding .0015 to the radius). I tried it in any case ...

 

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And it was perfect. Tightening the bolt has no effect on the bar...so, I guess my boring was fairly accurate given that I had to make the measuring tool to do it. I can now proceed with the split bearing but that will tie up the milling machine and I have a small job to do for the foundry next door that I need the mill for so I dare not set up a fussy job before the tool I need comes in. Thankfully, that should be tomorrow.

Edited by JV Puleo (see edit history)
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Today I tackled the split cam bearing. The first stem was to mill a flat and then put in center holes.

 

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Then the holes were drilled with a #25 drill, the thread size for 10-24.

 

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The piece then went back in the mill to be separated. This was the most time consuming part....small cuts and the saw only runs at 65 RPM. I think this part took about 3 hours.

 

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With one done I turned the piece around and put a C-clamp on the slit side. This is to keep the top half secure while I cut through the other side.

 

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And there are the two halves. Next I have to fit the cap screws that hold it together, bore and turn it round again.

 

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It's an interesting way to finish out the year.

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Posted (edited)

Is the bearing splash or pressure fed? What’s the max rpm of the engine? Will you grind the cam bearing surface and regrind the cam before you finish the bearing to final clearance? From learning things the hard way, I have learned to look long and hard at the cam before finishing the new custom bronze bearings...........been there, done that!

Edited by edinmass (see edit history)
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Posted (edited)

The bearing is splash lubricated. Maximum rpm is probably around 1000 since the cam runs at 1/2 the crank speed. The camshaft is new and is surface hardened and ground all over. I was careful to mike that first. I intend to bore the bearing .001 over and will put in an internal oil groove and oil pockets (or maybe just one pocket depending on the exact location front to back) or I may make a spiral oil groove in it - something I haven't done before. That is one of the experiments I've been working on, with a special oversize spindle gear for the lathe so I can make a very long thread (something like 2 turns per inch). I also have a design of a machine that will put figure 8 grooves on the inside of a bearing but that may be too much to undertake right now although I was thinking of building it to do the main bearings. That said, the engine is along way from final assembly so once this is "done" I can still fiddle with it.

 

I hadn't thought of it but now that you mention it I probably could give it oil pressure. That might be a good idea although the surface speed will be much lower than it would be if the cam had bearing journals that were larger than the lobes and the RPMs higher. I thought of doing that but it seems to harbor too many attendant risks. These split bearings are a chore to make and I wouldn't have minded if I could have avoided it.

Edited by JV Puleo (see edit history)
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When re-engineering anything with splash lubrication there is a high possibility of causing problems that can’t be foreseen. Often times there is a cup, recess, or other groove cut into the top or side to allow oil in, and with engine modifications often times the original design of some small item that is unknown and impossible to see will change the way oil splashes and cause a lack of oil failure. Guess how we learned this problem............the upgrade we did was designed by an experienced engineer and rebuilder..........and still failed with modern oil. If possible and not terribly difficult, I would run pressure to it. For splash, your going to need to run it with more clearance. As I’m sure you are aware, oils primary function is cooling..........and lubrication is secondary. That bearing location in you block doesn’t look like it is “over lubricated” with a splash system. Ed

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Posted (edited)

I'll be surprised is something doesn't fail. I've simply made too many parts to presume that all of them will work as intended. I'm just hoping that whatever does fail doesn't cause catastrophic damage. I do think that can be avoided though or I wouldn't be doing this.

 

Edited by JV Puleo (see edit history)
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I think you will be all right, you just have to try and think of 100 different problems that can pop up. Your skills are excellent, and taking your time is a big advantage. If you want to run a brass car hard, which almost everyone does, weather they know they are or not is another issue.........taking advantage of a pressurized system is a great option. You don’t need a huge oil supply there.......and the up side of pressure with all you modifications would be a plus. Modern oils will also be a huge benefit. I think running you engine for ten or fifteen hours at half to two thirds throttle before you try driving the car would make thins much easier to sort and deal with. 

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Posted (edited)

That is pretty much the plan...though I'm not enthusiastic about building an engine test stand and I'm a long way from being able to use the chassis. Actually, the chassis cannot be moved from where it is without picking it up. If there were wheels on it it, it wouldn't fit through the door.

 

In it's final form, the bolt that holds the bearing in place will have a 1/4 or 5/16 extension on the end that will go into a reamed hole in the bearing. The original intention was to make certain the bearing could not shift forward or back but I don't see why I can't drill the center (very small) and feed oil through it. The only question is how to connect the oil line to the top end of the bolt...maybe a small banjo fitting like those used on brakes. I'll think of something.

 

Thinking constantly of what can go wrong is one of my habits...it often keeps me awake at night but I admit it has also allowed me to dodge a lot of bullets. What would use for a rear main seal material? I'm thinking of either graphite rope or felt and I'd prefer felt as that was a common and effective seal at the time. I am wondering how it works with low oil pressure as my experience with felt seals is mostly on non pressurized systems...keeping in mind that the pressure will not exceed 15 lbs and may well be lower.

Edited by JV Puleo
typo (see edit history)
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Hello Joe,

 

Thinking about your pressurized system... I know there were a number of cars with just

a spiral groove to pull the oil back in. I believe Austin Healey "Bug Eye" Sprite comes to mind.

 

On the Mains and Rod bearing shims will you have the babbitt tips? These are supposed to

keep oil where its needed. Here you can see one of the tips and the round hole and slot that

provides a mechanical lock to the shim. There appears to be a punch mark to upset the babbitt.

 

Don't loose sleep. Its only an engine. As one person once said "Do something. You can always fix something but you

can't fix nothing." 

 

Greatly enjoying watching progress!

 

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Posted (edited)

I hadn't really thought much about shims and I may very well do without them.We'll have to see how the shells come out before I consider that. RR used quite thick shims with the edge Babbetted and I've always wondered what the idea was. The only way you could adjust them is with a surface grinder. I think this car had brass shims at one point but it was obvious that someone, not the seller but whoever he got it from - just slapped the engine more or less together to sell it. I don't really know if all the engine parts I got with it came from the same car.

 

I did make more progress on the bearing today. I flattened the faces. They were quite good but it would be impossible for the slitting saw to give a really flat surface. First I worked them on the bench top with 120 sandpaper. (The bench top is an old surface plate - not accurate enough to serve as one but good enough for this purpose.

 

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Then finished on the lapping plate. Since they were quite good to begin with so this didn't take hours.

 

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Then I tapped the holes in the lower half.

 

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When that was done I lapped the top half and drilled the holes out to clearance size for the cap screws.

 

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The most fussy bit was counterboring the holes. This has to be done so that the thickness of the bottom of the bearing half at the hole is .150. I may have come up a bit short. If so, I can deepen them a bit more after the diameter has been reduced. I must have 40 counterbores and never the exact one I want. There is very little room to spare with this bearing...

 

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Nevertheless, it went together just fine.

 

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Last, I made a tool for indicating the bearing in the 4-jaw chuck...it is round to the small dimension of the now oblong hole and should be tight. I must have measured incorrectly because I hit the measurement I was aiming for right on but it's a few thousandths too small. By now, it was approaching the end of the day so I thought I'd quit while I was ahead and finish tomorrow. I'll put a knurl on this to raise the surface slightly and I think that will suffice.

 

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Edited by JV Puleo (see edit history)
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Do you have a feed rate on your mill for a 3 hour cut or did you have to advance that manually?   Probably a silly question but now that I have a mill that I'll hopefully be using this year, just about any post with a mill in it catches my curiosity. 

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For the 5" cutter with 40 Teeth, 65 RPM and a feed rate of 4.8 inches per minute. I think I used 3-/12 inches per minute but the cuts are extremely small, maybe .025 to .030. I have no idea what sort of cut will work though I assume they could have been bigger. But, the small cuts give a smooth surface and clean slot so anything that you might gain by increasing the cut may well be lost if the two slots are a little rougher. One of my problems is that I've never seen it done by anyone who knew how to do it so I'm making it up as I go. Also, I'd rather take the time and know it will come out good than push the envelope and have to do it over.

 

It was all done with the power feeds. There are on-line calculators for cutter speed and feed rates that  I've found very helpful. The first time I used a slitting saw I ran it much too fast and shattered the saw...an experience I'd rather not repeat.

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2 hours ago, Terry Harper said:

Hello Joe,

 

Thinking about your pressurized system... I know there were a number of cars with just

a spiral groove to pull the oil back in. I believe Austin Healey "Bug Eye" Sprite comes to mind.

 

Not being an engineer, I've no idea how you would calculate doing that. The engine does not appear to have any seal but it had a drip oiler that added oil in very small amounts so the grooves in the crankshaft that directed it back into the engine were probably sufficient - though again, we don't know how much they leaked in period. I'm guessing they not only leaked but laid down a cloud of oily smoke. One of the period comments you see consistently is that most people over-oiled their engines - oily exhaust being a lot cheaper to deal with than melted bearings.

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Posted (edited)

Hello Joe,

 

I did a bit more research out of curiosity. MG used the scroll and slinger setup for quite awhile.

However, for it to work well it requires tight clearances. (.003 to .006 for the MGA)

 

Running, the system works quite well but will drip when shutdown. On the MG its actually threads with a form that

has the crest forming a flat and a sizable radius forming the root .

 

The disk to the left of the scroll is the oil slinger.

 

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I almost think my Wisconsin uses something similar but I would have to check. I remember there

were no seals or packing.

 

Not sure how you would retrofit an existing crank for a setup like this.

 

T.

Edited by Terry Harper (see edit history)

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Heldt illustrates something similar in 1910. I can't think of any way to retro-fit an old crank either. My feeling is that I should use whatever works, that I can fit and is appropriate for a low pressure, relatively slow turning engine. A google search turns up several references to felt seals in International Harvester tractors but, of course, the discussions always presume the reader is thinking in terms of the same engine. So far I've found nothing in the way of engineering data on older seal systems.

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Hello Joe,

I will send over a few pictures and some direct information that we used to install a felt seal cartridge into the rear main seal area of the Locomobile block and it does stop oil migration out the rear main!  I also did add full pressure to my Locomobile and have it set to run at about 25 lbs when hot and with modern oils.

Regards,

Al

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I put a knurl on the centering tool. This didn't work quite as well as I'd hoped but it did work. In fact, after it was knurled it was too tight.

 

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It centered but I suspect it was still off center a little.

 

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I started boring. Because the hole isn't round and I'm limited by the diameter to the size of the boring bar , it deflected quite a bit. I stopped in the middle of this operation to readjust the piece in the chuck. That corrected the problem and I bored the hole round.

 

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Once it was round, I drilled and reamed to 1" + .001.

 

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Then turned the OK to match the aluminum piece I'd made. I rechecked this four or five times to make certain I had the right number. Oddly enough, it turned out to be 1.851 - exactly .001 larger than the dimension I was aiming at so apparently my shop make boring bar adjustment tool is better than I'd thought.

 

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I hit the dimension I was aiming at dead on. Here's the finished bearing.

 

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And in the engine. Tomorrow I will make an aluminum cap for the top side so that the bolt will be pushing against the entire saddle rather than in one spot. I'm taking Edinmass's suggestion to run an oil line to the bearing. If it has oil pressure, I doubt an additional oil groove will matter.

 

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My apologies if you mentioned this earlier... did the casting for the center cam bearing break and that's the reason for your support?  Looks like a nice solution to the problem if that's what it is.

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Jeff...if you go back to page 58 you can see what was there. The saddle was Babbitt lined and there was a spring loaded cap that pressed down on it - also Babbitt lined. Aside from the fact that I have no idea how you would renew the Babbitt in that spot, I thought it was a cheesy center bearing...certainly prone to bounce as pressure increases and decreases on the cam shaft depending on which valves it is opening. I never liked it and spent a good deal of time trying to think of a way to replace it with something more substantial. Based on the figures in Heldt, it still does not have enough cam bearing surface but this is the best I can do.

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If you pressure feed it I would run it at 1 1/2 to 2 with the oil grooves, 1 is too tight for me,.,......splash or fed.

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1 hour ago, edinmass said:

If you pressure feed it I would run it at 1 1/2 to 2 with the oil grooves, 1 is too tight for me,.,......splash or fed.

 

Thanks Ed. I wouldn't have guessed that much. I will leave it as it is for the time being and hone the bearing out when the cam is fitted...if .002 is ok that makes alignment all the easier.

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Joe, I just re read this full page 60 of your cam bearing redesign.  What a novel approach to an other wise "tough" situation!  I share the thoughts of Ed, pressure oiling will be a good thing...in my opinion.  You have addressed the cam center bearing as well as how to keep it in place.  Are you going to install an alignment dowel to assist with keeping the bronze bearing aligned or are you going to rely on the four positions of the clamping bolts?

Al

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Thanks Alan. That is an easy question to answer. I'm making a cap to go over the top half of the bearing to distribute the pressure of the clamping bolt more evenly. The bolt will have a 5/16" projection on the end that will pass through the cap and into the bearing about 1/4" - more than enough to keep it in place but nowhere near enough to come in contact with the camshaft. I will drill a 1/8" hole through the center of the bolt. The head of the bolt will be fitted with a small banjo fitting (Mike West is sending me a couple Franklin brake system fittings). The oil will come from the line that feeds the center main bearing - another fussy job I've yet to do because it involves drilling a hole through the crankcase into the bearing.

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