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tomw

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#1
Dear All,

I have decided to post a build log of my attempt at making this engine:
STEAM-ENGINE-7.jpg

from PMRs casting kit. I chose this engine because it is really two engines that have been joined together, giving me twice the opportunity to learn how to do things.

Also influencing my decision is the build log by this fellow: deansphotographica.com. He built his PM #7 engine using Taig equipment with some custom attachments. I am going to be using Sherline equipment (a 4400 lathe and a 5400 mill). I also have a rotary table. Thus, some of the operations will differ from his build. However, the order that I complete tasks will be largely the same as the order he used.

I started this project on August 24th, 2015. Therefore, the first few posts will be catching up to where I am now.

I am very new to machining, having bought my lathe in January, and my mill in March, of this year. Therefore, I am looking forward to hearing peoples comments on my techniques and strategies. Any and all constructive criticisms are highly welcome.

Thank you for following along.

Cheers,

Tom
 

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Terry Werm

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#2
First off, Tom, welcome to the world of hobby machining and model steam engineering. I think that you will find your newfound hobby to be very enjoyable. I for one will be following along on your build as miniature steam engines are one of my favorite subjects.
 

tomw

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The first part I did was the base. Here is the drawing for the base, and the casting as received.
PM #7 base drawing.jpg

PM #7 base raw casting.jpg


First I took some preliminary measurements to see if any part of the casting was clearly faulty. I was quite pleased with its squareness and uniformity. I decided then to sand the bottom of the base flat, giving me my first reference surface. I did the sanding on my surface plate with 320 grit Aox paper and WD40 as a sanding fluid. I used the figure eight technique, and also rotated the base 90° every 20 or so circuits. I let gravity be the arbiter of how much pressure was applied. This took me about 45 minutes, but I got a bottom surface that was flat with about 90% contact.
Sanding bottom of casting flat.jpg

I then mounted my "big" angle plate to mill table and indicated it to normal of the X travel. I then clamped the base to angle plate and shimmed it so that the short edge marked x above was parallel to the mill table.
Setting up angle plate on Sherline mill.jpg

Facing outermost  drive shaft journal boss.jpg

I then used my 1/2" end mill to face the drive shaft journal boss. I aligned the mill to the boss by eye, such that it would not leave any crust on the "top" (see photo above). The base was then rotated 180°, and the other boss was surfaced.

The center of the drive shaft is the main reference point for determining most of the other features on the base. Thus, I locked my X and Y at this point, as the center of that boss is going to be the center of drive shaft journal. The entire distance from the outside of the right most journal boss to the outside of the left most boss is over 4". To drill the shaft journal and have it be fairly straight is a challenge. I used the approach as outlined by Dean here. Basically, I would center drill the boss, drill it 3/16" through, then put back in the center drill and center drill the next boss in line, followed by another 3/16" drill through, etc. The trick for the further away bosses was to use extra long bits. Unfortunately, I took very few photos of this process. Fortunately, Dean has plenty.

Center drilling first boss.jpg

Drilling 3-16 " in first boss.jpg

Center drilling into second boss.jpg

Using 6" long center drill to drill 3rd boss.jpg


I decided at that point to make a custom fixture/jig for the base that I could mount to my Sherline angle plate (with handy T slots). This is just a piece of aluminum plate that was made square and flat. Of course, making a piece that big square and flat in a Sherline mill took me most of an afternoon! I fit up the base to the plate so I could machine the cylinder mounting bosses. Here, I used shims to get the drive shaft (which I put through my newly drilled journal bosses) level to the table. I did this on my surface plate with a height gauge and some brass shim stock. Once everything was set, I clamped the base to plate. As long as I used the same set of shims, and placed the base in the same place, I could take the base off the plate and subsequently remount it square. You can see in the photo below the black lines on the fixture, and the shims at the bottom right corner of the base, for alignment.

Clamping base to custom fixture-jig.jpg


I then took a skim cut of the cylinder mounting bosses to make them flat.

Taking a few skim cuts on cylinder mounts.jpg


After that, I removed the base back to the surface plate, and using my height gauge I marked the vertical position of the cylinder mount through-holes. Using a steel rule, I then found the center of this line on each boss and center punched it. The base was then remounted to the angle plate on the mill. I then used my long center drill bit and a .010 feeler gauge to find the center of the drive shaft and set my Y axis to zero on my DRO. Basically, I brought the center bit towards the shaft until I could just feel resistance as I moved the feeler gauge. The amount of resistance is about what I would use when setting points on a distributor (for any young-uns wondering what are points and distributors, ask an old guy). I then subtracted .010 and half the diameter of the drill bit to find the center of the shaft.

I did this complicated bit of metrology because I could not get my edge finder even close to the shaft.

Finding center height of drive shaft.jpg

Marking drive shaft center on cylinder mount bosses.jpg

Finding drive shaft datum.jpg

I apologize for the fuzzy image. And for all future fuzzy images. A drawback of using an iPhone camera and not focusing.

Once the shaft center was found, I used a wiggler to find my center punch marks on my the cylinder bosses. Using a center drill and then a 1/64 under bit, I drilled out the cylinder mount through holes. The entire rig was then flipped around, and the holes were reamed to size. I had to flip it around, otherwise I did not have the vertical clearance on my mill for the reamer.

Center drilling cylinder mount boss.jpg

Drilling cylinder mount hole 1-64" undersize.jpg

Reaming cylinder mount holes to size.jpg


Until next time:

The base so far.jpg


Thank you for following along.

Regards,

Tom
 

tomw

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#4
Terry, thank you for the welcome. I am definitely enjoying myself.
 

tomw

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Upon re-reading my previous post, I forgot to mention that once the drive shaft bosses were drilled 3/16", I used a 3/16" drill rod to check that the drilling operation resulted in a straight bore. I then went back, and with a 15/64" long drill, through drilled the bosses. I then reamed the bosses 1/4". Again, this is the same approach as taken by Dean of Idaho.

Unfortunately, at the time I was not thinking about making a photo log of this build. Thus I don't have photos of the final drilling and reaming operations.
 

BRIAN

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#6
Hi Tom,
Nice work and careful planning, I like your Jig It will help a lot as you go along.
Thanks for taking the time posting your project. .you have me hooked.
Brian..
 

savarin

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#7
got me hooked thanks.
 

tomw

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#8
In this post, I go through finishing most of the machining on the base casting. The first task was to remount the base flat on the mill table and use an indicator to get the drive shaft parallel to the table (x-axis). I did not need a jig here, as it mounts easily with some strap clamps directly to the table.

The first thing I wanted to do was finish machining the cylinder mounts. The thickness of the cylinder mounts is determined by the distance from the face of the mounts to the horizontal center of the crankshaft (drive shaft). Thus, I found the center of the crankshaft using an edge finder and set the Y axis on the DRO to zero.

Finding the center of the drive shaft.jpg

Finding the horizontal center of the crankshaft.

I then put in my trusty 1/2" end mill and cranked forward on the Y axis 3.25"+.25" and made note of the DRO reading. I then cranked a little further and touched off on the face of the cylinder mount. I need to take about 60 thou off. I did this in 20 thou passes, using a spindle speed of around 400 rpm. Deeper cuts produced unsatisfactory vibration, a drawback of such a small mill. The last pass I made was 5 thou, at 700ish rpm and a very slow feed to get a nice finish.

Milling the face of the cylinder mounts to final size.jpg

Milling the face of the cylinder mount with a 1/2" end mill.

Cylinder mounts milled to final size.jpg

The faces are completed

Mmmm, smooth.

Now it was time to mill the crosshead ways. The reference data for the crossheads are the vertical centerline of the crankshaft and the horizontal centerline of the cylinder head mount through-holes. To find the vertical centerline of the crankshaft, I brought my end mill toward the top of the crankshaft as I moved a small bit of paper back and forth underneath it. When the paper was grabbed by end mill, I knew the end mill was .003 above the shaft (the paper is .003 thick). I could then crank down the z-axis .128 and set my Z axis DRO to zero.

To find the horizontal center of the through-holes, I placed the shaft one of my end mills into the through-hole (which are 3/8 dia). The fit of the end mill shaft was very tight in the hole. I then used my edge finder and a little arithmetic and voila, the center was found.
miracle_cartoon.jpg
Obviously, I had to repeat the above to find the horizontal datum for each cylinder mount. One center was used as the X axis 0 on my DRO, the other center I recorded carefully on a torn piece of oily paper which I frequently placed under my stool (the kind you sit on, not the kind you give as a sample to your doctor when you have giardia).

Finding the center of the cylinder mount hole.jpg

Finding the horizontal center of the cylinder mount. That is a 3/8" shank end mill in the hole.

Before proceeding with milling the crosshead ways, I decided to clean up the oiling points on the top of the crankshaft journal bosses. I positioned the cutter horizontally by eye. The final height was determined by the first boss I milled. These were just careful plunge cuts.

Cleaning up the oil cup mount points.jpg

A very clear shot of some strap clamps.

The rest is pretty basic milling. The important bit for me was keeping track of where I was in three dimensions relative to my reference points. You may notice that I milled the outer edge of crosshead rails. This is not what is called for, but I think it makes a neater appearance. If I was a tiny foreman running a tiny factory, I would have wanted it done this way.

Milling the top of the crosshead way rails.jpg

Smoothing the tops of the crosshead guide rails. I am using a 1/4" end mill.

Milling the crosshead ways.jpg

Milling the crosshead ways to the correct width and depth using a 1/4" end mill.

I then drilled the mounting holes for the crosshead caps and the oil cups on the crankshaft journals. The placement of the holes for the caps is relative to the centerline of the cylinders and the machined face of the cylinder mounts. The oil cup hole placements were determined by eye in the x axis and on the horizontal center of the crankshaft. I then tapped all the holes. The oil cup holes were tapped 2-56, and the crosshead cap holes tapped 5-40, per the drawing.

More crosshead way milling.jpg

Center drilling the mounting holes.

Tapping 2-56 for oil cups.jpg

Tapping the oil cup holes for 2-56 threads. I am using my tapping rig*, a very handy piece of equipment.

Crosshead rail mountings are tapped.jpg

Crosshead cap holes are tapped for 5-40 threads. I think those are pretty darn smooth crosshead ways.

So, after all that, I ended up with a base that was largely machined except for the holes needed to actually mount the cylinders. As I figured out later, I should have done these now. Dean of Idaho did them later, but I think that is because he does not have a DRO, which makes finding the hole positions on a bolt circle pretty easy.

Until next time:
Crosshead ways are done.jpg

Cheers,

Tom

*I have no financial interest in this company. Just a happy camper.
 
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kvt

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#9
congrats on getting started, I also am doing the same PM#7 with a Sherline 5400 Mill and 4400 lathe. Question, How did you do the crank or do you have the extended axis on your mill as my stock one is not tall enough to set the thing on it's side and get a drill through it. I'm looking at mounting it on the lath so that I can drill through all 4 post. Second where did you get the long center drill and long bit from.
I have not taken any pictures yet. Keep forgetting phone and don't have a camera. but have less of the main casting done than you do. So I will be watching what you do.
 

tomw

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Ken,

I did get the extended column. It really makes a difference in what you can do with the machine. If you are heading to Austin anytime soon you are welcome to use my mill to do the crank bores. I think that is the only machining steps you really need the extended column for. Of course, it is pretty handy for other steps as well.

I got the long center and twist drill bits from McMaster Carr. The center drill is part number 2915A35 and the twist drills were part numbers 2986A21 and 2986A24.

It has been a fun build so far.

Cheers,

Tom
 

tomw

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A quick note: I realize I am putting in a lot of detail in the text. For those who want to skip this detail, I am now including captions on the photos. The captions are in a different font to help distinguish them from the main text.

Next up is the flywheel. This one was pretty simple, though my explanation below may not be.

Flywheel casting.jpg

The raw casting. It is bronze.

Because I don't know flywheel terms, nor can I find them on the web, I am going to use the terms as indicated below. Hopefully that will help things remain somewhat clearer than mud.

Flywheel terms small.jpg

What I call the parts of the flywheel

I started by chucking it in the three jaw chuck from one side. I spent quite a bit of time getting it set up so the hub rotated close to the center by trying different angular positions until I was satisfied.

Flywheel in the 3 jaw chuck.jpg

The flywheel freshly chucked up in the lathe

Since there is a casting draft on all surfaces, I did not feel this was the most secure arrangement. Therefore, I took some very light cuts on the inner rim at a slow speed and feed until that surface was clean.

Cleaning up the inside rim.jpg

Making very careful cuts on the inner rim to create a better clamping surface for the chuck.

I then flipped the wheel over and re-chucked on the newly cleaned up side. I then cleaned up the inner rim, the rim side, and the sides and face of the hub. I cleaned up the the outside rim of the wheel using the Sherline compound set at whatever angle was called for (I think 5°). I made sure to cut deeply enough to go over the centerline, and and then I carefully noted the final depth of cut. This way by cutting to the same depth on the other side I could be reasonably sure to have apex of the wheel centered side to side.

Both sides of inner wheel cleaned up.jpg

Cleaning up the surfaces of the flywheel rim


Tapering surface of wheel with compound.jpg

Cutting the outer rim taper using the Sherline compound. This compound mounts on the back of the cross slide and the tool is mounted upside down.

The hub center drilled, drilled and reamed to 1/4".

Center drilling hub.jpg

Center drilling the hub.

I then finished facing the rim side until that was nice and clean with a nice clean meeting line to the outer rim. I recorded the distance from the spoke base to the edge of the rim (the rim inside depth).

The wheel was then flipped again, the rim side faced to create a rim inside depth that matched the other side. The outer rim on this side was cleaned up using the compound as previously described.

Then it was over to the mill to drill the hole for the hub grub screw. I mounted the three jaw chuck, with the flywheel still in it, to my angle plate. I used the crankshaft to center the flywheel hub hole under the spindle. Using the long center drill, I spotted the hole, and then drilled it out and tapped it. Pretty slick, really.

Finding centeral axis of flywheel.jpg

Indicating the spindle on the center of the crankshaft to find the center of hub.

Center drilling flywheel hub.jpg

Center drilling the hub for the grub screw hole. This was followed by drilling and 5-40 tapping.

Progress so far:

Build so far.jpg
Flywheel terms.jpg
 
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Hawkeye

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#12
Doggone it, Tom. Why'd you have to go and show us this? I've already taken a look at the PMR web site. That looks like a great project to take on.

Seriously, thanks for sharing. I'll be watching your progress. Might just have to join you. Your detailed tips will make it easier for any who give it a try.
 

kvt

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I may have to take you up on coming to see you unless I can get the extended col for my 5400, Found I need it even to do the holes for the piston rod and end cap, I guess I could do it on a drill press or something, but that would not ensure they are correct. Also had to stop and working on my laptop as it cratered on me. (using wife's now) so my fun budget just got cleaned out.
I also see that you have the angle plate for your mill, Nice. I bet that helped to get the set screw done on the flywheel.
Also did you use HSS or a carbide on taper, as it looked like you were using the carbide on the rest of it, it looks clean and bright finish
 

tomw

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#14
Ken,

I sent you message with my phone number. Just send me text if you have a hankering to head to Austin.

I forgot about the holes for mounting the cylinder. Yes, you will need the extended column for those, or a very short bit. Someplace I saw someone use a three jaw lathe chuck to hold drill bits because it gave him more head room.

I used HSS in the compound, as it can only hold 1/4" bits. I used carbide for the rest of it.

Cheers,

Tom
 

kvt

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#15
I have a set of 1/4 inch carbides that I use that way I can switch back and forth as needed. I do not have a quick change toolpost setup yet. Still using the originals. Getting tools as I can. Thus mostly sticking with 1/4 inch all around.
 

tomw

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Doggone it, Tom. Why'd you have to go and show us this? I've already taken a look at the PMR web site. That looks like a great project to take on.

Seriously, thanks for sharing. I'll be watching your progress. Might just have to join you. Your detailed tips will make it easier for any who give it a try.
Hawkeye,

Thanks for watching the progress. The PMR model castings really seems to be good. They are also interesting engine designs. And, for me, they have several models that can be done on small machines.

Cheers,

Tom
 

Hawkeye

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#17
Do they happen to make a kit for it to make a reversing linkage? That could be a fun after-project.
 

kvt

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Hawkeye, I have not seen one on their site but have seen general ones on other sites that is like the kit that one guy used for a governor it was from some place else, But that would prob be fun trying to make that kit work with this kit, say governor, reverse, and a boiler pump, all hooked up with drip oilers, and a nice boiler and water tank. Then you could put on show, Oh, though of another item that auto cylinder oiler, That way we do not have to worry about killing the cylinder. I may have to start looking for additions to mine, but first I have to finish the basic engine. but yo u gave me some good ideas for mine. thanks
 

tomw

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Hawkeye, as far as I know, no. They do make kits for boilers, which might be my next project. I always like to build things that might go boom.

The next casting I thought I would tackle was the connecting rods. So, instead I did the heads.
The first step with the heads was to remove the remains of the sprue. I did this with my 1" belt sander followed by a bit of filing. As an aside, one of my favorite tools has become by Grizzly combo 4" disc, 1" belt sander. It is a Chinese thing, sold under a bunch of different brands. It is cheaply made and cheaply sold. But man, is it handy!

Filing to remove the sprue.jpg

Filing the head flattish after removing the sprue using the 1" belt sander.

I then decided to proceed with the inboard heads. First I chucked it up using the "stuffing box", or gland seal, or whatever you want to call it, protrusion as the hold point. I did my best to get the flat face to run true-ish. Holding the head this way was a little precarious, what with the casting draft on the stuffing box. Thus, it was again light cuts to make a clean flat surface.

1 Inoard head in chuck.jpg

An inboard head in the 3 jaw chuck.

2 inboard head flattened.jpg

Taking very light cuts to get a clean, flat surface on the inside of the inboard head.

The head was then taken out and re-chucked, with the newly flattened surface resting on parallels. This is really easy to do in a small lathe like the Sherline because it is so easy to remove the chuck and put it on a bench. I then put the chuck back on the lathe and proceeded to fling the parallels at high speed across the shop. Just kidding, but that is what will happen if you don't remove the parallels before you start the lathe!

3.2_ reverse mounting inboard head .jpg

Using the newly created flat side, the head was mounted in a 3 jaw chuck using parallels to indicate in the part.

4 head ready for lathe.jpg

The head in the chuck, without the parallels. Did I mention that it is important to remove the parallels before spinning up the chuck?


Once the head was securely in place, I proceeded with machining the outer face and stuffing box, including drilling through the stuffing box 1/8" (for the piston rod), then drilling and tapping for 1/4-28 threads 1/4" deep of the gland nut. I used both a plug and bottoming tap to get the threads as deep as possible.

Out side of inboard head machined to size.jpg

The stuffing box and outer face of the inboard head machined to size

Tapping the stuffing box.jpg

Tapping the stuffing box for the gland nut. Here I am using a 1/4" bottoming tap.


The head was again reversed in the chuck. To ensure that the head was running true, I used a bump indicating trick. I do not have a little ball bearing tool to do this, but I have found that the ass end of a brazed carbide tool, with a little lube on it, works great for this. I double checked the alignment with a DTI, declaring success if the face runout was less than or equal to a thou. This is an important step, as that face really needs to be perpendicular to the piston rod hole. Otherwise the rod could bind.

Bump aligning inboard head.jpg

"Bump" indicating the inner face of the outboard head to make sure it is running perpendicular to the lathe ways.

The face and edge of the head were then machined. The face was machined to the final thickness of the mating surface plus the height of the cylinder pilot. The cylinder pilot was then machined by additional facing cuts to the diameter of said pilot.

Inboard head step.jpg

Facing the inboard heads inner surface to create the cylinder pilot. The pilot is only 1/32" high, and the diameter is critical, so this is fiddly work.

The entire process was then repeated with the second inboard head.

The outboard heads don't have a nice little stuffing box boss to hold onto. To remedy this situation I CA glued (super glue) a bit of 3/8" diameter brass to the outside of the head. It turns out a 3/8" dia piece of round stock just fits into the depression on the outside of the outboard heads.

Super glue for the boss.jpg

Using CA glue to attach a bit of 3/8" brass rod to the outboard head. I removed the boss later by using a butane torch to heat it to about 400°F.

The head was then mounted in the 3 jaw chuck using parallels, with my glued on boss sticking out to be machined. The parallels were removed and the boss was then turned until it ran true. The head was then flipped and held by the boss in the 3 jaw chuck for final machining. like the inboard head, the pilot was machined in once the head was taken to a thickness of the flange plus the pilot.

Turning the boss.jpg

Turning the brass rod "boss" to run normal to the inner face of the casting.

Machining outboard head.jpg

Turning and facing the outboard head castings edge and inner surface.

Machining outboard head pilot.jpg

The cylinder pilot successfully machined on an outboard head.

Once the lathe work was done, I removed the chuck from the lathe, with the head still in it, and mounted it to my mill. I then used a coaxial indicator to align the center of the head and spindle. The four mounting hole locations are on a 3/4" bolt circle, and were easy to locate using the DRO. These holes were center drilled and then clearance drilled 9/64" for the 5-40 head screws.

Center drilling outboard head.jpg

Center drilling the head bolt clearance holes.

twist drilling outboard head.jpg

Drilling the clearance holes 9/64".


After doing the second outboard head, I now had 4 heads. I hear this is better.

The heads.jpg

Can anybody spot the step I just might have forgotten?

Until next time:
Progress with inboard heads.jpg

My blogging buddies:
IMG_1159.jpg
 
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tomw

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#20
OK, so about those connecting rods. They are little bronze castings. They don't appear to have a straight surface on them, the thickness from the big end to the small changes, and there is much that is round about them. But, Dean of Idaho managed to machine them is a few simple steps. How hard can it be?

First off, I should admit that these connecting rods are the same as on the PMR #3 engine, which I previously "built." Second, I ended up making a custom, "light weight" rod out of aluminum bar stock when I completely screwed up the casting for that engine. By completely screwed up, I mean made a hash of, destroyed, made useless, or other synonym for doing what I should not have done.

But this time, it was going to be different. I had Dean's build!

Nope, I hosed both rods, at the same time, trying to be efficient. Just so the reader knows, super glue (cyanoacrylate glue or CA) is great, but it is not a wonder drug. Unless inhaled. Then it is wonderful at killing you.

I have ordered four new connecting rod castings from PMR. Maybe I will be able to update this log with how you actually might machine these little bastards. And, if any of you all (or y'all) have some tips, please let me and readers know what they might be.

So, I ended up making both rods from brass bar stock. Because this is not part of the kit, I am going to largely gloss over the details and show some nice pictures.

1_Casting for connecting tod.jpg

The raw casting

2_Connecting rod trickery.jpg

The raw casting adhered to a bit of aluminum. The shim is to get the things level with the mill table. This failed.

3_Starting over.jpg

A bit of brass bar stock being milled to square. It is slightly wider than two connecting rods worth of material.


4_cutting the blanks.jpg

The two "blanks" for the connecting rods being split from the single squared chunk of bar stock.

5_the blanks.jpg
g
The two roughed blanks for the connecting rods.

6_center drilling the big end.jpg

I stacked the connecting rod blanks in the vise edge on and milled them square to each other. I could then put them into the vise as you can see above and drill both blanks at the same time for the big and small end holes.

7_twist drilling the big end.jpg

The big end hole being drilled.

8_Reaming the big end.jpg

The big end hole being reamed. The small end hole was just drilled, not reamed, per the directions on the plan.

9 _blanks finished.jpg

The connecting rod blanks with some holes.

10 Jig for connecting rod.jpg

I created a jig to hold the connecting rod blanks on my rotary table. Both blanks were mounted to this jig at the same time (stacked).

11 Small end machining.jpg

Using the rotary table to make the small end.

12 Side plunge machining.jpg

Using the rotary table to make some plunge milling to rough in the angled side from the small to the big end. This was followed by by a continuous with the same end mill to final size.

13 Basic shape of connecting rods.jpg

The connecting rods so far. These are both 1/32" too large on the small end.

14 Machining final width.jpg

Milling the relief to get the small end (and most of the rod) to 1/8". Shims and parallels and cursing were used to make this possible.

15 Finished Connecting rods.jpg

The finished m******ing connecting rods are done. They are not as originally intended, and they are not pretty, but they should work. I hate these f***ing things.

Please pardon my French.

Cheers,

Tom

P.S. I will add to this log how I succeeded in machining these little freaking connecting rod s***s when and if I actually succeed in machining these little effing ************ers. Not that I'm bitter.
 

kvt

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#21
Ok, what part failed. The getting them level with the mill table or the holding them, Based on your comment about the super glue it may not have held the way you wanted or something. The home made ones look nice. I have been busy and have not even made it out to work on mine for over a week. The base is still sitting on the mill table waiting to be lined up and leveled again.
 

tomw

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#22
It was a combination of factors that led to the failure. Mostly it was about finding a good way to hold them solidly and on level. My failed solution was to use an aluminum plate that I glued the big ends to, and then supported the small ends on shims.

Thanks fro reading.

Tom
 

Hawkeye

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#23
I ordered my engine kit this evening. I can see that I'll be reading your account several times when I get working on it.
 

kvt

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#24
Tom,
here is what I was thinking on them, Clamp it in the Sherline vice, by the small end or as much as possible, and shim it to put it as much straight as it would go, Then use an endmill on the big end to cut the sides on it, then remove and clamp by the newly done big end now do the small end. If we squared the big end off properly we should now be able to have both ends set, and can hold by one end and drill the other, then do the switch again. Yea it is a bit of a pain, but I think it should work. these would almost have been better as blocks of stuff to cut and shape rather than castings from what I see and happened to you. If I get a chance to try it I will let you know.
 

T Bredehoft

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#25
At one time in my varied career, I was required to Blanchard grind the ends of some connecting rods. (approx 18 in long.) The big end was thicker than the small end and they were symmetric. We had jigs made for each of the four differing grinds. The first and second grinds were of the big end, the third and fourth for the small ends. We did four rods at a time, mounting them on each fixture, and in the case of the first of the set, leveling them crosswise in the fixture with a separate piece of fixture. It was a complicated process and one no one wanted to do. The very first grind taking 20 minutes to half an hour to set up and 5 minutes or less to grind. Two rods per engine. This particular engine had as a third piston on the crank, a double ended compressor piston, for natural gas. The engine ran on Nat Gas and compressed it also, to send it on its way in a pipeline. The power pistons were about 6" dia., 3 1/2" stroke, producing with a turbine, 75 hp.
 

kvt

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#26
I think I have seen some of those around, From the Texas panhandle they had both gas and oil pump stations all over the place. I always though it was funny they use the Natural gas to run and pump it as well, what if something went wrong, but never saw one fail and cause much of a problem (fire ball type). I always thought a sealed electric motor might be safer.
 

tomw

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#27
Hawkeye,

I hope you find it enjoyable. Let me know if I help with clarifying anything.


Tom,
here is what I was thinking on them, Clamp it in the Sherline vice, by the small end or as much as possible, and shim it to put it as much straight as it would go, Then use an endmill on the big end to cut the sides on it, then remove and clamp by the newly done big end now do the small end. If we squared the big end off properly we should now be able to have both ends set, and can hold by one end and drill the other, then do the switch again. Yea it is a bit of a pain, but I think it should work. these would almost have been better as blocks of stuff to cut and shape rather than castings from what I see and happened to you. If I get a chance to try it I will let you know.
Ken,

Yeah, I thought of something similar after I had screwed up the rods I have, if I understand what you are saying. The only problem would be the shimming and holding it well enough by just one end. They are pretty flexible little pieces.

The other thing I was thinking was putting them, one at a time, flat and by the big end, in the vice. Drill the big end hole and then use that to mount it to a fixture with some sort of fitting you could indicate from. You would still need to shim under small end to make it level, and probably shim under the thin section of the crank and clamp there to prevent the wobblies. But once clamped, you could mill and drill the small end, flip it and re-shim, and then mill the other side of the small end. It would be a lot of monkey business for two small pieces, and you would still need to thin the big end somehow.

Let me know how it progresses. I'm going to keep pondering.

Cheers,

Tom
 

tomw

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#28
The next things I did were the crank throws and crank bearings.

The crank throws are bronze castings. The first step was to use the belt sander and some draw filing to remove the sprue and smooth the surface a bit. I then mounted the casting in my three jaw chuck. The central boss was then turned and faced. According to the drawings, the height of the center boss is not critical, but the height (or thickness) of the crank throw as a whole is very critical (the drawing has a .xxx dimensional callout, so +/- .005). From crank throw is drawn with what looks like half of the thickness being taken up by the boss, so I faced the boss to a height of 3/16". The diameter of the boss is also not critical, so it was taken down until it was nice looking. This is probably an optional step, but it makes for a much better surface for the chuck to grab in the next step.

1 Crank throw casting.jpg

The crankshaft throw rough casting.

3 Position throw in three jaw chuck.jpg

After removing the sprue and a little draw filing, I mounted the throw in a three-jaw chuck.


4 Turn and face center boss.jpg

I machined the side and faced the end of the boss. The height of the boss was brought to 3/16". The parallels are somewhere under one of my toolboxes. Do as I say, not as I do.

The piece was then flipped and grabbed in the three jaw chuck by the newly machined boss. I did not want to mar the newly machined surface, so I cut a small strip of aluminum shim stock to wrap around the boss. The jaws then dig into the aluminum and not the nice shiny bronze.

5 Protective aluminum for boss.jpg

I fashioned a protective shield for the boss from some aluminum shim stock.

I then faced the surface, taking cuts until the piece was .375 thick. To get it to the right thickness I first did enough facing to make the surface smooth. I then removed it from the chuck, measured its thickness. I then rechucked it and took the rest of the cuts. I only removed it for the one measurement, as I wanted the surface to the absolutely perpendicular to the crankshaft mounting hole (next step). Unfortunately, I have no pictures of this process.

I then center drilled, drilled and reamed the hole for the crankshaft to 1/4".

6 Drilling the crank hole.jpg

Drilling the 15/64" hole for the crankshaft on a nicely faced crank throw. This was followed by reaming to 1/4".


The next step was to drill the hole to which the f*****g connecting rod is connected to the crank throw. The distance between this hole and center of the crankshaft needed to be accurately determined. For aesthetics and balance, this hole also need to be along the center line as defined by the center of gravity of the throw. I found the centerline of throw using a ruler, my opti-visor, and some swearing (yes, I like Oxford commas). As kind of illustrated below, I would pick a point some distance from the hole for the crankshaft and find the middle of the narrow bit on the throw. I did this for three points, and then used a straight edge and scribe to connect the dots. This line now identifies, reasonably accurately, the centerline of the throw's center of gravity.

Finding centerline.jpg

A rough illustration showing how I roughly determined the centerline of the crankshaft throw. The light gray bit is supposed to be a ruler (or scale if you prefer).

10 Center line of the crank throw is marked.jpg

The crank throw in a three jaw chuck mounted to my rotary table. Note the scribed line. Along this line, .375" from the center of the crank hole, will be drilled a #38 hole for attaching the connecting rod.

I then mounted and centered my rotary table, and then mounted the 3 jaw chuck with the crank throw still in its clutches. I moved the X axis .375. I installed and aligned wiggler, and used the rotary table to bring my scribed line under the center of the spindle. And like Robert's your Mother's Brother, I could now drill the #38 hole that will be the point of attachment for the g*****n connecting rod.

12 Usign the wiggler to find the center line.jpg

Using a wiggler to indicate the centerline under the center of the spindle, .375" distant from the center of the crank hole.

The grub screw hole to fasten the throw to the crank was then drilled. I did this by holding the throw vertically in the vise, and aligning it by eye so the grub screw hole would be on the opposite of the side of the boss that faces were the little s**t of a connecting rod attaches. I used the crankshaft itself to make sure the hole through the boss was perpendicular to the axis of the grub screw hole. Then I used an edge finder and some arithmetic to find the horizontal center of the boss and drilled the hole. All holes were then tapped with the appropriate tap and fluid.

14 Set up for drilling the grub screw hole.jpg

A shop still-life, showing how the grub screw hole was located and then drilled. I don't show a center drill, but I did use one.

15 Connecting rod mount and grub screw holes tapped.jpg

Tapping. That is a 5-40 tap.

The above steps were done for both crank throws.

I then made what the kit calls the crank bearings, but really they are the bearings for the connecting rods. Anyway, those are pretty basic. Read the captions on the photos below for more details.

17 crank bearings from 1-2" CRS.jpg

I used 1/2" 12L14 CRS for the bearings. The kit supplies a chunk of 5/8" CRS. It seemed silly to remove more metal than I had to, so I made the switch. If I had had 3/8" CRS, I would have used that.

18 Face and turn to 5-16".jpg

I faced and then turned the stock down to the 5/16" outside diameter. BTW, I love turning leadalloy.

19 Drill through.jpg

Drilling the central hole. I center drilled things to get it started, and then I drilled deep enough so I could get both bearings done at once.

20 Turn the pilot and cut off the bearing.jpg

The inner pilot diameter was then turned. To get the shoulder as small as possible I did this turning with a very sharply pointed HSS bit (not shown). Here are I am getting ready to cut off the first completed bearing.

21 Two tiny bearings.jpg

The crank bearings completed. Both bearings have been de-burred.


And this is how things look at this stage:
22 Progress to date.jpg

Until next time, Cheers,

Tom 9 Getting ready to mark location for connecting rod mount.jpg 11 Finding the crank throw center.jpg 16 Finished crank throws.jpg
 
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tomw

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#29
Next up are the eccentric hubs and eccentric straps.

The kit provides a length of 5/8" CRS, probably 12L14, from which to fashion the eccentric hubs. There is a concentric groove and a 1/4" hole for the crankshaft that is offset .100, for an eccentric throw of .200.

1 Eccentric hub plan.jpg

The eccentric plan, should I be able to stick to it.

The first step was to create two grooved parts of the correct length. I faced the provided stock, and then turned the first groove. I used my .031 wide carbide grooving tool, which allows for cutting on the side of the tool. I would plunge cut both ends of the groove as indicated on the plans and then turn between those points to about 10 thou less than the final depth of .075. Each sweep I would take about 15 thou. Then using my "wire gauge", 1" mic, and some arithmetic, I took the last few cuts to the called for depth. The scare quotes are because I used a drill bit as my gauge. Or is it gage? What is the difference?

2) grooving hub.jpg

Cutting the first part of the groove with a carbide groovy tool. The groove is .100 from the end of the part, and will be .100 long by .075.

I then cutoff this first part and repeated the above steps for the second, hopefully identical part.

3 Cutting hub off.jpg

Yup, cutting off the part.

A now grooved part was then mounted in my 4 jaw chuck. I need to be able to offset the part from the spindle center by .100 in just one plane. To make this easy, I had previously fashioned some thin v-blocks. I use these v-blocks and some small parallels to mount the piece in the chuck. The piece was then centered in the chuck. I prefer the method outlined by David Lemereis in this video for chuck centering. This has been posted on this site before, but it is worth mentioning again, in my honest opinion. What sort of jerk gives his dishonest opinion? Psychopaths, I suppose.

4 Set up for drilling and turning off center.jpg

Mounting the part in my 4-jaw chuck. It is only roughly centered here. Once centered, it will be offset along one axis .100.

With the jaws snug, but not tight, I then offset one axis .100. The really nice thing about the v-blocks and parallels is that you don't have to worry about getting the other axis out of center, since those jaws remain snug on the fixture the entire time. You also don't need to worry about getting scratch marks on the piece as it moves past the jaws.

The hole for the crankshaft was then drilled and reamed to 1/4".

5 Reaming the drilled hole.jpg

Reaming a hole! Holy moly, look at that! Wow!

Then I machined the piece to create the lobe-like bit, aka counter weight. On an engine this small I imagine this part is optional, but it does make the part look better, and it is called for on the plans.

6 turning relief.jpg

Roughing out the counter-weight lobe on the eccentric hub. The visible steps are eliminated during the finishing cuts.

The trick here is paying attention. I did not want end up going to far, so I turned the lobe to about 10 thou less than the correct diameter and about 10 thou less than the correct height (depth). I then went back and took light facing cuts towards to lobe and then would back the bit out along the Z axis. In this way, I would increase the height and decrease the diameter of the lobe and leave behind a nice smooth surface.

Wow, was that clear as mud or what! Maybe the sketch below will help understand these last few cuts.

cutter path.jpg

Imagine this is a sketch of the eccentric hub. The grey area is going to be removed as the cutter follows the arrow. Note that the cutter is at an angle to give clearance for both facing and turning in one somewhat smooth operation.

This process was repeated for the other eccentric hub. I used the trick of only loosening two adjacent jaws to swap in the second piece, thus ensuring my centered offset would remain undisturbed.

Both pieces were then taken to the mill and their grub screw holes drilled. I used the same process as on the crankshaft throws. These holes were then tapped for the 5-40 set screws.

8 Drilling for grub screw.jpg

Center drilling for the grub screw hole.

9 Finished eccentrics.jpg

Finished eccentric hubs.

The material provided for the eccentric strap, or simply eccentric on the plans, consists of a short piece of brass tubing. The tubing O.D. is fine, but the I.D. is too small to fit over the eccentric hub. This I enlarged by boring until the eccentric hub just slid into the bore. It is a sliding fit, so there needs to be about a thou of play. Otherwise it will bind and/or gall when running.

10 Eccentric straps.jpg

The provided stock for the eccentric straps are these two bits of brass tubing.

11 Boring ID of eccentric strap to size.jpg

Boring out the tubing so the eccentric hub will slide within it.

12 Trial fitting eccentric hub in enccentric strap.jpg

Checking the sliding fit of the eccentric hub in the eccentric strap. Slides like a weasel chasing a rabbit down a hole.

I then faced the piece to the correct width (length?).

The plans call for a 45° x 1/32" chamfer. I put this on using a straight, brazed carbide bit set at 45°. To chamfer the other side, I flipped the piece in the chuck and bump aligned it to get it running true before doing the cut.

13 Champering strap.jpg

A chamfering I will go.

Each strap was then taken to the mill, where I milled a small flat on the O.D. and drilled and tapped the hole for the valve connecting rod.

14 Spot facing strap w 3-32 endmill.jpg

Putting a flat spot on the outside of the eccentric strap. The lock nut for the valve rod goes against this surface.

15 Finished straps.jpg

Finished eccentric straps. Or eccentrics, as the plans call them. This strikes me as an odd name for these parts, as they are, in fact, very symmetric.

That is it for today. Until next time.

Cheers,

Tom
 
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T Bredehoft

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#30
Thanks for the excellent descriptions of your work. I made a small (4" tall) two cyl steam engine many years ago, considerably different from yours. Only had a one sheet plan. I did a lot of engineering to get it done.
Steam Engine (2).jpg

The cyl block was hard brass, the base was cast iron, the rest was mostly drill rod.
 
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