Winner Pm Research Engine #7

[tomw]

Bob, nice car. For some reason your avatar looked like a truck! I apologize, and am ashamed... I like it that you kept the original lines. I really like the sweep of the top towards the rear and how it blends with the rear fenders. Very nice. I also see excellent door and hood alignment; a sign of a true craftsman.

 

[Sandia]

Thanks Tom. Your engine turned out really nice and the build log is fantastic. Might tempt me to order the castings, as I like that engine design. I need to finish the Redwing I started last winter. Really don't like a lot, probably 3 or 4 weeks if I will just get back on it. I stopped working on it during the heat of the summer, just too hot to stay motivated not to mention the castings were constantly rusting on me. I would like to build the other hit and miss engine they sale, but darn those castings are expensive. That and the mess the cast iron makes is the down side.

Bob

 

[tomw]

Next up are the steam ports. I started by drilling the valve ports that go from the valve to the angled piston cylinder ports. I placed my guide pin in the piston bore and then mounted the cylinder casting in the vise. I then found the center of the piston bore on the Y axis using a edge finder on the protruding guide pin. I then found the longitudinal center of the cylinder casting in the X using my edge finder. The table was now locked and the DRO set to 0,0.

Next was getting the cylinder casting vertical, such that the centers of the piston and valve cylinder bores were aligned with the spindle axis. I placed a piece of 1/4" drill rod as a guide pin in the valve bore to a depth of about 3/16". This will ensure that I don't drill into my guide pin. I then mounted a piece of the 3/8" drill rod in my end mill holder. With the spindle located 5/16" off on the Y axis 0, and the vise slightly loose, I could rotate the cylinder casting until the two bits of drill rod were just touching. To determine if they were just touching I used my multimeter set on Ohms* and looked for the point were resistance began to fall. I called this just touching (sorry, no picture of this). I then removed the 3/8" drill rod and brought my table back to 0 on the Y axis. According to my logic and arithmetic, this should have placed a line passing through the centers of the piston bore and valve bore parallel with the center of the spindle. I then tightened the vise and moved back to 0 (on the DRO) in the Y. I double checked my centering in the X, since the cylinder may have moved a tad in the vise.

Aligning the centers of the bores with the spindle axis. Note this is the second of two cylinders I did, so I did not need my piston bore pilot to the align the piston bore in the y-axis.​

I then center drilled and drilled the valve ports at the location and to the depth indicated on the plans. Even though my cylinders are over-bored by .01, there is plenty of room left to drill these ports according the drawings.

Center drilling and drilling the ports that go from the valve bore to the piston bore steam ports. Note the piston cylinder guide pin used in the initial alignment of the casting to the spindle Y axis. DO NOT drill all the way into the piston bore, or you will be doing pain-in-the ass brazing. Just saying**.​

Next up was drilling the ports that go from the piston bore to the just drilled valve port bores. These ports start at the very edge of the piston cylinder wall and go at a 20° angle to the valve ports. The first step was setting up the castings in the vise. To get the correct 20° angle I used a 20° angle block. To get the casting positioned in the correct vertical orientation I used the same trick I used when drilling the valve ports. Since I have not moved the vise, my set up was still centered on spindle in the Y axis.

Getting my bores aligned so they are centered under the spindle and the center of the bores are parallel to the X axis. Note the turned down end of my alignment pin. This was threaded 3/16"-40 MP and used to align the casting for drilling the piston cylinder outboard steam port.​

I then used a 5/32" end mill to create the 3/32" deep counterbore. To find the center of this counterbore I used my wiggler to find the piston cylinder edge, and then moved in a further 5/64" (1/2 of 5/32") and set my DRO X to 0 and locked the tables. I then plunge milled the counterbore. I wasn't completely sure which part of the counterbore was to be 3/32" deep. I decided, looking at the plans, that the trailing edge was to be that depth. The 3/32" depth I milled was very approximate, being measured with a bit of wire and compared to my pocket scale. But, it was shiny!

I then used a #0 center drill to start the piston cylinder port bore, and then finished the drilling with a 3/32" stubby twist drill. Since I knew this bore had to meet with the valve port bore, I held a bit a welding wire bottomed in the valve port and drilled down until I felt the bit grab the wire.

Unfortunately, I have very few photos of the above process. I was very excited that it was all working as planned (I know, craziness), so I forgot. I flogged myself in penance later. Admittedly it was a light flogging with my back scrubby brush, and it actually felt pretty good, but the thought was there.

The steam port on the inboard side of the piston cylinder is counter bored and then drilled 3/32" deep until the bore reaches the previously drilled cylinder steam port.​

I then flipped the cylinder over, end to end, and bored the other (outboard) cylinder steam port. The only change was in finding the vertical center of the cylinder casting. The exhaust hole is a 5/32 hole tapped for 3/16" straight pipe tap. Therefore, I took my 1/4" drill rod, turned down about 1/4" to the correct size for 3/16" thread, and threaded it with a die. I then screwed this into the exhaust hole. This then became my guide pin for alignment against my spindle mounted 3/8" drill rod.

The above process was then repeated for the other cylinder. As before, no photos.

The last holes I drilled were the intake ports. These are 5/32" holes (to be tapped 3/16" -40 MP) drilled into the center of the intake port boss' (or bosses?) and through to the valve cylinders. To find the center of the boss, I made a little guide jig for a transfer punch. The guide fit snuggly over the port boss, and with a tight sliding fit for the transfer punch. This allowed me to then quickly center punch the correct center area of that center. Center center center....Jack is all work and no play jackisallworkandnoplay...

Using a transfer punch and a guide to center punch the intake port boss.​

It was then a simple task of mounting the cylinders in the vise and drilling the intake ports through to the cylinder bores. I then tapped these holes for 3/16-40 MP.

Drilling the intake port with a 5/32" twist drill. I was careful to stop drilling when the drill just completely entered the valve cylinder.​

After all holes were drilled, I used my 1/4" reamer to debur the valve cylinders. To debur the piston cylinders I first made a flappy emory paper sander by CA gluing the edge of a small strip fine emory cloth to a piece of drill rod. This flappy sander was then mounted in my hand drill and briefly run in the cylinders.


And that concluded the work on the cylinders, for now.

​

Cheers,

Tom


* How did the yogi know I was resisting his teachings? I kept saying "Ohm".

** On my PMR #3 build I made this mistake. I ended up silver brazing the edge of the piston bore where I drilled through and re-boring the piston bore. I saved the casting, but what a learning experience.​

 

[tomw]

I just read over my post (which I had read over about ten times before posting) and noticed a few mistakes. I corrected (most?) of the grammatical errors in the post itself, but thought I should correct this particular mistake with a separate mea culpa:

To debur the piston cylinders I first made a flappy emory paper sander by CA gluing the edge of a small strip fine emory cloth to a piece of drill rod.

I did not use emory paper. I used 400 grit AoX paper. In looking through my notes, I realized my mistake. I will be taking another flogging tonight. Mmmm, flogging...*

Cheers,

Tom

*My definition of flogging may be at variance with yours.

 

[tomw]

The next things I tackled were the two pipe fittings, an elbow and a T. These need to be cleaned up, drilled, and tapped.

The first thing I did was make a little fixture to hold the pipe fittings. The fixture is based on this design.

A little fixture for some little pipe fitting castings. The background grid is 1/4". The 1/16" pins in the fixture are press fit into one half and are a tight slip fit in the other half.​

Before I could mount the fittings, I had to use a small swiss file to remove the casting flash from the edges. Otherwise the fixture would not close completely upon the fitting. Once that was done, I placed the fixture with fitting in my milling vise. I aligned it vertically with a small precision square. I used my edge finder to then locate the pipe fitting under the spindle.

The 90° elbow mounted in the vise using the fixture. Since I knew the dimensional placement of the holes in the fixture I used the edge finder to center this under the spindle. When I rotate it 90°, the Y-axis remains centered, I only needed to center the X for the other hole.​

I then used a 3/8" end mill to clean up the end of the fitting before center drilling and drilling the passage. The fixture was then rotated 90° and the process repeated. The tee required one additional 90° rotation to finish. I then tapped each fitting for 3/16 MP. Note that on each fitting one of the passages is to remain unthreaded. This is where you are to solder the cross tube connecting the two cylinders intake ports.

Drilling the first hole with the tap drill for 3/16-40.​

Drilling the last hole for the tee fitting. ​

The next step was to drill the clearance holes for mounting the inboard head and cylinders to the base. There are three holes are on a 3/4" diameter bolt circle for each cylinder, but they are not evenly distributed around the bolt circle. Instead, the two upper holes are each 45° off the vertical centerline of the piston bore, with the third bottom hole on the centerline of the piston bore. Thus I had to do a bit of math to find the coordinates needed to drill the holes. This was pretty easy once I realized I had an isosceles triangle.

The coordinates for the inboard cylinder head mounting holes to be drilled in the cylinder casting. The Y axis is vertical.​

To make this process as easy as possible, I decided to drill the holes in the head and the base at the same time. So, I remounted the base on my fixture from way back when I first started machining the base.

The base remounted on my base fixture which is mounted to a 90° angle plate which is mounted to the mill table. I used a DTI and the drive shaft to square the base to the table. The shaft has been removed in the photo.​

I then used my co-ax indicator to center the through-hole on the cylinder mount under the spindle and set the DRO to 0,0. I then CA glued the outboard head to the cylinder mount. After letting this sit for 10 minutes, I used my calculated coordinates to center drill and then drill the three clearance holes. This process was then repeated for the other head and motor mount. The cylinder heads were then removed from the base by heating with my little butane torch.

Center drilling the holes in the inboard head and cylinder mount. The inboard head is CA glued to the cylinder mount.​

Drilling the cylinder mounting clearance holes.​

Cylinder mounting holes are now drilled for the right cylinder.​

I then needed to create the threaded head mounting holes in the cylinder castings. I first mounted my rotary table to the mill and centered it under the spindle. I then bolted the cylinder casting to a small piece of aluminum stock using the piston cylinder guide pin. The guide pin had previously been drilled through the center to clear a 10-32 SHCS. This was then snuggly mounted (but not too tight) to the rotary table with some t-nuts and SHCS. I again used my co-ax indicator and some judicious tapping to center the piston bore guide under the spindle. I then tighten to the SHCS to lock the fixture in place.

I decided that horizontal center of the piston bore and valve bores would be aligned parallel to the Y-axis. I slightly loosened the piston bore guide pin, which allowed me to rotate the cylinder casting. I moved the mill table along the Y axis the known distance between the piston and valve bore centers and then used my wiggle with the ball end to center the valve bore under the spindle. I now had a known radial coordinate position to drill the mounting holes.

I moved the table back in the Y axis to the 3/4" bolt circle and used the rotary table and my center and twist drills to create the mounting holes. I repeated this process for the other end of the cylinder (using the radial dimensions for a 4 hole pattern). And then I repeated this entire process for the other cylinder. Once all the holes were drilled, I used my tapping jig to to tap all the holes for the 5-40 machine screws that are used to put it all together.

Drilling the inboard side of the cylinder for the mounting screws.​

A view of the inboard face of the left cylinder with the mounting holes tapped. All machining on this cylinder is now done.​

At this point, all of the castings were machined! What remained to be done were bar stock pieces and some piping.

Here is the engine to date:

Thanks tons for following along.

Cheers,

Tom

 

[kvt]

That is looking good. where did you get the oil cups for it. or did you make them. Thanks for sharing your build Mine got put on hold for a little while, now rearranging the shop so I can get back in it.

 

[tomw]

Ken,

I got them from PMR. I got the ones with 2-56 threads. http://www.pmmodelengines.com/shop/lubrication/oil-cups/

I hope you get back to your shop soon. I am also not in the shop, because I have torn my garage up to put in better wiring, insulation and a mini-split HVAC system. It will be worth it, but I am getting impatient!

Cheers,

Tom

 

[tomw]

I just read through all of my posts. Ugh.

For all of you who have suffered through this log, thank you! I'm still trying to get back my ability to write, and your patience is greatly appreciated!

If anything is unclear, or most things are unclear, and you want clear, please message me and I will do my best.

Cheers,

Tom

 

[Sandia]

Tom, I think you did a great job on the engine and your build pics and explanation is great in my opinion. Gives me the incentive to get back on my PM hit and miss engine.

Bob

 

[tomw]

Well, I guess I got a little frustrated with myself! The lesson here is don't drink and edit.

I am down to the last few bits. The next two bits are the pistons and valves.

The piston is made from 5/8" diameter brass round stock.

The bar stock and plan for the pistons​

This I turned down to .509 for about 3/4", allowing me to get two pistons. I checked the slip fit in the cylinders themselves as I was turning the piece, and .509 was a very nice fit. As a reminder, I over-bored the cylinders to .510.

I then cut the two grooves for the teflon piston rings, adjusting the final diameter of the grooves to account for the .010 oversize dimension.

After I turned the stock down to the correct diameter I cut the grooves for the piston rings. ​

I then drilled the 3/32" piston rod hole to 3/4" (this is a through hole in both pistons), followed by counterboring with a 5/16" 4 flute end mill. I think a two flute end mill would have been better. I ended up with quite a bit of grabbing going on.

Then the dame slapped me across the face like cobra striking a mongoose; not that I didn't deserve it. I knew then her brass was to be left alone...

Drilling 3/4" deep hole for the piston rod.​

Counterboring the piston using a 5/16" four flute end mill.​

The first piston was then parted off, and the next piston's ring grooves and counterbore were machined. After parting of the second piston, both were demurred and given a light polish to make the as smooth as a baby's hinder.

The pistons are completed.​

The valve is made from 3/8" brass round stock.

The bar stock and plan for the valves.​

Because of the length of the valves, I made them one at a time (i.e. no combined turning). The brass stock was turned to a nice slip fit in the cylinder valve bore, and then the grooves for the steam "ports" were created using my grooving tool. I took very light cuts as the piece was sticking out pretty far from the chuck. Unfortunately, it wasn't sticking out far enough to also use the tailstock center. At least not without a lot of monkey business. Once the grooves were done the valve was parted off to the correct length. This operation was then repeated for the other valve.

Turning the stock to the correct diameter. The part was checked for a slip fit in the valve cylinder bore.​

The grooves were cut using a 0.031 grooving tool with side cutting ability. I took very shallow cuts at 1000 rpm to reduce deflection of the part. ​

Parting off the valve.​

I then remounted each valve in the chuck and drilled out the steam exhaust channel. Each piece was then reversed in the chuck and the hole the valve linkage rides in was drilled.

Drilling the opening for the valve linkage.​

I then drilled the through holes over on the mill. The hole in the middle is for steam exhaust, the hole in the end is for pinning the valve linkage to the valve.

Drilling the through holes in the valve.​

The finished valves.​

Cheers,

Tom