A two cylinder mill engine under construction

[Philjoe5]

I’ve built several versions of a single cylinder oscillating rotary valve steam engine to get my machining skills sharpened. Now I’m building a two cylinder version of this engine. I’m working off the set of plans for the one cylinder engine, making modifications as needed.

Here’s a photo of one of the singles I’ve built:

Through the magic of photo editing software I’ve made a picture of the 2 cylinder engine I’m building:

Basically I’m going to take the cylinder – con rod – eccentric assemblies, duplicate them, and put them on the other side of the flywheel. The crank pins on the crankshaft will be offset by 90 degrees so the engine will self start.

Now for my first progress report. All barstock engines start with a good lump of metal, in this case some 1144 free machining steel:

My trusty bandsaw is making 2 cylinder blocks here:

A little milling machine work and here are the blank cylinder blocks ready for some machining:

There are 2 passageways that are drilled at 30 degree angles from the cylinder bore to the valve port. I start these with an end mill to make a flat, then drill the passageway. This operation takes a light touch to keep the end mill or drill bit from wandering.

Several drilled holes and 56 tapped holes later, here are two cylinder blocks finished!

They are nearly identical. Using some cylinders from my “parts” box, I’ve estimated there’s about a 0.003” difference in bores between the 2 cylinders. That’s OK because the pistons will be machined to fit their individual bores.

I’ll try to post regularly to keep you all informed of my progress. At some point I’ll need some advice so if you can help jump in.

Cheers,
Phil

 

[BobWarfield]

This will be a fun one to follow. Off to a great start so far!

Thanks,

BW

 

[ChooChooMike]

Yup, looking forward to seeing your build pix !!

 

[Maryak]

Philjoe,

Great work, keep it up :bow:

Ain't castings expensive, Bar stock is the way to go ;D

Regards,

Bob

 

[Philjoe5]

This week I made the cylinder heads and started the crosshead guides. I’ll post progress on the guides when they’re finished. If I'm posting progress in annoyingly small increments, let me know and I'll stretch 'em out.

In this pic I’m using an edge finder to locate the center of the round workpiece, the cylinder head.

Determine the radius, R of your workpiece and r, the radius of the nub of the edge finder. Then find the edge of the workpiece at about 3 o’clock. Move the table of the mill a distance of R + r to the right. Then locate the edge of the workpiece at about 12 o’clock by moving the table toward you. Now move the table away from you a distance of R + r. Once again find the edge at 3 o” clock and so forth. The handwheel settings quickly converge to a constant and you’ve located the center of the workpiece. I forgot where I found this method but it works like a charm. If anyone reading this knows the correct name of this method please chime in.

I’m drilling the mounting holes here. Once I find the center, a little trig gets me to each location for the next hole. A rotary table would also work here but I get consistently better results using this method.

This picture shows one cylinder head mounted and the inside view of the other one.

Nothing fancy with making these, although I have found several ways to screw them up in the past. So what you’re seeing here is the result of my informal education.

Cheers,
Phil

 

[Circlip]

Without trying to detract from your machining and setting skills Phil, newbies might find it easier to accurately drill a turned washer as a jig, to locate on the cap and trunk guide spigots and spot through on to them? If you've drilled it correctly, it gives you three less chances of making a mistake.
Regards Ian.

 

[chipstractor]

Phil,
Neat project. Keep us posted.

 

[Philjoe5]

Good point Ian. In fact the designer of the original plans for this engine recommends that approach and it is common to see it. I use the trig approach simply because I remember sitting through the class when I was 16 years old and saying to myself "What the heck am I ever going to use this stuff for"? So with kindest regards to my former trig teacher, Mr Werner, I'd like to say, "Thanks for teaching me a very useful mathematical tool".

Cheers,
Phil

 

[mklotz]

Determine the radius, R of your workpiece and r, the radius of the nub of the edge finder. Then find the edge of the workpiece at about 3 o’clock. Move the table of the mill a distance of R + r to the right. Then locate the edge of the workpiece at about 12 o’clock by moving the table toward you. Now move the table away from you a distance of R + r. Once again find the edge at 3 o” clock and so forth. The handwheel settings quickly converge to a constant and you’ve located the center of the workpiece. I forgot where I found this method but it works like a charm. If anyone reading this knows the correct name of this method please chime in.

It's called the "Osborne Maneuver".

 

[Philjoe5]

I’m making the crosshead guides out of some aluminum bronze. I found a good supply of this material in 1 5/8” diameter a year ago. It machines nicely and adds a nice contrast to the steel components of the engine.

Here I’m turning a section for one of the crosshead guides. I’m using the dial indicator to tell me when to stop feeding to get the proper length.

Now I’ve turned both crosshead guides and drilled/bored them to specs. I mounted them on the cylinder blocks to check for fit. Next I need to make access ports in the sides so I can oil the piston rod and adjust the packing gland nut if required.

In the past I’ve milled slots or drilled holes and I like the appearance of the drilled holes so I’ll go with that approach here. I made a clamping device using a bar of aluminum to hold the workpiece down and the vise jaws are “lightly” clamped on the guide to prevent crushing the walls. Then the holes are drilled with centercutting end mills in steps up to ½”.

The bores of the guides are lapped to remove any burrs from the drilling operation and to ensure they weren’t distorted in the vise (which would be easy to do with a wall thickness of 0.070”). The crosshead guides were completed and are shown here along with the aluminum rod I used for a lap:

I made the valve port covers by taking a piece of brass turning it to the required diameter and drilling the 4 hole bolt pattern, before turning the end down that fits in the port. Then it’s a simple matter of turning down the stock to form the nub, slicing off the workpiece by parting off or using the bandsaw, then facing the flange side to its thickness of 0.125”

The mounted valve ports are shown here. I also completed the cylinder heads, rod end for this side of the engine. These cylinder heads are also made of aluminum bronze. This photo shows both sides of the cylinder blocks with the two types of cylinder heads. It may not be clear, but the cylinder head on the rod end is tapped for ½-20 NF threads. Packing gland nuts will be made to fit.

Cheers,
Phil

 

[Maryak]

Phil,

Your engine is coming along very nicely :bow:

Bronze on steel does give a very pleasing visual mix.

With the drilled holes for access to the gland nut etc. Do you make a special spanner to adjust the packing ???

Best Regards
Bob

 

[Philjoe5]

The packing gland "nut" is a turned down rod, threaded on one end to fit into the cylinder head. It has 6 holes (0.100" diameter) drilled radially at 60 degree intervals. To tighten the packing gland nut put a 0.1" diameter rod into one of the holes and tighten the nut. Here’s a picture of a completed packing gland nut along with a fixture I use for the drilling operation.

Cheers,
Phil

 

[wareagle]

Phil, I have been watching this one unfold, and I have to say your are doing a good job! The engine is looking great. Many thanks for taking us along the journey!

 

[Maryak]

Phil,

Now why didn't I think of that - especially seeing as I recently made such a thing for a 1927 Chevy water pump gland :-[

Best Regards
Bob

 

[Philjoe5]

I’ve completed both piston – piston rod – crosshead assemblies. Not without a few misadventures. I turned the first crosshead down a few thousandths too much, and that was for the crosshead guide with the smaller bore. Then while milling flats on the replacement crosshead, the workpiece shifted in the vise and buggered up the face, so that was scrap. Finally, getting back on the horse for the third and fourth times, I managed to finished them. The precision of these assemblies will directly influence the smoothness of the movement of the engine so I’m as fussy as I can be.

The sequence for making these assemblies follows. First, the piston rods are cut roughly to size on the bandsaw, faced off on both ends to size. Then each end is turned down to 0.186” for a length of about 0.4” for 10-32 threads. This is 2% less than the major diameter for this thread and has given me good results for this size. A tailstock dieholder is used to cut threads. As a result of some input from this board (Thanks Rick, Greenie) I reduced the diameter of the piston rod to the shoulder by about 0.010” past the last thread. This ensures the shoulder of the piston rod butts up against the crosshead and gives minimum runout of this assembly. When I chuck up the piston rod I get TIR < 0.003” on the piston end and < 0.006” on the crosshead end.

The bronze pistons have 3 evenly spaced oil grooves that are 0.003” deep that are made with a 60 degree threading tool. I make each piston to fit one of the cylinder blocks since they differ in size by about 0.003”. I had to make an aluminum lap for one of the cylinder blocks to get the piston to go all the way through the bore, but once lapped the piston moves smoothly through the bore. Completed assemblies shown here:

Using an old con rod I had I connected up the crosshead end of the engine with the piston attached. For both cylinder block assemblies movement is quite smooth. When I first built this engine I wondered about the function of the crosshead. If I take the piston rod assembly and run the piston back and forth through the bore I seem to get a lot of “stuttering” in the movement. Once the crosshead and guide are in place though, movement is slick. The function of the crosshead is to minimize tilting of the piston in the cylinder bore and it sure works.

Finally, I made the packing gland nuts. I have been leaving the packing empty on my previously built engines with no apparent ill effects. I’ve only run on compressed air and perhaps that is why I’ve gotten away with it. Here is a photo of the packing gland nut attached to one of the cylinder heads.

This subassembly of the engine takes all the patience I can muster, but it pays good dividends in the end. Whenever I finish work of this nature I tend to go on to a part that requires more bulk cutting like carving a flywheel or connecting rod from a chunk of steel. One of those is next.


Cheers,
Phil

 

[Brass_Machine]

Looking good Phil!

When are you, me and Tin getting together for coffee?

Eric

 

[Philjoe5]

Eric,
For sure at Cabin Fever. Anything else coming up before that?

Cheers,
Phil

 

[Philjoe5]

This posting describes making the connecting rods. The con rods in the original plans have the big and little ends silver soldered to the rod. An admitted hack at silver soldering, I’ve made the con rods one piece. This means I’ll have a bit more milling to do. Time spent doing the extra milling could have been applied to a few lessons in silver soldering I suppose but I didn’t want to spend the $ for a proper torch now. Here’s where I’m starting and also where I hope to end. The completed con rod is from a previous project.

A few hours later with most of the milling done I have two blank con rods.

Now I have some drilling and boring to do. Being a believer in fixtures BUT being frugal I try to make as few as possible. So I’ve drilled and reamed the small end and drilled the big end here to fit the fixtues I have. Here I’m rounding off the small end on one of the con rods using the rotary table.

After taking the sharp edges off of the big ends on the rotary table it’s back to milling the angles. I’m setting the milling angle in this picture. That angle block is removed before milling.

Finally they’re drilled and bored to full size of 0.700” ready for a bronze bushing.

I use two set screws to hold the bushing in place. Are they necessary? I’m not sure but they’re easier to put in now rather than later. The picture shows two cap screws inserted to emphasize the threaded holes.

Finally the bushings are made from a piece of ¾” bearing bronze turned to size, drilled, reamed and pressed in position on the con rods. I’m parting one off here:

The con rods are finished.

I’m nearly finished with the stuff that comes right off of the plans. I’ve done some calculations for the baseplate and I think I have that figured out. In its final form it will be a plate of 3/8” aluminum but I’m going to make a temporary one out of wood to check my math. I have lots of cheap wood but no cheap metal. More later. At this point if I make the bearing blocks and crankshaft I can finish out the design for the base.

The crankshaft will have the webs pinned in place so I can remove the flywheel or eccentrics for maintenance. I’ve made up a design for the webs based upon some other engines of this type I’ve seen. More details to follow, but right now I’m planning to pin the webs to the crankshaft with 6-32 set screws. A good idea?

I think I’ll tackle the bearing blocks next.

Cheers,
Phil

 

[Maryak]

Phil,

Looking good, I agree with you solid is better than silver soldered, or flanged ends and split bushes through bolted. :bow:

Best Regards
Bob

 

[Philjoe5]

Time for my weekly progress report. Bearing blocks are the topic of discussion this week.

I’ve machined the bearing blocks using a two piece design. This is a modification from the plans that call for a split brass bearing attached to a steel base. The sequence of machining is: mill the steel base to dimensions, mill the brass bearing cap to dimensions, drill and tap the base, drill clearance holes in the brass cap and assemble the cap and base. Next, drill and ream the brass cap. Then mill excess off the brass cap and round it off. Pictures of each step will help you see what I’m doing. There’s nothing fancy going on here but careful work ensures the crankshaft fits and rotates freely when this whole assembly is mounted on the baseplate.

A short digression here. I got into this hobby a few years ago and my immediate goal was to build some working engines, display them at some shows and meet some other folks. Initially I built some engines with fairly simple machining techniques. An example of one of my first steam engines is shown here. Note the rectangular bearing blocks. I hadn’t really figured out how to round the tops according to the plans.

Now, a year later, I’ve picked up a few tricks and have figured out how to do this. So while I’m working on this engine, I’m going to jazz up the bearing blocks on my older engine using the same fixture and machine setups as my present build.

Starting out I milled two pieces of steel and brass to dimensions. Then I tapped the steel bases on both sides. Topside for mounting the brass bearing caps, bottomside to mount the bearing blocks to the baseplate. Then I assembled caps to bases.

Next, comes the drilling operation for the crankshaft. I know there has been dialogue on this board about proper drill bit geometry for drilling brass but I don’t have the means to have separate sets of drills for steel and brass. So, necessity being the mother of etc., I found I can drill a pilot hole on the mill/drill in brass using the quill feed. Then when drilling larger holes I switch to the fine feed (by handwheel). The ability of the brass to grab the drill bit is countered by the mass of the mill/drill head and the whole operation proceeds smoothly.

After reaming the ½” crankshaft hole,

the units are assembled and a ½” piece of drill rod is set through the bearing caps to check for alignment. In my former unskilled life, I would have stopped here at these perfectly functional but unattractive bearing blocks.

Next, the caps are removed and prepared for rounding the tops. First I drill ¼” holes that define the start and stop positions for the end mill used for rounding.

Holes are drilled and excess material is milled away on the mill/drill.

Then the caps are mounted on a fixture. The fixture is mounted in the chuck on the rotary table and using a ¼” roughing end mill I find the positions of the start and stop holes I had drilled previously. I note the positions and keep them handy. While milling I’m careful not to exceed either limit positions.

Here are all four brass caps milled:

The bearing blocks assembled for the new engine shown here

The bearing blocks for the old engine, shown here, installed. Nicer than before, no? Even better, the reassembled engine runs.

The next part I’m working on is the crankshaft. I’m using a crank web design that’s fairly common. I cut the two arcs on this steel disk with a boring head. Although it’s an interrupted cut, it went smoothly enough. Shown here is a trial cut on a piece of steel I fished out of the “recycle” bin

That’s it for now. In a week I hope to show you a crankshaft.

Cheers,
Phil