"Pioneer" 2 stroke engine

[deverett]

This engine is not to be confused with Rudy Kohoupt's Pioneer. This Pioneer is a 2 stroke engine operating on the Systeme Loyale. Compared to normal 2 stroke engines, there is no crankcase and no valve gear - both inlet and exhaust valves operating at atmospheric pressure.
Whether this cycle was ever used in production engines is open to question.
Edgar Westbury wrote an article describing a model built on this system (included below) and Engineer's Emporium have obviously used his notes and sketches to produce their castings.

View attachment MODEL PETROL ENGINES PART XII by Edgar T.pdf

I decided to have a go at making this engine, so here goes on how it went. It's not a complete blow by blow account, more what I remembered to take pics of during the build:



The castings (except for the piston) are all iron. I opted to purchase a second flywheel just to make the engine look like the original and hopefully the extra mass will help with smoother running.

I started by machining the mounting pads on the top of the base. Shims were used to level the casting and a clean-up cut was taken over the raised surfaces; these would eventually be where the crankshaft and cylinder brackets would be fixed.


The casting was then turned over and the bottom cleaned up. The pads providing the level this time. Doing it this way round meant that minimal amounts were cut from the casting. Newspaper was used to contain most of the cast iron dust. The paper was curled back before machining to allow the scribing block to sit directly on the table to check the levelling.




Dave
The Emerald Isle

 

[idahoan]

Hi Dave

It's great to see a new engine project coming from your shop!

I will be pulling up a chair to follow along.

Dve

 

[deverett]

The crank bracket was next. I held this in the vice with card between jaws and casting. There was not enough room on the vice base for any lateral support, and although it does not look like the most secure holding, all went well for machining the bottom of the casting.


Once done, I was able to mount the casting to an angle plate to drill a pilot hole for the crank bearing. A long centre drill came in very handy for this job.


Once I had the pilot hole drilled, I enlarged the hole to take the counterbore pilot so that there was a seat for the crank bearings.


I have a set of counterbores where each cutter is mounted on an arbor with a separate pilot. Using one of these, I was able to counterbore the top face, the inside bottom face and using a special (home-made) arbor, the inside top face of the crank bracket.


The bracket was put in the vice on parallels and the mounting holes were drilled and spotfaced, this time with a one-piece counterbore.


Still one more face to counterbore, but this was done on the lathe later. The casting was mounted on the cross slide with a dummy crankshaft that was centred in the Grip-Tru chuck and tailstock centre through the previously drilled pilot holes. Needless to say it was hanging in the air, so it was packed up with shims and secured ready for boring.


This method ensured that the counterbored surfaces were going to be true to the bearing bores. At the time this was the only way I could think of doing it but in hindsight I should have done everything with the casting mounted on the cross slide in the first place. The pilot holes were enlarged with a bigger drill and then the boring head came into play to size the holes for the crank bearings.


The bronze bearings had previously been turned with just a reaming allowance left for final sizing.
Here we see the bearings in place. One bearing has no inner collar: this is where the timing bracket goes.


The crankshaft is just a plain piece of 1/2" steel with keyways each end. The embryo crankshaft was set up on the milling machine in Vee blocks and a slot cutter was used to cut the keyways.


Question: How do I post attachments so that the picture is seen in the text instead of readers having to click on the attachment link? I use the 'Manage Attachment' facility (paper clip icon) to load pictures.

Dave
The Emerald Isle

 

[Cogsy]

The pictures are showing up in-text just fine for me, no clicking required. I suspect your personal display settings are to blame. Have a look in your 'account' tab on the top of the forum for a setting along the lines of "display pictures".

 

[Jasonb]

Yep look OK to me too. You are off to a good start.

 

[deverett]

The pictures are showing up in-text just fine for me, no clicking required. I suspect your personal display settings are to blame. Have a look in your 'account' tab on the top of the forum for a setting along the lines of "display pictures".

Thanks Cogsy for pointing me in the right direction. All OK here now.

Dave
The Emerald Isle

 

[deverett]

Now I can see what I'm writing and picturing, reporting progress will be easier.

Flywheel turning has been described many times, so I won't go into any details. To get the correct crank throw on the flywheel, a simple jig was made up. A piece of flat bar had a hole drilled to accept a 1/2" bar that was a good fit in the crankshaft hole and a pilot hole was drilled at the crank throw distance. Fix the jig to the flywheel and sight the pilot hole to the centre of the crankpin boss, which had previously been marked with a radial line.
View attachment 84319
The hole was then tapped for the crankpin.
View attachment 84320

The cylinder bracket was held to an angle bracket with shims to get it level and spare bits of metal to prevent the clamps fouling anything. The bottom was cleaned up.
View attachment 84321
With the bottom done, it was a simple matter to clamp the casting to the lathe cross slide (suitably shimmed) to bore the hole for the cylinder neck.
View attachment 84322


Dave
The Emerald Isle

 

[Jasonb]

Don't know what you have done now Dave but I'm not seeing the pictures in your latest post. just a blue "attachment ####"

 

[Blogwitch]

Wonderful stuff Dave, well described and displayed.

I will be keeping a good eye on this build.

John

 

[deverett]

Don't know what happened with the pictures, so I'll redo the last post...

Flywheel turning has been described many times, so I won't go into any details. To get the correct crank throw on the flywheel, a simple jig was made up. A piece of flat bar had a hole drilled to accept a 1/2" bar that was a good fit in the crankshaft hole and a pilot hole was drilled at the crank throw distance. Fix the jig to the flywheel and sight the pilot hole to the centre of the crankpin boss, which had previously been marked with a radial line.

The hole was then tapped for the crankpin.


The cylinder bracket was held to an angle bracket with shims to get it level and spare bits of metal to prevent the clamps fouling anything. The bottom was cleaned up.

With the bottom done, it was a simple matter to clamp the casting to the lathe cross slide (suitably shimmed) to bore the hole for the cylinder neck.


Dave
The Emerald Isle

 

[deverett]

Hopefully I'm back on track now...

The air-cooled cylinder is a hefty lump. There is no easy way to hold it to get the inner end turned for fitting into the bracket. Nothing for it but to grab it tight in the 4 jaw chuck. Fortunately my M300 lathe was able to hold it securely while the mounting flange was turned. All appeared secure for the first op, so I carried on and bored it out at the same setting.

With the cylinder bored, next was to machine the other end face to receive the cylinder head. The cylinder was stood on end and secured by clamps in the gaps between the cooling fins. I've had a set of swan-neck lamps for several years and this is one of the few times that I have found them to be of any use (one of 2 can be seen; the other 2 clamps are standard Myford items - much more versatile).

The pad you see at 11 o'clock in the first picture is for the cylinder oiler. This was drilled and tapped. With the oiler screwed in place, it was used to orientate the cylinder in its bracket, ready for drilling/tapping the securing bolts.
Sliding the cylinder into the mounting bracket, orientating the cylinder correctly using the lubricator as a reference, the assembly was held vertical against a 2-4-6 block. The 4 securing screw holes could now be drilled and tapped. The locations of the holes, previously marked out, were picked up by a sticky pin.

The cylinder was held between two 2-4-6 blocks to machine the exhaust valve housing boss.

The exhaust hole was drilled/reamed and the valve chamber machined out with the boring head, then the seat was cut with a home-made seat cutter tool a la George Britnell.

Dave
The Emerald Isle

 

[Jasonb]

All OK now

 

[deverett]

On now to the cylinder head. This was held in the four jaw chuck; 3 jaws gripped naturally but the 4th jaw required a spacer in order to hold the casting firm.

The head was faced and bored for the combustion chamber and the inlet valve guide was drilled/reamed at the same setup.

The head was then held against a 2-4-6 block and levelled. A 3/4" piece of HSS was laid on the rough inlet boss and levelled with the aid of a scribing block and finger pressure on the centre of the HSS to stop it moving - all very high tech! After machining the face flat, it was faired into the head flange with a round nose mill.

The hole for the carb. was drilled/tapped at the same setting.


The head was clamped against the cylinder and the securing bolt holes were drilled and tapped.


The spark plug hole is at a 45 degree angle to the bolting plane of the head. Four stand-offs were made up and the head was bolted to a temporary mounting plate for drilling and tapping the hole.
The whole assembly was gripped in the vice and a pilot hole drilled from the combustion chamber out to the spark plug boss. The jack under the head resisted downward pressure from the drill.


The head was reversed on the stand-offs and the pilot hole lined up using the drill. The hole was then enlarged and tapped for the spark plug.


Dave
The Emerald Isle

 

[Brian Rupnow]

Nice work Dave, and very interesting set-ups.--Brian

 

[deverett]

The exhaust port casting was held in the four jaw chuck, faced and bored.

The casting was held against a 2-4-6 block and the top cleaned up. Using Jenny calipers, the centre of the top face was found. Using this method, usually three arcs are made but they rarely meet exactly, resulting in what we used to refer to as a cocked hat. Using best guess from the arcs, the centre was popped and then picked up with the sticky pin. The exhaust passage was drilled and tapped for the exhaust pipe.

The next picture shows the exhaust valve chamber - the pad on the cylinder and the valve housing. The valve seat tool and bushes are shown also. I decided to have the valve seat and valve at a 1 degree difference - 45 degree seat and 46 degree valve. The thinking, as mentioned by others is that it is easier to get a good seal with line contact which may end up at just a couple of thou after a twirl to seat the valve rather than trying to seal the valve with both parts at the same angle and greater contact area. This is not to say that others have done it with equal angles quite successfully.


The piston was supplied as an aluminium casting. There was plenty of length and girth on it so I just grabbed it in the 3 jaw Grip-Tru chuck; centred it as best I could and machined the outside to a nice slide fit in the cylinder and made 2 grooves for the piston rings.

Being a casting, hubs for the gudgeon pin were cast in place. The inside was bored out as far as the hubs. Then over to the milling machine where the recess for the gudgeon pin was milled out to the correct width to give room for the con. rod little end to swing. There have been various ways described to get the gudgeon pin hole perpendicular to the con. rod cavity. I happened to have a suitable piece of square steel that was a nice fit between the hubs. The embryo piston was held loosely in a vee block and using a square against the appropriate side of the steel, the piston was rotated until the square was lined up with the steel. The clamp was then tightened and the assembly put into the vice.


All that was left to do was return the piston to the lathe with the machined part held in the chuck and the un-needed end was parted off. I nearly said un-wanted, but that piece may come in handy one day.

The 3 rings were machined out of cast iron of unknown parentage. 3 because I wanted one spare, just in case... I made my rings a good fit in the cylinder bore and then split them using a jeweller's saw and filed the gap to be about 4 thou. I've tried other methods including nipping with pliers, hitting them with the end of a tool blank while they've been held in a vice but I've always ended up with more parts than I started with, which is not the object of the exercise.
I made up a clamp and spread the rings with a wedge to hold them apart and heated the assembly with the propane torch until they glowed a medium red for 5 minutes or so, then they were well covered in insulating glass fibre and pieces of silica firebrick and allowed to cool slowly.


Dave
The Emerald Isle

 

[deverett]

I've taken a couple of days off to recover from keyboard cramp, but now I'm back in the saddle...

I made the valves in 2 pieces, silver soldering the head to the stem.

This is the inlet valve held for soldering. The valve stem protrudes well through the head and a preformed ring of solder has been slipped on the extension. To prevent the solder going too far from where it is needed, before fluxing the joint I usually rub an ordinary lead pencil on the areas I want to remain clean. In this case it was easy to reach everywhere to clean up so I did not need to use the pencil. All that needs to be done now is to heat up the assembly until the solder flashes.

Here silver soldered, but yet to be cleaned up. Note how the solder has penetrated right through the joint. Could have used less solder. The solder wire I was using was 1/16" thick, and there was only one coil round the stem. It just shows how little solder is really required for these small fittings.


I now tackled a few small parts, most of which were simple turning and/or milling jobs so I photographed only a few of them. They were parts for the carb., ignition timing and exhaust valve spring system.

The carb. started off as a piece of 1" diameter brass bar. This required a square section in the middle with threaded portions on each end for the choke and mounting to cylinder head. The through hole required a tapered hole for the venturi. I happen to have 10 degree tapered end mill and this was the dog's bits for this job. A hand graver modified the entrance of the hole to give a trumpet shape. After turning and threading (external one end, internal on other end) it was mounted in the vice to mill the square portion.

The throttle barrel would eventually reside in a cross hole here.

The ignition timing lever required several operations. It started off as a piece of 1/4" brass plate.
After marking out, it was stuck to a super glue chuck to machine the boss and bore the central hole. A spring centre was sandwiched between the job and another centre held in the tailstock chuck. A clock gauge bore onto the stem near the point and the 4 jaw chuck was adjusted until there was no deviation on the gauge.

A clamping screw hole was drilled and tapped, with the screw clearance hole going through to half thickness.
The arm around the boss was nibbled out by step milling as closely to the boss as I dared.

It was then slit so that when fitted to the crankshaft bush the screw would secure it.

The final operation was to shape the rough edges and for this I used a couple of filing buttons. Another part done.

This is progress as it stands, along with the flywheels which are not shown here. Now I'm on the homeward stretch. Just the con. rod to make up, a few more small bits and then assemble everything.


I need the con rod fitted to piston and flywheel in order to line everything up to drill/tap for the hold down screws of the crankshaft and cylinder brackets. Relying on measurements would more than likely mean that there will be binding between the moving parts - especially with my measuring.

Dave
The Emerald Isle

 

[idahoan]

You are sure making quick work of this one Dave.
Very nice work, great pictures and explanations. I'm looking forward to seeing more progress.

Dave

 

[deverett]

Unfortunately, Dave, this has been very slow work. It is an account of a job that has (almost) been done.

All will be revealed soon!

Dave
The Emerald Isle

 

[Blogwitch]

Wonderful work Dave.

I really liked the way you made up the holding jig for the head, some people using castings don't realise that an hour spent doing something like that makes life a lot easier and quicker, and usually a lot more accurate as well.

Nice

John

 

[deverett]

I really liked the way you made up the holding jig for the head, some people using castings don't realise that an hour spent doing something like that makes life a lot easier and quicker, and usually a lot more accurate as well.

John

Actually, John, you must take the credit for that. I remember somewhere in the dim distant past that you used a similar type of jig which gave me the idea. Think it was it on the Scott vacuum engine.

Dave
The Emerald Isle