Mery Explosive Engine

[PaulR]

Machined one eccentric strap this afternoon. Following standard procedure I used an offcut of brass to mount the casting then centred it in a four jaw chuck.

I'd never have thought this method - neat! But the novice question: how did you centre it when there's none of the mounting piece sticking out of the chuck?

[Chipmaster]

Hello Paul,
the piece of brass bar wasn’t truly centred in the four jaw independent chuck, that was just a way to hold the eccentric strap casting. I adjusted the chuck jaws until the irregularly shaped casting itself looked to be central with the axis of the lathe, just by eye, hardly precise.
The faces of the brass bar were machined parallel at the outset so this method pretty well ensured the faces of the eccentric strap would be at right angles to the lathe axis.
I hope that answers your question.
Andy

[Chipmaster]

The two eccentrics were machined from a piece of cast iron bar.

IMG_1615 by Andy, on Flickr

Then held in a four jaw chuck to turn the offset of 0.094", the axle is 9/32" diameter.

IMG_1616 by Andy, on Flickr

Almost finished

IMG_1622 by Andy, on Flickr

IMG_1626 by Andy, on Flickr

The eccentrics will use grub screws to set their position for valve and ignition timing. I also need to drill and thread the straps to attach the eccentric rods also drill and thread them to attach oil cups.

Andy

[Chipmaster]

Each eccentric sheave fitted with two 1/8" long 6ba grub screws and the straps fitted with cups marked Oil just in case I forget what they're for.

IMG_1651 by Andy, on Flickr

IMG_1652 by Andy, on Flickr

Perhaps the straps will benefit from a bit more fettling.

Andy

[Chipmaster]

Moving on the next components were two clevises to be attached to the ends of the eccentric rods.

I machined round mild steel bar in the lathe to shape and cut 4ba thread in the ends of the clevises then over to a milling machine, mounted in a square collet block.

   IMG_1693 by Andy, on Flickr

Followed by milling a 5/32" slot, fitting a 3/16" pin and putting a radius on the end.

IMG_1699 by Andy, on Flickr

The magnified pictures really show up the scars.

IMG_1704 by Andy, on Flickr

Next came the cast bronze levers. They were rough and tough, I resorted to using a disc sander to tidy them up.

IMG_1677 by Andy, on Flickr

This is the exhaust lever.

IMG_1688 by Andy, on Flickr

IMG_1681 by Andy, on Flickr

Then the other lever that will probably control the ignition. I say probably because I haven't decided on an ignition system yet.

IMG_1713 by Andy, on Flickr

IMG_1714 by Andy, on Flickr

I haven't fixed the 150 tooth gear to the 9/32" diameter countershaft yet, mainly because it's supposed to be keyed. However, I don't have  the appropriate broach guide. I have considered using a 7mm guide that's in my kit with a piece of shim packing, or just keep it simple and use Loctite to retain the gearwheel, any advice gratefully received.

IMG_1718 by Andy, on Flickr

Andy

[pirmin]

very nice those clevices" i wanted some of this type also on my Otto Engine, but then opted for a simpler design, maybe i will remake them one day!

Nice progress on the engine so far

[crueby]

I like that design of clevis too - the rings at the base look great.

[Chipmaster]

I felt I'd have a go at making improvised oil cups for the big end and crosshead which turned out to be quite time consuming when it came to getting the knurling right, I blame the old tools. The cup for the crosshead has a small hole in the lid so the oil will flow freely whereas I haven't put a hole in the lid of big the end cup to avoid having oil scattered about when / if the engine runs. I threaded the lids 5/16" x 32 and they have 2BA threads for attaching to the engine.

IMG_1773 by Andy, on Flickr

IMG_1774 by Andy, on Flickr

IMG_1777 by Andy, on Flickr

IMG_1781 by Andy, on Flickr

I will have to dismantle the engine in order to drill and tap the trunk to fit the crosshead lubricator at the same time I might as well decide on what to make and fit for lubricating the cylinder, it's likely to be similar to these oil cups but will need to be gas tight with an O ring seal for the screw on lid.

Andy 

[PaulR]

Nice! I like the tapered ends on the studs which looks really neat and must make getting the nuts on much easier. I'd like a quick way to do that for screws - I made a little screw plate thing for filing them to length but the ends are always flat and difficult to engage.

[Krypto]

I haven't fixed the 150 tooth gear to the 9/32" diameter countershaft yet, mainly because it's supposed to be keyed. However, I don't have  the appropriate broach guide. I have considered using a 7mm guide that's in my kit with a piece of shim packing, or just keep it simple and use Loctite to retain the gearwheel, any advice gratefully received.

I think it's a law of the universe that you will always be missing the broach guide you need as I always seem to make one no matter how many are in the kit.  Luckily it's not that hard.

[Chipmaster]

Hi Krypto, I agree making a guide should be straightforward but I'm so tempted to use my 7mm guide with its 2mm broach. I would only need to wrap the guide with two to three thou thick shim to be a snug fit in the 9/32" bore of the 150 tooth gearwheel. I'll try it out on a piece of scrap.

Meanwhile, continuing with my oil cup phase I have fitted various cups threaded 2BA to the engine. I made the cup fitted over the top of the crosshead and bought the other four on eBay. It was slightly inconvenient having to turn the engine bed upside down to drill and thread the holes for the countershaft lubricators.

IMG_1791 by Andy, on Flickr

IMG_1793 by Andy, on Flickr

IMG_1795 by Andy, on Flickr

The holes left on the underside will be plugged with short bits of rod threaded 2BA then filed off level with the surface of the casting.

The cups on the main bearing caps are tilted at 45 degrees. That doesn't look right to me and they can only be half filled so I might make 45 degree elbows to re-orientate them.

IMG_1808 by Andy, on Flickr

IMG_1807 by Andy, on Flickr

Andy 
 

[Admiral_dk]

Great progress + looks good 

Per                

[Charles Lamont]

Just an idea for you, Andy. Rather than an elbow, if you don't mind a bit of JB Weld-ing, you could add the boss that should have been on the casting in the first place:

[Chipmaster]

Agreed Charles that would be aesthetically pleasing.
Thanks
Andy

[Chipmaster]

I was able to make the exhaust valves this afternoon having been excused gardening due to inclement weather. I used 5/32" silver steel for the stems and turned down some 5/8" silver steel for the valve heads. The heads were silver soldered onto the stems. Each valve was then held in a collet chuck and the angled valve faces carefully machined. The method was the same as was pictured in my 'Reply 147' in April 2025.

Here are the two valves with their springs and collars that will be retained by 6BA grub screws. The drawings show the collar is retained by split pins passed through a hole in the end of the valve stem, I might do that later on.

IMG_1816 by Andy, on Flickr
IMG_1818 by Andy, on Flickr

A view from above of the valve in the exhaust chamber.

IMG_1820 by Andy, on Flickr

The two complete exhaust chambers.

IMG_1823 by Andy, on Flickr

I have left the valve steams much longer than they should be so that I can use a tap wrench on the stem for grinding in then saw off the excess after that task is completed.

Andy