Mery Explosive Engine

[Dave Otto]

Great progress Andy!
I borrowed the mixer off of Max's engine and and made a 3d model of it. My plan is to create some dimensioned drawings and post them here on MEM. Maybe you and Jack (when he gets back) will find them of some use?

Dave
 

[Chipmaster]

Hello Dave, yes please 
I’m not aware of Jack, is he also in the process of building a Mery engine?
Andy

[Dave Otto]

Hello Dave, yes please 
I’m not aware of Jack, is he also in the process of building a Mery engine?
Andy

Hi Andy
It was this thread, he has not posted any photos of his engine. He did tell me that he was going down south for a while and I'm not sure if he has made it back home yet.

Dave

https://www.modelenginemaker.com/index.php/topic,12070.msg285227.html#msg285227

[Chipmaster]

The two explosion chambers are mounted on the cylinder using 6BA studs. The holes in the guide were opened up from 6BA tapping to clearance size and guide was used to ensure the holes lined up and weren't too close to the edges of the castings..

 IMG_1200 by Andy, on Flickr

IMG_1201 by Andy, on Flickr

Explosion chambers attached, the quarter inch diameter hole in the centre is the connecting passage to the cylinder.

IMG_1190 by Andy, on Flickr

IMG_1204 by Andy, on Flickr

IMG_1207 by Andy, on Flickr

There is a fair amount of work left to do on these explosion chambers and I have been waiting for a 7/64" reamer for the valve guides - a reamer bought on eBay  was lost in the post so I had a buy a new one at three times the price which is due for delivery today.

Andy

[Jo]

Good use of the guide Andy. These days of DROs it is too easy to over look the tried and tested (and often superior) use of the traditional ways of making sure things line up.

Did I mention  the engine is looking very good.

Jo

[Roger B]

Looking good 

Is that a fine model hammer or an engine component in the bottom left of IMG_1204?

[Chipmaster]

Thanks for the compliment Jo, the 7/64 reamer was delivered which will be used for the two inlet valve guides, hopefully over the next few days.

Hi Roger, you’re looking at a family heirloom. It’s a brass toffee hammer that was used in my great grandmother’s shop in Bristol about 1900. Do you remember slabs of toffee being broken up in sweet shops? I also remember what that toffee did to my teeth.

Andy

[Chipmaster]

Continuing work on the Explosion Chambers.

There was insufficient clearance beneath the 6BA nuts to accommodate the covers that I expect to be about 1/8" thick.

Clearance under the nuts by Andy, on Flickr

So a fair amount was milled away.

 IMG_1216 by Andy, on Flickr

IMG_1218 by Andy, on Flickr

I then milled the floor of the chamber flat.

Before,
IMG_1221 by Andy, on Flickr

On the way,

IMG_1219 by Andy, on Flickr

Finished and mounted back on the cylinder to check the two chambers line up.

IMG_1241 by Andy, on Flickr

At this stage I decided to make a 90 degree valve seat cutter. The valve heads are 1/2" diameter with 7/64" diameter stems. The end of a length of 13mm silver steel  was machined at 45 degrees and a 7/64" hole reamed through the centre to accommodate the pilot shaft. The silver steel was then mounted in a dividing head and four cutting edges machined. I got it right this time - a right handed cutter, previous efforts have turned out to be anti clockwise cutters by mistake.

IMG_1243 by Andy, on Flickr

IMG_1244 by Andy, on Flickr

IMG_1246 by Andy, on Flickr

After heat treatment and ready for cutting valve seats.

IMG_1282 by Andy, on Flickr

Back to the Explosion Chamber castings, after measuring up and marking up I was confident I could bore out the valve pockets and provision for the bronze valve guides and they would line up as per the drawings.

This is the view looking down into a valve pocket ready for a valve guide. You might notice the first threads of the inlet tract.

IMG_1270 by Andy, on Flickr

The inlet tract threaded 5/16" x 32 into the side of the valve pocket.

 IMG_1272 by Andy, on Flickr

The other explosion chamber.

IMG_1273 by Andy, on Flickr

It was important to ensure the 5/16 x 32 threaded inlets of the two chambers line up because eventually they will be rigidly connected to a gas / air mixer in between them. I threaded each end of a piece of 5/16" brass just to see that the ports were aligned.

IMG_1276 by Andy, on Flickr

With the valve seat cutter posing.

IMG_1280 by Andy, on Flickr

The explosion chamber castings are much longer back to front than the two inches specified in the drawings, almost 1/4" over as can be seen to the left of the scribed line in this picture.

 IMG_1274 by Andy, on Flickr

It's not detrimental but I intend to saw off the excess and mill the end square.

The next task will be making and fitting bronze valve guides, then I can cut the valve seats.

Andy

[RobC]

Wow great build…..   For the valve cutter,  did you grind the relief on the back of the cutting edge or can you use the dividing head on an angle.   I like the idea of inserting the guide after

[Chipmaster]

I rotated the job in the dividing head against the milling cutter  to decrease the flank ( I think that’s the term) behind the cutting edge. That was to reduce the area to be ground and filed to provide the relief. The grinding and filing was done off hand which is why the tool appears multi faceted. I was content if the cutting edges remained intact.

Andy

[RobC]

I rotated the job in the dividing head against the milling cutter  to decrease the flank

That makes perfect sense. Wish i had thought of that when making mine as had alot to grind off on my bench grinder…. Haha.   Next time

Thanks

[Chipmaster]

A leaded bronze bar was turned down to form the valve guides, machined to be a tight fit in the 9/32" diameter holes in the valve pockets, also bored 3/32" whilst on the lathe. The guides will be reamed 7/64 after they have been installed.

IMG_1283 by Andy, on Flickr

IMG_1284 by Andy, on Flickr

The tool for Knocking in the valve guides

IMG_1285 by Andy, on Flickr

IMG_1286 by Andy, on Flickr

Two valve guides in position.

IMG_1287 by Andy, on Flickr

Tomorrow I'll ream the guides out to 7/64" then have a go at cutting the valve seats.

Andy

[Chipmaster]

The valve guides have been reamed to 7/64" and my home made valve seat cutter performed fairly well.

IMG_1298 by Andy, on Flickr

I only had time to make one inlet valve today. The 1/2" diameter mild steel valve head was machined to 45 degrees, reamed to 7/64" then parted off and silver soldered to a length of 7/64" silver steel. To machine the valve face it was back to the lathe, mounted in a multisize collet chuck, centred and supported by a small live centre to machine a concentric face at the correct angle.

IMG_1306 by Andy, on Flickr

IMG_1307 by Andy, on Flickr

IMG_1322 by Andy, on Flickr

IMG_1324 by Andy, on Flickr

After a short session grinding in the valve with very fine grinding paste the valve seemed to achieve a satisfactory seal. The stem needs to be shortened to an overall length of 2.125" and a collar made to retain the spring.

Andy

[Chipmaster]

Today I made the second inlet valve and the collars that tension the springs. The collars are held by 6BA grub screws.

IMG_1330 by Andy, on Flickr

IMG_1332 by Andy, on Flickr

Andy

[Chipmaster]

How to hold and machine the two exhaust valve chamber castings was a challenge for me.

IMG_1368 by Andy, on Flickr

IMG_1366 by Andy, on Flickr

I wanted to ensure holes drilled through the centre of a face would emerge exactly in the centre of the face on the other side. Particularly where the casting around the valve stem is narrow.  To ensure the opposing faces would be parallel I marked and centre drilled each face then machined the faces of the casting between centres. Thus when I positioned the casting on a parallel in my drill press the drill should be at 90° / perpendicular to the faces and emerge in the centre, on target

IMG_1375 by Andy, on Flickr

IMG_1376 by Andy, on Flickr

IMG_1378 by Andy, on Flickr

After machining the opposite faces.
This side will become the valve chamber.
IMG_1380 by Andy, on Flickr

This is where the valve stem will exit.

IMG_1381 by Andy, on Flickr

Drilling through using a 1/8 long series drill.

IMG_1383 by Andy, on Flickr

That went well so the next task was to true up the flanges, back on the lathe between centres.

IMG_1387 by Andy, on Flickr

IMG_1388 by Andy, on Flickr

IMG_1389 by Andy, on Flickr

The two embryonic exhaust valve chambers are now mounted on the exhaust ports held by 6BA studs.

IMG_1392 by Andy, on Flickr
IMG_1393 by Andy, on Flickr
IMG_1394 by Andy, on Flickr

Andy