Mery Explosive Engine

[Jo]

Sorry for the side track 

I'd make up some wedges to go between the holes to give you a vertical surface. A flat steel bar between them for mounting the scale on. I would position it out far enough for the swarf to fall in front (behind  ) the steel bar and the scale mounting surface would line up under the main taper casting. Then you just make a "hotchpotch" of brackets to provide the head mounting.




I have no problem using the taper turner with the DRO fitted.

Jo

[Chipmaster]

Thanks for the pictures Jo.

Andy

[Jasonb]

I would have thought 1.5" is ample room for a magnetic scale and compact or mini read head, even enough there for a cover to keep most of the swarf off

https://www.machine-dro.co.uk/digital-readouts-display-and-encoders/linear-encoders/m-dro-magnetic/m-dro-ehc-series-compact-head-with-565mm-22-1-4-inch-reading-length-magnetic-tape-encoder

[Alyn Foundry]

Hi Andy.
I’m watching your build log with great interest. As a few are aware I too have a set of castings that were secured over 24 years ago following a straight swap with Roland Morrison for one of my Gardner engine kits. We also met up in 2000 for the N.A.M.E.S show the same year.

You are very wisely taking the utmost care in the setting up of the main bed casting…..( it’s surprisingly fragile. ) I passed mine onto a friend that operated a rather nicely equipped jig borer at his employer’s establishment. There was what can only be described as a ‘ butterfingers moment’ when the casting was accidentally dropped onto the bed of the machine. This resulted in the entire front end breaking off and needing repair. The repair, by Silver soldering, was successful but it really put me off from moving forward with the project. The only part that got machined was the flywheel…… but I DO like machining flywheels 


   Graham.

[Chipmaster]

Hi Graham, the accident that befell your casting was tragic, i will treat mine with even greater care.

Jason, here's a better picture of the 'bridge piece' being used to help position the casting.

IMG_8568 by Andy, on Flickr

I also superglued a short piece of steel across the 'cylinder end' of the casting that was also marked out and centre drilled.

IMG_8565 by Andy, on Flickr

I put the dial test indicator there to check for movement when setting up and during machining. 

The boring bar was home made from a length of 1" precision ground mild steel.

IMG_8570 by Andy, on Flickr

Mounted in a Multi Collet Chuck.

IMG_8572 by Andy, on Flickr

Away we go....these are videos on Flickr

I used 35 rpm and a fine feed initially so that I had time to stop the lathe should there be any problems, it was interrupted cuts most of the way.

A machining the Trunk Guide by Andy, on Flickr

At that rate it took about 35 minutes to traverse approximately six inches. I increased the speed and feed after the job had settled down.

From one end to the other by Andy, on Flickr

Boring video at higher speed, 35 minutes boring in 53 seconds.

35 minutes boring in 53 seconds by Andy, on Flickr

Andy

[Jo]

Sounds like the Cast Iron is good stuff 

Any reason you didn't use a between centres boring bar?

Jo

[Chipmaster]

Hi Jo,
Yes I thought between centres was the way but the 'bridge piece' part of the casting between the main bearing housings was still there at that stage, preventing a between centres job. The bridge piece could have been removed to make way for a boring bar but I mistakenly thought it might be useful later on.

Bridge Piece by Andy, on Flickr

I had used that 12” long boring bar between centres on my Retlas main bearings and the Retlas Dynamo but it wasn't long enough for the Mery trunk guide.
I did consider a longer 1" diameter pgms boring bar but it would have needed to be about 20" long and expensive even if I could obtain such a length.

Andy

[Jo]

I have been wondering, other than during the pour, how that bridge could be useful. Maybe Graham can confirm how it helps during the casting process and if there is anything we have missed  .

Jo

[Alyn Foundry]

As we’re aware by now the bed casting is rather thin and delicate. I’m pretty confident that the bridge served two or even three functions.

Primarily to form the ‘ cheeks ‘ for the inner main bearing, increase the rigidity  ( for machining the main bearing area ) and ensure that adequate metal was available on the much thicker sections in the main bearing areas.

   Graham.

[Jasonb]

Would certainly have helped if anyone had wanted to use a shaper to fo the flat surfaces of the bearing housings by spreading the sideways loads

[Chipmaster]

While the cross slide was still locked in position I used a boring head to machine the outside of the flange that the cylinder will be attached to.


Flickr video with serious chatter!
IMG_8591 by Andy, on Flickr

IMG_8596 by Andy, on Flickr

Then loosened the gib strips on the cross slide and faced the end of the casting.

IMG_8606 by Andy, on Flickr

IMG_8603 by Andy, on Flickr

The casting had to be lined up with the central axis of the lathe again in order to bore a recess that will accommodate a stuffing box. I have found these co-axial indicators very reliable.

IMG_8607 by Andy, on Flickr

IMG_8609 by Andy, on Flickr

IMG_8610 by Andy, on Flickr

The multi position stop and feeler gauges were used to set the depth of the recess.

IMG_8614 by Andy, on Flickr

IMG_8617 by Andy, on Flickr

The casting was ready for milling the main bearing housings. I did consider using a shaper Jason but decided that might be risky.

Andy

[Jo]

Nice use of a boring head 

Jo

[Chipmaster]

Cheers Jo and now for the 45 degree main bearing seats.

First check the adjustable angle plate. I set it with a quality British made combination set, the scale on the angle plate was 4 degrees out, why bother to fit such a rubbish scale ?

Preparing to mill the main bearing seats at 45 degrees. by Andy, on Flickr

It took quite a bit of patience to get the casting set up ensuring the 18" long gauge plate didn't foul parts of the milling machine. The gauge plate continued to be essential with even more holes drilled and some threaded for half inch Whitworth studs.

Preparing to mill the main bearing seats at 45 degrees. by Andy, on Flickr

Testing the set up with clamps

Preparing to mill the main bearing seats at 45 degrees. by Andy, on Flickr

Preparing to mill the main bearing seats at 45 degrees. by Andy, on Flickr

Ready to go
IMG_8645 by Andy, on Flickr

Milling the main bearing seats at 45 degrees. by Andy, on Flickr

Milling the main bearing seats at 45 degrees. by Andy, on Flickr

I stopped at this stage because the casting was becoming thinner where the main bearing studs would go.

Andy

[Jo]

  That shows just how big the main casting is in comparison with a normal sized home milling machine. Looks like you have over come the challenges 

I was converted over to a Wixey angle gauge clone for setting up angles, the Chinese knock them out for about a tenner each  Using it is so much easier than getting out my angle vernier all the time.

Jo

[Chipmaster]

Hi Jo, I'd forgotten those Wixey type angle gauges existed, at that price I might treat myself to one or even two.

My next Mery job was to prepare the main bearing caps, bolt them to the main casting and bore them to take the main bearings. The 18" length of gauge plate used to mount the main casting continued to be indispensable.

Milling the main bearing caps by Andy, on Flickr

Main bearing caps faced by Andy, on Flickr

Milling the main bearing caps bolt pads flat by Andy, on Flickr

An awkward set up.
Main bearing caps drilled 3mm to be tapped 4 BA. by Andy, on Flickr

Tapping engine bed 4BA by Andy, on Flickr

Milling to accept the crankshaft + bearings.

Main bearing caps and housing milled to create a gap of 1.5" for the crankshaft. by Andy, on Flickr

Boring for the main bearings.

Centre drilled ready to bore 5/8" to house the main bearings. by Andy, on Flickr

Job done

Job done, ready for main bearings. by Andy, on Flickr

Using a dummy crankshaft to establish the position of the pivotal shaft.

Using dummy crankshaft to establish position of the pivotal shaft by Andy, on Flickr

Andy