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 sheaves 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