Announcing the Merc 888

[Krazy Karl]

Master Rod



Crank Shaft




Continental 220 Radial Engine

Some pictures to show those who have never seen the insides of a 40's radial engine. These are still used commercially in crop dusters.

kk

[smittythewelder]

Tim, the part of this link that might be of immediate interest is halfway down the page, on the left:

http://crosleyautoclub.com/EngineTre...ng_Tree-3.html

[Tim Kurcz]

Tim, the part of this link that might be of immediate interest is halfway down the page, on the left:

http://crosleyautoclub.com/EngineTre...ng_Tree-3.html

Fantastic! The concept has been built before; at least in 4-stroke form.

Excellent image contributions, all. Please keep them coming!

Tim

[Powerabout]

Tim, the part of this link that might be of immediate interest is halfway down the page, on the left:

http://crosleyautoclub.com/EngineTre...ng_Tree-3.html

I like that, a stock rod with new cap and one custom rod.

[Tim Kurcz]

I like that, a stock rod with new cap and one custom rod.

Basically, that's what is planned for the 888. A prototype will be built welding a "blade" to the existing Mercury rod cap. The matching "fork" will be machined into a custom link rod. These will be constructed to complete swing testing and clearancing of the opposing block.

[Powerabout]

Basically, that's what is planned for the 888. A prototype will be built welding a "blade" to the existing Mercury rod cap. The matching "fork" will be machined into a custom link rod. These will be constructed to complete swing testing and clearancing of the opposing block.

Merry Christmas Tim
how hard is it to make a rod for an outboard?
I have never seen the process?
Thinking of the 8 rare rods in my v8

[Yellowjacket]

Basically, that's what is planned for the 888. A prototype will be built welding a "blade" to the existing Mercury rod cap. The matching "fork" will be machined into a custom link rod. These will be constructed to complete swing testing and clearancing of the opposing block.

Careful with welding on the rod cap. If you weld on it make sure that it is round when you are done. Welding will distort the cap and also anneal the rod cap (that is a forged part) so it will be softer than it was before the welding. Also the inner surface of the rod cap is hardened to work as a bearing surface. Grinding too much on that surface will also soften it and it won't last long under the contact stress... These rod caps are generally opened up for clearance but doing that only takes about a half thousandths off of the bore (or about a quarter of a thousandth off of each side) so there isn't much of a problem with taking too much of. But if you take off three thousandth's from a surface you are likely to be getting through the hardened surface and the surface will spalling off in short order.

If you change the bearing clearance by a half a thousandth then that's a lot, so you will probably have to clean it up when you are done welding.

[Tim Kurcz]

Careful with welding on the rod cap. If you weld on it make sure that it is round when you are done. Welding will distort the cap and also anneal the rod cap (that is a forged part) so it will be softer than it was before the welding. Also the inner surface of the rod cap is hardened to work as a bearing surface. Grinding too much on that surface will also soften it and it won't last long under the contact stress... These rod caps are generally opened up for clearance but doing that only takes about a half thousandths off of the bore (or about a quarter of a thousandth off of each side) so there isn't much of a problem with taking too much of. But if you take off three thousandth's from a surface you are likely to be getting through the hardened surface and the surface will spalling off in short order.

If you change the bearing clearance by a half a thousandth then that's a lot, so you will probably have to clean it up when you are done welding.

Most outboard rods are forged steel, copper plated (carburize mask), rough machined (removes copper plate from intended surfaces), assembled, carburized, then finish machined (ground/honed). Copper plated areas are soft, only the bearing/wearing surfaces are hardened. To prove this to yourself, clamp a spare rod in a vice, apply torsion with a pipe wrench, and watch it twist without shattering.

For the proto rod, copper will be removed from the cap, the extension blade tig welded in place with the rod assembled and fully torqued. Following, the journal bore will be honed round and to size, and the pivot bore will be machined.

After swing fitting, the proto rod and cap bearing surfaces will be Brinnell tested. If there is no significant difference, the 888 might be run with welded rods. If the difference is unacceptable, custom rod caps will be machined, and the bearing surface will be carburized, honed, etc.

Side note: It might surprise you to know that mod outboard racers have been honing .002" - .0025" from the big end bores for many years. This procedure followed Mercury's change from .880" to .882" crank pins. It allowed rods to survive race conditions without overheating (bluing).

[Powerabout]

why do they copper plate?
Do you need to freeze them to break the cracked cap types?
does the big end need to be harder to do this?

[smittythewelder]

After welding and BEFORE re-machining, you might consider shot-peening and even cryo-treating the rod . . .