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pshort · Posted: Tue Sep 13, 2005 19:25 Post subject: Hispano Suiza connecting rod

The new book "The V12 Engine" by Karl Ludvigsen has been mentioned in another post.

This concerns a car engine, but it is a very nice one, and with an interesting construction detail. I posted this question on a machining Forum with quite a few gearheads, but no one had seen or heard of it.

When describing the J12 engine which appeared in the early 1930's, the author describes a curious connecting rod design which I haven't heard of. Can anyone enlighten me further on this - I am having trouble picturing how it works.

After explaining that the 250mm rods were machined from solid and had tubular shanks which were drilled down from the top, the resulting hole in the small end being left open, he describes the big end:

"The rods' big ends were unique. Meshing teeth formed on both the rod and the big-end cap were drilled so the cap could be secured by two tapered pins, inserted through the teeth along the longitudinal axis. Though demanding impeccable machining skills, this was an ultra-light configuration completed by ribbing for strength around the big end".

Anyone got an old book with an illustration of this?

It was a mighty engine, beautifully finished - this was back in the days when one might be proud to lift the bonnet side and display the engine to admirers.

pshort · Posted: Tue Sep 13, 2005 19:31 Post subject:

Not really related to the above, but when I posted this question on the maching Forum, this interesting photo was posted.

The Illustration is from a J.H. Williams & Co. Catalog which is from circa 1921, courtesey of Frederick Harvie

szielinski · Joined: 13 Jul 2003 Posts: 94 Location: Canberra, Australia

I'm not really sure what is meant by "longitudinal axis" in your post. If you mean the axis longitudinal (parallel) to the crank, then look in the letters section of your TM magazines. There is a picture of a Hispana-Suiza (I think) conrod with a construction remarkably similar to your description - with a picture !
Sorry I can't remember the issue - If no-one refreshes our memory, I'll post it later.
HTH!

pshort · Posted: Sun Sep 25, 2005 19:06 Post subject:

szielinski,

Excellent! That must be it! Thanks for letting me know. And the photo I wanted was less than a metre away from me, in Torque Meter vol. 2, No. 1, pg 35.

I really don't know enough about these engines to comment with authority, but the photo is described as being a Hispano-Suiza 12Y45 blade con rod, however Herschel Smith indicates that the 12Y used 'main and link' rods (although the 12X used blade and fork rods)

It looks like it might be a rod from the J12 car engine?

I will try and contact Robert Storms, the writer of the letter.

Once again, thanks for helping find a photo of this most unusual design.

pshort · Posted: Thu Sep 14, 2006 16:24 Post subject:

Thanks to Jerry Wells for letting me know the patent number for the above connecting rod. Note, there are several pages to look at eg "original document" etc. The US patent has better (larger)drawings.

Although this type was used on the J-12 automotive engine, I see the drawings show connections for link rods, both V and W layouts.

http://v3.espacenet.com/textdoc?DB=EPODOC&IDX=GB331618&F=0

http://v3.espacenet.com/textdoc?DB=EPODOC&IDX=US1927768&F=0

Here is another Marc Birkigt patent using the castellation and pin idea:

http://v3.espacenet.com/textdoc?DB=EPODOC&IDX=DE615242&F=0