Just curious, has anyone ever built hollow connecting rods? What about fabbed/welded rods? It seems you could make super strong light weight hollow rods. I remember a few years back when I was into mountain biking the new thing was shimano hollow crank arms, they where stiffer than standard arms and lighter weight.
12-08-2006 07:20 AM
There is a little more force on a connecting rod than a bicycle bell crank.
12-08-2006 11:43 AM
Obviously there is more force on a connecting rod but the fact remains that a hollow tube is stronger than a solid bar of the same weight. Why do you think roll bars are hollow tubes and not solid metal rods?
12-08-2006 11:59 AM
"but the fact remains that a hollow tube is stronger than a solid bar of the same weight"
That is not necessarily true. Hollow tubes have a greater capacity for compression forces than a solid bar. In the case of tensile strength, a solid bar has more strength than a hollow tube. And the longer the member is, the less compression force it can handle. So in my opinion it would be a better idea to go with a solid member vs. a hollow one in terms of what would handle the variety of forces better (compression, tension, etc).
12-08-2006 12:06 PM
A connecting rod is not subject to large torsional stresses that favor a hollow tube, and a forged single piece I-beam or H-beam is much easier to manufacture and machine.
12-08-2006 12:14 PM
Jerking the piston down from the exhaust stroke against the inertia of the piston and vacuum above it is what kills rods. That comes from rpm mostly.
Yes, There are/were "hollow" connecting rods made. I have had a set in my hand before and know a guy that still owns them. Do a search for Mekart, Meckart or Mechart rods. Don't remember how it was/is spelled. They were very light and looked impressive, no real world experience with them though/
12-08-2006 08:35 PM
Welded rods??? WAAAAAY back in the day, before all the wazooo aftermarket conn rods came out there was a company called " Dons Boxed Rods" He actually tig welded a boxing plate on both sides of a stock rod, kind of like boxing a frame. Never saw one, must have been very heavy and hell to balance an engine but he made them, used to advertise in Hot Rod.
12-09-2006 08:54 AM
Ansen used to make hollow rods. I don't recall the material. I think there were some that were titanium.
12-09-2006 08:57 AM
Here you go, these are a version of Mechart rods. Very similar to the ones I mentioned above for a SBC.