Connecting rods

[wyrmrider]

I'm thinking of some early angled aluminum rods with huge amounts of metal around the pin and large capscrews and dowels around the capscrews
MT? Howards? They worked well I think we had some in early Hemi and early Olds

[clshore]

The strength of a joint with bolts in shear does not depend on fastener torque.
In a joint where bolts are in tension, the fastener is essentially a spring.
To prevent separation of the joint, the installed bolt tension must be greater than the imposed load.

It would be interesting to analyze the forces of a rod with angled caps that were cracked, rather than machined flat.
The mating cracked surfaces would not only assure alignment, but shear forces would be reacted directly through the entire face,
rather than through the bolts/dowels.

Angled caps are also seen in some Diesel Locomotive and Marine applications, likely for bore clearance.
Some of these feature serrated or patterned mating faces that would accomplish similar goals.
Taylor Volume 2 features a picture of a Sulzer locomotive rod made this way, you can be
sure that they didn't design it this way on a whim.

[DaveMcLain]

One time I asked Bill Miller if he thought that an aluminum rod would work in an automotive application with no bearing at all. He didn't think that the material would work long term yet it seems to work ok at the wrist pin end. Wouldn't it be simple? Bore the rods close to what's needed and then hone them to the exact clearance and bolt it together.

[clshore]

Aluminum directly on steel works OK, many OHC cams run this way.
But it's load bearing capacity is far less vs dedicated purpose bearing solutions.
And other desireable traits such as embeddability are not as good.
It's one reason modern bearings employ a multi-layer solution.
Another issue is eccentricity, most modern bearings are designed to fit into a perfectly
concentric housing, but the shell thickness itself is tailored to vary, different at parting line,
than 90 degrees from it.

That said, I wonder then how bearings intended for rods with angle caps are engineered?

[swampbuggy]

clshore talked about rods being manufactured with serrated mating surfaces. He said that this design you bet was not done on a whim, AGREE. The rods being used in NASCAR Sprint Cup engines are supplied by Pankl in Austria. These con-rods are made with serrated surfaces, and "ALSO" include a small solid dowel pin about .080" one on each side. So i am betting that they (whoever) have come to the conclusion that this is necessary at 10 k for 3-4 hrs to keep the big end round and not loose that very tight bering to journal clearance. JMO , Mark .

[statsystems]

One time I asked Bill Miller if he thought that an aluminum rod would work in an automotive application with no bearing at all. He didn't think that the material would work long term yet it seems to work ok at the wrist pin end. Wouldn't it be simple? Bore the rods close to what's needed and then hone them to the exact clearance and bolt it together.

IIRC, Yeager rods could used WITHOUT a bearing. I think KB racing used them before anyone else.



The rocket surgeons in Glendora banned that shit right quick.

[modok]

Not a big fan or the serrated rods, or the early cummins, actually I think the design on the dt466 rods best. Holds up just as well and is easy to work with. The cracked rods are cool but I still see some distortion at the surfaces, but can't fix it, although there are a few tricks to doctor them slightly, such as bead blasting the cracked surface, and many have oversize OD inserts availible.
Aluminum rods don't need inserts! that's true, but I think the ideal alloys differ quit a bit, but it works for briggs.
I told my co-worker today that the rods are angled so they fit down the hole, and I saw the light go on. That's funny, doing this for 30 years and never bothered to wonder why they were, but, I guess we don't really need to know anyhow.

[swampbuggy]

The serrated mating surfaces on the Pankl con-rods are machined, they probably have to trash them if the big end becomes out of spec.'s .

[modok]

If I can fix those, then many others can too. It's not impossible at all.
Same as Perkins rods right?

[4sfed]

Aluminum directly on steel works OK, many OHC cams run this way.
But it's load bearing capacity is far less vs dedicated purpose bearing solutions.
And other desireable traits such as embeddability are not as good.
It's one reason modern bearings employ a multi-layer solution.
Another issue is eccentricity, most modern bearings are designed to fit into a perfectly
concentric housing, but the shell thickness itself is tailored to vary, different at parting line,
than 90 degrees from it.

The aluminum/boron metal matrix composite rods used for a short time in F1 ran without bearings to save weight. A coating was applied inside of big ends to address embedability, and providing eccentricity in the rod is easy.

I can't buy bearings for my 40 year old engines that have enough eccentricity, so the rods are modified to make the bore of the big ends wider at the parting line than they are tall . . . effectively increasing the eccentricity of the installed bearings.
-

[dwilliams]

many have oversize OD inserts availible.

Early flathead Fords used "floating" rod bearings; the shells fit with clearance between the crankpin, shell, and rod bore. The shells were not keyed, so they rotated independently of the crankpin. Replacement bearings were available with undersize ID and overside OD.

Bruce Crower did something similar with the wristpins of his turbocharged Indy motors. He had problems with the wristpins locking in the rods. After playing around with clearances and bushing materials he tried floating the bushings in the rods as well as on the pins and said it worked. He was probably running into wristpin flex issues, but Bruce always liked to think outside the box.

[modok]

many have oversize OD inserts availible.

Early flathead Fords used "floating" rod bearings;

yeah, and it's a total PITA. The bearings i had to work with were not arched right
if there's anything i dislike more than subaru....It's old fords.

Works good for turbohcargers of course, then they have a reason to float besides just for the heck of it