Pauter Rod thoughts

JustinOlson · Post by **JustinOlson** » Mon Apr 03, 2006 12:58 pm

What are the feelings around here about pauter rods? I've heard very good things from some top Import crew chiefs that swear by them, but I couldn't find any thread referencing them here. Some people claim that there design is uncommon. If it was such a great design it would have been copied by other companes.

http://www.pauter.com/4340_rods.htm

Any BTDT?

OldSStroker · Post by **OldSStroker** » Mon Apr 03, 2006 2:54 pm

No personal experience with the Pauter rods, but some thoughts:

E4340 Vacuum melt material is an excellent choice. Perhaps the only thing better is Vacuum Arc Remelt (VAR) material which is cleaner and stronger due to fewer micro-voids or micro inclusions. VAR should probably be used for billet only parts, as forging can induce junk into the material. If the rod is not machined on 100% of the forged surface you risk decarb and inclusions. I couldn't tell from the website, but they appear to be 100% machined.

The "reverse H-beam" design seems to put most of the material along the centerline of the bores which doesn't appear to me to be as good at distributing loads to/from the hoop end as a conventional I or H-beam design does.

I'm not sure how many Cup engines, with min weight rod rules, use this design. As with their pistons, Cup engine parts get about the most strength they can form the weights they are required to use. I guess if I really wanted a low windage rod I'd make the beam more oval or diamond shaped than flat with a wall in the middle.

There are many ways to skin a cat, and this design may work well. I just haven't see it used too often in higher end engines. Perhaps it is, however. They do appear to be high quality pieces. How do these rods compare to Carillo for pricing?

My $.02

Nwguy · Post by **Nwguy** » Tue Apr 04, 2006 1:14 am

$1568 per set of eight. That is for some pretty exotic brands( ferrari, fiat, MG), I would hope that SBC would be less than that.

Tycho · Post by **Tycho** » Tue Apr 04, 2006 6:01 am

Any first year mechanics of materials book will have a section discussing bending moment and optimal material distribution. Here's one example:

http://hsc.csu.edu.au/engineering_studi ... tress.html

For a beam to resist an applied bending moment, the material from which it is made must develop a moment over its cross-sectional area that resists the applied moment. An extremely thin beam has little ability to resist the applied moment (little material between the neutral axis and the top or bottom of the beam. The more material the beam has on either side of the neutral axis, the greater is its ability to resist the applied moment and therefore the applied load.

Pauter's design has MOST of its material located on the neutral axis. This is bad.

They overcome this intrinsically inferior design with good materials selection, precise machining, and careful inspection (they make it work)...but the fact remains that an X is just about the worst design possible.

Niles · Post by **Niles** » Tue Apr 04, 2006 6:57 am

I agree with Tycho. How does the weight of the rod compare with that of a comparable H beam? The H beam would have a much greater structural moment and thus hopefully make use of that by decreasing the reciprocating mass of the rod.

DavidNJ · Post by **DavidNJ** » Tue Apr 04, 2006 9:55 am

Yes...on the neutral axis. However, everyone uses H-beam and I-beam rods without issues. Each has its mass on the neutral axis of one plane, each with a different plane. In the I-beam rod the bending stiffness is in a plan that has bearings on each end that prevent bending torques from being applied.

The Pauter design has the most mass where an EDM hole would go.

So, IMHO, rod bending stiffness doesn't seem to be an issue. However, the Pauter rods are neither inexpensive nor light, so I'm not sure why they would be selected over a Carillo, Crower, Dyers, Kings, etc.

Keith Morganstein · Post by **Keith Morganstein** » Tue Apr 04, 2006 11:22 am

The rods remind me of the "blade" rod of a "fork & blade" rod set used since the dawn of the vee engine in the early days in every thing from harleys to giant EMD deisels. I suppose they are strong enough.

thundair · Post by **thundair** » Tue Apr 04, 2006 12:06 pm

Just a thought, but the 'I' beam and the 'H' beams are both poor in torsion loads.

I would still like to know, what is the direction of the load that breaks the rod. My guess is the critical alignment of the pin end to the BE is some how askew, maybe with growth differences or inclusions distorting the wall strength. All this leads to failure in torsion and if that is true then all the open wall rods are suspect...What say you??

Cheers

Unkl Ian · Post by **Unkl Ian** » Tue Apr 04, 2006 12:56 pm

Pauter is know for their work on pancake 4 cylinders.

Some people feel that using an H-beam,in a horizontally
opposed motor,allows oil to collect on the top side of the rod,
throwing off the balance.

Unkl Ian · Post by **Unkl Ian** » Tue Apr 04, 2006 12:59 pm

"I would still like to know,
what is the direction of the load that breaks the rod. "

While rods may twist and distort as they fail,
I suspect,they fail in tension or compression.

The torsional loads would be minimal,in comparison.

OldSStroker · Post by **OldSStroker** » Tue Apr 04, 2006 4:50 pm

Tension usually initiates rod failure. TopFuel might be a big exception. Stopping the piston at TDC, especially on the exhaust stroke, puts the largest tension load on the rod, and tends to distort the cap. If that seizes the bearing to the crank, or breaks a bolt the failure can propagate from there.

The rods I've seen broken in the beam were usually the result of a failure someplace else and the rod being pushed into the side of the block or into the piston which was wedged sideways in the bore. IOW, the beam didn't fail first, it was a consequence of failure somewhere else.

If you are restricted to a minimum rod weight, wouldn't it be a good idea to minimize the mass (weight) at the small end (reciprocating) and move more of it to the cap (rotating) which would lessen the inertia (tension) load on the rod?

I still like the A-frame rod design, especially for very short rods. Think about a F1 engine with a 1.56 stroke and a 2.1:1 rod/stroke ratio. That's about a 3.25 long rod. A-frame rods might be used here.

Keith Morganstein · Post by **Keith Morganstein** » Tue Apr 04, 2006 5:05 pm

With rod failures i see them fail in the beam. Imports from inclusions left in the steel. recons from rough handling, leaving a stress raiser in the beam. Had a certain beefy oem rod failing right were the trademark was stamped.

Bent rod seem to be from the reasons you discuss, especially piston seizure or hydro locking. they seem to bend linear to the rotation of the crank. The panter rod is probably very resistant to that.

By "A" frame , do you mean the old mechart rod ?
I still have a set of them, but only seven good ones and havent found a spare yet.
the eigth is slightly twisted and I'm not sure you can straighten a rod like that.
Can you??

OldSStroker wrote:Tension usually initiates rod failure. TopFuel might be a big exception. Stopping the piston at TDC, especially on the exhaust stroke, puts the largest tension load on the rod, and tends to distort the cap. If that seizes the bearing to the crank, or breaks a bolt the failure can propagate from there.

The rods I've seen broken in the beam were usually the result of a failure someplace else and the rod being pushed into the side of the block or into the piston which was wedged sideways in the bore. IOW, the beam didn't fail first, it was a consequence of failure somewhere else.

If you are restricted to a minimum rod weight, wouldn't it be a good idea to minimize the mass (weight) at the small end (reciprocating) and move more of it to the cap (rotating) which would lessen the inertia (tension) load on the rod?

I still like the A-frame rod design, especially for very short rods. Think about a F1 engine with a 1.56 stroke and a 2.1:1 rod/stroke ratio. That's about a 3.25 long rod. A-frame rods might be used here.

wbclassics · Post by **wbclassics** » Tue Apr 04, 2006 5:15 pm

OldSStroker wrote:I still like the A-frame rod design, especially for very short rods. Think about a F1 engine with a 1.56 stroke and a 2.1:1 rod/stroke ratio. That's about a 3.25 long rod. A-frame rods might be used here.

I have no idea what the F1 boys are using now, but the Ferrari 049 V10 (about five-six years old now?) used an I beam type rod.

http://members.atlasf1.com/desmo/pistone.jpg

http://members.atlasf1.com/desmo/pistone2.jpg

OldSStroker · Post by **OldSStroker** » Tue Apr 04, 2006 10:26 pm

wbclassics wrote:
OldSStroker wrote:I still like the A-frame rod design, especially for very short rods. Think about a F1 engine with a 1.56 stroke and a 2.1:1 rod/stroke ratio. That's about a 3.25 long rod. A-frame rods might be used here.
I have no idea what the F1 boys are using now, but the Ferrari 049 V10 (about five-six years old now?) used an I beam type rod.

http://members.atlasf1.com/desmo/pistone.jpg

http://members.atlasf1.com/desmo/pistone2.jpg

That rod approaches an A-frame design. I don't know how to scan/post pics here, but on page 73 of Ian Bamsey's book V10 Formula One Engine Technology there is a full page picture of an I-section 2 bolt titanium con rod typical of the V10 era with serrated joint between the rod and cap. It is almost a perfect A-frame design with slightly concave sides.

Note that some F1 rods are located by the pistons, not the crank throws.

BigMoose · Post by **BigMoose** » Wed Apr 05, 2006 7:04 pm

FWIW I played around with some FEA analysis on another board. These are not precise "take it to the bank" FEA runs, like one would do in a business situation. I just ran them for fun, and to show some new members how the rod big end pinches in at the top with high RPM, sometimes resulting in spun bearings.

Here is a still:

Here is a link to where some .avi video's of the distortion are:
http://www.mtggraphics.com/bigmoosesubpages/fea.htm

Might be interesting/fun to someone who never saw the pinch in before.