HarleyTechTalk

OK so for a performance build how bad are these stock rods. What are you guys seeing in actual use in the field? 

Are you referring to the taper-top, OE T/C connecting rods?
That has been used in the diesel industry for years now.
Scott

Of course and that is tough service for sure.
Your opinion then?

And that said why bother then with "H beam" rods? Who makes those anyway?

The tapered top is done to reduce the overall weight and move the strength in the rod to where it's needed. Think about what part of the pin area is used for what and it makes perfect sense. The top of the pin area is only used to pull the piston down the bore on the intake stroke. So by removing the metal from up top and adding it back on the bottom where all the load is makes the pin area stronger for what it's used for. It also allows the piston to give more surface area on the pin during the power stroke if made properly with no increase in weight. As said before it's been around for some 30 years in the diesel industry and is well proven.

Just thinking out loud.  When these are used in a Diesel the clearances are more than likley much closer as far as cylinder/piston which reduces lateral movement of the piston in the cylinder (Makes sence?).  With Forged pistons in an air cooled Harley the clearance is a bit looser.  This one would think could/will cause more stress on the top piston pin area due to more movement of the piston in the cylinder.  I would prefer having more material on the small end end of the rod likke the "H" beam uses. 

As Scott and Steve stated, these rods have been used in diesel applications and other applications for years without issue.  Although as a T/C Crankshaft rebuilder we have not experienced any issues with these rods (Bushed or Non-Bushed) when using stock length skirted pistons, but have experineced issues of small end wear on the front rod because of piston rock with "Slipper Skirt" pistons.  We rebuild hundreds of T/C crankshafts each year and these are our findings.

Our suggestion to our customers is if you are using stock length skirted pistons, re-use the stock rods, if you are going to use "Slipper Skirt" pistons replace the rods with either the earlier style rods or the H-Beam rods.  We have found that the front rod is always the one that has the  wear and have found that this is attributed to the severe rod angle on the front cylinder.  Also in rebuilding crankshafts we also find that the front rod big end, cages and bearings are always the loosest and need resized.  In severe applications, we turn the rods around and run the female rod in the front and this virtually stops the rocking and wearing. 

Hope this information is helpful.

Quote from: Deweysheads on January 07, 2012, 09:38:51 AM
And that said why bother then with "H beam" rods? Who makes those anyway?

More to the rod than just the tapered wrist pin area. Never had a problem with the design myself but there have been reports of the bushing rotating and jamming the pistons tapered area where the rod sits. Probably from less bushing area press fit.  I think the design is best suited for a no bushing rod.  Rigididity and anti stretch would be more inline for H beams. I have these same rods in the crank I have for sale in this forum. Very stout.
Ron

What make the front rod angle more severe? From what I see the bore is centered to the crank for both the front ant rear cylinder. Geometry is the same for both.
Max

Quote from: Hot-Shot Motorworks on January 07, 2012, 11:55:23 AM
As Scott and Steve stated, these rods have been used in diesel applications and other applications for years without issue.  Although as a T/C Crankshaft rebuilder we have not experienced any issues with these rods (Bushed or Non-Bushed) when using stock length skirted pistons, but have experineced issues of small end wear on the front rod because of piston rock with "Slipper Skirt" pistons.  We rebuild hundreds of T/C crankshafts each year and these are our findings.

Our suggestion to our customers is if you are using stock length skirted pistons, re-use the stock rods, if you are going to use "Slipper Skirt" pistons replace the rods with either the earlier style rods or the H-Beam rods.  We have found that the front rod is always the one that has the  wear and have found that this is attributed to the severe rod angle on the front cylinder.  Also in rebuilding crankshafts we also find that the front rod big end, cages and bearings are always the loosest and need resized.  In severe applications, we turn the rods around and run the female rod in the front and this virtually stops the rocking and wearing. 

Hope this information is helpful.

Hmm: I always thought the front wore more because of the odd firing and degrees the front did a bit more work than the rear under load?
Ron

Quote from: Deweysheads on January 07, 2012, 09:38:51 AM
And that said why bother then with "H beam" rods? Who makes those anyway?

Eagle was manufacturing(importing) Evo rods at one time, that looked extremely similar, but as far as the T/C counterpart, I do not know for sure. Ultima?
One thing, I'll bet dollar to donuts, that the T/C H-beam rods, ARE NOT, made here.
Hoban Bros. prefers the H-beams for better wrist pin support, as was told to us.
Scott

So what, my Hyundai got me to the dealer and back today.
Ron

       Never herd the term "slipper skirt pistons" ? .... Can somebody give me a description. Thanks.

The original name,slipper skirt, came from the 60s. It was a drag racing piston with tephlon buttons installed in the skirts (not the pin holes). In this context I expect it refers to narrow skirt pistons like Wisecos.
max

When I spoke with Hoban about my build they were more concerned about the rods than the possible crank issues.Ended up doing both and had them install "their own"h beams as opposed to the import option.Not sure who actually made them though.

Hotshot

"We have found that the front rod is always the one that has the  wear and have found that this is attributed to the severe rod angle on the front cylinder".

Having some trouble digesting that.So the rear cylinder has less of a "rod angle" than the front?

I'd sure like to hear that expounded-upon, too.  I could see where on average the front cylinder is trying to accelerate the crank harder than the rear because it'd been 90° crank rotation longer since the last power stroke compared to what the rear cylinder sees in that respect.  But without seeing the actual drawings or carefully measuring things, I can't envision the rod angles being any different front-to-rear.

 

Also,  the length of the piston skirt on a Diesel is conciderably longer than any Gas powered vehicle i've seen.  This IMO aides to the stability of the piston within the cylinder of a diesel.  Durring the power stroke a diesel will direct it's energy more precicly thru the rod.  In some of these high power Harleys with short skirt forged pistons they fit much more loosly and IMO will cause additional strain on the small end due to more movement of the piston within the cylinder.  Maybe i'm wrong but from this view it makes sence.  As far as diff. angle front to rear on a Harley I have never heard of that... Love to hear the explination. 

Are you guys being kind since it's Hot Sh*t's first post?

You get more second posts with honey than with vinegar, right?

Quote from: glens on January 07, 2012, 03:17:03 PM
You get more second posts with honey than with vinegar, right?

Ron

The 110" we did that was 133/127tq sae 5th gear had a stock crank in it. No issues so far. Beginning to think that the stock crank may not be the end of the world afterall. It may not be to the strict standards of HTT but i think it will suffice in most builds

Quote from: machinist on January 07, 2012, 03:10:56 PM
Are you guys being kind since it's Hot Sh*t's first post?
[/quote i
he is somebody we want posting. They have a great reputation and a lot to share.

I mean no harm.