HarleyTechTalk

Hoban offers h-beam rods from across the pond as well as from the USA. I run the H beam in my 113", the SE rods in that 4.375" assy. had noticable movement in 10,000 hard miles. The Hoban H-beams have been good through 42,000 miles (some abusive) so far.

Isn't the firing order harder on the equipment in a V-Twin than a diesel?

Quote from: Deye76 on January 07, 2012, 04:47:56 PM
Hoban offers h-beam rods from across the pond as well as from the USA. I run the H beam in my 113", the SE rods in that 4.375" assy. had noticable movement in 10,000 hard miles. The Hoban H-beams have been good through 42,000 miles (some abusive) so far.

Isn't the firing order harder on the equipment in a V-Twin than a diesel?

I noticed my Hbeam Darkhorse the same. 13k when I pulled it and not change one bit since install.
Ron

I think my concern was more of a tolerance issue, bushing press fit, not a statement about the tapered rod design. I haven't seen any of these rods let go but I have seen bushings spin. It wouldn't be hard to bush and ream them with a little more press and premium material even with the crank in the bike on a top end.

Quote from: Jaycee1964 on January 07, 2012, 03:07:47 PM
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.

Well the amount of power produced by a HD is no where close to what many diesels produce today and the pistons are much shorter than you think. Just to give you a little idea a few of our diesel race engines produce over 3.5Hp per cu. in.! Using this rod design there are no failures at these power levels so I doubt it will be an issue in a HD. As for how well HD installs bushings and controls the clearances, that's anyones best guess.

Water cooled engine clearances Verses Air cooled.  Also, a Diesel doesn't rev as much.  There are differences.

Quote from: Steve Cole on January 07, 2012, 06:54:01 PM

Quote from: Jaycee1964 on January 07, 2012, 03:07:47 PM
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.

Well the amount of power produced by a HD is no where close to what many diesels produce today and the pistons are much shorter than you think. Just to give you a little idea a few of our diesel race engines produce over 3.5Hp per cu. in.! Using this rod design there are no failures at these power levels so I doubt it will be an issue in a HD. As for how well HD installs bushings and controls the clearances, that's anyones best guess.

Agreed with the above. But I also agree just because other industries run these with great results doesnt mean HD didnt do a piss poor rip off of the design. Have had many failures come through our shop. Metallurgical issues with the integrated hardened race they use at the crank pin imo. Also seen alot of the spun bushings issues as well, correctable though. What kind of cylinder temps are these diesels seeing?

Quote from: Deweysheads on January 07, 2012, 05:16:37 PM
I think my concern was more of a tolerance issue, bushing press fit, not a statement about the tapered rod design. I haven't seen any of these rods let go but I have seen bushings spin. It wouldn't be hard to bush and ream them with a little more press and premium material even with the crank in the bike on a top end.

You just nailed the big issue. Top of bushing is too thin to offer a good compression on the press fit. Lose that and the load at the bottom of the bushing could cause it to rotate. The more the power and operational rpms the engine sees the more the risk. You don't see these things in the 120r because they know better.
Ron

Quote from: jimlibo on January 07, 2012, 02:07:17 PM
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?

We all understand that the stroke vs rod length causes the connecting rods to run at an undesirable angle in a 45* engine.  Over the years of building harley engines it is always found that the front cylinder always has more wear on the minor thrust side of the cylinder than the rear cylinder does and it also runs the hottest because of the additional friction created. 

In researching the reasoning behind this, it has shown that both cylinders do run with abnormal rod angles compared to any other engines.  If you were to look at the rotation of the crankshaft when the piston is at bottom dead center on the rear cylinder and is rotating up on compression you will see that the rod angle is more in-line with the the angle of the rear cylinder.  Now look at the front cylinder and look at the angle of the rod compared to the angle of the front cylinder when it is rotating up from bottom dead center on compression.  What you are going to witness is the rod angle on the front cylinder is trying to push the piston thru the front of the front cylinder.  With this happening, it causes severe loads on the front connecting rod and failures on the front rod is more prevalent than the rear rod.  This is just the nature of the beast that we have to deal with.

If any of you have ever have the opportunity to witness a engine being run on a engine dyno you would be astounded at the amount of frictional horsepower/torque loss there is in a H-D engine.  Frictional horsepower loss in a stock engine can average around 40-50% and will increase as the cubic inches increase.  Don't get me wrong there are many other things in an engine that creates frictional horsepower/torque loss other than the pistons and cylinders, but the pistons and cylinders are where the majority of the loss is created, especially the front cylinder.

I will pull some dyno sheets and get some exact amounts of frictional horsepower/torque losses.  I will also show what g's the piston generates as it rotates directions.

Hope this helps you understand.....

Todays OEM diesels are running ~1425 peak EGT's. Our race engines can handle 1800 with short peaks to 2000! Would I recommend that to anyone for a street vehicle..... no way, but when you set a land speed record at 341 mph you push things a little.............. OK maybe a lot! One full size drag truck we have runs 5.8x in the 1/8 at 5800 lbs with 1.38 60 ft times. Not your grampa's diesel! It's fun to be at the track and the vette's, mustangs and camaro's laugh at you until you blow them off the track in a pickup truck.

As far as HD screwing up the design, well all we have to do is look at the crankshafts but it's what they can get away with.

Hot shots been around for more than a day or 2. I remember looking at their head work years ago if they are the same people. Those rods appeared shortly after the primary side bearing change in the case where the crank had enough end play that the front rods were being lost. My best guess is that it allows the wristpin end of the rod to walk easier putting less strain on the big end. Strange things happen to rods as they are running.

Just a FYI, as an example Volvos 13 liter truck engine (also used in Mack) has slipper skirt pistons, made of steel,
and using the tapered small end  concept.

One can just start to guess how tight they can fit a steel piston to a steel bore, all water cooled.

Some diesels have a two piece piston. For example the dt530. It has a steel piston that contains the rings and wrist pins, then has a separate crown made of aluminum that slides under the piston. The wrist pin holds things together.

This reply is to deathwish's comment....

Yes we are the same company as years past.  Although on your statement "Strange things happen to rods as they are running".  Please review our article on T/C Crankshaft Shifting at the link below.  It tells what happens to a crankshaft while it is running and with this big mass moving and doing what it does, it makes a person wonder what the connecting rods and pistons are doing.   

www.hotshotmotorworks.com/didja_know.htm

The dt466 and the dt530 used regular connecting rods. The replacement for them are the powdered metal tappered wrist pin rod.
Lots of engines use the powdered rods. They are fine and work well. BUT what doesn't work well is the fact that HD uses the rod as a bearing surface. They should have put races on the connecting rods.

QuoteSome diesels have a two piece piston.

Yes, I recognise this as well.
Our products at work used that concept on our 11 litre engines.

Quote from: Hot-Shot Motorworks on January 07, 2012, 08:23:10 PM
If you were to look at the rotation of the crankshaft when the piston is at bottom dead center on the rear cylinder and is rotating up on compression you will see that the rod angle is more in-line with the the angle of the rear cylinder.  Now look at the front cylinder and look at the angle of the rod compared to the angle of the front cylinder when it is rotating up from bottom dead center on compression.  What you are going to witness is the rod angle on the front cylinder is trying to push the piston thru the front of the front cylinder.

...

Hope this helps you understand.....

I'm sorry, but that really doesn't help me see what you're trying to say, which you've basically said twice the same now.  There are only three ways I can envision a functional difference between the two cylinders such as you're trying to describe:

1. The cylinder bore centerlines both pass through and intersect at and perpendicular to the crankshaft rotational centerline, both rods are the same length with wrist pins set at same height and with same offset in pistons (same working length), but gravity appreciably pulls the pistons/rods toward the ground, through the rear of the rear cylinder and the front of the front cylinder.

2. The cylinder bore centerlines both pass through the crankshaft centerline, the effects of gravity on the pistons/rods is inconsequential, but the rods have different working lengths and/or wrist pins are set differently in the two pistons.

3. Both rods have the same working length/etc., gravity difference is inconsequential, but the intersection of the cylinder bore centerlines is not located at the crankshaft rotational centerline.

At any rate, so long as the connecting rod centers are the same measurement front/rear and the cylinder bores' centers both intersect at the crankshaft rotational center (at 90° to the bore centerlines) and both pistons have the same pin locations, I don't see how the "rod angle" is going to be any different between the two cylinders.  Please try to explain things a little better/differently for me.  Thanks.

I understand the MOCO has gone to no bushing, isn't that true? During what MY did that happen? What are your opinions on that setup VS the version with the bronze bushing.
I bring no bias to the table and I am trending toward thinking the new rods are not as bad as they are said to be.

Harley did go to a bushing less rod a couple years ago. It was discussed on here. Someone here posted the dealer handouts from the annual meeting that showed all of the changes for that year.

I was chatting with Reggie @ R&R and he mentioned the non- bushing rod change happened late 2006.

From an engineering point of view a tapered rod is probably  an advance over a standard rod.  My VW diesel is 1900 cc. Over 275 pounds of torque, 400 lbs ccp, and tapered rods. I regularily turn it to 5500 rpm and no problems in over 150 thou miles. On the other hand my SE Jims 4 3/8 crank has I beams, was loosey,goosey right out of the package,and has stood up to severe abuse for quite a few years now. Rocket science technology is great, but when translated into our beloved big twins not sure how much practical advantage we see. Going to put a bigger turbo,run an additional 8 lbs boost on the VW and see how those rods like that.

Joel 2001 FLHT

Just annectdotal but, my diesel pick up(02 Ford 7.3) has the tapered end powdered metal rods, it's pushing 500hp/900ft.lbs. and has held together for 10 years. But I'm about at the limit for pm rods, over 500 hp and they come apart. Seen this personally several times.

Glens....It is difficult to describe without having illustrations of how the rod angles are in an engine.  The next time you have an opportunity to examine a disassembled engine watch the rod angles in relationship to each cylinder and you should be able to understand what I am saying.  The highest load on the front cylinder happens on the compression stroke and the highest load on the rear cylinder happens on the power stroke.  Hope this helps....

How many degrees difference is there?

Its ok to have 500 plus horse and 900 ft pounds with a stout connecting rod. The problem is when you have a twig of a connecting rod with 140 horse and 160 ft pounds.
BTW I have a 2009 and my connecting rod is bushed.

"always found that the front cylinder always has more wear on the minor thrust side of the cylinder than the rear cylinder does and it also runs the hottest because of the additional friction created."

I've always maintained the front cyl. runs hotter than the rear, but many here disagreed with me when I stated it a few years ago. Their thinking is it gets more air than the rear. Hotshots explanation of the rotation of the crankshaft when the piston is at BDC makes a lot of sense to me.

Also, that same rotation pulls oil to the rear..does it not?
Sorry for taking this a bit off "track"