2nd Gen Non-Engine/Transmission Cod Rod Picture

[vciesielski]

duramax con rod pic

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[diesel DOG]

Why is the end cap on the Cummins offset?

 

[rbattelle]

I have always theorized that it's done like that so the rod can be removed through the cylinder bore without the need to drop the crank. It's done like that on many extremely large engines. It's good connecting rod practice to maximize the crankpin diameter.

 

[richardcoxid]

I personally believe that the reason for the canted rod-bearing cap has to do with the angle of the forces exerted by the crank on the rod bearing as it rotates. This way more of the force is on the solid section of the con rod bearing and less force is being exerted on the rod/cap interface and the rod bolts. The con rod side force is greatest when the crank is at 90* from vertical (centerline of the rod journal is horizontal to the main bearing centerline), this is when the solid section of the rod bearing is absorbing the greatest amount of force.



I. E. the con rod/rod cap interface, when bolted together is not as strong as the solid section of the rod.



I am not an engineer so maybe a mechanical engineer could explain it better, or maybe I am all wet and there is another reason. Please correct me if I am wrong! Maybe a sketch would help explain it.



By the way most inline six-cylinder engines including our 5. 9 has 7 main bearings. A front main bearing, a main bearing between each connecting rod journal and then a rear main for a total of 7.



On a V-8 the connecting rods are paired (two rods on the same crank journal) together for a total of four-connecting rod journals. So they have a front main, two rods, a main bearing, two rods, a main bearing, two rods, a main bearing, two rods, and then a rear main bearing for a total of 5 main bearings.

 

[rbattelle]

Richard,



I used to believe that was the case as well, but then I looked at the physics of it all, and it doesn't make any sense. Since the connecting rod is hinged on both ends, it cannot transmit any load that is not directly along it's center axis. Therefore, there is no way there is any significant side-loading on the rod, no matter what position the crank is. What I'm saying is, the load ALWAYS transmits directly along an axis passing through the center of the wrist pin and crank pin.



If I'm wrong, someone smarter than me will correct me. But it will take a very strong argument to make me believe there is ever any off-axis load on a connecting rod!

 

[JoeBioDiesel]

I was told by a Dodge trainer, at a Dodge Cummins "Engine Mechanical" class that it was so the rod can be removed. We had one apart, and the cap does not fit down the bore if it is completely sideways... so that's probably one of the reasons.



BTW, Cool Class!! It was then that I decided I needed a Cummins powered truck.



Joe

 

[DJb]

This is a very imformative AND funny thread lol. Lets see, I'm not positive of the numbers but, at what rpm is the most torque produced between all of the engines? IIRC, the Cummins makes it best torque numbers at the lowest rpm of all of them?

 

[fkovalski]

So... . this picture of the connecting rods is being discussed on another site. I posted the photos and they are calling BS on me. Saying the photo has been aroun the 'net and it is a haox. I have never seen all 3 in person. CAn someone provide irrefutable evidence of the photo?

 

[Cummins Pilot]

When I was a PSD guy we saw the same pic and some said it was doctored. I've never seen anything that said it wasn't real. Due to the design of the V versus the Inline I'd say the pic is correct.

 

[Mike Ellis]

So... . this picture of the connecting rods is being discussed on another site. I posted the photos and they are calling BS on me. Saying the photo has been aroun the 'net and it is a haox. I have never seen all 3 in person. CAn someone provide irrefutable evidence of the photo?

I don't have evidence of the photo, but the specs on the different engine's bore and stroke are easily accessible on the web. The Cummins has 6 cylinders versus the competitions' 8, but with similar horsepower and torque levels. Each cylinder is pumping out more pow-uh than the equivalent cylinder on an V8, and accordingly a stout rod is required. A longer stroke requires a longer rod, and a more powerful stroke requires a beefier rod. To satisfy both requirements you must have a long, beefy rod.



The disgruntlement the rod picture evokes in the hearts of Powerstroke and Duramax fans everywhere is simply envy, they are ashamed to be seen in the shower when the mighty Cummins goes strolling by :-laf :-laf



******

http://www.meadowlandford.com/2003 Power Train Specs.htm

6. 0 Powerstroke

bore x stroke = 3. 74 x 4. 13

displacement = 363 (5954)

Compression ratio = 17:1



http://www.fordf150.net/specs/02fsuper.htm

7. 3 Powerstroke

bore x stroke = 4. 11 x 4. 18

displacement = 444 (7277)

Compression ratio = 17. 5:1



http://www.truckinweb.com/brandpages/chevy/0508tr_dura/

Duramax

bore x stroke = 4. 06 x 3. 9

displacement = 403 / 6599

Compression ratio = 16. 8:1



and, to avoid claims of bias from the Ford folk:

http://www.meadowlandford.com/ford-f650-f750-cummins-engine-spec.htm

Cummins 5. 9

bore x stroke = 4. 02 x 4. 72 in

displacement = 359 cu in, 5883 cc

Compression ratio = 16. 5:1

 

[MRaynor]

That was good. I had tears in my eyes from laughing, even my wife was rolling. She is a good woman. Now when a Ford goes by she says it is a "powerjoke" or a duramax goes by she says "durajunk". I guess she knows quality too. She drove the Cummins for the first time the other morning to take our son to school. When she got back I asked how she liked it and she got a big smile and said " that truck is sweet". Looks like I will be trading in the 1500 for another Cummins. Going to wait awhile though. Forgot to mention in the center of my back window it says SIZE MATTERS, it does get attention. Sorry to ramble.

I don't have evidence of the photo, but the specs on the different engine's bore and stroke are easily accessible on the web. The Cummins has 6 cylinders versus the competitions' 8, but with similar horsepower and torque levels. Each cylinder is pumping out more pow-uh than the equivalent cylinder on an V8, and accordingly a stout rod is required. A longer stroke requires a longer rod, and a more powerful stroke requires a beefier rod. To satisfy both requirements you must have a long, beefy rod.



The disgruntlement the rod picture evokes in the hearts of Powerstroke and Duramax fans everywhere is simply envy, they are ashamed to be seen in the shower when the mighty Cummins goes strolling by :-laf :-laf



******

http://www.meadowlandford.com/2003 Power Train Specs.htm

6. 0 Powerstroke

bore x stroke = 3. 74 x 4. 13

displacement = 363 (5954)

Compression ratio = 17:1



http://www.fordf150.net/specs/02fsuper.htm

7. 3 Powerstroke

bore x stroke = 4. 11 x 4. 18

displacement = 444 (7277)

Compression ratio = 17. 5:1



http://www.truckinweb.com/brandpages/chevy/0508tr_dura/

Duramax

bore x stroke = 4. 06 x 3. 9

displacement = 403 / 6599

Compression ratio = 16. 8:1



and, to avoid claims of bias from the Ford folk:

http://www.meadowlandford.com/ford-f650-f750-cummins-engine-spec.htm

Cummins 5. 9

bore x stroke = 4. 02 x 4. 72 in

displacement = 359 cu in, 5883 cc

Compression ratio = 16. 5:1

 

[rbattelle]

That picture sealed the deal for me 5 years ago when I decided to buy a Cummins. Great picture. I now have one of the rods from our engine on my desk at work. It is the same one that's in the picture above. So we know that the Cummins rod in the picture is absolutely undoctored. I don't know about the other 2 rods, but I've never read anything to indicate they are doctored in any way.



It is funny how the DMax and Ford guys get all squeemish around that picture, and are quick to point out the key design differences that drove the differences in the rods.



-Ryan

 

[SnoKing]

http://mysite.verizon.net/res6pseo/id3.html Snoking

 

[REFLOYD]

i have benn into a 6. 2/6. 5 gm and that is the con rod that is in them, the Cummins is the one posted as for the POS oops I meen PSD i have no clue and really dont care. they dont last long enough for me to worry bout them

 

[Vaughn MacKenzie]

So... . this picture of the connecting rods is being discussed on another site. I posted the photos and they are calling BS on me. Saying the photo has been aroun the 'net and it is a haox. I have never seen all 3 in person. CAn someone provide irrefutable evidence of the photo?

Yes I think that photo on Page 2 of this thread is a Photoshop job. Here is a fairly recent photo (from '04 I think) of the 3 diesel rods. As you can see the PSD rod is also canted, and I'd say it looks pretty beefy too. But remember it's thinner than the CTD rod because it has to share a crank throw with another rod. Also notice the Cummins HPCR rod was redesigned & looks a little different than the 24v rod.