Commando rods

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dynodave

dynodave

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After many years since I first heard alledged stories about "D" connecting rods, I have finally have a set in my hands.
23258 D
Commando rods


NM23258 ?mfg symbol? R8R
Commando rods


"For safety reasons, Norvil Motorcycle Company WILL NOT rebuild any 850 engine where D-rods are found unless they are replaced with new conrods."
I was personally told additional evidence from Les E...
Any comments about this connecting ROD situation.
any truth or just fantasy?
Would you use D rods?
 
What was the actual issue supposed to be that made them ‘weak’ in the first place; dimensional error? Material error? Or what?
 
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dynodave said:
"For safety reasons, Norvil Motorcycle Company WILL NOT rebuild any 850 engine where D-rods are found unless they are replaced with new conrods."
I was personally told additional evidence from Les E...
Click to expand...

Well that could be a blessing in diguise!
 
My experience-
I rebuilt a motor for a customer a few years back that had D rods. It had over 70 K miles on it.
I gave the customer the choice of replacing them. He said "no, he was easy on the motor "
It is still in use.

But would I put them in my motor. Probably not.
 
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Well understood, but what is the truth behind all the fear?
 
Fast Eddie said:
What was the actual issue supposed to be that made them ‘weak’ in the first place; dimensional error? Material error? Or what?
Click to expand...

From (very) vague recollection there was -allegedly - an 'invisible mould line' which was a stress raiser.
According to one expert, anyway.
 
I have plenty of D rods, but those look different to the ones I have, could it be a case of 'which D rods' Mine are still fitted at 37K on them, they looked to have been correctly forged and had no surface fatigue crazing, so back in they went.
A rod will only be week if forged incorrectly, Heat treated incorrectly or carries a stress raiser.
 
kommando said:
Les increasing sales when overstocked on rods.
Click to expand...

Seems quite unlikely to me, especially if he only balked at rebuilding engines with very rare "D" rods.

B+Bogus said:
From (very) vague recollection there was -allegedly - an 'invisible mould line' which was a stress raiser.
According to one expert, anyway.
Click to expand...

This approximates the reason I had heard...due to a two hit forging rather than a single hit on a HDA rod.
As the tale goes , smacking the rod on the bench, to show the customer, had caused the head to snap off. Not a rod that I would want in my engine.
Less than a scientific story, but I might sacrifice a few rods to try and verify the truth...nobody else seems to be as curious as I am.


madnorton "could it be a case of 'which D rods'"

Any chance of posting a pix of each?
 
Supposedly the entire original rods were stamped one time but the D rods were stamped twice (small end and big end stamped separately). The stress riser was where the two stampings met. There are threads going back to 2007 on this but even then no one seems to have the real story.
 
This "D" rod shows 2 circled "D"s,
different from the ones on my desk, shown in my pix above.
And notice the numbers run in the opposite direction indicating a different mold/die and maybe a different manufacturing process.
Commando rods
 
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Madnorton said:
Mine are 2 D's found in MK3 Commando's.
Click to expand...
Thanks
These D rods came out of early MKIII 32536X, and it is highly unlikely the rods were ever changed.
It would be nice to know if there are good VS defective ones. More research may eventually tell.
So now the question...which are good/bad ....D..and/or... DD ?
The only rod I ever broke was NOT D or DD. It was in a stock, new, 70 Roadster, my first bike.
 
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