Rockers

[Peter Holmes]

There seems to be some concern from very competent engineers that visit this forum over the safeness of the locking rocker feed bolt, the concern seems to be that any metal that is removed from the rocker arm (ET25-MOD) to accommodate the female threaded component could weaken the arm and I presume lead to a breakage of the arm.
Now to someone like myself that has zero engineering expertise this concern seems irrational and without any foundation, but has anyone suffered a breakage of the rocker arm due to removing the very small amount of metal that is required for clearance, I have ridden with them in situ for years without a problem, but granted I do not thrash the engine. I just wondered whether there was an alternative view from other very competent engineers that this mod is perfectly safe, especially as they are readily available from the spares club, I would assume that they consider them to be perfectly safe to install.

 

[Vincent Brake]

well, i wont be the messenger...
as they are mostly killed

 

[Peter Holmes]

Welcome back Vincent, I missed you!

 

[stu spalding]

There seems to be some concern from very competent engineers that visit this forum over the safeness of the locking rocker feed bolt, the concern seems to be that any metal that is removed from the rocker arm (ET25-MOD) to accommodate the female threaded component could weaken the arm and I presume lead to a breakage of the arm.
Now to someone like myself that has zero engineering expertise this concern seems irrational and without any foundation, but has anyone suffered a breakage of the rocker arm due to removing the very small amount of metal that is required for clearance, I have ridden with them in situ for years without a problem, but granted I do not thrash the engine. I just wondered whether there was an alternative view from other very competent engineers that this mod is perfectly safe, especially as they are readily available from the spares club, I would assume that they consider them to be perfectly safe to install.

Hi Peter. I've posted this pic before but here goes anyway, the rear rocker has had the small amount of metal removed to clear the feedbolt nut. The front one was modified by one of the world's top Vincent men and has done many thousands of miles without failure although I always felt that too much metal had been removed. Subsequent checking revealed that it allowed for 1.25" of valve travel, totally unnecessary. I hope this sets your mind at rest over weak rockers. Cheers, Stu.

 

[passenger0_0]

Interesting. Rather than failure through fracture it's more likely that excessive elastic flexing is the real issue although modest cam profiles used in Vincents probably mean this also is not a problem.
Easy enough to analyze however why bother unless failure is common?

 

[Bill Thomas]

How much movement must also depend on how deep the valve seat is cut/worn,
So there is no set measure ?.

And somehow this is under the "A" section ?.

 

[vibrac]

I have had them since they were a mod in MPH used them in all my racers even when we had that phase of needle rollers (bigger hole as well)

 

[Simon Dinsdale]

And somehow this is under the "A" section ?.

Now moved to the correct area.
Simon

 

[Peter Holmes]

Bill, Sorry for posting this in the wrong section, bit like my school report "should concentrate more"
Stu, You have allayed my faux fears, in reality I was not concerned in the slightest, but I was concerned that very competent engineers that post on this forum seemed to suggest that by using a part that the Club Spares Co. are selling, we are risking what could be a catastrophic mechanical failure, which seemed to me to be very unlikely, I would be very surprised if this component has not over the years been lightened and polished in the quest for power and speed. I am sure that if this part (ET25-MOD) is manufactured using the correct metallurgic specification there is heaps of excess strength built in anyway.

 

[Bill Thomas]

I weakened the last one I did a lot, And was worried, But I didn't want anything to jam up,
So you have to suck it and see .