ET: Engine (Twin) Shadow Engine strip

nkt267

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Not sure what advantage there is in running those pushrods, or was that what was available.........
The pushrods i was given belong to Ged Abrahams, he needed shorter rods than were available and these were what he sourced,I'm not quite sure where they came from but with the cams he has he could not get them to work..I tried them in new Maughans followers and I could not get more than about 5 degrees of movement in the cup before they jammed.
Maybe that was the same problem in the engine from the video and that's why one broke,there would have been a lot of bending action once they jammed..
 

Michael Vane-Hunt

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I very much doubt that the push rods were not installed corectly in this engine. They were assembled by John McDougal and he would have done them properly. Need to look for another reason for the broken rod.
 

Martyn Goodwin

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Non-VOC Member
I have taken a closer look and am amazed that the motor ran for more than just a moment or two before it broke those pushrods! They are definitely non-standard and clearly NOT Vincent components and not designed to be used in a Vincent motor.

Here is a close up of the end of one of the pushrods that came out of the motor - look closely and you can see the witness marks where the shaft was hitting the surround of the cup in the cam follower!
Screen Shot 03-13-18 at 12.26 PM.JPG


Now here is a photo of an original Vincent pushrod ET 43. Note how the shaft of the pushrod is 'waisted' immediately above the contact ball to ensure sufficient room for it all to move as the cam follower falls and rises on the cam.

original pushrod.jpg


Without the 'wasting' a plain ball end push rod inserted into a cam follower cup can only 'rock' around 10 degrees because of the constraint of the cup walls. The genuine part, with the 'wasting' of the shaft is able to 'rock' around 35 degrees - this means the genuine part never makes contact with the cup walls and so is never subject to bending stress, even with a high lift camshaft.

The 'wasting' of the correct ET43 pushrod shaft is also visible in the Spare Parts List, drawing MO13.

Easy fix - fit the proper parts - DO not simply reinstall the poorly designed parts that were there earlier.

Its little things like that that make a BIG difference.
 

Martyn Goodwin

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Non-VOC Member
Not the pushrods. This engine had 40 or 50 thousand miles on it. The head were rebuilt shortly before the pushrod failure. Might want to think about that.
A very lucky owner then - there is no denying the bent improvised pushrod rod or the impact witness marks on the ones that appear to be straight.
 

Bill Thomas

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I had to have that type of pushrod , To go with the somerton cams and big radius on the followers, That was all we had back in 1980, But mine had the undercut, Like John said. Cheers Bill.
 

oexing

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VOC Member
They guy who fabricated these rods had no idea - and same goes with the guy who installed them . In the picture below the three rods from left are Horex, Horex, BMW /5 series, all aluminium tubes. The fourth from left is /5 Series BMW all stainless steel. The three tubes from right are titanium - too low thermal expansion, no good . I will definitely do a run of aluminium tubes with steel ball ends as the original steel rods do not suit the all aluminium cylinder and head combo valve clearance wise when the engine gets to operating temperature.
I did quite a few sets of valve adjusters for bikes like Bonneville, Commando, SR 500 , certainly with undercut.

Vic


P1050717 kk.jpg
P1040563.JPG
 

Robert Watson

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VOC Member
AS MSVH says.

That engine ran 50 k miles on those push rods, and the owner decided it needed some head work (guides, springs etc), which was done by a non experienced person. What you don't see here is the looking down the tunnel with the rocker pulled out as I did after the failure and seeing the keeper on the lower guide unscrewed.
I have run those same rods, same springs (which got replaced with the head work) for some 80K+ miles with ZERO issues.

It is very interesting to see the speculations made from a video without any other information about the build or the background.

Enough said.....................
 
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