New member hello & APD rebuild

[Ruairidh Dunford]

   

In my experience around 50% of rods coming in to me are now cracked like this.

[Alan]

I’d agree with that. Sometimes if you catch them early enough they can be saved, but you have to remember these parts have a fatigue life and they are probably 90 years old. New cranks and rods should be regarded as an insurance policy. The last crank that I had that let go wrote off more or less every thing except the cylinder head.

[Hugh Barnes]

Thank you Ruairidh...

[Goldnrust]

Thank you everyone for the continued thoughts.

So I've dropped my crank off to be crack tested and the 37 head to be skimmed flat. Presuming all is ok everything else will get cleaned up and thrown back together and we'll see how it runs. As I see it, if it weren't for the flooding I'd have happily put some fresh oil in and gone for a drive. This is several steps better than that and so more than good enough to get me on the road. I shall hold off on any further tuning, beyond the head, for now.

In terms of the rods, I've decided to risk it. Looking at the helpful picture Ruairidh has posted, I believe my rods have been probably been cracked tested reasonably recently, as I can see the same silverish colouring on them.

   

So now I wait with fingers crossed to see if the crank is ok! Will hopefully know end of the week/early next week.

In the meantime maybe I should get back to finishing off those brakes I was avoiding!

[Dave Mann]

Here's a con rod which failed after less than 6 months, it weighs 100 KG 
  Broken connecting Rod.bmp (Size: 3.52 MB / Downloads: 63)

[GM6VXB]

Trying to get my head round what would cause the cracks in the Con rods.

Possibilities are:

Gudgion pin too large having to be forced into the hole.
Expansion of the pin with the engine running. Possibly not as the rod is bolted onto the pin.
Over tightening of the con rod bolt.
Over reving the engine. Again possibly not as this would affect the crank more than the rod.
Dubious batch of rods.
Old age.

To me, all are possibilities except over reving the engine.

Martin.

[Terrytuned]

A bit like this Alan
  crank failure.jpg (Size: 42.03 KB / Downloads: 142)

[Malcolm Parker]

That's very impressive Terry!

[Tony Griffiths]

Thank you everyone for the continued thoughts.

So I've dropped my crank off to be crack tested and the 37 head to be skimmed flat. Presuming all is ok everything else will get cleaned up and thrown back together and we'll see how it runs. As I see it, if it weren't for the flooding I'd have happily put some fresh oil in and gone for a drive. This is several steps better than that and so more than good enough to get me on the road. I shall hold off on any further tuning, beyond the head, for now.

In terms of the rods, I've decided to risk it. Looking at the helpful picture Ruairidh has posted, I believe my rods have been probably been cracked tested reasonably recently, as I can see the same silverish colouring on them.



So now I wait with fingers crossed to see if the crank is ok! Will hopefully know end of the week/early next week.

In the meantime maybe I should get back to finishing off those brakes I was avoiding!

Here's a con rod which failed after less than 6 months, it weighs 100 KG 

That looks like the one you told me about with the sharp 90-degree section at the base that burst through the crankase and narrowly missed two men.

[Dave Mann]

That's right Tony, it was one of 6 which failed wrecking the engines necessitating all the engines being taken out of service while a new rod was designed, manufactured and installed. To keep the customers power supply available containerized gen sets were air freighted out. The original rod was designed by a well known engine design company.