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Saito Cracked Conrod


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I've just removed the backplate from an un-run Saito 62B, only to find a crack all the way across the conrod to a depth about 1/4 of the thickness. I have two of these engines, both new and un-run, so I looked in the other - exactly the fault! I contacted MacGregor but they were not aware of this issue and directed me back to the supplying model shop. Has anyone else seen this in 2020 vintage Saito engines?

IMG_3723.JPG

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That was the first thing I did - disassembled one of the engines, and it looks like a crack. I was hoping it may be a casting line but its jagged and goes down each side of the rod thickness for about 1mm. New photo is not great but it gives you an idea.

Saito62B_conrod.JPG

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Have to say looks like a crack to me, obviously the motor had not run, the assembly grease is undisturbed on the first photo.

Still don't understand how they became cracked, I have two 62's but they are both the older "A" version.

Have sent a link to this to a pal of mine who has just bought a BNIB 62b will see if I can get him to drop the back plate off his and have a look.

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Thanks Paul, you inspired me to cut metal, well, file and polish it at least. First prize goes to Alan! I think I took about 0.25mm of the higher surface (although I didn't measure before/after) and then worked my way down to 1200 wet and dry and metal polish. It's not a mirror finish and there is still a slight crevice/dimple in the middle but I didn't want to push my luck.

 

Many thanks for all the comments. I don't think we will hear of many conrods snapping any time soon but they won't win any beauty contests either!

MyConrodPolished_1.JPG

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2 hours ago, Rich Griff said:

 

 

I wonder what Jon from laser reckons, bet he says that scrap.

 

Honestly, i have to wonder why anyone is dismantling a brand new engine in the first place. 

 

With that to one side, although its hard to tell from the photos exactly what is going on i wouldnt be running the engine with a rod that looked like that. I dont pretend to know what is wrong with it but MG are the importer and service agent of saito and so the buck kinda stops with them. If you go back to the shop you bought it from all they will do is send it to MG. I used to work in a model shop and that is all we did as we were not permitted to make decisions like that. It was kinda annoying actually as i got the wrong answer from a supplier regarding an engine failure (not a saito) once and was expected to convince the customer to pay up even though i knew the supplier was feeding us male bovine excrement regarding the failure. Fortunately another engine of the same type had the exact same 'in trousers poop' and we had more of a case to argue. It worked out fine in the end. 

 

If you get no joy from MG contact saito directly. A customer of mine had a saito radial that on two occasions ejected an entire cylinder off the engine. He alleged that MG were 'unable to assist', so sent it to japan and it came back magically a completely new engine. 

 

Martin, is your photo of another engine with this issue? If so there are 3 engines identified with this apparent issue from a sample size of about 5 people, on one thread on one forum...that seems rather excessive. 

 

If anyone has an NDT xray machine that would be dead handy right about now to see how deep the crack is. 

 

 

EDIT: ah, not deep at all ? 

 

 

 

 

Edited by Jon - Laser Engines
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Well spotted, but the close up photo in 'another photo attempt' post, the evidence that this 'feature' is replicated across several rods - and the ability to polish is out confirms it was never a crack, but would have been formed during the forging (or casting) of the rod and would have likely come from poorly aligned joints in the die. Conrod loading is primarily in compression, combined with some bending, and if design margins are low fatigue failures are most likely in the blends from the shank to the big / small ends, or at the ends themselves. A full on hydraulic lock can cause a rod to buckle (unlikely on a model engine) but the most typical failure mode would be a bearing / bush failure.  So although this does not look good, it is more of a cosmetic defect / feature than anything that could affect performance. 

(I used to run Conrod fatigue tests - albeit on somewhat larger displacement Diesels')  

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I didn't intend to dismantle the engine, just to remove the backplate to check for swarf. I've only started doing this recently after a bad experience with a new engine that  gouged the piston very badly on the first flick with fuel in it, but that's another story.

 

 

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