Fin 35 Posted January 27, 2022 Share Posted January 27, 2022 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? Quote Link to comment Share on other sites More sharing options...
Martin Arnold 1 Posted January 27, 2022 Share Posted January 27, 2022 Are you saying both engines have a cracked con rod ? Amazing that should get through quality control at Saito !! Quote Link to comment Share on other sites More sharing options...
Fin 35 Posted January 27, 2022 Author Share Posted January 27, 2022 Yes, the crack is in the same position on both engines, in line with the outer radius of the crankshaft balance weight. Quote Link to comment Share on other sites More sharing options...
Alan Gorham_ Posted January 27, 2022 Share Posted January 27, 2022 Is it actually a crack? The conrod looks cast or forged rather than machined from billet, so I wonder if it is actually thicker towards the big end and the line is simply where the extra material on the casting tapers away. Quote Link to comment Share on other sites More sharing options...
Martin Arnold 1 Posted January 27, 2022 Share Posted January 27, 2022 Think you need to take one of rods out to have a closer look. Quote Link to comment Share on other sites More sharing options...
Fin 35 Posted January 27, 2022 Author Share Posted January 27, 2022 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. 1 Quote Link to comment Share on other sites More sharing options...
Alan Gorham_ Posted January 27, 2022 Share Posted January 27, 2022 I still don't think that's a crack, especially after saving the photo and zooming in. Is it untidy work? Yes! The fact that it's in exactly the same place on both rods suggests to me that it's just replicating a flaw or intentional feature in the casting tooling. 1 Quote Link to comment Share on other sites More sharing options...
Martin Arnold 1 Posted January 27, 2022 Share Posted January 27, 2022 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. Quote Link to comment Share on other sites More sharing options...
john stones 1 - Moderator Posted January 27, 2022 Share Posted January 27, 2022 If whatever it is is not stood proud, looks like a crack. Quote Link to comment Share on other sites More sharing options...
Fin 35 Posted January 27, 2022 Author Share Posted January 27, 2022 Another photo attempt... 1 Quote Link to comment Share on other sites More sharing options...
Sparks Posted January 27, 2022 Share Posted January 27, 2022 Even if it is not a crack, its certainly a stress raiser. Quote Link to comment Share on other sites More sharing options...
Fin 35 Posted January 27, 2022 Author Share Posted January 27, 2022 Stress and acid indigestion ? When I run my nail over it there's a step, high on the long face, low on the short face. Quote Link to comment Share on other sites More sharing options...
Martin Arnold 1 Posted January 27, 2022 Share Posted January 27, 2022 Looks more like a casting fault on that shot, my pals is the same !! 1 Quote Link to comment Share on other sites More sharing options...
Alan Gorham_ Posted January 27, 2022 Share Posted January 27, 2022 I did say... Quote Link to comment Share on other sites More sharing options...
Martin Arnold 1 Posted January 27, 2022 Share Posted January 27, 2022 The rods are out of stock at hobbyplastic ! Quote Link to comment Share on other sites More sharing options...
Fin 35 Posted January 27, 2022 Author Share Posted January 27, 2022 I ordered the last one today! I wonder what it will look like. Quote Link to comment Share on other sites More sharing options...
Rich Griff Posted January 27, 2022 Share Posted January 27, 2022 Wwww, that is quite deep and not good. Get in touch with Saito... If the rod fails ( a very highly probable failure point indeed ) then the engine will be wrecked/scrap. Not good quality control Mr.Saito ! I wonder what Jon from laser reckons, bet he says that scrap. Quote Link to comment Share on other sites More sharing options...
john stones 1 - Moderator Posted January 27, 2022 Share Posted January 27, 2022 That looks different, still don't like it though. ? Quote Link to comment Share on other sites More sharing options...
Paul De Tourtoulon Posted January 27, 2022 Share Posted January 27, 2022 Mine failed on my FG-30 although I was using 7% oil, I am surprised that the petrol versions aren't bushed, I made my own after finding them only available in Kangaroo land,,, Le photo is after I straightened it out to measure it,,, Your does look like a moulding fault to me,,, Quote Link to comment Share on other sites More sharing options...
Fin 35 Posted January 27, 2022 Author Share Posted January 27, 2022 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! 1 Quote Link to comment Share on other sites More sharing options...
john stones 1 - Moderator Posted January 27, 2022 Share Posted January 27, 2022 I want a prize then, it must have been stood proud to be able to sand it out. Quote Link to comment Share on other sites More sharing options...
Jon H Posted January 27, 2022 Share Posted January 27, 2022 (edited) 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 January 27, 2022 by Jon - Laser Engines Quote Link to comment Share on other sites More sharing options...
DaveB1 Posted January 27, 2022 Share Posted January 27, 2022 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') Quote Link to comment Share on other sites More sharing options...
Fin 35 Posted January 27, 2022 Author Share Posted January 27, 2022 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. 1 Quote Link to comment Share on other sites More sharing options...
Martin Arnold 1 Posted January 27, 2022 Share Posted January 27, 2022 "Martin, is your photo of another engine with this issue?" Yes Jon, that is a third engine, coincidentally he bought it BNIB last week. Having seen Fin's polishing work it does not seem to be an issue, still not a pretty thing to see on a new Saito though. Quote Link to comment Share on other sites More sharing options...
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