What's this all about is it a new thing or am I just late to the party.
Open the PDF for a better view.
Open the PDF for a better view.
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Indexed segmented crankshafts
- Thread starter 56 Fregate
- Start date
You could have a straight 16. Why lust after boring straight eights 
Andrew
Andrew
I deny everything. Was just trying to broaden my knowledge base is all..
A friends DKW has a (smaller) crank like that.
Quite a few motorcycle engines in the past have a crank like this, and the few competition two strokes are still built like this. Suzuki T500 twin and GT750 triple, and all BMW motorcycles before 1969 have this feature. There are no conrod bolts as they have closed ends and are assembled with the crank pieces using roller bearings.
Hmm
As Alan said nothing new in the concept there and commonly used for motor bike engines in previous days, but the length of that shaft is out of the ordinary though, and indeed seems doubtful that it is real.
Closer to the French car scene, 2CV engines have a pressed together crankshaft with full circle big ends on the rods. So need to be pressed apart for reconditioning and new rod bearings.
Jaahn
As Alan said nothing new in the concept there and commonly used for motor bike engines in previous days, but the length of that shaft is out of the ordinary though, and indeed seems doubtful that it is real.
Closer to the French car scene, 2CV engines have a pressed together crankshaft with full circle big ends on the rods. So need to be pressed apart for reconditioning and new rod bearings.
Jaahn
It looks like a damned awful lot of extra machine work for what gain. Someone in the USA patented this idea no doubt waiting for his ship to come in.
Hmm perhaps this is why his patent ship did not come in ?? much easier to make, but hey mate did we get the firing order right or is that one out of wack ???
Big Ship = Big Crankshaft (cargo ship engine crankshaft)
Im pretty sure my old Citroen GS, Had a roller baring crank ,less friction! ,FROM THE LOOK OF THOSE GUYS THAT 12 CYLINDER ENGINE WOULD HAVE TO HAVE A STROKE OF ONLY 4 METERS ,
A very competent friend assembled his BMW crankshaft on the (tiled) kitchen floor at some scarey temperature achieved in the oven. Apparently they go together perfectly easily at the right temperature. Impressive, to me at least.
I have only pressed together single cranks and have paid for my twins to be done. One BMW R60/2 twin crank that needed hard chroming, then surface grinding a bearing seat area, I sent to a BMW crank specialist in Alabama USA. Price was good, freight was pricey. All up total, balanced, fully rebuilt with all new bearings including freight $600, new crank $1200.
Much of BMW bike engine/gearbox assembly on the pre1969 Is done through heating one part to enlarge it slightly giving a light press fit for bearings.
Much of BMW bike engine/gearbox assembly on the pre1969 Is done through heating one part to enlarge it slightly giving a light press fit for bearings.
Yes, it was a single, for a Farmobile restoration.
I think this was the option of choice (if not the only one available) in the early days of motoring. I remember an article in Classic and Sports Car about the Bugatti 35 with an eight cylinder inline engine, which apparently had a crankshaft like that. Now I imagine very easily these days the machining is easy peasy, indexing is child's play. But then it must have been a nightmare.
Oh, and by the way, the 35 had a block made from a single piece of steel. No idea how they carved it.
Oh, and by the way, the 35 had a block made from a single piece of steel. No idea how they carved it.
You will note that the illustration of this straight eight crankshaft has 9 main bearings which would suggest similar technology to the segmented crankshaft above. Also note that they didn't use counterweights in the early days.
I recall in my early apprentice days, that a colleague used to do up Honda Scamps, with a twin 360cc engine. He used to press the crank apart, I am assuming now to replace the roller bearings in the conrod bigend, as these must have been a weakness. When reassembling the crank there was lots of tapping with hammer to get the concentricity of the main bearings in axial alignment before final pressing together. Anyway he used to get them going again and sell onto people as first cars for their children. There was also a 600cc engine option as well. I suspect he got them for low cost as most people would not attempt to repair the engine with failed bearings.
When you think about it, they were probably great for a town runabout, but a 360cc engine in a 550kg, 3Mt long small car is still quite small. But it worked and was accepted at the time - early 70's.
Not relevant but.... I recall cruising a Gov't Holden in 1972 at 70 mph near Mount Gambier and being passed at high speed by a red Honda Scamp... That was the big engine one I always presumed....