Commando Crankshaft Porn

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An interesting article. A few years ago I built a Suzuki T250 for racing. I'd always believed in Japanese production engineering, however after I bought two new conrods, I decided to check their weight , end for end. The little end of one rod was much heavier than that of the other. I had a top loading laboratory balance with a piece of glass rod on the pan, a V stand beside the pan , next to a linisher and a bench grinder. So I matched their weights end for end, and polished the rods. Japanese two stroke rods are shot peened and copper plated to remove stress raisers which can cause a failure. I didn't rebalance the flywheels, however the motor was smoother than most other two strokes that I have ridden. It did not chuck a rod even after being raced for years by the next owner (also maintained). He won 28 races and 5 championships with it, and it was on methanol.
I doubt that commando rods, gudgeons and pistons would differ much when weighed end for end in assembly - however I've never looked.
 
A little something to keep my new crank warm showed up in the mail today. I will be glad to not have to worry about fatigue with my old 100,000 mile cases anymore. Jim

Commando Crankshaft Porn


Commando Crankshaft Porn


Commando Crankshaft Porn


Commando Crankshaft Porn
 
What brand are they Jim?
All shiny smooth on the outside like that, they look more like billet than cast?

Glen
 
worntorn said:
What brand are they Jim?
All shiny smooth on the outside like that, they look more like billet than cast?

Glen
Click to expand...

They are billet SBR cases from New Zealand. Now I am going to have to make a billet timing cover to match. Jim
 
worntorn said:
Strong stuff!

Glen
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And Oh So Bee U tee full :) Way jealous Jim, but hey, thanks for posting the photos of those outstanding crankcases :D I'd not heard of SBR 'til now, I love this forum !!
 
I know you have tons of work Jim but what ever happened to the Twingle????? I am really looking forward to hearing it. :wink:
 
Hortons Norton said:
I know you have tons of work Jim but what ever happened to the Twingle????? I am really looking forward to hearing it. :wink:
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Actually the engine is done and I had planned on installing it in my bike. Fear of the unknown stopped me. There were just to many unproven ideas in the motor to put it in the bike I travel around the country with.
It will run yet, probably on my dyno mount first. Jim
 
The is a guy up in Queensland making crankshafts using an NC machine. I spoke to him a while back about a billet crank for my 850. My problem is that I don't think many people have seen what is in the middle of most bar stock. His price was around $2500 - I think finding clean steel might be a problem, Australian made alloy steel is usually garbage. What do you do - find an importer and get him to cut a disc off a bar, so you can do a sulphur print ? I suppose with NC you could make it out of a slab and avoid the inclusions ?
 
acotrel said:
The is a guy up in Queensland making crankshafts using an NC machine. I spoke to him a while back about a billet crank for my 850. My problem is that I don't think many people have seen what is in the middle of most bar stock. His price was around $2500 - I think finding clean steel might be a problem, Australian made alloy steel is usually garbage. What do you do - find an importer and get him to cut a disc off a bar, so you can do a sulphur print ? I suppose with NC you could make it out of a slab and avoid the inclusions ?
Click to expand...

I have not found any inclusions in VAR steel. Jim
 
comnoz said:
A little something to keep my new crank warm showed up in the mail today. I will be glad to not have to worry about fatigue with my old 100,000 mile cases anymore. Jim

Jim,
Below the oil pump mounting boss,is that a hole for the oil return on T/S jpg?
CNN
Click to expand...
 
CanukNortonNut said:
comnoz said:
A little something to keep my new crank warm showed up in the mail today. I will be glad to not have to worry about fatigue with my old 100,000 mile cases anymore. Jim

Jim,
Below the oil pump mounting boss,is that a hole for the oil return on T/S jpg?
CNN
Click to expand...
Click to expand...

I haven't done any return oil hole yet on the cases. I think you are seeing the lower oil pump mounting hole?
I will post some pictures of the mods when I get them made. Jim
 
Jim, I take it that by VAR you mean vacuum degassed ? Or is that a brand ?
 
VAR was originally an abbreviation for Vacuum Arc Remelt, but now is commonly referred to as just Vaccum Remelt. The arc part was kind of redundant, because that's pretty much the only way steel is melted in a vacuum environment. If I recall correctly, the lump Jim used for his crankshaft was actually a double VAR, aerospace certified (I've forgotten the specification used) billet. The VAR process produces very clean alloys, and double, or even in some cases triple remelting produces exceptionally clean and homogeneous materials.

Ken
 
the steel works i work for produces triple melt which is referred to as HCM3 for jet engine shaft (which i machine) plus a number of other specialist alloys of stainless steel etc. As will as multiple heat treatment processes there are forging processess to get the correct uniform grain structure within the metal. a great deal of metal fails on its grain struture not being correct this would lead to stress failure over time.
 
To get decent material In Australia, it would have to come from elsewhere. We only make structural grades. The attitudes towards quality are a disgrace .
 
acotrel, if what you say is so about availability of suitable steel, unless one is hell bent of fabricating a crank in the homeland with the alloy steel that you must ship in, it may be more economical to have it fabricated over seas and then shipped in at say maybe 20% of the original billet mass weight.
 
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