Commando Crankshaft Porn

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hobot said:
Ugh, there likely is a sonic way to sample a good crank or bolt then listen for a sour note in others.
Click to expand...

In older motorcycles/vintage machinery, which have the simple coathanger/bent wire type steel multicylinder cranks, hanging it from a rope then tapping it with a spoon etc and hearing it lightly ring was a good a way as crack testing as anything. If it went clunk, no good.

May not work with a big lump like a Commando crank. Split into component parts, maybe ?
Be interesting to try, compare to a known cracked example though...
The cast iron central bit would be the problem, castiron not being a good bell material, AND known to crack at the drop of a hat...
 
In older motorcycles/vintage machinery, which have the simple coathanger/bent wire type steel multicylinder cranks, hanging it from a rope then tapping it with a spoon etc and hearing it lightly ring was a good a way as crack testing as anything. If it went clunk, no good.
[/quote]

Model T Ford cranks are tested the same way, hit it and if a good one, should ring like a tuning fork!
 
Below is a nice picture of a Steve Maney 59.6mm crank shaft fitted with very short Herb Becker custom aluminum connecting rods.

Great workmanship by both Herb Becker and Steve Maney.

Commando Crankshaft Porn
 
......."Great workmanship by both Herb Becker and Steve Maney."..................man that's no lie, Dances! Thanks for posting.
 
I had to look it up, but Laverda twins started with a 180 degree crank (imitating the Honda superhawk) then changed over to a 360 degree crank more like the british twins.
 
Depositing articles on history and observation on firing order and crank offsets as applies to handling, chassis attitude accelerating and tire behavior leaning. Its a bit lengthy to take in the scope as might apply to Norton clunkers. Oh yeah might keep gryo direction effects in back of mind too.

..................................................
about reversing the crank opposite wheel spin, because it lifted front...

As Doohan explains: "After they changed the rotation the bike would lift the rear when you accelerated, so you'd have the back tire spinning and the rear would lift, making the wheelspin worse. At the same time it pushed the front down, messing up the steering". The Big Bang eradicated the voodoo purely by chance, because the extra vibration produced by the close firing order required a counter-balance shaft that damped out the gyro effect.
http://www.superbikeplanet.com/NSR500.htm
....................................................


Banging out power plays.. via Carsten S. in mc-engine list.

http://tinyurl.com/8pfgh6u
If not that much time to read in all, start at 5.1, "The math going behind".
http://www.google.de/imgres?q=crankshaf ... s:883,i:12


Scroll pg 2 & 3 to get some English sense of flywheel mass helping traction too.
http://www.pit-lane.biz/t1461p20-techni ... urs-motogp
 
If you look closely at the mating surfaces between the rod and cap you will see that they are precision serrated. I am told that this is the most robust way for an alloy cap to rod connecting surface. I have seen aluminum rod/cap assemblies with single steps, steel bushing and pins but to me the serrated surface is as close to making it into one piece as you can get.
Commando Crankshaft Porn
 
Cracked connecting rods - Interesting but not relevant for aluminum which was the subject of the picture and notes above.

There are a variety of methods to index and secure aluminum caps to aluminum rods. The serrated approach cited in the crankshaft notes above and shown in the picture below is probably the most easy to achieve for its robustness as they are straight serrations done on a knee mill (Bridgeport Vertical Mill).

Commando Crankshaft Porn


Below are pictures along the same lines for commercially manufactured rods. I can only speculate on how they set up the circular serrations. In some ways this appears better as it restrains cap to rod movement in two directions in the plane.
Commando Crankshaft Porn

Commando Crankshaft Porn


Of all the Herb Becker rods I dismantled there was never evidence of movement or metal fretting. I would not use stepped or doweled all aluminum rods for competition.
 
Those rods look very much like R&R, of which I put a set in my PR engine.
Sadly, they clash with the crankcase and are totally useless! The big-end bolt heads are the issue :(

Here's hoping yours don't have that issue!
 
the alloy cap rods looks like the kind M.A.P. Cycle Marion in Fla have sold for couple decades now and know to require case relieving as can't be as compact as steel for the fatigue load cycles. They have photo's online to view. By time the alloy caps big enough there ain't that much mass advantage over stronger steel.
 
Steel caps with aluminum rods can be the best of both worlds, primarily for dimensional stability at elevated temperatured. The do not open up as much when hot compared to aluminum. A steel cap will constrain the aluminum expansion to some degree.

The rods with the circulaur serrations are from MGP out of Colorado Springs. The rods on the Maney crankshaft are custom built by Herb Becker.
 
Dances with Shrapnel said:
Steel caps with aluminum rods can be the best of both worlds, primarily for dimensional stability at elevated temperatured. The do not open up as much when hot compared to aluminum. A steel cap will constrain the aluminum expansion to some degree.

The rods with the circulaur serrations are from MGP out of Colorado Springs. The rods on the Maney crankshaft are custom built by Herb Becker.
Click to expand...

I'm still amazed at all the really cool stuff that Herb has done. Between him and Jim Comstock there's no end to the supply of fascinating innovations for the gearheads among us. Not to mention the other forum members who pop up occasionally with new and intriguing experiments.

Ken
 
B+Bogus said:
Those rods look very much like R&R, of which I put a set in my PR engine.
Sadly, they clash with the crankcase and are totally useless! The big-end bolt heads are the issue :(

Here's hoping yours don't have that issue!
Click to expand...

Clearanace can be an issue with standard stroke Norton twins. I have heard the cases and the cam shaft are the usual culprits. Cases can be relieved a bit and I have seen it but cam shafts................

The Herb Becker connecting rods are on a 59.6mm stroke Steve Maney crankshaft so there's an abundance of clearance. Also note the rod bolts are nested into the caps providing extra aluminum section for stiffness.
 
I'm a believer in cryogenic tempering, especially cranks and cams and bearings

Norton rotary development...
Some of the detail developments are interesting to recall. For example, it was found that the forged steel rotor shaft journal diameters, which are casehardened, grew in diameter during the first few hours of use due to the high temperatures developed in these early engines. It was only after a cryogenic treatment was introduced into the production process that this problem was overcome.
Click to expand...
http://www.nortonownersclub.org/history/rotary
 
hobot said:
the alloy cap rods looks like the kind M.A.P. Cycle Marion in Fla have sold for couple decades now and know to require case relieving as can't be as compact as steel for the fatigue load cycles. They have photo's online to view. By time the alloy caps big enough there ain't that much mass advantage over stronger steel.
Click to expand...

Steve,

Thanks for the education!
The rods are a work of art and I was gutted when I found the clash. I never considered relieving the cases, so I hit the buffers.
Time to regroup and break out the Dremel again!

OK, back to the cranks - I'd placed an order with Steve Maney for a new crank before the start of the season, and he called a couple of weeks ago to say he has a batch ready.
Christmas present time, I think ;)
 
Hey B-b, thank goodness the cracked out bottom of my combat cases from rolling a steel rod cap up like chewing gum only required JBW to seal as not much a structural area so can get away with chewing it out on purpose.
 
Thanks for that Steve, its a good read! You still keep coming up with good links.
foxy
 
http://www.holdfastmac.com.au/424stroking.html

IF this link worked :? It Shows B M E P per Degree Revolution , on a Super Tigre 46 two stroke running four stroke .
Renouned for this capeability , along with other S T engines .

Point Being , the rate of rotation is NOT constant for the crankshaft . The little picture should explain , if you can find it .
 
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