Preventing Broken cranks

Heres' part of an old article about a test performed at the BSA factory to keep their cranks from breaking. The life of the crank was greatly improved by rolling a fillet radius into corner of the PTO shaft. The radius wasn't cut - it was formed under high pressure (similar to the advantages of forging). I don't remember where I found this info but I'm passing it on.


CRANK PIN ROLLING (BSA cranks)

"Next they set up one of their
special cranks, with the rolled filet radius on the
crankpin, it was subjected to the same test, buzzing away on
the vee blocks [some kind of severe vibration device],
ten minutes passed, thirty minutes and it
was still in one piece. I got tired of waiting and asked to
be informed when it broke. It did not break and after one
hour it was still good. [without the rolled radius it broke in a few minutes]
I was very impressed and so was Mr
Hopwood but the factory again did not seem interested,
perhaps they could not believe it. This rolling process
consisted of applying a ball ended tool to the radius under
high pressure in a big lathe.

A few cranks were made, some for research, some for use on
the dyno. It seemed fantastic that this simple process could
make such a difference. Many years later when I was working
for Volkwagen in the USA. I discovered that they cured a
rash of broken crankshafts on the 1965 truck engine by the
same procedure, except that they did not use a ball, but a
small roller to form the radius. It cured the problem for
Volkswagen."

Jim,

that's from Roland Pike's Autobiography, Chapter 22. It's posted at Beezagent

http://beezagent.blogspot.com/search/la ... troke%20A7

Lots of other good info there.

Ken

Yes, rolled fillets are used on nearly every diesel crank in existence. Great improvement. But I have never found anyone with the ability to do it other than the manufacturer. Jim

Anyone tried cryogenically treating some of our more failure prone components ?

If someone could do this they could make a buck and we could use our stock crank cheeks for racing. Roll both the PTO shaft and the drive side journal.

rond944 said:

Anyone tried cryogenically treating some of our more failure prone components ?

Click to expand...

Tried that with a gallon of ice cream, but I am still crazy :mrgreen:

Jean

That is why nearly all Aircraft components have radii in the corners. High stressed components have their rads. shot blasted to peen the material.
Con rods are quite often shot blasted to improved fatigue stresses, & are much less likely to form surface cracks.
I often do not trust Crankshaft regrinders, as a lot of them don't know how to properly dress the wheel so the radii are fully formed.

I thought this was specified in the service manual. It's mentioned as a warning in the NOC Commando service notes to to forget the radius when doing a re-grind. The shop I used was aware of it and was able to provide the radius.

illf8ed said:

I thought this was specified in the service manual. It's mentioned as a warning in the NOC Commando service notes to to forget the radius when doing a re-grind. The shop I used was aware of it and was able to provide the radius.

Click to expand...

Sorry...not to forget the radius. My typing seems to be getting worse.

Anyone tried cryogenic treating some of our more failure prone components ?

Click to expand...

Yes I have but only after N2 gas tempering on some chain saw blades, which I use enough to known how long to retain both edge and tension. Blades lasted 2-3x longer before dulling and no longer needed to take up chain slack till time to sharpen. Great labor savor that extended chain life too. Cost $5 a chain plus shipping.
Ms Peel had almost everything engine to tranny cryo-tempered and like that toughest tested engine in Norton history WOT unloaded over rev for seconds that disappeared the tach needle d/t bouncing off peg so hard then slammed back.
Crank ends bent enough to eat up inside of alternator stator and jerked oil pump snout in half and flattened a RH exhaust cam lobe but ran her another 2000 miles before decided time to scrap engine. It did lock up once a week later on return home idling into shed CINK!. Opened to find merely a belt pulley plate screw had shaken loose to trap against case. If had happen under power would have just smeared right past it w/o notice. Measured crank to find 1/16" off DS and 1/32" TS. 2000 hard miles later its 50% self corrected 1/32" DS 1/64" TS.
New Peel welded nitrided crank was all cryo'd prior to assembly. Norris D+ cam will follow suit soon. Various dyno tests demo better power, assumption being better thermal dimension stability and heat conduction. Main cost is the shipping and all are computer control devices so find closest shop to use. Ask first what must be done before treatment or ask me to avoid some suprises like valve seats pushed right out of head : (

I found shop that was able to salvage Peels new but bent crank, maybe they have device to compress the radius. Peels radius already formed and shot peened so don't know it further advantage to be gained.

The bad news I leave you with is that even if crankshaft does not break - the stuff connected to its ends will at some rpm point. Only non flex shaft will allow safe approach to 10K rpm and beyond. Gear cam drive would go long way to preserve TS from chain jerking and racers can remove alternator, so wait to see what that combo gets away with, by others first thank you.

illf8ed said:

I thought this was specified in the service manual. It's mentioned as a warning in the NOC Commando service notes to to forget the radius when doing a re-grind. The shop I used was aware of it and was able to provide the radius.

Click to expand...

Yes, it is very clearly specified in the service manual. The problem is that most automotive crank grinders are reluctant to dress their large (expensive) grinding wheels to the .090" radius just to do one crank, and then have to dress them back to a sharper edge for the next auto crank, reducing the diameter of the wheel. Some will do it, and some won't. The shops that commonly grind British bike cranks are usually aware of the radius requirement, but even with them, it's a good idea to make sure. I always send a copy of the page from the service manual along with the crank, just to be sure.

Ken

Steve, on our Commando motors, wouldn't we have valve float long before 10,000rpm?

Long stroke motor would be greatly exceeding the 4000 feet per minute maximum even over 7400rpm?

Seems pointless.

lcrken said:

[ The problem is that most automotive crank grinders are reluctant to dress their large (expensive) grinding wheels to the .090" radius just to do one crank, and then have to dress them back to a sharper edge for the next auto crank, reducing the diameter of the wheel. Some will do it, and some won't. The shops that commonly grind British bike cranks are usually aware of the radius requirement, but even with them, it's a good idea to make sure. I always send a copy of the page from the service manual along with the crank, just to be sure.

Ken

Click to expand...

I've seen pics on here were the auto shops have been to lazy to even remove the counter weights,leaving steps in the crank,what you have to realise is that to change a wheel just to grind 2 crank pins will take longer than the job and will actually end up costing the shop, when you change a grinding wheel it has to be dressed and reradiused ,my advise is shop around check out the shops and don't wiiiiine if you think it's a bit expensive, also check the work before you accept it, there is very little you can do on a poorly ground pin, espiecaly if they have used a small radius wheel and ground away your larger radius.

Steve, on our Commando motors, wouldn't we have valve float long before 10,000rpm?

Click to expand...

Hi&dry- I almost died the 1st week on 1st Combat-pre-Peel, decided plenty of time power to pass semi before oncoming could appear around a bend, got almost to cab when traffic appears so nailed it more to get nothing but horrible noises and dropping power in 2nd so snicked 3rd and creeped ahead and back in lane just in time. That was on factory CHO head later discovered to have inhaled some carb slide before my time, which might have added some valve stem bind in guides as it peckered chamber bent and chipped valve lips.
Few days later was on drag strip pulling mid 11's sec in 1000 ft run to 7000 w/o issue till tire fold up dumped me just past X-mas tree. Rode 'it' back160 miles staving off crush injury shock by echoing sNoton off bluff walls after dark. I'd blown the rusty mufflers off practicing take offs ya see.

On Peels OVER Rev Event I'd put on spiffed up big port CH0 head with Deer's race level valve kit, [+ lightened crank] Who know how high rev's went but way beyond any tales I've heard so far. I think the large ports caused the extra rev surge that hit so hard after 7500 it slapped my adrenalized throttle grab right back to my chest to further knock me off balance as eyes and ears popped out seeing tach needle disappear and motor too in clouds of smoke out every seam and bolt hole. 2000 miles later lifted head to find nothing at all collided nor damaged in head. Cam lobe top gone, lifter bottoms smeared away. So current kits eliminate valve float as limiting factor compared to crank flex and cam drive.
This head is now with Ken who says ready to fly after milling bottom for 920 jugs.

I've seen the light now 2x's over, don't press Norton past red line long and don't use high power in long held sweepers unless iso's tamed by rear link.
I've got two thought experimental way to way exceed 8500, one for short period by bashing flywheel on sacrificial bearing metal that first deforms like rubber then explodes in plasma burst to lower friction and shock wave flywheel back in line. I've done the figures a few years ago for speed of flywheel rim and find its in the zone of space craft reentry speeds, no solid surface bearing or liquid like oil can take it w/o loosing all electrons in orbital that chemicaly binds elements into alloys. Mostly turns into 4th and 5th phases of matter > plasma and pure electromagnetic radiance spectrum.
Air-gas bearings can not take the shock imbalance loads of vintage combusters.

2nd way is planetary gears that bear all the sling loads w/o a center bearing.
Looks silly but this geometry translates linear to rotary so pure that rods can be fixed solid to pistons or be part of pistons. Small rod end it the trick part requires forked ends in a twin.

http://woodgears.ca/gear/planetary.html

highdesert said:

Steve, on our Commando motors, wouldn't we have valve float long before 10,000rpm?

Long stroke motor would be greatly exceeding the 4000 feet per minute maximum even over 7400rpm?

Seems pointless.

Click to expand...

I'm pretty sure the valves would float in the air for a moment or two after the engine exploded at 10,000 rpm.

Ken

Yeah so did I and they did in my factory Combat before 8000.
I'd really like feedback on how the tach works and how fast Peel engine could have spun up to steady state unloaded for at least 3 sec. I don't know how fast rev'ing yoose guys race engine are but I could not snap Peels throttle to WOT and back fast enough to prevent needle zinging into redline. I had rev up contests with a number of sports bikes up Huybrusa's which I had to spot them to start at 4000 and Peel at 2000, they all go ZarroooMMM, Peel > baLTTBANG past 7000 before they got to 9000.

Fastest I ever saw tach on the road was in 2nd after snicking a high side into next hook back and had view of next turn above me no traffic so held on till 7600 before put eyes on next launch point .3 sec later. Peels tach was new then and steady reading. Last glance of speedo with tach was ~90 mph. Too fast for brakes so had to slide front and rear to let momentum crash us the right way.

Another method to judge is run your engine just up so tach needle steady on back of peg then chop throttle - how long you expect to drop into red zone and then to stop at 0? I had lots of time for many emotions and visions of destruction waiting for needle to show up, then many formed thoughts while blurry became merely fast bouncing needle, then some more time to go silent in mind and blank stare on last peg bounce then couple more seconds to stop. Shed rang another second. Smoke took 20 sec with me fanning it but then only cleared enough to see top profile still there. Hand slap back made me stumble back so my head dropped to engine level as I re-gained posture to re-gain grip, I saw things no man should ever see, worse than birth canal stretching and bulging.


I almost vomited as this was engine the Drouin meant for. I had nothing more to loose so kicked her couple times and started fine with bit loose noise sounds.
Don't know why she lost power at 5000 rpm after, Pulled like a train up to that.
It was winter so trying to disprove Kieth Code front tire steers bike theory I was running up steeps to 110 [to get down hill help,with tall screen and full lowers to use body english alone to slam Peel over repeatedly to make her straight steer hands off no throttle turns. Prior could easy push the huge shield to over 120 while I lit a cigarette in still air looking over the top couple inches. Not very streamlined. Boy I loved Peel's past accidental engine combo.

So what rpm and valve kits have yoose guys floated.

hobot- proved with rear link front tire is limiting dangerous device only meant to help rear while it can then get TF out the way and let rear do its thing.