TT5.9mag
Two atmospheres are better than one
Can you explain why crankshaft manufacturers (Scat, Callies, Bryant, Manley, etc) all make cranks with multiple keyways?
Cam Phasing
- Thread starter Bodyperson
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jos51700
Green Bearing thread connoisseur
I'm not a crank engineer, but just looking at it, I'd venture that it creates fewer stress risers than a single large keyway.
TT5.9mag
Two atmospheres are better than one
Nope. It further reduces the strength of the shaft, and increases the amount of stress risers. Now why would they still do it?
jos51700
Green Bearing thread connoisseur
As I read that, the line that says "in case the key way is too long..." kindda sums up my point and even elaborates that long continuous keyways contribute to shaft twist. A long keyway cut for single sliding key is pretty detrimental strength wise, where multiple half moon key slots is a much more rigid and robust setup.
That said, I'm not a crank engineer, and if you know some other reason, share it. As I said, keys aren't designed to carry loads and the furthest I 'officially' opined on.
You're welcome to slather your crank and cam bolts in red thread locker and leave them finger tight if you want to prove to me that the key carries the load.
TT5.9mag
Two atmospheres are better than one
And you’re welcome to leave your keyways out of the crank and cam if you think they don’t carry any load.
TT5.9mag
Two atmospheres are better than one
Shaft key & keyway | Key types | Keyed Joint application & benefits
Everything you’d ever like to know about keys and keyways and how they transmit load, reduce shaft strength, and are sized per application.
Everything you’d ever like to know about keys and keyways and how they transmit load, reduce shaft strength, and are sized per application.
TT5.9mag
Two atmospheres are better than one
The reason they (crank manufacturers) sell cranks with multiple keyways is because when you drive more components from a hub or pulley, one key does not meet the requirement for strength. Supercharging is a very specific example where double keyed cranks and dampers (or hubs) are used.
Yup. Even @Coyote Jack has talked about that before.
I ran the offset Mopar performance keys to 6700rpm with 300# open spring pressure. No issues.
TT5.9mag
Two atmospheres are better than one
The strength of the crank is not of concern. It was brought up in general terms to be used as an example of how adding multiple keyways to a crank snout affects its strength.
PRH
Well-Known Member
And then there are these…….
jos51700
Green Bearing thread connoisseur
It's funny... I've seen plenty of blower drives that used bolts with no keys.... And never one that used keys with no bolts.....
Don't forget the green bearings. lol
jos51700
Green Bearing thread connoisseur
Green bearings are the foundation upon which every vehicle since the Volkswagen Beetle has been built. We owe green bearings our gratitude! Let's give green bearings a great big hand!
junkyardhero
Well-Known Member
i was there for the green bearing wars. i fought back the hoards and naysayers, driving the detractors before their wives and children and reaping their mortal souls amidst the wails; and making chariots of their bones in the aftermath.
i did this not to quell my insatiable appetite for blood lust, but so that my descendants could roll down the road freely, without the worry of weebles or wobbles in their life. it was my sacrifice to make.
i did this not to quell my insatiable appetite for blood lust, but so that my descendants could roll down the road freely, without the worry of weebles or wobbles in their life. it was my sacrifice to make.
TT5.9mag
Two atmospheres are better than one
Then youve seen a bunch of **** screwed together by morons. Bolts can carry (small) load in shear depending on the material and the fit (friction) between parts but they are designed really for carrying a load in tension and should be used as such. Keys and keyways are a much better way of mechanical power transmission.
jos51700
Green Bearing thread connoisseur
Normally I agree with you, but you're just flat wrong.
Notice: Not a keyway in sight....only bolts...
But yeah, Blower Drive Service doesn't know what they're doing.
(Hint: if the bolt is carrying load in shear, then it's lost tension for whatever reason. When a bolt is properly tensioned {a.k.a. tight}, then it sees virtually zero shear load in these applications.)
I will agree that keys can carry enough load to get the job done if you add a whole bunch of them, and call them....
splines.
TT5.9mag
Two atmospheres are better than one
I’m not wrong. I’m stating facts basically right out of text books. If the bolts stay tight, they see virtually no shear load you are correct, until the point that the force to drive the components (blower) exceeds the friction capacity of the bolted components and you get slip. Then the bolts are carrying load in shear. They get around this by adding multiple fasteners. That’s why there are 6- 3/8” bolts to hold that pulley on. And blower drive service knows what they’re doing, they sell “all crank hubs with a stock sized keyway AND a 1/4” keyway located 180 degrees from the stock one”
TT5.9mag
Two atmospheres are better than one
jos51700
Green Bearing thread connoisseur
And the crank bolt's tension is what's holding that hub in place during operation, not the keys.
Leave the crank bolt out, make a pass, and get back to me.
OR I guess I could ask....where's the key on the flywheel side? You know....the side that sees repeated shock loads and far more drive forces?
I don't need your linked website to understand this. An MS in Mechanical engineering covered it for me.
But! I'll quote your linked site for you.
"The mechanics of a bolt in tension are less complicated than for a bolt in shear. In this case there is no slip to consider. " No slip, no shear. Just like I said in post 94. I'd cite the source for you, but you already know it.
TT5.9mag
Two atmospheres are better than one
You referenced BDS saying how good they were. Yet, they make hubs with multiple keys. Why?
Never mind you don’t have to answer I’m done here.
An engineer doesn't need a degree to be called an engineer. Engineering happens all of the time. I've learned from hard knocks. I've seen sheared bolt heads implant themselves in plywood.
Lost a friend to a sheared bolt from a puller. Hit him on the head like a bullet. Definitely want those bolts tight.
Lost a friend to a sheared bolt from a puller. Hit him on the head like a bullet. Definitely want those bolts tight.
It cannot be argued that what keeps fasteners tight is bolt stretch. Pretty simple theory. While I agree the keys hold virtually zero load, they do keep something in place right where it's supposed to be.
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