Riddle me on Shafts

ckruzer

ckruzer

Infidel
Joined
Jul 2, 2015
Location
asheville nc
Why do go-fast cars seem to uniformly have 3-4" steel or aluminum non slip shafts (slip yoke on trans)
Vs
4wd buggies sporting equal hp/torque ratings use a slip shaft with 2" tube just fine?

Setting aside "weight" savings

Does it have to do with rotating mass? The longer shaft in cars being a-typical?

Long story short. This C3 I am doing this LS/T56 Twin 67mm Turbo swap on - The trans is not slip - so to get the driveshaft out you have to either drop the diff or drop the trans. This is no bueno for ujoint replacement in the future after too much fun. So in my head Im like "Why not call up Olivers and get a 1330/1330 slip shaft made to mate the t56 slip yoke to the pinion yoke? and go have fun? Im not racing and counting every Lb for a #trackday

Thoughts? Is a slip yoke + slip shaft no bueno? Is the issue more so the age of this vehicle - in noting that the slip yoke currently on the OE trans is fully seated when using an OE shaft? My understading is that a slip yoke is not fully seated on install but greater than 50% spline engagement - allowing for movement both directions: and this is key for removing the driveshaft and slipping it in further to allow dshaft removal?

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ckruzer said:
Does it have to do with rotating mass?
Click to expand...
Yes. Critical velocity etc.

from MW website :
"Most important is the Critical Speed. Essentially, any rotating shaft will reach a point where it will become dynamically unstable. This leads to a “whipping” or “jump-rope” effect that causes violent vibration and ultimately leads to driveshaft failure. Critical Speed is a function of the shaft’s length, material stiffness and tubing diameter. Shorter shafts, made of stronger material, and having a larger diameter account for the highest Critical Speed potential. For example, 52" long driveshaft made of 3" diameter mild steel will have a Critical Speed rating of 6,322 RPM. Make it from 3-1/2" o.d. tubing and it’ll go to 7,322 RPM, and with big 4" o.d. tubing 8,246 RPM is possible. Similar variations are reflected in various diameter 4130 steel, 6061 aluminum and MMC (Composite Aluminum Tubing) aluminum shafts. The absolute highest critical speed ratings are for carbon fiber shafts, typically found only in cars that buzz through the lights in excess of 10,000 RPM."

ckruzer said:
Thoughts? Is a slip yoke + slip shaft no bueno?
Click to expand...
No bueno.
 
Bebop said:
Yes. Critical velocity etc.


No bueno.
Click to expand...

Is the issue more so the age of this vehicle - in noting that the slip yoke currently on the OE trans is fully seated when using an OE shaft? My understading is that a slip yoke is not fully seated on install but greater than 50% spline engagement - allowing for movement both directions: and this is key for removing the driveshaft and slipping it in further to allow dshaft removal?
 
ckruzer said:
Is the issue more so the age of this vehicle - in noting that the slip yoke currently on the OE trans is fully seated when using an OE shaft? My understading is that a slip yoke is not fully seated on install but greater than 50% spline engagement - allowing for movement both directions: and this is key for removing the driveshaft and slipping it in further to allow dshaft removal?
Click to expand...
Should be the case, yeah.

You don't want it bottomed out and applying pressure on the trans output.

I added info on Critical Speed in post above.
 
Bebop said:
Should be the case, yeah.

You don't want it bottomed out and applying pressure on the trans output.

I added info on Critical Speed in post above.
Click to expand...

It does appear fully seated stock (common complaint in the c3 forums)
Ill give a harder wack and see if it moves

On previous yokes pre SYE, Id seat the yoke and pull out 1in then send off the measurement from there for a driveshaft build quote
 
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