driveshaft length

Supershafts said:
That's a lucky break that person experienced, i got one a shop did and the shaft ripped apart, took out the exhaust, tank, diff, and locked up a wheel and with the fuel leaking all over put the truck in the wall from 85 mph and maybe lost 20 mph on the way to the wall.

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Actually, that one took out the fuel tank, exhaust, and cracked the bell housing on the allison. It wasn't anything i was involved in, but i use everytime someone wants to know why i wont build them a Steel replacement for a 2 piece or broken aluminum shaft.
 
I guess i should have gave speed. With a 72inch 4inch shaft on this truck by specs you cant go more than 100-110mph.
 
If built correctly shaft should hold up. we did a 4 door ranger with a 410 sprint car motor and auto. had 83" long single shaft never a single problem.
 
We had one of these go terribly wrong recently in my area on a Mack dump truck. The damage was brutal wish I would of took pictures of it. The owner operator thought he could change some sh*t up to save on weight... Didn't end so well for his truck and his wallet.
 
SIKFORD said:
If built correctly shaft should hold up. we did a 4 door ranger with a 410 sprint car motor and auto. had 83" long single shaft never a single problem.
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If it doesn't go beyond the limits of the shafts ability than you can, but you just can't throw single piece shafts at everything.

I have seen cars just about cut in two, trucks with the mid section look like it got caught in a shredder and people seriously injured and needing to learn how to walk all over again.

Had a kid at another shop do something similar, no idea of why and what roll length, diameter and material play and they made the shaft for his p/u and nearly killed his brother in the back seat when the shaft cut thru the body
 
SIKFORD said:
If built correctly shaft should hold up. we did a 4 door ranger with a 410 sprint car motor and auto. had 83" long single shaft never a single problem.
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Supershafts said:
If it doesn't go beyond the limits of the shafts ability than you can, but you just can't throw single piece shafts at everything.

I have seen cars just about cut in two, trucks with the mid section look like it got caught in a shredder and people seriously injured and needing to learn how to walk all over again.

Had a kid at another shop do something similar, no idea of why and what roll length, diameter and material play and they made the shaft for his p/u and nearly killed his brother in the back seat when the shaft cut thru the body
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In any 2 piece to single piece driveshaft thread on any forum ive ever been on. There is always some guy with some claim of some driveshaft that the laws of physics and critical speed limitations dont apply to. :bang
 
1pieceatatime. said:
In any 2 piece to single piece driveshaft thread on any forum ive ever been on. There is always some guy with some claim of some driveshaft that the laws of physics and critical speed limitations dont apply to. :bang
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Very true, and i wonder if a ranger even has the room for a 83" shaft, even in 2x. That's only a few inches shorter than the AL above, i can't remember a ranger that used anything near that length. Some had a 2pc but they weren't near that long.
 
So if you were able to precision balance the shaft would you be able to get a longer one to survive? Or is it because of the weight/length that they begin to bow in the middle, and I can see bad things happening at that point.
 
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zstroken said:
So if you were able to precision balance the shaft would you be able to get a longer one to survive? Or is it because of the weight/length that they begin to bow in the middle, and I can see bad things happening at that point.
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No amount of balance can overcome the max operating RPM. We typically balance driveshafts down to .10 ounces or less.
 
zstroken said:
So evidently the shaft isn't true?
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Typically driveline tubing is egg shaped anywhere from .001" to .005"

Without reading the engineering literature in its entirety, i can only guess it has to do with with deflection and is based on some sort of percentage of Deflection VS diameter. I.E. if a 2" shaft and a 4" shaft have an equal amount of deflection, obviously the 2" shaft has an amount of deflection that is a greater percentage of the diameter than the 4" shaft. And obviously the longer it is between centers, the greater the deflection will be.
 
zstroken said:
So if you were able to precision balance the shaft would you be able to get a longer one to survive? Or is it because of the weight/length that they begin to bow in the middle, and I can see bad things happening at that point.
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Weight is the main issue and why you don't see steel making longer than 70" runs in one piece.
The same diameter in stl that is done at say 3000 rpm, AL will usually go an additional 800 to 1000 rpm more where CF will go usually any additional 2500 rpm

We could put any tube at any length, when it gets to a certain rpm the weight of that shaft and its diameter causes it to, lets use the term flutter, if you were able to watch the shaft under a high speed cam as it gets to that critical speed where the weight is to much for that diameter at that speed the shaft will appear as if its like a rope material and it'll look like its waving and then as that is happening it is quickly weakening...

Then it goes BOOM like an explosion, then it cuts what ever each end comes in contact with.

So to not have this happen you need to know length and overall speed the vehicle is capable of, then by knowing gearing and trans one can know if you can safely use a 2", 3", 4", 5" , 6" diameter shaft to span whatever distance you need the shaft to couple the diff to the trans or t-case.

Usually a 1" change in diameter enables an additional 1200 to 2400 rpm, so what won't work in 2" may be risky at 3" but not a problem at 4".
 
Supershafts said:
Weight is the main issue and why you don't see steel making longer than 70" runs in one piece.
The same diameter in stl that is done at say 3000 rpm, AL will usually go an additional 800 to 1000 rpm more where CF will go usually any additional 2500 rpm

We could put any tube at any length, when it gets to a certain rpm the weight of that shaft and its diameter causes it to, lets use the term flutter, if you were able to watch the shaft under a high speed cam as it gets to that critical speed where the weight is to much for that diameter at that speed the shaft will appear as if its like a rope material and it'll look like its waving and then as that is happening it is quickly weakening...

Then it goes BOOM like an explosion, then it cuts what ever each end comes in contact with.

So to not have this happen you need to know length and overall speed the vehicle is capable of, then by knowing gearing and trans one can know if you can safely use a 2", 3", 4", 5" , 6" diameter shaft to span whatever distance you need the shaft to couple the diff to the trans or t-case.

Usually a 1" change in diameter enables an additional 1200 to 2400 rpm, so what won't work in 2" may be risky at 3" but not a problem at 4".
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Understood thanks.

From your explanation it isn't so much the weight, as it is the ability of a larger diameter shaft to deal with the increased centripetal forces that are because the shaft has some runout, bend, etc.
 
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zstroken said:
Understood thanks.

From your explanation it isn't so much the weight, as it is the ability of a larger diameter shaft to deal with the increased centripetal forces that are because the shaft has some runout, bend, etc.
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I think to say weight is the main issue is misleading, as a 2" .065 wall shaft is not capable of as many RPMs as a 4" diameter .065 wall shaft at the same length and obviously the 4" shaft would weigh more.
 
Ghostman said:
How do they compare to one piece. Of we could get fixed yoke output on transmission instead of slip yoke, would you build a two piece the same or with different considerations?
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You dont need a fixed yoke @ the t-case to run a 2 piece shaft. Same basic considerations apply for each piece of a multiple piece driveline with some applications having as long as a 5 piece shaft ( mostly limousines ).
 
1pieceatatime. said:
I think to say weight is the main issue is misleading, as a 2" .065 wall shaft is not capable of as many RPMs as a 4" diameter .065 wall shaft at the same length and obviously the 4" shaft would weigh more.
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Yes, I think he means the force exerted(centripetal force). Thinking of a jump rope etc. If your slightly out of round/balance, the faster you spin it the more it will be trying to look like a jump rope. A 4" shaft has more resistance to buckling, flexing than a 3" etc.
 
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