driveshaft length

Got the truck together before went to pickup the shaft up and the truck measures 70inch and i know why. The truck measured from has a 24v and 24v engine mounts. The truck i need the driveshaft for is a 12v. The 24v engine mounts sit the engine futher forward about 2inch. I believe this is to allow better access to the fuel return on the 24v head. Because i have installed a 24v engine with 12v mounts and there is hardly any room to install the fuel return so we end up using 24v mounts for more clearance since we had them.

That being said anyone anyone have a spare set of 24v engine mounts i could use a set for myself.
 
zstroken said:
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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Thats kind of where i was going with deflection and/or run out relative to percentage of diameter.
 
kjpcummins said:
Got the truck together before went to pickup the shaft up and the truck measures 70inch and i know why. The truck measured from has a 24v and 24v engine mounts. The truck i need the driveshaft for is a 12v. The 24v engine mounts sit the engine futher forward about 2inch. I believe this is to allow better access to the fuel return on the 24v head. Because i have installed a 24v engine with 12v mounts and there is hardly any room to install the fuel return so we end up using 24v mounts for more clearance since we had them.

That being said anyone anyone have a spare set of 24v engine mounts i could use a set for myself.
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I was thinking that the 24V + blocks have the 6 bolt holes, and the 12V only have the 4 bolt holes per side. Is that what your referring to?
 
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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I ask these questions below because people confuse what a 2pc shaft is.

OK are you asking how does a single piece shaft compare to a 2 piece shaft ?

Or are you asking how a slip yoke shaft compares to a shaft with a stub and slip...

A 2 pc shaft is only a shaft that is actually 2 separate shafts, divided at a u-joint coupling

Or are you asking if i would build a 2 pc shaft like i would a single, a 2pc would be planned the same way with the same requirements as a single need to be known, or some vehicles use a 2pc for poor design reasons, such as a company that modifies hummers, they fuk it up putting **** all over and then i gotta make a 2 pc that is able to clear all the nonsense they put in the way


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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Runout isn't the issue, 0.0 runout will still have a negative effect if the speed of that shafts length by diameter is exceeded.

Lets say you wanted to instal a shaft in a nascar vehicle thats shaft speed is going to be 8500 rpm and going to span on center between 45/46"
The 2' shaft would be the greatest since it will be the lightest, but it's going to do that wave like issue and rip into 2 at around 4500 rpm, so then you want to keep weight down still and find out 3" is gonna fail around 63/6500 area, 3.5" isn't all that far off, but it's still lower than 8500 rpm so then 4" has a 7/800 rpm beyond the 8500 use area.

If we made the shaft longer, those speeds of failure come in earlier, because of that issue this is why there are 2 pc shafts.

Sometimes there are 2 pc shafts because splitting the shaft into 2 you can use smaller shaft diameters and you can stuff more stuff into a single area... and have a smooth aero effective floor, see mercedes, bmw, porsche and other euro cars for that style of thinking.

.
 
Supershafts said:
I ask these questions below because people confuse what a 2pc shaft is.

OK are you asking how does a single piece shaft compare to a 2 piece shaft ?

Or are you asking how a slip yoke shaft compares to a shaft with a stub and slip...

A 2 pc shaft is only a shaft that is actually 2 separate shafts, divided at a u-joint coupling

Or are you asking if i would build a 2 pc shaft like i would a single, a 2pc would be planned the same way with the same requirements as a single need to be known, or some vehicles use a 2pc for poor design reasons, such as a company that modifies hummers, they fuk it up putting **** all over and then i gotta make a 2 pc that is able to clear all the nonsense they put in the way




Runout isn't the issue, 0.0 runout will still have a negative effect if the speed of that shafts length by diameter is exceeded.

Lets say you wanted to instal a shaft in a nascar vehicle thats shaft speed is going to be 8500 rpm and going to span on center between 45/46"
The 2' shaft would be the greatest since it will be the lightest, but it's going to do that wave like issue and rip into 2 at around 4500 rpm, so then you want to keep weight down still and find out 3" is gonna fail around 63/6500 area, 3.5" isn't all that far off, but it's still lower than 8500 rpm so then 4" has a 7/800 rpm beyond the 8500 use area.

If we made the shaft longer, those speeds of failure come in earlier, because of that issue this is why there are 2 pc shafts.

Sometimes there are 2 pc shafts because splitting the shaft into 2 you can use smaller shaft diameters and you can stuff more stuff into a single area... and have a smooth aero effective floor, see mercedes, bmw, porsche and other euro cars for that style of thinking.

.
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I don't understand the physics behind how a perfectly balanced shaft will go into start waving at certain RPM unless there is something that allows forces to act on a certain part of the shaft. IE there is something that is acting off the centerline.
 
zstroken said:
I don't understand the physics behind how a perfectly balanced shaft will go into start waving at certain RPM unless there is something that allows forces to act on a certain part of the shaft. IE there is something that is acting off the centerline.
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Next time you get the chance, ask your old lady what happens when the shaft goes too fast.
 
As speed increases for a shaft the length of its mass becomes to heavy at the center and will start to deform as it fails it's ability to hold it's rigidity and form from going to fast it creates heat fatigue, that fatigue then causes the failure which having a 40/50 lb shaft come apart at 4500 rpm is deadly...

Example take 40 lbs and put it on a 6' rope and spin around as fast as you can, or have a friend spin you on a kids playground spinner.
You're gonna find your arms won't be able to hold it at 6' as they will at 4' and 2'.

Everything that spins has a speed where its weight acts on itself and kind of increases it's weight, cranks flex crack and break, flywheels explode, tires come apart....

Watch a fuel cars tire in slow mo and see it's far from round, shafts do the same thing when they reach a speed there length is exceeded they deform and break.

.
 
I was talking about fixed yoke shafts vs slip yoke shafts. Fixed yoke shafts obviously have to have a male/female splines ends and are in two pieces. Just wondering if there is any preference between the two. Similar to the front shaft.
 
For 1 pc apps you're better with slip yokes than the stub slip, and it's also extremely cheaper.

The only time a end yoke is better is if you're doing extreme off-roading and if you rip the rear shaft apart you don't lose the t-case oil/fluid if you lose the slip yoke.
Otherwise it is a heavier performance robbing shaft.
 
Supershafts said:
For 1 pc apps you're better with slip yokes than the stub slip, and it's also extremely cheaper.

The only time a end yoke is better is if you're doing extreme off-roading and if you rip the rear shaft apart you don't lose the t-case oil/fluid if you lose the slip yoke.
Otherwise it is a heavier performance robbing shaft.
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The trans slip style will also have a marginally higher RPM limit.
 
Supershafts said:
As speed increases for a shaft the length of its mass becomes to heavy at the center and will start to deform as it fails it's ability to hold it's rigidity and form from going to fast it creates heat fatigue, that fatigue then causes the failure which having a 40/50 lb shaft come apart at 4500 rpm is deadly...

Example take 40 lbs and put it on a 6' rope and spin around as fast as you can, or have a friend spin you on a kids playground spinner.
You're gonna find your arms won't be able to hold it at 6' as they will at 4' and 2'.

Everything that spins has a speed where its weight acts on itself and kind of increases it's weight, cranks flex crack and break, flywheels explode, tires come apart....

Watch a fuel cars tire in slow mo and see it's far from round, shafts do the same thing when they reach a speed there length is exceeded they deform and break.

.
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I don't agree with your analogy, especially since the weight piece is at a single place along circumference. Where the driveshaft it is a continuous uniform weight around the circumference, so if the shaft is perfectly balance/uniform it will have net zero force regardless of the speed as the forces will cancel. Unless there is some weight slightly off center. Then as the speed increases the force on the off center/balance piece will increase. Now the larger diameter tubing will have more of a resistance to the buckling. I hope I explained my thoughts properly. I believe you in saying the larger diameter shafts will handle the increased RPM, but I am thinking the buckling is proportional to the 4th power of the radius.
 
Supershafts said:
As speed increases for a shaft the length of its mass becomes to heavy at the center and will start to deform as it fails it's ability to hold it's rigidity and form from going to fast it creates heat fatigue, that fatigue then causes the failure which having a 40/50 lb shaft come apart at 4500 rpm is deadly...

Example take 40 lbs and put it on a 6' rope and spin around as fast as you can, or have a friend spin you on a kids playground spinner.
You're gonna find your arms won't be able to hold it at 6' as they will at 4' and 2'.

Everything that spins has a speed where its weight acts on itself and kind of increases it's weight, cranks flex crack and break, flywheels explode, tires come apart....

Watch a fuel cars tire in slow mo and see it's far from round, shafts do the same thing when they reach a speed there length is exceeded they deform and break.

.
Click to expand...

I don't agree with your analogy, especially since the weight piece is at a single place along circumference. Where the driveshaft it is a continuous uniform weight around the circumference, so if the shaft is perfectly balance/uniform it will have net zero force regardless of the speed as the forces will cancel. Unless there is some weight slightly off center. Then as the speed increases the force on the off center/balance piece will increase. Now the larger diameter tubing will have more of a resistance to the buckling. I hope I explained my thoughts properly. I believe you in saying the larger diameter shafts will handle the increased RPM, but I am thinking the buckling is proportional to the 4th power of the radius.


Your analogy actually indicates that it might be a balance issue as the buckling resistance increases faster as the radius increases than the centripetal force increases with radius.
 
It's weight, the same diameter shaft and length in thinner wall will spin faster than the heavier wall shaft of the same diameter and length.

This is why say at 50" the stl shaft fails at 6800 and the al shaft of the same diameter and length fails at 7700.
Or even closer, the 65 wall shaft fails at 7100 and the 83 wall fails at 6800, same holds true as the wall increases, the wall increase will hold more tq, but at the sacrifice of rpm... This is why we use 65 wall in nascar stuff, the 83 wall is heavier and its rpm yield is lower, and we aren't having to worry about tq since there is no 1st gear multiplied tq spikes

This is why we could put a 80" long single stl shaft in your truck for pullin only, but you'll die going down the highway, put the 80" shaft in AL and you'll be alive on the highway.
 
IIRC, the faster a given weight spins, the greater the force outward or going away from the center becomes... therefore the faster the heavier shaft spins, the more force there is pushing outward on the wall of the shaft and I suppose it begins to yield and deform and I'd imagine that's when SHTF?

And I'd imagine the length between the two ends has to come into play somehow as the center of the tube is doing double-duty trying to resist the bending forces from the weight of the shaft AND the rotational forces while spinning?
 
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6 ft is the max you want to go on a one piece make sure you have it balanced very well it's cheap to have them welded and balanced at your local heavy duty truck store I always have fleet pride do mine. It's about 6ft and feels perfect at all speeds I've only been up to 110 tho.
 
STROKETHISF350 said:
6 ft is the max you want to go on a one piece make sure you have it balanced very well it's cheap to have them welded and balanced at your local heavy duty truck store I always have fleet pride do mine. It's about 6ft and feels perfect at all speeds I've only been up to 110 tho.
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Probably better off doing them yourself in your back yard and welding them together with a coat hangar and a torch. Granted fleetpride is like walmart for truck parts so the service at each location will vary greatly. The way the one we have in town here hacks things together and over charges is great for business where i work.
 
1pieceatatime. said:
Probably better off doing them yourself in your back yard and welding them together with a coat hangar and a torch. Granted fleetpride is like walmart for truck parts so the service at each location will vary greatly. The way the one we have in town here hacks things together and over charges is great for business where i work.
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yup.
 
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