Outer Limits 4x4 Board

I need a reasonably small OD drive shaft to clear the transmission oil pan, but having bent 2 now whats stronger tube or solid bar ?

It is a front shaft so as long as balance is close it will be ok

I had the same problem with a jeep I'm working on now , 350 chev auto , we put dana diffs in which moved the pinion to the drivers side and reversed the shaft so slipjoint was at top , the bigger trucks are running solid so maybe a chromemoly one would suit your application. Glen Dobbin at Dobbin Engineering make them for any application , so I guess solid would be stronger if your not worried about weight , I suppose they are breaking them cause there hitting on the transmission , Cheers Paul.

I think for short lengths, solid is fine, just harder to balance.

The shaft is about 1 meter in length

Mart in my case it was just tagging the corner of the bash plate under full flex

On a ramp it would clear but as your climbing a rock and fully flexed it would move the axle just enough to tag the corner. I have taken an extra 40mm out of the slot in the plate to that problem should be fixed now. I also found broken transmission mount so that would have compounded the movement.

Personally I would just go with a thick wall shaft, not solid bar.

Also If you happen to land on a xxxxxhd tailshaft it would be more likley to bust the alloy tcase housing. Just a thought.

heavy walled tube can transmit more torque for a given mass- do the maths!

If you're restricted to a certain diameter for clearance, then solid is always going to be strongest.

But you gain very little strength from the solid centre, heavy wall tube will give up a more weight than strength.

Why not shorten the existing tube, but cutting it down, and insert the thin solid for the part that has the clearance issue. This will equal half tube, half solid.

The end result will be your problem fixed with an easy to balance shaft.

Current tube is 31.8 OD 3.2 WT

Looking at the blackwoods catalouge that is the thickest wt for 31.8 OD and the next size up is 35 OD which will have clearence issues with the pan

The also have hollow bar in 32OD 20ID (my my calcs a WT 6mm) or 32OD 16 ID (8mm WT) would this be a better option than tube ?

The other option I was going to check was hydrolic pipe ??

Sandvik have an excellent range of hollow bar over the ditch. Check them out.

if your that close that 5mm is going to pose a clearance issue id suggest perhapse lifting the box and transfer up a little bit or lowering your bumpstops a little as 5mm is not enough clearance for a drive shaft even 20mm is pushing it.
think about it this way you break a box mount and it will move that much. or you break a shaft and ther is no chance you transmission is going to live thru it.
also if you make the shaft too strong all you will do is break diff pinnions and transfers.

i totally agree with strenghtening the shaft but i recon there is another probem that needs addressing first.

ps tube is stronger than solid

On my Landy, the slip joint is placed where it would have contacted a crossmember. Perhaps that may be an option? Long slips even?

Pics would help , Cheers Paul.

AussieCJ7 wrote:Current tube is 31.8 OD 3.2 WT

Looking at the blackwoods catalouge that is the thickest wt for 31.8 OD and the next size up is 35 OD which will have clearence issues with the pan

The also have hollow bar in 32OD 20ID (my my calcs a WT 6mm) or 32OD 16 ID (8mm WT) would this be a better option than tube ?

The other option I was going to check was hydrolic pipe ??

that tube is no good for driveshafts we use tube that is made for this purpose it is high tensile cold drawn seemless made in the USA .the hollow bar would probably work ok but would be a bit heavy.the smallest tube we carry is 1 5/8 inch x .120 wall (41.3 x 3 mm) 1 1/4 x .188 wall is avialable (31.8 x 4.7 mm) but is hard to get sometimes it also comes in a .120 wall (3mm) pm if you want more info

same od diameter solid, v's hollow bar, same load on each, the solid snaps the hollow flexes a little but stays together

Ice wrote:same od diameter solid, v's hollow bar, same load on each, the solid snaps the hollow flexes a little but stays together

Oh BS.
For that to happen the solid would need to be made from pig iron.

Solid is stronger than a tube of the same diameter and same material. Always.

Ice wrote:same od diameter solid, v's hollow bar, same load on each, the solid snaps the hollow flexes a little but stays together

correcttttttttttttttttttttttt.

KiwiBacon wrote:

Ice wrote:same od diameter solid, v's hollow bar, same load on each, the solid snaps the hollow flexes a little but stays together

Oh BS.
For that to happen the solid would need to be made from pig iron.

Solid is stronger than a tube of the same diameter and same material. Always.

Care to place money on that ?

Ice wrote:

KiwiBacon wrote:

Ice wrote:same od diameter solid, v's hollow bar, same load on each, the solid snaps the hollow flexes a little but stays together

Oh BS.
For that to happen the solid would need to be made from pig iron.

Solid is stronger than a tube of the same diameter and same material. Always.

Care to place money on that ?

Yep.
Can back it up with FEA models too.

Ice wrote:same od diameter solid, v's hollow bar, same load on each, the solid snaps the hollow flexes a little but stays together

what kind of load are u talking? side load or rotational?

i really have no idea with this at all but i just can seam to get my head around it

and what kinda of material are u talking about to SNAP? most metals that we would use in this kind of application would just bend(or get dints then twist off) from a side load not snap, and if you are talking about rotational loads why are axles solid?and not just thick walled tube?

redzook wrote:

Ice wrote:same od diameter solid, v's hollow bar, same load on each, the solid snaps the hollow flexes a little but stays together

what kind of load are u talking? side load or rotational?

i really have no idea with this at all but i just can seam to get my head around it

and what kinda of material are u talking about to SNAP? most metals that we would use in this kind of application would just bend(or get dints then twist off) from a side load not snap, and if you are talking about rotational loads why are axles solid?and not just thick walled tube?

You are correct.

In addition to your common sense observations, hollow tubes can suffer local buckling and collapse.
Which is why you'll hear of hollow driveshafts being "corkscrewed".

hollow bar is stronger as it has to be distorted before it will fail, solid will shear at the centre point, axle are solid because most axle splines are rolled on not machined. If you wanted to make a drive shaft from EN36, HITUFF or similar it would be strong but for a small diameter over a long length it would get a resinance n vibrate. Remember your drive shaft is doin 2000+ rpm, the large drive shaft is for rigidity over the length.

Most modern motor bikes run hollow shafts for added strength and less weight

nastytroll wrote:axle are solid because most axle splines are rolled on not machined.

so you are saying hollow axles would be stronger then solid?

nastytroll wrote:hollow bar is stronger as it has to be distorted before it will fail, solid will shear at the centre point, axle are solid because most axle splines are rolled on not machined. If you wanted to make a drive shaft from EN36, HITUFF or similar it would be strong but for a small diameter over a long length it would get a resinance n vibrate. Remember your drive shaft is doin 2000+ rpm, the large drive shaft is for rigidity over the length.

Back to school for you. The concept of a "neutral axis" is one you need to learn.
Solid does not shear from the centrepoint, all cracks grow from the outside in. Bending, twisting it doesn't matter.

Every component has a specific natural frequency, that's completely unrelated to this discussion.

nastytroll wrote: Most modern motor bikes run hollow shafts for added strength and less weight

Weight is the only reason for the hollow shaft. Hollow is not stronger, but it can have a better strength/weight ratio.

KiwiBacon wrote:

nastytroll wrote:hollow bar is stronger as it has to be distorted before it will fail, solid will shear at the centre point, axle are solid because most axle splines are rolled on not machined. If you wanted to make a drive shaft from EN36, HITUFF or similar it would be strong but for a small diameter over a long length it would get a resinance n vibrate. Remember your drive shaft is doin 2000+ rpm, the large drive shaft is for rigidity over the length.

Back to school for you. The concept of a "neutral axis" is one you need to learn.
Solid does not shear from the centrepoint, all cracks grow from the outside in. Bending, twisting it doesn't matter.

Every component has a specific natural frequency, that's completely unrelated to this discussion.

Weight is the only reason for the hollow shaft. Hollow is not stronger, but it can have a better strength/weight ratio.

your right ,I did not explain that well. Best of luck with the drive shaft problem Aussie CJ7.

KiwiBacon I'm obviously not as educated as you but solid bar does bend easily compared to hollow bar, compress 1 side expand the other ect, so would it not be more ridgid over the same length as solid?

I know solid does not shear from the centre, but hollow bar is used in alot of high torque application where rigidity is a must.

For a drive shaft I'm assuming being a front it will be around the 1m mark long, I would think being a small diameter spinning at high rpm ( assuming it will be driven fast) would the shaft not want to shake it's self out of the vehicle? is this not the reason centre lathes have steadies?

Its been a long day, I'm not being a smart arse but curious?

nastytroll wrote: For a drive shaft I'm assuming being a front it will be around the 1m mark long, I would think being a small diameter spinning at high rpm ( assuming it will be driven fast) would the shaft not want to shake it's self out of the vehicle? is this not the reason centre lathes have steadies?

Its been a long day, I'm not being a smart arse but curious?

You are correct that a driveshaft needs enough rigidity that it doesn't begin to "whirl", basically flex enough sideways that it becomes out of balance, unstable and destroys itself.

As driveshafts get shorter they get a lot stiffer so you can get away with a smaller bar or tube for a front driveshaft than for a rear. Landrover used a basically solid driveshaft in the V8 discoveries, they had to to clear the cat converters.

web wheelers at it again, shooting your traps off when all you have done is read something on the net,

yes we are talking about rotational force here.

why arn't axels hollow ? simple cost, take a big drag car, they spend the money and drill the axels, its not a weight saving issue either

lets look at say the prop shaft on a container ship, its you guessed it HOLLOW becuase it transmits a huge load

being hollow it has some give before it corkscrews, your solid shaft has no give it just snaps

you might think your educated but you obviously have NFI, dont concern yourself though many a qualified engineer has NFI and NO practical experience in industry either


i just make the things and repair them when they go snap so what would i know ?

redzook wrote:

nastytroll wrote:axle are solid because most axle splines are rolled on not machined.

so you are saying hollow axles would be stronger then solid?

yes tim they will take more Torque before failing,

Ice wrote:web wheelers at it again, shooting your traps off when all you have done is read something on the net,

yes we are talking about rotational force here.

why arn't axels hollow ? simple cost, take a big drag car, they spend the money and drill the axels, its not a weight saving issue either

lets look at say the prop shaft on a container ship, its you guessed it HOLLOW becuase it transmits a huge load

being hollow it has some give before it corkscrews, your solid shaft has no give it just snaps

you might think your educated but you obviously have NFI, dont concern yourself though many a qualified engineer has NFI and NO practical experience in industry either


i just make the things and repair them when they go snap so what would i know ?

Think about this for a little bit.
If solid bar has no give in it and just snaps. Then how do your springs and swaybars survive?

BTW weight matters a lot to drag racers, that's why they drill axles. When you're pulling up to 5g off the line, 1kg feels like 5.

Ice wrote:web wheelers at it again, shooting your traps off when all you have done is read something on the net,

yes we are talking about rotational force here.

why arn't axels hollow ? simple cost, take a big drag car, they spend the money and drill the axels, its not a weight saving issue either

lets look at say the prop shaft on a container ship, its you guessed it HOLLOW becuase it transmits a huge load

being hollow it has some give before it corkscrews, your solid shaft has no give it just snaps

you might think your educated but you obviously have NFI, dont concern yourself though many a qualified engineer has NFI and NO practical experience in industry either


i just make the things and repair them when they go snap so what would i know ?

I was under the impression that the axles on a drag car were gun drilled to reduce rotational mass, for the same reasons they use titanium spools etc and aluminium and or carbon fibre driveshafts.

Agin the container ship theh shaft is hollow to give it allow it to have a much larger circumfrence for the same or less weight than a soild shaft that will stand up to the same numbers. if you could run a hollow bar and a solid bar of the same circumfrence the soild will beat it every time, there is simply so much more material to deform before it fails. And if you think that soild axles dont have any twist in em before they go snap .. then I am sorry old mate .. but your the one who has NFI.
(Watch an axle in a test bed some time, you will see it will twist almost a full rotation before it begins to give, usually at the area where the splines meet the drive flange) You can see that the entire shaft is twisted



One a hollow shaft has a stress riser in it, it will simply fold up at that point (Put a coke can on a hard flat surface, and gently get a kid to balance on it with on it .. it will hold them up .. touch the can gently with your finger and pull it away quick as the can folds up)

There is a good reason that most liner springs (torsion bars) at are not made hollow as they would be far to hard to engineer any other way. If you look at coil springs they are being twisted all their working lofe and are made out of heavy wire