Link Material

[ausyota]

I am about to build a triangulated 4 link set up for the rear of my Lux.
Obviously the lower links have to be super strong for when the weight of the truck comes down on them on a rock, so I am making them out of 38mm solid 4140 rod.
Now for the uppers, can I get away with just using mild steel pipe with weld in bungs to save a few bucks?
The uppers only have to deal with the torque from the diff right?

[one_waz]

gday mate, im halfway through doing this same conversion, i have used 1 1/4inch solid stainless for the lowers (was supposed to have been 4140 but should be ok i think) and 1 1/4inch seemless tube with 10mm wall with weld in bungs. I used a really good program to work out the lengths, angles etc. let me know if u want.

i would post pics but dont know how[/u]

[brad-chevlux]

pretty sure you'll find suitably walled tube will be stringer then solid bar.

[evanstaniland]

Hey one_waz could i get a copy of that program to work out link lengths.

i have solid 7000 series alloy links think 38mm OD

im planning on changing to 45mm OD links with johnny joints

Evan

[macca81]

Hey one_waz could i get a copy of that program to work out link lengths.

x2

[uninformed]

pretty sure you'll find suitably walled tube will be stringer then solid bar.

i always thought that all things being equal (material and OD) solid was stronger than hollow.....

Serg

[KiwiBacon]

pretty sure you'll find suitably walled tube will be stringer then solid bar.

i always thought that all things being equal (material and OD) solid was stronger than hollow.....

Serg

You would be correct.
Last time this topic surfaced, the denouncers of solid bar were quite vague on their reasons why.

[chimpboy]

pretty sure you'll find suitably walled tube will be stringer then solid bar.

i always thought that all things being equal (material and OD) solid was stronger than hollow.....

Serg

You would be correct.
Last time this topic surfaced, the denouncers of solid bar were quite vague on their reasons why.

Surely solid is stronger than hollow for material of equal size... Maybe it's that hollow tube is stronger on a weight-for-weight basis, and people have that confused with diameter?

[KiwiBacon]

Surely solid is stronger than hollow for material of equal size... Maybe it's that hollow tube is stronger on a weight-for-weight basis, and people have that confused with diameter?

We'll wait and see if the same people come back.
Their argument was that solid is mysteriously weaker and more brittle than a hollow.

[chimpboy]

Surely solid is stronger than hollow for material of equal size... Maybe it's that hollow tube is stronger on a weight-for-weight basis, and people have that confused with diameter?

We'll wait and see if the same people come back.
Their argument was that solid is mysteriously weaker and more brittle than a hollow.

Does it get stronger and stronger as it gets more and more hollow?

[KiwiBacon]

Surely solid is stronger than hollow for material of equal size... Maybe it's that hollow tube is stronger on a weight-for-weight basis, and people have that confused with diameter?

We'll wait and see if the same people come back.
Their argument was that solid is mysteriously weaker and more brittle than a hollow.

Does it get stronger and stronger as it gets more and more hollow?

Either that or it gets stronger and stronger as the walls get thicker. But when the hole in the middle disappears it suddenly turns to custard.

We need to produce some 50mm tube with 24.98mm wall thickness. That'd be awesomely strong.

[Tiny]

the argument has to do with surface area, although I think some may be confused. Solid is going to be stronger than hollow, granted, but heavy wall hollow will be lighter and in certain applications more than strong enough.

some people employ the same principle by using say hex instead of round

if I ever get around to linking my shit I think I will use I beams

[KiwiBacon]

the argument has to do with surface area, although I think some may be confused. Solid is going to be stronger than hollow, granted, but heavy wall hollow will be lighter and in certain applications more than strong enough.

some people employ the same principle by using say hex instead of round

Hex instead of round? Good if you need to put a spanner on it I guess.

if I ever get around to linking my shit I think I will use I beams

I posted this similarl concept on pirate last week. In jest of course.

[me3@neuralfibre.com]

The larger the diameter, the "stronger" it is WHEN THE WEIGHT IS THE SAME.

So thin wall large dia tube is stronger than thick wall small dia tube.

BUT that's the strength of the tube for bending, not for being crushed when you land on a rock. Crushing the wall is a different issue (large thin wall would be bad - eaier to crush due to thickness, and reduced radius)

I would pick the absolute largest diameter you can, with the thickest wall you can, within the weight you need.
I would prefer diameter over thickness of wall.

Solid is fine, if you can bear the weght penalty. If you can increase the dia though - do that.

Paul

[just cruizin']

to get a bit techy for a minute, it's the second moment of area that is important. Essentially when a object bends to inside of the bend is under compression and the outside under tension hence the material tensile properties are being put to work. This is what gives the tube it's strength. The inside is doing SFA to resist the bend.

So if really comes down to weight and hence dollars. If we assume a given cross sectional area. As the radius of the tube increases the thickness would decrease, there is an optimum point where the thickness is that small it starts to buckle just before that point is going to be the best (biggest raidus and small thickness) to provide resistance to bending. The problem we suffer is that we land on ours so hence the suffer external damage other then the static or plain dynamic load we apply.

So why is tube better then solid, because with solid you are paying for a lot of material which is essentially providing no strength benifit.anything over about 6mm wall thickness is getting on the extreme side.

[one_waz]

if you would like the 4 link program, just PM me your email and ill send it you

Waz

[KiwiBacon]

to get a bit techy for a minute, it's the second moment of area that is important. Essentially when a object bends to inside of the bend is under compression and the outside under tension hence the material tensile properties are being put to work. This is what gives the tube it's strength. The inside is doing SFA to resist the bend.

So if really comes down to weight and hence dollars. If we assume a given cross sectional area. As the radius of the tube increases the thickness would decrease, there is an optimum point where the thickness is that small it starts to buckle just before that point is going to be the best (biggest raidus and small thickness) to provide resistance to bending. The problem we suffer is that we land on ours so hence the suffer external damage other then the static or plain dynamic load we apply.

So why is tube better then solid, because with solid you are paying for a lot of material which is essentially providing no strength benifit.anything over about 6mm wall thickness is getting on the extreme side.

Well put.

If you want to get really anal. You can point out that as diameter gets bigger, stiffness increases faster than strength (stiffness ~d^4, strength is d^3). So if we include impact absorbtion we get to the point where links have to be a whole lot stronger because they're stiffer which makes them suffer higher impact loading.

I'd probably use RHS. Because it's easily available in stronger grades (350 and 450MPa yeild) than pipe or tube without becoming so hard it becomes difficult to weld.

[chimpboy]

I wanted to put this in perspective for myself so I did some rough calculations. Assuming the same type of steel...

75mm drainpipe (assuming a wall thickness of 0.7mm), like ordinary zincalume pipe is roughly equivalent in weight to...

10mm solid round bar.

So if you picture those in your head, I think it's pretty clear which one is more rigid and "stronger", but also which one would survive a whack without taking any damage.

For even more visualisation, imagine 75mm solid round bar compared to the drainpipe... faaaaaarking heavy but anyone who thinks the drain pipe is stronger is crazy.

[ausyota]

I'd probably use RHS. Because it's easily available in stronger grades (350 and 450MPa yeild) than pipe or tube without becoming so hard it becomes difficult to weld.

Interesting that you say that.
One of the guys localy here in WA is going to use square hollow section to make his links.
I thought yeah why not, he reckons all the cool kids are going to laugh at him

[KiwiBacon]

I'd probably use RHS. Because it's easily available in stronger grades (350 and 450MPa yeild) than pipe or tube without becoming so hard it becomes difficult to weld.

Interesting that you say that.
One of the guys localy here in WA is going to use square hollow section to make his links.
I thought yeah why not, he reckons all the cool kids are going to laugh at him

Sounds like you've found a guy worth listening to.

[ISUZUROVER]

I'd probably use RHS. Because it's easily available in stronger grades (350 and 450MPa yeild) than pipe or tube without becoming so hard it becomes difficult to weld.

Interesting that you say that.
One of the guys localy here in WA is going to use square hollow section to make his links.
I thought yeah why not, he reckons all the cool kids are going to laugh at him

DOM tube is available in 450Mpa + and is weldable.

If I remember rightly, you get about a 30% increase in mass using SHS (compared to pipe with the same diameter and wall thickness as the SHS). However SHS is stiffer, which is a bonus, but what about torsional strength?

[me3@neuralfibre.com]

I wanted to put this in perspective for myself so I did some rough calculations. Assuming the same type of steel...

75mm drainpipe (assuming a wall thickness of 0.7mm), like ordinary zincalume pipe is roughly equivalent in weight to...

10mm solid round bar.

So if you picture those in your head, I think it's pretty clear which one is more rigid and "stronger", but also which one would survive a whack without taking any damage.

For even more visualisation, imagine 75mm solid round bar compared to the drainpipe... faaaaaarking heavy but anyone who thinks the drain pipe is stronger is crazy.

OK - I'm crazy.

Take that pipe, and support it properly (you chose a VERY thin wall, so it needs a large support).

Now extend it as a 6m length.

They weigh the same.

Betchya the 10mm rod bends MUCH more than the pipe.

The pipe is "stiffer" than the rod.

But I think you may have gone too far one way.

Think of this example. I have racks on my ute - 2.5" press bend exhaust pipe. They'll hold a lot of weight, I've had 200 KG up there and they'll do a lot more than that.

Take the same weight in RHS, and you end up with 1" tube with 3mm wall. I wouldn't want to put 200KG on 1" RHS racks then brake hard.

Exhaust pipe is a great example of light, strong tube with a good wall / diameter ratio.
It's VERY strong in compression.

Paul

[chimpboy]

Now extend it as a 6m length.

They weigh the same.

Betchya the 10mm rod bends MUCH more than the pipe.

I agree, that is what I was trying to say. To me it's obvious that the 10mm is much more bendy.

The last bit, I was talking about 75mm drain pipe vs 75mm solid.

[v840]

I'd probably use RHS. Because it's easily available in stronger grades (350 and 450MPa yeild) than pipe or tube without becoming so hard it becomes difficult to weld.

Interesting that you say that.
One of the guys localy here in WA is going to use square hollow section to make his links.
I thought yeah why not, he reckons all the cool kids are going to laugh at him

Got a couple of lengths of 50x50x4 sitting in my garage waiting to become my lowers. Cheap easy and strong as all get out, well, at least under a zook. From what I understand, it's a lot harder to bend/kink than tube too.

[zukesloveformud]

One other good thing about SHS is if you run it on edge i.e with the one corner down and one corner up, it will be allot more dent and kink resistant. Also when it comes to sold vs tube it is a balance. Solid bar kilo for kilo is no where near as strong as tube, but as said before tube can be dented easier, the trick is to find the happy medium. One other way is to stitch a web along the length of the link.
Jim

[ausyota]

So anyway back to my original question...
I have my lowers (which have to handle impacts) sorted.
Will 32NB medium wall with weld in bungs in the ends be strong enough for the uppers?
I could go to 40NB but the bungs are 1 1/2" so to get a decent fit in 40NB I would need to go heavy wall (may not be a bad thing).
The local steel shop only has medium wall pipe in stock

[KiwiBacon]

So anyway back to my original question...
I have my lowers (which have to handle impacts) sorted.
Will 32NB medium wall with weld in bungs in the ends be strong enough for the uppers?
I could go to 40NB but the bungs are 1 1/2" so to get a decent fit in 40NB I would need to go heavy wall (may not be a bad thing).
The local steel shop only has medium wall pipe in stock

There are two ways to answer that question.

The first is what engineers are paid to do. In depth analysis of the geometry and forces, ending with a recommendation.
The second way is to find a similar setup which has been well used and tested, then see if your links are at least as strong as those.

[Strange Rover]

So anyway back to my original question...
I have my lowers (which have to handle impacts) sorted.
Will 32NB medium wall with weld in bungs in the ends be strong enough for the uppers?
I could go to 40NB but the bungs are 1 1/2" so to get a decent fit in 40NB I would need to go heavy wall (may not be a bad thing).
The local steel shop only has medium wall pipe in stock

That will be easily strong enough.

We have used that material as upper links in many buggies and its never looked like failing...broken lots of other stuff though.

Probably the only way you would break that as an upper link is if you rolled and smacked the rear axles sideways and buckled one of the uppers.

Getting it engineered is another thing altogether though.

Sam

[80lsy gq]

i thought you told me engineers drive trains...

[ausyota]

Cheers for that Sam.
Thats what I wanted to hear, an answer from someone who has "been there, done that".
And no it does not have to be engineered