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Which Is Stronger?


Tonk
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Tonk, the answer is bar. ;)

Tube is just stronger per unit mass, but since you are (probably) not worried about weight (unless this is part of your weight-saving plans), then go with bar.

The reasons tube is good is because all the material is a long way from the axis, which makes it very EFFICIENT in terms of 'moments of area' and its derivatives. This is why, for a given amount of material (i.e. mass), an I-beam is the best (or one of) method of supporting loads in a KNOWN direction. The more material you have as far as possible from the neutral axis, the stronger the material will be for a given mass. But this does not mean that material near the neutral axis does not contribute to strength - it does, it's just less efficient than having it further away. So to resist bending with a beam of a GIVEN MASS, then tube is best as all the material is further from the axis. But to resist bending with no mass restrictions, bar will always be stronger for a given outside diameter.

You can visualise it like moments or torques. The greater the distance from the pivot, the greater the force that can be exerted. So in terms of our bar/tube choice, you can mentally see that if your tube has a large diameter, it will need to support a lower load to resist the same bending. It's just a way of visualising the effect of the distance from the neutral axis. I hope that makes some sense.

The above explains why gun-drilled halfshafts are popular in sports cars - they can resist high loads while remaining as lightweight as possible because they move their mass (material) as far from the neutral axis as possible.

So in terms of driving something unbreakable for a small mass penalty, go with solid bar. If you are designing a Landy-based F1 car, go with tube.

Al. :)

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Tonk,

I was forever bending steering bars front and rear on the old hybrid.

In the end I bought danbars front & Rear, and WOW what a difference, also grease then up then when they hit they rotate over the obstance rather than dig in.

Trim to fit maybe ....Kieth Gotts sells them cheapish, ask JW he's always nipping up there !

Nige :ph34r:

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Streaky - I have some and I *think* they are solid bar if I remember right... Pretty beefy, I'm pretty sure they are solid.

That didn't help much, did it... :unsure:

Tonk - kind of depends what you have access to! (Quite a bit, I know...) And how much you want to spend (not much, I know...!) :ph34r::lol:

Anyway, I thought you had a steering guard!?! How did you bend the bar?

I'll have a think about materials / treaments, but if you build it fat enough (that is, put lots of material far away from the neutral axis), most things will do!

Did you see what I did there? Referring to my previous post? Just popped it in. Smoooooth huh? Now that's a quality post! :D

I know you can get bars (that is, TUBES) which slide over the regular bar and kind of 'spin' like a wheel over obstacles - not sure how effective this is...? Any thoughts?

[Oops - just pipped to the post by HFH there...]

Hope that helps. Al.

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....Kieth Gotts sells them cheapish,

First time I heard that Nige, not about the steering rods, just generally!

I've been trying to get some sumo bars from Kinglsey 4x4 but had no success, in the meantime I have found that threaded rod screws down inside a standard 90 track rod and is just about the right length, filling the main length.

Threaded rod cost me about £6, a new track rod to fill it will cost me about £18. Sumo bars are about £70.

I'm not sure the material used in the threaded bar is ideal, however I'm willing to give it a go on price vs strength basis, especially since I have seen sumo bars bent too.

The internal diameter of my old series 3 rod however is not the right size to fit, so a new made rod might be needed. In fact my series 3 rod is thicker internally and externally than the craddocks rod I bent the hell out of going over a bump.

I've also found that box section is just (well maybe just, I failed on Saturday and ended up with a mess of metal) big enough to go over the track rod externally, which would add a box section strength to it. B&Q £5 stuff, unfortunately i was trying it on an already bent bar which had loads of rust and the box section started to distort as I smashed it with the mallet :) I might try again after trying the interior bar approach.

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Had this prob on the hybrid.

Mainly it was the front tube that went from sterring box to axle, but the logic is the same.

I tried a few homers 1st.

One was to sdrill a couple of holes around the tube into the cavity, then I pushed (read gentle tap in or in technical speak a JWhite No 18 :D Hammer) a piece of rod, 16mm from memory, then welded it in place, it helped but still bent.

Then I did the above and welded a lump of angle to it, same, bent again.

Then I bought a new pair of bars, and Danbars (sump are about the same) due to the OD and the joint wall thickness, I gave it terrible abuse (at least .78 on the Tonk abuserufar%se Scale) and never bent it.

I did manage to shear off a track rod, but fixed it in the mud, as such I still have danbars, but carry a std bar zippied to the roll cage "just in case"

By them Tonk there worth the money, you also probably need a new bat roo, cos the ID of the danbar is SOOOOO close ANY bend at all in the tube going into it and forget it it won't go on - work out how I know this fact :lol:

Nige

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I have 3mm wall 30mm box welded on over my track rod and drag link. Had the same on Alf too with no problems.

Shortly after I had the box weled on the bars for the 90 and painted them all up nice shiney, i picked up a pair of dan bars for £30. So they are in the garage for a rainy day, ie when i either bend my boxed ones or i decide to shell out on some new bars to put inside them :rolleyes:

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as jon says, cant have em on series, i have a couple of other ideas i'm thinkin about ;)

i bent it cos i took a tree out in reverse with my rear xmember then reversed over it, got horribly stuck up on it and tried to go forwards, still drove around for the rest of the day like it :lol::lol:

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We have had the same problem when we made the track rods strong enough we started to shear off the track rod ends, even genuine ones, so a compromise are Qt bars /bearmach strenghtened bars and std track rod ends and even these will bend .

Tonk should you consider spring steel ?

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Yeah, maybe, but they have canted ends where the TREs go, so the bulk of the bar is offset.

Sadly, I can't remember if this offset is vertically upwards or horizontally forwards...

I'll take some picks when I'm next about, but yeah, it may not fit.

Wouldn't the best option just be do make something like that though - thick old bar with a slight bend to avoid the diff? Maybe with more underside protection to fend off those trees / cliffs / small planets you drive over (in reverse, naturally)?

With this setup, the TREs themselves would almost certainly be the weakest link.

Rather than bending the bar you'd shear the threaded section of the TRE (or possibly bend it if it wasn't screwed in very far).

Hold on, I've got another idea: PORTALS !!! :D:D:D

Al.

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as already said, for the same mass, tube is stronger. Think of bike frames - they would be pencil thin if solid rod was stronger in resiting bending!

What I have done to my track rod is to put inside it a 14 mm tube (from B&Q), a slightly loose fit plus a 12 mm rod hammered into the tube, effectively making them a bit more solid. No idea how effective it will be though. Tere is also oil inside the track rod to stop the stuff rusting so I can take the rod out ... not sure why I'd want to do that. To stop the rod from sliding insdie, there are small length of copper tube (well, there would be wou'dn't there :P ) that is squashed by the tre.

I did this since I could use the original track rod with damper bracket. A larger diameter tube or dan/sumo bars do not come this this braket (ok, I could weld it on but ....)

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