Right then - now that the car has passed SVA I'm planning some improvements. One is to replace the column with a simpler design running in spherical bearings. I have a Grp 4 steering coupling and a length of 5/8" steel bar which has a spline on both ends (from Rally Design). I need to cut this bar and extend it by welding it into each end of a steel tube, but what tube has a 5/8" i.d.? The o.d. isn't so important, providing I can source spherical bearings to suit.

Thanks in advance for any advice,

Eddy

the reason you are not allowed to weld steering columns is that it is dangerous, simply put. Ayrton Senna died because of that, and although it is very difficult to happen, in case it does, the results are usually disastrous.
I donīt think it is that hard or expensive to have a custom made splined bar, is it?

Think you will find official cause of Senna's crash was down to low tyre pressures causing loss of ride hieght affecting down pressure . Steering column may have broken on impact . Thats if you can believe what you watch on tv. Suspect most Locosts have welded columns ?

Certainly the majority use a Sierra-based column (as I do). The upper part is unmodified, and the lower part (triangular clampy thing to donut UJ) is normally extended by cutting and welding.

As far as I can see the original Ford lower column includes some welding at either end anyway. Forging the whole thing in one piece would be difficult and/or expensive.

gustavo - I'm not sure what you mean by "you're not allowed to weld steering columns". My car (and countless others) already passed SVA with a welded column. I'm merely changing the design to reduce any friction inherant in the nylon-bushed Sierra column in an attempt to maximise steering "feel".

Rusty Nuts - the official cause (after a lengthy enquiry) was low tyre pressures following an extended session behind the safety car allowing Senna's car to bottom out. Many people, needing a scapegoat, blamed the constructor.

Eddy

i can guarantee all mk indys at least have welded columns.

if the steering system isn't to be welded, i fail to see why all race spec quick release bosses have a slug that has to be welded onto the column.

obviously a solid bar can't fail, but neither should a good weld.

just venting my thoughts,
tom

The column itself hasnt got a huge amount of force going through it. The highest torsional force it sees is whatever you can apply to the steering wheel without moving the wheels. Ceratinly a lot less stress than the strength of the welds!

Most kits use a welded column, as infact do many production and racing cars!

Cheers,
David

Back to the original question - where can I get some suitable tube? 19mm or 3/4" 18 or 16 gauge is too loose a fit around the 5/8" shaft. I could always turn up an adaptor to mate the two together, but it'd be less hassle to find the right tube.

Eddy

Eddy, surly 3/4" od x 16g (1/16th) is 5/8" id.


I just measured some I used to brace my engine bay and it's 15.8mm, i.e. 5/8"


I'm confused,

Paul G

Err...sorry. My maths, particularly converting 'twixt imperial and metric, isn't what it should be. You're right about the 16SWG.

Cheers,

Eddy

I never weld my steering columns. I use CDS tube (size depends on length) and slide the ends into the tube. I will then drill through both and put a pin in. I then braze the whole lot together.

This avoids any risk of the weld effecting the metal. It is also mechanical (the pin) and brazed.

If your brakes fails at least you pick where you hit, if your steering goes.........

John

good points there JB.

In the past i had a 19mm tube that was a very snug fit over the sierra downlink tube. The other stuff ive used was about a mm too big on the bore - odd, since i thought it was all the same stock. However, neither failed.

Im trying to make a point of including 'good practice' in my workshop approach, even when it doesnt seem necessary. Hence when i change the steering column (again...) in a few weeks, i'll give the pins a go.

Thanks for the suggestion - I was planning on drilling, pinning and welding the pin (no brazing gear) so you've confirmed I'm taking a sound approach.

Cheers,

Eddy

I weld the column, but fully appreciate what John Beardmore is saying.

I use CDS, turned out for a press fit onto the splined shaft ends, then angle cut the ends of the tube to 45 degrees, press the ends in and mig around the 45 deg cut. the angle spreads the shear plane to some extent which helps.

I would also use heavier tube the 16swg. In theory this will be fine, but a thicker tube makes welding a lot easier and stronger if you don't have a TIG machine.