Thought I'd share my steering idea...

Basically I wanted a custom rack, but was not prepared to pay the high costs so I thought I'd start with a low cost rack and make cheap mods...that's the theory at least.

Instead of lengthening the rack directly, I'm using the rack to drive a lower shaft in parallel..

Hopefully the pics should tell the story..




Steering concept




steering 01


[img][/img]

why not just lengthen the rack directly?

Don't you need to get a dog leg in the column?

Good questions, thanks....

I thought of extending it directly, but that would have needed two extension shafts (Ok, easy) but also two extension pieces for the rack housing which would have be pretty accurate both dimensionally and concentrically for it to be smooth acting...and then find a good way of joining and sealing it and still be rigid......It would almost be easier to replace the housing.

Doing it this way I also get the steering column higher up, away from my feet on the pedals.

No dog leg needed...it's central seating for the driver ala Mac F1...

[Edited on 31/7/07 by Alan B]

why bother extending the outers.. just run it through an outboard bush...

and the dog leg question was in case you crashed,,, you don't want the steering wheel becoming too good a friend!!!

drop your rack below the top chassis rail, add extensions, then run them though bushes (reamed - easy) mounted in the pillow blocks..

that way you get the dog leg (so that the column folds if you crash) you drop the weight lower in the car.. remove excess engineering you can get your rack parallel to the bottom wishbone..

however ... I'm not an engineer... just a keen beginer...

[Edited on 31/7/07 by bpgoa]

Good points again....I probably should have posted the idea before starting it...LOL

Re dog leg...Ok I get what you mean...I was thinking of a wire mesh type of collapsible column.....

Again, your feedback is appreciated...

it's a lot easier to pick something apart than to come up with an idea in the first place... you should see some of the bits I've thrown away

When the steering column runs directly between your legs it's even more important to have a dog leg in case of impact.....
Otherwise

Worst case- Ayrton Senna #2
Best case- Singing like Jimmy Sommerville

But then I'd be exceedingly wary of doing anything too DIY with regards to steering.....

After all, a wheel falls off, you can probably struggle to a stop.... the engine fails, you've still got steering and brakes, one side of the braking circuit fails you've got the other side of the handbrake (or engine braking)....

the steering fails... say hello to Mr Armco and his good friend Mr Local Casualty Department....

Isn't it a SVA requirement to have a 15 to 30 degree angle in the column, so it doesn't transmit the energy from a crash straight down the column?

Thanks again for all the input.

A couple of points.

1) The car will not be subject to the SVA, however, I totally agree that a dog leg created by having 2 UJs in the column path will be a lot safer in the event of a head on impact, therefore I will do that.

2) I fully agree with the potentially unsafe possiblities of DIY engineering and would discourage anyone unsure of their capabilities and knowledge NOT to undertake such things.

However, I am a qualified mechanical design engineer of many (too many..) years experience and have worked on many safety critical systems and components.

I also agree that steering is VERY important from a safety viewpoint, however I'd say that there are many other aspects of car building that are very close behind.

Again thanks, it's all constructive.

quote:

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Originally posted by hughpinder
Isn't it a SVA requirement to have a 15 to 30 degree angle in the column, so it doesn't transmit the energy from a crash straight down the column?

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Hi Alan


I realise your car is not subject to SVA but there is a alternative way to the mandatory dog leg, that being, a telescopic section.

As I understand the SVA regs the wire type upper section is to lessen injury should the driver be thrown forward towards the dash.
This is as well as a collapsible telescopic section OR dog leg of 11deg or more in the lower shaft.

As I have 9.5deg offset in my own build in the lower shaft I have made my version using two tubes that have slots milled in them,
and a boss inside with a protruding stud to act as a clamp. (see pic)

It may be easier to do a similar thing in your case, rather than a dog leg.

Just a thought.

Paul G
Rescued attachment tele-stearing-shaft.jpg

Ah good idea Paul.....so you're saying if you have a telescoping section and a mesh type collapsing section you should be OK without a dog leg or angle change?

Also, how much travel of telescoping do you have?...it looks like about 3" or so....is it nipped up pretty tight, or not?

Cheers,

Alan

[Edited on 31/7/07 by Alan B]

Hi Alan

I'm sure they give a figure of 127mm ( 5" ) but as it is fitted I have 10"

I'll also post the page from the SVA manual. Sorry it may be a tad big.

Hth
Paul G
Rescued attachment tele-stearing-shaft-dims.jpg

From the manual
Rescued attachment s-shaft-001.jpg

Go and have a look at a late model small car and see if you can use the whole column. In Australia we have the Daewoo Matiz. It has a nice, light column with a collapsing section in it and also a double jointed link at the bottom from distant memory

stiletto rack?

quote:

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Originally posted by tigris
stiletto rack?

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Hi Alan,

how you doing?
just a quick thought on the steering design.
the only problem i would see is that you are introducing other components into the steering function that are liable to wear out / fail over time.
if you lengthen the arms and connect them directly to the hubs then they are the only component doing the steering.

i can see as a design it would work but i like to keep things simple with less components to go out of alignment or wear out.
As someone else said tohugh it is easy to analize someone elses design than come up with one of your own.
just my thoughts.

Thanks for the hospitality on my visit to Florida, i will sure remember the sugar shack for a long time to come.
I have told the story of the nights events to my friends who found it very entertaining!

cheers

Paul

Hi Paul,

Glad you had a good time and enjoyed the Shack..

First of all utimately I will make my own decision on the steering design, as we all would. However, it's not say that everyones opinion is not valued...trust me it really is and I'm quite torn on this one.

Bpgoa said....

"drop your rack below the top chassis rail, add extensions, then run them though bushes (reamed - easy) mounted in the pillow blocks.. "

Which I think is a simple and obvious answer.

However, my point against this is the fact that the original rack bar is tapped 3/8-24 at the end and would easily extend with studs and extension pieces, however they would be relatively long (about 7.5" each) compared the rack bar length of about 9" and without very long outboard bearings (which aren't possible without losing travel) I'm concerned about the buckling stabilty of the whole assembly....kind of scared of it buckling at the knees so to speak.
At least with my version I have a full length solid bar that is attached by two robust arms to the existing rack ends.

Paul, about your point re: wear and tear, the only extra wearing parts are the two outboard bearing blocks which would be used on the simpler version anyway.

Saying all that, the simpler version is course...well simpler...and a little lighter not using the side arms.

So quite honestly, you all have made me re-think my solution...I know I don't have to convince anyone but myself...I'm totally convinced that it's safe and reliable......but is it the best solution....??

Who knows...we'll have to wait and see..

Again thanks all......

Hey Paul maybe I should post some Sugar Shack pics for everyones amusement?

Colin Chapman used remote steering on The 4WD lotus 64 which might be a better option/layout.

Will have to try and find photos.

"Hey Paul maybe I should post some Sugar Shack pics for everyones amusement? "

yes please do Alan, it will bring back some good memories.
It seems like an age ago since i was in Florida.......................it was only two weeks ago

Hi Alan,

mmmmm, tricky one!

I personally would not be keen on doing it with the parallel bar. The bending loads on the two legs that connect the rack to the slide bar will be pretty unpleasant, and the loads they impart on the rack ends will also be quite nasty.

What lengths of steering arm do you need? I assume its not possible to just use very long steering arms!?

If it does need extending (which it obviously does for you to be going to this trouble! ) then I would say that screwed in rack extensions would be fine, made from the same diameter bar as the rack itself and staked or high strength loctited into place