What cars don't have power steering AND have low ratio?

[John]

Nero, is it high or low ratio that you want? are you talking steering ratio or gear ratio?

Obviously power steering always have a HIGHER gear ratio than equivalent manual systems, but a LOWER steering ratio.

Another thumbs up for the camira rack. It's a reasonably good bit of gear.

J

[Nero]

how would I go reducing the amount of assistance in the original 380 power rack...would this assist in increasing the amount of feel?

[Ben Wilson]

this is correct. It's more the teeth themselves than the rack actually. All the steering loads in a manual rack are going through the teeth, which this is not the case on a power rack. Therefore, ratios and teeth design, as well as material and heat treatment even are often very different between the two systems.

So, the cars mentioned in the other thread with electric power steering should be OK then?

[John]

how would I go reducing the amount of assistance in the original 380 power rack...would this assist in increasing the amount of feel?

Not easy. Assistance is a function of torsion bar stiffness and piston diameter, neither of which is very practical to change.

And no, reducing the assistance is not necessarily going to increase the feel. It might help, but it's not a given by any means. Feel is very hard to quantify, but it's a factor of the quality of gear mesh, stiffness of overall system, ratio, hydraulic gear design, inertia of system etc etc.

J

[John]

So, the cars mentioned in the other thread with electric power steering should be OK then?

Ben, not sure what you are asking. Which other thread? (there are now 2! ) I think all column assist EPS systems are rubbish compared to hydraulic systems, only a few (golf been one of them) fully EPS systems come close to steering feel of a good hydraulic or electro-hydraulic system.

One of the many problems with EPS systems is that very few except for the premium ones (ie Golf again) use torque sensing as well as angle. ALL the cheap ones on small cars use only angle sensing, ie the amount of assistance supplied is only a function of the angle input, which is obviously a very large compromise when you are asking an electric motor to provide power. And of course probably the biggest problem as I mentioned in teh other thread is that for good steering feel, you need a low interia system between the driver and the pinion, and all column assist systems have a great big motor between them, so not exaclty low inertia.

Edit. If you mean that the rack and pinions themselves would be strong enough, then the answer is yes. As mentioned above by cameron_datto the systems are basically manual with the motor bunged onto the column.
J

[John]

Nero,

Smart cars are manual. I actually did quite a bit of work on the MCC Smart steering, albeit the EPS version. But the manual systems were actually quite ok, and why anyone would buy a electric system over a manual in a car like that is beyond me. However, I don't whether the oz delivered ones were EPS or manual. Worth checking out.

J

[Jim]

Neil, just sorting the camira rack pics for you now. Will the last of the camiras ('89?) be in the same ADR group? I don't know if Daewoo used this type or not, but my guess would be yes.

[Jim]

Here's the camira rack and dimensions. If it's of use to you I'll post it to you as I have no need of it. It is roughly 4 and a half turns lock to lock, probably a bit much for you, but I'd imagine the euro guys would have bolt in options for the application.

[Nero]

Thanks Jim, I can't see how I would avoid bump steer with such a diff to the suspension pickups and 4.5 turns loc to lock...wow! How much do you reckon it would weigh?
John, thanks for your input. Smart cars are rare and a wrecked one wouldbe hard to find. I am starting to run out of choices. The logical thing would be to use the 380 rack...I have one, it comes as part of the engine package and matches the other components, so if anyone wanted to replicate the car all they would need is a front cut. But it is heavy! and I would have to run the power steering fluid through 10 feet of tubing.

[Jim]

It probably weigs maybe 2 or 3 kilos, it's pretty light. Yeah, a bit under 4.5 lock to lock, but it has a reasonably long stroke so I guess you could reduce how much of that you need with the steering geometry. No idea on the bump steer issue other than I thought the further towards the centre of the car (the longer the arms) the better to reduce bump steer? Never noticed it as an issue in the camira, it was a well handling car despite it's appalling build quality.

The picture may be a bit misleading as it is showing the rack at one end stop, not in centre.

As to the PS tubing, 10ft of 10mm steel tubing wouldn't weigh too much. PS needs pressure not volume, unlike say the cooling system.

[Nero]

I'll mock up with the 380 rack as it has 2.9 turns lock to lock and I can easily change it should it seem to heavy...in fact I will weigh it too.

[Billzilla]

Try to get the steering as 'fast' as you can, it'll help in the odd bit of motorsport you do in it.
I asked for the fastest rack that Mr Fraser could give me, as the one I drove in NZ (I can only fit - just! - into one other one) had the steering too slow for me.

[thechuckster]

i thought the outer control arm connected to the rack should be the same length as the LCA? .. but then again, the camira works in opposition to the laws of nature, science and all that is good in the world... so maybe it's not surprising that it works despite looking so wrong.

[Nero]

well the std rack seems out of the equation...the input shaft is at a bad bad angle. So I need a more central position input shaft on a rack...anyone seen anything?

[msmola2002]

Probably not much use, but I think the 1980s porsche 911s (up to the one that ceased when the 964 came out) had a rack which has the input right in the middle. No idea where to get one, and would probably be worth arm/leg/kidney too.