Good Morning

I've read with some interest John Miles article in the latest Bulletin of the 750MC. As many of you know JM is coming back to Sevens after years messing about with modern cars and is building a special. As part of his approach he has examined and measured the torsional stiffness of the chassis in unmodified, modified and with body attached form to see how the various changes affect the result. It is most interesting.

However the bit that got me intrigued is at the end where he says, " Overall it is the hopeless steering attributes of a standard Austin 7 that ruin the experience, i.e. the combination of "slack" on-centre connection and ridicuously fast 10:1 gearing, which contributes to the "friction/jamming in mid corner."

One part of the solution he says is to reduce the steering ratio. He quotes Mike Eyre as saying that the 1931 Charles Goodacre Mille Miglia car had a 16:1 ratio which is approxitmately the same as a modern car. From my notes with Mr Goodacre the works standard was 18:1.

Does anyone change their ratios today for racing or the road and how do we measure the ratio?

Location: The south-eastern corner of Surrey

Julian,

If you examine a number of early type steering boxes you will see that the majority have a lot of wear on the thrust face on the bottom of the worm. This is caused by the serrated bearing face with sharp edges formed by the washer / formed end of the column tube (the way the worm is fixed to the shaft) not being suitable and the lubrication collapses giving metal on metal contact. If you modify the steering box to give a flat continuous thrust face, skim the bronze bush in the end of the box flat, and make sure that all the other bushes are in good condition then with careful adjustment of the box the steering can be made to self centre without modifying caster angles etc.

It is possible to press a thin thrust face part into the end of the worm and clear all the tubes for the hand controls etc.

The acid test is to jack up the front axle and move the steering lock to lock from the road wheel end. If you can only turn the steering one way or it is much easier to turn one way than the other then the steering box requires attention.

Regards

Rob

Location: The 3D shed,Tewkesbury

From when I raised this before there seem to be two camps:

First and in the great majority the happy campers who leave just a tiny bit of slack in the box, standard springy drag link and floppy shackles, and let the car find its own way down the road. With very little work their steering boxes will self centre and feedback and their cars will be delightful over any surface and for any distance.

In the competition camp the box is tight, the drag link is tight, a shackle is isolated. The car goes where it is pointed. With a lot of work a steering box can be light and smooth (many are not) and give some feedback and sometimes centre in one direction as long as the moon is full. The experianced racers just accept their cars as they have always been in much the same way as the owner of a pit bull has no problem with it and believes their dog to be great with children.

The problem comes when you want it to be precise, and self centre, and feedback, and be light, and smooth. "Ho ho ho" and "why bother" chant the rest. My own plan is to rebuild the hourglass box I've picked up and give that a go.

Unlike John Miles (so that would be me wrong then...) I was thinking that if it worked really well and with everthing else smooth to try quickening the steering with a longer drop arm at the box end. My only excuse for that error of judgement (I won't fight it, I know it's an error) is that mine is long wheelbase which from what some have said makes a huge difference to stability. From what many have said a really quick short wheelbase car is a proper tightrope walk / unicycle ride / bronko / exhausting. I also wonder what effect the wheelbase has on turning circle (getting it round a hairpin) and general "speed" of steering.

David

Location: Lewisham

I once (20 years back?) heard a story of someone racing on sand (in period) and making the steering slower with a longer arm at the axle end. Can't remember who told me or who the driver was. In the hope that sparks a memory from someone else.

Of course the other variable here is steering wheel size, and thinking now on the Midget and Aurelia I competed with (alas the Aurelia now gone) I put them back to full size wheels, more evidence of how daft the quicker steering Austin 7 idea might be.

David

Location: Lewisham

Location: Lands End, UK

Something else that bothered me before I actually drove my special was that the steering drag link (from axle back to steering box) wasn't level. The concern was bump steer. In practice the front spring is so stiff its not a factor.

Thinking now it might be a part of the the low frequency left/right/left/right "patter" I've experianced with it... Would there be a gyroscopic force up and down if the wheels are being waggled left and right over each little ripple and that feeds back and back and builds and builds?

I need to experiment with a bike wheel.

David

Location: Lewisham

John Miles is right about A7 steering, it’s awful.
The worst experience I had with the black car was at Goodwood, testing. On the fast left hander at St Marys, the steering just seemed to lock up every lap.
With the early type steering box it appears to me that the thrust from the worm on the column is taken through that horrible serrated thrust washer at the bottom of the worm/column on right turns.
Then the thrust on left turns is taken by the plain surfaces at the top of the worm.
However, the top thrust surfaces are unlikely to get much, if any lubrication and one of the lower thrust surfaces although lubricated is probably hardened steel and not unlike a milling cutter.
As for steering ratio.
I have just checked my rebuilt and as yet uninstalled 1927 steering column/box.
6 turns of the steering wheel gives 1 complete turn of the drop arm.
I can’t lay my hands on a standard steering arm at the moment but I think they are either 3 ¾ inches or 4 inches centre to centre. The drop arm is 3 ¾ inches centre to centre.
It occurs to me that the Big 7 steering arm might be longer??

This is the steering arm from the R.P.Lowe special as described in the ’Autocar’ July 14th, 1944.
It is 6 inches centre to centre.

my race car has the front steering arm extended by about 1 inch . this makes it a lot easier to keep on the black stuff, i have seen steering arms made from the ends of halfshafts (the threaded end not the coggy end)not tried it yet !!!

A bit contentious but has anyone ever fitted a steering rack longitudinally?

OK the various clubs etc might not be keen on a rack or even cancel your membership but have any of the guys racing in say the 750mc were the cars are dare I say it a bit more modern ever done it or considered it.

Our smaller tractor at work has a longitudinally mounted ram that pushes back and forth the equivilent of a drag link. If a suitable rack was found then it could be mounted to suit and one side/end of it could be attached to a threaded drag link. The other side or end would be redundant. The "column" would then just be whatever you fabricated and could be supported on proper bearings and have UJs to allow freedom of choice in fitting location.

Apologies to the purists.

Steve

With all this talk of steering, got me thinking about the making a steering arm to a custom length. I then remembered the neat and effective steering arm on John Way's racing Ulster, which is an ex Peter Hornby car. It uses a con-rod as the steering arm but I don't know what from. Does anyone have any idea?
I also wondered if there were any other con rods which were suitable that are ~6inches from crank pin centre to gudgeon pin centre?
I am going to take my steering box apart this weekend to modify it as discussed by Rob above.

All the best

Tom

John told me it's from an Austin A50. Just like Henry's.

Location: The south-eastern corner of Surrey

I'm not sure you're right about using an A50 conrod as a steering arm. The big end cap is fitted at 45 degrees to the centre line.
They are however 6.498" to 6.502" centre to centre.
I suspect that the 1940/50's side valve Morris Minor might be the donor. The big end cap fits at 90 degrees to the centre line and is 6.496 c. to c.
Alternatives might be Triumph and BSA twin cylinder motorcycle con rods.

Thanks Henry, lucky I didn't spend too much time trying to track some down as I couldn't find any information on the rods. I will make a note of the dimensions in my book and then keep an eye out for your suggestions at the jumbles.

Tom

Tom,

My dad tells me he found it necessary after the modification to file an oil groove across the bronze thrust face in the bottom of the box similar to the one on the upper thrust face. Nick also said to make sure the bush in the end of the column tube is not worn, one of his was 1/16th out of round. If you don't put that right you cannot effectively adjust the mesh.

It will be a challenge machining the thrust face of the lower bush flat if you are working with a vintage type steering box with the stator tube permanently fixed. I would suggest taking the tail stock off a lathe (unless it has a very long bed) and running the stator tube in a fixed steady.

Regards

Rob

Location: The 3D shed,Tewkesbury

Rob,
Thanks for the tip.
The bush at the bottom of the steering column is definitely ok as I checked it when doing my quick release steering wheel.
As a result of doing the Quick release steering wheel the stator tube was shortened. I had wondered about removing it all together and then making the replacement thrust spacer to have a short locating spigot. Thinking about it the stator tube probably does not provide any meaningful location and could be done away with and no locating spigot provided. With the clamping bolt on the large steering column thread it is highly unlikely that the two shafts will be running concentricly.
Hopefully I will get enough time to have a go at this, this weekend, but we will see.

All the best

Tom

I've had one of those "Doh" moments.

It wasn't just Austins that made an A50 - BSA at Hall Green made a 650cc twin commonly called the Royal Star which was serial numbered the A50. From what I can see online the rods are clamped parallel to the crankshaft with no offset like the Austin A50 rods. Perhaps that is what John Way meant. Need to spend more time spent looking at motorcyle parts stands at Autojumbles

Looking at the rods on various suppliers websites they certainly look very stylish.

Apologies for suggesting the Austin A50 type engine as a possible source Henry, didn't you ride Triumphs in your youth?

Location: The south-eastern corner of Surrey

Finally had time to sit down and think a bit about steering ratio's.
The standard box requires 6 and a third turns of the wheel to fully rotate the drop arm. Therefore when the drop arm is vertical the steering ratio is dictated by the steering box and the lengths of the lever arms. As the angular deviation changes so does the steering ratio.
The question then becomes where does the value of 16:1 and 18:1 mentioned above?
With calculation using measurements from a car the steering ratio will vary from ~7.5:1 to 9.4:1(at the extreme of travel).

Substituting a standard steering arm for one that is 6 inches from ball joint to king pin eye gives a range of ~10:1 at small angles and 22:1 at the extreme of travel.

Does anyone know at what steering angle the steering ratio is stated at?
It would be interesting to do some back to back testing of different ratio's and I think it was something Mike Forrest had a play with back in the 60's (I can't find my copies of the article at the moment).

John Miles who started this all off appears to be marketing steering arm adaptors to give an increased length:

http://www.classiccarama.com/classic-car-parts/advert/austin-7-steering-arm-modification-by-a7-dynamics/

All intriguing things to think about while mowing the lawn.

You know, I've read all of this thread and my over-riding thought is Austin 7 steering isn't awful. What is awful is the steering on Austin 7s that are worn out or badly adjusted. Personally, I'd be very wary of someone who tells me the steering on my car is awful, and then wants to sell me something to put it right.

OK chaps here are the facts:
The issue with std A7 steering is you have little or no real control at the limit of adhesion because of three factors 1) The dramatically increasing friction once loaded endemic in a worm gear 2) The free play in the joints and worm gear around centre and in transient manoeuvres 3) The typical 10:1 ratio. You will know that even a std ulster with flat rear springs steers from the rear axle as the front axle starts to bite, due to lateral weakness of the rear springs. Meanwhile the front is gaining gaining grip and friction exacerbating the instability leaving the driver as a "passenger" mid corner. Modern cars have steering ratios (average road wheel angle versus steering wheel angle)of around 16:1. This is to keep the cars response managable at speed. What would more response gain you? Nothing. Now bear in mind that the average modern car has a natural yaw frequency of about 1.5Hz (90 oscillations/min) when excited in yaw whereas the human responds at about 0.7Hz when correcting yaw deviations. A lightweight SWB A7 will probably be faster to respond making it even more difficult for the driver to keep in phase with yaw deviations even if he has the strength to overcome the afformentioned steering friction/jamming.
The solution (as Austin's knew in the 1930s and Bugatti did not) isto slow down the steering ratio. This has 3 advantages. 1) Reduced steering box loads therefore reduced friction/jamming 2) Reduced response gain at the front axle making the rear feel less laterally weak. 3)The potential to increase caster without making the steering too heavy.
Unfortunately there is a limit to how far the ratio can be lowered with the std steering gear before the idler potentially goes over centre on lock. 20% reduction is safe. After that you will have to think about reducing the full lock angles or make an entirely new steering worm gear.
Finally I could not bear to retain those overhung ball pin drag link pivots which seem to me designed to "snap here", so have converted to spherical joints in double shear at the hub end. Heresy but I don't really care because I want to actually enjoy driving the car, and they considerably reduce free play.
One final point is that in an ideal world you would not steer the car from a steering arm connected to a knuckle in turn connected to the track rod. The idler would be connected direct to the track rod as I believe it was on the model T Ford?

An afterthought re steering.
Assuming a basically standard steering set up you also have to pay attention to the sideview angle of the draglink. The better it looks i.e the straighter it is, the faster the steering ratio will be. On the other hand more angle potentially necks out the steering arm ball joint. Ideally on a lowered chassis it would be better to shorten the idler end but this normally means making a new idler or welding something to the earlier single piece type. I thought this would be a bit risky not knowing what material the idlers are made of.
John Miles

Hi John,
I have just found your 2010 comments on this rather informative thread.
I happen to be looking at this very issue on my special.
Having done the mods you suggest and with a newly rebuilt steering box with needle rollers etc how much play would you expect at the steering wheel (14" dia)
I am running Dunlop 4.50 racing tyres on the front 5.00 on rears, flat springs etc so want the best steering possible.
If you pick this up John I would appreciate your input also the experience of others would be helpfull.

Paul N-M

Location: Penicuik

Sorry, meant 2012 comments!

Paul N-M

Location: Penicuik

I have two Sevens with John Miles modified steering. An Opal and a special.The play on 14inch steering wheel with drop arm vertical is 20mm

This mod is probably the best thing I've done on both cars and transforms the driving experience.

Charles

Thanks Charles,
Thats very helpfull. How much did you extend the arm by? I was thinking 25mm.
Regards,

Paul

Location: Penicuik

Thanks Charles.

Paul

Location: Penicuik

The quick steering is one of the features of a Seven which makes them fun to drive on tight winding roads and obstacle courses. If it had not been for the ultra rapid response my saloon would not have been recovered from several extreme departures from the intended course and/or roll angle and would have been destroyed.

The basic flaw with the Seven steering is the inbuilt geometric error of the linkages. With no play in the box if the car is rocked the wheel turns through a wide angle, especially notable considering the ratio. For this reason the wheel is best lightly gripped. Over some waves and winds the car will hold course better with hands off! It is for this reason that many recommend distinct play in the box to allow the road wheels to deflect and re centre and so reduce wander over bumps and winds on the straights, even though a good box can be adjusted for almost no lost motion.
Despite wild antics I never detected any tendency to lock or to load impossibly in the Seven but with salons roll limits antics. I have discovered the unnerving lock trait in other makes with a lot of plain bearings.

The Ford system where the track rod is steered directly is not ideal with transverse spring and suspended shackles; the Ford Y is not noted for steering precision! Late US Fords had a Panhard rod to ensure axle end and track rod moved in similar arcs.
(The geometry with many makes of older cars was compromised; often countered by almost eliminating any spring travel!)

Location: Auckland, NZ

Hi Charles,
A couple of further questions if you can help.
Did you convert to 'rose' joints at both ends of the drag link?
If so what size of bolt (dia) did you take the taper out to on the steering box drop arm? At the moment I have tghe original style joint at the drop arm and 'rose' at the steering arm.
The drop arm looks fairly minimal strength wise as it is.
Thanks,

Paul

Location: Penicuik

Hello Paul,

Yes I have "rose" joints at both ends of the drag link and the bolt size is 3/8 unf

Hope this is helpful.

Charles

Location: Norfolk

Thanks Charles,
So using 3/8th you are relying on the torque up of the bolt to keep everything tight as the fit in the eye is not great due to the expanding taper?

Paul

Location: Penicuik

I have had no problems with this fortunately. Reckon if the assembly is careful you have a set up that is better than original.

Have you lowered the radius arms mounting to increase castor angle? (Packing piece between spring and chassis) This mod works in well with lowered steering ratio and taken together will bring a smile to the face on a bumpy road.

Charles

Location: Norfolk

Hi Charles,
Thanks for that.
I have a Big 7 front axle on roller bushes instead of shackles with bespoke spring (longer), panhard rod and double radius arms each side going back to the chassis sides.
The castor is set at 3 degrees but this is easily adjusted via the radius rod lengths which are on 'rose' joints. Final castor will be set by experiment. This is a pure track car in case your wondering.

Regards,
Paul

Location: Penicuik

It’s really good to come across an informative post regarding information outside the box!

As the above posters have said longer steering arms really helps so I was told by a well-known Austin 7 Single Seater Builder.

I have used two bicycle cranks carefully grafted onto the steering box shaft and the end of the steering arm. These are just over 6" long and should make for less steering input.

I am also using rose joints on each end and keeping the arms as inline as possible.

Also I found that the steering box gear has three positions so it can be moved around the shaft keeping away from worn surfaces.


The picture below shows a temp link arm but cranks in place.

https://www.facebook.com/LotusSportster7/photos/pcb.1304491196335053/1304490069668499/?type=3&theater

Location: West Sussex

This photo shows a slightly different set up. Big 7 axle split to give IFS... The track rod is split and joined with ball joints to the steering arm... Steering box mounted such that the arm operates horizontally facing forward... (Similar set up on the Worden, but the arm faces rearward. I'd give it a go on my Speedex, but i'm starting to worry about the points score, lest they do ever require retrospective testing of specials...?

Anyone got a 50's ford recirculating ballbearing steering box gathering dust under the bench?

Location: Colchester

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Having battled with Photobucket am using Flikr now so can show my solution. Along with a modified steering box (photo on Photobuckrt thread) I have altered the steering arm ratio as others have done.
The axle is a Big 7 one.

Paul N-M