Steady On

Hi All,

I see much mention and use of different systems to secure the top of the motor to the frame - headsteady systems. But for the ignorant (i.e. me) what do they do that isn't done with the normal rubber isolastic blocks? It looks like they allow movement of the motor in the fore-and-aft plane, but not side-to-side, to what benefit? What are the advantages and, if any, disadvantages? What systems or brands perform better or best? If they are a worthwhile addition, is it possible to make my own out of balljoints and Aluminium extrusion and if so are there any public domain plans available?

As always, thanks in advance.
Yours,
Curious of Nunawading.

davamb said:

But for the ignorant (i.e. me) what do they do that isn't done with the normal rubber isolastic blocks?

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They make the life of the two std isos a lot easier. The whole idea of the isos is to use a planar guiding system to add torsional stiffness to the chassis - which is very important for handling - and use the softness of the rubbers where it is needed and doesn't hurt.

In terms of riding a bike you really don't care whether your front and rear wheel move a few mm closer to each other or up and down relative to each other because the rubber allows them to do so. But you do really care whether your wheels stay in line to each other under lateral forces.

The std head mount does nothing to add to torsional stiffness, it lets the bike twist like hell if the two isos give up. This means as long as they work all the torsion from front to rear wheel is transmitted via the edges of the isos. Adding an iso mount or one of the rod-end type head steadies means that the torsion - in terms of lateral forces - is fed into this mount as well which drastically limits the pressure on the edges of the std isos.

In terms of geometry three isos form a plane - hence giving a planar guide. But this also explains why rods (like HD uses) are better than the sliding discs of the isos: Each iso is a small planar guide in itself so if the three aren't perfectly parallel (which they never are giving the flimsyness of the Commando frame) the counteract each other.



Tim

davamb said:

what do they do that isn't done with the normal rubber isolastic blocks? It looks like they allow movement of the motor in the fore-and-aft plane, but not side-to-side, to what benefit?

Click to expand...

I suspect it's one of those things you never knew you needed until you tried it?

I haven't tried one of these special top steadies yet, so as far as I'm concerned, I don't need one. 8)

Well, I waited 33 years to put one on mine, because I never thought that one would help.
So I parted with £200 on a beautifully advertised iso head steady, & spent 3 evenings filing, scraping & repainting to get it to fit because of the crap workmanship.
After 33 years of not having one, I can tell you that, wait for it, it doesn't seem to make a blind bit of difference!
Still got the same old handling problems.
Wish I had kept my old Super Rocket.

Flo said:

Well, I waited 33 years to put one on mine, because I never thought that one would help.
So I parted with £200 on a beautifully advertised iso head steady, & spent 3 evenings filing, scraping & repainting to get it to fit because of the crap workmanship.
After 33 years of not having one, I can tell you that, wait for it, it doesn't seem to make a blind bit of difference!
Still got the same old handling problems.
Wish I had kept my old Super Rocket.

Click to expand...

If you went with an iso type headsteady I'd be surprised if you did see that much difference. The link styles have been around for a while now, why didn't you use one of those?

I"m so glad truth is comming out on the nil importance of a head steady
no matter the type.

EVERYTHING on a Commando, pilot mass, engine orbital,
fork slap loads, power pulse traction dampening, road texture
and wind buffet, tire aim and air spring coflicts, chassis twist
>>> Focues on rear isolastic as Pivot. All of em leverages thru rear iso.

The Harshest Fastest Rough Ricochet Rabbit Riding Glee's I've
ever attempted on Ms Peel was with just Patton's rear low link.
No Head Steady at All!.

If not riding into OR beyond Hinged Antics, I'd fore go any
head steady at all. Pashaw I made the first one work
and find its a lot of worry and hype about nothing much.
All I can sense it does is take last of wiggle jiggles out of wind
buffeting on stem and forks, that most, [if any one else]
can tell from road texture or engine vibes in a strained frame,
because they don't have a rear link to
untangle all the sploshing and splashing in an untamed Commando.
I rate best possible contribution of a perfect head steady
function as maybe 5% smoother and more massive sense
of inertial stability.

BTW a slight silly mm of spring compliance in top link
pays back wonderfully one a rear link allows frame
articulation to take tire conflicts out of the equation.
Yeah a shame, if I'm right all the engineer experts
will have to re-think basic road going assumptions.

I've a rigid SV650 on full upgrade suspension and race tires
and learned modern tarmac handling limits on 900 Nina, All
too damn rigid they all just resonance themselves into
corner cripples way way before a tamed flexy flyer
Commando does, if a tamed Commando can even
be made to become upset no matter what, so far
ain't been able to way way beyond anything I've
ridden or watched on video expect for ice spike
speed way bikes.

BTW if you over ride these modern wonders you
can stiil save em by hi siding up long enough the
frame springing settles down before touch down.
But they are so unpredictable at what limit they
go crazy so fast its beyond human reflex to
compensate, Its Not worth the risk to me any more
to seek unsatisfying bit extra mild G's pressing them.

To those this sounds crazy too, don't need any head steady,
To those this makes some sense too, BEWARE the
front and top head steady WILL NOT STOP Hinged onset
But Will move its onset up to frequency and intensity
that human reflex and power can not compensate for
in time to matter SPLATT!

Need new subject on Watt's like linkage ala hobot,
based anchored and pivoted on Bob Patton rear link Wonder.
To impliment this requires some fore thought on
angles of opposing rod links and normal front link mounting
may not allow Watt's control at extreme loads.

http://upload.wikimedia.org/wikipedia/c ... inkage.gif


hobot

interesting article in this latest roadhandler on adjustable/vernier iso's. loosen everything and adjust rear. more often than not front iso is so out that it needs milling to retain adjustability. most frames are not kosher geometry wise. i just got hemmings adjusters front/rear and new rubbers. also new rubber on head steady. i've been fooling around w/ the clearances just to get acquainted. reckon i'll try the above and see where my frame stands geometry wise. from what the dude in roadhandler said it made a real and significant improvement in handling.

Races and police ran tighter iso clearance and put up with vibes
in turning loads. IIRC, generally set to half the manual clearance.
Still a stop gap solution as does not stop hinged handling onset,
just delays it some.

My only concession to non '72 items for my factory Combat
is an 850 swing arm with collars kit and the vernier isolastics.
Took wrenches and adjuster probe and played with
adjustments on the road to find good compromise to lock down.

Even sloppy loose worn Cdo's can fling a mean corner
and switch backs with only a twitch as slack taken
up. But in longer held loads of sweepers, all hinged hell
can let loose. Same for tightest iso Cdo but at faster
rates and higher loads before onset. So its good to
snug up iso as much as practical and get parts
all squared up -just not transforming to full potential
of iso Cdo's. Therefore fastest racers use solid mount.

Trixie Combat's under spine tube is skewed 3/8" to L,
and down tubes a bit tweaked, makes it a bugger to
get front iso mount in and factory head steady
requires 1/4" rubber shims on opposite bracket surfaces,
but rides and handles as fine as any factory Commando.
So good to aim for perfection, its mostly for
ease of assembly than any handling improvement.

One thing I've never seen mentioned but I've noticed.
When rear patch is side loaded it pivots through
rear iso to press sideways on front iso. Pressed hard
enough the front tabs can lean over and twists
tube like torsion springs.
To see how little force this takes, stick a screw driver
thru tab hole and lever on it a bit.
In the least this would allow iso to bind and vibe,
in worse case spring back can fish flop off the dock.

No head steady can restrain this, So flip a coin on type,
work a bargain deal or make your own. Same difference
to function.

hobot