BRAKE
REACTION BARS
by Gerry Willburn and Lorne Goldman
(Lorne) Smart trad owners all use them, the Factory install them on request....but why?
Too many owners, don't understand them. They put them on because someone tells them to. As I an amateur, myself, I dislike that. One
of the great gifts of Morgan ownership is that they can lead to
mechanical and electrical understanding that can massively benefit your
life and not merely your Morgan (s).
Trad
Morgans are not perfect..though they CAN very close to be so with a bit
of common sense and this Manual. Auto mechanics is not magic...and the
experience of long mileage can reveal ALL. My Morgans have become the
most reliable vehicles I have ever known
Brake reaction bars (or Upper Cross Axle Braces, as
they were once known) address the movement of the top of the suspension
pillar and locates it with respect to the chassis. There is already
a brace from the bottom of the pillar back to the chassis to locate that
end. However, under hard braking, the top of the kingpin assembly moves
under that force to ill effect, being that wobble of the front end you feel..which also reaches the steering wheel. Hard braking is urgent enough that you do NOT want to be controlling the steering wheel at the same time! There are two basic sources of this movement;
(a.) the action of the suspension itself, particularly on washboard surfaces
and (b.) rotational reaction from braking stresses.
(Gerry Willburn) I
must admit that when I first put them on our DHC back in 1959, I had never
even heard of brake torque reaction. I was addressing the movement
on uneven surfaces which (in addition to making the steering a bit vague)
caused cracking of the front wings just inboard of the wing lamps due to
movement of the wing stay attached to the top of the pillar. These cracks
began to appear within weeks after we bought the car!
I asked Chuck Talbott (then Tech Editor of the Morgan
Plus 4 Club) and he told me that all of the racers had installed a brace
from the top of the pillar to the chassis where the damper blade is attached.
I built them myself (as well as for all of the Morgans I have had through
the years). All were made from aluminum and I used thin wall electrical
conduit tubing.
After
cutting approximately to length (a little long),
one end is flattened with a hammer on an anvil (or the end of a vice)
and
drilled to take the oiler bolt at the top of the king-pin. This is then
bent to the angle required, the other end measured and flattened. It is
bent to shape and trimmed as necessary, then drilled to take the
forward damper blade bolt.
It is a very simple installation. The only trick is
the avoid accidentally nudging the kingpin assembly after you remove
the top bolt. Take it out and then immediately put the bar and bolt
back on and thread the bolt, to secure it but not to tighten it
completely at this stage. I am
concerned that you lose the exact alignment of the top bolt into the
kingpin threads and or the kingpin and the main spring dislodge. (That is dangerous!!) Then let it find its proper spot on the frame, drill that hole and tighten the two bolts. I have never seen
any indication of damage to the frame through their use.
One precaution
is to use bolts weak enough to shear in an impact.
 WATCHPOINT:
(Lorne) Brake Reaction Bars are made of a number from a number different metals
and formats and levels of sophistication these days. They can also be purchased
from Mulfab or almost everyone. See PARTS page. There is also a write-up on making and fitting them
in Cuthbert Twillie's famous A Yank in Malvern and that is the source of the diagram above. They can even be as effective when made from a flat metal strap you can find as scrap.
Update July 2012: I have noticed that the Factory
has copied the Mulberry design
and is now selling them in stainless through their dealership network. I have no reports as yet on the strength
of their retaining bolts.
Please note: The pictures
here, all different versions, show different attachment point as well.
Each has been successfully used by Morgan experts.
I use the ones just above in this box. I obtained them polished stainless
from John Worrall. They are fit in the Mulberry fashion pictured above.
|
(Gerry) The first thing I noticed after installation was how much
better the steering felt in rough corners. The cracking of the 
wing
ceased (and was covered up by installation of wing mirrors over the top
of the existing cracks and bolted through the wing stay). I have since
installed them on every Morgan that Barbara and I have owned and several others for friends. I think they are beneficial to all Morgans. I
have always installed them "to fit" and never made any attempt to adjust
caster through them. I am the most surprised that they only recently
(in the last several years) re-surfaced as a "new" innovation in England. (
wryly)
(Lorne)
The second thing they prevent, especially for those of us, like
racers, who brake hard and often. They prevent the deadly bending of the
cross-frame. See the famous John Sheally II's old cross frame
to the right. Even a bending of the cross-frame subtlety is enough to sadly alter your front end dynamics
without you knowing it.
Please NOTE: The Cuthbert Twillie diagram to the left attaches the bar to the wing stay foward of the old one-shot oiler hole which eMog and logic convinced the Factory to get rid of. This attachment point should have no prejudicial effect and is less invasive and risky for one-shot oiler cars..
As well. one shot oiler bolts (a unhelpful system) are not graded and
can shear. THE MOST IMPORTANT WATCHPOINT in this process is the
one alluded to above. Where Morgans are at their unintentional best is
the amazing crumple zone effect they have....many years before Formula
One and the then regulatory authorities realized that
safety feature. It saved the lives of my wife and I in
2002. My wife and I survived as the Morgan flexing ladder frame,
eliminated in 2020, combined with the wooden tub also eliminated at the
same time, absorbed impacts before they reach the cockpit.
In the front part of the car, Morgan bend at the bulkhead, allowing the
entire front suspension and the engine to resist the impact force's
egress before they too reach the cockpit. (I have seen the Aeros react
the same way). Though unplanned, this crumple feature is fantastic.
Morgans do have unsafe areas, but with a negligible amount of money and
good sense, they can be cured.
So the trick is to use these reaction bars to steady the front end,
providing the great benefits discussed above but WITHOUT eliminating
the natural safety elements and having these bars transfer impact
forces in an accident to the cockpit. To achieve this is merely a
matter of using weak bolts that will shear in an impact but are strong
enough to do the job intended. As Gerry noted above, we are not sure
the what bolts the Factory uses with THEIR kit. I use the pretty polished bars shown
above..and they will shear not only at the bolts but at their bend
pleats as well.
THE CROSSFRAME (aka crosshead) Morgan
is the ultimate governor of steering and front suspension dynamics.
Sadly, they can bend , either in an accident or, especially in cases of
the more powerful Plus 8s, by braking forces over time. Many old timers
use their old kingpins rammed down the lower tube to prevent this, but
GoMoG /eMog popularized the brake reaction bars, which have multiple
beneficial effects, among which is the prevention of this sad effect
forever. It also cures the problem without adding much weight, unlike
the kingpins. NOTE that cross frame must
be properly adjusted to each car. That is the reason for the adjusters
at each end. One carefully measures the distance between points at the
the rear of the chassis and using a leveler to confirm the straightness
of the crossframen and adjusts accordingly. Brake reaction bars will also help with this issue over time.
Note: The Adjusters
Pre 1996 used 3/8 BSF, 20 tpi
Post 1996 used 3/8 UNF 24 tpi