Adjusting Cobra Trailer Brakes
Charles Petersen
"Depending on driving style, the overrnning brake starts responding hard after approx. 1,000 km. It
is then an absolute must that you readjust the wheel brakes in accordance with the instructions for
use (located in front part of trailer). In no event should you adjust the brake rods !
The first adjustment is very important for proper functioning and service life of the brake, as in
the beginning up to the grinding-in of the brakes, wear is at its greatest and very one-sided. So
please don't forget! After approx. every 10,000 km, the linings must be checked and adjusted"
I do not have the 'instructions for use (located in front part of trailer)'. If anyone has this I
would appreciate your forwarding it to me. Other advice is welcome.
Greg Arnold
Cobra, and at this point it has way in excess of 1,000 km.
John Cochrane
ground at a contest. His answer was this: jack up the trailer. There is a
little hole on the inside of the wheel. Open the access cover. You'll see
teeth of a gear thingy. Rotate that in the direction shown by the arrow --
use a screwdriver -- until the brakes just start to rub inside the wheel.
Back off slightly. (Just like an old VW if you had the idiot guide!) Then
readjust the handle height to point straight up by adjusting the bolt in the
middle of the trailer -- not the one near the handle.
This is second hand, and I haven't done it yet, so a call to your Cobra
dealer might be worth while. Or let's hope someone more knowledgeable
answers the post
John Cochrane
"Greg Arnold" <Soa...@REMOVEcox.net> wrote in message
news:kNHk9.120620$Pf7.4...@news1.west.cox.net...
Jim H
and Komets. Most of the info is applicable. Long post!
http://www.dg-flugzeugbau.de/anhaenger-e.html
Brake system (Kobra)
The position of the hand brake is an important indicator for the wear of the
brake linings. If the brake lever moves past vertical to aft the wheel brakes
need adjusting. To do this, jack up the trailer and secure it, turn wheel by
hand, and lever the adjustment wheel in the direction of + until the linings
touch lightly, then back off until the wheel spins freely. Under no
circumstances adjust the brake rods! Occasionally the brake linings should be
visually inspected. Old, hardened linings should be replaced. The bowden cables
should be cleaned and greased to keep them freely moving. Never drive with
frozen bowden cables or with the hand brake on. Because of the resulting
overheating the grease in the wheel bearings will melt and run out, and the
overheating of the bearings can sever the axle and cause a loss of the wheel!
Overheating of the axle grease usually results in radiating grease traces on
the tire or rim.
http://www.mindspring.com/~hennulat/Trailer.htm#Brake
Brake System (Komet)
The brakes on all Anschau sailplane trailers are of the surge-type, which means
that during deceleration of the tow vehicle, the inertia of the trailer pushes
forward and compresses a piston in the tongue. This mechanical movement
actuates a lever and rod system, which presses the brake shoes against the
brake drums. Of course this system is also actuated when backing up a hill. To
prevent a locking of the brakes in this case, the brakes contain a feature
called the "backup automatic". One of the brake shoes has a spring loaded
sliding bracket, which decreases the effective diameter of the brake shoes when
the wheel turns backward while the brake shoes are in contact with the drums.
This releases the brake and allows the trailer to roll backward even though the
brake is applied.
The backup automatic is of course also effective when the trailer is parked on
an incline with the tongue pointing uphill. To assist the hand brake in this
case, a set of wheel chocks is mounted on all late model trailers, which should
be placed behind the wheel. These chocks are normally kept in stock by ENTEC.
It is recommended to have all brake and bearing work performed by a reputable
automotive shop.
The brake rods are made of special high tensile steel and should not be
replaced with regular hardware store type threaded rod. Brake shoes generally
come in two different widths, 30 mm and 50 mm. The brake lining on all modern
brake shoes is factory bonded to the shoe and cannot be replaced separately.
The brake rods are connected to a balance beam under the chassis, from which
the Bowden-Cable type "pulls" lead to the brakes. On twin-axle trailers a main
balance beam is connected to two secondary balance beams, each one of which
works the brakes for one axle. A rubber O-ring is connected between each end of
the single or secondary beam and the frame, pulling it backwards and unloading
the brake system if the surge mechanism is inactive. This greatly extends the
life of the brake shoes. On older trailers, aging may have deteriorated the
rubber O-rings to the point, where they no longer exist. ENTEC stocks
replacement O-rings.
Adjustment Procedure:
Jack up your trailer and support it so that both (all four) wheels are off the
ground. You may want to do this without the sailplane in the trailer. Make sure
that the brake shoes have sufficient lining thickness (2 mm minimum) and that
the brake drums do not have any deep grooves. On some very old trailers, more
than 25 years, especially on Grau and Peitz axles, you will find rivetedbrake
linings. On these, the minimum lining thickness is 4 mm. If one brake shoe
shows excessive wear, all shoes should be replaced (for both axles on twin axle
trailers). Clean out all debris and dust. If you are using compressed air, wear
safety glasses! This is also a good time to have your bearings checked and
repacked.
There are generally two makes of brake systems employed on Anschau trailers,
Peitz and Knott. All of them use Knott brake shoes. The adjustment mechanism
for Knott systems is a hex head bolt on the upper axle side of the brake back
plate, for Peitz a wheel type screw, which is accessed through a hole in the
back plate. This wheel type adjuster is turned, by levering, with a
screwdriver. If it cannot be turned, remove the brake drum and free the
adjustment mechanism. Please check in which direction the mechanism is
spreading the brake shoes, since it is possible to install it in more than one
orientation. The brake drum should turn easily and smoothly (without
hesitation).
· Disconnect the rod system completely at the balance beam.
· Tighten the adjustment mechanism until the wheel is completely blocked
when trying to turn it in the forward rolling direction.
· On Knott brakes, loosen the adjustment bolt 5/4 turns (the clearance
allows you to turn it only ¼ turn at the time). On Peitz brakes, loosen the
adjuster until the brake shoes rub only slightly.
· Re-connect the brake rod system and with the hand brake lever fully
loose and the tongue pulled out. Tighten the rod system until a slight rubbing
noise is heard when spinning the wheels in the forward direction.
· The balance beams should be straight at this time. Re-adjust the pulls
or the rods to the secondary beams if they are not.
· Test the release of the backup automatic by pulling on the hand brake
(on brakes with a tooth segment three teeth, on brakes with an energy storage
spring in the rod system 30degrees.
Try turning the wheels in the backward rolling direction. If the brakes do not
release, the adjustment on the brake shoes (bolt or wheel) should be loosened
slightly. If this doesn't help, the mechanism for the backup automatic is dirty
or rusty. Try cleaning it up.
It should also be checked whether the brake chatters. If it does, the brake
lining is worn too much and the brake shoe with the backup automatic is cocked
too far. The brake shoes have to be changed.
· If the brakes work too suddenly, there is too much slack in the rod
system or the surge damper in the tongue is weak. Try tightening the rod system
a little first. The surge damper should slowly push the hitch end back out if
you push it in manually. There should be a definite resistance when you push it
in. Unless your tongue assembly is of the type
Knott KR 13/7, you need to disassemble the surge brake mechanism and measure
the extended length as well as the compressed length of the damper to order the
proper replacement.
Jim H.
CFIG
N483SZ
gapagod...@aol.com
JJ Sinclair
correct. You will find a 3/8 " hole (1cm for you limeys) located at the 2
o'clock position as you face the inside of the wheel. There is an arrow that
shows the direction to make the slotted disc move.
Remember to block the other wheel on both sides (front and rear) so that your
trailer doesn't try and move while the intrepid pilot is undernesth.
JJ Sinclair
Jke4034
putting the brake adjustment instructions in the front of the trailer. . . .
Hi John!
The Alko company as the manufacturer of the axle does not recommend that people
without expierience adjust trailer brakes. Adjusting brakes needs not only the
knowledge what to do, it also needs some feeling what the right pressure from
the brake shoes to the brake drum is. A wrong adjusted brake can lead to
serious accidents, including the loss of wheels. So it is strongly recommandet
to go to a mechanic shop for this work.
There have been several accidents in past from wrong adjusted brakes. On a car
brake , you can feel when the brake is wrong. But on a trailer brake,
especially with a strong car, you can feel this only in the first seconds of
driving , during acceleration. If you do not feel it in this period the brake
will become hot and will fade. It will come more hot during the next miles and
the grease of the wheel bearings will melt and run out of the bearing. Because
of the fading the driver will not realize that there is something wrong. The
bearing comes so hot now that the axle bolt can melt and fail. Then the wheels
will come off together with the broken axle bolt. This can happen with wrong
adjusted brakes, blocked ( bent ) brake cables or rods or, most common, during
driving with a not released hand brake.
PLEASE LET A MECHANIC DO THIS WORK !
It is your life (And the life of others), it is your car, your plane and your
trailer!
Alfred Spindelberger
Please, can you mail this letter to the soaring news group? I have no access to
this group from Europe.
Thank you, with best regards
Alfred
John Earlywine
_|_
------------()-----------
Fort Wayne, IN
Andy Durbin
> The following reply from Cobra may provide some insight for the change from
> putting the brake adjustment instructions in the front of the trailer. . . .
>
> Hi John!
> The Alko company as the manufacturer of the axle does not recommend that people
> without expierience adjust trailer brakes. Adjusting brakes needs not only the
> knowledge what to do, it also needs some feeling what the right pressure from
> the brake shoes to the brake drum is. A wrong adjusted brake can lead to
> serious accidents, including the loss of wheels. So it is strongly recommandet
> to go to a mechanic shop for this work.
(text removed)
> Thank you, with best regards
> Alfred
>
> John Earlywine
> _|_
> ------------()-----------
> Fort Wayne, IN
I wonder where Alfred thinks I will find a mechanic experienced in the
adjustment of Alko axle brakes, and the particular actuating method
used on Cobra trailers.
Will Alfred want to see my mechanic's credentials before releasing the
instructions? Withholding service instructions is likely to lead to
more, not less, cases of incorrect adjustment.
I hope Cobra agents that may read this thread see the folly of this
situation.
Andy Dubin
new Cobra owner
Leon McAtee
>more, not less, cases of incorrect adjustment.
This would seem to be true, but............
Maybe the directions are so poorly written that it takes a mechanic with
experience in that type of braking system to know what they are really trying
to say.
Also, assuming that you are in the US from the time stamp on your post: Do you
really expect that a manufacturer would release this kind of information
knowing the reading comprehension level of our average high school grad?
Knowing the kind of judicial system we have I wouldn't give out that kind of
info without a signed and notarized copy of the mechanics ASE certification in
hand <G>.
Brakes, even light weight trailer brakes are nothing to second guess. I didn't
get in on the first of this thread but if you are attempting to adjust them
yourself may I respectfully sugest that if you can't figure out how they work,
and come up with a way to properly adjust them, maybe you aren't qualified to
do the work and need to find someone with the proper training and/or
experience.
That being said,
>I wonder where Alfred thinks I will find a mechanic experienced in the
>adjustment of Alko axle brakes, and the particular actuating method
>used on Cobra trailers.
after looking up the system on the Internet there is nothing out of the
ordinary here so, just about any mechanic with a bit of trailer brake
experience should be able to get the job done for you. You might ask to see
their ASE credentials and test score in brakes, if you are the nervous
kind......
Andy Durbin
Leon,
I am not American. I do however reside in America.
I have maintained every vehicle I have owned, and many others, over
the last 30 plus years. I do all the work myself including engine and
transmission rebuilds, suspension rebuilds, and complete brake
refurbishment. I have never undertaken any of that work without first
reviewing the available shop manuals unless I am completely familiar
with the work. I have no doubt that I am competent to adjust the
brakes on my trailer, but would still prefer to read the
manufacturer's recommended procedure before I start.
I am reminded of the fiasco when the BMC 1100 amd 1300 series cars
were introduced in England many years ago. Several qualified
mechanics didn't notice that the rear wheel bearings were tapered
rollers instead of the spaced ball races typically used by that
manufacturer. Tapered rollers tightened to 100lb/ft don't last long,
and there was at least one fatal accident due to wheels and hubs
departing the vehicles.
Andy Durbin
Phoenix,AZ
Leon McAtee
>
>I am not American. I do however reside in America.
>
>I have maintained every vehicle I have owned, and many others, over
>the last 30 plus years.
There's hope. This means that you can probably understand what you read.
Anyone under 30 has to prove it to me.
>I am reminded of the fiasco when the BMC 1100 amd 1300 series cars
>were introduced in England many years ago. Several qualified
>mechanics didn't notice that the rear wheel bearings were tapered
>rollers instead of the spaced ball races typically used by that
>manufacturer. Tapered rollers tightened to 100lb/ft don't last long,
They were not qualified.
And that was more than "many" years ago<G>
It sounds to me like you have enough experience to adjust your own trailer
brakes. I also like to consult the manufactures recomendations but they are
not always available for whatever reason (like no longer in buissness) and you
then have to fall back on your own experience and extrapolate from known good
practices.
If I were you I'd quit worrying about it and just go get the job done......
BTW you wouldn't happen to know where I could find a new floor pan for a '60
Sprite? Not a 1/2 floor, but the whole original kind.
Michael McNulty
>
> There's hope. This means that you can probably understand what you read.
> Anyone under 30 has to prove it to me.
>
With attitudes like this in our sport, do we need to wonder why younger
people are not attracted to soaring?
Bill Staley
Sounds like the wheel brake adjustment has been covered, but, would
appreciate any info on the impulse mechanism. I have had the same
response from Mr Spindelberger when I ask about the directions for
both adjusting the wheel brake shoes, and rebuilding or adjusting the
impulse apparatus in the tongue. Mine goes to both stops with a
resounding thud.
JJ Sinclair
--------------------------------------------------------------
It seems one of our local pilots landed out and didn't have a crew, so he
called back and asked the FBO to, "send someone". The selected "someone",
wasn't too familiar with glider trailers and arrived at the land-out site with
both wheels smoking and the hand brake standing straight up.
Undeterred, Our intrepid pilot, released the brake, shoved his new ASW-27
inside and drove off in the direction of home. Didn't quite make it, a wheel
seperated after the bearings froze and I guess the heat build up did the rest.
It is often said that sailplanes are designed by geniuses to be operated by
idiots, Apparently, Alfred belives that trailers are designed by geniuses, to
be operated by idiots or Yankee idiots anyway.
JJ Sinclair
Chip Bearden
ones in my owner's manual fairly well...sort of. From memory, my
manual directs me to adjust the starwheel adjustor (the toothed thingy
you can see in the hole in the backing plate of the brake) until the
trailer wheel cannot be turned any further IN THE FORWARD DIRECTION,
then back off the adjustor until the trailer wheel turns freely. I
assume this prevents setting the brakes too loose, as when just the
end of one shoe drags on the drum. The reason for the cautionary
language above is that even when the brakes are locked up, the wheels
can still be turned backwards to allow backing up. So all checking for
lock up, slight drag, or free wheeling MUST be by rotating the wheel
in the forward direction.
I've had multiple problems with my Cobra trailer brakes over the
years, with many of them ultimately traced to the overrun tongue. The
tube-within-a-tube design works great until one or both of the two
large plastic bushings in which the inner tube slides (the inner tube
being the one with the hitch on the forward end) are not properly
lubricated and/or swell, or the inner tube corrodes on the lower
surface from water dripping into the tongue or simply condensing and
then being trapped along the lower side by the bushings. After my
trailer sat for a couple of years without being moved much, I had to
remove the inner tongue and smooth off considerable roughness caused
by the corrosion, then open up the clearance of the bushings (which
had somehow swollen) with a small grinding wheel on an extension
shaft, then lubricate everything properly, before I could get my
overrun/surge brake to work correctly. Most older trailers I've seen
seem to have surge brake tube/bushing assemblies that are quite loose,
not tight. This makes sense considering that the inner tube slides in
the bushings every time you brake or accelerate. You can check
grabbing the handle on top of the hitch (not the brake handle) and
rotating the tube back and forth a bit.
By the way, when the inner tube slides easily from fully actuated to
fully extended with a thump at each end, it's time to replace the
damper inside the tongue: it's just a small shock absorber that
prevents the brake from being applied too sharply, which can cause the
trailer wheels to hop off the ground before landing with a screech.
Also by the way (sorry for the length), be careful when replacing
brake shoes: depending on the type of brake, the shoes may not be
symmetrical. Swapping leading/trailing and/or left/right shoes can
allow the end of one shoe to jam, thus causing the brakes to lock up,
melt the wheel bearing grease, etc.
The cable-actuated brake systems used on Komet and Cobra trailers
aren't inherently more complex than conventional automotive hydraulic
brake systems but they are more demanding to set up and adjust
properly, and they require relatively frequent adjustment, at least
when driving them the way we do in the U.S. when one can put 10,000 km
on a trailer in one contest.
Chip Bearden