Older Cobra trailer brake oscillation

On 9 Mrz., 18:45, Brian Bange wrote:
Alfred,

I towed the trailer home with just the wings in it. I left the
fuselage in the hangar. That would account for about a 300
pound lighter load. Would this cause my problem?

The trailer was probably built in 1983 and has housed an
ASW20B since it was new, as nearly as I can tell. It has
P165/80R13 tires on 4 lug wheels.

Thank you for your very detailed post.

Brian Bange
At 17:11 09 March 2009, wrote:



On 8 Mrz., 04:30, Brian Bange *wrote:
I just towed my new (to me) Cobra for the first time and
when I
brake even moderately, the tires lock up on the trailer, then
let
go, then lock up in a repetitive cycle of about 3Hz. What do I
do?

Brian

HGi Brian
In your case, most likely the wheels are too big in diameter.
Overrunning brakes are a self regulating system, and they are
servo-
sustained.
Self regulating means, that a trailer with a certain weight
needs a
certain diameter of the brake drum and a certain diameter of
the
wheels.
The dynamic wheel diameter for a trailer with wheels with 4
bolts can
be between 572 and 602 mm, so the difference between
minimum and
maximum diameter is just slightly more than one inch.
The dynamic wheel diameter is the diameter *with 100 km/h (
about 60
miles an hour.) Here the wheel is about 12 mm( 1/2 inch)
more in
diameter as the trailer resting.
As mentioned before, the brake is servo sustained. This is
done with a
certain position of the brake shoes *inside the brake drum. So,
a
certain amount of the
force of the turning wheel is used to sustain the brake force.
If your wheels are too big in diameter, this servo system just
receives too much force from the wheel and overreacts,
blocking the
wheel. This means no force anymore to the servo brake, =
brake opens.
Wheel turns again = too much force to the servo brake =
blocking
again.........
If you tell me the wheel size you currently use and if you have
a
brake drum with 4 or 5 lugs, I can give you some advise
The whole system is designed to work perfect at 90 % of the
maximum
weight of the trailer. It will run up too light and brake too weak
at
50 % and it will run up hard ( and brake weak again ) with
100% of the
trailers maximum weight.
* * * * Alfred- Zitierten Text ausblenden -

- Zitierten Text anzeigen -

Hi Brian!
It seems,that I was wrong with my assumption - your wheels are the
right size.
So, it may be an extremly worn brake lining, may be together with a
wrong adjustment of the brake rod.
Please check first the lenght of the brake rod and look at the
linings. Use a light to see if the lower edge of the chamfer of the
lining is still visible.If not, new linigs are needed.
Please do not hesitate to contact me if you have no efforts.

Best regards, Alfred