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Cobra Trailer Brakes



 
 
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  #11  
Old May 20th 19, 07:26 PM posted to rec.aviation.soaring
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Default Cobra Trailer Brakes

On Sunday, May 19, 2019 at 6:00:59 AM UTC-7, Nelson Howe wrote:
On Saturday, May 18, 2019 at 6:23:27 PM UTC-4, wrote:
Having just installed new brake drums, bearings, backing plates, and brakes on my 2011 year Cobra (New because I burnt up the original ones on the way to Perry, a long post on that later) I am quite sensitive to how hot the brakes should get in normal operation.

I am sure that all the new items were installed properly and the adjustments were checked and are correct.

Taking the trailer from home to SCOH is a 60 mile trip. The first half is rural but with quite a few stop signs and traffic lights. I stopped several times to check and the brake hubs were hot (and I would expect some heat due to friction, physics, and all that) but how hot is too hot? I could put my finger on the hub but didn't want to keep it on much longer than a second. By comparison the brake rotors on the tow vehicle were considerably hotter than the trailer brake drums.

At one checking stop I jacked up each side and the wheels turned freely with no sound of brakes rubbing.

The second half of the trip was open highway and upon arrival at the field the brake drums were still warm, but considerable less than the stop and go portion of the trip.

The trailer tongue compresses when stopping and expands when moving in what I assume is the normal manner. I did test how much force it takes to depress the movable portion of the tongue, unhitched from the tow vehicle, and it seemed to me about 75 pounds. When released the tongue then moved out to its full extension but did take about 10 seconds to do that.

So, having said all this, is this normal operation or is something amiss?

Next time I tow the trailer I will take actual temp readings with a thermal scanner and report actual temps.

DVM
ASG29E BV


I had to replace the pads and bearings last year because of overheating. Even after the replacement I found my hubs getting pretty warm on a short drive. We then removed the bowden cables, lubed them, got them moving freely and easily, and reinstalled them. That fixed the problem and the hubs now feel just a little warm to the touch after driving, not hot. I have a new set of bowden cables I plan to install in the future.

Nelson


My experience is the same as Nelson's. I replaced the damper and the shoes, but only after cleaning and lubricating the bowden cables really well (but without removing them), making sure friction was reduced, actuation was smooth and the whole system adjusted - only then I experienced both confident braking without too much heat build up even after downgrades. They heat up the most in city stop and go traffic.

David
  #12  
Old May 20th 19, 08:08 PM posted to rec.aviation.soaring
AS
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Default Cobra Trailer Brakes

On Monday, May 20, 2019 at 7:10:38 AM UTC-4, Charlie M. (UH & 002 owner/pilot) wrote:
It wouldn't hurt to watch temps. Tire pressure will change by about 1PSI/10*F.


Would it be conceivable to design a hub cap, which acts like centrifugal air pump to cool the hubs? Or install a scoop under the trailer to funnel air towards the hubs?
I have a TPM system installed which is also monitoring the tire temperature and I am impressed by how sensitive it is in both regimes.

Uli
'AS'
  #13  
Old May 20th 19, 08:40 PM posted to rec.aviation.soaring
Charlie M. (UH & 002 owner/pilot)
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Default Cobra Trailer Brakes

A more open wheel with some hubcaps could do some venting. There are some OEM car wheels (Corvette and others) that do exactly that.
Scoops/channels are likely to get torn off, especially a retrieve in a field that is soft, rough or tall grass.

While I have not made it a habit to check trailer wheel temps when towing, if the surge brake actuator is lubed and not bent, there should be almost no brake usage. Thus, no heat generated.
  #14  
Old May 20th 19, 09:37 PM posted to rec.aviation.soaring
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Default Cobra Trailer Brakes

As far as I can tell, every time that the tow vehicle uses its brakes, the brakes on the trailer engage. Is this not the way it is supposed to work?

DVM
  #15  
Old May 20th 19, 09:47 PM posted to rec.aviation.soaring
AS
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Default Cobra Trailer Brakes

On Monday, May 20, 2019 at 4:37:20 PM UTC-4, wrote:
As far as I can tell, every time that the tow vehicle uses its brakes, the brakes on the trailer engage. Is this not the way it is supposed to work?

DVM


No - only if the towing vehicle decelerates fast enough so that the trailer does overcome the force of the damper in the tow bar will the brakes be engaged. If you feel a subtle 'bump in the rear' every time you tap the brake, check/replace the damper.

Uli
'AS'
  #16  
Old May 20th 19, 10:00 PM posted to rec.aviation.soaring
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Default Cobra Trailer Brakes

How much force does it take to compress the trailer tongue. My estimate was about 75 pounds. Does this seem about right?

DVM
  #17  
Old May 20th 19, 11:19 PM posted to rec.aviation.soaring
AS
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Default Cobra Trailer Brakes

On Monday, May 20, 2019 at 5:00:45 PM UTC-4, wrote:
How much force does it take to compress the trailer tongue. My estimate was about 75 pounds. Does this seem about right?

DVM


I would guess that depends on the weight of the trailer. Mine is a two axle one with a max weight of around 3,500#. I would imagine that my damper requires more force to collapse than one in a trailer for a 1-26. I tried to compress my tow bar by hand and couldn't.
Only if I have to do a 'panic stomp' on the brake do I feel the bump in the rear. The three grease fittings get a few shots every year and that seems to be all required to keep it happy.

Uli
'AS'
  #18  
Old May 20th 19, 11:42 PM posted to rec.aviation.soaring
JS[_5_]
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Default Cobra Trailer Brakes

On Monday, May 20, 2019 at 3:19:55 PM UTC-7, AS wrote:
On Monday, May 20, 2019 at 5:00:45 PM UTC-4, wrote:
How much force does it take to compress the trailer tongue. My estimate was about 75 pounds. Does this seem about right?

DVM


I would guess that depends on the weight of the trailer. Mine is a two axle one with a max weight of around 3,500#. I would imagine that my damper requires more force to collapse than one in a trailer for a 1-26. I tried to compress my tow bar by hand and couldn't.
Only if I have to do a 'panic stomp' on the brake do I feel the bump in the rear. The three grease fittings get a few shots every year and that seems to be all required to keep it happy.

Uli
'AS'


To order the correct tongue damper for a Cobra requires sending the information stamped on the trailer's AlKo tongue to Ralf at Spindelberger.
This would imply there are different dampers, different forces.
(several are in stock at W+W)
When the damper is REALLY gone, you'll feel and hear a loud clunk on starts and stops.
Jim
  #19  
Old May 21st 19, 12:09 AM posted to rec.aviation.soaring
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Default Cobra Trailer Brakes

I have contacted Cobra and they told me that my trailer has 2051 brakes and the overrun device is 161S. However; that still does not tell me what the compression force is? As noted above the trailer tongue compresses with i'm guessing 75 pounds of force and then extends out to its full extension in about 10 seconds.

DVM
 




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