Cobra trailer brake heating up

[Eric Greenwell[_4_]]

I adjusted the brakes on my Cobra trailer according to the directions from Cobra.
On the first test drive, the right brake drum got very hot in a few miles (about
240 deg F); the left brake drum got up to about 125 deg F.

Neither drum seems to be dragging when I jack up the wheel and spin it. I backed
off the right drum about 8-10 clicks, which reduced the temperature to 175 deg f
(but it was shorter drive). The brake handle still comes up to the correct position.

I'll back off the hot drum another 8 clicks, and see if it still gets hot, but I'm
wondering if I'm missing something here. Does anyone know why it's getting so hot
if it isn't dragging?

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorgliders/publications/download-the-guide-1
- "Transponders in Sailplanes - Dec 2014a" also ADS-B, PCAS, Flarm

http://soaringsafety.org/prevention/Guide-to-transponders-in-sailplanes-2014A.pdf

[David Salmon[_3_]]

At 03:02 03 April 2017, Eric Greenwell wrote:
>I adjusted the brakes on my Cobra trailer according to the directions
from
>Cobra.
>On the first test drive, the right brake drum got very hot in a few miles
>(about
>240 deg F); the left brake drum got up to about 125 deg F.
>
>Neither drum seems to be dragging when I jack up the wheel and spin it. I
>backed
>off the right drum about 8-10 clicks, which reduced the temperature to
175
>deg f
>(but it was shorter drive). The brake handle still comes up to the
correct
>position.
>
>I'll back off the hot drum another 8 clicks, and see if it still gets
hot,
>but I'm
>wondering if I'm missing something here. Does anyone know why it's
getting
>so hot
>if it isn't dragging?
>
>--
>Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email
>me)
>- "A Guide to Self-Launching Sailplane Operation"
>
>https://sites.google.com/site/motorgliders/publications/download-the-guide-1
>- "Transponders in Sailplanes - Dec 2014a" also ADS-B, PCAS, Flarm
>
>http://soaringsafety.org/prevention/Guide-to-transponders-in-sailplanes-2014A.pdf
>

Just a couple of thoughts.
Are the wheel bearings adjusted correctly and greased?
On the brake rod linkage, is the 1mm gap there with the brake off?
Dave

[Hartley Falbaum[_2_]]

On Sunday, April 2, 2017 at 11:03:02 PM UTC-4, Eric Greenwell wrote:
> I adjusted the brakes on my Cobra trailer according to the directions from Cobra.
> On the first test drive, the right brake drum got very hot in a few miles (about
> 240 deg F); the left brake drum got up to about 125 deg F.
>
> Neither drum seems to be dragging when I jack up the wheel and spin it. I backed
> off the right drum about 8-10 clicks, which reduced the temperature to 175 deg f
> (but it was shorter drive). The brake handle still comes up to the correct position.
>
> I'll back off the hot drum another 8 clicks, and see if it still gets hot, but I'm
> wondering if I'm missing something here. Does anyone know why it's getting so hot
> if it isn't dragging?
>
> --
> Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
> - "A Guide to Self-Launching Sailplane Operation"
> https://sites.google.com/site/motorgliders/publications/download-the-guide-1
> - "Transponders in Sailplanes - Dec 2014a" also ADS-B, PCAS, Flarm
>
> http://soaringsafety.org/prevention/Guide-to-transponders-in-sailplanes-2014A.pdf

If your trailer is newer-2000 or so, it probably has the sealed bearings. They can fail, and heat the drum. Are you checking the hub temp, or the drum rim temp? Remove the drum and inspect mechanism of brakes--may be stuck and not backing off.
If it heats to high, too long, you can anneal the axle and it will break off! Find the problem.

[Eric Greenwell[_4_]]

Hartley Falbaum wrote on 4/3/2017 7:22 AM:
> On Sunday, April 2, 2017 at 11:03:02 PM UTC-4, Eric Greenwell wrote:
>> I adjusted the brakes on my Cobra trailer according to the directions from Cobra.
>> On the first test drive, the right brake drum got very hot in a few miles (about
>> 240 deg F); the left brake drum got up to about 125 deg F.
>>
>> Neither drum seems to be dragging when I jack up the wheel and spin it. I backed
>> off the right drum about 8-10 clicks, which reduced the temperature to 175 deg f
>> (but it was shorter drive). The brake handle still comes up to the correct position.
>>
>> I'll back off the hot drum another 8 clicks, and see if it still gets hot, but I'm
>> wondering if I'm missing something here. Does anyone know why it's getting so hot
>> if it isn't dragging?
>
> If your trailer is newer-2000 or so, it probably has the sealed bearings. They can fail, and heat the drum. Are you checking the hub temp, or the drum rim temp? Remove the drum and inspect mechanism of brakes--may be stuck and not backing off.
> If it heats to high, too long, you can anneal the axle and it will break off! Find the problem.

It does have the sealed bearings. I'm checking the temperature at the drum rim.

I'll pull the drum and hope I see something that's easy to fix!


--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorgliders/publications/download-the-guide-1
- "Transponders in Sailplanes - Dec 2014a" also ADS-B, PCAS, Flarm

http://soaringsafety.org/prevention/Guide-to-transponders-in-sailplanes-2014A.pdf

[[email protected]]

Have you checked the overrun mechanism in the tongue, especially the damper? Also the large bushings in the outer tube in which the inner tube slides can get dry (there are grease fittings). The inner tube can rust/corrode. And the bushings themselves (some kind of plastic) can seem to swell, causing binding.

Also the cable actuators inside their housings can rust, binding and causing the brake shoes to not release. You can remove the assemblies at both ends and then add lubricant. Spinning the cable inside the guide can help free things up, also.

If you replaced the brake shoes recently, make sure you got the identical set and that they were installed in the correct orientation so they don't "self energize" to the point where they hang up.

The Alko surge brake works well when everything is in order but there are many things that can go wrong--with disastrous results.

Chip Bearden

[Eric Greenwell[_4_]]

wrote on 4/3/2017 8:08 PM:
> Have you checked the overrun mechanism in the tongue, especially the damper? Also the large bushings in the outer tube in which the inner tube slides can get dry (there are grease fittings). The inner tube can rust/corrode. And the bushings themselves (some kind of plastic) can seem to swell, causing binding.
>
> Also the cable actuators inside their housings can rust, binding and causing the brake shoes to not release. You can remove the assemblies at both ends and then add lubricant. Spinning the cable inside the guide can help free things up, also..
>
> If you replaced the brake shoes recently, make sure you got the identical set and that they were installed in the correct orientation so they don't "self energize" to the point where they hang up.
>
> The Alko surge brake works well when everything is in order but there are many things that can go wrong--with disastrous results.

The overrun mechanism is working properly. I'll check the cable actuators when I
take the drum off tomorrow. The shoes are original, and appear to have plenty of
lining when I look through the little hole in the backing plate, but I'll know for
sure with the drum off.

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorgliders/publications/download-the-guide-1
- "Transponders in Sailplanes - Dec 2014a" also ADS-B, PCAS, Flarm

http://soaringsafety.org/prevention/Guide-to-transponders-in-sailplanes-2014A.pdf

[[email protected]]

It's also possible there are​ brake hardware problem. The tiny areas where the brake shoes rest on the backing plate should have a small amount of high-temp grease (don't want any on the friction material itself or the drum). And the return springs can lose some strength, especially if the brakes have overheated, and fail to pull the brake shoes away from the drums.. There are also other links that can get sticky and cause problems. Most of these things don't occur but when you're looking for a reason for dragging brake shoes, it's another possibility.

Chip Bearden

[John Carlyle]

Eric,

what did you find that caused your brake problem? I'm going to be adjusting my 2000 Cobra trailer brakes soon, and would appreciate any hints you could give.

-John, Q3

On Monday, April 3, 2017 at 11:36:15 PM UTC-4, Eric Greenwell wrote:
>
> The overrun mechanism is working properly. I'll check the cable actuators when I
> take the drum off tomorrow. The shoes are original, and appear to have plenty of
> lining when I look through the little hole in the backing plate, but I'll know for
> sure with the drum off.

[Eric Greenwell[_4_]]

John Carlyle wrote on 4/16/2017 5:24 AM:
> Eric,
>
> what did you find that caused your brake problem? I'm going to be adjusting my 2000 Cobra trailer brakes soon, and would appreciate any hints you could give.
>
> -John, Q3
>
> On Monday, April 3, 2017 at 11:36:15 PM UTC-4, Eric Greenwell wrote:
>>
>> The overrun mechanism is working properly. I'll check the cable actuators when I
>> take the drum off tomorrow. The shoes are original, and appear to have plenty of
>> lining when I look through the little hole in the backing plate, but I'll know for
>> sure with the drum off.

I decided I'd rather to other things than work on a trailer, so today I took it to
the mechanic that does my motorhome repairs. Didn't find anything external, so
tomorrow they'll pull the hubs. I'll let you know.

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorgliders/publications/download-the-guide-1
- "Transponders in Sailplanes - Dec 2014a" also ADS-B, PCAS, Flarm

http://soaringsafety.org/prevention/Guide-to-transponders-in-sailplanes-2014A.pdf

[[email protected]]

Bumping this thread to see what Eric found last year.

My Cobra brake jammed on after a hard stop on the way home from Midlothian last week. Couldn't free it up so disconnected the brake cables at the center brake rod. That freed up the wheels immediately so I drove home. Seemed to stay jammed until I came up the steep driveway. Now it's free, with no indication what might have been wrong. The inner sliding tube and bushings were lubed and moved freely. The brakes and cables were fine; the wheels turned freely after I disconnected the cables even though the tongue was still jammed in the collapsed position.

One odd thing: the lever that comes out of the lower part of the tongue that pulls the brake rod couldn't be tapped loose. No surprise since the inner tube was fully collapsed and thus actuating this lever. But on the way home, I stopped again: tongue was still collapsed but this time when I tapped the lever, it came loose and moved freely. I'm just getting into it now to see what might be amiss but has anyone had this problem?

Chip Bearden

[JS[_5_]]

On Monday, August 13, 2018 at 11:44:43 AM UTC-7, wrote:
> Bumping this thread to see what Eric found last year.
>
> My Cobra brake jammed on after a hard stop on the way home from Midlothian last week. Couldn't free it up so disconnected the brake cables at the center brake rod. That freed up the wheels immediately so I drove home. Seemed to stay jammed until I came up the steep driveway. Now it's free, with no indication what might have been wrong. The inner sliding tube and bushings were lubed and moved freely. The brakes and cables were fine; the wheels turned freely after I disconnected the cables even though the tongue was still jammed in the collapsed position.
>
> One odd thing: the lever that comes out of the lower part of the tongue that pulls the brake rod couldn't be tapped loose. No surprise since the inner tube was fully collapsed and thus actuating this lever. But on the way home, I stopped again: tongue was still collapsed but this time when I tapped the lever, it came loose and moved freely. I'm just getting into it now to see what might be amiss but has anyone had this problem?
>
> Chip Bearden

Chip:
Are you sure there isn't a bullet jammed in it?
Jim

[[email protected]]

> Are you sure there isn't a bullet jammed in it?
> Jim

Hahaha! Anything is possible. :)

[JS[_5_]]

On Monday, August 13, 2018 at 2:54:13 PM UTC-7, wrote:
> > Are you sure there isn't a bullet jammed in it?
> > Jim
>
> Hahaha! Anything is possible. :)

That one particularly possible after the "Dallas" TV show remake...
With the big mystery "Who shot JB?"
Jim

[Michael Opitz]

At 18:44 13 August 2018, wrote:
>Bumping this thread to see what Eric found last year.
>
>My Cobra brake jammed on after a hard stop on the way home
from Midlothian
>=
>last week. Couldn't free it up so disconnected the brake cables at
the
>cent=
>er brake rod. That freed up the wheels immediately so I drove
home. Seemed
>=
>to stay jammed until I came up the steep driveway. Now it's free,
with no
>i=
>ndication what might have been wrong. The inner sliding tube and
bushings
>w=
>ere lubed and moved freely. The brakes and cables were fine; the
wheels
>tur=
>ned freely after I disconnected the cables even though the tongue
was
>still=
> jammed in the collapsed position.
>
>One odd thing: the lever that comes out of the lower part of the
tongue
>tha=
>t pulls the brake rod couldn't be tapped loose. No surprise since
the
>inner=
> tube was fully collapsed and thus actuating this lever. But on the
way
>hom=
>e, I stopped again: tongue was still collapsed but this time when I
tapped
>=
>the lever, it came loose and moved freely. I'm just getting into it
now to
>=
>see what might be amiss but has anyone had this problem?
>
>Chip Bearden
>

JB,

A long time ago, I had a similar problem with the tongue staying
collapsed. It turned out that there was a gas strut inside the tongue
that had failed. Once the gas strut was replaced, all was OK again..
FWIW...

RO

[[email protected]]

On Monday, August 13, 2018 at 8:45:05 PM UTC-4, Michael Opitz wrote:
> JB,
>
> A long time ago, I had a similar problem with the tongue staying
> collapsed. It turned out that there was a gas strut inside the tongue
> that had failed. Once the gas strut was replaced, all was OK again..
> FWIW...
>
> RO

Yeah, my understanding is that it's a gas spring and a damper. The damper function seems to work (i.e., I don't have sharp bumps when the mechanism hits the stops under braking or acceleration, as was true in an early Eberle trailer we had with no damper). But I have no way of measuring it against a spec. I've had the damper/spring out before and it's accessible now so I've already emailed Rex about getting a replacement. I was chased inside by the rain yesterday while the tongue was spread out in the driveway so I haven't been able to examine the interior mechanism closely. Will report back what I find.

Chip Bearden