Cobra trailer skid wheels
Randy Lervold
supported by the hitch and skid wheels on the aft end? And anyone
mounted wheels in place of the skid pads for getting into steep angle
spaces?
Larry Goddard
bought it. They were constantly getting banged about, would develop worn
flat places, etc. After replacing several sets, I put some McMaster Carr
rubber bumper blocks... They are great.... If the rear does go down it
absorbs the shock and they are shorter than the wheels, so they don't hit
things as often.
YMMV
Larry
Eric Greenwell
ra...@rv-8.com says...
Eastern Sailplane, Cobra dealer, told me they are designed to
withstand contact at only the hitch and rear end skid pads. The skid
pads seem to work just fine to protect the trailer, but sometimes
leave gouges in the pavement. Haven't had to replace them in 60,000
miles.
--
Delete the REMOVE from my e-mail address to reply directly
Eric Greenwell
Richland, WA (USA)
Duane Eisenbeiss
mounted to a 1/4 inch plate that is mounted to the bottom of the trailer in
place of the skid. This has worked well for me during the last 30 years or
so. Obviously many trailers get by with just a skid, so the castering wheel
is not REALLY required.
The most usual time to drag the back of the trailer is when coming out of a
gas station. During this action I am usually turning. When the skid is
dragging in a sideways motion, I think that it can put an adverse load on
the trailer, hence the castering wheels.
The wheels protrude only slightly more that the usual skids. In some cases
the Cobra factory skids are not big enough. If you have the stabilizing
jacks on the rear of the trailer and go through a big dip, the jacks can be
damaged.
Duane
"Randy Lervold" <ra...@rv-8.com> wrote in message
news:e84147ce.02111...@posting.google.com...
Caracole
You need to do a search through google about the thread
Cobra tongue breakage
If you love your trailer, or value the contents of your checking
account, you will choose to make a greater effort to find a
flatter slope into a gas station. . . . .
Cindy B
"Randy Lervold" <ra...@rv-8.com> wrote in message
news:e84147ce.02111...@posting.google.com...
Randy Lervold
had no trouble when the weight of the trailer is momentarily supported
by the hitch and the aft edge of the trailer, whether by skids or
wheels.
My reason for the question and concern, and why wheels will be
necessary, is that I intend to store my glider in my garage which has
a steep upward pitch leading down into it. These trailers are so long
that every time it goes in or out it will necessarily be supported by
the wheels and hitch, possibly lifting the main wheels entirely off
the ground. It is smooth concrete so there's no snags, but still, if
the assembly can't be supported in this manner then I'm in trouble.
If anyone has pics of their wheel installation (how they are mounted)
I'd sure appreciate it.
Randy Lervold
Vancouver, WA
"Duane Eisenbeiss" <eisen...@compuserve.com> wrote in message news:<pFHz9.2672$285....@rwcrnsc51.ops.asp.att.net>...
Larry Goddard
coming into the parking lot while you are going out. Castered wheels can
only be presumed to "caster", allowing the trailer to move sideways as well
as forwards.
Larry
Eric Greenwell
> Randy:
>
> You need to do a search through google about the thread
>
> Cobra tongue breakage
>
> If you love your trailer, or value the contents of your checking
> account, you will choose to make a greater effort to find a
> flatter slope into a gas station. . . . .
Is there any evidence to suggest that is what caused the tongues to
break or crack? Everything I heard indicated it was fatigue, not
stress.
JJ Sinclair
>Is there any evidence to suggest that is what caused the tongues to
>break or crack? Everything I heard indicated it was fatigue, not
>stress.
Dale Bush cracked his cast trailer hitch when the jack wheel hit as he drove
out of a gas station. If *fatigue* is the cause, why are the new tongues
failing? I would expect the older tounges to show a fatigue problem first.
JJ Sinclair
Duane Eisenbeiss
news:20021111235202...@mb-md.aol.com...
......... If *fatigue* is the cause, why are the new tongues > failing?
JJ Sinclair<<<
Have you heard of "new" Cobra tongues failing? If so, please start a new
thread and lets us know what you know about the failures.
Duane
JJ Sinclair
>Have you heard of "new" Cobra tongues failing? If so, please start a new
>thread and lets us know what you know about the failures.
The failuers that occurred a couple of years ago were on new trailers, less
than two years old and they were all being towed behind motor homes. I'm not
referring to the replacement tonges which Spindelburger shipped out as a fix.
He also posted a detailed scenario about the cause which he blamed on the Motor
home and trailer combination dragging the jack & wheel as they left a gas
station. Makes sense to me, the jack drags as the rear wheels of the motor home
continue on down into the curb that is located at most gas stations. This puts
considerable force on the tongue (down on the hitch & up on the tongue) The
jack & wheel acting as a fulcrum. Do this 10 or 20 times and I can believe
metal fatigue failure of the tongue. I can not believe that *new* tongues would
be failing without considerable force being applied to them in a short period
of time (less than two years) We have been towing Cobra trailers for 30 years
or more. I ask the question, *why aren't the older tongues failing first. if
the cause is just metal fatigue* ????
JJ Sinclair
JJ Sinclair
probably should be saying *Metal Stress*. Metal Fatigue conjures up the vision
of those brave fire tanker pilots making a drop in the Sierras. The wing of
their 30 year old C-130 failed because of metel fatigue caused by thousands of
cycles over many years. Metal Stress, on the other hand can occur in a very
short period of time by simply bending the metal past its yield point and it
will crack and fail in as little as 10 or 20 cycles.
I just did it with a push rod held in a vice. The mild steel push rod was much
smaller than our Cobra tongues.but its diameter and wall thickness were
proportionately similiar to the Cobra tongue. When I bent it past its yield
point, the compression side formed a little bulge. With repeated cycles a small
crack appeared on one side of the bulge after only 7 cycles. A few more cycles
and the crack went half way around the tube. On the twenty-first cycle it broke
in two pieces.
So, what can we do to prevent this from occuring? First look at your jack wheel
and or skid plate below the hand brake. If it has skid marks on it, then you
got the problem. The first thing I did was to remove the jack & wheel when
traveling. Then I noticed the hand brake skid was scraping. You can raise the
ball height (hitch with a shorter drop) This will cause the far end of the
trailer to drag, but at that distance from the tongue, it can take it and won't
cause tongue failure. Or. I placed a heavy duty caster on the bottom of the
bolt that holds the ball. NOTE, this is on the motor home side, placing a
caster or skid on the trailer tongue will only provide a new fulcrum around
which to bend your tongue! When I exit the gas station the caster hits first
and doesn't allow the rear end of the motor home to continue to drop as the
rear wheels roll through th curb.
JJ Sinclair
Mike Koerner
Thanks for your posts on trailer tongues. You remind me that I have not done
my civic duty in detailing my experience and recommendations on this
subject - which are very different from yours.
My recommendations are that the trailer chains be repositioned so that the
BODY of the trailer is tied to the tow vehicle and that trailer tongues be
inspected AT LEAST once each season.
You said "The failures that occurred a couple of years ago were on new
trailers, less
than two years old". Apparently you were not including mine.
Two years ago, as a result of a post on this news group by Ed Byars, I went
out and checked my tongue with a flashlight. It was cracked clean though
over 160 degrees of the circumference of the tube! The crack was centered on
the bottom of the tube and located immediately aft of the welded bracket
that holds the brake mechanism.
My Cobra trailer was 12 years old at the time and had many miles on it, most
behind a motor home with a stiff suspension and long arm from the rear
wheels to the ball.
The alarming aspect of this discovery was not the imminent failure but the
potential hazard. The chains and wheel break safety wire were attached to
the trailer tongue in front of the crack!
I didn't have time to send the tongue back to Spindelburger or section it to
establish the failure mode. I had it welded up at a local shop, with a
couple of doublers added for good measure, and was back in the air the next
weekend.
I'm not without opinions however. I don't believe the damage related to
dragging the tongue wheel, though I have ground a couple those off just for
good measure. The tongue wheel crushes and its axel fails before damaging
the tongue. Also, there was no evidence of yielding in compression at the
point of failure. The edges of the crack were square.
I believe it's a fatigue failure related to millions of cycles with a heavy
tow vehicle bouncing down rough roads. Our trailers, though not heavy, are
long and thus have a huge rotational inertia about their axel.
If there was an instigating event it would have been from dragging the
trailer's tail. This would put the bottom of the tongue in tension,
consistent with the crack I saw. But I don't think this is necessary. The
failure could be the result of fatigue acting on a stress concentration in
the weld-effected region just behind the brake bracket.
The important thing is that I'm not worried about it any more. I clamped a
couple of 3/8 inch steel plates under the protruding end of the threaded
fasteners that secure the forward end of the tongue to the trailer. These
plates, about 4 inches long and two inches wide, extend forward clear of the
trailer body and have eyeholes for chain attachment. And I've used
heavy-duty chain and hardware, no cast iron hooks. So no matter what happens
to the tongue, the trailer stays with the tow vehicle.
Thinking I was going to save someone a lot of grief, I checked every trailer
at Crystal, Cal City and Minden last year. None showed any evidence of
cracks. So this is a fairly rare event.
And I wouldn't expect this problem to be unique to Cobra trailers (it looks
like newer models have substantially larger tongues, by the way).
People with the older hardware should modify their chains to be sure they
have heavy-duty hardware tied directly to the trailer body. And everyone
should inspect their tongues at least once each season.
By the way, your test with the control rod was really quite different.
Although it may have looked proportionately the same as a trailer tongue,
the deflections you imposed were proportionately far greater than anything
we see on the road. The area you referred to as a "Little bulge" is
buckling. There was no buckling on my trailer.
You may wonder that I would go to such effort to correct your post while
others advocate using both hands to cover your face while in a spin, the
elimination of the Soaring Society of America, etc. I can think of no excuse
for this. I'm sorry. Thanks again for your posts.
Mike Koerner
JJ Sinclair
Lets review what we know about the broken tongue problem:
++ Most have occured with trailers being towed behind motor homes,
++ Several have occured on fairly new trailers.
++ Most show dragging marks on the jack wheel or brake skid plate.
You probably did have *metal fatigue*, but how do you explain the failures on
several new trailers? They didn't bounce down the road for 12 years. Why did
they fail?
Your suggestion to attach safety chains directly to the body of the trailer is
an excellent idea and we should all do that.
JJ Sinclair
JJ Sinclair
related to
>dragging the tongue wheel, though I have ground a couple those off just for
>good measure. The tongue wheel crushes and its axel fails before damaging
>the tongue
The fact that your jack wheel DRUG twice shows me that your tongue was put
under stress on at least two occasions, The question is, How much stress?
Where would we expect to see any signs of over stressing the tongue? At the
edge of welds on the tongue where the structure is strengthened by adding a
bracket and weakened at the edge of the weld due to problems associated with
the welding process.
I would suggest that the stress was enough to concentrate at the weld and
initiate the failure mode.
JJ Sinclair
Eric Greenwell
jjgl...@aol.com says...
> Eric wrote>>>>>>>>>>>>>>
> >Is there any evidence to suggest that is what caused the tongues to
> >break or crack? Everything I heard indicated it was fatigue, not
> >stress.
>
> Dale Bush cracked his cast trailer hitch when the jack wheel hit as he drove
> out of a gas station.
This would be overstressing, not fatigue, which typically involves at
least several hundred cycles, and often 100,000 or more. I'd expect a
cast parts to fail more often with this kind of stress than the forged
sheet hitch connectors used by most trailers.
Eric Greenwell
jjgl...@aol.com says...
> Good post Mike,
>
> Lets review what we know about the broken tongue problem:
>
> ++ Most have occured with trailers being towed behind motor homes,
>
> ++ Several have occured on fairly new trailers.
>
> ++ Most show dragging marks on the jack wheel or brake skid plate.
>
> You probably did have *metal fatigue*, but how do you explain the failures on
> several new trailers? They didn't bounce down the road for 12 years. Why did
> they fail?
I remember being told the "new" tongues that had the cracking appear
in a year or two were made differently than the older tongues.
Apparently, Alko (the tongue manufacturer) made a design change (but
not a specification change) that made the tongues more likely to fail
in our particular use. The newest Cobra trailers I've seen use a
rectangular section tongue, not a round one.
> Your suggestion to attach safety chains directly to the body of the trailer is
> an excellent idea and we should all do that.
This is also Cobra's recommendation. And they should be big chains,
too, because the trailer will not be stable once the tongue breaks,
and a whipping trailer can exert considerable force.
Eric Greenwell
jjgl...@aol.com says...
>
> The fact that your jack wheel DRUG twice shows me that your tongue was put
> under stress on at least two occasions, The question is, How much stress?
>
> Where would we expect to see any signs of over stressing the tongue? At the
> edge of welds on the tongue where the structure is strengthened by adding a
> bracket and weakened at the edge of the weld due to problems associated with
> the welding process.
>
> I would suggest that the stress was enough to concentrate at the weld and
> initiate the failure mode.
I'm not a metallurgist, though I did work with them for 30 years.
Fatigue cracking at welds occurs under tension. My understanding is
compressive forces, which is what you would get from dragging the
brake protection skid, would not cause the kind of failures we saw at
the welds.
Some of the failures occurred where the tongue entered the trailer,
where there are no welds, and would not have been subjected to high
forces from dragging the brake handle skid. Perhaps you are not
including these failures in the discussion, but only the ones failing
at the welds.
Eric Greenwell
jjgl...@aol.com says...
the failures.
>
> The failuers that occurred a couple of years ago were on new trailers, less
> than two years old and they were all being towed behind motor homes. I'm not
> referring to the replacement tonges which Spindelburger shipped out as a fix.
> He also posted a detailed scenario about the cause which he blamed on the Motor
> home and trailer combination dragging the jack & wheel as they left a gas
> station. Makes sense to me, the jack drags as the rear wheels of the motor home
> continue on down into the curb that is located at most gas stations. This puts
> considerable force on the tongue (down on the hitch & up on the tongue) The
> jack & wheel acting as a fulcrum.
The forces you describe would greatest on the hitch back to the front
of the bracket that protects the brake handle. As best I can remember,
none of the cracking or failures occurred in this area.
Silent Flyer
not sure what you call them in the USA - just trailers ?) The common
factor was that they were all being towed by motor homes or off-road
vehicles.
The cause is claimed to be excessive vibration transmitted to the caravan
chassis by the tow hitch being attached to the more rigid chassis of this
type of towing vehicle.
Is there a clue here ?
DB
JJ Sinclair
I conclude from your recent posts, that you don't believe any of the tongue
failures were caused by dragging associated with entering / leaving gas
stations. At least two of us disagree, Cobra manufacturer and me. Alfred
Spindelberger wrote>>>>
"The tongue may be bent from the car at too steep turns or if the trailer
tongue area is "high centered". The long overhang of "campers" can cause the
small wheel on the tongue to drag on the ground when over uneven terrain or
entering gasoline stations and this can cause excessive stress to the tongue."
I have seen this exact scenario with my trailers and the trailers of my
customers that brought them to me to repair after cracking caused when entering
/ leaving gas stations.
JJ Sinclair
Chip Bearden
When my trailer tongue broke (right where it entered the trailer), the
trailer did indeed whip back and forth. My sister was driving the car
behind us and said it was pretty dramatic. Fortunately the wide-body
van I was driving was stable and I got it stopped without drama.
Noteworthy was that what kept things together was the surge brake
actuating rod. I'm not advocating chainless trailering (I added them
immediately after this incident) but if the break occurs aft of the
brake handle, you might get lucky as I was.
The reason the tongue broke, however, was accelerated fatigue caused
by stress concentration. A few years before, another driver had
jackknifed the trailer in a minor incident. The tongue had been bent
slightly, then straigtened, and a small vertical "fin" welded along
the bottom of the tube by a backyard mechanic "just to make sure."
This section of the tube--which was not allowed to flex like the rest
of the tongue--concentrated the bending stress right at the point
where the tongue enters the trailer (and is inserted into another,
larger tube). And after a few years, it broke.
Message: Others have cautioned about introducing stresses or
heat-treat weaknesses when welding. Be very careful when "reinforcing"
your trailer tongue not to introduce a failure point from repeated
stress and bending.
The second time the tongue broke (I've got lots of stories), was when
the front attachment point of the large tube INSIDE the trailer failed
in tension. This allowed the tongue to pivot up around the rear attach
point and the front of the trailer to settle down until it came to
rest on...you guessed it...the faithful surge brake actuating rod. In
this case, the trailer went right on trundling behind the vehicle with
no sign anything was amiss--until smoke began pouring off the hubs
because the brake rod had actuated the trailer brakes.
The temporary fix was to raise the front of the trailer and wrap one
of the safety chains around the junction of the tongue and front cross
member. That allowed us to trailer into the welder's shop where he
added a large U-bolt to tie the front of the tube into the front cross
member without introducing any other welding-related weaknesses. This
was a Komet trailer, 1978 vintage, by the way; anyone pulling one of
those would be well advised to check the weld inside the front of the
trailer where the outer tongue tube is welded to the front bracket.
And if it were me, I'd go ahead and add a U-bolt anyway.
Chip Bearden
Eric Greenwell
jjgl...@aol.com says...
> Eric,
> I conclude from your recent posts, that you don't believe any of the tongue
> failures were caused by dragging associated with entering / leaving gas
> stations.
None of the failures I heard about seemed related to the loads
dragging might impose, based on the description of the crack
appearance and it's location.
> At least two of us disagree, Cobra manufacturer and me. Alfred
> Spindelberger wrote>>>>
> "The tongue may be bent from the car at too steep turns or if the trailer
> tongue area is "high centered". The long overhang of "campers" can cause the
> small wheel on the tongue to drag on the ground when over uneven terrain or
> entering gasoline stations and this can cause excessive stress to the tongue."
Do you have full context version of this? I couldn't find anything on
the Cobra web site.
I agree the tongue can be bent by this dragging, but I don't think it
explains cracking on the bottom of the tongue, nor the way the cracks
looked. For example, the crack on my tongue looked like a fatigue
failure, not a compression failure.
> I have seen this exact scenario with my trailers and the trailers of my
> customers that brought them to me to repair after cracking caused when entering
> / leaving gas stations.
Where were these cracks - top or bottom? Was the tongue examined
before the gas station incident, or only afterwards? If only
afterwards, I'd suggest the crack was developing before the gas
station incident, and only noticed when the incident prompted
inspection.
Despite my reservations about the "dragging" theory, I like the idea
of the idea of a wheel or skid on the hitch to reduce the chances of
dragging the handbrake skid. I'm more concerned about the forces
imposed on the coupler than the tongue, however, but this would
address both issues.
JJ Sinclair
I found Spindslberger's letter on Google by typing in *Cobra Trailer Tongues*
In 30 years of towing trailers, I have had two tongues fail completely (not
Cobra) and seen a complete failure and a cracked hitch on customers trailers.
I have seen the stress that was applied to the tongue when the brake guard drug
and the rear wheels of my motor home continued down to the curbe, as I left a
gas station. The gas station scenario is the only way I can resolve the
failures of very low mileage trailers. Classical metal fatigue would normally
take years of use to appear. I believe these low mileage failures were caused
by over stressing the tongue in a gas station and then the weakened tongues
failed, showing *metal fatigue* symptoms.
JJ Sinclair
Eric Greenwell
jjgl...@aol.com says...
> Eric,
> I found Spindslberger's letter on Google by typing in *Cobra Trailer Tongues*
I didn't find the one you quoted, but I found a similar one, posted by
Tim Mara on Aug 8,2000. I believe this explanation by Cobra is not
what they ultimately came to believe was the cause of the rash of
failures we had in fairly new trailers. I recollect it was later that
Cobra discovered the change in the tongue manufacturing (by Alko), and
had an opportunity to physically examine tongues that had failed.
> In 30 years of towing trailers, I have had two tongues fail completely (not
> Cobra) and seen a complete failure and a cracked hitch on customers trailers.
> I have seen the stress that was applied to the tongue when the brake guard drug
> and the rear wheels of my motor home continued down to the curbe, as I left a
> gas station. The gas station scenario is the only way I can resolve the
> failures of very low mileage trailers. Classical metal fatigue would normally
> take years of use to appear. I believe these low mileage failures were caused
> by over stressing the tongue in a gas station and then the weakened tongues
> failed, showing *metal fatigue* symptoms.
If the damage was only related to the "gas station scenario", I would
expect many more broken tongues over the last 20 or so years, not the
rash of that we had back in 2000.
A few of the failures might have been related to the "gas station
scenario". I'm not disputing that, and I think it is worth protecting
against, since adding a wheel or skid at the vehicle hitch is cheap
and easy, as you mentioned.
The likely reasons for the fatigue cracks appearing fairly soon are
the change in tongue manufacturing and the increased number of
motorhomes in use by glider pilots.
Without examining the failed tongues, the failure mode can't be
determined. So, as surely the last two participants, we should
probably give the thread a rest until we have some new information.
Incidentally, when I typed in *Cobra Trailer Tongues* into Google as
you recommended, I didn't find Alfred's remarks; instead, an amazing
(and large) assortment of references to dragons and sex stories came
up! Give it a try. It worked much better when I typed the reference
into Google Groups.
JJ Sinclair
The only thing I would add, would be that the *Gas Station* scenario is not a
*one time thing*, if the motor home & trailer combination is susceptible to
dragging in the tongue area, it will happen again and again, resulting
in-----------------------------------
--------------------------------------------------------------------------
------Knock it off, JJ, They have heard it all, at least three times.
OK, Boys & Girls, Let's review what we have learned (some of this will be on
the test)
++ Inspect your tongues regularly, especially if towed behind a motor home.
++ Install heavy duty chains that attach directly to the trailer frame.
++ Remove hand crank before towing trailer.
++ If you are concerned about the *Gas Station Scenario*, consider installing
rollers or casters on your motor home that will contact the sloping driveway
just before your trailer tongue draggs.
JJ Sinclair