Warning re Hitches - Wrist Twisters
 
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post #1 of 8 Old 09-29-2018, 02:19 PM Thread Starter
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Warning re Hitches

Dear All,
I want to pass on my recent experience.
As part of my garage build, I had to clear everything out, including the numerous motorcycles, basically a gaggle of old SOHC CB750s and my dormant track bike.
Seeing as my Kendon motorcycle trailer can only handle two at a time, it meant 3 trips to our son's house to get them into his garage.
The third trip just had the track bike on it.
Now get this, their street is a wee uphill gradient, so after light braking I stopped along the curb.
I glanced in the mirror and noticed the trailer angle seemed weird, as in tipped downwards at the front.
Hmmmmmm, how could that be?
I checked immediately, and to my horror, discovered that the hitch mounting bolts and their rectangular load distribution plates had broken through the aluminum cross beam our Maxima has behind the bumper molding, and was levered down such that the ball stud was resting on the pavement.
Yikes!!!!
The hitch was a Class 1, sort of T shaped, with the leg projecting forward to the spare wheel well, and the top of the T bolted to a structural cross beam.
The hitch was designed so that the bulk of the forces were being transferred to the structural beam.
The hitch's forward strut which was bolted to the spare wheel well floor was fine, although the 'floor was distorted some by the strut having levered against it as the back of the hitch went down.
The hitch was installed almost 15 years ago.
My examination indicates galvanic corrosion of the dissimilar metals as aggravated by a road salt and crevice resident water created electrolyte, as being the root cause.
(OK, one could say the root cause was the stupidity of bolting steel to aluminum for such an application, environmental factors included.)

IF you have any kind of hitch whose mounting relies upon bolting to aluminum structural components of your vehicle, check it for soundness!

I was so lucky, mine broke free with a light trailer load, under gentle braking from less than 30 mph.
I didn't even want to contemplate the result of such a hitch failure with fully loaded trailer at highway speeds and heavy braking.

This is my contribution for the day!

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post #2 of 8 Old 09-29-2018, 03:01 PM
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Aussie style tow hitch. The draw bar is bolted to a steel ute chassis.
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post #3 of 8 Old 09-29-2018, 04:18 PM Thread Starter
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Quote:
Originally Posted by Islandboy View Post
Aussie style tow hitch. The draw bar is bolted to a steel ute chassis.
Eyeballing it I'd say that past the ideal steel:steel, just watch out for high tow and tongue weights.
That said based on the net shape and size of the angular tie in and assuming the only other locating point is a symmetrical one on the other side.

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post #4 of 8 Old 09-29-2018, 04:41 PM
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I agree with in regards to corrosion. What might start out within spec, many years of corrosion can undo. Here is a pic of the mount point on my ute. Over 15yrs old, some paint missing and rust. I'm not sure how much steel you lose per year to rust but give that join another 10yrs untreated and it's going look a bit thin.
Given your mix of dissimilar metals the rate of loss of one metal was going to be fast. I've seen aluminum boats rot very quickly where a steel fish hook has sat unnoticed.
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post #5 of 8 Old 09-29-2018, 06:53 PM Thread Starter
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Quote:
Originally Posted by Islandboy View Post
I agree with in regards to corrosion. What might start out within spec, many years of corrosion can undo. Here is a pic of the mount point on my ute. Over 15yrs old, some paint missing and rust. I'm not sure how much steel you lose per year to rust but give that join another 10yrs untreated and it's going look a bit thin.
Given your mix of dissimilar metals the rate of loss of one metal was going to be fast. I've seen aluminum boats rot very quickly where a steel fish hook has sat unnoticed.
Yours looks pretty good for its age!
Very interesting about the steel hook on aluminum boat, and no doubt warm humid salty sea air would help things along.

The reality is, I never paid attention to the hitch, probably because I didn't do the installation. If I'd done the install, I'd have realized that beam was aluminum and hopefully thought about what I was doing.
Any other Class 1 hitch will attach the same way.
I need to investigate Class 2 hitches, but not for their rating, and instead, just what they attach to.
Of course, exacerbating all this is my propensity for keeping stuff forever...........

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post #6 of 8 Old 09-29-2018, 07:28 PM
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My aluminum runabout I got secondhand. About 10yrs old. I noticed some small holes near the bow, above the water line. Inside there is an aluminum shelf. Jammed between the shelf and boat hull I found a steel 44gal drum lid. The boat hull on the inside has a ring of corrosion where the drum lid was sitting. Some holes eaten all the way through.
I wonder in your case if the two metals had been separated by a gasket of sorts if that would've helped.
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post #7 of 8 Old 09-30-2018, 07:42 AM Thread Starter
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Quote:
Originally Posted by Islandboy View Post
My aluminum runabout I got secondhand. About 10yrs old. I noticed some small holes near the bow, above the water line. Inside there is an aluminum shelf. Jammed between the shelf and boat hull I found a steel 44gal drum lid. The boat hull on the inside has a ring of corrosion where the drum lid was sitting. Some holes eaten all the way through.
I wonder in your case if the two metals had been separated by a gasket of sorts if that would've helped.
Very interesting findings re your boat!

I think you are spot on that a gasket would've helped my case some.
Probably some high density sheet plastic to act as an insulator.
As well as wadding it all up with some very heavy grease.

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post #8 of 8 Old 09-30-2018, 02:35 PM
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That road salt is a killer for metal, we don't need it over here, but when I was living in the UK during the eighties, I was shocked by the amount of corrosion on the cars.

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