Stress cracks in aluminum framed trailer

[Rockin]

I was looking at horse trailers today and the salesman said they see a lot of stress cracks in the frame of all alumnimum horse trailers. I am curious if this is valid or not.

I've also hear there are electrolysis problems on a trailer made with a steel frame and alumnimum skin. Is this valid?

[tanker]

Having 35 years working with aluminum tanks/trailers, makes me wonder about those stress cracks in the frame. When aluminum cracks, it will continue to travel, unless it is stopped. To stop a crack you can drill a small 1/4" hole at the traveling end of a crack, this will put a radius at the end and the crack can't travel. However the crack should be ground, or gouged out cleaned both sides and welded. If you just weld the crack it will crack again, if you don't drill stop the crack, it will crack just ahead of the welding process. Cleanliness is a must or you will have contamination. Aluminum is always in a state of oxidation, so clean it with a stainless steel wire brush (that was never used with any other metal), or wash it with acid.
If unpainted steel is placed side by side with aluminum you will have electrolysis, which will eat away the aluminum, and you will have a white powder, and flaking aluminum. You can put properly painted steel, or use duct tape, or a plastic film between the two dissimilar metals.
Some times aluminum frames crack because of poor design, you cannot build a steel frame and an aluminum frame the same way. Different stress levels. I would look at the history of the manufacturer and see how long, and how many aluminum frame trailers they have been making. The one in question, may have been one of the first aluminum framed trailers thay made. You don't want to get stuck with someone else's trouble. Even if you were to weld gussetts at cracked area's you may make it worse, by being to stiff and not allowing normal flexing. Believe me, my company had its up's and down's in its 57 year history when it came to any new design on its aluminum units. I would check and see if you can find any others of the same make and vintage and see if their are any cracks.
I don't know if DOT would ever stop a horse trailer in some states, but they won't allow any stress cracks on big rigs.
I myself would stay away from a trailer with frame cracks, the salesman may say its normal, but is he an expert, or trying to make a sale.
Maybe "Dr. Lee" could chime in on this stress issue. [img]smile.gif[/img]

[Rockin]

Tanker, thanks for the info. I'm also curious if there is a history of cracks in aluminum framed trailers, and if the cracks have led to failures.

[BuffaloGuy]

I've done a lot of towing with aluminum stock trailers and found that the more gravel roads and cattle gaurds it's crossed the more stress cracks. Aluminum gets brittle with time and when a trailer starts to stress crack its' time is up. You can weld to your hearts content but it won't change the temper of the rest of the aluminum.

I have noticed that the newer trailers seem to hold up 100 times better than the first ones. Not sure why. My .02 cents is don't by one with stress cracks.
Ken

[tanker]

I must agree with Buffalo Guy, about rough use. It also depends on the alloy of the aluminum, several hardness available. A company new in building something they never did before is a huge learning curve. Thicker is also not better. I would look for a trailer that has proven itself. Someone that has been manufacturing these for several years, with an engineeering staff that knows stress, and how to cope with it. Ask around, do some searching on the net, see who's been out there a while. I don't ride horses, so I don't know anything about stock trailers. [img]smile.gif[/img]

[CleviteKid]

So-called stress cracks are really fatigue cracks, due to repeated cycles of high stress followed by low stress. Steel and titanium have what is called an endurance limit; if the stress is below the endurance limit, you can cycle a steel or titanium component an unlimited number of times without fatigue cracks starting or growing. That is why steel crankshafts, connecting rods, valve springs, transmission gears, axles and suspension springs are usually made of steel (or titanium in your Porsche race car).

Aluminum does not have an endurance limit - if you put enough stress cycles into it, it will crack, even at a low stress. While you are worrying about your horse trailers, worry more about the airplanes over your head. The airplanes all have aluminum wing spars, and the spars all have cracks. It is just that Boeing and the airlines (except for maybe Alaska and America West and others that Inspector knows about) know where the cracks are, how fast they are growing, and how many more flight cycles before the wings are replaced.

Properly designed and tested aluminum framed trailers can last a long time, but when they do eventually crack (might take 40 years) their time is up. For example, aluminum has been used successfully in boat trailers for many years. But I would agree, don't buy a pre-cracked trailer ! ! !

Most of the big-rig box trailers you see behind the Freightliners and the Navistars and the Peterbilts and the K-whoppers are built with steel frames and aluminum bodies, but as Tanker says they have carefully applied insulating plastic layers and zinc chromate primers to prevent the galvanic corrosion of the dissimilar metals. Is the average horse trailer built with the same technology and quality control?

Hope this helps you in answering your dilemma,

Dr. Lee

[Rockin]

The 40 year life sounds a lot more reasonable than the 2 years indicated by the salesman. I'm curious now what bi-metal protections they have in place on the steel framed aluminum body.

[Paintdude]

On Utilimatsters they insulate the metal frame from the aliminum body with some type of plastic protective sheeting.

[IndigoDually]

I currently have 3 Aluminium trailers, '95- 16' 2 compartment stock, '97 28' 5 horse head to head with dressing room and a '99 4 slant with dressing room. They are all Eby's. They have 2 plants, 1 in PA. and 1 in OH. They build all of their trailers from the ground up, they just buy components (axles, etc). My trailers are all aluminium, the only steel is the gooseneck and the axles. The '95 has well over 100k on it and I get asked if the trailer is new.

I bought my 1st one (the '95) used and proceeded to replace my others with their brand. I also have a truck body done by them. I haven't seen any evidence of stress cracks or electrolysis on any of mine.

Many times trailers sit 99% of the time, especially if the owner only hauls their own horses around. A trailer that is used for commercial transport will show the use and abuse and would be more of a candidate for stress cracks and broken welds. I run hard and fast and down some harsh roads and my trailers are doing fine. I am on the road at least 3 time a week and in the summer many weekends have 2 trailers out.

John