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Thread: Is an Aluminum drawbar strong enough for a towbar rack

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    Is an Aluminum drawbar strong enough for a towbar rack

    I am putting together an aluminum enclosure for a tow bar carrier (think of it like a small bike rack off the tow bar, but enclosing it). Some notes:
    • The enclosure frame is going to be with Aluminum.
    • Weight to be carried is only ~45kg
    • Towbar is reese hayman - so 50mm x 50mm square
    • Main reason is I can then weld directly onto this as the rest is in Aluminium, plus keeps another item lighter weight in the design too


    Question 1 - Would it be OK to use Aluminum for the main bar going into the tow bar? Say 50x50x3.0 dimensions with 6060 T5 temper?

    Question 2 - If not, what would be the approach to attach/fix an Aluminum frame onto a drawbar (with some crossbeams) which is steel?

    thanks

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    Re: Is an Aluminum drawbar strong enough for a towbar rack

    45 KG, that's about 100 LBS. Aluminum isn't as strong by dimension as steel. With steel, I tow 10000 LBS with a Tongue weight of 1500 LBS. How will you attach the carrier to this 2" piece of solid bar stock? Some welding equipment might not be up to the task.
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    Re: Is an Aluminum drawbar strong enough for a towbar rack

    Quote Originally Posted by Willie B View Post
    How will you attach the carrier to this 2" piece of solid bar stock? Some welding equipment might not be up to the task.
    not really sure what you mean here - re the Aluminium option it was hollow square 50x50x3.0 that I was considering re whether it's strong enough to carry 45kg..

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    Re: Is an Aluminum drawbar strong enough for a towbar rack

    Solid shouldn't be a problem, though the vibration will wear into the aluminum. Hollow I would avoid. BTW, this type of application is not where aluminum shines. It will fatigue a crack at the welds much quicker than steel.

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    Re: Is an Aluminum drawbar strong enough for a towbar rack

    I would think steel drawbar and frame to mount aluminum box on would be a much better arrangement.

    Mike

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    Re: Is an Aluminum drawbar strong enough for a towbar rack

    Steel, 10,000lbs? I haul 15,000lbs with aluminum. FYI there are LOTS of 2" aluminum drawbars and the do shine quite literally, many are Class V rated for higher towing weights than any 1/2 pickup can haul. Those are forged, not the 2"x2"x.125" you are referencing (Sorry mate, no sillymeters for me )

    Now your square tube may be the minimum for a substantial weight of 100lbs. Fatigue cracking is BS if it's welded properly, and you can NDT the 4 place bike carrier I made about 20 years ago that is still fine and dandy. I think it is 1/4 wall drawbar. There are as well probably hundreds of thousands of other bike racks and hitch carriers that are rated for higher weights which you can buy that some poor kid in China made for $99 at Walmart. There are even aluminum carriers just like you describe making which are rated for 300lbs, and I have another channel style which is rated for 500 lbs that I strap my dual sport motorcycle to.

    So yeah you don't need a 100 lbs of steel to hold your 100lb carrier.
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    Re: Is an Aluminum drawbar strong enough for a towbar rack

    Quote Originally Posted by mixedup View Post
    not really sure what you mean here - re the Aluminium option it was hollow square 50x50x3.0 that I was considering re whether it's strong enough to carry 45kg..
    The hollow stock in the receiver is a question for engineers. I acquired second hand a basic carrier from Tractor Supply I think. Although it is of steel the hollow male portion isn't sturdy enough for a small aluminum tool box. If any imbalance left to right, it twists. I brought it home with a 30 LB aluminum tool box, empty except for a 50 LB vice. In 20 miles the vice had slid to one side, and that side was nearly touching the ground.

    For your carrier, I suggest a solid 2" bar in the receiver. At the two front corners place metal passing under the hitch frame to prevent twist. A solid bar of 2" aluminum is a massive heat sink. Perhaps a large MIG with spool gun will work, Only the very largest TIG machines can get a sound weld with that large a weldment. Consider a steel insert, and bolt, or clamp aluminum to it. This also moves the dissimilar metal / stress corrosion away from such a critical point.
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    Re: Is an Aluminum drawbar strong enough for a towbar rack

    Like this one? Aluminum fatigues, add a huge drop as a lever and stuff happens.

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    Re: Is an Aluminum drawbar strong enough for a towbar rack

    You could add another couple hundred pounds on it and still have peace of mind. Just have good fit up and correct legg heights

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    Re: Is an Aluminum drawbar strong enough for a towbar rack

    Mixedup, you contemplating 50mm x 50mm x 3.0 mm wall tube? Too thin - it might hold up a couple aluminum lawn chairs. And will it have very sharp corners? Might not fit in the receiver.
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    Re: Is an Aluminum drawbar strong enough for a towbar rack

    Quote Originally Posted by VPT View Post
    Like this one? Aluminum fatigues, add a huge drop as a lever and stuff happens.

    No, that's not forged like I said and all metal fatigues. That's a cute milled block of aluminum welded to another block with a design full of stress. That was an accident waiting to happen, no matter what it was made from, aluminum, steel or kryptonite, with no chains, a long drop, and a little 1/4" fillet weld. Where's the rest of the story, overloaded trailer, probably overloaded tongue weight, I bet there was lot of stupid going on. It's not just material material, how it's made and used. I can post plenty of steel hitches too that are snapped because they are dangerous designs, poorly executed and abused by morons.

    Good thing there aren't $350 million dollar 747's carrying hundreds of people at nearly the speed of sound flying on aluminum wings. Those bend, oscillating hundreds of cycles an hour for thousands of hours. They must be steel I beams.
    Last edited by xryan; 04-05-2016 at 04:06 AM.
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    Re: Is an Aluminum drawbar strong enough for a towbar rack

    And planes are riveted together to allow more movement without stressing the metal. Ever ride in a riveted boat and then a welded boat?

    Also check the break on that aluminum drop, the weld didn't break.

    Aluminum trailers crack and fall apart. A steel trailer (as long as it doesn't rust) can basically last forever.

    Aluminum is great, I love to use it, but it has its places and uses.
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    Re: Is an Aluminum drawbar strong enough for a towbar rack

    Quote Originally Posted by VPT View Post
    And planes are riveted together to allow more movement without stressing the metal. Ever ride in a riveted boat and then a welded boat?

    Also check the break on that aluminum drop, the weld didn't break.

    Aluminum trailers crack and fall apart. A steel trailer (as long as it doesn't rust) can basically last forever.

    Aluminum is great, I love to use it, but it has its places and uses.
    Those are about the most ignorant statements I've ever read.

    Apparently aluminum is the only metal that fatigues in your bizzaro world. Have you ever seen an aluminum object that has been welded fail, where it fails, why it does so, where the base metal has been weakened without additional heat treatment?

    You both also ignore that POS adaptomatic-turnover designed for every truck/trailer combination which is disaster, safe for none. Where's the rest of that photo's story? The chains? The boat on the trailer? The tires? The, most likely, idiot driver?

    If you'e worked in avaition you know that every system of the airframe has mandatory inspection and overhaul hour limits, regardless of the material.

    Welded vs rivited aluminum boats? I'll take welded every time. Yes "I've ridden in them" both as a passenger in a vessel and Master of it (merchant mariner licence, ie: Captain) I've welded them, repaied rivited ones, as well as steel. I guess you've never seen a ship split in half and sink like a rock taking the crew with it that was made from steel. Would you like me to show you pictures of steel trailers that are 2 years old that have failed, with no rust?

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    Re: Is an Aluminum drawbar strong enough for a towbar rack

    Ryan, you could lighten up a bit and still make your point. Sounds to me like you and VPT were making some of the same points in different ways.
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    Re: Is an Aluminum drawbar strong enough for a towbar rack

    Yep, tone it down boys. No need to turn this thread into a pissin' match.
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    Re: Is an Aluminum drawbar strong enough for a towbar rack

    Duane, you got a problem? Bring it on, LOL!

    I hope the OP wasn't talking about using 3mm wall tube. That is my concern. ~ 100 pounds sticking out the back and no mention of the length, load distance or road conditions ...

    I remember flying in Boeing 727's where the wings would flap around all over the place. Felt much better in a 737, especially when I was flying "strapped-to-the-wing class".
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    Re: Is an Aluminum drawbar strong enough for a towbar rack

    As a truck driver almost any of us will tell you aluminum trailers are preferred. They're lighter. Last just as long. They don't rust, aluminum doesn't bend well so usually they don't dog Leg over time like steel ones do. If they break big deal. That's what insurance is for. Usually the welds on the rub rails where you secure your chains and straps is what breaks if they ever do break. Easy fixes. Weld it. Don't have to worry about bending and hours of hammering and straightening like you do with steel

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    Last edited by jakehawk9; 04-05-2016 at 10:11 PM.

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    Re: Is an Aluminum drawbar strong enough for a towbar rack

    Quote Originally Posted by Oldendum View Post
    Duane, you got a problem? Bring it on, LOL!
    My post wasn't directed at you. It just came up right after yours.
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    Re: Is an Aluminum drawbar strong enough for a towbar rack

    Quote Originally Posted by xryan View Post
    Those are about the most ignorant statements I've ever read.

    Apparently aluminum is the only metal that fatigues in your bizzaro world. Have you ever seen an aluminum object that has been welded fail, where it fails, why it does so, where the base metal has been weakened without additional heat treatment?

    You both also ignore that POS adaptomatic-turnover designed for every truck/trailer combination which is disaster, safe for none. Where's the rest of that photo's story? The chains? The boat on the trailer? The tires? The, most likely, idiot driver?

    If you'e worked in avaition you know that every system of the airframe has mandatory inspection and overhaul hour limits, regardless of the material.

    Welded vs rivited aluminum boats? I'll take welded every time. Yes "I've ridden in them" both as a passenger in a vessel and Master of it (merchant mariner licence, ie: Captain) I've welded them, repaied rivited ones, as well as steel. I guess you've never seen a ship split in half and sink like a rock taking the crew with it that was made from steel. Would you like me to show you pictures of steel trailers that are 2 years old that have failed, with no rust?

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    Steel doesn't crack. Never seen it happen ever. Stainless maybe but not steel.
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    Re: Is an Aluminum drawbar strong enough for a towbar rack

    Quote Originally Posted by VPT View Post
    Steel doesn't crack. Never seen it happen ever. Stainless maybe but not steel.
    Huh? I can think of any number of heavy equipment threads that show cracked steel ( buckets, loader arms, suspension components..), as well as plenty of picts in the trailer fail thread of cracked steel.
    .



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    Re: Is an Aluminum drawbar strong enough for a towbar rack

    Quote Originally Posted by DSW View Post
    Huh? I can think of any number of heavy equipment threads that show cracked steel ( buckets, loader arms, suspension components..), as well as plenty of picts in the trailer fail thread of cracked steel.
    Bologna! Show me one pic of steel that cracked from fatigue.
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    Re: Is an Aluminum drawbar strong enough for a towbar rack

    Quote Originally Posted by duaneb55 View Post
    My post wasn't directed at you. It just came up right after yours.
    Just teasing, Duane.
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    Re: Is an Aluminum drawbar strong enough for a towbar rack

    Quote Originally Posted by Oldendum View Post
    Ryan, you could lighten up a bit and still make your point. Sounds to me like you and VPT were making some of the same points in different ways.
    Fair enough, I could "tone it down". No I don't really think we are saying the same thing in different ways. The original query was basically asking about a luggage rack on an aluminum drawbar, I gave him a real world answer, yes no issue albeit not with an aluminum foil tube. However others would like him to believe he needs a steel behemoth sticking out the back just showing an aluminum one that failed. To answer VPT :

    No, they are not riveted for that reason.
    Yes I have ridden in welded and riveted, as well as built them and captained them. I'll take welded every time.
    The weld bead didn't break because that's not where the failure occurs in aluminum, it fails in the weaker HAZ outside the bead.
    Any trailer can and will crack due to metal fatigue. The aluminum actually give you a bit more warning with it's larger plastic yield deformation, the steel may develop an unseen crack since it has a smaller plastic deformation zone, then a catastrophic failure.

    As for the broken aluminum drop hitch (which was a horribly design), here's steel failures, which similarly don't prove anything other than things break. Who knows how the part was used before the failure, most likely it was abused and overloaded as we all see almost daily on the road and in the LONG trailer fail thread.Name:  steelhitch.jpg
Views: 275
Size:  40.9 KBName:  ballfailure.jpg
Views: 275
Size:  109.7 KB
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    Re: Is an Aluminum drawbar strong enough for a towbar rack

    Quote Originally Posted by VPT View Post
    Bologna! Show me one pic of steel that cracked from fatigue.
    Yes you must be right, that why the Federal Highway Administration produced the Manual of Repair and Retrofit of fatigue cracks in steel bridges. Figure #1 in that publication is described as "Typical fatigue crack across a repaired flange butt weld in a welded I-girder test specimen. The arrows show the direction crack growth and the fatigue striations show how the crack grew elliptically through the flange. Photo courtesy of US Coast Guard."

    2nd paragraph in Chapter 1 just above that picture says this.

    FATIGUE

    When cracks are discovered in bridge elements (members or connections) in service, fatigue is usually the cause. (5) Fatigue is the formation of a crack due to cyclic service loads. (6,7) Figure 1 shows the surface of a common fatigue crack. This crack originated at the toe of a repair butt weld in the flange of a welded built-up I -girder (hence the access hole cut into the web). The appearance of a fatigue crack is typically smooth and silky, as shown in Figure 1. Fatigue surfaces usually show distinct striations outlining the shape of the crack as it grew (as seen in Figure 1) and these point back to the origination point of the crack

    https://www.fhwa.dot.gov/bridge/stee...0/hif13020.pdf



    I'm too lazy tonight to find a steel paper clip and bend it back and forth until it breaks to prove steel fatigues and cracks due to repeated cyclical loading.
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    Re: Is an Aluminum drawbar strong enough for a towbar rack




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