4x8 extension

[kitecop]

Can sumone steere me toward a thread on extending the tongue of a 4x8 HF trailer? I know its on here but cant find it.

[pchast]

Here is mine... viewtopic.php?f=50&t=54690&start=15

I included a grade 8 bolt in the end and into the hitch adapter in addition to
my welding. Belt and suspenders, both...

[kitecop]

Hmmmmm, i already have about 8 ft of 2x2 so i was going to weld to the face of the front of the trailers box frame and send it through the exhisting square channel that the hitch normally attaches to. I need a good 3ft extension.

[KCStudly]

You really want the extension to reach back under the first 2 xmbrs (if not further). Attaching to the face of the front xmbr is weak.

[bobhenry]

Harvey (nobody) where are you ?

I copied my efforts somewhat from his post. It had lots of good pics.

found one ......

http://tnttt.com/viewtopic.php?f=35&t=60591&p=1088793#p1088793

Here is the one I was looking for.......

http://tnttt.com/viewtopic.php?f=35&t=60358&p=1085971#p1085971

Ya gotta love his test load in this post.....

http://tnttt.com/viewtopic.php?f=35&t=14551&p=190079#p190079

[bobhenry]

Here is a rear hitch added to a HF frame. I owe someone an apology as I have forgotten who's album picture I stole



Make a great way to add a bike carrier or a cargo platform if needed.

[Nobody]

I'm here Bob, just been busy all day workin' on my new (to us) Casita. Had to fabricate a sliding battery tray 'cause the door to the battery compartment is rdius'd, & manally lifting a battery that weighs a third as much as me, especially at arms length to put in'n out of the compartment ain't any fun. Also had to move the fridge out into the aisle to replace the Piezo Igniter & then replace all the rivets I drilled out .

When I built my TD in 2006 I used the 1800# (then) HF trailer. I love the trailer but just couldn't abide that 'clunky' coupler mount, & I thought it'd be nice to add a little length to the tongue for easier backing/parking etc. I had on hand a piece of 2" square steel tubing, approx 1/8" thick walls. It was just long enough to reach the 2nd cross member & protrude approx 17" in front of the existing factory coupler mount. I turned the factory coupler mount upside down, did a little judicious grinding, drilled a couple of holes & bolted the old coupler mount upside down on the 'A' frame tongue. I cut a couple of pieces of 1 1/5" steel angle & after placing the tongue extension through the re-sited coupler mount, & squaring the extension to the trailer chassis, I bolted the pieces of angle to the cross members either side of the extension, & the extension to the steel angle pieces. I also bolted the extension (top to bottom) to th cross members & the old coupler mount. Added a new 2" coupler to fit the extension & built my TD. It's been almost 9yrs & 25K+ miles & it's still solid, & works great tho some of the factory paint has 'flaked' off the old coupler...

[kitecop]

This is probably the route i will go. Thanx.

[angib]

Yes, picking up at least the first two cross-members is essential - otherwise you are just modifying the HF trailer to make it weaker.

[daveesl77]

Nobody's method is exactly how I did my HF tongue modification. I may have actually copied mine from him. Maybe not exactly exact, as I also bolted through both cross members and also welded. Yeah, I'm one of those belt/suspenders people

dave

[kitecop]

Adding the extention that way def requires a bolt since the added piece does not press against the frame anywhere. All the towing and stopping forces create shearing pressure that relies only on the welds to absorb the energy. I dont consider the bolt excess... Its needed as it reduces the shearing stress on the welds dramatically.

[KCStudly]

Adding the extention that way def requires a bolt since the added piece does not press against the frame anywhere. All the towing and stopping forces create shearing pressure that relies only on the welds to absorb the energy. I dont consider the bolt excess... Its needed as it reduces the shearing stress on the welds dramatically.

Um, sorry but this statement is just wrong.

The shearing loads are the shearing loads and the cross sectional area of the material that those loads are applied to is the cross sectional area that those loads will be applied to. The cross sectional area of a bolt is actually very small, and it is easy to apply a lot more cross sectional area with the application of welds. The bolts can do the job, and can certainly be of help maintaining alignment during the welding process (or use clamps) but once the welding is added the bolts are essentially just along for the ride.

The effective cross sectional area of a 3/8-16UNC bolt in single shear thru the threaded portion (such as in a bolt tab situation) is only .067 sq in (http://www.engineersedge.com/fastener_thread_stress_area.htm). Two 3/16 inch nominal welds down either side of a tube crossing a 1-1/2 inch wide xmbr amounts to .105 sq in {(3/16^2 / 2) x 1-1/2 x 2 = .105), or about 160% stronger than a single bolt. Since the weld must fail first for relative motion to occur and the bolt to see any shearing load, the bolt isn't adding anything at that point.

For the same bolt in single shear (such as when bolting thru two tubes with anti-crush sleeves) the area of the bolt being loaded would actually be a little larger than the described weld, at .110 sq in, but the relative motion argument still wins. If we are conservative and assume that we are designing with a yield strength of 24kips for mild steel then the shear strength for this single theoretical joint is in the neighborhood of 2500 lbs. Do that 3 or 4 times to fasten your tongue and you should have no worries about shear, even with road jarring acceleration/deceleration. Add welding clips made from short lengths of angle steel or gusset tabs and you can account for additional torsion loading (line of force vs. attachment point offset, twist such as with coupler binding, etc.)

[kitecop]

Adding the extention that way def requires a bolt since the added piece does not press against the frame anywhere. All the towing and stopping forces create shearing pressure that relies only on the welds to absorb the energy. I dont consider the bolt excess... Its needed as it reduces the shearing stress on the welds dramatically.

Um, sorry but this statement is just wrong.

The shearing loads are the shearing loads and the cross sectional area of the material that those loads are applied to is the cross sectional area that those loads will be applied to. The cross sectional area of a bolt is actually very small, and it is easy to apply a lot more cross sectional area with the application of welds. The bolts can do the job, and can certainly be of help maintaining alignment during the welding process (or use clamps) but once the welding is added the bolts are essentially just along for the ride.

The effective cross sectional area of a 3/8-16UNC bolt in single shear thru the threaded portion (such as in a bolt tab situation) is only .067 sq in (http://www.engineersedge.com/fastener_thread_stress_area.htm). Two 3/16 inch nominal welds down either side of a tube crossing a 1-1/2 inch wide xmbr amounts to .105 sq in {(3/16^2 / 2) x 1-1/2 x 2 = .105), or about 160% stronger than a single bolt. Since the weld must fail first for relative motion to occur and the bolt to see any shearing load, the bolt isn't adding anything at that point.

For the same bolt in single shear (such as when bolting thru two tubes with anti-crush sleeves) the area of the bolt being loaded would actually be a little larger than the described weld, at .110 sq in, but the relative motion argument still wins. If we are conservative and assume that we are designing with a yield strength of 24kips for mild steel then the shear strength for this single theoretical joint is in the neighborhood of 2500 lbs. Do that 3 or 4 times to fasten your tongue and you should have no worries about shear, even with road jarring acceleration/deceleration. Add welding clips made from short lengths of angle steel or gusset tabs and you can account for additional torsion loading (line of force vs. attachment point offset, twist such as with coupler binding, etc.)

You are assuming that the bolt setup has slop in it or there is zero flex to account for. The cross members on the HF trailer surely flex some under breaking and acceleration with this modification. The cross members being welded too were designed for vertical strength not lateral. If the extension has a thru bolt to hit durring the flex then it recuces the stress on the welds. No matter how u look at it, adding an extension that way does not use the structural integrity of the 2" tubing... It relies soley on the welds. Also, I doubt the trailer itself is of a very high quality steel so i personally would not rely on just a few inches of fillet weld to hold my extention to my trailer.

[KCStudly]

The presumption is that the welds are applied by a qualified welder.

If you don't trust your ability to weld, then bolting is the right decision for you. But it is not correct to state that the bolts are de facto required in order to make a suitable joint. It is the design of the connection that determines its ability to perform the desired function as much as it is the fastening method.

There are good bolted joints and good weld joints; and there are bad ones, too.

Peace.

[Nobody]

I have NO engineering knowledge or experience, just quite a few years of practical experience building things that undergo varying degrees of stress in different situations for my personal use. I have limited experience welding & have built a couple of hitch receivers that we used to tow tandem axle equipment trailers hauling medium size farm tractors & small dozers (generally non-highway use). None of my welds ever failed but I knew what kind of new steel I was using, the capabilities of my welding machine, the rods I used, & I was careful to 'over-spec' my material/job for planned/intended use.

I had no such information on the HF trailer chassis, the 2" square tubing, or the 'angle-iron' I used. I simply found the angle that had been used in an old farm gate (in good, rust free condition), bought the tubing from a local supplier (told him what I wanted it for & he selected an appropriate piece). After locating & 'squaring' the angle & tubing to the trailer chassis I clamped everything securely in place, drilled holes thru one 'leaf' of the angle vertically thru the lower side of the trailer chassis 'C' channel cross member & bolted it up using 1/2" Grade 5 automotive strength bolts, nuts, & washers. I then drilled horizontally thru the other 'leaf' of the angle, thru both sides of the square tubing & bolted it up, again using two 1/2" Grade 5 bolts. The only vertical bolt thru the square tubing is at the original ball mount & that is for stability since the tubing didn't completely 'fill' the 'slot' vertically. I used Grade 5 bolts horizontally to fasten the coupler to the square tubing. I 'passed' my trailer wiring thru the square tubing tongue extension inside a corrugated vinyl/plastic 'loom' & figured it'd be hard enough to thread it under the horizontal bolts without introducing more difficulty with 'unneeded' vertical bolts in the way... After it was done I had a friend (who built commercial equipment trailers for a living) inspect my work & he pronounced it good, & since then I've towed the TD 25K+ miles & never gave it a second thought. Pretty sure I made a misstatement in my above post when I said I'd bolted the extension vertically thru the 1st & 2nd cross members. I did not do that, just the horizontal bolts thru the angle iron used. Also, that post makes it appear that I had the 2x2" tubing 'on hand' & used it for the extension when in fact I bought it for just that purpose