Ahoy, welders...

[jigsnreels]

I want to lengthen my drawbar by about 600mm. Interested in your thoughts about the best way to do this. It's a 100x50 section.

ATM, I'm leaning towards butt joining some more of the same, then welding a length of 100mm plate along the top & bottom of the drawbar, well past both sides of the join.

Any better ideas?

[barra71]

Hi Jig, when doing the butt joining make sure the join is on a 45 degree angle dont join it as a 90 degree angle.

as this is how i would do it mate. i am no boiler maker nor welder, but have have done lots of welding.. there may be a welder on the forums here that could tell you of a better way to do it..
and with the 10mm plate are you going to bolt it or weld it mate, as i would weld it in place. are you useing a stick or mig... also it would be stronger if you were to put the plate to the sides and not the top or bottom.. there would be more flex if it was on the top and bottom...

Chris

[Rip it up]

I'm with Barra. A 45deg cut on the drawbar with a long point at the top. The plate each side with 75mm x 6mm. Fully welded. You are in turn trying to bend 75mm of steel on its edge. Not an easy task.

The only way to approach it is to get an internal sleeve that is a neat fit inside the SHS. This would over lap the join 300mm each side. Drill main tube only. Plug weld in 4 points per side. Then strap the outside. But would be needed on a 3T boat not a single axle trailer. By the size of the drawbar your boat is only small.

Good luck.

[finga]

I'm with Barra. A 45deg cut on the drawbar with a long point at the top. The plate each side with 75mm x 6mm. Fully welded. You are in turn trying to bend 75mm of steel on its edge. Not an easy task.
I would not fully weld the plates.
I'd measure about 15mm from the pointy bit of each corner and draw a line across the steel at these 2 points to make a little right angled triangle and cut this triangle off and only weld the original 4 sides. I would not weld where the little triangles have been cut off.
This would have to be a biggest trailer with a 100X50 drawbar. If your not very, very proficient at welding and have a decent welder (150A stick welder from Bunnings simply will not cut the mustard) I would not do it and take it to someone to do as there would probably be a lot of stresses in a drawbar of those dimensions.

Where's Owen when you need him?

The old tilt trailers were easy to do. Buy some steel, unbolt the old and in with the new....jobs done.

And then when the jobs done don't forget to get the trailer remeasured for rego.

[Owen]

I would not fully weld the plates.

Where's Owen when you need him?


Owen doesn't own a welder.
And he won't give advice on a potentially fatal job with only half the information and no indication that the guy doing the job is qualified.

There is a big difference between being a welder and being able to make sparks!!!!

That said ... As far as joint prep, an angled cut has merit.
The joints should be prepped and a full penetration weld carried out.
This should be tested with dye penetrant before continuing.
The plates should be on the sides of the box tapered to a triangle with a rounded end.
Without knowing what material sizes etc makes it hard to be sure, but the plates should be welded top and bottom only and perhaps down the taper. No weld around the radius of the plate.
Welding down the face gives a heat affected zone that may crack during flexing.

If you didn't understand all the above then you're not qualified.

[jigsnreels]

The guy who wrote the post isn't a qualified welder but has made a few sparks over the years. The trailer is a Belco tandem with a Haines 580 on it. The bowsprit leaves only about 50cm clearnace to the car's rear window. The boat can't go back any further on the trailer.

I want a bit more room to get between the car and boat, but I'm not interested in killing myself or anyone else to achieve it. I'm happy to pay a pro for this one. The method outlined above came from a trailer maker - he was more concerned about sideways flexing than vertical flexing, hence the bar along the top & bottom. Owen, your idea seems the opposite of this. If I understand you, you're aiming to minimize lateral flexing,

Some nice thread work in yr pics there.

[Owen]

The majority of the load is it the vertical plane, so the loads are mostly on the sides of the box. That's why you don't want to weld right down the sides.

The best method assuming its an A frame with a central bar is to cut the whole centre bar out.
By adding a piece you have a weak spot in the most heavily stressed area of the trailer. The joint will also be in front of the safety chain so if it fails you'll be overtaken by your trailer.
Lots of structural things have joins. It's not that it's a massive undertaking, it's just not something to be taken too lightly.
Don't use a stick welder and spend the money on some dye penetrant to make sure there's no cracks when you're done.

The trouble with any mods is how are you going to stop it rusting from the inside?

[Gon Fishun]

If you are going to this much trouble, why not cut the draw bar out and fit a new longer bar, mig welded back in. Maybe have the steel gal dipped prior to fitting.

[tunaticer]

Tilt trailer or not?
If it is a tilt, get a whole new longer drawbar made.
What weight boat sits on this trailer, just because it sits on it does not necessarily mean that 100x50x??? RHS is the optimum size. Seems there is a lot of trailers under boats that barely carry the weights either by design and by material sizes or both.

[warti]

With the dye pen you should grind the top of the weld down a bit for best results.

[Dicktracey]

Has he thought about fitting a folding kit to save the hassle ?
Dick
http://www.trojanparts.com.au/index.asp?pageID=2145889249

[finga]

The method outlined above came from a trailer maker - he was more concerned about sideways flexing than vertical flexing, hence the bar along the top & bottom.
If that be the case then the 100mm side of the RHS would on the horizontal plane and not in the vertical plane.
Don't forget the longer the drawbar the greater the drawbar flex.

The drawbar folding kit Dick mentioned does go big enough. That would be a solution if it did.

[sid_fishes]

a pic or 3 would be a good starting point before anyone really makes a comment.
if the removal of the draw bar is possible,i would look at a bigger wall thickness to start with and possibly a bigger size ie 75x100. duragal is a good start
my 2 cents

[cormorant]

Creates some other issues that a towbar place will discuss with you and depends just how much clearance you realy need ( not what you would like) but what about getting a extended towbar tongue made up to give you a extra 150mm ?

Next one is using double pivot rollers at the rear of the trailer so it sits back another 6 inches, moving axle etc.

make all the front rollers higher so teh bow rides higher , yep a little more beef when winching on , bugger all extra effort but easier getting off and may give you extra clearance.

Yep you guessed it I don't like seeing production trailers get cut as if there is ever a accident and someone smart with a white wig or a propeller hat decides it was all made worse by the modification and the trailer wasn't reengineered and plate stamped over the pits then ......... It is not now the issue happens but 7 years on when the ungalvanised bit is rusted through and lets go. Check with someone who know the correct engineering ad paperwork when you modify a production trailer as now I believe you are supposed to reticket it and change the rego details offciially in NSW. QLD may be different. The person that does teh change is liable for the life of the product. .

Consider trading it in on the correct trailer for your purpose is the other option or if a stainless bolt on bow use a shorter design .