Trailer Project

[Bilbo]

Trust me Brett, Kegsy knows his sh!t and I for one would place my life in that mans hands

I'm sure without his help and advise on our outback trip my trailer would still be sitting on the Bogey Hole track in the NT

The best way he's explained it to me is that any cross weld will fatigue the structural integrity and there for create weak points. I can only guess but the combined weight of all the bikes would have to be in the vicinity of 500kgs + wouldn't they

Fish plate the draw bar now I'd suggest

I'll take all the advice I can get as I want this project to work and be safe.

I need Kegsy just to clarify re the cross members. I have three running between the chassis rails (they are not in the earlier photos I have posted). I need to be sure that the bike tracks on top of the chassis that don't provide any structural strength to the trailer haven't weakened it. If the consensus is that it is weakened then is there a fix or should I abort the project.

The combined wet weight of the bikes is 396kg, with the heaviest nearest the axle.

Thanks for everyone's help.

Cheers Brett

[4wd26]

you have weakened the chassis by the welds across the chassis attaching the bike racks

by how much?? that is hard to assess.

fishplating the entire side of the box might be harder than adding a 50x50 rail under the chassis.

[snowman]

Welding along the width on the main chassis rail significantly reduces its strength. IE: where those cross members have been welded. Ideally you wouldn't weld across the width on the main chassis rail, but weld the cross members from their underside along the radius / edge of the rail.



The concern isn't that you haven't got enough weld, rather that the current weld is in a location that reduces the strength of the main structure. Adding more welds as you describe won't do any harm, but its not going to offset the potential for a stress fracture where the other welds are.

Hope that makes sense.

I am not a structural engineer but do work in the building industry so to use some different terminology if you imagine your RHS drawbar was an 'I' beam the top and bottom (shorter lengths) are the Flanges whilst the longer (depth) is your Web.

700px-Ibeam.svg.png

With structural columns for example the strength is provided by the flanges. That is why you will rarely, if ever, see them modified. That said the 'Web' can be penetrated. The 'Web's' primary role is not for strength per se' but to maintain the flanges location parallel to each other.

So what Kegsy is saying is that you should not drill, weld or deform the top and bottom faces of the rectangular hollow section at all if you want to maximise your strength.

[4wd26]

not quite the case in the box sections
the trailer could have been made and had the bike racks attached

BUT

the welds needed to go along the box section, in this case under the bike rack, so a difficult weld

he would have got the same length of weld (or better) without the potential to weaken the rail.

the rail or chassis in this case has all the welds parallel to the load/ stress lines induced by towing

another way around this would have been to have a plate on the top with the parallel welds for the bike rack, and this attached to the chassis by long welds along the chassis

some sort of stringer under the chassis would be advisable for the length you are going, this would be lighter than a full box section replacement/ addition
http://www.gnschassis.com.au/products_a-frames-straps.html

[Bilbo]

So I guess from the info above I'd be better off starting the chassis rails again or using the braked axle on my other trailer and give this project the flick.

Hmmm decisions decisions.

Any one want to buy an ml tub and canopy?

[4wd26]

Not necessary to dump everything you have done
We have given info on what might be weak points and methods to rectify, from there it is up to you to decide if the fix is easier than starting again

I really like the concept and how it looks and importantly for you does everything you wanted

[Bilbo]

Not necessary to dump everything you have done
We have given info on what might be weak points and methods to rectify, from there it is up to you to decide if the fix is easier than starting again

I really like the concept and how it looks and importantly for you does everything you wanted

Thanks 4wd26,
I'm really not sure which way to go.

I've had many boat trailer that has had the strap ( as per your link) either under or on top of the rail. I can see how that would help.

Cheers. Brett

[BillMcQuade]

Let's be a bit realistic here, I have seen many of those old crappy, angle iron box trailers getting around with heaps of rust and the worlds worst welding. They are usually get well overloaded, and still keep on plodding. This trailer looks a lot better than those, and just needs a little work to make it last forever.

I do a lot of fabrication, and I agree with Kegsy's suggestions on weld placement. So never fear, it certainly isn't "throw away the trailer" time. A few bits of doubling will sort out any issues that the trailer may have, or you can weld a strongback along the bottom profile of the drawbar. You can also run a centre spine between the apex of the drawbar, and terminate it on a new crossmember down towards the tub.

[Kegsy]

Everyone has pretty much cleared it up I think...

It definitely isn't a loss. Just fish plate it up, or run another section underneath and double it up.

The trade off is weight however.

Given the length of that drawbar and the load I would be beefing it up anyway. Better to over engineer and make it home, then to go a little light on and have to leave her behind out in the middle of nowhere.

[al coholic]

Better to over engineer and make it home, then to go a little light on and end up ruining everyone's holiday

Fixed

[Kegsy]

Thanks mate hahaha

[Bilbo]

Thanks Kegsy,

I've contacted the guys who are going to comply the trailer for SA rego. They are going to have a look and advise exactly what I need to do. I guess if they are signing off on it and I do what they suggest we won't have any issues come rego time.

Thanks everyone for your advise. I shall continue to persevere.

Cheers Brett.

[Bilbo]

I've decided to stop this project and develop the other trailer that I have built.

Hence the tub and canopy are now for sale.

Cheers Brett.

http://www.gumtree.com.au/s-ad/1061903542

[c-dale]

Disappointing to hear mate, was looking like an awesome project.

[har05l]

I agree with c-dale, was coming along nicely and very unique.

Perhaps if you don't have luck selling the tub/canopy you may pursue it

Good luck anyway

[Bilbo]

Thanks guys. Agree har05I I'm in no rush. Will see what happens.

We used the other trailer on Fri night. Here's some pics!




LED lights and all.

[har05l]

Looks practical but I like the other one better

How do you go with condensation under the mattress ?

[gazman152]

Thanks guys. Agree har05I I'm in no rush. Will see what happens.

We used the other trailer on Fri night. Here's some pics!




LED lights and all.

Very cool. Would like to do something similar except quad bike underneath boat rack on top. Bit of a boys hunting / fishing machine.