Thread: Punch 12mm hole in 8-10mm steel

Originally Posted by gazza2009au

How about some advice on how to make it stronger rather than critisisim and bashing my idea into the ground?

What about all these home made trailers being built how many of those builders had a engineer cad there designs?

And that is just what I and a couple of people were commenting on - people without the necessary skills designing and/ or making trailers. If we had faith that you had a handle on what you were doing there would not be so much criticism on what you are attempting but you seem right out of your depth and without the self awareness to recognise that.

A really simple example - have you calculated what force the fully laden trailer (that is, with boat) will exert at the towing hitch? I ask because I was taking to someone about tow bar mounted bike racks recently, and they were telling me stories about tow bars breaking off because too much weight was on them and then the car hit a pothole. Looking at that trailer with the wheels right at the back and it's length, I think you could be in trouble.

Originally Posted by gazza2009au

Thanks J i have never head of calculating bending moments i looked it up on youtube i will calculate it when the sun comes up, do u possibly have a link to a chart or scale for the results so i can compare or do u know where i can look to find it?

Engineering students literally spend years learning how to calculate bending moments and what they mean/ how they should be applied (because those bending moments don't mean much unless they are put into other equations). As per this thread
https://metalworkforums.com/f307/t203572-risk-liability
I doubt if anyone who knows what they are doing will give you an answer

Michael

Michael read your post in the email notification, i can only see a bike falling off a rack if its a 40x40mm or the smaller square towbars mine is the 50x50mm im not saying mine wont break but i have carried a 145kg bike on a rack i have actually carried a few bikes on my rack

The rack its self probably weighs 30kg i have had a DRZ400, WR450F, Husqvarna TE450 and various other bikes on it

I think its rated to 270kg ball weight the ideal ball weight is 10% of the pulling load my xtrail is rated 2000kg so 200kg ball weight

The trailer may look odd with a long Y on it but the boat doesnt pull right up to the front.of the trailer it will sit 60% over the front axle 40% over the rear and that is the hull only the rear 40% has the engine too (the 60/40 is just the hull)

Im out here measuring it now

Boats hull is 5.7m

Center between axles leaves 2m over the rear axle

From center of axles leaves 3.7m of hull over the front axle

Than i have the engine hanging off the rear of that 2m so likely the boat on trailer will be

From center of both axles will be 2.7m of hull and engine off the back and 3.7m of hull over the front axle

It will sit like the tape measure in the pics i done all these measurements a year ago when i planned it all out just over time i have forgotten

Hi there,

Come into this thread late it appears,

What braking system will you be using?

Also, for everyone who has reservations regarding the safety and design of this trailer, don't forget it will need to be registered. This will mean having it inspected. I'm not qualified or experienced in these type of trailer designs but surely any dodgy design will be rejected when it comes time to register it?

After a recent trip across the Simpson Dessert, I look at trailer design completely different now. I witnessed a graveyard of destroyed and abandoned trailers all along the French line. Makes you realise that it's not that easy to look at a design and decide if it's a good design or not just by how it looks.

Gazza, if you are not sure if your trailer design and build is up to scratch, just tow it across the Simpson. If you still have it when you get to Mount Dare then it's a good design!

Simon

I am by no means an expert in the area but from some knowledge my understanding is that in Australia the requirement for trailers is covered by VSB1.
Registration is covered by an inspection however this does not go into detail of engineering or weld / connection strength, unless it is obviously poor workmanship it will get past.

The manufacturer or importer must affix a plate that identifies the party taking responsibility for the certification statement.
The responsibility for safety falls back to the manufacturer / importer and can be identified via the above vehicle plate.
https://www.infrastructure.gov.au/ve.../vsb_01_a.aspx


There are many instances of fatigue failures particularly with aluminium, I am only suggesting that for your own piece of mind get some professional advise from people that build theses types of trailers. There are a lot of home built trailers out there but most are steel, aluminium in structural use is a different animal.

You are correct regarding the building regulations are governed by VSB1.

I will be building a 6x4 offroad trailer at some stage. Rated to 1600Kg independent suspension with electric brakes. That type of design is way out of my league, especially after what I saw in the desert. I have bought specific plans for such a trailer build and the independent suspension is an "off the shelf" buy from a certified trailer parts manufacturer. It comes with the trailing arms with stub axles welded in, mounting brackets, springs, shockers and electric brakes. At $1600 it's not cheap but they have done all the engineering for me and certified it.

The only thing it requires from me are reasonable welds which I'm pretty confident with.

Simon

I've never understood why it is not a lot more stringent.

It's not difficult to make a good looking weld that lacks penetration and also to make a crap looking weld and then cover it with bog and paint and who is to know? Poor workmanship can be covered up easily for the unsuspecting eyes.

If something goes wrong and it causes a serious accident who is then to blame?

Obviously this rarely ever happens otherwise changes would have been made to the ruling.

Apart from the quality of the weld looking at it is also the penetration and most importantly where on the structural member the weld is.
With trailers the most common mistake is the thought to weld connections all the way round thinking more welds is better and stronger, the A frame in particular should not be welded across the connection where it meets the chassis as this creates a spot that is prone to fatigue cracking.
Another common shortfall even with bought trailers is the A frame being cut short, for maximum strength the A frame should continue all the way to the front suspension mounting points rather than relying on the chassis to provide that strength.

If something goes wrong and it causes a serious accident who is then to blame?

As per above the vehicle plate identifies the party taking responsibility of the certification statement. For a home built trailer this is the person who built it.

Here is a nicely understandable link to the most basic explanations of forces at work in beams - with the right kind of formulas to START learning.
Calculating Forces in Beams - DT Online
To get a handle on the formulas presented, EVERY LINK in the text needs to be followed and UNDERSTOOD to apply the formulas.
Simply entering values in the formulas ISN'T enough! It is NOT just a table you can look up and apply.
Say for example you follow the link to Young's Modulus. There are heaps of links in that page too - each of which leads to an explanation that needs to be read and understood to make sense of the subject matter. E.g. the link to work hardening there leads to explanations of crystalline structures of metals that need to be understood to make sense of work hardening.
The whole subject of beam assessment and calculations becomes an ever increasing web of information and knowledge.
But consider even this as the entry level only.
To get to the next level of understanding (like metallurgy, metal fatigue, shock loads etc) does actually require very intense study at university degree level.
You DON'T need to get a university degree to learn this stuff and be competent, but you DO NEED a university degree to become certified to to apply that knowledge if you could be liable for the consequences of failures.....

Once you have an understanding of these physical and mechanical issues of design, then there are other topics required to be an "engineer": corrosion, galvanic action, plating, anodising, painting etc. are all subjects of CHEMISTRY.
These too need to be known and understood and applied to design - say an aluminium boat trailer that is likely to be immersed in sea water...

In one of the links above to a commercial aluminium boat trailer, they make a particular point of advertising the use of stainless steel fasteners. Looks very nice too!
Then read this: https://www.albanycountyfasteners.co...-and-aluminum/ and wonder....
However, they also advertise that the chassis members are anodised. This may well be because they actually have an engineer on staff who did some analysis or tests with stainless fasteners in the context of anodising as an electrical insulator (which it is). If that was the case (and the anodising is indeed done AFTER all the bolt holes were drilled or punched) then I take my hat off to the engineer for that design.

I hope this help a little further....

Originally Posted by gazza2009au

How about some advice on how to make it stronger rather than critisisim and bashing my idea into the ground?

This isn't a "bash Gazza" thread, this is a "try to make sure Gazza doesn't end up in an extremely deep and expensive pile of s***" thread.

The thread started off with trying to keep you safe from yourself, now it's making sure that everyone else on the road around you is safe as well and that's a whole lot more serious.

You've got enough knowledge to get yourself in trouble, but not quite enough to drag yourself back out again, and if something goes wrong the buck will stop with you and you might find yourself up the creek and uninsured for any damages. Is that a risk you're willing to expose yourself to?

Just because its designed by an engineer and certified does not mean its going to work. I am sure we have all seen some nice bright and shinny projects turned to cr*p at the push of a button, or towed off by the new owner only to find out the said engineer has only ever sat in his office and never set foot in the real world.

Then again there are some well design projects turned to cr*p because the owner never bothered to throw some grease at the wheel bearings occasionally.

Young's Modulus, the stiffness of metals...... O another flashback I better go lay down.

Tony

Guys the design may not be finished there is always still time to make changes like the trailer bunks i can replace the structual timber 200x75 with 200x100x4mm steel bunks that can run from the rear cross member right up past the chassie bends and past the cross member in front of the bends and bolt it all down

I can easily alter the design i dont mind adding galvanize steel to strengthen it

The bolts are from memory 8.8HT 12mm galvanized as galvanize is the least to cause galvanic corrosion on the scale

Brakes have to be mechanical disc brakes, if i went hydraulic my dogs would chew the pipes and hoses if i went pad brakes they would seize veing submerged

Bit humorous 13 pages into a thread about making holes!

Originally Posted by gazza2009au

Brakes have to be mechanical disc brakes, if i went hydraulic my dogs would chew the pipes and hoses if i went pad brakes they would seize veing submerged

If the dogs can chew through rubber, there are other options. Stainless steel braid and teflon plus 3/16" bundy should deter even a canine which has devoured a pot snack beforehand.

If I were to think about catastrophic trailer failure, the three worst areas I could think of would be drawbar failure, suspension failure or failure of the main chassis rails leading to the first two modes of failure.
I dont think that the main chassis rails will fail catastrophically, however it wouldn't surprise me if there are cracking issues at the ends of the frames in the future. Connection of suspension and drawbar are the two main areas that concern me with this trailer. Bolting through 3mm SHS is a bad idea under any circumstances as the SHS will crush long before the bolts actually begin to tighten properly and this leads to a loose joint that will work and wear in service. There are ways to prevent this such as anti crush tubes, but it is still not a particularly strong joint. Lose your drawbar and you have lost your safety chains leaving a 2000Kg unguided missile heading off at 100 K's. Even if you have breakaway brakes, they will not activate because the switch is still attached to the car.
Much the same applies to the suspension. Lose that, or even lose one side of the suspension and you are up for a rollercoaster ride. From memory, the suspension was to be bolted to the Aluminium, which I have few concerns with, but at some point, the suspension must be fabricated and I think we all have reservations about the standard of welding likely.
Gazza, you struggle with the most basic of workshop tasks. Even drilling a hole becomes a saga of trying to cut corners, blaming your tools and heading around in circles. You seem very impulsive. I respect your desire to have a go and I fully acknowledge that some great Australian innovations were created by people like yourself having a go. The difference that concerns me and I think many of us is your lack of safety, your lack of basic skills and trying to undertake projects that are quite involved on a shoestring budget that leads to design compromises.
We've interacted with you on this forum for a long time and the pattern hasn't changed.