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

Originally Posted by gazza2009au

...aluminium trailers carry a massive price tag and most are bolt together quiet strange really

Might be bolted together because welding is just as likely to anneal the aluminium and so rob it of it's strength. Not such a problem if the correct grades and techniques are used.
Fortunately, the engineer who did the calculations on your trailer took that into account, right?

Michael

I am the engineer Michael, this is the aluminium i am using below in pics, was thinking of adding one shs 75x75x5mm steel just in front of the.last cross member just to hel0 with the rear load of the boat and 182kg engine

How much do you reckon the trailer, boat and motor will weigh when finished? Surely you will crack the 2 Tonne mark?

Hey Karl the hull alone weighs 850kg, engine weighs 182kg, the aluminium from capral was marked 90kg

I have added around 70kg of steel 45kg of that actually weighed on bathroom scales

Things i havent weighed

4x 9" wheels
Tow hitch
2x brake disc
2x lazy wheel hubs
4 sets of wheel bearings
Lights
Plastic mudguards
2x 39mm axles rated for 1000kg each
Drawbar
Nuts and bolts
Y plate upper and lower
Winch post/winch
Mechanical brakes

Im hopping boat, motor and trailer come in under 1600kg so i have some allowance for fuel, fishing gear, electronics, if trailer gets stamped 2000kg i'll be happy

Originally Posted by gazza2009au

I am the engineer...

I'm surprised. You've spent 4 years+ at a University studying materials, processes, design, metallurgy and other related subjects but don't seem to understand the theory behind welding, alloying metal, cutting tools or structural design.

Where is your degree from?

Michael

That's straight for the jugular Michael G.
I know where you are coming from though. On a positive note, Gazza will have a go at anything, unfortunately this leads to him punching above his weight at times.
I have reservations about this trailer, although I will say that Gazza does seem to be doing his best to copy an allegedly engineer designed model (I'm not at all impressed with their design from what I can see in their photos).
In my ideal world, Gazza would work on becomming competent in a few areas before moving to more advanced tasks. A lack of funds makes it hard for him too.
Gazza, please don't think were back stabbing you, but the gaps in your skillset are on the verge of biting you hard. Little design points can make masses of difference when you start playing with Aluminium.

on the verge of biting you hard.

I am all for people having a go and attempting things that have some element of risk and them accepting the potential for personal injury, however this project if not suitably engineered has the potential to become something that will bite some poor unsuspecting innocent party coming the opposite way on the road.

Perhaps I may have been a little too pointed, but as you both note, the consequences of this going wrong could be horrific. A poorly made/ designed trailer weighing close to 2 tonnes spearing off because the frame bends or the draw bar snaps could be potentially fatal.

Home made trailers as a 'learn to weld' project are a pet hate of mine as without the skills, they are an accident waiting to happen. I also dislike it when people proclaim themselves 'engineers' without having the background to justify the claim.

Michael

I'm with you and the other respondents to your post, Michel.
On the other hand, I just bought a used commercially designed and built trailer from a well-known Australian manufacturer. I need to modify it to my needs, so examined the construction in considerable detail. I was horrified to be honest.
I'm NOT an engineer, but I can read and understand sophisticated mathematics and physics sources to get the right information.
This trailer will be much safer after my modifications....
So copying a certified design is still no guarantee of safety. KNOWLEDGE is!

Gazza: please get the KNOWLEDGE, not necessarily the qualifications - and recognise that there are things you don't know you don't know. Some of your questions make it clear that you need to get help to find out what those gaps are.
So keep asking questions here and don't take anything for granted that looks OK to you.

PS: over the past two years I've been doing welding subjects at TAFE to improve the quality of my welding and keep my brain going.
I did about 120 hrs aluminium TIG welding in that time. I now KNOW that I would NEVER do any aluminium chassis welding EVER!

Cheers
Joe

Has he actually done any welding on the aluminium sections? It looks like he has bolted everything to me.

That was exactly the point respondents here made: to deter Gazza from welding anything.

Cheers
Joe

Fair suck of the sav fellas...
He might drive a train Monday to Friday.

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?

Happy to!
But be aware I'm not an engineer.
I can't see any criticism in the past few posts - and no direct question for advice...

I think you might be on the right track with the addition of another cross member at the back. Please bolt it on
Do you know how to calculate bending moments of your sections? Have you checked that they are in the ballpark?

The other thing I would do if it was my trailer is to add a diagonal bracing member somewhere near the spring hangers. With the length of this trailer, there is a risk of the middle and rear part getting bent if you hit a pothole or a kerb or whatever with ONE wheel ONLY. Tbe bracing achieved by the drawbar triangle will hopefully prevent the front from getting skewed or racked, but there is nothing rearward from the bends in the chassis rails back to transmit longitudinal forces across the chassis.
Hope that helps.

Originally Posted by jhovel

Happy to!
But be aware I'm not an engineer.
I can't see any criticism in the past few posts - and no direct question for advice...

I think you might be on the right track with the addition of another cross member at the back. Please bolt it on
Do you know how to calculate bending moments of your sections? Have you checked that they are in the ballpark?

The other thing I would do if it was my trailer is to add a diagonal bracing member somewhere near the spring hangers. With the length of this trailer, there is a risk of the middle and rear part getting bent if you hit a pothole or a kerb or whatever with ONE wheel ONLY. Tbe bracing achieved by the drawbar triangle will hopefully prevent the front from getting skewed or racked, but there is nothing rearward from the bends in the chassis rails back to transmit longitudinal forces across the chassis.
Hope that helps.

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?

I will be adding the extra 2 bars to the square section in X form thanks for mentioning this i have a rough idea how to make it and attach it