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Trailer chassis design help
https://www.ausmini.com/forums/viewtopic.php?f=2&t=50899		 Page 1 of 1
Author:  Kennomini [ Thu Mar 05, 2009 4:49 pm ]
Post subject:  Trailer chassis design help
Ok for my mini trailer I'm building I'm at the stage of making the chase and draw bar. I'm just not sure on what chassis design to build so here are most of my options.
The chassis will be made out of 50mm square box section and if I make an A frame draw bar that section will be 50mm right angle.
This is how the chassis will basically be, the trailer has a solid axle and leaf springs. The front of teh trailer is at the top of the pic.Now theirs the A frame,
ImageImage
The single bar, I prefer this look but not sure if it will be strong enough :? .__________________________A combination of the two,
ImageImage
Or a shorter chassis design,
ImageImage
The trailer will be registered for 750 kg and may be towed behind other cars in the future so I want a design that's strong but still light weight. Also How long should I have the draw bar and what's a good height for a tow ball on a mini :?: If any of you have any ideas feel free to copy an image to paint and show me what you think :) .
Author:  albino235 [ Thu Mar 05, 2009 5:00 pm ]
Post subject: 
50mm equal angle probably won't be sufficient for the draw bar. Check the regulations for trailers, there are requirements for the strengths and loads that the draw bar must take to be legal.

Further to this trailer design should not be left to guess work or popular opinion generated through the internet. The trailer members must be designed to take the loads applied to them, so if you can't perform the calculations to find the sizes then get an engineer to help you.

Just remember if your trailer falls apart and kills someone you will be the one that goes to jail. Do it properly or don't do it at all it's simply not worth the risk.
Author:  awdmoke [ Thu Mar 05, 2009 5:14 pm ]
Post subject: 
Single bar. It's strong enough for offroad camper trailers.
If kept reasonably short, I would go with 50x3 SHS.
Remember that as well as being inherently stronger than angle, structural tubular sections are also made from higher strength steel
e.g. angle 300MPa < SHS 450MPa
Author:  frednutz&co [ Thu Mar 05, 2009 5:29 pm ]
Post subject: 
mine is 50mm square tube 4mm thick single bar welded to 6mm plate bolted to mini subframe.only using the rear section of a clubbie body.
seems to be strong enough .only carries folding chairs,tent folding table and a small BBQ.
Author:  EAB [ Thu Mar 05, 2009 6:35 pm ]
Post subject: 
make up your square base first. then weld your actual towing arms to the bottom of it. youll end up with the full fram under your trailer bed/floor
and the bars in the second last pic, so you get a sort of extended a frame

Image

Wheels on centre bar you extend your bars back to at least where your springs attach. that way you can also make it a tipping trailer if your getting a little crazy.
Author:  Kennomini [ Thu Mar 05, 2009 7:17 pm ]
Post subject: 
albino235 I see a lot of trailers with right angle for their draw bars, our 6x4 trailer has it and it manages fine. I know their are engineers and other people that have a good idea on what their talking about on here so I'm just trying to get an idea of what could work and what wont. I have thought about checking with an engineer so I might drop into one sometime and see what their opinion is.
EAB that's a stronger design than what I had, a tipper trailer is tempting but I think to keep the weight down I might not do it this time :roll: .
Author:  albino235 [ Thu Mar 05, 2009 7:42 pm ]
Post subject: 
Kennomini wrote:
albino235 I see a lot of trailers with right angle for their draw bars, our 6x4 trailer has it and it manages fine. I know their are engineers and other people that have a good idea on what their talking about on here so I'm just trying to get an idea of what could work and what wont. I have thought about checking with an engineer so I might drop into one sometime and see what their opinion is.
EAB that's a stronger design than what I had, a tipper trailer is tempting but I think to keep the weight down I might not do it this time :roll: .


I'm not trying to have a go at you or anyone specifically, I'm simply voicing my opinion in that trailer design is not something to be taken lightly.

But to make the thread productive, here is a link to the small trailer building code of practise. See section 12.1 for draw bars.
Author:  Kennomini [ Thu Mar 05, 2009 8:10 pm ]
Post subject: 
Don't worry I didn't think you were having a go or anything and I do agree with what you said. Is that link for any state in particular or is that Australia wide?
Author:  sgc [ Thu Mar 05, 2009 8:43 pm ]
Post subject: 
Kennomini wrote:
Is that link for any state in particular or is that Australia wide?


Most of the states' vehicle safety regulations are compatible.. if it passes that, it'll probably pass any in the country.
Author:  albino235 [ Thu Mar 05, 2009 9:50 pm ]
Post subject: 
As far as I'm aware that bulletin is a summarized set of the requirements of small trailers and is a National code. I would hope/expect that that bulletin is mirrored in the state legislation.
Author:  1310/71 [ Fri Mar 06, 2009 7:03 am ]
Post subject: 
albino235 wrote:
As far as I'm aware that bulletin is a summarized set of the requirements of small trailers and is a National code. I would hope/expect that that bulletin is mirrored in the state legislation.


That's my understanding too - it's a national code.
KB
Author:  mickmini [ Sat Mar 07, 2009 12:23 am ]
Post subject: 
albino235 wrote:
As far as I'm aware that bulletin is a summarized set of the requirements of small trailers and is a National code. I would hope/expect that that bulletin is mirrored in the state legislation.


unfortunately this is not always the case and it is never wise to assume. Yes it is a good idea to use the bulletin as a basis, but before you cut steel, make sure that what you design is also compatible with your state registration authority regulations.

cheers
michael
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