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Old 14 September 2012, 07:08   #71
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Could you not have kept the 150kg on the tow hitch where it doesn't count?
Nope. The law says that any car registered on or after 1st August 1998 must have a type approved towbar, tested to EC94/20. My car was registered in 2003 so my car has to have one, and the plate says it can only take maxiumum nose weight of 50kg!
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Old 14 September 2012, 07:30   #72
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You obviously haven't studied structural engineering then!...
Sounds like you slept through a few lessons yourself.

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Old 14 September 2012, 07:37   #73
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Originally Posted by jeepster

You obviously haven't studied structural engineering then!...The holes in question, called lightening holes (because they lighten the structure), do not weaken the structure, they actually increase the strength to weight ratio...Which is why lightening holes are applied to RSJ's whichare required to span very large gaps between supports, such as in modern open plan warehouses with the minimum of support pillars.
They would also give me convenient access to the inside walls of the RHS for ease of painting.
Even more brilliance...!

Allow me to pass on one of my favourite sayings....

"its always better to let people think your an idiot rather then open your mouth and remove all doubt!"

Simon.

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Old 14 September 2012, 07:53   #74
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This thread has brightened up my lunchtime no end!
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Old 14 September 2012, 08:30   #75
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[QUOTE=Anchorhandler;487680]Even without drilling holes in the fecking side rails that rectangular section tube is probably just on its strength limits and you want to go and weaken it even more!...

Drilling lightening holes in the side rails wont necessarily weaken the trailer, but they will greatly increase its strength to weight ratio. Its why lightening holes are used on RSJ's that are required to span huge gaps in modern warehouses with the only a support being a wall at either end...Without the lightening holes the RSJ beams would sag under their own weight.
Having lots of holes in a structure to increase it strength to weight ratio is nothing new...The Wellington bomber had one of the strongest airframes produced during the war, but this was due to its geodesic structure which was largely full of holes!

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Think about it, at the moment you have nearly a quarter of a ton bouncing up and down a meter or so either side of the fulcrum ( the axle) ... !!!
Well the boat is not actually bouncing on the trailer, the suspension sees to that.

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Honestly, stand at the back of the trailer and look down the length of those side rails and tell me there not significantly bending under the weight.... When i say significantly i mean anything more than a10mm deflection down its length.

Any beam will deflect, even under its own weight...The beauty of using steel is that it can deflect a long way before permanently deformation of the structure. BTW, adding holes increases the strength to weight ratio, which can actually reduce delection, not increase it.


If you let me know exactly what the rails dimensions are and what distance from the axle mounts the swing beams connect to them, l will work out how much weight you put though it....better safe than sorry..

Simon
Be my guest...Measuring along the side of the rails, the rails are 5.5m long exactly. The axle is 1550mm from the rear end of the rails. The rear swingbeam is 1375mm aft of the axle (175mm ahead of the rear end of the rails) and the front swingbeam is 710mm ahead of the axle. The main cross beam (the rear member of the I frame) is 1810mm ahead of the axle and 245mm aft of the 20% bend in each of the the side rails.
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Old 14 September 2012, 08:33   #76
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Excellent and I'm glad you've upped that to a 99 ... that should blow the louvre doors off anyway
Er, it only a 9.9hp!
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Old 14 September 2012, 08:37   #77
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My comments were regards advice given on other forums by a user of the same name as yourself....
And what bit of this advice did you consider shite exactly?
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Old 14 September 2012, 09:09   #78
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Quote:
Originally Posted by jeepster;487748B
...Measuring along the side of the rails, the rails are 5.5m long exactly. The axle is 1550mm from the rear end of the rails. The rear swingbeam is 1375mm aft of the axle (175mm ahead of the rear end of the rails) and the front swingbeam is 710mm ahead of the axle. The main cross beam (the rear member of the I frame) is 1810mm ahead of the axle and 245mm aft of the 20% bend in each of the the side rails.

Jesus....if ever we needed (more) proof that you have no idea what your talking about then ....HOW AM I SUPPOSED TO CALCULATE THE MAXIMUM POSSIBLE LOADING ON YOUR SIDE RAILS WITHOUT THE DIMENTIONS (AND THICKNESS) OF THE SIDE RAILS THEMSELVES.

I cant beleive i'm going to waste my time explaining this to you but a rectangular section tube will posess about 80% of its longitudinal strength in the side wals. (when used in the vertical manner as your trailer is).

Lightning holes are sometimes cut into brackets and fashion plates to reduce weight as you quite rightly say BUT ARE NEVER CUT INTO A SINGLE LOAD BEARING BEAM as your side rails are. Even when lightning holes are added, the potential loss in strength will always be calculated.

Now bearing in mind that your rails ARE THE MAIN LOAD BEARING STRUCTURE of your trailer, do you really want to go and cut fecking holes all over them...especially on their sides? ...

Simon
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Old 14 September 2012, 09:15   #79
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Originally Posted by jeepster View Post
You obviously haven't studied structural engineering then!...The holes in question, called lightening holes (because they lighten the structure), do not weaken the structure, they actually increase the strength to weight ratio...Which is why lightening holes are applied to RSJ's whichare required to span very large gaps between supports, such as in modern open plan warehouses with the minimum of support pillars.
They would also give me convenient access to the inside walls of the RHS for ease of painting.
You may well increase the strength to weight ratio, but that is very different to increasing the strength of something!!!
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Old 14 September 2012, 09:44   #80
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Jesus....if ever we needed (more) proof that you have no idea what your talking about then ....HOW AM I SUPPOSED TO CALCULATE THE MAXIMUM POSSIBLE LOADING ON YOUR SIDE RAILS WITHOUT THE DIMENTIONS (AND THICKNESS) OF THE SIDE RAILS THEMSELVES.
See post 1: 80x40x3 RHS
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