Drilling holes to lighten girders

[fizzy]

Well universal columns as they are known.
I am building a trailer using 2x 100mm columns as side rails. Or H girders or whatever you want to call them. They are very heavy - 21kg per metre!

Top and bottom are 10mm and the web is 6mm. Always wonder why it isn't the web that is thicker.

Anyway I was wondering about drilling a load of holes to make them a bit lighter as they are way over the top for what I need. I have my new Mag drill to play with as well.

Obviously holes not too close together etc etc. Is it OK to drill through the web as well although most of the weight to be honest is in the 10mm tops and bottoms.

Anyone got any links on where and how much you can drill etc?

 

[AndyStobbs]

Be better to cut them in half and use them as T section I would say. Just setting yourself up for an awful lot of drilling.

 

[fizzy]

No they need to be used as H section for mounting. This trailer is a one off and I am being a bit obsessive with it - Rolls Royce or should I say the Brunel or trailers!

Besides which how else can I justify a brand new Mag Drill for a hobby?

 

[normspanners]

the strength in h section is not the web it is the two flat sections, the web just holds the two flat sections apart, if you try to bent it you are basically trying to compress the bottom one and stretch the top one, thatis where it gets the strength from. It is/was common practise to cut hexagon shapes out to lighten and save steel, in girders with no detriment to the strength
http://zzhz.com/News/doc691.html
this is not exactly the same but gives you an idea.

 

[fizzy]

Just a tad heavier duty than mine!

All the girders I have seen have also had the webs drilled but they are only feeble 6mm - all the weight is in the top and bottom. Would look cool though!

I think I will drill a load of 16mm holes both side of the web along the bottom. The other advantage is that I can reposition the trailer for balance as it will be bolted onto the chassis.

 

[normspanners]

Besides which how else can I justify a brand new Mag Drill for a hobby?

Mind you your going to need a funny hole saw to cut hexagons!

 

[KemppiFrog]

Just a tad heavier duty than mine!

All the girders I have seen have also had the webs drilled but they are only feeble 6mm - all the weight is in the top and bottom. Would look cool though!

I think I will drill a load of 16mm holes both side of the web along the bottom. The other advantage is that I can reposition the trailer for balance as it will be bolted onto the chassis.

Err..no.

As Norm says, the web is to keep the top and bottom apart, so they can do their job. If you must drill holes, do it along the centre line of the web. The stresses on the web are nearly neutral there and increase as they get closer to the top and bottom of the beam. Drilling them in the top or bottom will seriously weaken the beam. If it is strong enough to cope with that, then it is well over sized for the job and heavy.

 

[fizzy]

It IS well oversized - the trailer is to tow behind my Landie. I have a 3.5ton axle for it.
It will weight about 800kg so carrying capacity will be about 2700kg.
Will carry a mini digger or loads of wood. Size will be 8x5x4.
I will have to post some pics in the project section.

 

[awemawson]

The classic lightening method is to cut the web into dragons teeth - shift so the points touch, then weld it back together. It doubles the separation and halves the weight of the web.

Andrew

 

[wristpin]

Essential reading?

http://www.trailerforum.co.uk/showthread.php?t=162673

 

[fizzy]

Essential reading?

http://www.trailerforum.co.uk/showthread.php?t=162673

Yes yes yes
chassis is already built and plated - just bolting a box onto it!
And I finished it months ago.........

 

[fizzy]

Oh and the first 2 links dont work!

 

[outofthefire]

They are way over spec I build wagons for a living and only seriously heavy duty trailers use h beams. By the time you've added your bearers and floor and sides your trailer'll probably weigh 3.5tons

 

[bigegg]

Well universal columns as they are known.
I am building a trailer using 2x 100mm columns as side rails. Or H girders or whatever you want to call them. They are very heavy - 21kg per metre!

I'd be tempted to visit one of my local steel suppliers , or the local scrappie, and ask them if they'd do a straight swap for something lighter - like some 150x50x3mm C section.

If you then needed the "H" section, I'd bolt two pieces together back to back .
21kgs/m over 3m? each side = 120kgs. The c section would be half that - and give you extra carrying capacity.

I read somewhere that the art of engineering is not in over-building, it's in building in JUST enough strength (+10%)

 

[fizzy]

The Victorians massively over engineered - and the stuff is still standing!

 

[bigegg]

It's your petrol you're burning...

 

[fizzy]

I honestly use LESS fuel the bigger the thing I tow - because I have to drive a lot slower!

 

[RonA]

Castellated beams

Well universal columns as they are known.
I am building a trailer using 2x 100mm columns as side rails. Or H girders or whatever you want to call them. They are very heavy - 21kg per metre!

Top and bottom are 10mm and the web is 6mm. Always wonder why it isn't the web that is thicker.

Anyway I was wondering about drilling a load of holes to make them a bit lighter as they are way over the top for what I need. I have my new Mag drill to play with as well.

Obviously holes not too close together etc etc. Is it OK to drill through the web as well although most of the weight to be honest is in the 10mm tops and bottoms.


Anyone got any links on where and how much you can drill etc?

I used to work for British Steel & we used to produce castellated beams to reduce weight but retain strength, basically the beam web was cut down the middle, triangular shapes were then cut out of both sides of web & then the two sides were welded.back together to form a beam with 4 sided lozenge shapes cut.out of it.

RonA

 

[dan.taylor.1]

Honestly think your way over engineering it, our 3.5t Ifor has like 150/50/4 folder c section for its frame rails and I've never seen one break yet unless in a bad accident or seriously overloaded.

Dan

 

[MattF]

The Victorians massively over engineered - and the stuff is still standing!

They weren't lugging their structures behind a vehicle. Over engineered is a misleading term for a lot of their stuff anyhow. It was well engineered, not necessarily overly.

Driving slowly doesn't mean you're using less fuel either. Lugging unnecessary weight will negate any fuel saving you might make and then use some more. It's extra weight to bog down, extra stress on the towing vehicle, towbar etc. Unless you're planning on whacking it behind a tractor and towing/dragging/abusing it, the design and weight is just excessive and unnecessary. That's also a hell of a lot of extra weight to brake.