BIG span tables needed.

[Bleedin Thumb]

Sorry to disturb you kind folk but I need to get a single span of 4 m (Class one, unseasoned select grade HW, grey ironbark or spotted Gum) for an out door swingset and my tables dont go that far. Can anyone give me a dimension?

Preferably a square section ......I dont know how that works...mostly they are rectangular .....

Is there a formula that for example if the Tables say 150 x 50 will say span 2m then by reducing the height by 50% to 75 mm and increasing the width by 50% to 75 mm IE 75 x 75 will span 2m??? (probably not).

How about taking 50mm off the Height and adding the same to width IE 100 x 100mm ?

Or is it a case of once I establish that the height is 150 and I want it square I will have to go 150 x 150?


This may seem stupid but I always find when I'm designing that those rotten span tables never fit the bill!

For example with this swing. the forces acting on it are not just gravity but a sideways twist that would be best served by a square cross member.

Anyhow thanks in advanced.

[les88]

what about a treated pine log
les

[Bleedin Thumb]

I would still need to make sure the TP was within specification and I will get a longer span for the dimension with HW....and HW looks better.

Also I need to mount the cross beam on uprights - one of which is on a 30% rake - this would make a joint with round members very difficult.......well ugly anyway.

God I wish for the days when you would just look at a bit of timber and know that it would do the job with out the fear that some Nazi would come along and reject it.

[les88]

Ok no log..try 10 x 2 or 9 x 3 inches. the strength comes with the depth so
square will not be as strong. Bolt it to the uprights it will not move with the swings
les

[Bleedin Thumb]

Thanks Less but some of the fittings are 50mm square plate mounts attached with coach screws so you can see why I'm after a square section.

Also as its for a playground I shouldn't really guess ...I need to be able to justify my choice through some sort of span table ...otherwise I'd just specify using old wharf timber 300 x 300......well my gut feeling is actually 125 x 125.

Edit Sorry I have worked out what I need to do. The beam needs to be 150 x 150 but I have reduced the load on it by using the cantalevered upright as part of the span effectively reducing my span to 2.3m whilst still leaving the distance between the posts on the ground at 4 metres. I will also use 150 x 75 twin uprights on either side of the beam as supports.

Thanks for your help Less.:)

I'll try to reduce the drawing and post it up

[journeyman Mick]

BT,
hard to tell really as span tables aren't really designed for the sort of dynamic loads that a kid on the end of a swing would impose. You could get an engineer to do the calculations or you could just over engineer it like crazy. The other thing you could think about would be to sandwich tow rectangular beams topgether to get your square beam but let a bit of steel into the centre of it for insurance.

Mick

[Bleedin Thumb]

Hi Mick, I don't think the forces are too great , just strange angles. I'm incorporating a multi child horizontal tyre swing with a single pivot that will be the worst . Infact I've decided to go 200 x 200 to overkill it...we dont need any kidies being launched into space.:D

[UteMad]

Can't use treated pine logs for play equipment anymore anyway... Why not just get a gal steel tube which would be way easier to fix all your swings to... You can get a size of the council ones in the parks....
I'd reckon 5 inch dia would kill it... Cause most swings are out of 150 dia logs

cheers Utemad

[Bleedin Thumb]

You can use treated pine Utemad, just not CCA treated.

I am actually pulling done about $10K worth of steel stuff to build the wooden multi use swings - natural materials in jungle type settings is my signiture - as opposed to bright colours, fixed equipment in a sterile enviroment that is increasingly the norm.

Pity really because steel would be easier:-

[bese]

is that a photo of hunter s thompson.

[Bleedin Thumb]

Don't be rude! Even though I have the greatest regard for the venerable Doctor I have never had any professional allegiances with the said father of Gonzo.