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MG Midget and Sprite Technical - A-frame structure tolerances (NMC)

Sorry no midget content here at all.

Im planning to build an A-frame based swing frame for my son's second birthday in March.

Ive found a free plan for a bench swing frame. It does'nt specifiy what sort of wieght capacity it can handle, does anyone know who to guestimate this? It will be made from 4x4 posts, like fence posts. I also plan to scale it down slightly, so any advice on how to scale down a plan is welcomed ( i guess its just a case of taking a % off all the measurments?!)

http://www.buildeazy.com/newserve/swing_seat_support_dec07_1.html
Rob McGeown

4x4 posts should be be fine. If you son's anything like I was as a kid then it needs to cope with "non-conventional" usage - eg swinging sidewards, spinning, carrying three people at once, etc etc. Make sure the base is wide so it doesn't topple over.

The swing my dad made for us was big enough for an adult, tested by an adult (ie him), and the chains were adjustable so that as we grew older he could just bolt it up to the next link to make the seat higher. It has served three of us from infancy to present day, simultaneously at times, and I'm 34 now!

It is held firm in a substantial amount of concrete :)

Ant
Ant Allen

If you are using chains, then just be aware that the links are great for small people to poke their fingers into - possibly with painful and messy results. Ropes might be better. You also need to be watchful for any scissor action as in one part moving too closely across another.
Guy Weller

Rob,
I reckon if you build it solidly out of 4x4 and use some good quality bolts it should take any weight. Id' scale it up not down and make it as tall as possible so you can get a really good long swing. You can have a cradle type seat on ropes initially but he'll grow up only too quickly and a long pendulum length swing will keep him going into adulthood and beyond......
Matt 1275 Bucks

You could always convert it into a love swing and go for child#3...

Ropes might need to be a tad softer than hessian...or maybe not!
Toby Anscombe

Build the main frame of 4 X 4 box section steel with fittings to take an Aldi £50 electric hoist and you can use it for lifting engines with as well! Who said NMC?

Guy
Guy Weller

Just built one for my kids (ie ME)
used 70x70mm for the uprights and 90x90mm for the horizontal and its strong enough.
a couple of points I would make are firstly that he seems to have just looped the chain over the horizontal, may be OK for a bench but not sure it will be for a kiddies swing where you need a single chain connecting to the seat.I used an Eye bolt through the horizontal with cleats to attach the chains and make them easy to remove. Secondly make sure the width between the chains is a bit wider at the top than at the seat end, makes it more stable when your swinging (sorry, meant when the kids are swinging).
Guy, couldnt get my midget under the swing to pull the engine out but did use the chains for exactly that in the garage.
Mike (italy)
sm storey

Oh another "feature" of the one my dad built - the chains have two pieces of plastic gas pipe slid over them to prevent getting rusty hands. I guess that's why we never had the damaged fingers issue too :o)
Ant Allen

the next issue i have is finding the timber at a decent price! Any inisde knowledge?
Rob McGeown

Isn't there a whole load on a beach somewhere in UK?

A
Anthony Cutler

I would not use nail plate fixings for kids play equipment due to them loosening with time and abuse.

I think that a coach bolted with spiky washers between the joints would be far better. If you look at the climbing frames on the web you'll see what I mean


For timber you could use shaved logs rather than 4x4, the logs can be bought tanalised and should be cheaper and longer lasting. Any decent builders merchants should be able to get them for you.
robnrrugby

Rob

Im sorry, but I DO NOT LIKE that design at all (Im vary serious)

This thing is going to carry alot of mometume vary fast....Id think a 60lbs child could turn into 240lbs of mass vary fast and that does not include the bench which looks like it could wiegh 100 lbs vary easily by its self....please call and talk to a house stud framer for better ideas on building an A-frame swing, they work with these forces every day, and im sure the info will be free

Once that bench goes beyound the back side of the A-Frame its going to continue carrying the momentum to the back side where there is nothing to keep it from flipping over, once its maxed out it will go back the other direction (AKA remember high school physics class...potential vs kenetic energy) and agian once it has passed the front of the A-frame, there is going to be alot of (continually growing Potential energy thats going to want to convert to kenetic energy by way of the path of least resistance) 1. fall over in a front ward direction or 2 break at those nail patch joints. or hopefully 3. do what its supposed to do.

If you do build this, anchor it in concrete (LOTS of concrete) and use lag bolts instead of nail patch plates

Personally you cant beat a big tree, with an old tire and a rope

Agian sorry, but please dont use this design with out massive modifation for the safty of your children.

Prop
Prop***The End in 2012

Rob, Props right about the concrete and bolts although maybe "Id think a 60lbs child could turn into 240lbs of mass vary fast " isnt quite as bad in the UK - yet !
With the timber I used the pre-treated stuff used for decking and treated the ends to about 10cm above where they are concreted into the ground.
Mike (italy)
sm storey

Wo, steady on prop!

Thanks for your concern, i have already resolved to use M12 coach bolts and nylocs throught in place of the nail plates.

Im not making the seat, ill use a std plastic swing seat.

It will be made with pressure treated timber, not the rough fence posts in the design. Either that or mahchine round posts, 75-100mm in diameter.
Rob McGeown

This thread was discussed between 12/02/2009 and 13/02/2009

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