UKH

A relative of mine wants to rig a rope swing on a tree for their kid. The problem is that once it's up they can't inspect it very often so the rigging has to be bombproof, abraision proof and weather proof. I was thinking of recommending a stainless steel sport climbing chain with all the proper certifications. I can't seem to find these online so can anyone recommend one? I don't want to use any chain from a hardware shop etc. it must be the proper thing that you would leave on a sports route for a few years at least.

The correct chain should be totally rust proof shouldn't it? I was planning on recommending the chain round the tree branch, held together with a thick stainless steel trianger maillion, and then a 10.5 mm semi-static caving rope hanging from that. What do people think? I'm not really happy with the idea of it not being inspectable. I've jumared up plenty of mystery ropes in caving and trusted random old rope swings as a kid, but when it's for somebody else's kid I want it to be perfect. They aren't really bothered how much it costs as long as it's solid.

Cheers

Lyon Equipment . All sorts of certified slings chains  and wire strops for caving ,climbing,  industrial access.

Some can be sheathed to be kind to the tree.

Great thanks. I don't like it not being inspectable it just goes against the grain for me. But then again kids use all kinds of crap for rope swings don't they and these chains sit at the top of sports routes for years.

I can't find a chain on their website what about this?

https://www.lyonequipment.com/anchors/wire-strops/lyon-galvanised-steel-str...

They don't seem to have a rating though are they not anchors?

I would look at round lifting slings attached to your rope with stainless maillons. Much kinder to the tree than chains or wire strops. Can be as  strong as you like and also a lot cheaper than metal alternatives. They’re easier to inspect than chains/wire strops too.

Thanks. How do they cope with being out in the weather for a year?

Fine. They have a different construction to climbing slings. They have a protective sheath and then endless loops inside. The sheath will no doubt fade in the sun but wouldn’t affect the integrity (unlike a climbing sling). I’d also expect the sheath to wear through eventually but I’d be surprised if this was before the rope needed replacing anyway.

Stainless steel isn't always the magic material people think it is. This is more for interest really as I doubt you are by the sea but SS304 and SS316 (the common grades) are hopeless in marine air and not just in the splash zone.

Carbon steel is a harder material also, although I think you would struggle to notice any difference practically.

I would also second the industrial lifting sling route. The yards tend to cut them when they finished with them so not so easy to get free ones now.

They’re PPE anchors, i.e. they’re rated for the use of one person (2 people in rescue). The minimum breaking strength is in the region of 25kN. 
For comparison the minimum breaking strength of a 2 tonne lifting sling will be in the region of 140kN.

You can't certify chain for use in rock climbing anchors on it's own, it only becomes certified when it's incorporated into an anchor.

OK thanks. What certification should an industrial lifting sling have then?

BS EN 1492-2

e.g. https://www.safetyliftingear.com/products/round-sling-2tonne-lengths-from-0...

Thanks!

I never knew that, explains why I couldn't find one! I think people here are right anyway that a chain wouldn't be best on a tree and an industrial lifting sling is better.

When my brother and I were very young, dad rigged up a swing for us (chain and car tyre) off a big oak in the field. I don't think anybody inspected it from day one. It was still in service 30 years later. On wet days, we'd be quite filthy from the rubber coming off the tyre. How times change...

I know that I am being overkill but that's what they want. I have trusted my life to some shoddy in-situ ropes underground where you get to the top and realise it's rigged off a stal the thickness of a thumb, so I'm not a health and safety freak, it's just different if it's for somebody else's kid. And if they don't care how much it costs then why not go to town with it?

P.S. I've also been injured from failling rope swings as a kid!

Couple of these, some malions and chain would do the trick.

https://www.machinemart.co.uk/c/lifting-straps--strops/

I'd probably just use galv chain, but either way don't mix materials. I.E. no galv to SS.

If I was planning it for someone else, as you are, I would be thinking along similar lines to you. However, about 10 years ago I was in our back garden with my 3-year old son and he asked for a swing so I just dug out an old climbing rope plus an offcut piece of wood and set it up in less than half an hour. I didn't expect it to last more than a few months without some re-work, especially as there was a crack in the wood, I didn't paint it and it was winter at the time.

Needless to say that swing is still up, hasn't had any maintenance yet and has been used by countless adults as well as children.

My solution for anchoring without rubbing was this:

1.Get two pieces of rope (one for each side of the swing) long enough to reach to the ground when doubled up. Clove hitch each of them to branch at their midpoints.

2.Drill a rope-diameter hole in each of the four corners of the seat.

3. Put the four rope ends through the four holes and tie thumb knots tightly.

Every now and again you could slacken the two clove hitches if you were worried about throttling the branch growth but I'm not sure that in 10 years, I ever have done.

PS By doing it this way there is no rubbing on the tree, as mentioned above, but also the load is spread independently through the four corners of the seat. Any one of those could fail and the seat would remain roughly stable through the other three points.

Obviously your choice, but I can't help but feel that even 11mm static would be massively overkill - threaded through some flexi plastic piping (i.e. plastic hose/tubing) to give it abrasion resistance from the tree (and stop it cutting into the branch) and weather resistance. If you're attaching caving rope to it to make the swing, you're still placing reliance on knotted caving rope at the end of the day anyway, at the top where it's going to be just as difficult to inspect.

I would be a bit wary about making recommendations when it is clear you don't have any technical expertise in this area, in case you could be held liable if something were to go wrong.  Whilst this is not quite the same as a professional offering advice, they do appear to be relying on you because of your climbing expertise.  Perhaps I am being over-cautious, but in a similar situation I would simply go back to them with the results of my research and leave it to them to decide what to do.

I don't have expertise in tree rigging but all the things I've suggested are massive overkill. As a kid I used a piece of polyprop and a plank of wood and that was left out in the rain and sun for 5 years or so. Anyway I just showed them a few links to caving rope, maillons and strops/lifting slings with the usual disclaimer that it's just what I would consider using.

Put up this bomb proof tree swing that will outlast the tree, and the first day the kid decides to jump from the top of the swing and breaks a leg.

I'm hoping there is a harness tie in point as well as landing mats in a 5m2 area 😅

I knew this post would get some "When I werra lad" responses but I was asked to recommend kit for an OTT bombroof swing that would last a few years so that's what I'm doing! As a kid I took as many risks with dodgy rigging as anyone else. 

The problem is you end up over designing something that doesn’t actually have to be bombproof. Just has to support the weight of an average adult. Nylon rope has worked for decades in this application. The most likely problem you’ll have is the kid getting tangled in the rope. If it’s stainless steel, that’s going to prove to be a bigger issue to cut through. Then the next likely issue is climbing the rope or chain up into the tree. Then it’s falling off the swing, or out of the tree.
 

Ultimately when it comes to kids, they’ll find ways of making things more dangerous.

The main thing is that they’re supervised to some extent in case the worst does happen. 

I'm assuming the parents will take care of that, it's up to them to supervise. The bombproofness they want is more for weathering etc. If they do use cable it's not for the actual rope it's for throwing around the branch so if the kid gets tangled up in that they they should have been supervised. 

For sure, I was just kidding around.

My dad put up some of that horrible blue pp rope which lasted for decades. The tree fared much worse than that rope. The horrible splinters you got even dissauaded kids from climbing it!

No worries. Don't get me wrong I know that what I'm suggesting is totally overkill, and I knew I would lose a lot of street cred and look like a health and safety freak for asking it, but they did say "what's the most OTT long lasting solution" so there you go. 

Given your mate's requirements I'd be tempted to rig it so it can be pulled down for inspection/removal but cinches up on the branch when loaded so as not to cut the bark. Here's my totally over the top suggestion:

Thread some garden hose (a bit more than branch circumference) and a pop bottle neck/top onto a kernmantle rope, barrel knot a ring (or pair of chain links) onto the end, snug the bottle top over the knot and the hose up into it, tape it in place. Throw the ring over the branch, re-thread the tail through the ring and pull the ring back up into the tree. Tree has room to grow as the noose normally loose, hose/bottle protects tree and rope, noose action stops the rope sawing the branch when used as a swing. Swing can be pulled down for inspection by the ring using a nail in a stick.

jk

In that case all you need is something hard wearing to sleeve the rope and keep it from binding into the tree.

I would say periodic inspection of any equipment should be high priority.

Chains aren't very tree friendly and you should take care putting several kilos of metal above the heads of small kids (without helmets).

Pad the tree and use some old rope to hang the swing.  Use an additional loop to loosely backup the main attachment point, if the primary fails the secondary (which is unstressed through normal usage) will save the day and allow remedial work to take place.

Make it loose so the tree can grow unconstrained. I find it a little sad to see trees strangled round a bit of 30 year old blue tow rope.

A chain will saw through the branch killing it and making the tree the source of concern long before the rope wears out or succumbs the the environment.

Industrial strops and slings (which are protected by a sheaf) can't easily be inspected in situ (work places should have regular inspection routines).

JK's suggestion above is good.

Yes I think that's the best solution. It doesn't need to be OTT if it's inspectable. Thanks you and JK.

Sounds like the only safe option is to cut the tree down.

Get a professional to cut it down. 

We found a rope swing in the woods at the weekend, made from a long length of red polyprop larksfooted over a large branch and then tied to a wooden seat (that had seen better days!) with 2 bowlines.

We did let the kids have a go, we'd seen several much bigger kids trying it and I did inspect the knots - they'd pulled up pretty tight and weren't about to slip. One side had a stopper knot, I added one on the other.

The weak point of the system was most likely going to be wear on the rope at the larksfoot, but far too high to inspect - if we went back, I don't think I'd let them on it and I'd be tempted to chop it down before someone gets injured.

You could cut the tree down when you wanted to inspect the anchor for wear and then re-rig it to a new tree if it passes the inspection. Problem solved.

The most force on a swing and tension in the rope is when you’re travelling the fastest and at the lowest point at the bottom of the swing. Most likely case is the rope breaks and the person on the swing crashes into the ground from a fairly low height. Depends on the length of the rope as to the speed. The tension will not be more than weight of the person. 
 

At least I’m sure that’s what my applied maths says. 

So why do they move in an arc?

jk

Momentum from the moving swing. There’s no more additional forces involved other than gravity. 

What an awesome thread. 

So far we have established -

- that all rope swings are a danger to life unless inspected regularly by an approved authority.

- Trees are not safe to support weight

- marine grade stainless steel is no good in the marine environment

- dissimilar metal will result in instant death when in open air

And maths proves centrifugal force doesn't apply to rope swings

You left out...

- And if you're concerned about a child's well-being and money is no object, you should ask random people on the internet for advice rather than going to a professional.

As the saying goes: You get what you pay for.

probably cut all trees down in the council area

The world has changed.....

Spent my entire youth from about 7-16 hanging around our local park where one particular tree was the focus of the most amazing tree swing imaginable.  It was the job of the older youths to put it up every summer using the blue nylon tow rope from whoevers father we could steal it from.  As you got older, it fell upon you to install the rope.  It would be installed at the same high branch and offered an amazing swing from inside the highest branches whoever was brave enough to scramble up. 

I can remember a few broken bones.  A few injuries but in the grand scheme of things i reckon it served our local community for decades as a meeting place for BMX, bonfires, raiding building sites for 8x4 sheets for ramps and just plain socialising.  Hell i bet a few virginities were lost there.  I remember spending my entire summer holidays there with friends, only popping home for a bite to eat.  Every single boy/girl within a 1mile radius used to meet up there every evening.

If a parent had offered to get involved they would not have had a chance.

Why does everything have to be so risk free?

When is it under tension? At the top of the swing there is no tension. The swing is stationary and the only force is acting down and it is gravity. 
At the bottom of the swing the tension is due to the weight of the person. 
In between those positions there are various components of the horizontal and vertical accelerations which will create various decelerations and ‘restoring’ forces and tension.

The swing will eventually come to rest in the equilibrium position. 

Life is a lot more expensive now.

Only ‘a broken arm’ can impact your future earning potential a huge amount. Ask anyone who has been knocked off their bike and spent weeks off work from only a broken arm and physio. 

At the bottom of the arc the rope supports the swinger's weight (as per the static 'sitting still on a swing' situation) and accelerates their mass toward the centre of the arc, it wouldn't be much of a swing if it didn't.

jk

Hint - centripetal force

I reckon you'd better give up with the applied maths and stick to the day job.

At the top of the arc, you'll be experiencing zero g. There's no tension on the rope and you briefly go into free-fall.  The tension in the rope will increase progressively, slowing down your vertical descent rate and accelerating you forwards at the same time. time.

As you reach the bottom of the arc, you will experience one g plus whatever the centripetal force adds (mass*velocity squared divided by the swing radius).  The further up the arc you go, the greater your speed at the bottom, as potential energy is converted into kinetic energy.  Which means more g force at the bottom.

I seem to remember that in bridge jumps  you can experience up to 2g at the bottom.

Whereas 40 years ago you'd just shrug off a broken arm and get back to ploughing that field?

Which depends on the height of the drop and length of the rope.  
 

In a bridge jump I assume you are at the same height as the point the pendulum is on an incredibly long rope. 
 

What’s your acceleration going to be off a typical swing where you’re probably no more than 2m above the bottom of the arc? 

No. You’d be sat at home trying to decide whether you’d be better off spending your remaining money on food and mortgage, or an expensive lawyer.

One of my son’s friends has just lost her hand after breaking her wrist. Aged 14.  

A reasonable question.

a_max = g + (v^2/r)

2m height change (dh), 4m rope (r):

Converting from GPE to KE: v_max = sqrt(2 x g x dh) = 6.3m/s

a_max = gravity + max_centripetal = 9.8 + (6.3 x 6.3 / 4) = 19.7m/s/s or 2g

The shorter the rope and or the bigger the swing, the higher the peak acceleration.

jk

In a bridge jump, you tie one end to bridge A and the other end to yourself, often clinging to bridge B. The length of the  drop will be slightly less than the distance between the bridges.  So the geometry is pretty close to the maximum on a swing.

To the OP:  if you aim for an adult on the swing pulling 2g with a reserve factor of 5, you ought to have enough strength to stop worrying about it.  Say 10 kN.  And that would still support four kids on it, going for broke with a reserve factor of 2.

Once you've got your rope swing and attachment constructed to a satisfactory safety factor, you've then got to worry about the integrity of the branch to which it's attached.

As there's no way to quantify that, best chop the whole tree down, tarmac it over and install a steel constructed swing with the requisite BS kite mark. Job's done.

I knew lots of people would say 'how times have changed, when I werra lad...' but I'm literally just asking what kit would make the most bombproof and weatherproof swing. I agree industrial slings and caving rope is OTT but that's what they're after. I knew most of it already I just wasn't sure about interactions with the tree and weathering.

I'm not saying the world should be made safe or I would rig a swing llike this for myself or my own kids. I also used crap rope swings as a kid and broken bones etc. I've also done alpine climbing and expedition cavingso it's not like I'm a health and safety freak. Seems like whenever you ask a question here people start assuming an aweful lot about the asker!

Ok. I’ll look at that again when I get home but seems like at maximum point you’re experiencing zero velocity but 1g due to your weight. 

Then at the bottom of the swing you’re experiencing 1g due to your weight plus an additional ‘force’ trying to change your direction. 

It seems too coincidental to me for it to be exactly 2g. These forces are all due to gravity and there’s no additional force or acceleration involved. 

It’s also difficult to follow sometimes because you read the original question and there might be assumptions being made. Then by the time you’ve gone through all the previous posts a lot of the water has got muddied. 

Yes I also think people have automated triggers, they see rope swing, industrial sling, CE rating, then something goes 'ping' and they start typing 'when I werra lad...' etc.

It's not, I rounded and anyway that's just a quirk of the numbers you and I picked (2m drop, 4m rope).

jk

I’m still not convinced. The greatest velocity will be when h = r. 
 

The length of the rope will affect the linear velocity but, from memory, the period of oscillation is proportional to the length. So the acceleration will be less as the rope gets longer as the circle will be bigger and the angular velocity reduces. 
 

I’ll have a look at it later. 

The thread that keeps on giving.... 

Reminds me of a physicist I know. He can go in to great detail explaining what molecules of gases are doing, but can't work out why driving on nearly flat tyres is a problem.

Just curious, but have you actually been on a swing? 🤣 

Yes. When you get horizontal the chains go slack. It’s very hard, if not impossible to go higher than that. That’s the highest you can go. 
The period is 2 PI sqrt(L/g). And not related to the mass. The actual linear velocity will be faster for the longer the rope, but the maximum angular velocity is fixed.

I would have thought the acceleration will depend on the rate of change of velocity and the component towards the centre of the circle will contribute towards the tension and the component around the arc will contribute to the increase or decrease in speed. 
 

I’m interested in what’s going on. 

So that’s interesting. 

If the swing reaches maximum height at 90 degrees to the ground. It will have 2g + g tension at the lowest point. 

That part is actually 2gh/r where h is the maximum height and r the length of the rope. 
 

I’m surprised it’s that high. Is that the same force as you exert against the seat? 

Couldn't you just let people make their own mind up about it?

youtube.com/watch?v=eXFEho2vN7g&

Which will be near enough the same force as the seat, less the mass of the swing parts.

Without meaning to sound callous; shit happens. You can't engineer a risk-free life for all, and if you could I'd wager that it'd cause untold mental harm.

I honestly believe that calculated and sensible risk in everyday life is essential for mental well-being.

If rated and suitably durable slinging really is required, there exists a steel-core nylon roundsling in industry. Commonly used in the events industry for things like slinging trusses to hang from chain. Known as 'gak flex', though probably in the same way that hoovers are known as hoovers. Almost certainly more tree-friendly than a steel strop.

It's 'Gacflex' with a 'c' - the 'gac' stands for 'galvanised aircraft cable'.

Similar construction to a polyester roundsling (aka 'SpanSet' to those who sling trusses), but with a thin galvanised steel rope wrapped round and round inside the outer sheath instead of a loosely woven polyester one.  Unlike a polyester sling they have an inspection port in the sheath and require periodic inspection of the core by sort of shuffling it around inside with a loop poking out of the port like a hernia, which is a huge faff.  Quite expensive, and while they're much more flexible than a conventional steel rope, they're still a lot stiffer and less 'wrappable' than a polyester sling.

I see where you're coming from but honestly, this is a terrible idea. 
(Almost as bad as slinging a tree branch with a stainless steel chain!)

E2A..  Since I'm on this thread now, my 2p:

Don't bother with any kind of sling, just use the rope.  For example by tying a big loop in the end with a fig-8 and larksfooting it around the branch.  Perhaps over a bit of padding, an old sack or something.

If it really needs looking at closely every six months or whatever, get up there and have a look at it.  How hard could that possibly be?  A branch solid enough for a swing is solid enough to lean a ladder against, and it has two strands of caving rope already rigged and hanging off it!  Surely it's at least as important to check the tree for damage as the rope anyway.

Who is advocating a risk-free life? 
 

I think most people are advocating sensible precautions to reduce the risk of injury. The most sensible being to inspect equipment and surrounding for danger and supervise young children. Most people seem to manage that. Of course there are a few people who don’t and for some of them their children get injured or even die. Mainly in kitchens, falls or road accidents. The financial cost of having a brain damaged child will run well into the millions, before you even look at the emotional, psychological and societal damage. 

Noted - I'd always wondered what it actually stood for (but not enough to care, because I tend to watch other people sling trusses ). It's a shame though that the first two companies in the Google results can't spell their own hire stock correctly.

Depends on the circumference of the branch, really? I'm not advocating it, because I'd personally use something 'normal' in a climbing context, but they're frequently wrapped around 50mm OD truss chords. I'm not sure the OP's friends will be using anything skinner as a rigging point, given the need for it to be bombproof! Just putting options out there for further research in the hope that it will lead to bare steel not being wrapped around one of our wooden friends in the name of fun.

For the avoidance of doubt for the thread, I'm fully in the camp that overengineering does not and can not replace inspection.

Course you can go higher than horizontal. Never heard of The Bumps?

E

Apologies if I misinterpreted what you were saying. Sensible precautions are, of course, sensible. Wrapping people (kids, young adults, adults) in cotton wool is not. That is all I meant.

I don't mention 'wrappability' because one of those slings couldn't be wrapped around a branch, obviously it could.  It's more that they're quite stiff and springy and I doubt the weight of a child's swing would be enough to keep them in place.  Not the main reason I think it's a bad idea, just thinking aloud really.

You certainly can't achieve "all the proper certifications" (in the words of the OP) by buying esoteric and expensive kit.  No more so than you already get by using a bit of caving rope instead of nasty blue polyprop anyway.  It's rigorously quality controlled and tested to EN1981.  That's 'proper certification' that is.

If you really needed proper certification in a piece of playground equipment as a whole, which is the only way it would be meaningful, it would have to be designed constructed and installed by someone who needs no advice from anyone here about how to go about it.  And it'd still need to be checked periodically.

Not that there's anything wrong with a home-made improvised approach.  Better yet, maybe teach the kids a few knots, give them the rope and leave them to it.  Who wants a swing when you can have an adventure!

Yep, hence why I didn't just cut it down at the time - I had a knife in the car.

Then why suggest you'd cut it down next time?

I said I'd be "tempted", not that I definitely would. No idea how long it's been there, or when we'll go down there again - next week, it'll probably be fine, 6 months time, maybe not. Maybe someone else will chop it before then, anyway.

If I had the time, I'd take my gear down, get up the tree and assess the bit round the branch before doing anything. The branch is a long way up - whoever put it up there didn't just do it in 5 minutes.

That is very true, and isn't something I'd fully considered. I assumed your reservations were regarding the radius around which it would be bent.

100%

Yes. I meant you can’t go above the horizontal and have it still behave like a simple pendulum. You fall inwards due to gravity when the tension is 0. If it was suspended by rigid poles instead of strings then you could go to 4g+g at the bottom. But suspect the whole dynamics would change because you’re then getting into the territory where it could go over the top and there would be no 0 speed point and the whole thing is in constant motion. It’s then a whole different barrel of motorcycles. 

I still don't see why you might even be tempted?

What's it got to do with you?

If anyone is interested in a long term installation that doesn't kill the tree/ then blocks can be used like this to spare the bark.