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Swing Arm Why?


paramotormike
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I have wondered for a while now why do we need swinging arms on our paramtors?

1) Helps with torque on take off...... I see a fair number of high and low hangpoint motors with no arms launching OK

2) Helps with weight shift...... Paraglider harness's do not have arms, and I have seen walkerjets and flatops weight shift OK.

Seems to me the number of bolts sheering, cracking, metal fatique etc etc.

Is this the best way? Have manufactuers looked into the fixed low hang points? Or just followed on from the earlier designs of swing arms on a steel frame and cage.

Lower powered engines might have hardly any need for swinging arms???

Any other reasons why we should have them?

Cheers

Mikey

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Well for me it's again as simple as 'it feels better' you get more feedback from the wing.

I see it a bit like power steering. I flew high hang point for 3 years (200+ hours) and would not go back to it unless the 'feedback' issue is sorted.

Once you go to low swing arms, it's hard to think of a reason why you would use anything else.

Ref the worries about breaking pivot points, do your pre flights change the bolts as often as you like (£7) in my case.

SW :D

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Hi Simon.

I was more talking about fixed low hang points. Like with a paraglider.

I too agree, the feel and control of low hang points and ground handling, better brake position etc.

I just wondered why the low hang points have to move, and cannot be fixed as per a paragliding harness.

Other than for the reasons I already mentioned in the original post!

Happy 1500 members +

Cheers

Mikey

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I've been wondering if there's something a bit more clever going on with these swing arms in order to cancel out torque steer / effect under power.

I feel virtually no torque effect from my swing armed PAP.

When I am on full power (eg during take-off). My motor is visibly rotated on my back (as seen in pics people have taken and also the people I fly with have commented on this several times - will try to find a pic).

By rotated I mean it looks like someone has grabbed the outside of the frame and twisted it like the bevel of a divers watch a few degrees.

If I hadn't seen this on pics I would not have felt it myself in flight.

I suspect this is the swing arms allowing the motor to twist rather than imparting torque induced weight shift into the risers/wing. And if the arms were fixed in place this wouldn't be allowed to happen.

Thoughts?

Always a chance I might be talking complete b*))ocks though. It has been known. :D

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I've been wondering if there's something a bit more clever going on with these swing arms in order to cancel out torque steer / effect under power.

I feel virtually no torque effect from my swing armed PAP.

When I am on full power (eg during take-off). My motor is visibly rotated on my back (as seen in pics people have taken and also the people I fly with have commented on this several times - will try to find a pic).

By rotated I mean it looks like someone has grabbed the outside of the frame and twisted it like the bevel of a divers watch a few degrees.

If I hadn't seen this on pics I would not have felt it myself in flight.

I suspect this is the swing arms allowing the motor to twist rather than imparting torque induced weight shift into the risers/wing. And if the arms were fixed in place this wouldn't be allowed to happen.

Thoughts?

Always a chance I might be talking complete b*))ocks though. It has been known. :D

Hi Arcus, all paps have an offset seating position, I think this is more of an attempt to cancel tourqe effect, not sure if the arms do much but I could be wrong :D

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I would argue (being an awkward sod :roll: ) that the hang points on a paragliding harness are not fixed.

Basically there is a strap that goes down from one carabiner, across the seatbase directly under the bum and up again to the other carabiner.

So when I am standing the carabiners are in a different (lower) position in relation to my body than when seated in flight.

I can control the wing during ground handling just by turning my hips, instead of pulling on the brakes.

The Pap system also allows me to do this but of course differs in having metal arms. I believe these are needed to transmit the thrust forces, which a paragliding harness does not have to deal with.

A fixed low hang point system is precisely that, fixed, by the metal framework.

Cheers

Steve

Hi Simon.

I was more talking about fixed low hang points. Like with a paraglider.

I too agree, the feel and control of low hang points and ground handling, better brake position etc.

I just wondered why the low hang points have to move, and cannot be fixed as per a paragliding harness.

Other than for the reasons I already mentioned in the original post!

Happy 1500 members +

Cheers

Mikey

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I would argue (being an awkward sod :roll: ) that the hang points on a paragliding harness are not fixed.

Basically there is a strap that goes down from one carabiner, across the seatbase directly under the bum and up again to the other carabiner.

So when I am standing the carabiners are in a different (lower) position in relation to my body than when seated in flight.

I can control the wing during ground handling just by turning my hips, instead of pulling on the brakes.

The Pap system also allows me to do this but of course differs in having metal arms. I believe these are needed to transmit the thrust forces, which a paragliding harness does not have to deal with.

A fixed low hang point system is precisely that, fixed, by the metal framework.

Cheers

Steve

I agree with steve on this one.

Pete b

Hi Simon.

I was more talking about fixed low hang points. Like with a paraglider.

I too agree, the feel and control of low hang points and ground handling, better brake position etc.

I just wondered why the low hang points have to move, and cannot be fixed as per a paragliding harness.

Other than for the reasons I already mentioned in the original post!

Happy 1500 members +

Cheers

Mikey

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I meet your Michel Carnet with a Matthieu Rouanet and raise you a Ramon Morillas.

Both have been world champions and both fly low hangpoint swinging arm paramotors.

At the end of the day though all that is irrelevant, all that matters is your own personal choice.

Fly it, try it, if you dont like it fair enough.

Just remember that all paramotor designs are a compromise, none are perfect.

Choose your poison.

Cheers

Steve

Here is a quote from the World 2009 Paramotor Champion.

Re: [PilotsPPGclubUK] Swinging Arms....Why?

No, we do not need swinging arms on paramotors.

In my opinion, swinging arms bring no advantage whatsoever, and I think they actually bring more problems in the first place.

Michel Carnet

Cheers

Mikey

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I would argue (also being an awkward sod) that I don’t think it’s irrelevant, if a resonable number of individuals including the world champion are saying they could have potential safety problems????

Has Matthieu Rouanet and Ramon Morillas stated, we do need swing arms and they are totally safe? Maybe they have, I dont know. Michel Carnet has stated that swing arms can pose problems.

If for some of us they are not needed, its one less thing to worry about surely?

Thats all I wondered, are they really needed? Or is fixed low hang points the way to go?

I think this post has run its course, I will not comment any more....but thanks for all the input.

Cheers

Mikey

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If for some of us they are not needed, its one less thing to worry about surely?

Cheers

Mikey

Hi Mikey and nice to meet another "awkward sod" 8)

I agree 100% with your statement that "If for some of us they are not needed, its one less thing to worry about surely"

If you dont want to fly this system, then dont, that's absolutely correct.

You are fully entitled to fly whatever system you choose.

However....

I do see an advantage for me in the low hangpoint swinging arm system and therefore have chosen a Pap. I have based this choice on risk and reward.

Maybe it was a bit strong to say Michel's opinion is irrelevant but I still maintain that my opinion is more important TO ME. Yours is of course more important TO YOU.

Matthieu and Ramon have clearly made their choice for this system as well. All three pilots are exceptional talents who compete strongly at the championships, each seeking the best equipment to suit their different styles.

Is this system totally safe? Of course not, what system is?

For the record, Michels own words in relation to swinging arm low hangpoint systems follow:-

Here are my perceived disadvantages of low swinging arms:

- it is like sitting on a barrel, with every change in throttle resulting in

a movement in pitch and in roll.

- in rough conditions you feel like a rag doll.

- you rely on the thrust to give you the correct attitude. With engine off,

you are reclined and on landing, the cage often touch the ground before the

pilot's feet.

- there is more torque transmitted to the pilot.

- the machine twists 45 degrees on the back of the pilot on launch.

- offset swinging arms are often a weak point on a paramotor chassis'

structure.

- very difficult to fit an efficient speed bar geometry

I have personally never liked that geometry and I am convinced that it is

responsible for many pilots not being happy to fly when conditions are not

100% smooth.

I also understand some pilots do swear by it.

Michel Carnet

I also agree with his assessment. So why do I still choose to fly this system?

I do like that geometry and the comfort issues he mentions dont bother me in the slightest.

The advantages from my point of view are the easiest possible ground handling and a reduction in the effect of torque steer on the wing to such a low level as to be practically irrelevant.

I used to fly a Rad MXL and my stats were I made about 60% of reverse launches and maybe 10% of forwards. I also bust 6 props in 6 months.

I found this to be soul destroying and almost quit.

Now with a Pap I make 99% of all forwards and reverses and last bust a prop in Las Candelas 2009. That was entirely my fault as well for choosing to try in very light and changeable conditions. If I'd been at home I wouldn't have bothered.

I also feel that the latter advantage of negating the effects of torque steer on the wing are not to be under-estimated in respect of safety. Path deviation into an obstacle and the possibility of spin through steering inputs whilst counteracting the torque steer must be factored in.

Cheers

Steve

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There is someone in the USA who has a version of independently swinging under arm bars for high hang point machines. See here http://www.usppa.org/Resources/HomeImpr ... ements.htm and scroll down to weight shift for a .pdf drawing.

For the video, see here

for part 1 and here
for part 2 where he elaborates on some of the explanation missing from part 1.

I have toyed with a couple of idea to modify the existing PAP/ H&E system that does away with the shackles all together. I can't get used to the idea of my life hanging by 2 x 6mm stainless steel bolts through an straight aluminium arm - no soft bushing of sorts. The backup straps appear quite thin too. Just my concerns...

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