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Do you use a Clutch or not?


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I should be buying my paramotor in the next three months if all goes as planned and I'm definitely not gonna get a clutch. It's just an additional wear item that needs replacing every so many hours (I've heard as few as 15 in some cases), and it slightly decreases your overall power. That, and it makes the unit more expensive. Those are the main reasons why I don't want one. 

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Clutch is good. You can land engine on and prop not turning...so you have engine ready if need to go around, but no risk of lines in a spinning prop when you land.

Clutch does not reduce power, how can it. Provided clutch is not slipping then it locks the engine output to the pulley.

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I have had both with and without a clutch . Both have advantages and disadvantages.

Clutch ...PROS -smoother when on idle , Less likely to catch a line whilst launching  .CONS ...a little less responsive to power up , something else to maintain , if you hit the kill switch then prop still spins for a while.....

No clutch ..PROS ...Lighter weight ,prop stops instantly when I hit the kill switch , Less maintenance. CONS .....paramotor shakes on idle , I have caught lines in the prop launching . .I may have missed a few things . but I prefer no clutch.

Also and engine running with no prop turning gives a false sense on safety. My engine a prop turn together and you never forget the dangers.I have seen a new pilot play with his throttle cruise control without holding then paramotor frame whilst the engine was running . The frame thrusted forward ..he was fortunate not to have a accident.

Hope this helps a little. 

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Clutched or no clutch air conceptions are both excellent machines . If you are a complete beginner a clutched model may be best . ..you will be less likely to catch a line if you don't launch the wing correctly .The nitro 200 is so light that the extra weight of a clutch is insignificant .They are also very reliable .

 

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15 hours ago, AndyB said:

Clutch does not reduce power, how can it. Provided clutch is not slipping then it locks the engine output to the pulley.

Everything I've read up to this point says if you have the two same engines, one with a clutch and one without, the one without will get more power to the prop. Something about the direct drive sending 100% of the power to the prop, whereas some of that is lost with a clutch. 

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6 hours ago, The80s said:

Everything I've read up to this point says if you have the two same engines, one with a clutch and one without, the one without will get more power to the prop. Something about the direct drive sending 100% of the power to the prop, whereas some of that is lost with a clutch. 

A clutch, when in the locked position cannot lose any power. It would have to slip to lose power....and then it would get very hot and not last very long. Maybe you are confusing machines with gearboxes with those that use belt drives?

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Scout video on clutch or not

I don't use a clutch because the machine I bought was 2nd hand and there was not much choice.  While technically they do add a layer of complexity they are pretty simple devices on millions and millions of chainsaws and scooters and are not difficult to check or replace.  There are just too many advantages compared to non-clutched IMHO.  And for sure they do not rob power unless slipping.  Same as a belt! 

I do agree that seeing them as a safety device in terms of ground starting can give a false sense of security.  

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Guest chrisg547

I started without a clutch. Then when I got a Thor200 with clutch I wasn't sure I liked it, as it was a bit different. Ive since owned 2 Mosters with clutch and now I wouldn't want to buy a motor without one. If you are struggling to get the engine going, then its easy to take off the prop. And then you don't have to worry about damaging the engine or risk losing bit and bobs if the motor runs up to max rpm.

Still its a personal preference.

 

Edited by chrisg547
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Hi 

As I understand  if you do thermals  with the motor switched off you want the propeller to be stationary  as a free spinning  propellor will create more drag.

I fly both types but prefer the clutched ,,the only issue I had was with  my cruising speed and clutch bite point very  close together  on low level beach flying.

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3 hours ago, noddyc said:

As I understand  if you do thermals  with the motor switched off you want the propeller to be stationary  as a free spinning  propellor will create more drag.

A free spinning prop creates LESS drag than a fixed one. A fixed prop is forced to move air as it pushes through it. A free spinning prop is pushed sideways out of the way, thus not moving air, just spinning.

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23 hours ago, AndyB said:

A free spinning prop creates LESS drag than a fixed one. A fixed prop is forced to move air as it pushes through it. A free spinning prop is pushed sideways out of the way, thus not moving air, just spinning.

Are you sure about that. My experience with model aircraft and full size helicopters tells me there is more drag with a rotating prop. After all, a helicopter without power falls a lot quicker without a turning blade, as per a Sycamore leaf.

 

Trevor.

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6 minutes ago, Trevsked said:

Are you sure about that. My experience with model aircraft and full size helicopters tells me there is more drag with a rotating prop. After all, a helicopter without power falls a lot quicker without a turning blade, as per a Sycamore leaf.

 

Trevor.

Yes, I am sure. It is basic fluid dynamics. 

With a heli with engine out, autorotation  is used so that the blades speed up, storing energy. Autoroation is like having a clutch - the blades are free to rotate without engine drive. That energy is then used before hitting the ground, by increasing the angle of attack and hence slowing the fall. 

A heli for some reason in the air with stationary prop would be called a brick, it has no aerodynamic lift. A flying heli with blades spinning, but engine failure, still has the energy stored in the blades to slow it's descent.

A heli that starts its fall with stationary (fixed) blades has the same aerodynamic force on the blades as the spinning ones. In the stationary case the force continually slows the descent of the machine, but there is no stored energy to use to slow descent near the ground. Allowing the blades to spin stores that same energy so it can all be used just before the ground arrives. 

 

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I think the opposite, a spinning prop have a much bigger area that will create drag, Even if it's an aerofoil, it's not pitched for the angle it needs to have. Sure it's less pressure on the blade as it spinns, but the turbulence it creates must be much bigger. Same with a boat propeller while sailing, if you let it spin when the engine is off it will vibrate more then if you place it in a gear that locks it. I'm sure someone have the correct science on it somewhere on Internet. 

But a paramotor with a clutch have less vibrations on idle, and isn't that worth a lot? I personally thinks that clutch is more dangerous than without. And that there are more positive advantages without one. However the few advantages that clutch have weights heavier.

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I agree with the above and yes I’d prefer a clutch, I was just taking issue with the statement that less drag is created with a spinning propeller. In the case of a power off approach, a spinning prop will create drag where a stationary prop will create less.

 

Trevor.

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Nope. Think of it like this. A flow of water or air will exert a force on a prop, trying to turn it. If the prop is able to move out of the way, by freewheeling, you cannot exert as much force - BECAUSE it is free to spin.

A free spinning prop can have a tendency to vibrate as it is NOT fully under load. It will oscillate between spinning faster to "get out of the way", then slowing a little slower again. Keeping something under load helps prevent vibration. Most boats allow props to free spin as this reduces drag!

If want to try this out for yourself, buy a kiddies windmill, those cheap plastic things. Now see how hard you can feel it when it is free to spin. Then try again, but with your finger stopping it from turning. You will feel the difference. :)

 

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From the boating article above whether a boat propeller should be locked or not...

...Our graphs show the results, which dramatically confirm that wherever possible you should let your fixed three-blade prop spin. The drag when it was locked was nearly three times the drag when spinning...  Conclusion: ‘Let it spin’

 

Edited by xNateX
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