Jump to content

Motor power


Recommended Posts

I have just been having discussion with Paracell about motor powers. From testing they say they have found that a 90 kg pilot can fly level at 5 kw power. (actual power used and measured). This would mean that the power figures given for our petrol motors are WAY OUT.

I happen to weigh the same as the Paracell pilot.

My engine is 26 hp or 20 kw. So I should be able to stay level at 1/4 power! I can assure you that to stay level takes 5650 rpm and is well OVER half power.

Something is smelling fishy.................

 

 

Link to comment
Share on other sites

Another thought....

Is that 5Kw an actual power rating for level flight, or 5kw output of the motor?  What I mean is if your engine is rated at max 26hp, I assume this won't all get converted to actual thrust.  There must be losses involved.  Sort of like when engine manufacturers claim power at the crank, when power at the wheels is much less due to parasitic losses.

Andy.

Link to comment
Share on other sites

Non of your first points have any bearing on........

An electric paramotor has been measured as using 5 kw at level flight.

Therefore, when I fly my potrol paramotor level, it too will be using 5 kw to keep me level.

I fly level at 5700 rpm with max rpm at 7600. As a rough guide I said assume this is half power. On my machine it as actually a little over half power (but that would make the next sum worse).....

If level is half power, then full power would be 5 x 2 = 10 kw. But my machine says it is 20 kw!!!!!!!!!!

 

 

 

 

 

  • Like 1
Link to comment
Share on other sites

13 minutes ago, AndyB said:

Non of your first points have any bearing on........

An electric paramotor has been measured as using 5 kw at level flight.

Therefore, when I fly my potrol paramotor level, it too will be using 5 kw to keep me level.

I fly level at 5700 rpm with max rpm at 7600. As a rough guide I said assume this is half power. On my machine it as actually a little over half power (but that would make the next sum worse).....

If level is half power, then full power would be 5 x 2 = 10 kw. But my machine says it is 20 kw!!!!!!!!!!

 

 

 

 

 

I wasn't sure whether you mean that it was 5kw of motor power, or 5kw of 'work' to keep level flight including losses.

Unless you are flying the same wing, same frame, same prop etc etc then I assume your losses and efficiencies could be quite different.  For this reason it's probably quite difficult to work out whether your level flight is indeed 5kw.  I guess it could be measured using a dyno if you know the RPM's, you'd still have the air density differences to account for but I would think this is much smaller variation than the rest of the chain of power.

Interesting topic! :)

 

Andy.

Link to comment
Share on other sites

Interesting indeed, a long while back I'm sure I read that you needed a minimum of about 7 HP for level flight. So 7 x 0.746 kW = 5.22 kW.

However I think it was on a slow very 'floaty' wing so actual wing performance and the drag characteristics of the cage and netting, apart from the lines, must all be optimised or taken into account for comparisons.

Link to comment
Share on other sites

Not sure it's as easy to calculate as first thought. G/R is crucial at the chosen wing/brake/trimmer setting.

(Say) 130kg all up weight and realistic trim off hands off glide of 7:1 then you'll need 18.5kg of thrust to stay level. What revs/prop combo will give you 18.5kg of thrust (and therefore hp/kWh)?

Considerable differences expected given which wing & size, size of cage, flying position, prop efficiency, etc.

Richard

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

 Share



  • Upcoming Events

    No upcoming events found
×
×
  • Create New...