[NSRCA-discussion] More electric newbie questions

[Dave Lockhart]

Colin,

 

I can’t comment on the physics of the electric motor itself…..but….with the RPM sensor on the Eagletree, or the logging of the Castle ICE ESCs, you can clearly see the terminal RPM at the end of a long downline is the same whether using a low idle or high idle.  When the brake is engaged, RPM is not recorded.

 

Dave 

 

From: nsrca-discussion-bounces at lists.nsrca.org [mailto:nsrca-discussion-bounces at lists.nsrca.org] On Behalf Of colin chariandy
Sent: Monday, June 20, 2011 3:59 PM
To: General pattern discussion
Subject: Re: [NSRCA-discussion] More electric newbie questions

 

I'm still trying to get my head around windmilling, low idle and higher idle being almost the same for downline speed.

 

I would have thought (from traditional magnetics theory) that there should be some torque (synchronization) derived from the rotating field and the rotating magnets to resist speeding up. Unless the rotating feild is too weak at low RPM and once out of sync the speed increases with little resistance. Thus the question....is it better to have a higher idle (stronger field)?

 

I am assuming that at low RPM both the PWM and the field voltage are lower than at higher RPM.

 

The problem is that theory and actual test data often don't go hand in hand....and not many clock the speed of their planes.

 

  _____  

From: Dave Lockhart <DaveL322 at comcast.net>
To: General pattern discussion <nsrca-discussion at lists.nsrca.org>
Sent: Mon, June 20, 2011 3:25:11 PM
Subject: Re: [NSRCA-discussion] More electric newbie questions

Ooopsss…..I meant to respond to your 1), 2), and 4) scenarios……

 

I haven’t flown the 3) med brake setting on the Jeti…..but yes, it is possible to have too much brake, and then you will have a faster downline speed than just a windmilling prop.


Dave

 

From: nsrca-discussion-bounces at lists.nsrca.org [mailto:nsrca-discussion-bounces at lists.nsrca.org] On Behalf Of colin chariandy
Sent: Monday, June 20, 2011 3:20 PM
To: General pattern discussion
Subject: Re: [NSRCA-discussion] More electric newbie questions

 

Dave....so you are saying:

 

No brake (regardless of idle or windmilling) - approx the same speed on downlines.

Too much brake - faster than idle/no brake?

 

Colin

 

  _____  

From: Dave Lockhart <DaveL322 at comcast.net>
To: General pattern discussion <nsrca-discussion at lists.nsrca.org>
Sent: Mon, June 20, 2011 1:00:02 PM
Subject: Re: [NSRCA-discussion] More electric newbie questions

Using Castle stuff….

 

1) and 2)     definitely not…..the idle RPM is not governed, and will wind up substantially in downlines, RPM will be the same at the end of the downline whether starting at low idle or high idle.  I’m not aware of any different behavior on other brands of ESCs.

3)  definitely not……wind up in downlines is virtually indistinguishable from using low idle.

 

Depending on just how many braking parameters you can adjust (which does vary between Castle, Jeti, Schulze, YGE), it is possible to have too much brake…..at a point, the downlines will become faster again when the prop disc is spinning too slowly.  I’ve been told that the ideal idle RPM (for maximum braking) can be calculated, but I don’t know anyone that has done this (and I certainly don’t have the knowledge to run the numbers).

 

Regards,

 

Dave

 

From: nsrca-discussion-bounces at lists.nsrca.org [mailto:nsrca-discussion-bounces at lists.nsrca.org] On Behalf Of colin chariandy
Sent: Monday, June 20, 2011 11:44 AM
To: NSRCA Mailing List
Subject: [NSRCA-discussion] More electric newbie questions

 

I can't find any definative reading on this so I have to ask the group.

 

Which configuration provides the most braking on downlines and approach for landing  (Jeti 90 + evo 30-10) :

 

1) Lowest possible idle

2) Windmilling prop

3) Jeti Med brake

4) Slighlty higher idle

 

My testing has not been conclusive....just not enough data.

 

Thanks

Colin.

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.nsrca.org/pipermail/nsrca-discussion/attachments/20110621/96e35b6a/attachment.html>