Espritmodel.com Telemetry Radio
Reply
Thread Tools
Old May 05, 2014, 07:58 AM
Registered User
hornet_dave's Avatar
USA, IA, Cedar Rapids
Joined May 2003
917 Posts
Awesome news! I think the big takeaway is that the stretch of mono line is giving you much more controllability versus the 300 lb twine (not much stretch) twine that im using.

The other thing thats interesting - at 18 mph linespeed and calm winds, i found the linespeed to be a bit slow with a res plane at the beginning of the launch. Ben has found 54ish to be too fast and 27ish to be a little slow with his planes. These are good data points.

Fnwizard - Yep, everything you say is correct, things in reality would be much worse than 360 amps. The big takeaway is that 100 lbs tension on the direct drive version is likely to blow something up. And 100 lbs tension on the 2:1 geared version seems within reason. Thats the only intended use of my spreadsheet, its just a sanity check.
hornet_dave is offline Find More Posts by hornet_dave
Reply With Quote
Sign up now
to remove ads between posts
Old May 05, 2014, 01:28 PM
RIP MC
fnnwizard's Avatar
United States, CA, Midway City
Joined Dec 2003
3,187 Posts
Quote:
Originally Posted by Benjhla View Post
Thanks for your input Dave and fnnwizard. I am wondering what the most useful thing I could do to help others who are trying a project like this is? I expect if I can post wing area, launch height, wind conditions, maximum amps, duration of launch, line pull, and mah used per launch, then those of you with the big brains can work out some numbers that may help others select ESC and motor sizing.

I am thinking a clamp style amp meter would be useful.

I hope this helps,
Best Wishes,
Ben.
Thanks Ben for all the feedback.
For starters, the data that's most helpful is:
1. Drum diameter for the 2nd prototype.
2. No load rpm with respective current draw and voltage
3. Stall torque with current and voltage.

There a couple ways to get accurate no load rpm, a higher speed (min 120fps) camera (like GoPro 3+) recording the end of the drum. Or, just reel in line for set period of time (few seconds) starting with no line on drum.

You can also figure out the ground line speed while on tow by measuring how much line is wound in as you stop the winch before the dive to go into zoom.

If you use some less stretch braided line on the drum end, you can just mark with markers.

With just 2 and 3 above we can estimate a performance curve to get an idea of where max speed, max efficiency, max torque and max power is.

You can then plot along those curves the data collected when videoing the current and voltage readings while the plane is being winched.

The problem with plane dependent data (including ground line speed) is that it is very setup specific. 2 exact planes can have a wide launch characteristic based on towhook position, camber, ele trim, and throw tension ( assuming same wind/conditions). The only way to narrow this down is to get tension while the plane is on tow.

For that, I ended up building a platform for my winch to sit on as shown in the last link below. I ended up having to use two load cells to get accurate tension due to the "variable twisting force" of the platform from the side load imparted from the line/drum position.

Be careful going down this route though as it gets very time consuming to gather data, then... God forbid, to lose all the data due to drive crash .

http://www.rcgroups.com/forums/showt...0#post15071336

http://www.rcgroups.com/forums/showt...00#post9622858

http://www.rcgroups.com/forums/showt...0#post24657409
fnnwizard is offline Find More Posts by fnnwizard
Last edited by fnnwizard; May 05, 2014 at 01:34 PM.
Reply With Quote
Old May 06, 2014, 05:02 AM
Registered User
Australia, NSW, Armidale
Joined Nov 2012
33 Posts
Thanks very much for your help fnnwizard. I don't have the resources to give you the exact information you want, however I did do some testing today and collected the following information. The flights listed are in order on the following video.

Brushless winch mk2 (1 min 26 sec)


Please note that neither of the planes I tested were pushed very hard. The Orion is a modified glider from a motorised frame, and the Supra is my friends plane on loan. I would guestimate that I was at about 70% of what the winch is capable of.

In addition to that my amp meter is only capable of measuring a total of 100 amps (50 per motor) so i needed to launch conservatively to prevent overloading the meter.

Wind conditions were light ~10kmh

Distance to turnaround 100m ish

Spool diameter 42mm

Flight 1 - Nan Orion 2.4
Battery 42v dropped to 32
Altitude 180m
Amps 56 (total for both motors combined)
mah 96

Flight 2 - Supra
Battery 40V dropped to 32
Altitude 180m
Amps 84 (total for both motors combined)
mah110

Flight 3 - Supra
Battery 40 dropped to 32
Altitude 170
Amps 82 (total for both motors combined)
mah 98

Footage showing winch alone was launching the Supra. Line broke due to wear rather than line tension.

Unloaded winch test at full throttle for 2 seconds
Battery 38V dropped to 37
Amps 12

I am really surprised at the low amp draw of the motors and how little of the battery is consumed per launch. Voltage drop is more than i imagined however I am moving up to 12 cell 65-130C batteries later in the week. Will report how that goes.

I have a new Maxa Pro coming at the end of this week, once I have it built I will be excited to push the winch and see what it is capable of.

Best Wishes,
Ben.
Benjhla is offline Find More Posts by Benjhla
Last edited by Benjhla; May 06, 2014 at 06:28 AM.
Reply With Quote
Old May 06, 2014, 07:10 AM
Registered User
hornet_dave's Avatar
USA, IA, Cedar Rapids
Joined May 2003
917 Posts
Im guessing your line tension is roughly 40 ish lbs, based on my simplistic model, for the 80 amp launches. You batteries are certainly holding you back if you want more power. Make sure you are using at least 5mm bullets on your battery connector. 10 guage wire too.

If you are using less than full throttle into the ESC with that sort of battery voltage sag, i would certainly be worried about ripple voltage. Extra input capacitors (low esr type, do a search on the heli forums for guidance) reduce ripple voltage to tolerable levels.

Of course, if i were using your battery, i would not have destroyed my 2m Renny

I think im going to target about 40-50 lbs tension on my winch, thats plenty for my bubble dancer.
hornet_dave is offline Find More Posts by hornet_dave
Last edited by hornet_dave; May 06, 2014 at 07:46 AM.
Reply With Quote
Old May 06, 2014, 11:45 AM
RIP MC
fnnwizard's Avatar
United States, CA, Midway City
Joined Dec 2003
3,187 Posts
Here's a power conversion chart I just made up for better understanding.
For every 1000W of electrical power, we can convert that to mechanical power of 737.56 foot-pounds per second. That's at 100% efficiency.

The ground line speed equates to how much the winch is reeling in once it gets to the max power point. This incidentally is what we can use to figure out the "sink" speed of the plane on tow as it takes into account the drag of the "air portion" ( the line from turn-around to plane towhook) of the line .

Ben you have almost all the numbers to figure out everything about the winch including efficiency. Since torque is proportional to current (for permanent magnet motors) and inversely proportional to speed, the 2 things you need now is to gather the torque at various wattage and line speed at max power and we can extrapolate that over operating envelope.

Your digital scale would work fine for torque. Just need 3 points for decent accuracy.
And line speed, well... if the line didn't break in the video, I can almost figure out the line speed, yes, it's that simple .

Next time out, I'll get some measurements from a McCann winch (series wound motors do not have proportional speed/torque curve = need actual data points for accuracy) on an Xplorer 4 as I have to rebuild all the data again anyhow. Would make for good comparisons! Thanks again for all your data!!!!
fnnwizard is offline Find More Posts by fnnwizard
Last edited by fnnwizard; May 06, 2014 at 12:40 PM. Reason: Replaced with correct chart
Reply With Quote
Old May 06, 2014, 05:57 PM
If it flies - I want one!
Petem's Avatar
Werribee, Victoria, Australia
Joined Jul 2008
997 Posts
Great experiments!

This is a fascinating thread!
Benjhla, re the mAh used per climb - your numbers seem in the ballpark compared to the energy used to climb my electric soarers to similar altitude: around 100mAh for the 2m floaters around .8kg, around 200mAh for a 3.2m Pulsar at around 1.6kg. I guess winch launching would gain some efficiency from the reduced drag of a pure sailplane, and some energy from any wind acting against the semi-fixed anchor point (eg, with lots of wind you can kite up and use zero mAh).
Watching with much interest - you seem to be headed rapidly towards a very useable, lightweight system.
Cheers,
PeteM
Petem is online now Find More Posts by Petem
Reply With Quote
Old May 06, 2014, 08:46 PM
Registered User
wyong, NSW, Aust
Joined Apr 2005
364 Posts
Hi, I am also watching with great interest as a sport flyer this sound like a much lighter solution to getting a nice launch once the settings are worked removes the worry of giving a mates light plane a launch.

As someone who as driven a winch for full size gliders I can say that you get to a point in the launch (about a 3rd of way up once settled in the climb) that unless you have lots of power opening the throttle made little difference on the heavy gliders (our 351 would reach a limit with the blanik but we could over speed a K7).

Arie
glidesailrc is online now Find More Posts by glidesailrc
Reply With Quote
Old May 07, 2014, 05:54 AM
Registered User
Australia, NSW, Armidale
Joined Nov 2012
33 Posts
Thanks fnnwizard, Pete and Arie for your encouragement and comments.

I think I have a simple test I can do, I am thinking to mount my power meter next to my luggage scales set the camera to film the readouts. With this I will be able to provide, duration, watts, amps, voltage drop and line tension all at the same time logged together, you will also be able to hear the load on the motor and judge how close it is to a stall. This isnt too hard for me to do, and with the equipment I have to hand. I can also measure the amount of line that comes onto the winch up to peak load. The only problem will be keeping the system under 100A which is the limit of my measuring device. The other option would be to attach the watt meter to only one of the ESCs, this will keep everything under 100A but will mean I need to de-solder a bit of stuff.

fnnwizard, if I provided all the data above but for 6 cells (in order to keep the combined amps below 100) is this of any help, or do I need to go the full 12 cells? I could also do measurements for 3,5,6,7,8,10 and 12 cells if that helped.

also fnnwizard, I wanted to thank you for all the help you have provided, and all the work you have done over the years to collect data on winch performance, i think it will help me a lot, even though I dont understand the subject well. Its obviously a lot of work you have put in.

Not sure when I will be able to do the testing, maybe friday... will see...

Best wishes,
Ben.
Benjhla is offline Find More Posts by Benjhla
Reply With Quote
Old May 07, 2014, 03:58 PM
RIP MC
fnnwizard's Avatar
United States, CA, Midway City
Joined Dec 2003
3,187 Posts
[QUOTE=Benjhla;28303258]

fnnwizard, if I provided all the data above but for 6 cells (in order to keep the combined amps below 100) is this of any help, or do I need to go the full 12 cells? I could also do measurements for 3,5,6,7,8,10 and 12 cells if that helped.
QUOTE]
It would probably be best to do the recording with 6-10-12s.
You don't have to go above 50A for each motor @ each set V at all since the relationships will be linear (we can just project the line for current, torque, rpm on the graph.


As you record the launch, we just need a few data points. I'll be looking for voltage, amperage and torque (tension * radius of drum) from ramp-up to the ping. Depending on the response time of all the gauges, this should give us more than enough data points to somewhat accurately plot the linear relations.


My main interest really is in the actual efficiency of the launches between the series wound motors and the brushless systems.


I'll rework the spreadsheet to show numbers and put a graph up to show relationships.
fnnwizard is offline Find More Posts by fnnwizard
Reply With Quote
Old May 12, 2014, 01:11 AM
Registered User
Australia, NSW, Armidale
Joined Nov 2012
33 Posts
"Test" Results

Not the most successful series of tests. I was plagued by a constant stream of obstacles, not the least of which was a line that kept breaking. Still , I did manage to get some results up until the point that the line broke... not sure if they are of any help though.

All tests were on a 6 cell 65-130c 3300mah battery.

There are three tests on the video. Test 1 approached 35kg and what appears to be 88 amps. The second two tests used 30 and 40mah respectively. I didn't get a measurement of mah used for the first test.

Brushless Winch Testing (0 min 37 sec)


Since moving up to 12 cells with 65-130c the winch seems to perform much better and considering I achieved a line pull of 35kg on 6 cells, I think it will do well on 12cells once I get to testing it with a plane.

I am hoping to have my 4m maxa built by the end of the week and will post some results then. I constructed a sliding bearing sled for the winch to sit on, this will allow me to measure tension with a plane on the end as well as amps etc.
Benjhla is offline Find More Posts by Benjhla
Reply With Quote
Old May 12, 2014, 02:26 AM
Thermal Wrangler
DrFragnasty's Avatar
Launceston Tasmania
Joined Mar 2004
2,061 Posts
Any photos of the packs and winch together? Just to give me an understanding of how compact this system could be. The standard winch that Bernie Sizer produces fits in a pretty compact box but doesn't include the battery:

www.nnewinches.com.au

DrFragnasty is offline Find More Posts by DrFragnasty
Last edited by DrFragnasty; May 12, 2014 at 10:11 PM.
Reply With Quote
Old May 12, 2014, 07:48 PM
RIP MC
fnnwizard's Avatar
United States, CA, Midway City
Joined Dec 2003
3,187 Posts
Awesome data Ben.
Here's a chart of your winch power profile. Without the actual amount of line reeled in, it's hard to find efficiency. This is the belt driven winch yeah?
If so, the motor @kv=250 doesn't line up to 2x the expected drum speed so that would suggest efficiency of < 50%?


At 40mAh used * roughly 23v = .92Wh compared to ~ 3.5Wh for the Supra launches. Btw, the Supra launches suggested efficiency only in the 30-40%.


Hopefully sometime this week I can get out to collect data for the series wound motor winches.
fnnwizard is offline Find More Posts by fnnwizard
Reply With Quote
Old May 14, 2014, 05:04 AM
Registered User
Australia, NSW, Armidale
Joined Nov 2012
33 Posts
Hi Chris,
I took some photos today for you to give an idea of the battery placement and scale. If I fly this weekend with Hutton I will try to get a photo of my winch next to his Ober for reference.

Are you thinking of making one? If so I would love to hear your ideas...

Best wishes,
Ben.
Benjhla is offline Find More Posts by Benjhla
Reply With Quote
Old May 14, 2014, 05:33 AM
Registered User
Australia, NSW, Armidale
Joined Nov 2012
33 Posts
Quote:
Originally Posted by fnnwizard View Post
Awesome data Ben.
Here's a chart of your winch power profile. Without the actual amount of line reeled in, it's hard to find efficiency. This is the belt driven winch yeah?
If so, the motor @kv=250 doesn't line up to 2x the expected drum speed so that would suggest efficiency of < 50%?


At 40mAh used * roughly 23v = .92Wh compared to ~ 3.5Wh for the Supra launches. Btw, the Supra launches suggested efficiency only in the 30-40%.


Hopefully sometime this week I can get out to collect data for the series wound motor winches.

Hey fnnwizard thank you so much for preparing the graph, it's very interesting. I am glad the test were of some value. I will collect more data over the next few days and see what happens with a plane on the end rather than a static test. I will make sure to record the amount of line reeled in too. The test was on the belt driven winch, and I also had about two laps of line on the spool, so the effective diameter of the spindle would have been approaching 48-49mm.... sorry I guess you could have used this information before...

Just out of interest I was wondering about the extremes of efficiency. What data would suggest a high efficiency system, say 80%, and what would be very low! Say 10%. I suspect that the more I push the winch, the efficiency will get very low, as I will be approaching a motor stall at peak line tension.

I could imagine using larger motors and a higher reduction system to gain efficiency, however it seems that there is a design compromise where the sound of the decaying and inefficient motor becomes an important feedback mechanism to line tension. Without this I would be a little afraid to put a plane on the end of it.

Does this sound valid to you?
Benjhla is offline Find More Posts by Benjhla
Reply With Quote
Old May 14, 2014, 07:43 AM
Thermal Wrangler
DrFragnasty's Avatar
Launceston Tasmania
Joined Mar 2004
2,061 Posts
Thanks for the photos Ben.
That's a neat set-up. The winch is pretty good too.
I'm not sure if it will compete with existing competition-level systems for pulling power but for a sport winch that looks about right. Better than a bungee for launch height and launch control, much lighter than a standard winch with car battery.

Any idea how much it weighs?
DrFragnasty is offline Find More Posts by DrFragnasty
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Discussion Bixler battery experiment (FPV step 1) raRaRa FPV Talk 10 May 21, 2014 02:27 PM
Idea rigid direct swash rotorhead experiment Alwayscrash Micro Helis 5 Apr 19, 2011 08:36 AM
Video rigid direct swash rotorhead experiment Alwayscrash Electric Heli Talk 0 Apr 10, 2011 04:55 PM
Discussion F3J Winch (with brushless system!) biesas DIY Electronics 21 Jun 16, 2010 08:06 PM
12.5" Span Brushless F-15 Experiment Lost In OC Pusher Prop Jet Models 27 Mar 09, 2005 07:08 PM