need help
08-02-2009 | 10:58 AM
#1
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From: Palmyra, NY
need help
I'm taking my first journey into electric flight and I need some help.
I have gotten a small rocket powered glider that I want to make some modifications to.
For reference you can see the model here: [link=http://randrmodelaircraft.com/Gamma%20Star.htm]Gamma Star[/link]
The directions show how to be able to have this as a boost glider or an electric pusher. I want the best of both worlds so I have decided to put an electric motor up front while keeping the rocket motor in the back. This is going to require me to make some modifications to the design but I want to keep it as close to the original as possible.
Due to size limitations I am forced to use a brushless inline motor.
I will also need to run a folding prop.
Where I need the help is in motor / battery selections.
I would like the plane to go around 60-70mph and last 5-8 minutes (time is less important) under electric power.
Here is what I know:
Plane: ~383 grams (includes electronics and rocket motor less battery)
Brushless inrunner: ~ 100 grams
1350mAh 3S battery: ~126 grams
ESC : ~18 grams
Total weight should be around 627 grams or 22 oz.
Due to space constraints I would like to keep the diameter of the motor 24mm or less.
Length is less important.
I'm looking for motor / battery / prop recommendations.
Any help will be greatly appreciated.
I will provide any information I can but my knowledge on electric is next to nothing at this point.
Thanks,
Norm
I have gotten a small rocket powered glider that I want to make some modifications to.
For reference you can see the model here: [link=http://randrmodelaircraft.com/Gamma%20Star.htm]Gamma Star[/link]
The directions show how to be able to have this as a boost glider or an electric pusher. I want the best of both worlds so I have decided to put an electric motor up front while keeping the rocket motor in the back. This is going to require me to make some modifications to the design but I want to keep it as close to the original as possible.
Due to size limitations I am forced to use a brushless inline motor.
I will also need to run a folding prop.
Where I need the help is in motor / battery selections.
I would like the plane to go around 60-70mph and last 5-8 minutes (time is less important) under electric power.
Here is what I know:
Plane: ~383 grams (includes electronics and rocket motor less battery)
Brushless inrunner: ~ 100 grams
1350mAh 3S battery: ~126 grams
ESC : ~18 grams
Total weight should be around 627 grams or 22 oz.
Due to space constraints I would like to keep the diameter of the motor 24mm or less.
Length is less important.
I'm looking for motor / battery / prop recommendations.
Any help will be greatly appreciated.
I will provide any information I can but my knowledge on electric is next to nothing at this point.
Thanks,
Norm
08-02-2009 | 11:08 PM
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From: Cloverdale,
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RE: need help
Hey Norm.
Are you intending on using the rocket first and then using prop power? If thats the case...that sounds awsome and i can help a bit. if not....well....you might want to rethink that idea.
Umm...well i just reread your question. Bad news. A brushless inrunner running 60mph is no big deal but that small and that light...well you mite just kiss that plan good by. If you could mount an EDF jet to it then you could supposidly reach 60mph. You would be able to have more weight because the motor is closer to the CG. I just dont know how you would do that with the current rocket set up. over wing maybe?[sm=confused.gif]
Are you intending on using the rocket first and then using prop power? If thats the case...that sounds awsome and i can help a bit. if not....well....you might want to rethink that idea.
Umm...well i just reread your question. Bad news. A brushless inrunner running 60mph is no big deal but that small and that light...well you mite just kiss that plan good by. If you could mount an EDF jet to it then you could supposidly reach 60mph. You would be able to have more weight because the motor is closer to the CG. I just dont know how you would do that with the current rocket set up. over wing maybe?[sm=confused.gif]
08-03-2009 | 06:55 AM
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RE: need help
tiggerracing,
Thanks for the reply.
In your opinion what is the problem?
I know this setup is going to add nose weight but the inside of the fuse is all but empty which means I should be able to place the battery towards the back to help with this.
I will also have to shorten up the nose to accommodate the motor which will also help the CG.
It might also be possible to go with shorter flight times and use a smaller battery pack.
A motor I was looking at is an HXT 2445 (370L) 2900kv Brushless Inrunner:
Speed: 2900kv
ESC Required: 20A
Voltage Range: 6~12v
No Load Curr: .5A
Max Load: 34A
The problem I have is I have no clue what this will give in ways of performance.
I'm not sure why a 20A ESC is called for when the motor will probably use upwards of 30A.
It is possible to go to a 28mm diameter motor but that means I will have to shorten the nose of the plane that much more (which may not be a bad thing)
Thanks for the reply.
Bad news. A brushless inrunner running 60mph is no big deal but that small and that light...well you mite just kiss that plan good by.
I know this setup is going to add nose weight but the inside of the fuse is all but empty which means I should be able to place the battery towards the back to help with this.
I will also have to shorten up the nose to accommodate the motor which will also help the CG.
It might also be possible to go with shorter flight times and use a smaller battery pack.
A motor I was looking at is an HXT 2445 (370L) 2900kv Brushless Inrunner:
Speed: 2900kv
ESC Required: 20A
Voltage Range: 6~12v
No Load Curr: .5A
Max Load: 34A
The problem I have is I have no clue what this will give in ways of performance.
I'm not sure why a 20A ESC is called for when the motor will probably use upwards of 30A.
It is possible to go to a 28mm diameter motor but that means I will have to shorten the nose of the plane that much more (which may not be a bad thing)
08-03-2009 | 09:39 AM
#4
RE: need help
ORIGINAL: nroofjr
I'm taking my first journey into electric flight and I need some help. ...
I'm taking my first journey into electric flight and I need some help. ...
* Presentation: de-mystifying Electric Flight
http://www.rcaircrafters.org/The%20Electric%20Show.pdf
* http://www.ampaviators.com
-> Beginner Guide
* E-book: Everything You Wanted To Know About Electric Powered Flight
http://homepage.mac.com/kmyersefo/ev...ng-e-power.pdf
Corresponding discussion:
http://www.wattflyer.com/forums/showthread.php?t=31071
* Get/buy a current/Watt-meter, it will save you money! 3$ diy Watt-meter:
http://www.rcgroups.com/forums/showthread.php?t=949923
* http://www.ezonemag.com
-> Faq
Get/buy a current/Watt-meter.
* System wiring diagrams:
http://scriptasylum.com/rc_speed/_wiring.html
* LiPo pack and balancer cable wiring:
http://scriptasylum.com/rc_speed/_lipo.html
* 3$ diy watt-meter
http://www.rcgroups.com/forums/showthread.php?t=949923
* Monthly Ampeer newsletter, on paper and online available. Excellent articles in the archives by e-flight pioneers Ken Meyers and Keith Shaw a.o.
http://homepage.mac.com/kmyersefo
Get/buy a current/Watt-meter.
* Brushless motor animations and simulations. Mostly outrunners but inrunners are just outrunners turned inside out, nothing fancy:
http://www.rcgroups.com/forums/showthread.php?t=216928
Get/buy a current/Watt-meter.
* Choosing a power setup
http://www.rcgroups.com/forums/showthread.php?t=739069
http://www.wattflyer.com/forums/showthread.php?t=27019
Get/buy a current/Watt-meter.
* Current, voltage, Watt, battery-types and -C-rating explained
http://www.rcgroups.com/forums/showthread.php?t=417868
Get/buy a current/Watt-meter.
* 'Dry' testing brushless motors after a mishap:
http://www.wattflyer.com/forums/showthread.php?t=35216
http://www.rcgroups.com/forums/showthread.php?t=240993
Get/buy a current/Watt-meter.
* How to repair a brushless motor
http://www.rcgroups.com/forums/showthread.php?t=1079423
Get/buy a current/Watt-meter.
* Motor_rewinding_101, about poles, winds, delta, star
http://www.gobrushless.com
-> knowledge base
-> basic overview (1-5)
* And last but not least, get/buy a current/Watt-meter.
08-03-2009 | 09:49 AM
#5
RE: need help
Play around a bit with e.g. WebOcalc/PowerCalc
http://www.rcgroups.com/forums/showthread.php?t=606703
and/or www.RCadvisor.com
That will give you some idea.
I would not use EDF, for two reasons:
* EDF is less efficient than a prop.
* with EDF you have little airflow over control surfaces during start and landing. Model more difficult to control, and since you are a newbie ... With a prop you always have the airflow of the propwash.
Vriendelijke groeten
Ron
http://www.rcgroups.com/forums/showthread.php?t=606703
and/or www.RCadvisor.com
That will give you some idea.
I would not use EDF, for two reasons:
* EDF is less efficient than a prop.
* with EDF you have little airflow over control surfaces during start and landing. Model more difficult to control, and since you are a newbie ... With a prop you always have the airflow of the propwash.
Vriendelijke groeten
Ron
08-03-2009 | 10:09 AM
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From: Palmyra, NY
RE: need help
ron_van_sommeren,
Wow that's going to take some time to go through.
Just to clarify I am new to electric, not R/C planes. I have been flying nitro planes and helicopters for approx. 10 years.
I have even flown the gamma star on rocket power only which by the way is very interesting.
0 to 150mph is about 3 seconds.
I just thought it would be fun to take off under electric and fly for a few minutes then kick the plane in the butt with the rocket engine using an onboard ignition system.
I've also thought about getting a current/Watt-meter.
What do you think
I will be looking through the links you provided.
Wow that's going to take some time to go through.
and since you are a newbie ...
I have even flown the gamma star on rocket power only which by the way is very interesting.
0 to 150mph is about 3 seconds.
I just thought it would be fun to take off under electric and fly for a few minutes then kick the plane in the butt with the rocket engine using an onboard ignition system.
I've also thought about getting a current/Watt-meter.
What do you think
I will be looking through the links you provided.
08-03-2009 | 09:43 PM
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From: Cloverdale,
CA
RE: need help
Holly cow thats alot of links ron!
Those links will explain it way better than i can. Ok the fact that you are going to cut alot of weight from the front will help CG. There are a BUNCH of spinners for electric that will even be long enough to make it look like you didnt chop the front off at all. It will look kinda funy sitting on the ground but will look stock in the air. Sorry i cant simplify the whole electric mumbo jumbo thing for you. I would just end up confusing you way more than the links ron provided.
Any thing can work so when you do figure it out LET ME KNOW. Id love to see some pics. People will be wanting your plans!
Good luck and let me know if you need any help on any thing that isnt too technical.
Max =)
Those links will explain it way better than i can. Ok the fact that you are going to cut alot of weight from the front will help CG. There are a BUNCH of spinners for electric that will even be long enough to make it look like you didnt chop the front off at all. It will look kinda funy sitting on the ground but will look stock in the air. Sorry i cant simplify the whole electric mumbo jumbo thing for you. I would just end up confusing you way more than the links ron provided.
Any thing can work so when you do figure it out LET ME KNOW. Id love to see some pics. People will be wanting your plans!
Good luck and let me know if you need any help on any thing that isnt too technical.
Max =)
08-04-2009 | 04:31 PM
#8
RE: need help
ORIGINAL: nroofjr
.... I just thought it would be fun to take off under electric and fly for a few minutes then kick the plane in the butt with the rocket engine using an onboard ignition system. ...
.... I just thought it would be fun to take off under electric and fly for a few minutes then kick the plane in the butt with the rocket engine using an onboard ignition system. ...
http://www.youtube.com/watch?v=glrmMEiG2WA
A current/voltage/Wattmeter is a good investment, it will pay for itself. I have seen too many 'why did my motor/controller/battery die?" threads.
Vriendelijke groeten
Ron
