RunRyder RC
WATCH
 1 page 749 views POST REPLY
HomeAircraftHelicopterGasser Model RC HelicoptersOther › An idea for alternator-starter combo
10-11-2005 07:09 AM  12 years agoPost 1
Disciple4123

rrKey Veteran

USA

My Posts: All  Forum  Topic

I am building up a Predator gasser camera heli at this time and will be using a Axi 2820 motor on the start shaft for alternator service. This is a bit larger than most motors put in this service, it uses a 5mm shaft, and able to deliver (or generate) around 500 watts. I believe that with this motor, a good ESC attached via relays to the three conductors of the motor could start the engine, then the relays would kick over and restore alternator function. Some of us who just do AP work don't want the extra risk of being near a heli that is starting.

The following considerations would need to be approached:

1) Having two shallow one way bearings in the clutch installed in opposite directions, essentially fixing the start shaft to the clutch with no movement allowed.
2) A power source, probably a 12 cell nicad type battery making 14.4volts would be good to start, and recharge during alternator function.
3) Some relays or a multi pole relay to temporarily bridge in the ESC to the three conductors. This relay could be hooked to a 10 second solid state timer, etc. or switched by servo channel to engage on startup
4) An ESC and open channel to run it. I have never had an electric aircraft, so I know very little about these.

Just trying to gather some opinions from those who may be able to shed some light on this project.

Thanks,
Eric

PM  EMAIL  Attn:RR  Quote
10-11-2005 02:31 PM  12 years agoPost 2
rbort

rrProfessor

Franklin, MA - USA

My Posts: All  Forum  Topic

Can it turn over the gasser engine?
Before you spend any money on everything else needed, I think your first step is to mount the 2820 motor to the top of the Predator start shaft leaving it with the bearing the proper way to turn over the engine and then supplying power to the 2820 motor via some battery (whatever it may take) to see if it can indeed turn over the gasser motor with all its compression. If it can then you are 1/2 way there after which you can design the circuit to start the gas engine and then turn into a charger once the motor runs.

Give that a try and let us know if you can crank over that puppy with a 2820.

-=>Raja.

MA 1005 Hanson 280, 4210 flts
Spectra 27 3DMax, 3288 flts
Whiplash V1-2 Hanson 300, 1570 flts
Whiplash V2 Hanson 300, 402 flts

PM  EMAIL  HOMEPAGE  GALLERY  Attn:RR  Quote
10-11-2005 04:56 PM  12 years agoPost 3
AceBird

rrElite Veteran

Utica, NY USA

My Posts: All  Forum  Topic

You’re kidding right?

If it were only that easy … You could do it with about a 20 : 1 gear ration. You also might want to add a flywheel and a clutch so the motor could get up to speed before the clutch slams in to turn the gasser over.

Now after you have it started you’re going to want to remove all that hardware so you can use it as a generator again.

Now you know why they don’t do this in your automobile.

Ace

PM  EMAIL  GALLERY  Attn:RR  Quote
10-11-2005 05:14 PM  12 years agoPost 4
cyber-flyer

rrApprentice

Boston, MA

My Posts: All  Forum  Topic

It's possible to do with the right mechanical setup. Like AceBird said you need 20:1 or higher gear ratio to crank the engine. Once the engine started the gearing mechanism need to disengage for alternator operation.
Once I tried to crank G231 with Hacker B50-11L motor and 5:1 gear - no luck.

PM  EMAIL  GALLERY  Attn:RR  Quote
10-11-2005 07:13 PM  12 years agoPost 5
TEKHD

rrApprentice

Fresno,Ca USA

My Posts: All  Forum  Topic

Well They have done this in the past with a car 1958 olds if my memory severs me

The Best Place To Be Is In The Air

PM  EMAIL  GALLERY  Attn:RR  Quote
10-11-2005 08:07 PM  12 years agoPost 6
Disciple4123

rrKey Veteran

USA

My Posts: All  Forum  Topic

Thanks for all the opinions. I do not have an ESC. How does one generate the correct powering to a three lead brushless motor to cause it to turn? Does it need some kind of oscillating current to turn, will DC just cause it to twitch over 1/16 of a turn and hold, or will it turn it?

As far as torque and power delivery are concerned: don't electric cars and such start in one gear and run up? I think the motors are able to deliver torque from 0 RPM better than a combustion engine. I also understand that reduction always helps torque,

Thanks,
Eric

PM  EMAIL  Attn:RR  Quote
10-12-2005 02:17 AM  12 years agoPost 7
cyber-flyer

rrApprentice

Boston, MA

My Posts: All  Forum  Topic

You need ESC to deliver pulses with proper timing to different windings of the brushless motor - no way to turn it with DC alone. Also a sine wave is not enough - you need to know position of the rotor and apply pulse at the correct angle of the rotor - sensorless ESC do so by sensing current/voltage combination in the motor windings.

PM  EMAIL  GALLERY  Attn:RR  Quote
WATCH
 1 page 749 views POST REPLY
HomeAircraftHelicopterGasser Model RC HelicoptersOther › An idea for alternator-starter combo
 Print TOPIC  Make Suggestion 

 3  Topic Subscribe

Monday, July 16 - 12:02 pm - Copyright © 2000-2018 RunRyder   EMAILEnable Cookies

Login Here
 New Subscriptions 
 Buddies Online