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03-02-2012 09:22 AM  9 years ago
Topic Vote0Post 1
Dimitris76

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Carmel, IN

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How many RPMs?
No that I got your attention

How fast do we need to crank those Zenoahs during starting?

Assuming an engine with good compression, fresh fuel, right oil ratio, non-flooded cylinder and well adjusted carburetor...

There reason I am asking is because I am building my own DIY onboard starter. I can see that commercial FEMA starters are using Speed 480 motors with an approx. reduction ratio of 36:1, but I need to do my own calculations.

Thanks!
Dimitris
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03-02-2012 09:24 AM  9 years ago
Azalin

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Yes you got my attention. Subscribed.
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03-02-2012 11:06 AM  9 years ago
Toxic Al

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chuluota, Fl

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Vario had one, not sure what the set up was but I am sure some who has one might chime in.Peace, Al
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03-02-2012 12:27 PM  9 years ago
Dimitris76

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Carmel, IN

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I believe Vario's are just rebranded FEMA starters for the
RC-series of Zenoah and clones.

The concept is pretty simple. I just don't like the idea of a starter motor hanging between the undercarriage.

I am looking into a finer solution for my gasser.

Dimitris
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03-02-2012 12:59 PM  9 years ago
Pistol Pete

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Seffner, FL

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I dont recall where I read it but my memory banks are kicking back the number 300rpm.~~Enjoying the hobby one flight at a time~~
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03-02-2012 06:10 PM  9 years ago
rbort

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Franklin, MA - USA

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300 sounds low?
The motor idles in a heli at about 3800 rpms. In an airplane it can run as slow as 1800 with a prop.

300 is like 5 revs a second you may need a little more than that to generate a good spark?

Free wheeling hand held electric starts generate at least 2500 rpms. Geared ones are slower. I guess the threshold is how fast you need to be to make enough spark to fire.

-=>Raja.
MA 1005 Hanson 27 3DMax, 4488 flts
Spectra-G Hanson 27 3DMax, 3485 flts
Whiplash V1-2 Hanson 300, 2090 flts
Whiplash V2 Hanson 300, 989 flts
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03-02-2012 06:37 PM  9 years ago
Azalin

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Pull the starter knob slowly and count the engine turns. Assume 1 pull takes 1 second. So multiply it with 60 and you will get the RPM.
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03-02-2012 08:27 PM  9 years ago
Dimitris76

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I believe I hear 4 or 5 pop sounds in every pull of the starter rope... So 300rpm sounds about right.

Dimitris
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03-02-2012 11:15 PM  9 years ago
Gearhead

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I'm betting 1 Pull takes less than 1 SecondJim
Buzz Buzz Buzz
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03-03-2012 04:12 PM  9 years ago
Azalin

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You might be right. 1 pull takes about half a second. More or less.
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03-03-2012 04:49 PM  9 years ago
Eroto

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Yes, you got my attention too
I like DIY
fly adrenalin. if it AINT broken DON'T fix.
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03-04-2012 05:47 AM  9 years ago
Eleven_Bravo

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Yes this seems very interesting to me also you have my attention.

On my HPI baja 5T if it is properly primed I pull one pull with the choke on to get a pop the one pull with it off then its running.

When the engine is warm all I have to do is give it one half hearted pull and it is running. It starts easy.

I just counted four revs per pull x 60 is 240 RPM

480 if you count a pull at a half second.

It is JMHO if you can get 3 to 600 rpm you will be golden.
ENGAGE!!
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03-04-2012 06:04 AM  9 years ago
rbort

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Franklin, MA - USA

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I wanna say
I'm not so sure about this logic...

If you pull the starter through and it goes around 4 times, don't you think the motor actually accerates as you're pulling and slows down to a stop after the rope has reached its limit?

I mean its not as simple as how many revs by a second?

-=>Raja.
MA 1005 Hanson 27 3DMax, 4488 flts
Spectra-G Hanson 27 3DMax, 3485 flts
Whiplash V1-2 Hanson 300, 2090 flts
Whiplash V2 Hanson 300, 989 flts
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03-04-2012 06:30 AM  9 years ago
Gearhead

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Edited,,
oopps,, never mind LOL
Jim
Buzz Buzz Buzz
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03-04-2012 06:59 AM  9 years ago
Azalin

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I got it. While you pull the starter someone looks to GV-1 to read the highest RPM it displays.
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03-04-2012 07:05 AM  9 years ago
Gearhead

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^^^ first remove the S-Plug CapJim
Buzz Buzz Buzz
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03-04-2012 08:11 AM  9 years ago
Eleven_Bravo

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Salisbury,NC

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4 pops per pull x 60 seconds would = 240 rpm if you are counting each pull as one second

If you count each pull as a half second then you are getting 8 pops per 1 sec pull x 60 seconds = 480 rpm I dont know where you came up with 28,800.

Or am I missing something??

Yes you are correct you do have acceleration and deceleration when pulling the cord but I am far from smart enough to figure all that out mathmatically to give you a correct answer on rpm.

Obviously neither of you agree with my thought process so I must be wrong so I will just bow out of this conversation and let the smart people have the floor. I am just a forklift operatorby trade and not a designer obviously.
ENGAGE!!
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03-04-2012 08:23 AM  9 years ago
Azalin

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Edited,,

""480 if you count a pull at a half second""

480x 60 Seconds = 28,800 RPMs should do it

it's not how many times the Plug Sparks that starts the Engine, it's how fast the Engine turns that Starts the Engine, you can turn the Engine over very slow at 50 RPMs all day long and most likely it will never start, but spin it at 28,800 for 2 or 3 Revolutions and it will start
You must be very sleepy when you write this.
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03-04-2012 12:47 PM  9 years ago
fastflyer20

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N. Tonawanda, NY

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Anyone ever start a nitro or gas plank on one flip of the prop?

A engine theoretically only needs one turn to start. The extra turns are required to suck in a proper air/fuel charge or due to improper needle settings/worn engine. I would bet 300 would start it with no issue as long as it had enough torque to crank it over.
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03-04-2012 01:25 PM  9 years ago
Rototerrier

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Fayetteville, GA - USA

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Anyone ever start a nitro or gas plank on one flip of the prop?
Me me me!! G45 on an Extra 300.

Choke and Prime Prime Prime and one good big flip and away she goes. Definitely not even close to 300 rpm. My guess...maybe 120-200. You do flip pretty hard...but could only guess as to what that would relate to in RPM if you could keep a consistent movement like that.
Gassers Rule, Nitros Drool, Electrics...uhhh...Joule?
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