Lumenier RB2205C-12 2400KV SKITZO Ceramic Bearing Motor
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Old Dec 07, 2012, 05:38 PM
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Well - the first twisted shaft I get will be a milestone indeed. Only then will I start to feel "up to speed". The DLE 20 has electronic ignition and I understand that at low RPM the module program retards the ignition (something like 26 or 28 degrees). Aside from that, I can adjust the ignition down to 31 degrees by moving the pickup sensor counter-clockwise along the crank. I may be able to move the sensor more if I modify it but for the next try when my new gears come in, I will just move it to its limit.

Elkton Md? I just finished an internship over the summer that had me living in the Aberdeen area. If all goes well it is my hope that the company will hire be back on full time when I finish school in May.

I was flying at the Swan Harbor field in Havre de grace (awesome field and great bunch of guys there). Cant wait to get back (knock on wood...). I was going to the field in Delaware (Lums pond? maybe 2 or 3 times) but it was much closer to go to HDG...
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Old Dec 07, 2012, 06:20 PM
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What's going to keep the engine cool?

Greg
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Old Dec 07, 2012, 06:54 PM
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For testing initially, it will just be an EDF unit from a little foamy that crashed and I will run it at a low throttle setting...

After that - I will hope the airstream will be enough.

Note: it will be a lot of weeks - maybe months before this project is ready for its own thread on RCG - but here is a little spoiler I suppose... Oh and have fun laughing at my version 1 starter which was a TOTAL failure.
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Old Dec 07, 2012, 09:24 PM
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Small world....I was a member at Swan Harbor,and now I am at Delaware R/C.

Swan Harbor's a bother for me,with the Hatem bridge,and dragging a trailer once in a while.

I like the Swan Harbor field though-that's a grass roots field if ever.........
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Old Dec 08, 2012, 09:31 AM
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That's an interesting hybrid project. How much battery are you carrying?

Greg
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Old Dec 08, 2012, 10:26 AM
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8s 4000 mAh. Takes 35 amps to take off from concrete and 20 amps to cruise but I only have 2 flights on it with the generator installed and not operational. I get about 8-10 minutes of circling around on batteries. It is far from optimal though - I just wanted to make sure the airframe could handle the weight.

This version will not charge the batteries or anything like that, just run the generator at 30 volts in parallel with the batteries (and heavy capacitive filtering of the rectified voltage to keep ripple at ~.5 volts@ 50 amps. Of course if I cant start the freaking motor.... lol.

Down the road I hope to have the batteries and generator on separate circuits with charging capabilities - but as I said before - this project has big technical difficulties (how to smooth ripple while keeping weight down, how to manage throttle on generator, how to not blow up lipos in flight, how to start the motor... just to name a few). I am not an engineer of any sort so its not been easy, and I have been at it for about 4-5 months now and this is the second version.. The first version used a OS 15fp on a belt drive to a BL motor. It could only produce 5-7 amps at 12 volts and was too heavy for any reasonable airframe, so I never attempted to fly it.

Most of the technical challenges I think I have solved (at least on paper) and when (if) it is operational and flying on the generator, I will start a thread somewhere on RCG for it; detailing how it all works. Just gotta get that motor started... I actually never anticipated this would be the biggest challenge, but in fact - it seems to be...so far...
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Old Dec 08, 2012, 11:18 AM
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Throttle you could quite easy fit a governor keeping it at a suitable constant RPM.
The load on the generator will cause a speed droop which will be automatically compensated by the governor. I would say that is actually the easiest part.

Why is the starting so important? I'd say, get a motor with a recoil starter, and start it before flight?

But in that case, I do not really see the advantage of the battery and the parallelling. You could just power the drive motor directly from the generator....

Brgds, Bert
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Old Dec 08, 2012, 12:11 PM
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Now,Bert......some of us just like the challenges of these things..lol.

If he wanted to 'follow', we wouldn't be having this conversation...

My Quadra 35 starts reliably with a standard magneto and on-board starter.
The G'62,at the same timing setting (28 deg advance,no auto retard)simply stalls the starter when it kicks back..

I'm afraid to increase battery amperage or voltage because of the breaking gears...I hope he gets it figured out....it'll make my life easier. hmmmm.
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Old Dec 08, 2012, 12:22 PM
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If you guys are breaking gears you either need better material or wider/course gears. I've been thinking about an onboard starter for smaller engines (glow size) for some time. Just for fun.

Greg
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Old Dec 08, 2012, 12:44 PM
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Originally Posted by epoxyearl View Post
Now,Bert......some of us just like the challenges of these things..lol.
I know what that is all about.... I am very much the same, just to see if it can be done.... but I usually start simple and build up (like first installing water cooling in a helicopter, and later worrying about a circulation pump), because it increases chance for success if you "invent" one thing at a time....

Brgds, Bert
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Old Dec 08, 2012, 12:49 PM
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Bret: I will read up on throttle governors, if it is simpler and more reliable than my current plan then I will consider it. Right now I hope to use a PID controller because it is software controlled and I can tun each of the parameters (how quickly it corrects error, how much error it tolerates and so on...) - but it lacks simplicity and requires some knowledge of programming.


I looked into other motor options with recoil starters (like an RC car motor or something). I decided (perhaps naively) to use the DLE because I already had it, I wanted the option of one day turning the generator off in flight or restarting in the event of motor failure and mostly because I was worried about fitting it in the cramped space my airframe offers.

Earl: You are exactly right - I am enjoying the challenge and everything I have been learning in the process. When/if I figure this out (with all the help from this forum) I will be sure to post/share everything I find on the matter.

Greg: I think going to a course gear is the right choice. I went against my better judgment and changed 3 variables at once for the version 3 starter. I went from aluminum gears on the first reduction stage to hardened steel. I went from a 6:1 reduction on the first stage to a 2.5:1 reduction (increase start RPM) and I went from 64 pitch gears to 32 pitch gears. A lot of changes and terribly unscientific... but what can I say, either I will get lucky and it works or I will be back to the drawing board doing it right like I should have in the first place.

Oh and I changed a 4th variable as well. I am doubling the thickness of my chassis that the starter mounts to... and the aluminum grade from unknown junk to 6061... Very unscientific indeed lol...
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Old Dec 08, 2012, 12:59 PM
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Originally Posted by chemnut842 View Post
Bret: I will read up on throttle governors, if it is simpler and more reliable than my current plan then I will consider it. Right now I hope to use a PID controller because it is software controlled and I can tun each of the parameters (how quickly it corrects error, how much error it tolerates and so on...) - but it lacks simplicity and requires some knowledge of programming.


I looked into other motor options with recoil starters (like an RC car motor or something). I decided (perhaps naively) to use the DLE because I already had it, I wanted the option of one day turning the generator off in flight or restarting in the event of motor failure and mostly because I was worried about fitting it in the cramped space my airframe offers.
A governor is basically a PID controller.... but with the added convenience of having an output signal that a servo can use....
Some RC-type governors give access to proportional band, integrating and derivative time, and others less so, but at least it is a direct plug-in.

You have good reasons for the starter thingy.... it is just that I would try to make one thing work at a time.... no use building a starting system if you can't get the generating system or the governing system get to work properly....

But I really like projects like this.... they are "outside the box" and those are my favourite....

Brgds, Bert
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Old Dec 08, 2012, 01:56 PM
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Woah! they have off the shelf, pre-tuned PIDs? I had no idea. Will definitely read more on this. Looks like another great product from the heli world.
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Old Dec 08, 2012, 02:11 PM
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Woah! they have off the shelf, pre-tuned PIDs? I had no idea. Will definitely read more on this. Looks like another great product from the heli world.
Well.... it is not thßt special.... ANY controller has some form of either P, PI or PID in it... In fact, analog Servo's had some form of PID controller inside.
I truly believe if you could disconnect the Potmeter of a servo and somehow connect a voltage signal proportional to your generatorspeed, and feed the servo from a servotester, you could make some crude form of governor from it. Wouldn't want to go there, but it is very likely possible, because I have done similar stuff with just servo's, servotesters and external signals connected to the potmeters.

An aftermarket cruisecontrol as could be bought in the autoparts stores were basically also some form of PI or PID. But that is most likely not suitable for what you want, because usually there the output signal is designed to operate two solenoids admitting or releasing the engines intake manifold vacuum to an actuator.... All big and crude.... And the parameters are designed for slow responding automobiles, not fast responding 20 cc twostrokes....

Brgds, Bert
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Old Dec 18, 2012, 12:29 PM
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Alright - last night my new thicker aluminum finally came in after waiting for 2 weeks. Within 2 hours I had a new starter chassis that looks exactly like the one in the video in the first post, but with 2X thicker 6061 aluminum (no idea what heat treatment it has if any; I asked the company rep. and he responded with "I am not a metallurgist, i just buy, cut and sell the stuff...).

I am happy to report that this morning my DLE 20 started and ran at a fast idle. (before the shaft coupler came loose and the motor died as i was backing the idle speed down). I will have to write more after work about timing, but I think the sensor was adjusted to the center position.

My recipe:

All gears 32 pitch and hardened or stainless steel.

Motor: scorpion 2221-8 (3595kv) with 9 tooth pinion.

First reduction stage is 9:25 = 2.8:1
Second reduction stage is 9:96 = 10.7:1
Total reduction = 29.6:1

ESC: hobbywing 35 amp
Battery: 15C 1000 mAh 3S lipo - zippy from HK

Chassis: 6061, 1/8 inch thick aluminum (probably no heat treatment). Motor bracket is 1.25 X 1.25 X 1.25 inch 6061 of 1/8 inch thickness ordered from an online store called "the metal store" (paid $18.61 shipping via ups and it took 2 weeks to get from ohio to kansas.... just sayin... but they did custom cut the stock to the size i wanted and I ordered enough for 2 chassis and it was only $27 and some change after shipping... I guess thats pretty good despite the wait).

Operation: ESC on 3 position switch, midpoint is what I used for starting, full throttle is overkill (probably the lipo and/or ESC cant handle it because it sometimes shuts down on this setting). I turned the ignition switch on within maybe half a second of activating the starter - no backfire problems were noticed and the motor came to life.

I do not have video of the motor starting, but here is what it all looks like when operating inside the plane. This is a test with the switch at center position ("half throttle"). You can also see a bunch of other junk in there that will have to be secured before further testing.

Version 3 starter (0 min 11 sec)
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