BMatthews

Getting back to the root of all this I have to wonder if you're not trying to fix a non existant problem in the first place. Yes the 1/2A stuff does not seem to have a very low idle RPM. But from the throttled small stuff I've seen flying the power left at the idle RPM's is still easily low enough to let the models glide in and land in a manner similar to the larger stuff with the lower idle. A lot of that has to do with the small pitch values we fly at. If the pitch speed of the prop is lower than the regular glide speed of the model then it's coming down for sure. Even if the pitch speed is about the same it's still coming down.

At 5000 rpm the pitch speed for a 3 inch pitch is....

5000 x 3 x 60 = inches per hour. That value, IPH / (12 x 5280) = mph. So that's.... 14 mph

Outside of the really light and slow floaty stuff there's not much that flies at only 14 mph.

D Bronk

check the electronic projects@ http://www.cliftech.com/ ;some ideas there..

SGC

Bruce that 14mph is assuming 100% prop efficiency, in real terms at our scale it could be only 55-60%- prop dependent. So at 5,000rpm its definitely coming down, all my throttled 1/2A stuff will drop for touch n goes below about 1/3rd throttle.
So I kinda agree with you that a SLOW idle isnt necessary.
Stewart

Bipe Flyer

I agree, it isn't really needed, but I just had to test out the ESC idea.
Just a bit of quick programming on the radio... Well, the video says it all.

http://www.zippyvideos.com/4224969773324156/escglow/

cyclops2

Your post is easy to read.

Bipe Flyer

Here is the programming mix I used. I set the offset to only cut in at low throttle and then slowly dialed in the mix until it started to glow. The ESC was in the aileron channel, but you'd obviously want to use a spare channel.

cyclops2

You are really asking for it, if you forget what is in there.

KidEpoxy

Bipe- what batts you use, 3.7 LiPo or some 4.8 itty-bitty-batry?

Thanks for the graphic demonstartion of the theory
The guys at the LHS (SF Bay Area) gave me a world of greif when I said to try this back in 2003, who's laughing now.

Bipe Flyer

I used an 8-cell NiMH because my LiPo ESCs are all in planes. I wouldn't use a 4-cell because the lowest cutoff for most ESCs is 5V. I think a 2-cell LiPo would be the best.

I think ESCs make great switches. I've been thinking about using one to control the oil flow in a smoke system rather than a clamp on the tubing.

KidEpoxy

well, there you have it:
The 9.6v dont fry the plug if you ECS it down in power. And them 5-7amp ecs are way light and mostly cheap. Plus you just plug in, no creative linkages & mounts. Also toss in the bennefit of ditching your flight 4.8v RX pack for a lighter 7.4 LiPo.

Bipe Flyer

Yeah, I erased the mix after. That would have been an exciting flight![X(]

meowy84

Thanks so much for all the awesome info guys.

BMathews, you're right of course about the 5000rpm thing and 14mph and that not much will fly at that speed. However, I'm also trying to 'test the limits' so to speak and see if I can get the idle a bit lower, whether it's useable or not. In addition, there was a post relatively recently about a 1/2A car, which I'm also in the planning stages of building. I know that Cox and Jerobee and a few other makers had some 1/2A cars out but they were rather crude. I'm wondering with a heavy flywheel and a throttle sleeve perhaps coupled to a carb (such as the AP) how low/well I can get the little Cox running for use in a 1/2A car.

Then again, as someone mentioned here about themselves, my mind and plans are 100s times faster than my hands and the speed at which any of my projects actually come to life. heh heh

meowy84

Bipe, wow, I like that video. Neat demonstration.

BMatthews

Oh yeah.... I'm extremely familiar with THAT problem.....

I had a Jerobee back when they were new. at that size and with no neat way to duct out the exhaust they were an extremely messy thing that sucked up dirt like a magnet in a machine shop. My buddies and I that had them spent about the same amount of time cleaning and servicing them as we did running them. Frankly I'd go for the electric cars just because of this but I have to admit that the scream of the glow engine compared to the sizzle of the electrics was far more appealing to a nitro junkie....

meowy84

Bruce, I agree, the Jerobees were dirty stinkers. heh heh I imagine it's because the sleeve for throttle control. The larger, modern r/c nitro cars with usual mufflers are relatively clean (not as clean as electric of course but....) Anyways, I plan on using the throttle setup with the hose and the washers as devised by a member (forget the name) on here a little while ago (there was a comprehensive thread on this a little while back). I'm hoping that with a single exhaust exit it'll be a bit cleaner, especially if I fashion a longer exhaust pipe and route the gasses away. Alternatively I could always try my Norvel .061 Litemachines engine with the muffler/throttle setup.

cyclops2

I have a confession to make on this Cox Micro Warbird Spitfire with a new .049 Killer Bee.
I have all the parts fitted in and doing the final balance and Silicone glue in of parts.
I had to push EVERYTHING all the way to the front to not add lead. What a time waster to pull this off.
NO more Cox engines!! I like Norvel RC carb., muffler, beam engine mounts, AND most important, a carb in FRONT. Not buried in the firewall with the fuel line fitting ALSO buried.

Cox had to have idiots to put the fuel barb deep inside the back plate. [sm=thumbdown.gif]
No way to access the fuel line.
Put in a seperate Du Bro Kwik Fill fueling valve. Saved my butt.
Vynyl Glove finger is a balloon tank.

This kept me occupied on retirement

2 more days to toss day. No glides for this plane. CG right on. And a vertical liftoff . Fly or eject.

Cowboy88

Hi Guys,

I have flown many 1/2A's over the years and have used most of the 1/2A engines. Heating is not an issue if you use high (25% - 30%) nitro fuels and are not flying in sub-freezing temps. The reed value engines using only a throttle restrictor (yes, there was throttling mechanism avaliable for the air intake at one time....) did have some issues with heating. But the rotor valves idle well. The big issue is usually some one trying to idle at the same rpm as a large engine. It won't happen! Smaller engines simply run at higher rpms. You don;t need a 500 rpm idle or even a 1,500 rpm idle on a 1/2A engine. If I recall correctly, mine usually idled around 5,000- 6000 RPM and I could land flying gliders like the "Piece-Of-Cake" at that rpm. In my oppion, you are adding wieght and complexity to the system you don't need. Even my Mach Two (twin Mach None) using two Tee Dee's with Carbs did fine without any onboard glow system.

That said, the heating issue does arrise when you start flying in sub-freezing weather. My experience has show that simply keeping the engine idle time short and using as high a nitro as 35-40% wit castor oil will help. I have flown 1/2A's in -20 degree temps and if you keep them under a heating blanket until flight time they start easy, run well, and idle reliably on high nitro fules.

Well, that's my two cents worth.

KidEpoxy

Depending on the model in question, a throttle mechanical linkage to Operational Cowl Flaps might be the ticket to keeping the head hot. Or have some kind of slider door cover the cowl exhaust vents from the engine compartment to reduce fin cooling the engine.

Dunno, really is a model dependant scheme

I was looking at an onboard glow when I came up with the ESC idea, but the idle problem went away after switching to 25% from 15%- Thanx to Jason @ Sheldons

meowy84

Cowboy88, you don't really 'need' leather seats, power windows or air conditioning but they're sure nice to have. Ok, ok, joking aside, not to bug you or anything, but it's not so much an aspect of 'needing' say a 1,500 rpm idle rather than wanting it. As BMatthews mentioned and you reiterated 5000rpm idle is fine for 1/2A but it'd be nice (at least in my opinion) to see if you can get it lower for that extra bit or realism).

KidEpoxy, the cowl thing sounds like a neat idea. It might even be lighter (and probably simpler depending on model) than an actual on-board system.

Cowboy88

I will admit, that I have ran onboard glow on larger multi-engine craft as a safety feature, although it was not needed. I will also admit to, on occassion, doing things just be cause it would be neat to accomplish it... So I do understand the need to expeiment and toy with ideas. As long as it is in that light and not out of a suspected need for the feature I am all for it! ;-)

In that light, one can find a hundred ways to provide onboard glow drivers. As for myself, I prefere to keep them simple using a micro switch. Or, if I wanted to get fancy, I would use a basic stamp microcontroller to allow programmable on/off settings using the throttle as input, and perhaps even a timed feature... and maybe even provide battery monitoring and a audio indicator feature for a low glow & airborn pack. Or perhaps I would use a LM34 to measure the head or exhuast temp and use this to set the glow driver on/off settings via temp and/or throttle or rpm settings.... See, I too can get creative! Just as long as we understand it is a want and not a need, I'm game!

KidEpoxy

hey, good idea.... run a constant hot to a thermocouple on the head, it takes as much juice as it need to stay hot all by its self... that would work better than EGR or 'Pull the Carb Heat'

Cowboy88

Well, I think I would use a IC temp sensor like the LM34 or similar as a thermocouple would require a lot more signal processing and would be fragile. The LM34 and similar ICs could take a beating and keep on ticking and would require only three wires to the chip mounted on the head or exhaust. You would not want to vary the current much as the glow element would do that for you. All you really need to do is turn it on and off. As the ailment heats up it will reduce the amount of current it takes to some extent. If you vary the current you not only ad complexity you also rise the possibility of burning out the plug due to to low a current.

If you run a small current through the plug over a period of time the element will flake and eventually burn in two. The plug needs to have the proper amount of current and voltage sent to it. Other than that, it will do naturally do the rest... Also, you will find that to make a difference you must heat the plug to a point to where it alone is capable of igniting the fuel. Heat is like water... It seeks it's own level. If you have a cylinder temp of 800 degrees and you heat the plug to 600 degrees you then end effect is only a slight increase in engine temp dure to a lesser loss of heat in the glow element. You must heat the glow element to at least the head temp to gain a reasonable amount ot heat in the combustion chamber. So trying to vary the plug temp is of little use. Simply lite it or not. Also, I neglected all sorts of complexities in my post. Fr one, the head temp is far deferent than the temp in the chamber. Exhaust temp would be a better test. Yet, even the exhaust temp will differ from the chamber temp for many-reasons. However, I think I would couple processing of both if I were to attempt this... A little micro controller like the Basic Stamp or a Motorola (yes I know they sold umcs to freescale....) 68705K1 would also do the trick. Programming settings like trip points on the throttle stick, reversal, and temperature trip points could be handled either via a simplistic RS232 connection or simple push buttons.

If you are the techi type and want to pursue this check out Pic micro controllers, Basic stamps, rabbit micro, Freescale micro controllers, Zilog, Intel and I'm sure there are a host of others. The Basic stamps are a good starting point.

National Semiconductor's LM34 is a good starting point for a temp project. All this could be surface mounted and place on piece of real-estate the size of a quarter for a one off version... Production could get you down to about half the size of a dime or smaller...

Ok, enough day dreaming. Stick with a square inch or two if you have not done this sort of thing before.... Also bread board everything first....

Have fun!

Bipe Flyer

Ho-hum - just making a SIMPLE glow driver.

KidEpoxy

kinda demonstrates the ESC "Simply connect battery, plug into RX & wirenut to glowclip" ... many will replace your switch harness as well as your nicads, use the ESC switch & 7.4LiPo pack. Or you can get the bundle of red & green wires... with that freaky single yellow- whats with the yellow? Can't you paint it or something

Cowboy88

Nice square wave Bipe ;-)

I do think that as our aircraft become lighter, larger, and more capable. Having some telemetry and automation on board will become the next big fad. WIreless cameras and some high end telemitry systems are paving the way for what will be common place in large scale remote piloted craft.

I know on my B36 I'm considering many features to remotely monitor onboard systems. Just haven't figured out how to look at the data and fly the plane. Could it be that the future on Large Scale RC will require flight engineer along with the pilot? Or will we evolve with visor mounted HUDs....