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Mini F-16 vintage project consideration

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Old 01-16-2013, 02:41 PM
  #151
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Default RE: Mini F-16 vintage project consideration

That's quite a favor..! I'd like to see how the machine work is done.
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Old 01-23-2013, 10:37 AM
  #152
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Default RE: Mini F-16 vintage project consideration

Okay gang,
I don't have much good news here, but I'm not quite ready to throw in the towel yet. I only got to spend an hour or so with it this weekend, but I fueled it up and got it started. I really couldn't get it to run consistantly. First the extension on the NV seems too long and too heavy. As soon as it fires up it screws in and shuts off the engine. So I put a curved hemostat on it to hold it and got it running for a bit. Now I couldn't adjust the NV like that and couldn't quite even keep it running for more then 20 or so seconds, but in that time It managed only to generate 1/2lb of thrust. Not nearly enough to do anything useful. So I'll try to do something to hold the NV so I can adjust it when it is running (if you have any Ideas please let me know). It wasn't running long enough for me to get a tach on. I am really fustrated that I can't seem to get it running. Some thoughts are:

Fix the NV issue
Raise up the tank to the NV level.

Any other advice would be well appreciated. Once I get it running up to speed and get a RPM and Thrust reading I'll reserve my decision to abandon this or not.

Much TIA.
Rick
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Old 01-23-2013, 10:43 AM
  #153
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Default RE: Mini F-16 vintage project consideration

Here is a closeup of the NV in question. It's a brass tube...
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Old 01-23-2013, 12:44 PM
  #154
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Default RE: Mini F-16 vintage project consideration

Hi Rick:

Really like your notalgic glow fan project. For sure have had a blast buiding the fan with the upgrades.

My ideas for the needle are;

1. Glue a small piece of silicon tubbing, or other material tubbing that withstands nitro, to the housing of fan in the exact position of needle. Hopefully this will give enough friction tohold needle in place.

2. Glue a wheel collar to fan housing to set needle in place. Replace screw of wheel collar so it can be tightened by hand. The same aprouch can be made in wood as your housing.

Hope you can make enough thrust to fly your model glow.

In worst case replace motor with modern EDF and you will have the joy of building a nostalgic fan, and flying a model jet without propeller. Your selected plane looks reallyniceand should be a exellent flier with today edf.

Cheers

Juan

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Old 01-24-2013, 05:51 AM
  #155
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Default RE: Mini F-16 vintage project consideration

One thing is for sure. In all the articles (retro) that I have read there is alot of emphasis on exhaust ducting and inlet ducting. So I have paid alot of attention to this in my test stand. I first got it running without the inlet collar and slipped it on while it was running. There is definatly something going on here. You could feel a pillow of high pressure air as I started to put it into place and then all of a sudden it got sucked on inot place. Interesting...
RP
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Old 01-26-2013, 05:47 AM
  #156
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Default RE: Mini F-16 vintage project consideration

Wow, great to see you got it running.
Your workmanship looks superb.
For a needle to beat the vibration blues, the most successful thing I have found is to use a piece of bicycle cable inner as an extension.


Stefan
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Old 01-26-2013, 06:24 AM
  #157
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Default RE: Mini F-16 vintage project consideration

Bicycle cable? What a great Idea, I might give that a try, Thanks!
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Old 01-26-2013, 09:06 AM
  #158
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Default RE: Mini F-16 vintage project consideration

Do you have fuel tubing covering the needle where it meets the body? That will keep the needle valve from turning. A rubber grommet in the fan housing tight against the brass tube?


Buzz.
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Old 01-26-2013, 10:25 AM
  #159
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Default RE: Mini F-16 vintage project consideration

If nothing else a piece of fuel tubing pushed through the hole in the housing and the needle extension friction fit into that.
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Old 01-28-2013, 04:50 AM
  #160
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Default RE: Mini F-16 vintage project consideration

fuel tubing over the needle will also prevent air leaks and give a more consistant run. do i get the test flight? i have lots of df time......
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Old 01-29-2013, 07:59 AM
  #161
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Default RE: Mini F-16 vintage project consideration

Of course Bob, it might not be much to fly - but I'll let you! I was playing with it last night. I didn't think of the fuel tubing option but maybe that's a easy quick fix I'll try. If not I'll try a flexible extension as metioned previously. I found some stuff in my junk box last night. Maybe I'll try it tonight? It seems nice out...
RP
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Old 01-30-2013, 02:15 PM
  #162
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Default RE: Mini F-16 vintage project consideration

Okay Guys,
Well here is the scoop. I spent some time with it yesterday and I got it running pretty well. I am not sure what RPM I reached, but I pushed it as hard as I could on 25% until it sagged. It seemed I was hovering around the 1lb thrust mark during the run. This isn't really what I was hoping for but it seems like a fair amount of air moving and maybe I can do something with 1lb. I am really disappointed since that is what the .049 was supposed to generate. I have that fan built so I guess I can run that and see what I get, but I suspect it has to be less then what I got on this motor. Maybe I can get a little more out of it with 35% fuel? Anyway ran a full tank through it and it ran well.

http://www.youtube.com/watch?v=UWMK3Nz359k

So what the heck, may as well continue. It's not going to fly very well on that amount of thrust, but might as well continue the journey!! What do you think?
RP
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Old 01-30-2013, 02:16 PM
  #163
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Default RE: Mini F-16 vintage project consideration

Here is the finished motor:

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Old 01-30-2013, 03:15 PM
  #164
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Default RE: Mini F-16 vintage project consideration

These tiny engines suffer greatly from excess friction in the fit of the parts and from too much load at the prop.
Do what you can to reduce both and you will see gains.
I've never worked with an .09....but I'll bet shaving the inside of the piston would pay huge dividends. Same goes for the intake, open it up as far as you can, open up the crankshaft tunnel if you see room for improvement there.
The prop [fan] can probably lose some mass with careful shaving of the blades. You will never know how far you can go until you've gone too far. That said, you must reach a point philosophically where you say to yourself that your results so far aren't satisfactory and that you are willing to go "all in" in an attempt to win this challenge with what looks like some risky engineering on your part.
Tiny engines are hyper-critical about load..the smaller you go the worse it gets. You can't use "off the shelf" components and expect to get more than "off the shelf" results.
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Old 01-30-2013, 07:24 PM
  #165
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Default RE: Mini F-16 vintage project consideration

From the audio that is hovering around 17,000 rpm. Does that seem low for a small fan?

According to Dr. Hepperle's site, the TD .09 makes peak hp around 18,500 - 19,000.
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Old 01-31-2013, 04:58 AM
  #166
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Default RE: Mini F-16 vintage project consideration

1lb translates to about 450g?
I think that would be great for a glow powered .09 fan. What is the weight of the engine and fan together?

It could give you close to 1:1 ratio of thrust and plane weight, and the fan will not stop pulling a higher speeds like a prop does when it reaches pitch speed.
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Old 01-31-2013, 06:32 AM
  #167
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Default RE: Mini F-16 vintage project consideration


Quote:
ORIGINAL: MJD

From the audio that is hovering around 17,000 rpm. Does that seem low for a small fan?

According to Dr. Hepperle's site, the TD .09 makes peak hp around 18,500 - 19,000.
I didn't put a tach to it, but I think I agree with you. It seemed pretty low to me but that was the best I could get out of it. I tested it by pinching the line while it was running and I screwed in the NV untill it would start to sag when I pinched the line. However, it appeared that the NV was incredibly INsensitive to adjustment while running at this speed. It seemes several clicks in or out had little effect.

RP
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Old 01-31-2013, 06:34 AM
  #168
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Default RE: Mini F-16 vintage project consideration

Quote:
ORIGINAL: Mr Cox

1lb translates to about 450g?
I think that would be great for a glow powered .09 fan. What is the weight of the engine and fan together?

It could give you close to 1:1 ratio of thrust and plane weight, and the fan will not stop pulling a higher speeds like a prop does when it reaches pitch speed.
Hello,
Great thought. It should unload a bit once it is flying too - I hadn't considered that...
RP

PS Give me a sec, I'll weigh the fan - that should be telling...
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Old 02-01-2013, 02:34 AM
  #169
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Default RE: Mini F-16 vintage project consideration

Many, many moons ago I tried something similar to what your setup was. I used a converted electric fan. It was made by Morley. I know now that it was a pretty inefficient design but way back then it was pretty cool. I put an Astro cobalt .035 motor in it which sounded neat but before I could build a plane for it I saw that Kress was making Cox .09 conversion kits. So I bought a conversion kit and the engine and had at it. I also bought an Ace 1/2a Pacer, a mini pattern type ship and made modifications to mount the assembly on top, pod style. Kress even sold a plastic pod style shell for it.

But.... I lost interest halfway through the build for a couple reasons. 1) It became obvious it wasn't going to be the rocket ship my mind was envisioning. 2) the noise was horrendous. And 3) problems surfaced that I lost interest trying to tackle for the first two reasons.

I experienced the exact same needle valve problem you experienced. To get it to run I had to hold the needle valve. Everything I tried failed. The friction tubing or grommets everyone is suggesting lasted until about 1 micro sec after the engine started. As soon as a little oil from the exhaust hit it, it would loose all friction and start threading itself out. The setup used the typical kress "fuel tank in an aerodynamic shape behind the engine" approach. Looked neat, but as soon you put fuel in it, it would sag down enough that the fan would eventually hit the housing and spit it off. If you knew how the Morley fan was assembled you would know it not easy to get the fan off. I made a stiffener but to keep it running I had to brace up the fuel tank with a tuned pipe type mount.

I don't recall the dimensions of the Morley fan but the rpms I was getting was way up there. Had to be close to 30,000. It was the most ear piercing, evil screaming shriek you could imagine. In the end, I was using 5% fuel and 3 or 4 copper washers to reduce compression. That was the only way I could keep from blowing glow heads. Having experienced that, I would say you need to reduce your fan load. Maybe try depitching the blades with a heat gun, cut half the blades off (3 instead of 6 blades for example), or maybe try fitting some different newer tech edf fans.

It was interesting project and I hope you are successful. I still have my setup in storage. Its in another state though or I would take pics.

Mike
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Old 02-03-2013, 03:51 PM
  #170
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Default RE: Mini F-16 vintage project consideration


Quote:
ORIGINAL: RickP


Quote:
ORIGINAL: MJD

From the audio that is hovering around 17,000 rpm. Does that seem low for a small fan?

According to Dr. Hepperle's site, the TD .09 makes peak hp around 18,500 - 19,000.
I didn't put a tach to it, but I think I agree with you. It seemed pretty low to me but that was the best I could get out of it. I tested it by pinching the line while it was running and I screwed in the NV untill it would start to sag when I pinched the line. However, it appeared that the NV was incredibly INsensitive to adjustment while running at this speed. It seemes several clicks in or out had little effect.

RP

IIRC, the .049 was supposed to have the blades trimmed narrower to get it into the RPM range it needed to be. Don't be too discouraged by rpm figures or thrust that you are seeing-ducted fans have never been great for static thrust. The setup will generate more thrust once the airflow thru the ducting allows the impeller to not cavitate.
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Old 02-14-2013, 08:00 AM
  #171
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Default RE: Mini F-16 vintage project consideration

Hi Guys,
Well I started some serious work on the fuse. I am having a little trouble figuring how to blend the inlet area. It seems my carved inlet ring is a little farther back then the plans call for. If I shorten the fuse in this area much more it will become very weak in this area. Not quite so sure how to proceed here.

Also, I need to figure out some of RC gear placement. I need to order servos. What servos are you guys liking for 1/2A stuff?

Amazingly it looks like the balance is going to work out quite well. I was really worried with that long tail pipe I wouldn't be able to get enough weight up front, but it's looking like that shouldn't be a problem. The motor turns out to be quite heavy, I haven't weighed it yet, but I'll get on that soon, promise..

RickP
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Old 02-14-2013, 08:54 AM
  #172
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Default RE: Mini F-16 vintage project consideration

CP turned me onto HS-65's a while ago and I really like them for faster 1/2A stuff.

The instructions say the TD .09 is 2.72oz.
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Old 02-14-2013, 09:06 AM
  #173
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Default RE: Mini F-16 vintage project consideration

Ok Thanks,
That sounds reasonable to me. Oh, and I mean the weight of my entire fan unit, sorry! The spinner is quite heavy. It's a bit of penalty, but I'm not sure how to get around it.
RP
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Old 02-14-2013, 09:15 AM
  #174
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Default RE: Mini F-16 vintage project consideration

Now the question I have is can I get away with one servo for the ailerons, I know standard convention is to put two, but anything I can do to minimize would be helpful.
RP
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Old 02-16-2013, 07:19 AM
  #175
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Default RE: Mini F-16 vintage project consideration

Quote:
ORIGINAL: RickP Now the question I have is can I get away with one servo for the ailerons, I know standard convention is to put two, but anything I can do to minimize would be helpful. RP
Nowadays it is common to put 2 slightly smaller servos. Previously it was common to use one servo, a larger one with sufficient power. If strip ailerons, servo was mounted in the middle of the wing with pushrods to the edge of the aileron closest to the wing. Ailerons had to be sufficiently strong and rigid enough to minimize torsional twisting toward the outside. The other way was to run flex pushrods through the wing to a location in the middle of the aileron. Another was horizontal pushrods to an "L" shaped bellcrank, which in turn had a pushrod going vertical to the aileron.

Look at any of the older aileron plane plans that show how it was done.
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