SMALLnet post367

Subject: R/C Helium Balloon < http://www.toytx.com/ > I plunked down $85 for this little gem. Quite amazing, I hope. I haven't mastered it yet.

Tech. Support is a riot! They describe it as a pusher, but one look at the props shows it's a tractor. I mentioned this to the guy, and he replied, "I noticed it flies backwards faster than forward." Then he wanted to know how I could tell. I told him to just look at the propeller, and not the direction it rotates in. He didn't get it.

Instructions are confusing. It's made in Taiwan, and I suspect the manual was written by a Taiwanese.

Excellent workmanship. 3 tiny motors, all swinging a 2" prop, from a single AAA cell. Check the Catalog. These motors and props might be just the thing for very small FF, perhaps multi- engined electric P-Nuts. Be the first kid on the street.... Carlo, are you reading this? :D

I have no R/C or infrared TX experience. Any tips? What happens when the receiving "eye" is not visible from the TX?

Here on the Jersey Shore it hasn't been above freezing for a week now. Ground as hard as a rock, and tomorrow we're expecting a Nor'Easter. (Nothing to do with religion.) Expecting 16" of snow, blizzard conditions, and huge tides. Batten down the hatches, boys, she's gonna blow. I've got enough CC for 10 days. (Nothing to do with engine size.) Happy New Year!

2. This tidbit is in regard to the recent conversations on CO2 cartridges for powering various devices. Joe Wagner had me going about these things used in race cars. I remembered I built one of these racers...this goes back to the 'fifties'. I am a pack rat of the worst variety, (ask my wife); digging in that basement revealed I had not lost nor discarded that racer.

It was a Monogram model of an Indy race car. I had painted it black; it still has the plastic "pilot" seated in the cockpit, along with the steering wheel and instrument panel decal. On the right side of the racer is the exhaust system consisting of a four- pipe manifold and long exhaust pipe, which ran almost the full length of the vehicle.

For guidance, it uses a couple of electrical grounding eyelets attached to the bottom of the car. The racer has # 8 decals front & rear. Scraped paint was evidence of mishaps and perhaps a couple of roll-overs. In the bag with the car, I have the device to puncture the CO2 cartridge. That has a steel tapered pin attached to a spring-loaded plunger, which is housed in an aluminum tube. The taper of the pin determines how large a hole would be punched in the cartridge. That is controlled by a knurled end piece which screwed the plunger in or out of the tube.

The plunger also has a notch that would preload the spring device for easier starting. I'm glad I'm a pack rat! In fact, I'm going to buy

Re the question asking about use of the Trinity Slot Machine motors for flying model planes. I had the same question back in about 1992. So here is what I learned;

What you have are motors for R/C cars which are of the Mabuchi RS-540 size, and designed to be used in an event called the "ROAR-91" -- which specifies that: (1) there is to be a single 27- turn winding of 0.65 mm wire on the armature; (2) timing is to be fixed at 24 degrees forward (and cannot be changed); and the motor is meant to use 6 or 7 cells for racing cars.

The intent is that by fixing the timing, wire diameter & turns, no one has an advantage with a special "souped up" motor in this race (i.e. a motor which can turn appreciably faster than the others do).

Gear ratios in the R/C cars are typically about 6:1 (but not easily adapted to R/C airplane use). The rotors of this motor are cut away to make it weigh less and turn a bit faster; thus the name "Slot Machine". When new it sold for about $20.

The obvious first choice is to attach a propeller adapter and fly a plane with the direct drive of a Prop. But what you will find is that this motor size has less torque than the slightly longer Mabuchi RS-550 size motor (of the same diameter) -- such as the Trinity Magnetic Mayhem monster truck motor. That means it can only turn a 6" or 7" Prop, whereas the Magnetic Mayhem can turn 8" Props for more thrust (and get better performance in 300-400 square-inch wing area planes on 6-7 cells).

Therefore, if you go the direct-drive route, use 8 cells (which will not hurt anything) so as to turn 6" props faster for more power. In 1992 I found that on 8 AA pencells of 600 mAh, this motor used 15.7 Amps to turn a Master Airscrew 6x4 at about 15,700 rpm, which is about what a TD 049 does. A flying weight of up to about 32 ounces resulted in a nice flying plane.

Even better is to use reduction gears, so as to turn a larger prop, to fly a 400-500 square-inch wing area plane of up to about 3 pounds. But you can't use a regular gear box such as those sold by Master Airscrew. That is because it would require neutral or reverse timing of the motor (and you cannot change the timing of this motor). Therefore you must use planetary gears or belts for the motors.

Also bear in mind that two motors would give you twice the thrust of one, so why not use both Slot Machines direct drive in a twin motor design model? For example, Model Airplane News plan MAN FSP 05771 is of a 400 square inch Italair Pegasus low wing type that would do nicely, and look nice in the air, too!

That was interesting about using diodes for night flying lights. I've had some luck with small Xmas bulbs (6V) supplied by flat "primary cells" (i.e. non-rechargeable) stripped from old Polaroid packs. Makes a very lightweight system. Used on several .049 jobs.

The flat Polaroid pack fits easily under a wing, or taped inside a fuselage. Have a couple of video tapes showing this feature; but they were a bit disappointing in that my one-lux camera shows the plane very clearly, when we could just barely keep it in the viewfinder during evening flights. At least the navigation lights were bright.

Speaking of Polaroid packs, some of my earliest electric flight attempts used them to juice slot car motors fitted with various plastic, even soldered-on tin can metal props.

I'm curious to learn the opinions of others about the vibration of twin-opposed engines. Most 2-cycles seem to be simultaneous firing, 4-cycles alternate. What about vibration? I felt my Elf twin shook less than an Elf single because the thump of ignition was balanced. Ideas? Roy C.

Does anyone have any experience with NiMH batteries in the smaller sizes? Specifically the 1000 mAh size that is physically the same size and weight as KR600AE cells. My SR Batteries X-250 draws 8.5 Amps static. My Clancy Aviation Yard Bee draws 5 Amps static. Do they maintain voltage at these current draws? Or do I need an extra cell to compensate?

I am planning to get a Clancy Aviation Stagger Bee. I have a PAW TBR .15 R/C in a regular Lazy Bee and I am satisfied with its performance, though the PAW is a crude beast at best. I have heard that MVVS .15 R/C diesel is very good. Does anyone have an MVVS .15 diesel?

...Francis, the PAW design IS a sort of "crude beast" -- but that's one of its virtues, I think. So far the only part of ANY PAW engine I've ever owned that got broken was the spraybar. [JW]

I thought I'd pass along to the gang the demise of my Citabria. I took it out and put on a slightly larger prop (a 5x2), which helped the climb performance. I got a little too exuberant -- did a snap roll to the right. This airplane snapped quite readily, tried to recover; then snapped to the left -- now it's headed down, straightened out and KRUNCH -- the ground rose up and smote my little Citabria. I hit hard enough so that the shaft of the Speed 300 is so bent, the motor won't rotate.

I agree with Randy -- this airplane needed to be lighter to fly better. With a different covering and motor combination, who knows -- maybe Dick Miller's MM1 with a 5 cell pack?

That wasn't the only airplane I lost this weekend. I flew my Bi Winger, and I gave it a full charge in somewhat warmer weather. Nice circling flight, first to the right (I cocked it right on launch) and then to the left -- until interrupted by a tree at about 12 feet up.

Since I fly in a park which is sort of close to an inner city neighborhood, I guess some agile person picked it out of the tree. I hope it made some kid a nice X-mas present.....

I'm also going to pass along a warning. I've been having some troubles with the little 150 mAh NiMH cells sold by John Worth. Here's what's happening. I'm using the cells on a Firecracker motor with a 3.25-inch prop, which is reasonably low draw. The motor ran for about 50 seconds on 4 50 mAh nicads.

Since I needed a little less power, I went to 3 NiMH cells. The first time I charged up the cells and ran the motor, all looked good: decent power for about 2.5-3 minutes. Minor problem is that this is a long motor run for a free flight, except indoors. However, when I charge the batteries up now, I get good power for about 20 seconds, and then a long wind down - over 5 minutes. I'm using a Sirius 100 Charger which is intended for packs of around 100 mAh. It uses a pulsed charge to put in 100 milliamps in an hour for packs between 4 and 8 cells. I talked to the guys who build it, and they said that it could be used for 3 cells as well, but that the trickle mode would put too much in, so you have to pull the cells off when it's done fast charging.

I've been using the charger on a bunch of my small packs, and it does seem to work well -- plus it seems to be well-built.

The problem is I think that this long low-power sequence in the Firecracker with NiMH cells isn't going to be useful for anything. The airplane I had the motor in wouldn't even move on its gear after about 30 seconds. I've also noticed that you pretty much have to drain the cells all the way in order to charge them up. If you don't, one cell tops out first, and then you get reduced voltages from the pack.

It's pretty clear that any airplane that's going to fly on this motor and 3 cells is going to be pretty small and light. I may try the Dumas T-34 or a Guillow 16-inch Focke Wulf. However, for our purposes, the longer motor run that we get from these batteries may not be worth the reduced power compared to nicads. Plus -- how long a motor run do we want anyway? One of the joys of this little electric stuff is not having to fool with timers or any complex electronics. I may try a 4-cell NiMH pack, or I think I'm going back to 3-cell nicads.

Oh yeah, the little switches that John Worth at Cloud 9 is selling for like $1 for 3 or something like that, work well. Smaller and lighter than the Radio Snack stuff, and they work more reliably.

In the previous Posting, there was a question about Speed 280 motors. For the most part these seem to come in two different flavors. There is the Graupner Speed 280 motor, which has a relatively low draw -- I've been running these motors on lithium cells with a 5x2 prop -- though I might go down to a 4.5 x 2.

This is an el cheapo motor, but for many relatively low-power applications, it suffices. The other Speed 280 motor is by Permax, and it's ball bearing. This motor has double the current draw, double the price (not really significant) and considerably more power than the Graupner. I haven't tried one of these yet, but I probably will soon -- need a replacement for the Speed 300, which was annoying: high current draw and lousy construction. (I didn't like the racket of the motor before the shaft got bent.)

I think there may be a third out there by Mega Mig or something, which is kind of in the middle -- somewhat higher current draw than the Graupner Speed 280, but less than the 280 BB. Probably about the same price as the Graupner.

Check out the .049-.074 engine muffler available from Bayou Productions at: < http://www.flyquiet.com/ >.

You've struck a chord in the latest Posting. I was brought up in an environment where we did fly competition, but mostly enjoyed sports flying. Even the big model events in England, like the Northern Heights Gala and the All-Britain Rally (at the Hawker and Handley Page airfields respectively) were mostly a sea of sport flyers with a few contests going on. I find myself somewhat out of synch with my fellow SAM flyers, many of whom insist that model flying was never about fun, but always about competition.

And even Dakota events, which we have been running in Canada with no engine restrictions and no timers allowed, have become shackled in the US by the NFFS with restrictions on the eligible engines (for which there is no justification whatever, and they even exclude many "contemporary motors") -- and allowing timers.

Maybe the AMA can look to a sport-flying event at Muncie like a SMALL Model meet!

...Dave, the AMA did once sponsor a sorta-SMALL model flying event, at Wright-Patterson AFB about a dozen years back. John Worth directed that. I was there (of course), and John told me that more meets of this kind were being scheduled. Yet I never heard anything further on that topic. [JW]

I have an O.S. 25 engine that i want to mount in a Sterling Models Stinson Reliant, about 44 inch wingspan. I need to know what in-cowl mufflers would work with this engine; but I don't know exactly what engine I have here. The engine is probably over 10 years old, and is a ball bearing type with a 2-needle carburetor.

The muffler is a bolt-through type, and its mounting hole centers are 1-3/8" on center. I want an in-cowl muffler that bolts on; I don't like strap-type mufflers. Anybody got any information????

This being my first post, I would like to say that over the last month it has been refreshing to read dedicated model talk.

The Herr J-3 that I'm building has a 35 1/2 inch wing span and is designed for rubber-powered flight. My question is, would the geared motor from a Lite Stick, six 150 mAh batteries, 7-inch prop at an estimated 5 ounce total flying weight be in the ballpark of what would be considered flyable?

Not being into the electric planes for very long, I can say it has been rewarding; as they are challenging; more so it seems, than "wet-powered" planes.

The mention of the Jim Walker "Fireball" brought back some fond memories. My old pal Marshall Hughes and I managed to get a Fireball kit when we were in our early teens living in Balboa, Canal Zone. Together we got it together, and tried to fly it in the baseball diamond, but without too much success...

It was our first Ukie, but a great kit for its day. If my memory serves me correctly, we used an Ohlsson .23 for power.

Years later, living in Portland, Oregon, I had the opportunity several times to see the famous Jim Walker in action; flying multiple ukies at one time, and on another occasion watched him run a radio-controlled lawnmower at a model airplane meet in Salem, Oregon. Jim was a real showman, and contributed a lot to model aviation.

...I well remember my first Fireball kit, too! That had two main problems. One was it's "free flight take-apart" construction. It was ALL held together by rubber bands, some of which (e.g. the tailplane retainers) had to be hooked through eyelets in the stabilizer, onto small dress hooks buried inside the hollow- block-balsa fuselage.

If these rubber bands weren't sufficiently taut (and I, for one, never figured out how to MAKE them taut), the tail would shift readily. That's not good in a control-liner! (Is it ever?)

The other problem I remember vividly was the control lines that came with the kit. Mine was an early one, and it included music wire lines. Gad! Those things were just oversize Slinkies.

I NEVER managed to straighten mine; and a friend who tried straightening HIS by tying one end to a fireplug and the other to the back bumper of his car, ended up with a broken bumper bracket and unaltered, stubbornly-curly music wire. [JW]

Has anyone found a 1/12 scale warbird (plans or kit) that performs well on a plain-bearing .15, like an O.S. .15 FP or LA?

On the Micro-4 electric motor questions, I have found the Foam Flyer from Dave Reese, and the Thistle (Thornburg, I think, in Model Aviation several years ago) on 3 50 mAh cells, does very well. Have had three flyaways with each model (slow learner) in thermals.

They are easy to trim because of the predictable thrust patterns of the Micro-4; and once trimmed, the flight patterns vary only slightly from what you finally decide on. Had one Foam Flyer land in a 50-foot old apple tree and stay there for 2 months and endure many thunderstorms, until the raindrops deluged the joints and it fell apart, coming down in pieces.

I found the pieces, including the motor, buffed up the armature to get rid of the rust, and the darn thing is still runnable.

One way to look at the efficiency of a propeller is that the backwash of the prop should not be too much in excess of the forward velocity of the aircraft. Now, for maximizing static thrust, that means a humongous volume of air moving backward very slowly will give the most efficiency and the highest static thrust.

This means a very large propeller diameter. However, to use the same power to spin a large propeller, one must reduce the rpm, hence gearing. Look at prop sizes on rubber models -- they are huge.

...Don, a rather thorough article on model propellers is included in the SMALLnet web site. That covers in detail the points that you mention, plus a lot more. Prop design and performance is dependent on several inter-related factors, and I've recently come across still ANOTHER variable that affects model prop efficiency.

I hope to do an article on this for one of the model magazines sometime next year. [JW]

Carlo Godel < > responds to Randy's remarks about "variations in wing loading" in the previous Posting:

That is not totally true, Randy. If you predicate the loading of an airplane on the cubic volume of the wing, they all come out very close to being the same loading for the same performance.

As you know, I fly scale from way sub-peanut to jumbo rubber, and a bit of R/C and C/L. So far, all of my Piper Cubs fly at 10 lbs/cubic foot of wing volume -- and that number is very close to the 10.5 that the original full-size J-3 flies -- at and all of my Mustangs seem to like to fly at about 12 lbs / cu ft...

So while surface area is used with the Reynolds number "correction factor", volume loading can be used directly. Besides, if you plot Reynolds numbers vs. wing chord, it comes out to be a cubic curve.

Lazy engineers didn't bother to calculate a volume too hard, back in the thirties. Well yes, they didn't have the hand-held calculators we have today, or the computational speed of computers.

SMALLnet Posting post367