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Update on Showtime 50 Tests (Model Airplane Accelerometer Tests Peaks at 9.5 G's)

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Update on Showtime 50 Tests (Model Airplane Accelerometer Tests Peaks at 9.5 G's)

Old 06-04-2009, 04:01 AM
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kyleservicetech
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Default Update on Showtime 50 Tests (Model Airplane Accelerometer Tests Peaks at 9.5 G's)

How many of us have ever wondered just how many "G"s our models are pulling during a typical flight, such as a loop?

06-09-09 Update
I ran some tests today on a Hanger 9 Showtime 50, equipped with a Hacker A50-16S, 16X12 APC-E prop, 6S2P A123 pack. The showtime 50 experienced a maximum acceleration of 5 G's on a standard loop where power is cut at the top of the loop before the downward decent and pull out. The model also showed a negative 3.5 G's during the flight, even though no inverted flight was conducted.

The very high G levels experienced by the Hanger 9 Revolver was found on a windy day, with winds on the order of 15-18 MPH. New tests on the same Revolver during winds of 5-10 MPH showed G levels on the order of 5.5 or 6 G's. Guess the bottom line, is if you have a fast model, slow down in gusty winds! (The Hanger 9 Revolver speed was measured at 89 MPH straight and level, and 113 MPH on a steep dive.)

I ran across some information on accelerometer integrated circuits recently, and purchased one of them, part number MMA2201D, manufactured by Freescale. This model accelerometer has a range of plus/minus 40 "G"s. Its available through Mouser Electronics, along with other suppliers. I paid about $5.00 each for several samples.

These devices required a regulated 5 volt DC supply, and use three connections. Two connections go to plus and minus 5 volts DC, the third connection is the devices output signal. The remaining pins on this IC are not used. As designed, the output voltage if this accelerometer IC is exactly 1/2 the 5 volt supply, or 2.5 volts at zero "G"s. The output voltage varies by 0.050 volts (50 millivolts) per "G" acceleration. FYI, 2.5 VDC to 5 VDC output is "Positive G's", and 2.5VDC to zero VDC is "Negative G's". The unit has a very rapid response, and WILL pick up vibration from any of those glow/gas powered models. The rated maximum response is 400 cycles per second, corresponding to a glow engine turning over at 24,000 RPM.

This accelerometer Integrated Circuit was patched into one of my LCD display Amp Hour devices. The PicChip was reprogrammed with 18 pages of code to match the accelerometer. The programming reads the "G" value once per second, and stores it for read back on the LCD display. (It can also record instantaneous "Peak" values, up to 14 G's. This function reads the "G" force about 50 times per second.)

After the unit was built, I put it on a piece of rope, and spun it around for test purposes. After calculating the "G" force at 4 G's, the read back also showed a peak of 4.0 G's

The result? Test flights were made today on my Great Planes "Revolver" electric model. The model was flown through a typical take off, steep turns, and two large diameter loops. The steep turns generated about 3.5 G's, the large diameter loops peaked at 9.5 G's! Also noted were several readings of minus 4.0 G's, even though I never inverted the model.

Note the attached photos that shows a 7.0 G value at 97 seconds into the flight. The inside view shows the accelerometer chip "Standing up". Its supported with a little hot melt glue. It had to be stood up because its position sensitive. The device on the right is a standard 9 volt Alkaline battery with its jacket removed both to save space, and save weight.

Then the model was landed, and the landing gear came off, on what was a rather good landing . That was the end of flying on that model today.

Post landing inspection showed that the Great Planes landing gear was supported by a piece of 1/4 in plywood, about 1 1/4 by three inches in size. And, the CA type glue joints simply came apart, with no damage to the plywood. It's obvious that this landing gear plate was a very poor design, in my opinion.

It would be interesting with those modelers that own the Eagle Tree recording devices, if this unit can be interfaced with those units. It's simple to hook up, with only three wires required, as described above. It would be rather simple to put the chip on a 5 VDC regulator chip, and hook up its output to an oscilloscope. You can watch its output vary all over the place on an an oscilloscope just by swinging it around with your hands. Makes it easy to check vibration levels on those glow/gas models. All you need is an oscilloscope! (I've got three, all Tektronixs.)

Now, that model pulling 9 g's results in the model weighing in at 0ver 60 pounds!
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Last edited by kyleservicetech; 06-10-2009 at 05:59 AM. Reason: New Updates
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Old 06-04-2009, 04:07 AM
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Too cool - I have often wondered how many G's we could pull. I think most RC wings could take well over 10 but now I suspect that is likely very conservative. I would really like know what a sailplane on a heavy winch launch.

It would be cool to see what dive and sharp pull up would do....

Mike
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Old 06-04-2009, 04:25 AM
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rcers

I'll be doing more tests on the "Revolver". Got the Landing Gear pretty much epoxied back in, and need to patch the holes the wheel pants made in the wing and fuse.

As for the sailplane launch, I've flown these models in the 1980's, and some of those winch launches are pretty violent. These launches FAR exceed what any engine/motor powered model could ever do. Guess that's why you occasionally see these sailplane wings come off.

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Old 06-04-2009, 05:21 AM
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I know our Rc Planes pull a lot of Gs, but did not think it was up to 9 Gs, I always build my planes to handle 8Gs with twin Spars, its has worked for me, never snapped a wing yet Take care, Chellie


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Originally Posted by fr4nk1yn
I'm gonna guess your two cent worked.
I did a mad dash and built the entire plane last night.
Built on top of it as the glue was drying, glued in the gear this morning, put the top on and took it to work to sand off the excess before it totally hardened.
Forgot the lead so I taped two pennies to the wing (:

There was some problems so the other plane would NOT have flown as well as it could for long.
The motor is just too much, wing LE was flexing under full power so I held it back to half except for the verticals.
It was all fun and games until the wing spar snapped.

The fix for all the problems should be to drop TWO spars through the fuselage on top of the wing and add another layer of foam, then sand an "airfoil" to it.

Plane is pretty plain it got the tips painted for ID, to bad it bled through the white foam and was no help, and was held together with painters tape.
Glad you got it to fly Frank, Yes 2 spars always build for an 8G wing load Thats what i do, and I never had a wing snap on me yet Take Care and have fun, Chellie



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Old 06-04-2009, 05:30 AM
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kyleservicetech
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Chellie
I know our Rc Planes pull a lot of Gs, but did not think it was up to 9 Gs, I always build my planes to handle 8Gs with twin Spars, its has worked for me, never snapped a wing yet Take care, Chellie


Yeah, and that big loop wasn't particularly violent, just a big loop about 150-200 feet in diameter, with power brought down to 20% or so at the top of the loop.

I did break a wing in the mid 1980's with a sailplane and winch. The 100 inch model had a pair of 1/4 inch diameter music wire spars, after the wing came off, both music wire spars were BENT about 15 degrees. Managed to spin the model down to the ground with the remaining wing, with little more damage. It managed to fly again!
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Old 06-04-2009, 06:09 AM
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Larry3215
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Thats really cool!
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Old 06-04-2009, 05:48 PM
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Any plans of making more and then selling them to us?
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Old 06-04-2009, 06:41 PM
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vax6335

Wow, I did that a year or two ago as the author and builder of the "RCHourmeter" in the RCReport magazine. That took a lot of work, and near as I can tell, I made about 50 cents per hour! And that was sending all the parts to the modeler to build him self.

If anyone is interested, I could design a circuit board for this project, where anyone could buy all the parts. And, I could sell the programmed PicChip at a few dollars over its cost of something like $5.00.

www.ExpressPCB.com will build up three circuit boards, 3.8 by 2.5 inches for $59, sent to your house. If I put multiple accelerometers on a board, that would be enough boards for about 18 accelerometers or so.

Cost, the materials, as a guess, would be about $20 each or so, not counting the circuit board.

If enough readers are interested, I could work up a parts list, and assembly instructions. Do be aware, that soldering this thing up will NOT work with a 40 watt iron! You need a needle point soldering iron for that accelerometer chip.
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Old 06-04-2009, 07:16 PM
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If their is enough interest, I think the best way to go on this would be to approach Eagle Tree, and see if they could interface this into their eLogger V3 unit.

Eagletree all ready has a two axis accelerometer for their more expensive package, but their accelerometer alone is some $70, plus you need to buy the full recorder, which really adds up in price.

Does anyone out there have experience with the eLogger V3???

FYI, these accelerometers have various ranges. The unit I selected has plus/minus 40g, but other varieties have plus/minus 8g's and so on.
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Old 06-04-2009, 09:30 PM
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I'd like to voice my support of this idea as a standalone unit. If you would be willing to order circuit boards and program chips, I would definitely be willing to pay $15-20 for the pair.

I doubt you'll have good luck with EagleTree; they won't want to work with your idea as it would cut into sales of their own 2-axis. The best you could manage would be asking them to consider offering a less expensive single-axis option. To me, that's still not as appealing as a standalone device, because I don't have an EagleTree and don't expect to get one any time soon.
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Old 07-23-2009, 01:29 AM
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I have the V3 Eagle Tree, but the only add on is for altitude. I am using it in a glider and it works great for that. Some of the people have used the GPS add on, but I don't know anyone that has an accelerometer for the Eagle Tree. I didn't even know they made one.

Ed
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Old 07-23-2009, 02:05 AM
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kyleservicetech
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mred
From what I could find out, the Eagle Tree accelerometer is rather expensive. But, if anyone can find out what the inputs to the Eagle Tree system are, it would be good to know.

FYI, the accelerometer I used for my project had an output voltage of between 0 and 5 VDC, with quiescent value at 2.5 Volts DC. And, it had an output of 0.05 Volts DC per "G" of acceleration, eq plus 2 "Gs" would be 0.1 VDC, added to the 2.5 VDC would make its output with 2 g's 2.5 + 0.1 or 2.6 VDC.

Would be nice to find out if the lower cost Eagle Tree system has an input compatible with the 0-5 VDC of these standard accelerometers.
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Old 05-26-2011, 04:15 AM
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Just put that "G" meter into my Giant scale 19 pound Goldburg Extra 330. On a simple loop, that model pulled 8.5 G's. At 19 pounds, that's something like 160 pounds on the wing spar (Minus the wings weight anyhow)

If we could miniaturize ourselves and go for a ride in one of our models, it would not be a very fun ride.
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Old 11-08-2011, 02:25 PM
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I supposed 9 to 10 g is about right - that's what real fighter jets pull doing similar manuevers.

I would think we could do more as there's no pilot to worry about.
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Old 11-08-2011, 06:29 PM
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Originally Posted by prof_fate View Post
I supposed 9 to 10 g is about right - that's what real fighter jets pull doing similar manuevers.

I would think we could do more as there's no pilot to worry about.
Yeah, I'm certain some of our models go far beyond 9 or 10 g's. I didn't want to tear the wings off of that model.

Since then several other of my models have been checked, they also ran 8-10 g's in simple loops. One went over 13 on a snap roll.
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Old 11-28-2011, 03:14 AM
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So does anyone proof their wings before 1st flight?

Even on my simple trainer, unsure of my job epoxying the wing join, I wanted to test it.

Especially after my repairs (have not yet re-maindend it).

5lbs trainer, figure center of lift on each half-wing is halfway out, I supported the wing at the tips and placed 15lbs dead center, I do not think the rest of it would survive 6 Gs, but at least the wing seems it would.

Dave
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Old 11-29-2011, 03:22 AM
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mred
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No, I never proof my wings if I built it. I know they will stay together and if it's an ARF, I normally won't buy it. I started in this hobby in the 50's when we HAD to build our own models or buy them from someone that built it around our area. We just didn't have ARF's then. I like building anyway.

As for pulling 5 to 10 G's in easy maneuvers, that doesn't surprise me either. I have seen some models that I'll bet are pushing 15 at least, maybe more. The way some people fly their planes, I always wonder when they will rip the wings off and some do. As for riding in one of our planes when they are flying, NO THINKS. Not after I have seen the way some people fly. Besides, I couldn't take 10 G turns anymore. They would carry me off on a stretcher after one of those flights and probably to the morgue. If nothing else, I would have a heart attack.

It would seem that the new G-Force meter is now out for the V3/V4 systems and they are either stand alone or used with the V3/V4 systems for logging. I haven't been to the site for awhile, so didn't know about them, but they have G meters now that you can hook in to the systems. The only add-on I have right now is the altitude and digital readout, but I can get the "G" meter for it if I want. Maybe one of these days I will. Until you mentioned it I didn't even know they had brought them out.

Ed
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