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So many Micro Systems to choose from...

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So many Micro Systems to choose from...

Old 07-10-2004, 03:08 AM
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Mike Taylor
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Default So many Micro Systems to choose from...

The question has come up about the different really micro R/C system out there and what makes one better than another. Here are some general pros and cons of the ones that I have played with.

The RFFS was the first sub-2 gram, 3-channel, proportional, plug-n-play micro R/C system. It has a built-in ESC and the directional controls drive magnetic actuators. The actuators are magnet and coil and weigh up to 2 grams and as litlle as a 1/10 gram. A single LiPoly cell powers it. It is wide band and can suffer interference in a crowded environment. I have quite few of them and I love them. If you are so inclined, you can remove the plug-n-play option and remove the pins and hard wire the system. In this dieted form with a light-weight antenna, the radio weighs 1.5 grams, and a couple of stock 1-gram actuators gives a total weight of 3 1/2 grams. Some very small airplanes (like less than 6" WS) are being flown with this gear. In stock form and with the largest actuators, the weight is still only 6 grams. The battery is connected directly and no switch is required. The RFFS with the 'big' BSD actuators is shown in the last photo.

The Micro Joule from Cirrus is a narrow band servo based system with remarkably light weight - some where in the neighborhood of 1/4 ounce. It is also plug-n-play. It had serious problem to begin with, but Cirrus corrected all the deficiencies and enhanced the strong points with even better performance. You can get ESCs for either a single LiPoly or one form up to 3 cells.

The external ESC produces a 3.3 volt output the servos which provides plenty of torque without chatter or over-shoot. You really should add a switch to turn these one; plugging produces chatter which can confused various processors. The ESCs are rated at more than adequate amperage for moderately sized planes. Down side is the larger connectors supplied, which are suitable for plugging into IPS or LPS systems, are a major part of its weight.

The MJ servos are 1/4" square sticks and are easy to mount. Heres one that is being fitted in a 2 ounce stick and tissue Albatross. This worked out well; the servo is strong, smooth, and centers well without jittering. Very acceptable. Down side - cost is rather high, and the output arms are fixed in place; mounting must accomodate this or you need to detact and reattach the arms with glue (older ones) or solder.

The second photo shows Falcon servos. These weigh less (1.7 grams per servo). These use the same pager motor as the MJs and have comparable torque, speed and resolution. The are shorter but wider. The interesting thing about these (beyond being extremely light) is the utterly simple mechanical system, and removal of the mechanical pot virtually every other servos use. A 'Hall sensor and a tiny magnet mounted on the output arm make sensing postion a solid state affair and not subject to vibration or wear. There are only 3 moving parts to the servos. Down side - same price as the MJs, you have to swap the red and black leads if you use them with the MJ RX as shown, and they have no real case so care in handling them is prudent. Updates to the design from a responsive manufaturer has added mounting hole and a third output arm for easier geometry in some cases.

I don't have pix of the next two RXs handy, so follow the links...

The JMP RXs are narrow band, and come in either actuator or servo versions. They weigh slightly less then the MJ, but not enough to matter any. They can be had with or without the mini-jst connetors if you are shaving grams. The JMP has a built in ESC and is designed to run on a single LiPoly. An add-on board allows running on two cells for more motor power. They are about 2/3 the length of the RFFS. These RXs, as well as the Falcon servos, are sold in the U.S. by Bob Selman (http://www.bsdmicrorc.com/). If you happen to fly channel 33, or have a spectra module, JMP also offer sub-gram RXs... The servo versions plug right into the Falcon servos, but the MJ's leads would have to be reversed here. This system claims to and indeed, appears self tuning a shortened antenna.

The Penta is a 5-channel, narrow band RX designed by Stefan Gasparin or CO2 fame (http://gasparin.cz/?show=main&lng=en follow the links to products and then micro systems). These are about 2 grams and are smaller than a postage stamp, flat and easy to find a spot for inside a small peanut sized model. They need an ESC, and a number are suitable near a gram. If your want full house with flaps for ~10 grams, this is the way to go. The down side to these is that you are expected to hardwire them for minimum weight or add plugs for the mini-jst's. This sytem is available in the U.S. from Dave Lewis (http://www.homefly.com/). Dave is also a supplier for execellent light weight coverings and extremely light weight CF tubes. One of my Pentas is going into a full-house, stick and tissue, twin-motor Tigercat scale model with either flaps or LG (can't decide). These are very reasonably priced pieces of jewelry, but the down side is the external ESC required, although this lets size the ESC to the model's need.
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Old 07-10-2004, 10:24 AM
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Tommygun
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Default RE: So many Micro Systems to choose from...

This is an excellent rundown of the various systems Mike. Is there anyway to make a post "sticky" here? (So that it stays at the top) So if a beginner in micro R/C wants to get one of these systems, I'm assuming you'd recommend the Cirrus? That one seems to require the least amount of tinkering to make work correctly. I know you talked a little about amp draw with the Cirrus ESC, but what size motors does that translate into, and where can you buy them? Can we see some more examples of planes you've built and flown with the Cirrus system? Thanks!
Old 07-10-2004, 02:07 PM
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Mike Taylor
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Default RE: So many Micro Systems to choose from...

Tommy,

Yes I recommend the Cirrus MJ, JMP, Penta and RFFS systems; they are all quite good, each with its own special strengths and weaknesses. Whether a system has an ESC can be either a strength or weakness. A weakness because you need to add another device (and a gram or two), but it is a strength since you are free to select larger, smaller, or higher frequency ESCs... All three servo systems use basically the same RF friont end and the same performance.

One important note: the Falcon servos are wired to the micro standard adopted by 'Sky Hooks and Rigging' and the JMPs, and the Cirrus MJs are wired to the standard U.S. parkflyer standards. To mix Falcon and MJ gear, two servo plug wires will have to be reversed!

For simplicity, the MJ system is the one. It has all the parts you need, ready to plug in and fly, and the problems that we saw in the early preproduction and first production runs have been corrected. The 5 amp ESC plugs are standard 'park flyer' stuff, and if you use a park flyer pack and motor, you're ready to go. I use smaller motors and batteries and replace the plugs with lighter ones. I worry that the MJ servos' output arms or long gear train will be damaged, but so far they have been fine. The whole system is quite light and works well. A 3 servo system with ESC weighs about 11 or 12 grams.

I admire the very light weight and simplicity of the Falcon servos, and I am willing to swap the two pins to use them with the MJ RX or in stock form with the JMP. Used with the JMP RX, you get a lighter system then the MJ (no ESC), but the higher cost is offset by not needing to buy a ESC. A full-house 3-channel system w/Falcons weighs under 8 grams. When you are contemplating a peanut sized model, that 3 grams can mean a lot - like 10% of your target weight!

The Penta works with either servos, and it is the ony 2 gram 5 channel radio available. It does take some 'fiddling', and it requires an external ESC

I still love my RFFS sytems; they are the lightest. Here's a link to a BIG movie of a small plane. I gave my friend Chuck a $10 Estes' 'Spicy Wings' free flight model. He came back with the plane shown in the real time movie here: http://www.vcnet.com/mtaylor/Spicy%2...Over%20TO.rmvb
He does loops, rolls, and inverted passes on a day that so windy it drove all the Tiger Moths out of the sky. It has an RFFS and two actuators, kenway geared M-20 or N-20 (I forget which now). This was a year ago, and a lot of new developments have hit the market since then...

The first photo is of a DPCModel's (http://www.dpcmodels.homestead.com/) Albatross converted to full-house R/C with Cirrus MJ RX and ESC, 2 x 170 LiPolys and a mix of Falcon and MJ servos. Hatch and top wing and struts are retained with magnets for easy gear access. AUW 2 1/4 ounces, flight is 'scale-like' (slow).

Next photo is a 'Fast Freddy' pull-out plan from Fly RC mag. The plan is supposed to be blown up to 200%, but I built mine to the plan - hence the 'Half-Fast Freddy' (you work out the pronunciation ). 3-channels, 11 1/2" WS, AUW ~ 1 ounce - vertical, loops, rolls, etc.

The last photo is a plane originally based on the Benny Howard "Pete" Racer. It has evolved into a fully symmetrical built up wing with laminated bent wood surface outlines, 1 mm Depron fuselage. This is currently carrying a modified (to accept two cells) RFFS, 2 x 145 LiPolys, 2 BSD actuators and N-20 motor. It is lightly loaded and the 14% airfoil allows it to pivot on a wing tip without tip stalling
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Old 07-11-2004, 01:54 PM
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Tommygun
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Default RE: So many Micro Systems to choose from...

How do you mount the MJ servos? They don't have a mounting flange like a traditional servo does. That Motorcalc program recommended for my application that I use an Astroflight 010, which is brushless. Since brushless motors require a specialized ESC that probably comes with the standard JR/Hitec plug, how can I make it work with the JMP connector receiver of the MJ system? The MJ receiver just has a standard BEC circuit that will work with any ESC, right?
Old 07-11-2004, 06:31 PM
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Mike Taylor
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Default RE: So many Micro Systems to choose from...

Mounting the servos is easy - servo tape works fine. The one in the top wing of the Albatross is glued in with a touch of flexible glue (RC-56) - it is just buried between two spars.

As fara as running the 010, it is brushless and requires a high frequency ESC. Although they call the MJ ESC 'high frequency', it is not high enough for the AF. The only difference in the ESC from a standard one is that it puts out 3.3 volts and the standard ones pump out 5 volts. At the higher voltage, the servos do start to jitter (over-shoot). Get a couple of share mini-JST plugs to solder up to the ESC you pick...

To be quite honest, I think you might want to rethink this application. If you need an Astro Flight 010, why not just use small conventional gear? The 5 gram servos are 2/5 the cost of a MJ servo, and it shouldn't effect the AUW that much. The weight of the motor and battery far outweighs the R/C gear. I tend to save the small gear for small planes...
Old 07-12-2004, 08:37 PM
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Default RE: So many Micro Systems to choose from...

Mike, maybe you have a couple tips on this application. This is an old U control "Super Stinker" made by my uncle back in the 60's. It's pretty much solid balsa. I don't think it's ever been flown, but it was originally designed for an .049. I picked it up from my parent's house today to check all the weights, and it weighs about 2 ounces w/no gear, and about 4 ounces w/ FMA min servos, GWS reciever and ESC. Wingspan is 13.5", area is somewhere in the neighborhood of 76 Sq". I plugged the data into Motorcalc, and it recommends a GWS CN12-R-LC 2:1 ratio (whatever motor that is) and 2 cell LiPo 700MAH. Apparently, the program thinks it will fly! Anything else I should consider?
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Old 07-12-2004, 10:25 PM
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Mike Taylor
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Default RE: So many Micro Systems to choose from...

Did I mention my current project is a Pitts Special 'Little Stinker', also in peanut size (13" WS).

I'd bet yours is the old Sterling kit... I had one as a kid with a Cox Baby-Bee .049 in it, and it was stink fast.

Mine new one will be a little lighter - I'm on track for near a 1 ounce AUW, probably more, but close to the ounce. Of course, the plans I am working from are for a Rubber band FF model designed in the 70s. Mine will come in near 2 0z/foot and should have a good chance of flying. If I need more poop, I can move up from the M-20 motor to the N-20 for a 4 gram penalty.

Yours at 4 oz, or 8 oz/ft, will be very, very fast. I've stopped saying that weight loading won't work, since several people have reported small planes flying at that weight, but it is way too fast for me to stay up with... The flight calculator suggests a minimum airspeed of ~8 mph for mine. Yours however, will have a minimum airspeed of 15 mph and in 4 seconds, it will be 90' away. Launches or take-offs will be thrilling!
Old 07-19-2004, 08:46 PM
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Default RE: So many Micro Systems to choose from...

Nope, that one is the old Scientific kit! I have one built on the shelf (red/white, with Betty at the sticks), and a kit NIB also.

I feel as is it may be a bit heavy as is, but then, you never know until you try. Honestly, I would preserve that old plane, and scratch build another one like it, using contest balsa, and try to convert that as you build it. It would be a shame to bust up your Uncle's plane. I'll bet it'll be a bit fast too, weighing 4 ounces with 76 sq in of wing.

Aren't they cool, though!!!????

Hey Mike, your project wouldn't happen to be a David Jones conversion, would it? That one is by far the prettiest Peanut Pitts ever drawn! I keep telling myself to build it for the new Micro Joule, but can't bring myself to try, for fear of not making it as pretty as it deserves to be...

phil in austin
Old 07-19-2004, 10:04 PM
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Default RE: So many Micro Systems to choose from...

Oops! Scientific - that's what I meant. Senior moment...

Yes, I am working from the Hannan Graphics plan drawn by David Jones. It is a very nice set of drawings, and surprisingly easy to build from. There are some issues with the ribs in that you need to cut away the lines instead of cutting to the lines, but it builds nice and square...

I built one in '71 0r '72 as an indoor FF. It worked very well, although I don't think I got much more than 30 seconds with it. The new one should have better duration when it is (re) finished - it got put up and out of the way on its building board, but then got knocked off the top of the fridge and it landed under the board. I can salvage the fuselage but it now needs new wings. The new micro gear (MJ, Falcon, JMP, etc.) is absolutely made for this sort of craziness
Old 07-23-2004, 03:45 PM
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Default RE: So many Micro Systems to choose from...

ORIGINAL: phuffstatler

Nope, that one is the old Scientific kit! I have one built on the shelf (red/white, with Betty at the sticks), and a kit NIB also.
I feel as is it may be a bit heavy as is, but then, you never know until you try. Honestly, I would preserve that old plane, and scratch build another one like it, using contest balsa, and try to convert that as you build it. It would be a shame to bust up your Uncle's plane. I'll bet it'll be a bit fast too, weighing 4 ounces with 76 sq in of wing.
phil in austin
You have a good point. Theres not much too it; it would probably be easier to just build something else similar from scratch. That being said, has anyone ever made a solid balsa micro plane?
Old 07-23-2004, 06:07 PM
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Default RE: So many Micro Systems to choose from...

TommyGun,

There are lots of 'solid balsa' micros, just not that thick! Look at Ralph Bradley's thread on the MicroMite over at RCGroups. It has been scaled down a couple of times, first down to 7 3/4" WS, and it is now down to 5 1/2 WS. See the thread at http://www.rcgroups.com/forums/showthread.php?t=242994

Other planes like the 'Skeeter' from DWE (smallrc.com) are also all balsa.

Matt Keenon's 4" WS 2 1/2 gram SE-5 is also balsa (http://www.rcgroups.com/forums/showthread.php?t=249775)

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