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motor for rubber FF conversion?

Old 04-13-2005, 09:47 AM
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Rick Lindsey
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Default motor for rubber FF conversion?

Hi guys, can anyone direct me to a source for lightweight motors that will run on 3.7V? I'm looking into what it would take to do some conversions of rubber FF models (first to simply add a rudder control and keep the rubber motor, but then I might as well throw in an electric motor since I can get the receiver with a built-in 10A ESC for only a few grams more).

The setup I'm looking at right now is a plantraco receiver (~8.4 grams with built-in ESC, 6 without it), single LiPo on the order of 150mAH (~3-5grams), and a single blue-bird 303 servo(~4 grams). I don't know how much the crystal, antenna, and assorted connectors/wiring will weigh yet though. Any suggestion as to the size rubber model I should be looking at to be able to carry this extra luggage? I was leaning towards outdoor models, since indoor flying just doesn't appeal to me yet (maybe that's because I've never been to an indoor fly-in), I'm hoping that their beefier size and construction will give a bit more leeway with the weight of the electronics.

Also, does anyone know how much thrust a typical rubber motor puts out? I'd like to see how the micro electric motors will compare.

If anyone has done a similar project (stick-and-tissue style FF conversion) then I'd appreciate any advice or insight you can offer! I don't expect to get any kind of aerobatic performance, more of an "assisted FF", where I can keep the plane in the right vicinity and hopefully not have it fly off into the swamp at the far end of the field . Keep the relaxing aspect of free flight, but cut down on the retrieval walk! Might be nice also with an electric motor to just keep it cruising around the field at a low altitude, rather than the typical climb and glide flight-path of a FF model. In fact, at first I was contemplating a throttle-only control, but the 1/2A folks convinced me that a small amount of rudder control would be a Good Thing(tm), and I'd already have the bulk of the electronics onboard anyhow, just need to add 1 servo.

thanks,
Rick
Old 04-13-2005, 11:56 PM
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rahtware
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Default RE: motor for rubber FF conversion?

Where to start...

First, to simplify your challenge, I would forget about the R-Thrust vs. E-Thrust issue, if you are like me it would only drive you nuts! As to converting R-Powered planes to E-Power, YES it can, and has been done. The first successful E-powered planes were either big gliders or scaled up R-Powered models. Something with a light airframe and lots of wing area.

Today you can convert just about anything, but the basic rules still apply... With enough power you can fly a brick... but it WILL fly like a BRICK. Stay away from heavy small models. You are starting at one of the extreme ends of viable RC so your choices will be limited. A light, RC assisted free flight model is (in my opinion) the best choice for the equipment and flying area you are talking about. Just don’t plan on flying it in any kind of wind.

Have you checked out: http://www.skyhooks.ca/WES.htm

This is a great site with lots of "toys" in the class that you are talking about.

One other thought (although I don't know how good it is) is to pick up a $39 Wattage Micro Flyer. It comes with; a 150mah LiPo, transmitter with built in charger for the LiPo, receiver/esc, direct drive motor with prop and an actuator for the rudder. If you haven't flown RC, before I guarantee you will crash it if you try to fly it! But, if you were to strip out the gear and install it in a 1 to 2oz airframe with a larger wing I think it could meet your requirements. The main problem with this system is the limited range of the receiver. A good thing about this setup is that the rudder is normally in neutral, and the RX has to be receiving a signal for the motor to run. Translated, this means that when the plane gets out of signal range it just shuts down and goes into glide mode.

Humm... I picked up a WMF to keep in the car to fly during lunch but have found it to be less fun (flying it) than I expected... Your post has started me thinking about doing just such a conversion.
Old 04-14-2005, 09:54 AM
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Rick Lindsey
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Default RE: motor for rubber FF conversion?

Actually, stripping the gear out of a Wattage MicroFlyer sounds like a stellar idea... The transition back to normal FF when it goes out of range sounds like a good feature, given the limited range (I had been looking at dual-conversion full-range rx's, but you pay a premium...).

I was thinking about something along the lines of a Sig Tiger, or a Peck-Polymers One-Night 28, or Flying Aces Moth to start with. Would they be appropriate? I'll go check out the microflyer after this post.

$39 for a micro-flyer is WAY cheaper than getting the gear I listed... Can the actuator be re-used with a reasonable amount of effort? I've got an LT-25 in the works (finished my ugly covering job earlier this week, on to hinging), so I'm going to learn to fly anyways, but I still like the idea of a small little model that will just cruise around the field at a stately pace... maybe bring back some childhood memories of flying my mini-maxer on my grandparent's farm .

-Rick
Old 04-14-2005, 08:45 PM
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rahtware
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Default RE: motor for rubber FF conversion?

Rick

You have opened Pandora’s box for me...

I dug through the garage and came up with a finished, but not-set-up-yet Peck Bostonian Pup!

http://www.peck-polymers.com/html/sport.htm

16" X 3 1/8" wing translates to 1 3/4 times the wing area of the Micro Flyer. Plus, the finished and covered airframe is a total of 13gms! I think this could be a winner. Did I mention that it is designed to have movable control surfaces? Normally they are mounted on thin, bendable wire so they can be moved to change trim with out rewarping the whole surface.

The rudder cutout is about the same percentage of the vertical stabilizer as the one on the WMF. Another perk is that as a free flight model, it has raised wing tips. This will tend to help get the plane back to level flight after a turn. Now if only I can find the control surfaces and nose block... They have to be in one of my boxes of rubber powered planes.

I will be stripping the gear out of the WMF tonight so will get back to you with info and pictures.
Old 04-15-2005, 11:33 PM
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Default RE: motor for rubber FF conversion?

You may want to also take a look at the Syma supersonic...mini rtf..from raidentech.com....I just ordered 4 of these ..and this plane is dying to be remodded with servos/esc/lipos/etc...and turned into a 3 channel full function micro...as it is now in stk form..it flys very nicely..and has a great range..but whats even better is the inside of the plane is hollow..so there is room to mount/add electronic components..it is setup to turn/left/right/up down..just by 2 motors..and thrust differential..and actually works quite well..but Id love to find someone that can instruct on how to convert this to a full function micro..and advise what components would be cheapest/best...
Old 04-15-2005, 11:45 PM
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Default RE: motor for rubber FF conversion?

another nice thing is its only $24.95...so you get a plane that flys nicley stock..or a plane that is perfexct for modding...
Old 04-16-2005, 12:56 AM
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rahtware
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Default RE: motor for rubber FF conversion?

Ah yes, but the radio gear in it is useless in another plane. My experiment is to see how feasible it is to transfer the extremely cheap and fairly light radio/power system out of the WMF into a better plane. So far it has gone OK. I have the gear set up in the Peck Bostonian Pup and it actually works. The pup has ended up weighing 36g which is heaver then I wanted, but even at that it's wing loading is under 4oz/sqft whereas the WMF worked out to be over 5. I think I can trim off another 5 or 6 grams by changing out the battery connectors and the wire that I ran back to the actuator.

I didn't take any pictures yet, but will before I cras... fly it.

If this works out I have my eyes on a cute little 20” glider…


Old 04-19-2005, 12:25 PM
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Rick Lindsey
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Default RE: motor for rubber FF conversion?

ORIGINAL: rahtware
I didn't take any pictures yet, but will before I cras... fly it.

If this works out I have my eyes on a cute little 20” glider…
So... did it work? If so, how big do you think you could go with the wmf hardware? I've had my eyes on a PP Flying Aces Moth, or an EasyBuilt Skokie (both 24" span), but I also considered a Sig Tiger (21.5" span, spec'd to weigh 1oz, dunno if that includes rubber or not).

Any pictures would be great, especially of the rudder control installation.

thanks,
Rick
Old 04-19-2005, 08:31 PM
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rahtware
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Default RE: motor for rubber FF conversion?

Just finished it today, and of course it is too windy for a test flight. Here are a couple of pictures of the instillation. Please forgive the botched covering job on the horizontal stab... I had to change the size and shape of the aft vert brace and the rudder, but didn’t want to recover so just slid and glued them in place.

As for positioning the actuator and magnet, I just copied the mounting measurements of the WMF for setting everything up.

I did replace the motor wires with longer ones so the receiver could be in the cockpit, and I had to replace the wires back to the actuator. The lightest I could get locally was single strand antenna wire from Radio Shack.

RTF it still comes in at 36 grams... Can't wait to try it out.
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Old 04-19-2005, 09:40 PM
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rahtware
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Default RE: motor for rubber FF conversion?

Flight results!!!

Flight #1. ROG into a bush! Caused by a slight left turn tendency. Battery came through tissue floor, knocked nose off of the motor.

Replaced the cockpit floor with cross grain 1/16" balsa. Glued the nose on and glued in a little right thrust.

Flight #2. ROG... Cross breeze came up... I over corrected and plane dove into ground. Glue wasn't dry on motor so knocked front off again... This time I lost the little spring from the prop shaft.

Re glued nose.

Flight #3 Hand launch into slight breeze. FLEW GREAT!!! Even though I had only used one rubber band on the wing, which ended up slightly eschew, the little PPB Pup flew better than the WMF! And the power off landing was straight and the glide angle was much moreshallow than the WMF.

Weight now up to 38 grams.

I know this little stick and tissue plane won't hold up as well as the WMF, but it is a much more forgiving flyer than the foamie.

I think this power system could fly something in the 20" -24" range, as long as the RTF weight was kept under 2ozs... Which will be my nest test.

Good luck
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Old 04-20-2005, 08:53 AM
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Rick Lindsey
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Default RE: motor for rubber FF conversion?

Thanks for the pics and the flight report! If you don't mind more questions from the ignorant newbie -- what did you use for hinges on the rudder? Those don't resemble any hinge I've seen before (unless they're hinge points?)

Also, do you know how much the WMF electronics package weighs? I've decided to start with a Sig Tiger, I might even build two so that I can leave one stock and have the other to monkey around with. Even if it's 1oz weight is without rubber, I'm assuming the WMF electronics come in well under an ounce?

thanks,
Rick
Old 04-20-2005, 10:13 AM
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rahtware
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Default RE: motor for rubber FF conversion?

Rick

Sorry about the sketchy details.

The hinges are the original rubber band hinges that I dug out of the WMF. It sounds like a cheap way to go, but as an actuator isn't self-centering the rubber band hinge is able to fulfill both the SC and hinge roles.

The electronics came in at 18 grams total (including battery). I did make some changes, but the weight stayed about the same. I got rid of the WMF contacts/mounting block as it was big, bulky and didn't work all that well. In its place I soldered Deans mini connectors, one to the circuit board and another to the battery. On the battery I soldered the connector wires to the battery tabs and then filed them so the battery can still fit into the charging slot on the transmitter. I will try to take a better picture after work today.

I checked out your choices and liked them all. Have you built "stick and tissue" before?

The nice thing about this radio system converting over to a rubber design is that the actuator in the tail balances out the motor in the nose. Most rubber designs have long noses as the center of the mass of the rubber has to match the CG point or the plane. In the Pup I used the receiver and battery to further adjust the CG.

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Old 04-20-2005, 12:35 PM
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Rick Lindsey
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Default RE: motor for rubber FF conversion?

Ah, no wonder I didn't recognize the hinges! That's one less thing to worry about, though, if I can just dig them out of the WMF.

It's been a long time since I've built stick and tissue (read 15 years or more). I built a couple guillows models as a kid (though only one was ever completed and "flown"), and a mini-maxer long long ago. I also built an AMA racer this past weekend -- at $3, how can you go wrong? Sig recommends the Tiger as a "first built-up cabin model", so I'm hoping it's an easy build! I really like the look of that style plane (as if that wasn't obvious from my other choices) so I'm thinking to move up to the Skokie after I build a tiger or two. I got spoiled by the laser-cutting of my LT-25, though I suspect if I really get into stick-and-tissue models that I'll have to learn to love my x-acto knife and home-made printwood *grin*.

The only drawback I've seen to these WMF electronics seems to be the charge time -- 45 minutes charging to get a 6 minute flight? How hard would it be to duplicate the "charge plug" so that one could buy extra LiPo cells to extend a flying session beyond one flight per hour (charging them all ahead of time and swapping out batteries between flights)? I've seen a cheap lipo charger that only does single cells, but I'd just as soon use the xmitter charger rather than have to buy extra equipment.

-Rick
Old 04-20-2005, 08:42 PM
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Default RE: motor for rubber FF conversion?

Rick

I have to wonder where they get that 45 min. charge time. Mine never takes over 20 minutes to charge, but I have to add that I don't take it down to a completely dead battery before charging. I put in a 4 to 6 min flight and charge while I fly my T-Moth. Throw in a little BS-ing and the darn thing is ready to fly again.

I have to tell you about flight #4... This AM, before work, it was finally dead calm so even though I was running late I just had to toss the Pup to see how it did without a wind. To my surprise it has a flaw that didn't show up yesterday. The Pup is TOO stable! If I just blipped the rudder the tail would swing as if to turn, but then swing back the other way and continue on the original heading. To make a turn I have to blip the button about 5 or 6 times in a row. I think this stability is due to the polyhedral wing. I'm not complaining, as it is much easier to fly than the WMF. And landings!!! I cut the motor at the same height that I cut it in the WMF, but the Pup didn't drop as fast so I had to add an extra circle to the landing pattern. When she did set down it was almost a spot landing with one bounce and a little rollout. I think I will postpone transferring the gear for a while and just play around with the Pup.

As for S&T building, I like it although the planes are fragile as eggs... Maybe that is why I enjoy flying these, light little birds. One thought is to use either one of the new light films or even saran wrap instead of tissue. Nothing worse then landing in a dew covered field with a tissue-covered model. And, if you dope it, it can get as heavy as the new films.

Time for dinner, will get back to you soon with some other ideas.
Old 04-21-2005, 02:29 PM
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Rick Lindsey
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Default RE: motor for rubber FF conversion?

Cool, 20 minutes between flights sounds better than 45. On the ruder blipping -- I take it you can't simply hold down the button to get the rudder to stay offset? That's kind of a shame if it works that way, I had assumed you could hold down the "right button" to get sustained right rudder. I wonder if it's got something to do with the way the actuator works (charging a cap or something to get enough oomph to move the rudder?) or just "dummyproofing" to prevent someone fro holding the rudder down too long and spiraling into the ground?

I'm not surprised a single blip of rudder doesn't do much to turn a craft with significant dihedral... Do you think increasing the rudder area might give better authority? I was planning to use a rather small rudder, so as not to enter a Death Spiral if I held it too long, but it sounds as if a largeish rudder might be in order?

Do you think you could do touch-and-goes with your Pup?

As far as tissue vs. plastic goes, i'd like to stick with tissue and try to keep the dope light (also, one can supposedly spray on Krylon to get a good finish without the weight (or extra strength) of dope?), but I've heard of something called "airspan" that should be ueber light... part of the appeal to me was doing this in a "stick-and-tissue" model, "stick-and-plastic film" just doesn't sound quite the same . If that's what it takes, though, so be it!

-Rick
Old 04-22-2005, 10:19 AM
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Default RE: motor for rubber FF conversion?

Cool, 20 minutes between flights sounds better than 45.
One thing that is a contributing factor to the length of charging time is the condition of the batteries in the transmitter. Tired batteries from a Costco brick are going to require a longer time to recharge the flight battery then a fresh set of Duracells.

On the ruder blipping -- I'm not surprised a single blip of rudder doesn't do much to turn a craft with significant dihedral... Do you think increasing the rudder area might give better authority? I was planning to use a rather small rudder, so as not to enter a Death Spiral if I held it too long, but it sounds as if a largeish rudder might be in order?
You have touched on the heart of the WMF to Rubber-powered plane conversion issue. Freeflight planes are designed to have stable flight characteristics, our conversions have to overcome this and yet, because of the lack of elevator control, not totally destroy the models ability to self stabilize in the horizontal plane. The other challenge is the lack of proportional control in the rudder throw. The problem With the Pup is not a lack of rudder authority, but rather limiting the amount of control it has over the model while maintaining the horizontal stability. If anything, the rudder on the Pup is too large, and thus has too much authority.

The transmitter does not control the length of time that the rudder is held over. When you push one of the turn buttons the rudder swings to full throw and stays there until you release the button. Blipping the turn button is a very crude method of achieving proportional control with this radio. If I were to hold the button down until the model has completed it’s turn it would be in so steep a nose down attitude that to recover it would zoom to a stall. Your idea of a small rudder is definitely the way to go, just don’t be surprise if your model has problems responding to input.

Do you think you could do touch-and-goes with your Pup?
I think so, although it would be more like a “bounce and go!”

As far as tissue vs. plastic goes, i'd like to stick with tissue and try to keep the dope light (also, one can supposedly spray on Krylon to get a good finish without the weight (or extra strength) of dope?), but I've heard of something called "airspan" that should be ueber light... part of the appeal to me was doing this in a "stick-and-tissue" model, "stick and plastic film" just doesn't sound quite the same . If that's what it takes, though, so be it!
I too like the look of tissue on a stick built model. I built the Pup about three years ago with the intention of flying it exclusively indoors, thus “dry” tissue, I am looking into alternative covering products that maintain this look for my next project. I think that the use of Krylon, or any of the other enamel spray paint would result in a much heaver covering than the traditional “(thinned and) brushed on clear dope and colored tissue” finish. Besides, when a produce is sprayed on a porous covering material the product usually penetrates the covering and ends up on the frame materials resulting in a much heaver plane.
Old 04-26-2005, 01:33 PM
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Rick Lindsey
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Default RE: motor for rubber FF conversion?

Would it be possible to add some sort of servo-arm to the actuator so that it could be mounted remotely (and so that the amount of rudder throw could be adjusted)? It'd be alot nicer to adjust the rudder throw by adjusting the pull/pull horns than by changing the rudder size itself to find the right balance between sufficient turning authority and the Death Spiral...

-Rick
Old 04-26-2005, 10:02 PM
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Default RE: motor for rubber FF conversion?

Rick

It is possible, and has been done. I'll see if I can find the article... I think it was in MicroRC mag.

I wonder if you would be better off going with a "real" radio and a Slow Stick. The reason I was able to fly the Pup before destroying it has a bit to do with 25 years of RC and 5 years playing with rubber-powered indoor planes. Even though my first flights ended prematurely, the Pup was close enough to "right" to not end up with too much damage. I'm not trying to talk you out of this project (I have been looking at the Tiger now myself), but I worry as I have seen too many potentially good pilots give up on this hobby due to a combination of poor plane choice and lack of training.

As far as I have heard, with a bit of help for the first few flights, the LT-25 is an excellent trainer. If you could find an experienced pilot to help you learn to fly it your success rate with the little stuff would be much greater.

Just a thought
Old 04-27-2005, 09:42 AM
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Default RE: motor for rubber FF conversion?

Oh, I'll definately have an instructor for learning to fly the LT-25. It sounds like RC'ifying a free-flight should wait until after i learn to fly my trainer, I was hoping it'd actually be easier to fly, but I suppose that diverging from the proven good FF design by tweaking the tailfeathers, adding weight, changing rubber to electric etc. might be more difficult than it appears at first glance?

I'm still planning to get and build the Tiger stock first anyways, so the RC conversion might get stuck on the back burner until I'm more comfortable with both FF and RC rather than a rank beginner at both.

-Rick
Old 04-27-2005, 09:10 PM
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Default RE: motor for rubber FF conversion?

Good plan Rick,

Hey, I found this in the January 1986 issue of Model Builder magazine.
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