Ideas for a flywheel to get a nice feeling to aircraft props

Discussion in 'Tips, Tutorials & Tools' started by Leif Oh, Jun 23, 2004.

  1. Leif Oh

    Leif Oh Member

    I've been thinking about making a fake "motor", to get a flywheel effect on aircraft props. The problem is how to make this as simply as possible, both constructing and installing it.

    Advantages are that you would get a nice, heavy feeling to your prop, which should rotate quite a few revs whenever prodded. Also, you would get ballast weight where you need it, to get the CG of aircrafts with nosewheels more right (think of a twin-engined P38 as an example). It's simpler to install than an electric motor (which I have done so far, but never run very much; plus it's a pain to get the electric outlets tidy and connect them to the external battery).

    Requirements should be that the entire unit ought to be able to install from the front of the finished aircraft, into holes 15-20 mm dia in the front 2-3 formers (strategic decision to be made before starting fuse construction), thus also reinforcing and helping to align front part of the fuselage.

    The unit should be simple to make, requiring no exotic material or tools, preferably paper and some plastic tubing and pianowire, plus widely available material for the flywheel itself. No metalworks should be required. Preferably, white glue should be possible to use all the way.

    Here's an idea how it might be made, in ten easy steps:

    1. Get RC push-rod plastic tubings, inner and outer, plus pianowire (ca 0.75-1mm) to fit in the inner tube to make it rigid. These will be axis and bearings.

    2. Get washers (a small load of them) of the proper outer diameter (15-20 mm; not critical, but should of course fit inside the largest diameter possible for your model) from the hardware store. The inner hole to be as small as possible (greatest weight per washer). Many of these stacked will become the flywheel to fit onto the axis.

    3. Cut a length of the inner plastic tube, insert and glue pianowire of same length. Glue a piece of the outer tube near one end. Length of this will be length of the flywheel portion of the rotor.

    4. Laminate all but the very ends of this outer tube with copy paper until diameter is the same as inner holes of washers to be used. Fill the laminated portion with washers, glueing them together. This will be the rotor, creating the flywheel effect.

    5. Make circular end-pieces of 1 mm card to slightly less than outer diameter of the envisaged unit. Glue in small pieces of outer plastic tubing as bearings, length 1 mm more than thickness of endpieces, to rotate against laminated portion of rotor axis and provide clearing from endpieces. Put one of these end-piece assemblys on each end of the rotor axis, butted up against the outer dia portion of the rotor.

    6. Construct outer layer by simply rolling and glueing the whole outfit onto print paper (one layer). Continue laminating with copy paper until outer diameter is correct for the holes already made in the front formers. Trim ends.

    7. Cut protruding ends of axis (inner tubing plus piano wire) to correct lenght - virtually none at the back, and enough at front to accept the prop and spinner unit. This finishes the fake "motor" unit, now looking like a small electric motor with the perfect diameter and length for your model.

    8. Insert into already finished fuselage and glue. Basically, the front end of the "motor" will be flush with the front end of the first former. Hopefully very little pain or adjustment will be required, since exact length is uncritical (if you got your initial measurements roughly right).

    9. Build the spinner and prop assembly onto a piece of the outer plastic tubing, instead of the usual paper tube or toothpick or whatever. A few more washers could be installed within the spinner, on a laminated portion of the outer tube, for extra flywheel effect (optional). Test run the assembly on a scrap piece of axis to check for alignment of prop blades.

    10. When the time for final assembly comes, just push the prop & spinner assembly onto the prop axis protruding from the fake motor, and glue it to the axis.

    Do y'all think this might work? Refinements? Better materials? Potential snags?

    Leif Oh
  2. 57townsman

    57townsman Member

    Wow, you put a lot of thought into this :shock: Sounds to me like it should work very well and you have worked out most of the details already. Anyone want to build one??

  3. Leif Oh

    Leif Oh Member

    Flywheel "engine" made

    OK, so I did the flywheel "engine", just to see if it would work. And it did - but the conclusion is that it's hardly worth the trouble, with a small electric motor obtainable for just 1-2 euros. Even if left unconnected, it will still make for a smoother running prop. Anyway, here's how it all turned out:


    Here, all the basic ingredients have been laid out:

    Materials: 10 washers (outer dia 20 mm, inner 3 mm). Lengths of plastic tubing (RC model inner and outer control tubes). 0.8 mm pianowire. All of which goes inside each other. 1 mm card, plus some 0.25 mm regular card.

    Tools: OLFA circle cutter. Hole punch. Piano wire cutter.

    A number of 20 mm dia discs were cut out to go between the washers (unneccessary, but I wanted the length of the finished engine to be well in excess of the distance between the two first formers of the prospected plane; the rotor might just as well be long then).

    End discs (even more than in the picture above) were cut from 1 mm card to a diameter of 22 mm (2 mm larger than the rotor to provide internal clearance).


    The three main parts assembled: Two end plates, and the rotor, all laminated on bits of larger dia plastic tubing.

    In addition, the rotor is glued to the smaller diameter plastic wire (with piano wire inside to provide some rigidity).

    White glue used throughout (although I must admit the rotor would have been better glued to the axis using thick cyanoacrylat).


    Outer casing (ordinary 0.25 mm) is about to go on. The paper strip is cut at the correct length; when it's finished there is only one layer.


    The finished product, matt grey paint hardly dried, compared to an ordinary electric motor.

    The flywheel effect certainly is there, but after an evening of it, I am still not sure it's worth the trouble.

    The flywheel enginge could be made much smaller (both in length and diameter), which is an advantage for particular needs. Another advantage is that you can make it in virtually any length you decide, in order to fit between two formers.

    It was satisfying to realize an idea. And it certainly would be something to brag about, showing off your model. But all in all, in the future I think I might continue to mount small electric engines butt to the back of the front former. It really is a whole lot easier.

    Leif Oh.
  4. Gil

    Gil Active Member


    Putting the weight toward the tip of the propeller will provide a greater "flywheel effect". I suspect that coiling some solder to fit inside the propeller envelope would be very conducive toward producing the effect desired.

    Best regards, Gil
  5. Jim Nunn

    Jim Nunn Member

  6. Leif Oh

    Leif Oh Member

    Gil, you're probably right. And if there's a spinner, a number of washers could go inside that instead.

    The plastic tubings, and piano wire will still come in handy in preparing a finished prop unit that can simply be pushed into the finished model from the front, in a 3 mm hole through the two first bulkheads. If still greater weight is desirable, a number of washers can be glued to the back of the front bulkhead.

    Much simpler. Thanks for the obvious suggestion.

    Jim, your little vibrator motors are beauties. Unfortunately, they fall into the cathegory of "not readily available", at least not for me here in Sweden. I checked with the local hobby shop. They do have pretty good ones, though, for a dollar, or a euro.

    The problem with electrifying models, as I already found out, is the amount of work involved in preparing outlets and connectors, plus a suitable battery case. I have tried simple wire loops taped to a battery, and it works, but it's not pretty.

    And internal batteries would require recharging, special connectors, a lot of wiring, plus probably soldiering. While I would probably be up to it, it is beyond what is fun in card modeling, the simplicity of tools and techniques.

  7. Gil

    Gil Active Member


    Use a small electric fan to spin the prop for photographs....,

    Best regards, Gil
  8. 57townsman

    57townsman Member

    Electrical connections can be disguised as fuel lines and power connections to ground handling equipment. Small batteries can then be hidden in said equipment along with a switch or run through it into a base.

    You could also run power through the wire reinforcement in the landing gear.

    Just brainstorming :lol:

  9. j77ason

    j77ason New Member

    I have to laugh (a bit). I used to build my wheels like that - punching them out of card with a number of punches I had made up in an engineering shop - from various diameters of metal tubing. - So tell me how do you find dead centre, so when you spin your disks, they don't wobble?
    There is an easy way..........
    We have sweets called Chuppa Chup - these things are a boiled sweet which is stuck on the end of a round white nylon tube. What the kids do here is eat the sweet and chuck the tube (sticks) away, wherever they happen to be ( usually on parks etc)
    I collect the Cotton Buds I use. That is to say, I cut the cotton wool ends off and I am left with a nylon shaft which is hollow, then I go out on fossiking walks, to pick up used Chuppa Chup sticks.
    The Cotton Bud round nylon shaft fits neatly in some of the Chuppa Chup nylon sticks. On tight ones, a round wood tooth pick works just as well.
    Thus, I have a free axle, bearing, hinge or whatever part I wish to build this into.
    By the same token, I can strengthen the cotton bud tube, by straightening a paper clip ( thin wire) and inserting it up the nylon cotton bud tube.
    Now, lets say you wish to build a hub which will freely spin - from that hub you can build on many other things - right?
    OK - measure the width of the hub you wish to build - but let's say 4mm thick for this explanation.

    Get a sheet of thin card or even photocopy paper and cut strips 4mm wide, by as long as the sheet.
    Glue one side of the strip with PVA glue - along the full length, then carefully wrap one end around the outside of a Chuppa Chup stick (or plastic tube bought from a hobby shop of the appropriate diameter - just fits around the cotton bud, no wobble).
    Now, wind the rest of the glued strip onto the Chuppa Chup tube, occasionally gently pulling the strip to make sure you have a tight fit. Keep building up the diameter of the hub until you have reached the desired diameter. Put aside, allow to dry.
    If you are making a number of hubs, do them all at the same time. The length of strip will be determined by how many you use on the first hub. Thus making the rest with the same lengths, wil create uniform hubs in diameter.
    Then use a sharp hobby knife to cut off that 4mm wide hub which is now the tube with the paper or card glued to it with PVA glue. (enough Glue as you would find on the back of a wet postage stamp).
    When you put that tube on the Cotton Bud stick and spin it, if you have made it correctly, it should spin without any wobble.
    Obviously, the length of the Cotton Bud Stick should be outside of both ends. You can use a thin Chuppa slice, either side of the hub, glued in place with PVA or Super Glue to hold the assembly together - then it is just a simple case of completing the part concerned.
    you can PVA glue the prop or whatever, after assembly and painting with acryllic paint or a water based paint - this will strengthen the overall part.
    I use this process to construct wheels for tanks and AFV's and cars and trucks, etc. Also on a Putilow Garford Russian Armoured Truck of 1917, I built up the inner wheels this way, then used the card model pattern to cut out spokes - so when I'd finished I had spoked wheels - but without any rims or tyres.
    I then constructed a round plug to the outside diameter of the spoked wheels (in the same way) - then I used that to construct rims and "solid rubber" tyres for each axle (4 wheels on the back, 2 on the front.
    I wrapped the first layer of card around the plug, without glueing it (because I wanted to push of the finished rim/tyre and mount it separately onto the above spoked wheels).
    In this way I was able to build authentic wheels for my model which I built at 1/15 scale.
    PVA glue dries clear, so it is easy to "rivet" parts of a model with authentic raised rivets. Just droplets of glue which you allow to dry - of a uniform shape and size. Just paint over them to get the looks.
    Yep, I build all of my models in black & white, detail them myself and use water based paints or acryllics to finish them off - real windows and doors, etc.

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