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One of the themes in my RC Blimp projects is building them smaller and smaller. First, because I like small things, but also to save on helium.

However, using lightweight RC gear usually raises the build cost. So in this project, I explored hacking a cheap toy RC car (scale 1/64) for the RC gear. It turned out to be fairly simple. One thing was less so: dealing with the very thin gauge copper wire these micro cars use for their magnetic steering actuator. However, for a workshop, I worked out at easier alternative, as shown in the last step.

The cheapest version uses an 11” latex balloon (a common party balloon), well inflated with helium to carry about 10g. The propellers are very simple and made from scratch (See step 5).

The result is small blimp that is suitable to fly at home or in somewhat larger halls. It can even fight some minor air drafts, but as for any small blimp, forget about flying outdoors.

The weight of the blimp is trimmed till it sinks slowly when no power is applied. The main motor pushes it forwards and upwards simultaneously. Dosing the forwards command allows flying at more or less the same level. Steering left and right is done with a tail motor. The controls on these cheap and tiny RC cars is on-off, not proportional. But actually that works better for the blimp than for the cars, as with the blimp you can use its inertia to your advantage.

Flight times easily exceed the driving time of the original Mini Racer used, reaching over 15 minutes.

Here is a video of the blimp flying:

Step 1: Parts, Tools and Supplies

Parts
  • a “Mini Racer” ($8.50 at DealExtreme or even under that)
  • 2 AA alkaline batteries (The cheapest source in Belgium is IKEA at €2.00 for 10, that is less than $0.60 for  the 2 you need)
  • a 0.5g “pager” motor (under $1.75 as in $5.20 for three at DealExtreme)
  • an 11” latex balloon treated with Hi-Float and inflated with helium (a balloon shop will take care of that for you, for under 2$).
  • some thin plastic sheet like from a butter cup (recycled)
  • Selotape/Scotch Tape, (a couple of cents worth)
  • a piece of bamboo or wood skewer (recycled)
  • a little non hardening clay to trim the weight of the blimp (or other easy to dose weights in the range of 0.1 -  3g)
Tools and supplies
  • a PH0 or PH00 screwdriver to open up the Mini Racer
  • a soldering iron and solder for electronics works.
  • some nail polish remover or a similar solvent (or, for the alternative explained in the last step, 2 x 50 cm of the thinnest gauge wire you can find, e.g. recycled from a discarded  mouse/USB cable)
  • a drop of superglue
  • a pin
  • a sharp hobby knife
  • scissors
  • a hammer
Depending on your sourcing the totally cost can vary, but as shown, it can be kept under $13. DealExtreme offers free shipping if you're willing to wait a couple of weeks. You can probably find the cars and pager motors at faster sources for still very low prices. In Europe you can get those tiny RC cars for at Conrad for €11 (and sometimes lessat special offers). Suitable pager motors can be found at Pollin for only €1.25, but removing the eccentric weight is harder.

Make sure the balloon is well inflated to 10 - 11” inch. Usually latex balloons are not fully inflated to their nominal size, to minimize the risk of them bursting during transport, like in a hot car. But if you take care on your trip home, you should be OK. The balloon should be inflated to carry 9g at least and some lift capacity to spare will keep you flying longer. In high altitude area’s you will need a larger balloon, try a 12” or larger one.

As said, you can get a prepped and helium inflated balloon at the balloon shop, but you can also rent a helium tank or buy a one-way canister. When using a one-way helium canister, take in account the helium sold in those is less pure (typically +- 85 %), diminishing the lift capacity accordingly. It still works but you will need a good 11” diameter. Pre-inflating with air (and emptying the balloon again) really helps to achieve a large enough size. Also buying some Hi-Float is worthwhile. The balloon will lose its spare lift capacity of a couple of grams in a matter of hours, a day at the most, but without a Hi-Float treatment those times will easily be halved. A longer lasting, but more expensive alternative is using foil balloons (also shown in the last but one step).

Step 2: The Mini Racer

These cheap and tiny RC Cars come under a number of names. Mine was a "Mini Racer". I found very similar "Tin Can" RC cars online in 27MHz, 35MHz and 40MHz and 49MHz. They do not come without any narrower bands. So you can only fly 4 at a time, by making sure they are on a different frequency. In most countries only some of the available frequencies will be legal, but it seems the frequency bans are often not enforced for these very low power toy RC systems. In Belgium 35 MHz is reserved for flying models but we’re turning the Mini Racer is one anyway.

Before dismantling the Mini Racer, charge it as described in its manual and take it for a test drive to make sure everything works.

This range is actually rather short (about 10m), but that is fine for a small “living room” flyer. I found on rc-cam.com that at least on some types, you can actually boost the range using a longer antenna and by doubling the transmitter’s voltage (add extra batteries). It seems those transmitters can handle up to 5V, but take care not to use that configuration for charging the flight battery. I didn't test this myself..

Step 3: Dismantling

Remove the bottom screws at the back and the front to remove the body. When taking further apart, make sure you do not pull on any wires. In particular first check and note where the two thin copper wires, coming from the steering, connect to the circuit board. These wires wire break real easy during further dismantling. I had to solder them back in place.

Before going for the rest of the screws, pry out the LEDs (two white at the front and depending on the model one or two red ones at the back). At this stage I kept on the LEDs. In my first build I later removed them to save weight, but the difference is only about 0.3g, so I recommend not to remove the lights unless you really need to lose a fraction of a gram in weight. After all some lights on your blimp are kind of cool.

Remove the screws holding the steering mechanism and the motor. Remove steering parts from the chassis except for the coil. Keep the two tiny magnets, they can be useful in other projects.

Unscrew the back motor mount. Push the motor from its plastic mount.

Push the switch out from the bottom, for example with the screwdriver. 


Tape in the circuit board, protecting the wire attachments, but keeping the switch and charging socket accessible. Test if things still work (including the charging).

Step 4: The Tail Motor

The steering actuator could be used to make a rudder. I actually found a description of a project doing that when hacking the Mini Racer to use in a model airplane. But, as to my experience a steering fin doesn’t work that well with slow moving blimps, I went for a tail rotor. I wasn’t sure the electronics would hold when replacing the actuator coil with a small motor, but that turned out fine.

The coil is glued to the chassis, but you can break it loose. At this stage I wanted to unwind the actuator coil for about 15 cm to make lightweight leads to the tail motor. But the windings turned out to be glued in place quit firmly. Only after soaking the coil in nail polish remover I could peel off a suitable length before breaking the wire. Put it in a small cup with nail polish remover or a similar solvent, making sure the cup is resistant to the solvent. It is best to cover it to minimize evaporation and ventilate the room. Let it soak for a couple of hours.

Of course you can use some other lightweight wire. If you want to keep the budget down you can recycle some from a discarded mouse or USB cable for example.

If the motor comes with a vibration weight on its axle, you will need to remove it, being careful not to damage the axle. I used this trick: I take the axle in between some pair of scissors or thin cutting pliers (don’t do this with your best scissors) and rest this loosely on some support (I used a bench vice). With a pin I tap the axle out of the weight.

Some of these small motors come with a square rubber sleeve. You can slide that right off.

To solder the thin copper wires I first make sure the ends have some solder on them. Apply plenty of heat and a good blob of solder to make sure the insulating enamel layer is removed by the high temperature. Don’t worry about the polarity when soldering to the tail motor, as this is sorted out when finishing the prop.

The insulation on the thin copper wire will probably be damaged by the solvent. So it is a good idea to no longer cross the wires. I kept them apart and at the same time protected them with tape, also covering the soldered connections.

Step 5: Making Propellers

The propellers are made from strips cut out of thin plastic sheet. The plastic used in cups containing butter, cheese or similar products is very suitable. I started out with two 25mm by 5 mm strips, leaving some room for trimming the propellers later. For these small blimps such rough propellers work well enough, but of course you can experiment what dimensions and shapes work best. For example, I learned that the propeller on the smaller tail motor, needed to be smaller to work well (I ended up with a total diameter of about 15 mm).

With a pin, a small hole is made in the middle of each strip. Some corrugated cardboard as a backing helps. If your pin should is thicker than the motor axle find another pin or take care not to push it completely through the plastic. The hole should keep a tight fit on the motor axle. So make a small hole and test fit each axle (the pinion gear on the main motor should be removed). Take care not to damage the motor and not to sting yourself with the axle.

Once the strip is on the axle, check the direction it spins for each command. Keep that in mind when twisting the strip ends each in opposite direction to form a rough propeller shape.

Do this for both propellers.

Step 6: Assembly and Test Flying

I cut a bamboo skewer even thinner and glued it perpendicular to the tail motor.

The main propulsion motor is taped to the circuit board in an angle of roughly 45°, making sure the propeller spins freely. I actually accidentally taped over the switch, but was still able to operate it.

The circuit board and the tail motor’s skewer are taped to the balloon. 
Add a little non hardening clay to trim the weight of the blimp till it just slow sinks when no power is applied. 
 You’re ready to fly (You might need to recharge first).

You can tune the main propeller's angle and the weight for a slower or faster cruising speed. A propeller pointing more downwards will give less thrust left for the forwards movement, which is better suited to flying in smaller rooms. Adding some weight might be needed to be able to give thrust about half of the time and achieve a reasonably smooth level flight.

Step 7: Further Improvements

In this project I tried to keep this build as cheap and as simple as possible. Obviously there is room for improvement. Some improvements can be done with recycled material, others at a cost of a couple of $.

The first one is using other balloons, latex or foil. I found some blimp shaped latex ones on eBay, lifting over 30g when used in full length. The cost of a helium fill is higher, but the spare lift capacity will make it last a week, instead of a day.

For even longer lasting fills go for foil balloons. You can adapt their shape with tape or, with some practice, make new heat seals as shown in my Hummingblimp Ible.

The 90 cm (40") long letters “I” foil balloons are a good size for this propulsion concept. They lift 13 to 17g depending on the helium quality. However there are two types: originally I had "sans serif" letters I, i.e. plain rectangles (used as a basis for the blimp shown in the first picture). But lately online suppliers, without updating the picture on their site, started to deliver "serif" style letters I, with protrusions at the end (as shown in the last but one picture). So if you want a plain rectangular shape, double check with your supplier.

When using longer balloons, it turned out the tail motor needed to be at the very back end to provide a long steering lever and get a decent manoeuvrability. As the main propulsion needs to remain in the middle of the balloon (both for weight distribution and a stable flight under thrust), the leads from the circuit board to the steering motor need to be lengthened. They should stretch about 60% of the length of the balloon.

I started replacing the thin copper wire with 1/10 mm enamelled copper wire (slightly thicker than the original). But for a sturdier solution I used 0,09 mm2 wire from a discarded computer mouse USB cable. I twisted the two wires, together with the twine that is also in the USB cable and soaked this this assembly in superglue to make it stiff by itself. That way the skewer could be omitted. I also kept the black sleeve on the motor when gluing it in place, allowing the motor to be repositioned.

The charging connecter can be replaced by a lighter solution, or be omitted completely when using clamps to charge the single cell.

If you have a gram or more to spare in lift capacity, you can add fins cut from foam trays. This makes flying straight out easier, which is particularly handy in larger rooms or halls.

In larger halls, using readymade propellers is also worthwhile. I used these from HobbyKing with great success. Again the tail propeller was shortened.

Step 8: Workshop

For a workshop I needed an easier and more robust way to connect the tail steering motor to the circuit board. This is what worked very well in a workshop with 7 young people (14 years old in average): 

After opening up the Mini Racer car and before taking anything apart, a scrap piece of circuit board is inserted under the thin copper wires. There should be no copper layer on top, as nothing should be soldered to the piece, it just serves to protect the plastic underneath when soldering, Keeping the wires well apart the long leads are soldered to each copper wire. A good blob of solder ensures isolating enamel is burned and good electrical contact is made. After that, a small drop of low temp hot melt glue is added to keep the soldered ends from touching each other. They should not be glued to the scrap piece of circuit board. After cutting the thin copper wires running to steering mechanism, the soldered connections are glued on top of the circuit board (making sure they do not touch any metal parts directly).

However this workshop did show the other wires (running to the main motor, switch, battery and charging socket) are the next vulnerable link. In a couple of builds one of these wires broke of at their soldered connections. So for a next workshop I plan not to remove the chassis, but only shorten it at the back and the front. A small test shows this does add about 2g to the build, so at least a 12 ̈ latex balloon will be needed. However for workshops, I’m planning to continue to use the 40" letter I balloons
<p>Hi</p><p>I know it has been some time since you did this project but don&acute;t you remember what was the output voltage from RC car circuitry? Was it the same for steering actuator and the motor? Do you have any tips where to find balloon foil?</p><p>Thank you for help :-)</p>
Hi,<br><br>The RC car is powered by a single 1.2V NiMH cell.<br>For the the receiver circuit and the led's this voltage is pumped up to about 3V, but the motor and actuator run at the original 1.2 V.<br><br>Foil balloons come from balloon shops and once in a while they have the foil foil on a roll too. The foil is hard to find. Once in a while you can find it at specialized (RC blimp) shops. West Coast Blimps used to carry it, but refused to sell outside the US and I can not find their site any more. You van try rc blimps canada.<br><br>For small projects the easiest is to buy large standard foil balloons and change their shape with a bag sealer.<br><br>succes!
<p>Thank you much for so prompt reply.</p><p>How are those LED&acute;s working? Do they work the way that only front or rear ones are lit? I would like to replace them with motors so they would be able to run in both directions. Do you remember if both red and white were at 3v? </p><p>Your idea of replacing roll with standard balloons is nice but I wonder if you can seal it with small bag sealer like this?</p><p>https://www.aliexpress.com/item/White-Mini-Portable-Electric-Sealing-Machine-Heat-Super-Sealer-Closer-Heating-Tool/32737995581.html?scm=1007.13338.71800.000000000000000&amp;pvid=757b0a97-36ff-4834-adf1-51162f33dc5c&amp;tpp=1</p>
<p>You're welcome.</p><p>The leds take a much lower power than any motor. The 3V circuit can not give enough current for motors. The LEDs must be on the RV as any LED needs lore than 1.2V.</p><p> Keep motors/actuators on the 1.2V.</p><p>I do not know if the small sealer does seal the foil. But it is impractical anyway. The outer ends of each seal are always bad, actually at those ends the material gets overheated an damaged, with a good chance on leaks.</p><p>I use a 30 cm sealer, taking care the outer ends of each seal are outside the shape I want. E.g. approaching a curve with a number of overlapping straight lines. Alas, convex shapes are impossible that way.</p><p>The 30 cm sealer I use is still reasonably cheap: https://www.aliexpress.com/item/Good-quality-all-matel-220v-12-200mm-sealing-length-and-2mm-wide-sealing-Heat-Sealer-Machine/32788517339.html</p><p>Keep me posted on your succes!</p>
<p>The problem I have there is that the motors I would like to use run on 3-5v (https://www.aliexpress.com/item/2PCS-DC3-5V-8520-8.... So my idea was to use step-up converter which however doesn&acute;t work in reverse (swapped polarity). </p><p>That is very inconvenient for me as I want to make the blimp go both backward and forward and also steering is going to be achieved using motors on each side working in opposite direction (4 motors in total). Now you see why I would love to get those sweet 3v instead of messing with bulky and &quot;heavy&quot; step-ups which may not even work. </p><p>Do you think there would be a way to achieve that?</p><p>I am also concerned about the range of remote control. You have mentioned there is a way to make it a bit better but increasing voltage of transmitter. Do you think it is a reliable long term solution? I&acute;ve seen a review where they tested &quot;grenade&quot; version of these tiny RC cars. The range was supposed to by significantly better with those. However, I have no idea how circuitry and voltages look like which is a big problem. </p>
Hi Jiř&iacute;K30,<br><br>Step-up convertors and motors are not a good match. But there are motors that work fine at 1.2V<br><br>However I'm guessing the controller in this Instructable does not match your project. It is very cheap, but not the most versatile.<br><br>If range is an important issue, you should think about a classic remote control system as used for model airplanes and such.<br><br>Read through my other blimp Instructables, in particular the Sub micro (spy) blimp: https://www.instructables.com/id/Masynmachiens-blimp-projects/<br><br>If you have some Arduino skills you could also go for another idea I have been lingering upon: using the app RemoteXY, a Wemos D1 mini pro and one or two Wemos motor shields.<br><br>Cheers,<br><br>Yvon<br>&quot;Masynmachien&quot;
<p>Thank you for great tips</p><p>I have decided to go for RemoteXY and Arduino Pro micro (chinese clone) + Bluetooth module. If nothing goes wrong it should be put together within 5 weeks. :-)</p>
<p>Hi Jir&iacute;K30,</p><p>That sounds like a good approach. I've had good success with the Blynk app and an Arduino nano, a bluetooth module, a small double H- bridge and a FET (for the upwards motor there is no reverse except gravity). I made a version where I can unplug in the modules and one were everything is soldered together.</p>
<p>Awesome man.. Thank you for posting this.. this post inspired me to make a blimp. I used a mini RC submarine.</p>
<p>I made it with the same Rc system but on the XL mylar globe balloons. They sure are fun to fly around the house, thanks for sharing this, </p>
<p>I made it! It has an interesting steering system in that it has both props in the centre.</p><p>The steering rotor is just an inch in front of the main rotor. It still turns but I can also go sideways and Straight up and down. Also I stacked two balloons on each other.</p>
Cool! Did you click the &quot;I made i button&quot;?<br>Thanks for sharing your experience with the alternative configuration. Can you post pictures?
<p>Any balloon with a lift capacity of about 15g is suitable. a bit more is better</p><p> Do you have balloon shops in your area?</p><p>If they do not have the balloon you want, they could order it for you, or they can inflate the balloon you've ordered online yourself.</p>
<p>We got a little crazy with the complexity and cost (and danger level) with our blimps (https://www.instructables.com/id/Battle-Blimps). I love how simple, easy, and low-cost your blimp is!</p>
THAT IS AWESOME!!! The future holds awesomeness!
Sweet! I still have 2 of those rc cars lying around. The future holds some blimp races in the office :D
<p>Thanks for posting this very thorough. next time i see a cheep rc car ill probably make one.</p>
<p>Although you mention a pager motor in the parts list, I don't see it mentioned/used further on. Am I missing something?</p>
<p>The &quot;pager&quot; motor becomes the tail motor in step 4.</p>
Thank you! <br>It brings me great pleasure to read my Ible engaged you to build a blimp too. <br>Also thanks for sharing the hints. Paperclips are indeed a very suitable alternative to the non hardening clay to trim the buoyancy .
Thank you for such an engaging instructable--it brought many hours of happy tinkering and experimenting. A couple things that really helped mine: a little $2 propeller from a local hobby shop(as you suggested), a little loop on the belly of the balloon to hang paper clips from: as the balloon loses helium these can be unhooked one at a time--a nice way to gauge remaining flight time. I took mine to a college reunion and floated it over the dance floor to much approval from the dancers.
Thanks for the great project! I'm still struggling to get mine off the ground. I started with one star-shaped foil balloon filled with helium, volume about 14 liters. When it failed to lift the parts off the ground, I added a second, which also failed to provide enough lift. So I checked to see how many US pennies it would lift: just three, about 8 grams. When I calculate lift based on a density for He of 0.1785 g/L I find that my two balloons should be able to lift almost 30 grams. Any ideas? Does Belgium have super rich He? Is our He being thinned?
oops...brilliant wife informs me that mylar balloons are that heavy. And now I notice your foil balloon is almost a meter long.
Indeed foil balloons (it actually isn't mylar) are rather heavy. You can check the helium chart from Qualatex (just google) to get an idea.<br>As surface varies with the power of 2 and volume with the power of 3, the bigger, the easier it gets to achieve enough lift. But with the low power here, keep it under a meter.<br>And sometimes the helium is less pure (typically in those one way canisters).
When I was making mine the back motor wouldn't work any suggestions?
Make sure it is well charched with good batteries in the transmitter. In the meanwhile, i learned the back motor quits first on a low battery.<br><br>I would first remove the propeller t see if it doesn't hamper the shaft's movement.<br><br>if it doesn't help, test the voltage on the leads to the motor (I guess you know how to do that). You should measure a voltage when givving a &quot;turn right&quot; command and an opposite voltage when giving a &quot;turn left&quot; command.<br><br>If you have something about 0.6 or more, then the connections are good up to that point and you should check al further connections. Check if the motor runs if you apply like 1.5V to it directly (e.g. from a battery). These tiny motors can be broken.<br><br>If you can not measure a voltage ever, male sure that were you soldered you did get to the copper (Do you have experience soldering that kind of wire). The invisable insulating layer should break down with heat, but maybe it did not. You can help establishing contact by sanding the wire ends.<br><br>Check the wires to see that they are not broken, but also if they are not short circuited. Don't rely on the invisible insulating wire, it can be damaged.<br><br>Making sure there is no short cicuit, measure the vultage on the solder points on the board, where the thin copper wires start. If you do not get any voltage respond to the commands, the board can be damaged. But those boards are quite robust.<br><br>Let me know when en how you got it to work. If it doesn't send me some detailed photos.<br><br>Succes,<br><br>Yvon
You can meet fantastic crazy geniuses only on instructables !!! <br> <br>Thank you for posting &hellip;&nbsp; <br> <br>(please give more !) <br> <br>you made my day !
Thank you! <br> <br>You can get such super nice comments only on Instructables!!! <br> <br>You too, you made my day! <br> <br>It certainly helps keeping up the work.
you mentioned building an airplane with these electronics, can you direct me to the plans for it?
It is the same link as mentionned in Step 2: http://www.rc-cam.com/microszr.htm <br>I will add it when I talking about the actuator too.
Masyn thank you so much holy cow! You are so great!
CUTE! love the idea how cool woul it be for like hundreds of these things in a hall XD
Decided I'd give this a try today. My plan was more of a zeppelin/airplane hybrid, but definitely in the spirit of the idea. I learned a couple things:<br> <br> 1. Check the battery size of the RC car in question <em>before</em> buying. My car took 3 AA batteries, so there's no chance it's going anywhere.<br> 2. Don't solder in your room of your apartment without first opening a window. Presently airing out my room.<br> 3. Always have spare wire around, whether you think you need it or not. My battery setup is using duct tape and the terminal wire (the springy stuff used to hold the batteries in place).<br> <br> While getting this to fly is likely going to be unsuccessful, I still had 15$ worth of fun trying this out! Thank you for posting!
awesome idea! I wonder what other ideas you can come up with using those motors..
awesome
Wonderful hack! I'm gonna make my first blimp with this one this winter :-)
Thanks! Go for it and keep me posted.
I have been meaning to try this for years! <br> <br>Great work - not only did you actually do what I have been meaning to get around to, but you did a much better job than was ever likely to! Lovely job.
Thanks!
Very cool job. I never would have thought to use those tiny race cars for something like this. Thumbs up!
CAT5 cable works well for things like this and it comes pretwisted

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