Retro (about 20 years old) r/c model hovercraft

[optima21]

for some reason I've recently become interested in radio controlled model hovercaft, so I thought I's gently dip my toes into the water so got an old school taiyo edge off ebay, I got it for less than £18 including postage but came without a transmitter , which wasnt an issue as I planned to upgrade the radio gear to todays modern 2.4GHz systems rather than the old 27Mhz systems.

if you look on youtube a few of these have already converted to modern radio gear and now use 3s lipo batteries so the batteries are 11.1v instead of 9.6V, but I want my radio controlled toys to un on 3.7v batteries, which meant that everything electrical on it would need to be replaced. One of the issues with working with low voltages is the voltage drop as the current increases, when you're just using 1 cell in series but not a problem when using multiple batteries in series. A result of this was that I started in measuring the voltage drop across different connectors and wire sizes. I was lucky that I found suitable new motors that were the same size as the old ones, but ditched the old direction propellers as I made adaptors that allowed me to try different 5" quad propellers that were cut down to size, so I could try ones with different pitches and number of blades. with the thrust being measured on a scale and compared to the current drawn

and the electronics, I used the original housing as it is waterproof, on the left is the lift motor, and that is switched on by the white cam on the right which operates a tiny microswitch below it, but that cant handle the current of the motor (about 3.5 amps) so that uses a tiny mosfet to turn the motor on and off. ( the contacts for the switch were originally on the circuit board that operated the radio gear and motors but that was thrown away, but I think my way of doing it was a neat solution to the problem. both of the thrust motors have a separate speed controller, the are designed to work at a higher voltage than I used, but with a bit of simple rewiring work fine (and they were cheap too) I got 5 for £14 delivered but looks like the price has gone up

1 / 2 / 5 / 10 / 20 / 50 /100 pcs 20A Bustophedon ESC Brushed Speed Controller For RC Car Truck Boat Remote Control Toys - AliExpress 26

Smarter Shopping, Better Living! Aliexpress.com

www.aliexpress.com

and above the cam on the right is the radio control receiver than I use

and there is all the electric waiting to go, complete with batteries, but more about that in a follow up post, and something unusual about their usage in radio controlled models

with the battery at the front being lighter than the original one (and providing more power), it made sense to reduce some weight at the back, so most of the propeller shroud was removed. Im old enough to know that you dont stick your fingers in propellers and if you do its your own fault, and secondly it has to slow the hovercraft down.

before I got to this stage I got another similar one off ebay, its a later one that is a copy of the one Ive modified, its all complete and working ( the yellow one at the pic at the bottom) and that cost £16 including postage, but its another future project but at least I could compare the performance of a standard one and my modified and and the modified one has 30% more thrust that the standard one and the thrust is measured by sticking it in a digital luggage scale, resetting the weight to zero and then giving it full throttle, (nice and easy once you've worked out how to do it ) and the weight of the modified one is 50 grams lighter too.

then its time to take it out for a play and compare it to the standard one. they are only suitable for going on a polished wooden floor or water, but since Im a member of a model boating club they are getting used to me doing my own thing. the standard one and the modified ones are like night and day,

1) duration - with the modified one it'll run for 30 to 45 minutes but the standard one is 10 to 15 minutes run time mix.
2) steering - the standard transmitter is awful to use as each thust motor has its own forward/reverse control so to turn right you move the left stick forward and to turn right you move the left stick forward. with modern radio gear it can work out the magic so its simple left and right on one stick and forwards/backwards on the other.
3) thurst - the increase in thrust means that it is faster over the water, and the increase in speed and the controllable steering mean that you can drift it too, which is more fun than going in a straight line. I can change the propellers to higher pitch ones to get more thrust if required, but the duration will go down.

and a few weeks ago I saw a smaller one on ebay, but from the pics couldnt see how it go lift, its was complete without a battery charger, but cost less than £14 including postage so thats another project., buts performance worse than the yellow one, but they are cheap toys to play with.

so thats something that Ive been playing with recently, I need to do another post on here about using Li-ion batteries and also using mosfets for low speed switching as it may be of help to other people, we have all different hobbies catered for on this site

 

[carbon]

I built one some years ago. I used a glow plug engine but struggled with power to drive the fan I made when in it was fitted in the hovercraft. I’ve recently changed it to electric but need to remove a baffle I have inside but haven’t found the time to do it



And now with the electric motor fitted

 

[selectedgrub]

I would steampunk the hell out of one of those.
Probably wouldn't float.

 

[optima21]

now for some of my ramblings about Lithium Ion Batteries, for most people any one will do, but because I use single cell voltages any voltage drop can make a difference to the performance of the models..

To power this hovercraft I decided to use Li-Ion (Lithium Ion) batteries rather than the more normal Li-Po (Lithium Polymer) batteries that are normally used for radio control applications. Its easy to get the two mixed up if you arnt too familiar with them and for most purposes they are interchangeable. the easy way to spot the difference is that the LI-ion batteries are cylindrical in shape and the Li-Po batteries are normally cuboid in shape. The Li-ion battery can normally be found in power tools and electric vehicles and the Li-Po batteries can be found in mobile phones.

the 18650 will be the most common form of the Li-ion battery, and that dictates its size e.g. 18mm diameter and 65mm long and these are the ones that I have got over the past couple of years (apart from the one that was in a model boat that sunk).

and they are from left to right

manufacturer/model	size	capacity	max discharge current	cell protection	model info
Amplus 14500	14500	1000mAH	10A	no	Ampsplus 14500 1000mAh 10A Battery Button Ampsplus 14500 1000mAh 10A 3.7V Battery ButtonMax. Continuos Discharge Current: 10A, Version: Button TopModel: A145001000HD10BT, Rechargeable BatteryBattery Designed for Torch, Light, Laser, Nerf, Vape, ModUK Brand, Tested and Certified, No memory effectSee more in Product Description. www.ampsplus.co.uk
Vapex VP18650F	18650	2600mAH	5A	yes	3.7V 2600mAh Li-ion 18650 Single Cell Battery ( Flat top) Vapex Dimensions: 68.1 mm long x 18.7mm diameter. Discharge: 5A Weight: 40g www.componentshop.co.uk
Sony VTC5A	18650	2600 mAH	25A	no	Sony/ Murata VTC5A - 18650 Battery 2600mAh - 25A Continuous Discharge - Flat TopOrder by 3pm (Monday to Friday) for same day dispatch!Brand: Sony/MurataModel: VTC5A (US18650VTC5A)Size: 18650Chemistry: NMCNominal Capacity: 2600mAhNominal Voltage: 3.6VDischarge: 25A Max Continuous (35A Max Continuous with a temperature limit of... www.18650.uk
Sony VTC6A	21700	4000mAH	30A	no	Sony/ Murata VTC6A - 21700 Battery 4000mAh - 30A Continuous Discharge - Flat TopOrder by 3pm (Monday to Friday) for same day dispatch!Brand: Sony/MurataModel: VTC6ASize: 21700Chemistry: IMRNominal Capacity: 4000mAhNominal Voltage: 3.6VDischarge: 30A Max ContinuousPositive: Flat TopProtected: NORechargeable: YesDimensions: 21.1mm... www.18650.uk
Amplus 26650	26650	5300mAH	20A	no	Ampsplus 26650 5300mAh 20A Battery Ampsplus 26650 5300mAh 3.7v Li-Ion 20A INR Rechargeable Battery / FlatVer. 2021, Free Zip case with each pair of batteriesHigh Capacity and High Drain battery designed for HID LED Torch, Flashlight, LightUK Brand, Tested, Fully UK / EU Battery Regulation & Compliant CellMay be used for Vaping... www.ampsplus.co.uk

there are two of the Sony VTC6A's in the picture and the Amplus batteries havn't been used yet due to a change of plans, but do show that other sizes are available.

the Sony VTC6A's are wired in parallel to give me low voltage but high capacity, in this case 8000mAH

to do discharging if the 18650 cells through the 1 ohm resistor , this was the setup that I used.......and yes I was using a machine vice as a heatsink. I used mosfet and switch to start and stop the current, the voltage dropped though the wire and power connector was 0.3V, but the voltage dropped across the mosfet was 0.03V, so bear in mind that this will affect the load on the cell. the cell voltages were measured at the cell terminals. I later changed the wires and connector on the Sony 18650 cell to do the high current testing.

time in minutes	voltage of vapex VP18650F though 1ohm resistor	voltage of Sony VTC5A 18650 though 1ohm resistor	voltage of parallel Sony VTC6A 21700's though model hovercaft (approx 17amps current)	voltage of single Sony VTC5A 18650 though model hovercaft (approx 17amps current)
0	4.19	4.18	4.18	4.20
1	3.58	4.03	3.93	3.66
2	3.56	4.00	3.91	3.60
3	3.55	3.97	3.89	3.53
4	3.55	3.95	3.87	3.46
5	3.54	3.93	3.84	3.40
6	3.53	3.90	3.80	3.34
7	3.51	3.88	3.76	3.28
8	3.50	3.85	3.74	3.21
9	3.49	3.83	3.71	3.10
10	3.47	3.81	3.69
11	3.45	3.79	3.66
12	3.44	3.77	3.63
13	3.42	3.75	3.60
14	3.40	3.73	3.57
15	3.39	3.71	3.54
16	3.37	3.69	3.51
17	3.36	3.68	3.48
18	3.34	3.66	3.46
19	3.33	3.63	3.43
20	3.31	3.62	3.41
21	3.30	3.59	3.38
22	3.29	3.58	3.35
23	3.28	3.56	3.32
24	3.27	3.54	3.28
25	3.26	3.53	3.23
26	3.25	3.51	3.18
27	3.24	3.49
28	3.23	3.47
29	3.22	3.46
30	3.21	3.43
31	3.20	3.41
32		3.38
33		3.34
34		3.29
35		3.25
36		3.20
battery temperature after discharge	28C	20C	21C	35C
cell voltage overnight	3.65v	3.40v	3.41V	3.43V

this was all done to show that all 18650 batteries are not the same, for low current applications you'll be fine as long as they are decent. both of the 18650 batteries were of the same capacity, but approx 3.5A current draw the sony was in a different league in terms of performance. the output voltage of the sony was considerably higher ( 8 to 10% most of the time) than the vapex cell, and the sony battery had a longer duration to get down to 3.2V. some of the voltage drop may have been due to the protection on the cell, but the increase in temperature at the end of the testing would indicate the higher resistance in the battery. after the batteries had relaxed the voltage on the vapex was much higher than the sony, which indcates that more of the capacity of the cell is available to be used in the sony rather than the vapex. or while the batteries are the same capacity, more of it is available for use with the sony.

I did originally buy the ampex 26650 to use to power the hovercraft bit was worried about duration so was thinking of using that to power the direction (thrust fans) and an 18650 battery to power the lift fan and radio gear but have them as separate batteries. I then found that if they are decent quality cells you can hard wire them and use them in parallel which is why I got the 21700 cells , and can handle 60 amp continuous discharge current. and in electric cars these cells are used in series and parallel. it took me nearly years to work out what is meant by 1S 2S 3S 4S when referring to using batteries, the s stands for series, so the rest of the cells I have are 1S cells but these are 2P cells. so for larger battery packs the my be 4S6P in which case they are 4 lots of 6 cells in parallel and the 6 cells in parallel so all discharge and charge together, unlike the series charging when each cell is individually monitored for charging. The two 21700 cells in parellel give me plenty of duration for the model hovercraft.

as a last test I though I may as well test the sony 18650 though the hovercraft just to see how it performed under high load, and I think cant fault it, I was expecting it to get warmer, but the smaller temperature rise and relatively high output voltage would indicate that there is low internal resistance and the voltage increase after resting would also indicate that most of the capacity is available at high current draws (over 3 times the maximum of the vapex 18650 cell)

 

[Ruffian]

Havent seen a tanyo hovercraft in a long time.

They were epic fun. But a bit vintage now would probably be slightly brittle.

 

[eLuSiVeMiTe]

now for some of my ramblings about Lithium Ion Batteries, for most people any one will do, but because I use single cell voltages any voltage drop can make a difference to the performance of the models..

To power this hovercraft I decided to use Li-Ion (Lithium Ion) batteries rather than the more normal Li-Po (Lithium Polymer) batteries that are normally used for radio control applications. Its easy to get the two mixed up if you arnt too familiar with them and for most purposes they are interchangeable. the easy way to spot the difference is that the LI-ion batteries are cylindrical in shape and the Li-Po batteries are normally cuboid in shape. The Li-ion battery can normally be found in power tools and electric vehicles and the Li-Po batteries can be found in mobile phones.

the 18650 will be the most common form of the Li-ion battery, and that dictates its size e.g. 18mm diameter and 65mm long and these are the ones that I have got over the past couple of years (apart from the one that was in a model boat that sunk).

View attachment 325260

and they are from left to right

manufacturer/model	size	capacity	max discharge current	cell protection	model info
Amplus 14500	14500	1000mAH	10A	no	Ampsplus 14500 1000mAh 10A Battery Button Ampsplus 14500 1000mAh 10A 3.7V Battery ButtonMax. Continuos Discharge Current: 10A, Version: Button TopModel: A145001000HD10BT, Rechargeable BatteryBattery Designed for Torch, Light, Laser, Nerf, Vape, ModUK Brand, Tested and Certified, No memory effectSee more in Product Description. www.ampsplus.co.uk
Vapex VP18650F	18650	2600mAH	5A	yes	3.7V 2600mAh Li-ion 18650 Single Cell Battery ( Flat top) Vapex Dimensions: 68.1 mm long x 18.7mm diameter. Discharge: 5A Weight: 40g www.componentshop.co.uk
Sony VTC5A	18650	2600 mAH	25A	no	Sony/ Murata VTC5A - 18650 Battery 2600mAh - 25A Continuous Discharge - Flat TopOrder by 3pm (Monday to Friday) for same day dispatch!Brand: Sony/MurataModel: VTC5A (US18650VTC5A)Size: 18650Chemistry: NMCNominal Capacity: 2600mAhNominal Voltage: 3.6VDischarge: 25A Max Continuous (35A Max Continuous with a temperature limit of... www.18650.uk
Sony VTC6A	21700	4000mAH	30A	no	Sony/ Murata VTC6A - 21700 Battery 4000mAh - 30A Continuous Discharge - Flat TopOrder by 3pm (Monday to Friday) for same day dispatch!Brand: Sony/MurataModel: VTC6ASize: 21700Chemistry: IMRNominal Capacity: 4000mAhNominal Voltage: 3.6VDischarge: 30A Max ContinuousPositive: Flat TopProtected: NORechargeable: YesDimensions: 21.1mm... www.18650.uk
Amplus 26650	26650	5300mAH	20A	no	Ampsplus 26650 5300mAh 20A Battery Ampsplus 26650 5300mAh 3.7v Li-Ion 20A INR Rechargeable Battery / FlatVer. 2021, Free Zip case with each pair of batteriesHigh Capacity and High Drain battery designed for HID LED Torch, Flashlight, LightUK Brand, Tested, Fully UK / EU Battery Regulation & Compliant CellMay be used for Vaping... www.ampsplus.co.uk

there are two of the Sony VTC6A's in the picture and the Amplus batteries havn't been used yet due to a change of plans, but do show that other sizes are available.

the Sony VTC6A's are wired in parallel to give me low voltage but high capacity, in this case 8000mAH

View attachment 325270

to do discharging if the 18650 cells through the 1 ohm resistor , this was the setup that I used.......and yes I was using a machine vice as a heatsink. I used mosfet and switch to start and stop the current, the voltage dropped though the wire and power connector was 0.3V, but the voltage dropped across the mosfet was 0.03V, so bear in mind that this will affect the load on the cell. the cell voltages were measured at the cell terminals. I later changed the wires and connector on the Sony 18650 cell to do the high current testing.

View attachment 325279

time in minutes	voltage of vapex VP18650F though 1ohm resistor	voltage of Sony VTC5A 18650 though 1ohm resistor	voltage of parallel Sony VTC6A 21700's though model hovercaft (approx 17amps current)	voltage of single Sony VTC5A 18650 though model hovercaft (approx 17amps current)
0	4.19	4.18	4.18	4.20
1	3.58	4.03	3.93	3.66
2	3.56	4.00	3.91	3.60
3	3.55	3.97	3.89	3.53
4	3.55	3.95	3.87	3.46
5	3.54	3.93	3.84	3.40
6	3.53	3.90	3.80	3.34
7	3.51	3.88	3.76	3.28
8	3.50	3.85	3.74	3.21
9	3.49	3.83	3.71	3.10
10	3.47	3.81	3.69
11	3.45	3.79	3.66
12	3.44	3.77	3.63
13	3.42	3.75	3.60
14	3.40	3.73	3.57
15	3.39	3.71	3.54
16	3.37	3.69	3.51
17	3.36	3.68	3.48
18	3.34	3.66	3.46
19	3.33	3.63	3.43
20	3.31	3.62	3.41
21	3.30	3.59	3.38
22	3.29	3.58	3.35
23	3.28	3.56	3.32
24	3.27	3.54	3.28
25	3.26	3.53	3.23
26	3.25	3.51	3.18
27	3.24	3.49
28	3.23	3.47
29	3.22	3.46
30	3.21	3.43
31	3.20	3.41
32		3.38
33		3.34
34		3.29
35		3.25
36		3.20
battery temperature after discharge	28C	20C	21C	35C
cell voltage overnight	3.65v	3.40v	3.41V	3.43V

this was all done to show that all 18650 batteries are not the same, for low current applications you'll be fine as long as they are decent. both of the 18650 batteries were of the same capacity, but approx 3.5A current draw the sony was in a different league in terms of performance. the output voltage of the sony was considerably higher ( 8 to 10% most of the time) than the vapex cell, and the sony battery had a longer duration to get down to 3.2V. some of the voltage drop may have been due to the protection on the cell, but the increase in temperature at the end of the testing would indicate the higher resistance in the battery. after the batteries had relaxed the voltage on the vapex was much higher than the sony, which indcates that more of the capacity of the cell is available to be used in the sony rather than the vapex. or while the batteries are the same capacity, more of it is available for use with the sony.

I did originally buy the ampex 26650 to use to power the hovercraft bit was worried about duration so was thinking of using that to power the direction (thrust fans) and an 18650 battery to power the lift fan and radio gear but have them as separate batteries. I then found that if they are decent quality cells you can hard wire them and use them in parallel which is why I got the 21700 cells , and can handle 60 amp continuous discharge current. and in electric cars these cells are used in series and parallel. it took me nearly years to work out what is meant by 1S 2S 3S 4S when referring to using batteries, the s stands for series, so the rest of the cells I have are 1S cells but these are 2P cells. so for larger battery packs the my be 4S6P in which case they are 4 lots of 6 cells in parallel and the 6 cells in parallel so all discharge and charge together, unlike the series charging when each cell is individually monitored for charging. The two 21700 cells in parellel give me plenty of duration for the model hovercraft.

as a last test I though I may as well test the sony 18650 though the hovercraft just to see how it performed under high load, and I think cant fault it, I was expecting it to get warmer, but the smaller temperature rise and relatively high output voltage would indicate that there is low internal resistance and the voltage increase after resting would also indicate that most of the capacity is available at high current draws (over 3 times the maximum of the vapex 18650 cell)

Usually use either Sony vtc or Samsung IR in my vape sticks. Though the efests I've been using are great too. Compared to some cheaper offerings I tested recently they're night and day
Bought for a model that ended up coming with a set so tested on the vape. Specs on paper ShOUld Have BEeN GOod. EXCuSE CaPS PHONE iS GKitChINg

 

[eLuSiVeMiTe]

Any better now. That was odd. Alternating between caps and not each letter. :/

 

[Matchless]

I built a single seat hovercraft when I was around 12-13, so 55 years ago, Zundap Bella electric start engine for lift, lorry fan, washing machine drum for the shroud, polythene skirt held together with double sided tape, 1" x 1" wood frame covered with hardboard, it actually worked and lifted off the ground with me in it, I have a cutting from the Chingford Guardian somewhere, never got around to fitting the propulsion engine as the hardboard got wet one winter, and I discovered girls!

 

[winchman]

What an excellent project

 

[stuvy]

I had one of these when new it was crap on grass but great on the river, I lost it in the end!

 

[carbon]

All model hovercrafts a rubbish on grass as there is not a good enough surface to contain the air in the skirt, hard surfaces are much better.

 

[PhillipM]

If you segment the skirt they're a lot better but still not great.

I don't get why you went with 3.7v and the associated current losses over the usual 3s setup though?

 

[optima21]

I don't get why you went with 3.7v and the associated current losses over the usual 3s setup though?

because the rest of my r/c models are running on 3.7V, and that's part of the challenge, getting it all to work together and doing what you want.

as part of getting this model to work, I needed to use a tiny microswitch to operate the lift motor, but that are ok up to 1 amp current but Im needing nearly 4 amps, so it looked like mosfets were the best option to do the load switching

so this is probably as simple as electronics gets (other than wiring up an LED (with a resistor). the circuit above on the right is how it would be if you were using a switch (with RL being the thing you want to switch on, a motor in my case). the mosfet is on the circuit on the left hand side and to turn it on and off you can use a switch connected to Vin, and to turn the mosfet (and motor on) the switch is connect to VDD and to turn them off you connect them to OV, thats about it for simple switching, and can be used for electronic switching to replace a relay.

One issue that I have is that Im using very low voltages (down to 3.0V) which means that I need to be looking for "logic level" mosfets as many wont work. so after looking at data tables, I ordered 3 different ones to have a play with. they are shown below against a ruler showing mm divisons. even the small one on the right can handle 5 amps current (of so the spec says) but I havnt done anything with them as they seem to be a bit small to solder to. I decided to use the one in the middle, they are designed for surface mounting but the legs can be straightened out for soldering a wire to.

so the middle one is a IRLR8726PbF and you can get 10 of them off ebay for less than £3.00

https://www.infineon.com/dgdl/irlr8726pbf.pdf?fileId=5546d462533600a40153567181dd26f7

so the important things in the spec for me is that it will turn on VGS(th) at less than 2.0v and the resistance RDS(on) is when working is less than 0.01 ohms. Other parts of the spec are that they can work upto 20V and handle 50 amps continious current ( I'd like to see that current go through the legs though )

the hovercraft draws roughly 17 amps with the three motors running at full power, so I thought I'd try putting that power though one of the mosfets to see what would happen, it worked fine, but was dropping 0.198 volts which I wasnt happy about so tried again with two in parallel and that brought the voltage drop down to less than 0.1V. the photo below shows them on a battery connector, with the resistor to turn the mosfet on and was done just to measure the voltage drop.

so I'll be happy to use them for high current (on/off) switching in future. if you want to do high frequency switching there can be issues but its not something I'd be looking at doing. they can be used for slow speed switching though. for one of the models Im building the motors will have a current draw of 4 amps each, so there 3 speed controllers that are usable, the one on the left is one of my creations, the one in the middle is rated at 5 amps but at 4.1A current draw drops 0.61V across the speed controller (which is 15% power loss) so not idea. the one on the right is one that was used to operate the thrust motors on the hovercraft and drops 0.155v which is better but I have issued with size and weight (this also shows how 4 mosfets are required to do the forward/reverse switching)

the model that need to have a speed controller that can handle 4 amps only needs to work in one direction (reverse isnt required), so you only need to use 1 mosfet to to that. on my radio gear I like to have my throttle stick centred which means that the forward only speed controllers you can buy have the neutral position in the wrong place. you could butcher an old servo up and use the module from that, but you'd need to replace the position resistor with a couple of resistors, which I wasnt happy about but I found these modules on aliexpress (why is the search so bad on there)

2PCS Mini Electromagnetic Servo Drive Module 9mm Micro Receiver Electric Circuit Conversion Actuator Board 3-5V for RC Aircraft - AliExpress 26

Smarter Shopping, Better Living! Aliexpress.com

www.aliexpress.com

and just soldered a mosfet on to make a forward only speed controller and it works well and at 3.8amps current draw drops 0.04V. (compare that to the 0.6V dropped by the 5A forward/reverse speed controller). The module has an output of 10mA but the mosfet is driven by voltage rather than current so its not an issue and the output of the module is a square wave peak to peak.

and has a proportional output and pulsewidth from 10 to 90% and running at about 100Hz

so there you go, Mosfets can be fairly simple to use but have their place in low voltage, high current switching, you can use smaller switches and because of their efficiency may not need heat sinks and dont have relay contacts to arc and burn out.

 

[optima21]

and time for an update now that Ive had a play with the blue Taiyo one and a few tweeks, the yellow hovercraft made by Fuhai has been canabalised for parts and when you compare it to the Taiyo one is basically an inferior copy and the parts just do not feel to be of the same quality. The motors burn out after less than a minute when used on 12 volts ( was just trying to see if they would work on 3S Li-ion voltages) and the skirts while interchangeable the material in the taiyo is much better and they inflate better as the top and bottom of the skirts have a lap joint of a few mm rather than a butt joint on the Fuhai one.

the lift gained from the lift motor was marginal but this was increased by about 10% by removing some of the slates in the grill for the ait intake and shimming up the lift fan to close the gap the top of the fan impellor and the intake to reduce the intake of air that had already been though the fan. so it was better on the water but didn't like go backwards and on smooth surfaces it refused to go back wards at all. this turned out to be due to the weight distribution being slightly towards the rear. I added the weight on another 21700 Li-ion battery to the front, which then balanced it and it worked much better going backwards on smooth surfaces, but on water going forwards it had an issue that it it hit a big ripple on the lake the skirt at the front could deflate and almost stop the hovercraft dead. I guess this why the balance is to the rear as the nose will rise about the ripples (waves) and carry on going. Alos Ive fitted higher pitched thrust propellers now so it goes faster and on smooth water it can plane on the surface which allows it to go a bit faster, I think that will be helped by the air being trapped under the front of the skirt due to its shape and providing additional lift.

and part trying to improve the performance I used the Fuhai skirt by punching some holes in it to redirect the air all around the edge of the skirt. I started off at 5mm but then reduced it to 3mm by superglueing washers on the inside. On smooth surfaces it was much better but in water it the skirt was slightly less inflated (and for some reason Im thinking of Marilyn Monroe on a subway grate, must be inflated skirts )

I might try this again in water but need more air first, but as Im oinly playing with it on water the one without holes will be fitted

and here is a comparison between the new and old radio control electronics. (the are the same size its just the way I too the photo



on of the issues once the orginal circuit board was removed was how to turn the lift motor on and off. the original switch was a rotaty switch but had a helix on it that pressed a couple of contacts together. the easy answer (to keep the original switch knob was to fit a cam to the switch to operate a tiny microswich to power a mosfet to turn the motor off (and in an earlier post on here). the orignal one is on the left and the modified one on the right

so next thing to do is try and get some more air under the hovercraft, and for measuting air speed I got an anemometer as I thought it might get a bit akward playing with a pitot tube (ols school method of measuring velocity). show below is the original (yellow) fan on the left and a replacement axial fan on the right. in free air the axial fan can shift alot more air than the radial fan, but an restriction and the radial fan will then start to outflow the axial fan. Im simple terms, the axial fan shifts high volume low pressure air and the radial fan shift low volume high pressure air. shown below the fans is one of the thrust propeller motor and a spare fan motor, they are very similar in size and the thust motor could be modified to fit to produce more lift, but for a 35% increase in air velocity, the new motor would draw 7 amps instead of 2.7 amps, so thats not going to happen as it get to hot to hold in 3 minutes.

I've got another version of the lift motor on order, which may or may not work (Im looking to have a current draw of about 4amps max, I might try and rewind the lift motor, should be easy enough to to as the the stator wires are soldered in place rather then being crimped/welded. (but I would prefer to buy a suitable motor off the shelf first.

and while Im at it these are the fittings to fit the thrust propellers to their motors (fore scale the thread is M5 x 0.5mm), and the washer are 0.3mm thicka nd machined from brass bar.

so its now much better than the original, makes you wonder why they didnt make them like that in the first place

 

[optima21]

I waited for another lift motor which had a performance somewhere between the two I already had (on paper anyway) , but, I still wasnt happy with the amount of air pulled though the fan for the current drawn with the new one. then I had another think about the problem and realised that the issue wasn't the motors but was the fan itself as the air intake in the fan was causing a restriction and was in effect stalling the air going though the fan.

I ended up mounting the fan on a faceplate, the mounting hole for the fan was slightly off centre so I ended up clocking it up on the outer edge of the fan.|

this was then fastened to the faceplate and the centre of the fan was enlarged with a boring tool being used at a 20 degree angle, which increased the intake from 35mm dia to 50mm dia

and if you look at the intake it now looks better with the sloping fan blades.

and did it work any better? on the original motor that I used, its using less than 5% more power but shifted 35% more air (free air delivery) but in the hovercraft had an increased airflow of nearly 25% over standard, and now the planing action is better on water. now I think Ive finished reworking it

 

[stuvy]

Nice little result on the lift fan

 

[Johnnybravo]

I remember selling something similar in the model shop I worked for in the the 1980’s. Made by Nikko. Crazy power consumption and funnily enough had better performance on Duracell dry cells as opposed to Nicads. Guess it was the extra 0,3v per cell that drycells provided that made all the difference

 

[optima21]

I finally got round to playing with the small hovercraft that I've had for a year now,

I havnt seen another one on ebay for sale since, but I did find a couple of foreign videos on youtube like this one that translates that they are fit for the bin,

ohh well , it just goes to show that there is room for improvement. so as normally happens with these things they aren't planned, but they evolve, and the first issue I had was with the lift fan, as I couldn't remove it from the motor, so I chain drilled the centre out of the lifting fan, then bored the centre out

and made a new centre from styrene and abs

which would be superglued in place.

the next issue I had was with the motors. one quirk of my radio control models is that I run then all on single li-Ion or Li-Po cells (or if I need more power I run them in parallel rather than series, so they all work on a nominal 3.6/3.7V, which means that new motor are required, I couldn't get ones that were the same size as the original ones, so I had a go at rewinding them, and they were fine for a few minutes then the smoke escaped, so then it meant that I needed to fit the slightly larger motors that I used in the larger hovercraft above.

this meant boring out the motor mounting for the new larger diameter motor

and because of the motor being longer, there wasn't enough space to make a mounting bracket, so this was glued in place|, I thing using a milling machine to hold the motor in place while the glue dries should keep it accurately aligned for lifting fan

with the propulsion motor being longer, the end cap which held the motor in place wouldn't fit so I needed to make a longer one with a recess in it to accept the longer motor, and just think of the fun you guys with 3d printers miss out on doing this

so I laminated a couple of pieces of 3mm styrene together to make a piece 6mm thick and then co-ordinate drilled some holes in it, please not, if this was metal I wouldn't be using a end mill in a drill chuck, but for soft plastics I think its ok to do.

and then counterboring the recess bigger

and a then the outside needed a locating lip to be machined on it, so the cap was mounted on some MDF to hold it the 4 jaw chuck, and once again you can so this with soft plastic, metal would be done with a metal backing

and a bit of filing and the new one shown next to the old one

and here you can see it on the hovercraft, and the guards to stop you putting your fingers in the propeller have been removed, and the propeller is a cut down drone propeller like the ones used on the larger propeller but a 4 blade version instead of a 3 blade version.

so at least I had a useable lift motor and fan which could flow more air and the propulsion motor/propeller was fine too, (but it wont be breaking any speed records).

 

[optima21]

I decided to keep the original mechanism for operating the rudders as it was nice and simple but the "servo" part needed to be replaced, but this was easy to do using a mini servo and a small bracket, using the original mounting holes. I would have proportional control of the rudders, Im impressed with the simplicity of the original mechanism though as the rudders are spring loaded to be be the straight ahead position, and the motor one the original servo part has a clutch on it, , so get full left of full right rudder by changing the polarity of the motor, turn the motor off and it goes straight ahead again. and the new servo setup is less than half the weight of the old one.

at this stage it was time to think about how to power it and where the battery needs to go. I know that the lift motor used 2 amps and the propulsion motor uses 6 amps so I got a Samsung 50S 21700 Li-Ion battery as it has a 5Ah

Samsung 50S - 21700 Battery - 5000mAh - 35A

5000mAh - 35A Continuous Discharge - Flat Top/Button Top/TabsOrder by 3pm (Monday to Friday) for same day dispatch!Brand: SamsungModel: 50SSize: 21700Chemistry: INRNominal Capacity: 5000mAhNominal Voltage: 3.6VDischarge: 35A Max ContinuousPositive: Flat/Button Top/Tabs (please select)Protected...

www.nubattery.co.uk

and is only a few grams heavier than the original 700mAh 6V battery, but it woudn't fit in the original battery housing, so I had to make cut a bigger hole in the hovercraft body and make a new battery holder. balance on a hovercraft is pretty critical so the heavier weight of the new battery is slightly further back than the original one and a box to hold the electronics was under it too, a guess said I should be ok with the heavier battery (or else I would have used a 18650 sized battery and would have lived with lower capacity (and duration)

so next was fitting the electronics, and I use pretty small receivers, but the 20A forward/ reverse speed controllers are a bit larger, so I decided to not bother with reverse and use a tiny 1A speed controller to drive a mosfet (which can handle 20A), so with a bit of wiring and some heatshrink, you end up with this

one big issue with the hovercraft is that everything on (and in them) gets wet so the electronics need to be in a waterproof housing. I spent a while thinking about this as I wanted something that was simple to construct, light weight and waterproof, then I had one of those Eureka moments, and ended up using a 10CC syringe body as the housing, and could even use the part where the needle goes to put the receiver aerial so that it wasn't running with the power leads

and the inside of the hovercraft and now its ready to have the bottom put back on (and skirt), and I think this ended being a neat conversion as this wont be seen

and then its time to play, and I think that went pretty well, even though the water was a bit rough, but there is plenty of duration and it can still go into a headwind, which it may not have done with the original propulsion motor.

 

[optima21]

a few months ago I got an even smaller toy hovercraft that is supposed to look like a hoverspeed hovercraft and its the same as this one

now before this I was starting to play with air powered toy boats so got a tiny drone to play with, so once I started playing with tiny ducted fans this was no longer needed, so I had 4 small motors and 4 small propeller, so it would be rude not to do a conversion. the toy hoverspeed isnt really a hovercraft though as these isnt an inflatable skirt. so it'll just be an airboat pretending to be a hovercraft.
one of the big issues in making small boats is that weight is an issue so its time to get a dremel out and a few hours later you've removed a few grams of plastic, the bottom and top of the skirt are then glued together

so here is the motor and propeller that the toy came with on the right and the drone one on the right, the propeller are 30mm diameter and the black housing has been milled and turned from ones the drone, and the motors draw 1 amp at full power.

and add some electrics, I used two 2.7A speed controllers one one each side of the body (the receiver is in the middle). Each speed controller operates a couple of motors, and a 18650 battery.

after testing it was found that if this goes at full speed (faster than on the video) there is a bow wave and this will cover the skirt/hull on this, so I ended up reshaping the front so that it would try and ride over the bow wave (and the battery being so far back helps with this too)

and that worked better and stopped the submarining

and the completed conversion

and there you have it 3 toy radio controlled hovercraft, I think that's enough for now though.