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Tow-behind tethered quad?

slyp823

crash test dummy
#1
I've recently taken up motorcycling (HUGE fun, btw), and have been trying to think of new and strange ways to shoot video or photo-every-[interval] outside of the normal "stick the gopro to the helmet"/"stick the gopro to the bike," and recently I came across the idea of a tethered multirotor. Most that I've seen are either remote-powered (tether also is a power cable) for longer flights or area surveillance, or are roughly the size of a Mavic Air and carry their own power source, but are tethered more for perception than anything else (don't have to ask "who's flying that drone?" when all you have to do is follow the tether down to the person holding it"). This gave me the idea of making a relatively small (maybe 250 size?) remote-powered multirotor, and put a tether (likely high test fishing line, either a single strand or braided) either on the tail section of the bike, or on something like a GoPro Chesty mount worn backwards. The bike has a battery tender lead installed, so having a constant ~14v isn't an issue. My main concern is how to control it, specifically how to get it to decelerate at least as fast (preferably faster) than the bike. Distance behind the bike and altitude should be mostly a factor of the length tether I use, so that I'm less worried about, same with yaw (a vertical stabilizer fin would do wonders for that). One idea that comes to mind is to have a small (or small pair) of EDFs aimed directly forward, let the quad literally try to pull itself backwards against the tether, but I worry about how much current that could end up drawing as the EDF could end up working against at least 100mph of wind, and I can't imagine they are designed around. The thought of angling the 4 thrust motors back slightly (similar idea to how racing quads angle the camera way up so that it is level during forward flight, just backwards) also comes to mind, but again, I don't know how nicely the motors would take to being essentially thrown into a wind tunnel and asked to maintain level flight. My biggest concern is not getting clocked in the back of the helmet with my own multirotor, should I have to panic stop. Anyone have any thoughts?
 

ElectriSean

Eternal Student
Mentor
#2
Interesting idea for filming, though I wouldn't use a multirotor for it... You can only run at full tilt for a very short time before your battery is toast, and control would be sketchy at best. A fixed wing could be treated as a kite though, it provides its own lift and could go for as long as you have gas in the bike.
 

slyp823

crash test dummy
#3
Interesting idea for filming, though I wouldn't use a multirotor for it... You can only run at full tilt for a very short time before your battery is toast, and control would be sketchy at best. A fixed wing could be treated as a kite though, it provides its own lift and could go for as long as you have gas in the bike.
My thought was to literally run a power cable from my bike’s SAE Battery Tender connector, run it along the tether, so that the quad was powered by the bike’s battery and charging system, rather than from having to carry its own battery onboard. I do like the idea of a fixed wing for simplicity and control authority, but they tend to have a hard time generating lift at 0mph, which unfortunately is a speed motorcycles sometimes have to go. Maybe blend the two, make an aero cover for the multirotor and integrate a decent size vertical and horizontal fin to help with pitch and yaw at speed?
 

PsyBorg

Wake up! Time to fly!
#4
Ok time for a grampa bill moment..

If you are planning this for open road use... just plain dont. There are sooooo many safety rules you would be breaking not to mention laws.

Worse yet you are risking other peoples lives to do something like that. You MAY be lucky to devise a working system but you would be a rolling distracted driving magnet.

Its bad enough people dont really look for bikes but to have a flying object behind it...

Just a bad and not really thought thru idea my friend.

Sorry for being blunt. Just dont be "THAT GUY"
 

d8veh

Well-known member
#5
I'll make it easier. It won't work. Put a camera on a long selfie stick instead, and make sure it's tied on tightly!

Some drones have a follow me function, which is great if you're walking around, but I doubt that it'll work on a motorbike. Whayt if a similar bike comes the other way? I know the Gadget Show in UK tried one for some sports activity, but it wasn't a success, though they're getting better all the time.
 

slyp823

crash test dummy
#6
I'll make it easier. It won't work. Put a camera on a long selfie stick instead, and make sure it's tied on tightly!

Some drones have a follow me function, which is great if you're walking around, but I doubt that it'll work on a motorbike. Whayt if a similar bike comes the other way? I know the Gadget Show in UK tried one for some sports activity, but it wasn't a success, though they're getting better all the time.
That’s what the physical tether is for ;) I’m nowhere near programmer enough to write my own “follow me” code, but given my plan to have the quad receive wired power from the bike (it can stay in the air as long as the bike’s battery has enough voltage to start the bike), doing a brute force hardware solution (it won’t follow the bike? “LOL IT WILL NOW.”) to what’s normally a software problem seems like the most appropriate thing.

Given the tethered nature of the multirotor, I’m not even 100% sure I would need an actual radio, if just a simple servo tester in place of the throttle channel to control altitude, and some sort of a brake function (air brake? small ducted fan aimed forward? Accelerometer on the bike tied to the pitch channel?) to help the quad slow at/near the same rate the bike does

I understand that y’all have concerns about the safety of this, but I’m hoping that the fact that it is literally tethered to the bike/rider will alleviate some of the concerns, and my plan to use propeller shrouds (picture a tiny whoop, scaled up to about 200-250 size) will alleviate the rest.

If it helps, imagine the multirotor equivalent of a control line plane, except instead of going in circles, it just follows the bike like an eager puppy on a leash
 

CarolineTyler

Well-known member
#7
Even better - get an Instax360 One X - put it at the end of a selfie stick and the stick 'disappears' - you can edit the video in post to display at any angle and viewpoint - awesome effect!!!
Check this out!!! and This!
All the fun of a flying camera behind you - much less risk
 

d8veh

Well-known member
#8
Without programming skills, you have zero chance. Even if you could get someone else with sufficient skill and knowledge, you most likely won't be able to get enough power to it. You'd need really thick wires to get the current up to the drone without a massive voltage drop. You have Ohm's law to blame for that. As an example, you lose 1v for every meter of twin core wire with copper conductors 1mm squared, assuming 30A current, so a 20ft tether would drop the voltage at the drone from 14v to 8v. You'd need 4mm square copper in each conductor to get the drop less than 2v. That wire would most likely be too heavy for the drone to lift.

Have you already got a camera drone. If not, get one to see how it works. You'll soon discover its limitations.

It's a great idea. I hate to discourage you, but to realise your dream, there is no ready-made solution, so you need skill, knowledge, understanding and experimentation to get there. It could be a long journey. Maybe you should contact this guy to see if he thinks what you want is feasible. He seems to be able to do miracles with drones:
https://forum.flitetest.com/index.p...tilt-fan-concept-flying-jet-motorcycle.53724/

If you're serious about this project, here's what I'd suggest: Get a drone (check out Rcsaylors Youtube channel for the best one), then do some tests to see whether it can fly whilst carrying some cable. See how much cable it can lift. See how fast it can go whilst dragging the cable behind it. See what happens when you pull the cable. If it doesn't work out, at least you have the fun of the experimentation and flying the drone.
 
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Merv

Well-known member
#9
I must agree with @PsyBorg, too many things to go wrong. Even if it is possible to do, your tether could easily become tangled in a prop. Or snagged by a power line, overpass, tree branch or anything else that crosses the road.

Might be safer and more practical to just have a buddy film you from another vehicle. Like this guy did.
 
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sprzout

Knower of useless information
Mentor
#10
I must agree with @PsyBorg, too many things to go wrong. Even if it is possible to do, your tether could easily become tangled in a prop. Or snagged by a power line, overpass, tree branch or anything else that crosses the road.

Might be safer and more practical to just have a buddy film you from another vehicle. Like they this guy did.
I'll agree with this - too many things to go wrong. You make a right turn, the drone slides out and tangles in the oversized mirror arm of the semi in the lane going straight, right as he goes. Your tether is more than likely going to pull you in that direction, and all of a sudden you're cartwheeling over the handlebars.

Or there's catching it on a light pole/yard arm as you go under, and you get yanked off. Or, worse, you don't get yanked off but instead the cable breaks and you've got a bunch of sparking and a whirling blender that's continuing forward and dropping in a parabolic arc - right towards your back.

i'm sorry, this just seems REALLY, REALLY dangerous.
 

ElectriSean

Eternal Student
Mentor
#11
I had assumed the OP would be doing this on a closed track, not on the street... Even a relatively light 250mm drone weighs a pound, I wouldn't want that landing on my car let alone colliding with it. Prop guards are not going to keep it from coming through the windshield :p

Volt drop aside, your bikes charging system would not be able to keep up with the current consumption of a multirotor even cruising around, let alone at 100mph.