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Tethered Spark?

Nuner83

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May 21, 2019
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40
Good Evening group.

I'm new to the forum as I just recently got into using the Spark at work. We've had it but only recently found a real use for it (we weren't looking very hard to use it for anything but fun tbh)

We've started inspecting the inside of large metal tanks/agitators with the drone. We've run into several issues. I think their might be some interference from all the metal, as well as the limited battery life.

One of the things I've been trying to look into is creating a tether system for the Spark. I was hoping something as simple as using the USB connector would allow me to maintain a charge but I get an issue the software preventing the Spark from taking off.

My second thought was gutting the battery and wiring in power that way so that the batter is still technically there but it isn't supplying the power.

Anyone have experience with doing either of these things?

Thanks!
 
I've flown a tethered sUAS (Inspire 1) and it was awesome but there are lots of limitations.

First one being the Spark doesn't have much "Reserve Power" to be able to lift the tether. It gets heavy quick carrying it's on umbilical cord.

IIRC the Tether for the Inspire did indeed have battery and line power in case the base unit lost power. It was a minimal amount of capacity but I was glad they did that because our generator ran out of juice and we were able to safely land it w/o the genny running.
 
We have a ready power supply so I shouldn't have to worry about losing power. My thought was that if I could eliminate the cells from the battery that should free up space for some lightweight power cables. I'm wondering if I could pop the cells out and hard wire a cable to those connection points.

I'm thinking I need to crack a batter case open and just give it a try.

The tanks I'm inspecting are only 30 feet tall so I think that the most I'd need to lift would be 30 ft. Worst case I would just need to maintain heighth, then I could work my way down the tank and use the tether to retrieve the drone at the bottom.

Thoughts?
 
We have a ready power supply so I shouldn't have to worry about losing power. My thought was that if I could eliminate the cells from the battery that should free up space for some lightweight power cables. I'm wondering if I could pop the cells out and hard wire a cable to those connection points.

I'm thinking I need to crack a batter case open and just give it a try.

The tanks I'm inspecting are only 30 feet tall so I think that the most I'd need to lift would be 30 ft. Worst case I would just need to maintain heighth, then I could work my way down the tank and use the tether to retrieve the drone at the bottom.

Thoughts?
 
Since one of your chief concerns is limited battery life, my thoughts are that you should ditch the limited battery life Spark and invest in one of the Mavics with nearly double the battery life. Or, am I being overly simplistic?
 
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A couple issues there. I have some size constraints that make the Spark preferable. I am trying to enter the tank from a small access point at the top of the tank. These are food processing tanks that require hours of additional cleaning, sanitizing etc is anything contacts a surface. I say that because I haven't figured out a way to lower the drone into the tank and take off and recover it safely. If I were able to I would feel more confident about fitting the larger Mavic through the opening instead of flying it through. If I can make a tether work I can sanitize it separately and give myself unlimited time to do a thorough inspection

The second issue is I've beat the heck out of the spark trying to get it to work for this application. The cost of replacing the Spark is a lot less painful than if i destroyed a Mavic. I've been looking for better guards for either the Spark or the Mavic to minimize these issues but at this point I think I may have to 3D print my own. I purchased blade guards, and a simple top guard from PGYTECH and it last all of 1 flight before utterly destroying it self. Far from satisfied with that order.

But the most important reason why I don't just upgrade is I can't get approval for it until I can prove that we can actually pull off consistent reliable inspections with a drone.
 
I'm thinking I need to crack a batter case open and just give it a try.

Here is a thread from a while back about a dual battery modification.
Post #18 shows pictures.

Here's a link provided for the mod.

Maybe this is something that you can use without sacrificing a battery.

I assume the metal tanks are steel and that may cause magnetic interference that will affect the performance of the Spark.


Edit: I just read they are food grade, so probably stainless steel and you shouldn't have a magnetic error.


Here's an idea, use a helium balloon suspend a GoPro or a 360* camera and record the footage, that way you won't have any interference.

Before drones, photographers would use a balloon to shoot pictures of clock towers, etc.

With a few pieces of string hanging from the ballon so that you and a co worker may be able to guide the balloon where you need it?
 
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We have a ready power supply so I shouldn't have to worry about losing power. My thought was that if I could eliminate the cells from the battery that should free up space for some lightweight power cables. I'm wondering if I could pop the cells out and hard wire a cable to those connection points.

I'm thinking I need to crack a batter case open and just give it a try.

The tanks I'm inspecting are only 30 feet tall so I think that the most I'd need to lift would be 30 ft. Worst case I would just need to maintain heighth, then I could work my way down the tank and use the tether to retrieve the drone at the bottom.

Thoughts?
I think you have a whole lot of issues to contend with here:
  • As Al mentioned already, the Spark has very little excess power to support any sort of payload. Even a light tether might be too much.
  • You said the entry port is at the top of the tank. As such the tether would be coming down from the top of the Spark ,which can/may/will at some point catch one of the props and cause a big problem.
  • If the tank is magnetic then the Spark compass will go crazy.
  • How will you light the inside of the tank sufficiently to get good quality video/pictures?
  • You can't just run power leads to the battery contacts because the FC communicates with the battery circuitry. Without a smart battery there, the drone will most likely not even let you power up.
This can't possibly be a unique problem in your industry. How are companies doing inspections now? Has no one found a solution like this?
 
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Why not just lower a Gopro/ DJI action cam with a custom control frame?

Indeed, a long extendable pole and simply lower it down, additional lighting if needed (?) could be done same way attached to pole above camera.
A mentioned, top access point won't work well with any sort of tether.
The whole drone thing inside a tank is simply risky, almost going to crash at some point in time.
 
@Nuner83 I fully understand and respect your genuine desire to make this specific project work. I really do and I've been there.

Sometimes our desires override our view of reality. The reality of this situation is most likely that this isn't the right TOOL for this specific job. While it's possible you could "eventually" get a half way satisfactory final product you've got to ask yourself if it's practical and worth the extra time and effort to end up with a "marginal" final product.

There are aircraft specifically suited for "Internal Inspections" but unfortunately they are priced well above what most companies find "acceptable". The market leader (IMHO) is this one:
 
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Just an update

I've already completed several tank inspections. the compass handled the tank just fine. Other companies do these kind of inspections only with more expensive rigs.

I've torn the batter apart, found that the "smart" circuitry has 3 batteries plugged into it, each 3.8 volts. I'll simulate the same thing with a lead that connects in the same point. All the parts are coming in this weekend so I'll solder the leads in with the DC power source and give an update on what happens then.

The tether will go from the top of the tank and then back up to the lid so that when the drone flies down into the tank the lead will be handing underneath. Because of the position of the access port I should be able to keep the tether out of the way of the drone, even if it does get in the way I have the blade guards on as well as an aftermarket lighting it which has done very well at lighting the areas I am trying to inspect/photograph. I'll be 3D printing a sturdier guard here soon. I'll update on the progress there as well.

So far removing the batteries has substantially lightened the weight of the drone overall. I'll compare the untouched battery and the gutted one tomorrow so I can show the comparison.

Also, because of the large agitator inside the tanks, and the need to view all sides of the tank and the internal agitator as well as several internal pipes and structures, lowering a pole or a balloon won't provide an adequate inspection to eliminate putting people in a potential confined space.

My hope with the tether is 2 fold, 1 it gives me more time to complete the inspection and 2 it gives me a means of retrieving the drone if it crashed. Either way I won't know how it works till I try it. If it doesn't worked, I've at least gotten plenty of practice time in and I've torn the drone down enough to now exactly how it works. Best case I save nearly 24 hrs of production time each time we inspect a tank.

I appreciate all the feedback I've received so far.
 
@BigAl07 I appreciate your response. I've looked into Flyability and they do have a great drone but the big improvements they have made have more to do with having to inspect internal structures that are far more complex that what I am doing.(large lighting, wifi boosters, full guarding and a gimbal type guard attachment) Basically I'm dropping down into a big tank, doing some sweeps around it while trying to avoid a shaft and some blades in the center. I've already completed several trial inspections using the basic spark, no corded connections to the remote, no upgrade to the wifi, and no modifications to the Spark short of some blade guards, so I already know its possible. At this point I'm working through a list of potential improvements and seeing what works and what doesn't I've already. I'll try to add some of the pics I've already taken of my test runs. They were done on a decommissioned tank to maintain food safety so don't be worried when you see the rust and less than edible bits haha.
 

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@Nuner83 I fully understand and respect your genuine desire to make this specific project work. I really do and I've been there.

Sometimes our desires override our view of reality. The reality of this situation is most likely that this isn't the right TOOL for this specific job. While it's possible you could "eventually" get a half way satisfactory final product you've got to ask yourself if it's practical and worth the extra time and effort to end up with a "marginal" final product.

There are aircraft specifically suited for "Internal Inspections" but unfortunately they are priced well above what most companies find "acceptable". The market leader (IMHO) is this one:

I must agree that a drone is not the right tool after reviewing his description of the task:

"Small access opening...
Of a food processing system..
For wall inspection...
While avoiding the central shaft"

Sounds like a colonoscopy to me ?
 
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Update: my untouched, charged battery weighs 98 grams. My battery case with just the control board weighs 21grams. This gives me 78 grams to play with without increasing the weight of my Spark.

The heaviest 20 gauge wire I could find was spec'd at 3.71 lbs/1000 ft. Breaking this down to grams/ft I come out to right around 1.68 g/ft.

With 78 grams to play with and requiring 2 lines in the tether, that should give me at least 23 ft of 20 gauge wire I can lift with the Spark.
 
Sounds like you're well on your way. I look forward to hearing your results and hope it''s a GREAT outcome!
 
We have a ready power supply so I shouldn't have to worry about losing power. My thought was that if I could eliminate the cells from the battery that should free up space for some lightweight power cables. I'm wondering if I could pop the cells out and hard wire a cable to those connection points.

I'm thinking I need to crack a batter case open and just give it a try.

The tanks I'm inspecting are only 30 feet tall so I think that the most I'd need to lift would be 30 ft. Worst case I would just need to maintain heighth, then I could work my way down the tank and use the tether to retrieve the drone at the bottom.

Thoughts?

Sounds like a crazy application/idea, but...

Your tether will have to use wire that is thick enough to have sufficiently low resistance and current carrying capacity to power the drone. Google LiPo batteries for RC fixed-wing and multi-rotor aircraft. The leads on these batteries are short and thick for a reason (hint: lower resistance/heat and higher current capacity). In general, the thinner and lighter the wire, the higher the resistance and voltage drop per foot, and the lower the current carrying capacity. The higher the resistance the hotter the wire gets at a given voltage/current. Finding the right thickness of wire is easy enough if you know the power requirements of the drone and use the right formulas for estimating voltage drop etc. of the wire - basic Physics/electrical engineering.

Don’t plan to feed the wire from a multi-layer spool since the layered coils may heat up enough to melt the insulation on the wire.

I solved these problems many years ago when I built still and video cameras for inspecting mines thru boreholes, and the bottoms of 100-ft deep caisson foundations. I designed and built an adjustable AC power supply that let me send relatively high AC voltage down a relatively thin wire to the camera(s). I equipped the camera(s) with an onboard step-down power supply to power the electronics. However, my application required much lower current than a drone.

The drone’s gyro stabilization system will likely have to do extra work counteracting external forces applied from the wiggling tether. At a minimum, this will draw more current at hover vs. a self-contained battery powered drone. At worse, the drone will crash.

You may be able to estimate the lifting capacity of the drone by tethering it with some string to a suitable weight placed on a digital scale and seeing how much the measured weight diminishes at full throttle. Make the string long enough that the drone isn’t in ground effect. Hopefully the drone doesn’t crash trying to counteract the force from the tether. If you know the lifting capacity of the drone and the weight of the wire per foot, you can estimate how much thick, heavy, high-current-capacity wire the drone can lift.

Somebody probably makes a suitable drone for this application. Google “indoor inspection drone” and see what you get.

Good luck!
 

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