Kickstarter and Indiegogo are great for finding out where the hype is these days.

Drones are at the top of the hype curve it seems.

Indiegogo is hosting another quadcopter: the Plexidrone. It has raised more than $300,000 as of this writing.

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While all the famous blogs are gushing over this thing (or at least, have made a very quotable quote or two), it bears looking into the specifications a bit more.  As with all pre-prototype, crowdfunded ideas, the wish-list is easy to make before the realities of economics and physics set in. As one friend of mine used to say jokingly, “No one can deliver what we can promise”.

I guess this quote, while at first blush sounds like a compliment, sounds a bit also like a warning: “If there was a list of features we wanted on a ready-to-fly drone, it might well read like PlexiDrone’s spec-sheet” – James Trew, Engadget

In other words, out of the hundreds of quadcopters that you can buy or build these days, if it was easy or possible to have all of these features, wouldn’t someone have done it already?

A couple of warning signals that I see:

1. the flight time – this is one of the golden specifications of any aircraft – how long can it fly? The Plexidrone people are claiming 35 minutes. Whoa! That’s a long time. The Phantom 1 flies for 5-10 minutes. The DJI Phantom 2 flies for 20-25 minutes.

If you look at the specifications of this very expensive motor ($200 per motor) that you can use as an after-market modification for a DJI phantom, you can see that – and this is a very expensive, very good motor – the ones in the plexidrone will definitely be worse than this –

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So, for this “expensive ideal” motor, look at the Throttle and Amps columns. At 75% throttle, we are looking at around 5 amps of draw per motor. Let’s plug this into a handy flight time calculator (5000 mAh, 20A average amp draw) and we get 15 minutes of flight time.

The only way to get 35 minutes of flight time would be to use only 50% throttle with these (again, very expensive and not the type that is going to be used on the plexidrone) motors with 10 inch carbon fiber propellers – again, almost certainly not going to be used on the Plexidrone.

2. This Plexidrone weighs 1.3Kg; it has a 5000mAh battery – that’s around 410 grams. All the other parts therefore need to weigh 890 grams. The motors will weigh (at minimum) 100g each, so that’s 490 grams left over for everything else – the frame, the shell, the screws, electronics, and so on. This just does not seem realistic.

 

3. The flight controller. On the Indiegogo page, they state

What flight controller does the PlexiDrone use?
The PlexiDrone uses DreamQii’s custom electronics and software. We do not use any off-the-shelf options.”

Considering all of the features – including the dead giveaway – the “follow me” function – which is only available on Pixhawk controllers – it is obvious that the Plexidrone is using the Pixhawk controller. OK, Pixhawk is open-source. So they are using a Pixhawk clone. I guess it is still not flat-out lying to say that they are using “DreamQii’s custom electronics and software” but come on – it’s just a bit slightly un-truthy, isn’t it?

It’s hard to build a new flight controller – No one will think less of this company if they say that they have not built their own flight controller hardware/software from scratch.

It is hard to be one of the only naysayers around here willing to write a blog post that is not all rah-rah and spewing only positive thoughts…. but this quadcopter, as it is advertised, seems to be making some unrealistic claims. I hope these claims can be addressed and solved and that the people who back this project are not too unhappy when some of these specs slide downwards a bit back into reality.

 

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