Crowdfund A Collapsible RC Tricopter

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It looks a bit like Anakin Skywalker's starfighter from The Phantom Menace.

 

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  • Thanks John!  

  • For the price, I think the DT series motors are some of the best choices for multirotors.  They are super efficient, they run cool, you can blow any debris out of them without taking them apart and you can lock the props on with nuts/lock-nuts.  It's the bearings that give them a bad name.  But if you lower the motor shaft (plenty available) you can add a thrust bearing to the bottom and transfer the entire load to the motor casing and off the inner race of the bottom radial bearing.  You would have to modify your airframe to accomodate the extra bearing sticking out the bottom.  DT7500 requires a 4x3x4mm thrust bearing.  $3.  You will end up with the most reliable motor available (IMO).  Okay, I gave that one to you for free.  ;)

  • I will say that it appears that you are honest regarding the performance of your aircraft and your selling price is accurate for a low rate commercial production; it's high and that is likely why we don't see other multirotors for sale made in a similar style.  There is more profit in selling a million pieces of cheap crap than a few quality items at a fair price.  And like I ended my last post, "I would love to fly one".  I wish you luck.

  • @ Brent

     

    -I may change some of the low stress hardware to nylon, been looking into that recently.   I didn't use carbon to keep the costs down.

     

    @ healthyfatboy

     

    -The costs are high on the initial run; they will decrease rapidly as manufactured part quantities increase, just a hump that must be overcome.

     

    -You make a valid point about aluminum, and at some point if the costs can be controlled the arms will likely be upgraded to carbon.  The idea was to make a professional rig quality without the $5000+ price tag most of the pro-filming platforms are charging.

     

    -The replacement parts will be very reasonable once the part volumes increase.

     

    -Thanks for the encouragement.

     

     

    @John Johnson

     

    -I suspect the people in the hobby are like-you-say the kind that is going to build their own, they (like both you and I, I imagine) enjoy the build/tuning/design process.  RC helis have been historically a niche, even within the RC world to some extent due to their expense and difficulty to fly.  I was hoping to attract a new wave of people, that may not share the same desires for building we do.  You make a fair point that the expectation may not be where it is regarding piloting skill and tuning, I’ll do my best to help make this clear through the training videos and making the default setup with as soft and wide an operational window as possible.

     

    -Regarding the weight; “unnecessary” is a subjective term.  If I was making a purely performance based rig, it would be smaller, wood, have no skids and have all that money put into a 6S drive system.  However, not everyone cares about that extra flight time, forward speed or climb rate.  Some care about aesthetics and ease of use.  If the world only cared about performance, cars wouldn’t have radios, power windows, cup holders or A/C.  Granted I would prefer a world like this, but it’s not the one we live in and a balance must be struck.   My hope is that the balance I’ve chosen is good enough to appeal to wider demographic of folk than do designs like that of TBS or DJI.

     

    -I’ve read about the DT bearing issue and endurance tested my DT1000’s for a continuous 10hr non-stop test at 110% of the thrust required to maintain a hover at max payload without any problems.  That said, the DTs are not my favorite motor and I will likely change them for the ones I’m testing now across the board with no additional cost to the Kickstarter backers.

     

     

    @Quadzimodo

     

    -I greatly admire what the Flight Test guys have done with their designs.  If I was building one for myself alone it would be much closer to their designs, again back to my comment above… trying to appeal to a wider group with the current design.

     

    -No worries about the whiteboard… 

     

    -Thanks for the kind words… regarding your car analogy, my hope was to produce a Honda S2000.  Maybe not the highest performance, but decent with some good looks, practicality and the ability to be upgraded in the future.  I have a feeling once I can show the version with the upgraded drive system there might a bit more love for it :)

     

     

    I actually tried to post some info on DIY before the PopSci article came out trying to get the opinions of people who know what they’re talking about… but it got pulled for spamming.  I’m guessing because I was new to the forum and it included a link to the website.  I sincerely appreciate all of your time and suggestions, I take them to heart.  

  • 3.7V and 4700ft is way different to me.  I am at 54m (That's 177ft for any Burmese, Liberians or Americans reading this thread) and I run down to 3.3V per cell.  Our testing conditions almost could not be more different, and it stands to reason that the Switchblade could achieve noticeably higher performance in my neck of the woods than it does in yours.

     

    Regarding weight, having observed the development process made clear on your kickstarter project page, I can empathise with the process you must have gone through making the transition from wood (something that is incredibly great performance wise, but not very good in terms of integration of electronics, ergonomics, form factor, aesthetic appeal, uniqueness and marketability) too... well... something, anything other than wood which is capable of supporting development on the basic geometry and allowing great improvements in terms of component integration, ergonomics, form factor, aesthetic appeal, uniqueness and marketability.

     

    I would argue that you have departed from a pre-established "right" way of distributing weight.  In fact, the only guys I am aware of who are building multirotors which do seem to me to properly maximise the ratio between (please excuse my use of improper terms) "sprung" and "unsprung" weight are David Windestål, Josh Bixler and Josh Scott.  Notably, their coolest tri designs are wooden.

     

    Regarding chassis, Aerospace Engineering is a fine art, and balance is everything.  If the chassis is over engineered for the selected components, then the chassis is over engineered for the selected components.  This makes sense in a way, as it offers great upgradability.  But this USP is not emphasised on your project page, and thus is little more than added value to your customers. Down-sizing or changing the frame stock yet retaining the existing design and features (such as the field configurable payload plate and the folding mechanism) may be impossible, while upsizing components to better utilise the attributes of the frame may destroy your finances. But, while I haven't done the math... even with an upgrade to bigger motors and battery, it seems extremely unlikely that you will need to increase the size of your rather oversized 45A ESCs. Also to be considered is the fact that any deviation from your currently resolved configuration may bring with it the need for other changes and modifications (prop size, arm length, etc).

     

    Regarding whiteboard, my apologies.

     

    Honestly, the Switchblade is a beautifully engineered bit of kit and, while it does integrate a number of elements which many would consider to be unnecessary or even misguided indulgences, the thing does fly. It obviously flies well and anyone who buys one of these preassembled kits (and is technically savvy enough not to render it in a non user serviceable condition) will at least be afforded the chance to enjoy something I have yet to achieve - stable video footage.

     

    As has been discussed here, the people who purchase the Switchblade will not be looking for their next multirotor, they will be looking for their first. Plus, they will probably not be geeks like us, and have no interest in investing 100s of hours absorbing forum threads, crunching numbers with ecalc, building technical knowledge and honing every last gram of weight or thrust or second of flight out of an airframe. However, they could be forgiven for expecting that you have done that for them in this instance.

     

    While what you have produced is not what I would produce today and in your shoes, that does not mean that what you've produced is not relevant, or even a little bit sexy. I like cars and don't particularly see the value or appeal or quality that others see in Alfa Romeos. I drive a stock white VW GTi which I adore, but to an Alfa buyer it is just another boring bland hatch not worth a second look.

     

    Simplifying problems and creating different solutions in order to allow a product to appeal to a broader market of consumers is what development is all about. Looking at it from this point of view, I greatly admire what you've done and am perhaps maybe even a little envious or even jealous of what you have achieved.

     

    While some frank criticisms have been levelled at a few of the decisions you have made in this thread, there are also a few good suggestions here. Thanks to the relatively small quantity of customers you will be dealing with coupled with the flexibility of the kickstarter system, many of these can be overcome should they be worthy of attention.  It also must be said that you are at no risk of under specing (or cheaping out) on the components you have selected.  It seems reasonable to assume that there is still time to better balance frame and drivetrain, and enough capital already allocated to selected components to meet this goal.

     

    My hat goes off to you!

  • Brent helped me get my first tricopter flying, I don't know how many years ago but it seems like ages.  After I got my first one working well I put it on a diet and removed .25 pounds of unnecessary weight from the airframe.  From that learning experience, I went on a journey in search of a lighter airframe.  In the end, I produced the Creep 1.0 tricopter which at the time (before we were stealing parts from Wii controllers to make autopilots) was the only available fully stabilized multicopter and I sold them for $650 (with precision laser cut parts).  I have carried a GoPro with it.  I have flown it for 24 minutes.  It used consumer grade electronic components which didn't require a computer to tune the gains if they changed locations (altitude above sea level).

    Shane, my point is that I think you are selling your consumer targeted wares before they are ready.  It's too heavy.  It's appears to be over-engineered in some areas and under-engineered in others.  Here is a short list of items that I would address if I were in your shoes:

    -The people that know what they are doing in this hobby know better than to pay your prices and they would rather build their own for 30% the cost.  So that means that your customers don't understand what they are getting into and you are offering them low rate production items with open source development autopilots and not consumer level products.  

    -What altitude will you tune these for?  If you tune them for sea level and ship them to someone who lives thousands of feet higher, then they will have to re-tune them to fly properly.  Same if they live at high altitude and take it to a low altitude location.  That means that they require a computer, FTDI and the knowledge to use the software.  I didn't see that info in your Kickstarter.  I live at 5k' and had to re-tune every time I went back and forth to the west coast.

    -You have too much unnecessary weight for the sake of making things look pretty (landing skid).  Drop unnecessary weight.  If you use nylon hardware it will reduce weight and in a crash stuff like motors will break away instead of bending a motor shaft (unless you are in the biz of selling $50 DT1000 motors).

    -Speaking of Hextronic motors, they are infamous when it comes to bearing failures.  The bottom radial bearing of each motor carries 33% of the aircraft weight on the inner race of the radial bearing.  Did you catch that?  You have over 1 pound of side load on the inner race of a radial bearing.  You are a smart guy, so what is going to happen to that bearing?  There is a mod for this issue which eliminates this issue and increases efficiency by about 15% with these Hextronic DT motors (but this info is not free).

    -What's with all the vibration dampening material?  I guess it's a good choice for an off the shelf (like) product to eliminate the need for the customer to balance propellers (and understand why it's important).  But all that foam rubber add complexity to the airframe.  I, and many others, have proven repeatedly that dynamically balanced propellers is better than vibration isolation.  But NEVER isolate the battery from vibrations.  It is a big chunk of mass that will dampen those pesky vibrations.

    -acrylic is going to crack.  use ABS.

    In hind sight, your pricing is probably right on target because after you ship the 30 tricopters that are spoken for as of now you are going to be spending a lot of time answering questions from your customers who just want something that works as easy as your video makes it look.  All that time has to be paid for somehow so might as well charge up front.

    In summary, sweet airframe and I would love to fly one.  But those who appreciate it know the challenges that come with it and the skills needed to fly and maintain it.  Those who are buying it are likely in for a rude awakening and a bad consumer experience.

  • T3

    Good to hear a response from the creator of the project.

    I agree that the KK2.0 is a great, inexpensive board and the APM even better. I guess for a RTF product, it may be worth the cost to some people who can't or don't know how to follow instructions. Of course, those people are generally going to be those that are less experienced at flying too and will have some accidents fairly quickly. With metal, it's going to bend on harder impacts and for the buyer, it'll be quite the expensive accident. As the seller, that can be beneficial but it'll be hard to maintain any support from people if you price yourself out of people's budget.

    If it's really going to cost you $650 to make each one, that's quite a chunk to swallow isn't it for such a small run and isn't really worth the effort if you're not making anything off of it.

    A Y6 may be a little more inefficient on the underside props but if you're going to argue that point, using heavy aluminum for everything is MUCH more inefficient and expensive. If you're worried about blade scrapes from beginners, I think buyers should be worried about the expense of replacement parts more than replacement blades.

    It's a nice looking bird but it seems like there's not much in it for you money wise if your numbers are correct and it will eventually be unsustainable for buyers as replacements are not going to be cheap as well. I wish you the best of luck as getting something up and running can be difficult. I've even thought about starting something up myself but it's just too much risk for me at this point in my life.

  • It's a solid tried and proven design, you just need to loose the metal. Every gram is robbing flight time. Replace it with carbon and use nylon hardware.

    Also that stock Turnigy rx does not handle failsafe last time I checked so that could be an issue.

  • I'd like to respond to your guys comments:

    HeliStorm

    - I agree I don't think it looks anything like the Starfighter.

    - I considered a Y6 but the underside prop efficiency is reduced and blade scrapes by novice pilots are easier.

     Healthyfatboy

    - Your math is pretty close, however my hard costs to build it in such small quantities are MORE than $650.  Precision components made in the US in small volumes are not cheap.  The only reason this product is economically viable is because I'm selling directly to the users instead of going through re-sellers, hobby shops, etc.

    - I've experimented with most of the flight controllers and I know the KK isn't the latest and greatest, but it works well and it helped to keep the costs down on the entry level one.  Of all the ones I used the APM was in my opinion the best by a good margin.

    Quadzimodo

    - It is relatively heavy with a relatively low payload capacity.  That's a fair criticism, however I prefer to understate specs.  Flight time is only down to 3.7V/cell and it's measured at 4700ft elevation.  I've seen 13min at sea level if I push the batteries.  Also, I am currently endurance testing motors, ESCs and props that will increase the payload on the pro by over 100% and the flight time by over 50% if they pass the tests.


    - Your criticism of the mass location is also fair.  However, it was important to me that the payload deck be quickly interchangeable so that one could go from an FPV setup to a camera to a light weight acro setup quickly without tools in the field.  I was also able to dampen the vibrations pretty well even without a lot of mass, so I would hope one could judge the result more so than the pre-established "right" way.  

    - The chassis is much stronger than is needed for the current 3S/4S setup, it was my hope that if the chassis was solid one could simply upgrade to stronger components / heavier payloads as they become available without worrying about chassis.  

    - The PID equation simply gives one a more thorough understanding of how to properly tune the controller... it wasn't a marketing gimmick.  I didn't even have that picture in the campaign until Kickstarter required me to show some of my development work.  I just snapped a picture of what was currently on my whiteboard to fill their need.

    I welcome constructive criticism and feedback as no one designer and no product is perfect.  I had an idea that a solid, easy to use chassis made specifically to be easy to upgrade would bring joy to people and give me a job doing something I love. 

  • RC junkie - I am happy to admit that while I recognise the formulas, I have never needed to transpose them for manual calculations, or really ever taken the time to properly dissect and comprehend. But I am yet to design my own flight controller or develop outside the standard tuning parameters, so assume that this is not unusual... Is it? Ecalc and well resolved off the shelf controllers like the KK and APM have saved me that need thus far.

    I just don't understand why it might be relevant to have a whiteboard lying around featuring the raw formulas yet no actual calculations, other than for marketing effect. For example, why not show actual figures for maximum theoretical power and thrust instead of the raw formula by which they can be derived?

    Perhaps I am just being overly critical. At the end of the day, the footage generated by the switchblade is streets ahead of what is coming out of my jelly factory at the moment.
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