With the Talon Tricopter giving me problems I decided to try out another of my favourite configurations - the "Deadcat" quad.
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Spider Style
Also known as "Spider" style, the "Deadcat" configuration is an 'X' quad with a standard 90° angle between the back booms but the front booms spread much further. The reason for doing this is that when flying FPV or filming with a front-mounted camera a 90° angle between the front booms will mean your props appear in the shot all the time.
The term "Deadcat" comes, I believe, from the fact that the shape of the layout looks a bit like those old tiger-skin rugs you see in the movies. That and the fact some bright spark posted a video on YouTube of one of these quads with a stuffed cat strapped to it!
There are plenty of different frames to choose from. Of course, the most famous of all I guess would be the TBS Discovery series but with a price tag of over $1000 this frame falls way outside our mission of getting the best performance for the lowest cost. A quick scout through Hobby King brought up the SK450 frame with a deadcat conversion kit.
Orders in - time to sit back and relax...
At only about $35 for the complete frame I knew I didn't really have much to loose and the reviews were good so I started to build my shopping list. At the time I couldn't get the Integrated PCB version from the Australia warehouse so I decided to go for the V1. Maybe next time we'll look at the "Defibrillator" model. I didn't want to make the same mistakes I made with the Talon. Most importantly I wanted to try some different, more powerful motors and also find some Atmel chip ESC's that I could flash with the SimonK firmware. As a result I ordered the following:
- SK450 Quadcopter Frame
- SK450 Quadcopter Deadcat Conversion
- Turnigy D2836/8 1100kv Outrunner (x4)
- Turnigy Multistar 20A Multirotor ESC (x4)
- Hobby King Quadcopter Power Distribution Board
- KK2.1 Flight Controller
- A selection of 10 x 4.5 slowfly propellers
Incidentally, I realised with the Talon that, especially for a beginner, flexible slowfly props are much better than those posh carbon jobs. The reason for this being it is much easier/cheaper to replace a prop when you have a bad landing than it is to replace a motor shaft, boom, tail servo, linkages, thrust bearing etc.
After a very short wait a lovely parcel of goodies arrived on my doorstep...
Time to put it all together
Putting the whole frame together took a little less than a lunch break to do. In fact I did a lot of it sat on the floor in my lounge with my 15 month old son "helping". I did find a couple of the supplied bolts had dodgy threads and wouldn't go in but as extra were supplied this wasn't really a deal-breaker for me. I did use cyano' on the threads to lock them in (didn't have any proper thread-lock at the time). This proved to be a bit of a double-edged sword though as the bolts are indeed now locked in place, so tightly in fact that when I found I wanted to rotate one of the motor plates by 90° so the leads matched up I stood no chance.
TOP TIP! If you are going to lock the threads on your bolts, make sure everything is aligned and you don't want to take it apart again any time soon!
Very quickly then I had a completed Turnigy SK450 Deadcat Quadcopter sat in front of me waiting for the electronics.
Finishing it off with some motive power
Adding the electronics was just as easy as putting the frame together. The motors were a good fit in the mounts and everything else attached with cable-ties and double-sided tape. I didn't like the idea of having my KK2.1 out in the breeze on that platform so opted to remove it and mount the controller inside it's foam box to the main plate. This is a tip I heard somewhere on the web and it makes sense to protect this delicate bit of kit to my mind. The power board went underneath the KK2.1 between the plates but I did find it a stretch getting the ESC's to reach. In fact I eventually replaced the ESC power leads with longer ones when I removed the covering to do the firmware upgrades.
TOP TIP! The new breed of KK2.1 has two separate power buss' so you no longer need to remove the red 5v lead from 3 of your ESC's!
Software upgrades
I think it is now widely accepted that the stock firmware on the KK2.1 (v1.5) is a bit dodgy and you really have to upgrade to get the best from your multirotor. I'm not going to go into great details on how to do this as there are a million awesome guides on the internet that show you how. I decided to load up the latest "Beginner" firmware from Steveis to start with so I didn't have to go through all the extra menus when setting up.
TOP TIP! You will need an USBasp device to connect your laptop to your KK2.1. These are nearly always out of stock on Hobby King but you can find them on eBay for a few dollars. Just make sure you also buy the 10-6 pin adapter or you will be very frustrated!
Upgrading the ESC's is not quite so essential as the modern si-labs chipped Turnigy Plush and Atmel chip Multistar ESC's are pretty good out of the box. If you do get an Atmel chipped unit though the new SimonK firmware does improve the throttle response a great deal.
TOP TIP! Get the Atmel chip adapter cable from Hobby King. This little tool makes flashing ESC's incredibly quick and easy to do.
Flight Controller Settings
Setting up a Deadcat quad is a little different from a normal quad as the varying arm angles upset the geometry on the KK2.1. I did a lot of research to find the best settings and fortunately took pictures of them all before something happened and I lost them!
First Flights
I conducted my first flights in the now traditional howling gale and too-small area. Even with those disadvantages I could tell that this was going to be an exceptional flyer. Power with a 2200mah 3-cell lipo was more than adequate with a half-throttle hover achieved easily. With the self-level on it was rock steady in the air and those "soft" settings made it easy to control with very little wobble. After only a short time of flying I decided to load up the FPV gear and see what trouble I could get myself into...
TOP TIP! Always make sure your buzzer is connected on the KK2.1. If you crash land in a field of waist-length grass the lost-model alarm will kick in after 30 minutes of inactivity and you won't lose your GoPro and all your FPV gear along with your frame!
Conclusion
The Turnigy SK450 Deadcat Quadcopter is about as much fun as you can have with your clothes on! The flight performance is exceptional and the solid, locked-in feel make using this frame for FPV a pleasure. It is true that you could go out and spend around 5 times the cash to get a DJI Phantom (not Deadcat) or around 10 times the cash for a TBS Disco (pre-built) and have the same if not better performance out of the box. The goal of Red20RC though isn't to show you what the financially unchallenged can do with a credit card and no experience! We are passionate about getting the best from the lower end of the market and we are overjoyed when the results are as good as the Turnigy SK450 Deadcat Quadcopter!
Get one - you won't be disappointed!
PS - I'm not knocking TBS or DJI, I'm just a firm believer that anyone can buy performance but true satisfaction comes from building it :)
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The amount of power on tap it could certainly handle a larger battery, even the balance with the GoPro and FPV gear would benefit from a little more weight out back.
I only use 2200's because that is the go to battery for 90% of my aircraft and is what I have most of in the tin!
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The Deadcat conversion is awesome because it gives you so much more space for gear (and it looks cool). I'm even tempted to stick an APM on it at some stage and see how it goes in fully autonomous mode.
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Nice setup and good review. Cheers
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Even that isn't nearly as bad as I thought so may be worth a direct comparison to the SK450 "Defibrillator" board at a later date.
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Probably should have mentioned the radio gear! You do need a receiver as this is what takes your control inputs and feeds them to the flight controller (KK2). Basically, what happens is your receiver outputs aileron, elevator, rudder and throttle - that goes into the left side of the board. Then on the right side you plug in your four ESCs (in the correct order). The KK2 takes your control input, does some complex maths, and tells all four motors what speed they need to spin to achieve your request.
If you look on the final picture in the article you can just about see a FRSky 2.4ghz receiver at the back, just in front of the battery.
AND - as a word of advice, don't tie your receiver aerials down parallel along the battery like some Muppet (i.e. me) did in that photo. It reduces your radio range and your multirotor will drop like a stone into long grass whilst you are flying FPV and it will take you an hour in searing heat to find it... (don't ask me how I know)
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I used the OrangeRX receiver for the first flights as it was what was sitting on the bench at the time. They are awesome little receivers (especially at $6) but, as they are DSM2 short antenna units, they are only really suitable for applications in cheap "parkflyer" type models. As soon as I put the FPV gear in I upgraded to a full-range Futaba FASST receiver.
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Thanks for the comment!
This article was a shortened version of one on my site. If you take a look at - http://red20rc.org/turnigy-sk450-deadcat-quadcopter/ - you'll find all the details about KK2.1.5 settings as well as some other top tips for flying the SK450 DeadCat!
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I'm new also kinda a newbie in this quadcopter scene. I thought it would be a cool thing to get this deadcat conversion for myself also (It couldn't have been so hard to get this thing flying smoothly...right ;)??). I managed to assemble the quad but now I'm having hard time configurating it. I'm using CC3D /open pilot to configurate the quad and I'm using Turnigy 9XR as my radio.
My main problem at the moment is that with the smallest throttle input from my radio the motors gain too much RPM -> with 10inch props the quad blasts in to the sky.. only way to get it down is to try to get it as smoothly as possible back down to the ground by giving some throttle input to it.
Beneath this major problem I ofc have still lots of configuration to do with the PI and possibly D settings. I didn't realize that an asymmetric quad could be a hard nut to crack for a first timer..
If you guys are able to give some small hints / explanations for me with these infos, I'd totally appreciate it. With regards,
Mike from Finland
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I've been looking for the arm bolts for ages and I cant seem to find them anywhere! does anybody know where I can find them?
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Where in the world are you? The bolts on this frame are metric so I guess you might have a problem if you are in the US. However, they are M2.5 x 6mm socket head, although any M2.5 x 6 will fit.
Of course, HobbyKing don't actually sell them but a quick search on eBay should find some. There's plenty listed in Australia if I do a search so you should have some luck.
If you get really stuck give me a nudge and I'll get some in next time I'm putting an order in with my supplier and send some over to you.
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