FPV250 Long Frame Quadcopter

by Red20RC | June 25, 2014 | (9 Ratings) Posted in Reviews

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It was only a matter of time before I got hooked by the idea of a 250 size quadcopter. I love the look of the “long frame” style quads made popular by designers like Blackout and Lumenier, so when HobbyKing released the FPV250 quadcopter long frame version I couldn’t resist…

FPV250 Quadcopter from HobbyKing

56212HobbyKing is making a habit of bringing out affordable versions of some of the world’s most popular multirotor frames. I personally already own the SK450 Deadcat quad (TBS Discovery layout – although the Reptile is closer) and Q450 quad (DJI Flamewheel F450 clone). Both of these are fantastic frames that cost only a fraction of their “brand name” counterparts.

The FPV250 racing frame continues this trend by being a pretty close match for the popular QAV250 by Lumenier. It isn’t identical though. In order to keep their development cost down HobbyKing have taken the already successful FPV250 quad and added a long frame conversion. This is made up of two short plates that extend the base of the frame and a long top plate (full length unlike the 2/3 length plate on the QAV frame). These are joined by 8 threaded tubes that are anodized a tasty red colour.

Planning for some fun…

39033For my FPV250 quadcopter build I wanted to go the whole hog. It was going to be FPV ready obviously with a board cam for vision married to the awesome ImmersionRC 600mw VTx. Recording my feats of daring-do would be handled by the new Mobius B Lens camera.

I had a few KK2.1 boards on the shelf so the flight controller was sorted. I wanted to use the recommended HobbyKing setup for power so I also ordered in the Multistar 1900kV micro motors, GemFan 5×3 3 blade props, Afro 12A ESCs and 1000mah 3-cell LiPos.

Putting it all together…

The main frame is a solid one piece affair so it was only really a case of adding the top and bottom plates. Some nicely thought out metal bushes ensure the bottom plates lock perfectly into place.

TIP: Don’t attach the top plate until you have mounted your flight controller, ESCs and motors, and sorted out all the wiring.

I decided I was going to get fancy with the wiring to try and save some weight. To that end I created a custom wiring harness that connected all four ESC’s to the power input without the need for a breakout cable.

2014-06-20 10.08.07-1920 2014-06-20 10.08.13-1920 2014-06-20 11.24.25-1920 2014-06-20 23.24.54-1920

Attaching the motors was where I hit my first snag… The mounting holes and screws are so small on the tiny Multistar motors that there is no way to mount them to the thick arms of the FPV250 quadcopter frame. In the end I decided my only solution was to attach the mounting plates to the motors and use cable-ties to fix them to the arms. In hindsight this is a good idea as this frame will no doubt suffer some abuse and the ties make for easy maintenance.

TIP: Use ties in all four holes as the mounting plates are thin and bend easily if only fixed at two points.

Big problems with small ESCs…

2014-06-20 13.18.07-1920The Afro 12A ESC is the perfect fit for this frame. Small, light and pre-flashed with the now obligatory SimonK firmware – they should have been a match made in heaven…

Skip forward then three hours to the point where I discovered that these ESCs put out 6 volts at the BEC instead of a more normal 5 volts. Yes, you may well shrug your shoulders. “So what?” you are thinking. Well, try applying 6 volts to a KK2.1 board and then try setting up your receiver… not so funny now eh? For some reason the KK2.1 does not like 6 volts. It looks okay until you try to use it and discover that extra volt has somehow scrambled the incoming receiver signals and nothing works. Trust me, I tried it on 5 KK2.1 boards including two in flying airframes – nothing.

2014-06-20 22.08.21-1920In disgust I snipped the wires, tore out the ESCs and threw them in the cupboard – ordering some Multistar 10A replacements. I didn’t want to use an external BEC as they were all too big and I didn’t want to wait (even now though I would have to). After I had calmed down though I had an idea…

In my box of bits I was sure I had an old 5A (ish) ESC from my Shockflyer days. I dug it out and tested it – 5 volts steady at the BEC. So I stripped off the coating and removed the motor wires and signal wire leaving only power in and power out. When I was finished it was not only smaller and lighter than the smallest BEC (I could find quickly on HK), but it was here already and FREE!

Fitting it to the frame was just a case of removing the red and black wires from the M1 ESC and replacing them with the BEC output. Power up and job done!

Kitting out the FPV250 Quadcopter…

I sat the ImmersionRC 600mw VTx at the back. The flight cam is one of the new Turnigy 700TVL units. These are truly tiny which is awesome, but also makes for some mounting conundrums. In the end I used the supplied mounting bracket and yet more cable-ties to fix it into place. The FrSky FASST Rx sits neatly on top with the Mobius held in place with a simple velcro strip above the flight cam.

The gap in the rear of the frame is perfect for a small 3-cell LiPo and I used a little mouse-mat gel to ensure a snug, slip-free fit.

Finally the GemFan props are perfect for the little Multistar motors. I think this is the first time I haven’t had to adjust a prop-center to get it to fit on a motor! I had intended to try some 6 inch props on this quad but the long frame prevents anything larger than 5 inch props swinging.

Ready to go this FPV250 quadcopter weighs in at 540g with the Mobius attached (499g without).

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Let’s go flying then!

I was so excited to get this quad flying that it was really annoying when the first flights were a total disappointment!

On the plus side, the KK2.1, flashed with the latest Steveis Pro firmware flew perfectly out of the box without me touching any settings.

On the downside, the power was marginal. Hover was achieved at around 60-70% throttle and the low voltage alarm (set to a dangerous 3.3v per cell) was kicking in within seconds of leaving the ground! Something wasn’t right. The batteries were toasty when I landed so I could only surmise that the little 1000mah 3 cells, despite being a 25-35C rating just weren’t giving enough juice. Whilst I was at it, HK had just released the “Baby Beast” 2150kV motors so they might help too! So I jumped online and soon had some new motors and 1300mah 30-40C cells on the way.

Into the air… again…

The 1300 cells were the first to arrive so I decided to give them a go with the current motor setup. The difference was stunning! Hover still required a little more throttle than I would like but there was definitely more power on tap and the low-voltage alarms were silent. I bumped up the stick scaling on all axis as well to make the frame more responsive and turned on the Mobius for the first time…

Bear in mind that this is raw, unstabilised footage. It’s an essentially untuned airframe and it was the first proper flight so no FPV, self-levelling was on, and all I did was beat up and down the reserve behind the house.

People are going to ask me for some settings so here they are:

Controller: HobbyKing KK2.1  |  Firmware: Steveis V1.17S2Pro

PID Values – Pitch/Roll: (P) 65, (I) 30  |  Yaw: (P) 65, (I) 50

Self-levelling: (P) 45

Stick Scaling – Roll: 45  |  Pitch: 45  |  Yaw: 60  |  Throttle: 105

All other settings remain unchanged from the default firmware settings.

Conclusion

The FPV250 Quadcopter with the long-frame conversion is another winner from HobbyKing. I’ve only given it 4 stars because of the problems I had with the motor mounts and the BEC voltage. The frame itself however can’t be faulted and the flight performance even before the coming upgrades is good enough to make me forget any small problem I had getting there.

There will always be those who will say “Yeah, but carbon fiber is stronger and the Blackout/Lumenier micro quads are better frames.” To be honest I totally agree! But they also cost 8-10 times the price of the HK frame. If I am going to have some fun and push the limits with a micro racing quad, I’m going to feel a lot braver if I know the whole frame can be replaced for less than I paid for the breakfast I just ate while writing this…

Watch this space for more videos and details on the upgraded motors, props and power distribution board that HK released yesterday!

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See more of my projects and articles at www.red20rc.org


UPDATE! My FPV250L has now had a complete rebuild. Catch the FPV250L Rebooted article at red20rc.org.

Was it worth all the effort?

Comments

Rainy Day RC on June 25, 2014
Nice! I followed your build on instagram @red20rc. Looks great, and thanks for the headsup about the KK2.1.5 not playing nice with 6 volts. I just set up mine (the article will be published soon) so you can see the setup of my laser cut quad.
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royce.meredith on June 29, 2014
Hey glad to see an article regarding the FPV250! I've been flying one with a Flip32+ flight controller and it has been fantastic! If you're interested check out my YouTube channel https://www.youtube.com/user/MiniQFPV/
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Red20RC on June 30, 2014
Thanks for the YouTube link. Always interested to see mini-quad videos and get some inspiration!
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stevevm on June 30, 2014
I'm looking for some help with my fpv250. I'm using the kk2 (about a year old) the zmr 1804-2400 motors and emax simon series 12A escs. The last couple of times that I've flown it, it has worked fine for a while but then it just rolls over and crashes. Could this be an esc problem or a kk2 problem or something else?
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Red20RC on June 30, 2014
...and make sure you update the firmware on the KK2. The stock V1.5(?) is almost un-flyable.
Flash it with the some Steveis firmware and you won't regret it! - http://www.rcgroups.com/forums/member.php?u=367321
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stevevm on June 30, 2014
I'm using 1.5 or maybe 1.6, I will try the steveis firmware.
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Red20RC on June 30, 2014
If you're only on the stock 1.5 that ships with the KK2 boards that may be your problem.
My first ever multirotor I couldn't wait for the programming cable to arrive so I flew it on the stock firmware and couldn't keep the thing in the air! Once I had update to Steveis firmware the difference was massive.
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stevevm on June 30, 2014
Cool! That will be the first thing that I try
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Red20RC on June 30, 2014
I'm definitely not the expert on this but two thoughts come to mind:

1. Vibration - sometimes what starts out as okay can turn sour as the vibrations build. The gyros on the controller cope for a while and then suddenly give up. Make sure your props and motors are balanced.

2. ESC overheating - I had this on my SK450 Spider quad. The first battery would be okay but if I went straight into a second battery it would almost certainly tumble out of the sky after a few minutes and nearly always by rolling over the same arm. I discovered that I had overpropped the motors and the ESCs couldn't handle it. I guess there had to be a weak link and one ESC wasn't coping quite as well as the rest, which is why it seemed to always roll over the same way. I swapped to smaller props and life is good. What size props do you have? Those gemfan 3 blade 5030's might be a bit much on 2400kV.
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stevevm on June 30, 2014
i've balanced the props and the video seems pretty good. I'm using the gemfan 5030's which seem to be the norm. If the esc's are overheating, i expect they would be warm to the touch which I haven't noticed but will check.

I'm thinking of reflashing everything and also have a flip fc on order, maybe that will solve it.
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donnyb on July 3, 2014
I built the same frame and used 2805 2800 kv motors. My battery got pretty toasty also. And I only could run for about 5 minutes even with a 60c 2.2 amp 3 cell battery. Something I did notice one escape would get warm compared to the others. The one that powered the receiver and the kk2 board. I used a separate ubec to run the kk2 and the receiver. Then motor 1 seem to have less problems. Broke a lot of props running in to things in the living room. Lol! Very nice artical.

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Red20RC on July 3, 2014
Thanks for the comment!
Mine has now been totally rebuilt with the new micro power distribution board and "baby beast" 2400kv motors from HobbyKing. I swapped to the 2 blade 5030 gemfan props as the 3-bladers were way overpowered.
Flew it in anger for the first time today and it was totally awesome. I'm getting 5-6 minutes of pretty hard flying out of my 1300mah 30-40C lipos and they are only slightly warm.
Looks like I may have to do another article to document all the changes!
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donnyb on July 9, 2014
Actually that sounds great! I would like to know more about how the new motors work for you. And like the clear photos of where you set your components. I tried to under-sling the frame an try it with bigger props. Didn't make to much of a difference on flight time, but I think it's still really neat. Actually I do have a question for you. What type of prop balancer do you use? I been using the top flight magnetic balancer, but thinking of getting the dubro. Even when everything is balanced out I still get a lot of vibes. But but when I balance the props on a motor and use tape to counterbalance while it's spun up. I put it on the magnetic balancer and it shows its off.Lol! think it's cheap props?

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Red20RC on July 13, 2014
Did you see the "reboot" article on www.red20rc.org yet? That has all the details of the rebuild and some video as well.
For balancing props I found an old hand balanced in the spares box (just a threaded shaft and two metal cones to lock the prop on square). It was useless doing it by hand so I actually made a little stand out of foam board and glued two magnets onto it to suspend the balanced friction-free. It seems to work well (scroll down my instagram feed - www.instagram.com/red20rc - and you will find a picture of it).
To be honest though, on the FPV250L I am using the GemFan 5030 2-bladers now and haven't bothered to balance them at all. HobbyKing are selling the genuine GF props now and they are pretty much awesome right out of the packet.
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donnyb on July 13, 2014
Hey I just seen it! And a nice video also. I really like the mini power distribution board location. I think I'm going to redo mine with the power board under the flight controller. Mine was wired with the 12 or 16 gage wire and I had issues with it. Plus the extra weight of the 20 amp speed controllers was a little much. Lol need to pull out the credit card!
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Red20RC on July 13, 2014
Oh, and the "low-hung" frame looks awesome. I am sooooo tempted to pull it all apart again and give it a go...
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Ballsy on July 4, 2014
I've got the same frame and actually designed and cut my own longframe out of G10. I have some carbon sheet I layed up and the next version will be cut from that. I have the multistar escs and 1900kv motors on now and hover just over 50% throttle. I find I get the best flight times using a 1300 3s 25C GensAce pack. My flight controller is the AfroMini 32 which flys great out the box. We have done some tweaking of the PIDs to help with stability in the wind. Now its rock solid. I also installed a power distro board which helped clean up the wiring. Been flying with just an FPV cam but borrowing a Mobius for this weekend and will post some footage. I also have new beefy motors http://witespyquad.gostorego.com/motors/rtf-mini-motor-x2204-2300kv-476.html and 12A simonk escs which I will fit to the next carbon version.
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Red20RC on July 13, 2014
I think the more powerful motors definitely help, especially when you start adding things like a Mobius or GoPro to the frame.
I've just bought a CNC milling machine so am looking forward to trying out some cutomised frames!
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ruumoo on January 10, 2015
can somebody help me?
I've bought a KK2.9 5.5 flight contoller and it doesn't recieve throttle signal.
I've checked all the wires, voltage, changed reciever and transmitter, battery but it just doesnt recognize the throttle input
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Red20RC on January 10, 2015
I'm sure we can do something to help!
First two questions...
1. On the receiver test screen are the other signals getting through? (Pitch, roll, yaw)
2. What ESCs are you using?
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