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2Doggs's blog
Posted by 2Doggs | Jul 16, 2014 @ 04:10 PM | 2,592 Views
I've been using these Nano Tech 1800mah 4S 25-50c packs on one of my 450 Pros and a Mini Titan.



On the positive side, the packs seem well made and have silicon insulation on the wires. they are also quite slim, at about 30mm high by 35mm wide, and are an easy fit under the E325s canopy on the Mini Titan when using the one-piece battery tray.

The packs have now done 200 cycles, yet despite me never using more than 1100mah, they seem to behave more like 1300mah packs than 1800mah ones. I keep a spreadsheet of pack data, so I can see that the resting voltage per cell after a flight has dropped from an initial 3.80v when new to 3.74v now, with the (balance) charger putting in around 1000mah after each flight. Using a data-logging ESC, I can see minimum voltages in flight as low as 3.23v per cell.

I bought NT 2650 packs for my 500, and those only have about 40 cycles on them. Again, despite never being over-discharged, the voltage per cell after 5 minutes of light aero at HS2250 is 3.75v. The charger puts back about 1500mah, so in reality the packs are behaving more like 2000mah rather than 2650mah.

I'm giving up on NT's for now, so I've just ordered some Gens Ace 1800mah 4s 25C packs for my Mini Titan. The Gens Ace packs are quite a bit fatter at 34mm x 30mm, though shorter than the NT's, but will fit on their side under the E325s canopy.

I believe the Nano Techs are deceptively labelled, with the capacity greatly overstated. I'd be interested to hear from anyone who's actually achieved the rated capacity from them, and what the per cell voltage is at 80% discharge of the rated capacity.
Posted by 2Doggs | Jan 22, 2014 @ 03:55 PM | 2,369 Views
I finally got around to buying an HK500TT FBL towards the end of last year. I'd been waiting for it to be stocked in the US warehouse.

I fitted it out with HK752 MG servos on cyclic, HK732MG for the tail, and one of my FuBars. I used a Turnigy Superbrain 80A ESC, since I like to use the data-logging feature. The motor is the Turnigy 3126 1600kv, a re-branded Suppo. Like all of the Suppos, the motor comes with nice deep socket head mounting bolts and spring washers, which makes setting pinion mesh a breeze - no threadlock required. The motor is smooth, and didn't need any balancing.

First impressions of the kit were pretty good. The head seems well made, and the fit and finish seemed better than my Skya HK450 Pros.

The mainshaft cover was a really loose fit on the mainshaft, however. I managed to get it to fit by wrapping the mainshaft with a shim cut from a soda can.

The mainshaft itself seemed to have quite a rough surface finish, but there were no problems with other parts - apart from the plastic canopy, which came already cracked, and the torque tube also needed straightening.

During bench testing, I discovered that the tail mechanism was locking up at anything more than about HS1800. Although I tried everything I could think of to get it to free up, it would still only work up to HS2000 or so. I thought it might be due to the excessive play in the tail slider bush, but a replacement align bush - a much snugger fit on the tail rotor shaft - has different threads,...Continue Reading
Posted by 2Doggs | Jun 21, 2013 @ 04:10 PM | 2,659 Views
I decided to take the Turnigy Superbain 45A data logging ESC off one of my 450 Pros and install it on the Mini Titan, together with the Turnigy H2223 motor running a 12t pinion.

Here's a pic of the MT, with the battered and much superglued canopy, in my usual Krylon neon yellow and orange hi-viz scheme. Also just visible in this pic is the grey PVC tape holding two cents to the rear end of the boom for balance!



In the shot below, I have full low collective and full forward elevator. The anti-rotation pin on the swash is almost touching the top of the motor, and the 4s 1800MAh Nano Tech battery pack is as far aft as it can go without touching the motor. This motor is really too tall for the MT! You can also see my low-tech motor balancing, using some Scotch "Magic" tape. It stands up well, and really improved the smoothness of the motor. The can is marked with a paint pen so if the tape flies off, I can replace it without having to rediscover the spot that gets it hot.... so far, it hasn't flown off in more than 200 flights!

On the FuBar FBL controller, I have my collective range set to 80, to give me about -12 to +12 of collective, and I calibrated 8 degrees of cyclic at the minimum cyclic setting of 59. In order to prevent the anti-rotation pin pressing on the motor, I had to reduce my cyclic ring setting from the default 85 to 78.



I did three driveway hovering tests to see how much power was needed at three headspeeds - 2400, 2600 and 2800....Continue Reading
Posted by 2Doggs | Jun 02, 2013 @ 07:02 PM | 2,916 Views
When I bought my Solar 654 servos recently, I figured they would work perfectly with the HK RJX head on my MT. The MT geometry doesn't tolerate the use of shorter or longer servo arms, since the elevator link is so short, and any variation from the "standard" 1/2" arm puts it significantly off vertical.

The 654's move about 15% further for a given signal input than most servos, so with the 21mm arms on the HK RJX head, standard servo arms resulted in a collective range value in my CX-ZYX of 65, just about perfect.

Considering it costs around $12, the HK RJX head is fantastic value for money. I've had one flying on one of my 450 Pro's for hundreds of flights and many crashes, and it's still really slop-free, and I've always preferred the way it flies to my Tarot head. The feathering spindle is a stepped design, like the regular Align 450 Pro one, but I chose to use an Align spindle instead, on which the grip bearings seemed like a tighter fit. The Align spindle is a touch shorter than the one that came with the RJX head, so I also used the spacers off a HK 450 pro spindle rather than the "top hat" style ones that came with the RJX head.

The head is a perfect match to the standard MT mainshaft. I mounted the head using the upper of the two Jesus bolt holes - i.e. setting the head as low as possible. In the image below, you can see that the swash locker arms are pretty well dead level at 50% collective, with the servo to swash elevator link set just...Continue Reading
Posted by 2Doggs | May 22, 2013 @ 02:52 PM | 3,109 Views
I've been meaning to try out some Solar 654 servos for a while on my 450's, despite some reports about loose internal parts and quality control issues.

On the servo tester, they seem fast - about 0.09s @5.5v, matching my Align DS410's which I think are a good benchmark servo for a 450.

I'm impressed by the solid plastic mounting lugs - most servos have the lugs hollowed out on the underside.

The Solar servos come with a good selection of servo arms, including a disc, and all the arms are a good snug fit on the output shaft.

Whilst the connectors on the end of my DS410 leads are a really tight fit in my RX and FBL controllers, the plugs on the Solar servos are a touch slimmer, making them an easy fit.

The surprising thing about the 654's for me is that they move more for a given input signal than most other servos. For example, most of my other servos need a pulse width change of about 900us to move the servo arm thru 90 degrees. The Solars need just 770us. Over their full range, they can move about 140 degrees, compared with 120 degrees for most servos.

I think that might make the Solars well suited to being used with the HK RJX FBL head, which has relatively long 21mm grip arms. With DS410's, I need to use 15.4mm servo arms in order to end up with a collective range value in the FBL controller of about 60. Whilst that's fine on a 450 Pro, the longer servo arms compromise the linkage geometry of an MT too much - in particular the really short elevator link. Using standard 12.7mm arms, I reckon I'd need a collective range value around 65 or so with the Solar servos.

Here's a pic of the Solars in my MT.



It also just so happens that the Solars are a very nice fit in the MT. The aileron servos just need a 2mm spacer to clear the main frames, and the linkage geometry is practically perfect.

Here's a close up showing the single spacers for the aileron servos, no spacers needed for the elevator servo.


Posted by 2Doggs | May 22, 2013 @ 01:40 PM | 3,402 Views
I've always hated the stock tail linkage on my HK 450 Pro, and I've tried the plastic forked Tarot mechanism, which is a lot better, but wears out quickly.

Recently, I fitted the GoGo.Rc tail mechanism, which is nicely made from cnc'd ally and some plastic. I've only had a few flights with it so far, but it seems to be a nice slop-free linkage.

In the end view below, you can see that the forked control arm needs to be aligned with the centreline of the tail rotor shaft. You can use the supplied M2 washers as shims to raise or lower the control arm. On my 450, the arm is maybe just a tad low.

One nice feature of this control arm is that if you unscrew the two locating pins that fit into the grooved plastic tail slider disc, you can remove the tail slider and tail rotor assembly which might make setup and maintenance easier.



The following shot shows the control arm from below. It's a good fit on the 450 Pro belt gearbox, with clearance between the arm and the gearbox. You can also see I had a slight tail strike recently....



In the shot below, you might notice that my tail rotor shaft protrudes beyond the tail rotor hub - it's a bomb-proof shaft made by Steve (Kauaiguy) from a 4mm ejector pin, and has survived at least half a dozen crashes. Wish I had more for my other 450's!

...Continue Reading
Posted by 2Doggs | Apr 30, 2013 @ 02:43 PM | 3,650 Views
My first electric heli was a Thunder Tiger Mini Titan, which I bought used from a friend whilst in the UK. After returning to the US, I discovered Hobby King, and began a journey with HK 450 Pro's, and with the advent of the CX3x1000, I converted them to FBL.

I had been planning to sell the old MT on, and had converted it back to it's original ACE RC format, with a simple TX and integrated CCPM mixer/gyro unit. Happily, the potential buyer pulled out due to lack of funds, and I decided to have a go at converting the MT to FBL using one of my CX's.

In FB form, the MT was always very stable, and being sort of stretched out longways, I was expecting it to be a bit less agile than my 450 Pro's - so I was really surprised at how rapidly it would flip and roll in FBL form - faster than my 450 Pros! I initially flew it with DS410's on cyclic, and an HK15158A on the tail, but I've now replaced the DS410's with Henge MD933's, having returned the DS410's to one of my 450 Pro's.

Here are a few snaps, with some thoughts.



In the view of the left side, below, you can see the CX-ZYX mounted on the boom block using a single layer of 3M tape. The relatively bulky FrSky V8FR RX is an easy fit within the main frame, fitted to velcro on the bottom plate. This RX is too big to fit between the frames of my 450 Pro's....





In the picture below, you can see that the relatively tall Henge MD933's need to be spaced off the servo mounts. For the elevator servo, I used offcuts of some...Continue Reading
Posted by 2Doggs | Nov 11, 2012 @ 04:05 PM | 4,096 Views
Here are a few pics of my HK 450 Pro belt, converted to FBL using the CX 3x1000 controller and a Tarot FBL head.





In the shot below, you can see the Nano Tech 4s 1800 pack fitted with 4mm bullet connectors. The Hobbywing Platinum Pro 40A ESC is velcro'd to the frame, and I run the RX lead thru the frames to the left side. Gotek 9257 tail servo is getting warm (up to 130f) at 6v and 333Hz but otherwise working OK. CX controller fixed with two layers of 3M foam double-sided adhesive tape.

...Continue Reading
Posted by 2Doggs | Oct 13, 2012 @ 09:51 AM | 4,208 Views
So far, I've used three different motors in my HK450 Pro's.

I started with the Typhoon 2218H.



Note that the Typhoon motors use a centrifugal fan, which is designed to draw air thru the motor from the top, exhausting it thru the fan at the bottom. Installed in a 450 Pro, therefore, the fan needs to be reversed compared with the orientation shown in the image, which is how all my Typhoons came. To reverse the fan, you simply remove the bottom retaining plate, and the fan itself is a loose slice of extruded aluminium alloy.

If the fan is left in the default direction, there will be much less airflow thru the motor. The default direction would suit helis like the Mini Titan, where the motor is mounted above the maingear.

I used the 2218H for quite a while in my 450 with a Turnigy Superbrain data logging ESC and various 3s 2200 25c packs.

When set up incorrectly, (too much pitch!) the motor pulled peaks of up to 55A, but with a proper setup, running a 13t pinion, current draw was in the low to mid 30A range.

On my first 2218H, the top bearing started to spin in the housing, and after that the shaft also started to spin in the bearing. This caused enough slop for the magnets to start rubbing on the stator.

After maybe 150 flights or so and several crashes, the last crash resulted in the shaft breaking at the circlip groove. The Typhoons use a 3mm shaft and bearings, and the shaft diameter steps up to 3.17mm at the circlip. I believe that makes the shafts very prone to breakage, with a large stress concentration at the circlip groove.

Shafts don't seem to be available, but if you used a 3mm pinion, you could make a simple shaft from a 3mm drill rod using a spacer or shims under the pinion to retain the can, and therefore not weakening the shaft with a circlip groove.

Overall, it's not a bad motor. You should check the tightness of the grub screw at the bottom of the can - they were loose on both my 2218H's.
Posted by 2Doggs | May 13, 2012 @ 06:04 AM | 4,657 Views
After the second crash in a month with my HK 450 Pro FBL, I had to get a new set of cyclic servos.

I had been running 2 x Henge 933's with a Corona 929MG on elevator. One of my Henge 933's had crapped out, starting to jitter a lot around neutral, and I was fed up with flying with a permanent bobble. Kauaiguy put me onto the fact that the controller can compensate for any differences in cyclic servos, so though the 929 is a faster servo than the 933, the heli flew fine, until the next crash.

Being in the UK, I had to buy servos from a brick and mortar store, and ended up getting Align DS410's, at GBP18 each, including the pesky 20% VAT (sales tax)

I could have gone for the metal gear versions, which were a bit more expensive, but since I was using Align DS4 servo arms, which are pretty beefy, I decided to go with the plastic gear version. I'm hoping the gears will strip in a crash, protecting the servo cases.

The servos are a perfect fit in the 450 Pro, and the cases look reasonably durable, though the mounting lugs are hollowed out on the underside, same as the Henge's and Coronas.

In flight, the DS410's perform very well. On the servo tester, they show 0.09s @ 6v, right in line with their specs, and they have very little gear backlash. The heli feels noticeably more "locked in" than it did with the Henge/Corona mix.
Posted by 2Doggs | May 13, 2012 @ 05:44 AM | 4,543 Views
In the past, I used a Hitec 5084MG servo on the tail of my HK 450, with various gyros, ranging from an HK401b, CSM420e, Assan GA 250 and a Leader Hobby GY 520. It seemed to work well, though not really much better than the various 9257 clones I've also used.



Recently, I got the chance to fit the 5084 in my 450 FBL heli, which uses the CX 3x1000 FBL controller. I have used a Fitec FS9357D in that heli, which gave good results until I managed to burn it out. I had neglected to do any maintenance on the tail pitch control, and there was some serious binding which did for the servo in the end.

Since then, I've been using an HK15158A 9257 clone, which has the great virtue of being dirt cheap, but sufferes from a bit of slop in the gears.

Teamed up with the 3x1000, the 5084 seems to work really well. I'm running it at 6v and 333Hz, and it's staying nice and cool. (I check the linkage for binding regularly now!)

With the 5084 being a mini servo, I have to use an adaptor to fit it to the 450 Pro tail servo mount.
Posted by 2Doggs | Mar 08, 2012 @ 05:42 PM | 5,695 Views
I first used Henge MD933 MG servos in my HK 450 Pro. They worked well for many flights, and were a perfect fit into the 450 Pro - though with the inexplicable different servo fixing bolt spacing on the Pro for the elevator servo, I had to file out the top mounting lug on the elevator servo.

The plastic cases are quite brittle - and after one crash, one of the aileron servo cases broke at the mounting lugs. I had not used any washers under the M2 bolt heads, however, and refitted the two surviving servos and a spare using washers, which I believe gives a bit more crash resistance.

The horns supplied with the servos are quite brittle, but hold a linkage ball securely enough without using an M2 nut on the back of the servo arm.

The 933's seem quiet and smooth in use, and seem to have good centring and resolution - but they also seem slower than the claimed 0.11s. My CX program box shows them as taking 0.14s @ 6v.

After well over a hundred trouble-free flights with the 933's, my next crash took two of them out. Both aileron servo arms were broken, and the servo cases cracked, and the plastic 2nd gear small pinion stripped.

I therefore decided to give the 922's a try. They're claimed to be faster than the 933's, but on the CX tester, they show almost exactly the same speed. They also run quite noisily, making a rough grating sound, and seem to have more backlash than the 933's.



Whilst my 450 Pro flew with all the default cyclic settings for the #5 preset model with the...Continue Reading
Posted by 2Doggs | Mar 08, 2012 @ 12:36 PM | 4,676 Views
Much as I've enjoyed flying my HK 450 Pro, it has been completely transformed by going FBL, using the HK RJX style head, and the CX 3x1000 controller.

It flies almost like a sim model - and the controller makes it so easy to do piros. Maybe that's why some people consider an FBL heli to feel "robotic", and maybe it might come as a shock to my system to fly an FB heli again!

Here's the setup:

Controller CX 3x1000
Motor Turnigy Typhoon 2215H 3450kv
Pinion 11t helical onto 121t main gear
ESC Turnigy Superbrain 40A with separate Turnigy 5A SBEC set to 6v
RX FrSky V8FR used with FrSky 2.4G module in JR 9XII TX
Cyclic Servos Henge MD922 MG 12.7mm arms
Tail Servo Fitec FS9357D 8.5mm arm
FBL Head HK RJX style
Main Blades HobbyPartz 325mm Carbon (21g ea)
Battery Zippy 3s 2200 25C x 3, Zippy Rhino 3s 2200 25C x 2

I mounted the controller on the gyro mount behind the anti-rotation guide, with the servo leads facing aft. with my ESC mounted externally by velcro on the right side, and my RX on the left, all my wiring is to the rear. It's functional rather than pretty...

The Zippy Rhino packs are holding up much better than the regular Zippy's, which now get pretty warm after using up 1400mah or so, and show much more voltage sag than the Rhinos.

I got the helical gears to reduce noise, and they seem a bit quieter, but I suspect they also cause the motor to pull an extra 0.5A or so for the same HS. I'm currently using the (excellent) SB governor High...Continue Reading
Posted by 2Doggs | Mar 02, 2012 @ 06:55 PM | 4,455 Views
I'm using this head on my HK 450 Pro (belt) heli, and quite like it. Here are some thoughts on its use.



Tiny Steel Washers

When I got the head, it wasn't immediately obvious to me to use the small steel washers in between the shouldered ball bearings that fit into the swash locker arms. The bearings are a very tight fit into the swash locker arms, and once pressed in, are almost impossible to remove. For one of the swash locker arms, therefore, I have to be careful not to over-tighten the pivot bolt, otherwise I get some binding from excessive side loading of the bearings.

The swash locker pivot bolts also serve as pinch bolts to help secure the head to the mainshaft - which seems like a good idea. The downside however is that I have to limit how tight the pivot bolt on the "good" swash locker arm is, since if I fully tighten that it will exert pressure on the other bolt, causing some binding. I'm really kicking myself for having left out the steel washers! At least blue threadlock holds the pivot bolts, and they haven't loosened in use.

Optional Mounting holes


Another good thing about the RJX head is that there are two sets of holes for the top "Jesus" bolt. Using the upper hole enables the head to sit lower, which helps agility a bit, and looks pretty good too.

Feathering Spindle - Bad!


The feathering spindle that came with my head was crap - I didn't bother using it, since it felt undersized, and the bearings were a very...Continue Reading