SAB Heli Division Goblin 700 HPS Head - Review - RC Groups

SAB Heli Division Goblin 700 HPS Head - Review

Chris Mulcahy reviews the "High Precision System" head conversion for the Goblin 700.



High PrecisionSystem "HPS"
Head ConversionFor The Goblin 700
Manufacturer:SAB Heli Division
Available From:Hobby Retailers

There is no denying that the Goblin 700 has become extremely popular, with its unique design and outstanding flight characteristics it is easy to see why. One of the things I've always liked about SAB, is their eagerness to listen to customer feedback, constantly trying to improve their products. The Goblin 700 was designed as a high performance 3D monster, and as such the rigid design of the "DFC" style head didn't lend itself well to lower head speeds. Now you might be asking "why would I want to run lower head speeds?", and the most obvious answer is to get longer flight times. Many different people like to run various head speeds to meet their own needs, so to this end, SAB released the HPS head as an optional conversion for the 700 and 630. With the HPS head you can still run high head speeds, but you can also run much lower head speeds than previously possible.

In The Box

The small box contains all of the parts you need to convert your Goblin 700 to the HPS head system. This includes a new swash that has four balls already installed, instead of the two on the original swash. (Note: The 630 conversion kit does not contain a swash, as the stock 630 swash already has holes tapped on all four sides). The packaging follows the same aesthetically pleasing design as the actual kits, with foam inserts carved out to accept the major components, and all of the smaller parts and hardware contained in individual labelled bags.


The manual does an excellent job at telling you which labelled bag you need for the step you are on. Assembly actually begins with the disassembly of the original head. The main head block is replaced, as are the blade grip arms. There are a few assembled parts in the kit, but I went ahead and double checked everything had thread lock. The kit also provides shims for adjusting the preload on the blade grips. As it turned out, my assembly was too tight with the shims, and this is okay as long as I check the preload after twenty flights or so. I made sure to lube the head where the new dampers and spindle sit (I used boto-lube), and double checked that all the bearings were greased. The radius arms (swash followers, washout arms, et al) are attached directly to the head block, so there are no alignment issues to worry about. The new head block is held in place with a single bolt through it and the main shaft, as well as clamped to the main shaft at the bottom of the head block - it isn't going anywhere without that main shaft!

As you can see, my main shaft had some grease and what looked like a bit of rust forming, so I decided to clean it before installing the new head. Before I did anything, I covered up my motor can with a poly bag to stop any rogue debris being drawn in by the strong magnets. I then used some wire wool and cleaned up the main shaft to like new condition, and used a can of compressed air to make sure there was no debris left sitting on any of the parts.

The linkage rods that connect the swash to the blade grip arms are actually turnbuckles, meaning that on one end the ball link screws on to the link clockwise, while the other end attaches counter clockwise. This allows minute adjustments to be made when setting up the head geometry. No more whole link turns when you only need half because of single direction ball links! It is also worth noting that the new head block also has the same pitch markings etched into the top just like the original head block.

The whole conversion took less than an hour, even with setup time. I had to double check that my cyclic and collective pitch settings were correct, and they only required a slight adjustment. With the conversion now complete, I turned my attention to my governor settings on my Castle HV160 ESC. Even though I have my motor geared to run goverened at 2200 rpm, I picked one of my flight modes and set it to 1800 rpm just to see how it would do. With my ESC settings complete, it was time to head to the flying field. The photo below shows the left over parts from the conversion, which I stored in the HPS box just in case I wanted to switch back at a later date.


Out at the flying field the first thing I noticed was that it is a little more difficult to get the canopy on and off the Goblin. Before the conversion, I would turn the head so that the pitch links sat in the front and back of the helicopter. This allowed the canopy to slide easily over. Now, I've found it best to turn the head to a 45 degree angle (from front to back), and the canopy must be pulled out to the sides a little bit more as you slide it in place.

For the first flight I left the Goblin running at 2200rpm to see if I could feel any difference between this new head versus the old head. I honestly couldn't tell much difference, but I've been told by people who fly a lot harder than I do that the original head feels just a little crisper than the HPS head. I flew tic tocs and piro flips, and I really couldn't feel any difference between the two, which felt great to me because I was worried about losing some of the "feel" that the Goblin has.

Towards the end of the flight I dropped the head speed down to 1800 rpm. It was a little bit of a shock at first as it sounded like the motor was going to quit, and then the governor kicked in and kept it humming. What a sound difference between the two head speeds! It sounded like I was in throttle hold doing an auto rotation. However, even at 1800rpm, the Goblin was still smooth without a single wobble in sight. I carried on flying it like I normally do, and found that the Goblin was still very responsive to my inputs, with plenty of power to punch out of maneuvers. Subsequent flights at 1800 rpm found my flight times increasing, and I've gotten into the habit of flying half my flights at 2200 rpm and half at 1800 rpm, switching back and forth throughout the flight. This has added at least a couple of minutes to my original four minute flight time!

I plan on pushing the Goblin a little more on the low end, and experiment to see just how low I can take the head speed. I've seen people have great success with head speeds as low as 1600 rpm, so I will give this a try soon and see how it does. I was very pleased with how my Goblin flew after the conversion, anything that gets me longer air time is a plus!

In the video below, The flight starts out at 2200 rpm, and you can hear it drop down to 1800 rpm towards the end. I dropped in some numbers on top of the video to show you exactly where the switch is. Even at 1800 rpm, the Goblin still felt like an incredibly agile machine.

Youtube Link


The head conversion is definitely something worth doing. I enjoy being able to fly with the high speed, and then slowing things down for some quieter and more graceful style flying. The biggest bonus to me is the increase in flight time, while not feeling like I had to sacrifice any of the Goblin's flying ability. It's definitely a great addition to my Goblin!

Lower RPM'sNone yet!
Longer Flight Times
No Wobbles

Last edited by CSpaced; Jan 22, 2013 at 11:38 AM..
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Nov 19, 2013, 11:26 PM
Registered User

here is the goblin in flight again

SAB Goblin 700 3D RC Helicopter (4 min 11 sec)

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