Written by Tony Chaveiro Friday, 18 April 2008 00:00
One thing that has always annoyed me on my T-Rex 600N is the fact that Align decided to use plastic bearing blocks on a pure blooded 3D Machine. We all know that rigidity isn't exactly the 600N's middle name and the plastic blocks are not helping at all. If one also takes into account the sloppy main shaft tolerance (the main shaft diameter is undersized – 9.83mm), then it becomes quite clear why the entire airframe basically rocks back and forth and side to side when we apply some pressure on the helicopter's head.
I searched for a couple of weeks on the Internet, looking for alternatives. I found several manufacturers that were offering upgraded metal bearing blocks (Align included) so it ended being a matter of choosing the one that seemed to offer the most benefit. The Align's were immediately excluded because of their weight and my “no second chance” theory (read my QuickUk Swash plate review). I ended up getting a set of MaxPro's metal bearing blocks and a set of G-Force's Thrust Bearing Blocks. Why did I get both sets? Well, although the G-Force Blocks seemed clearly superior, the MaxPro's come in a set of 3. This means that I could use the 3rd Maxpro bearing block together with the G-Force setup.
Once I had both products in my hands, I looked extensively over the quality of the manufacturing process, the ideas behind the design and obviously... weight.
There isn't much to say about the Maxpro units. They come in a plastic back without any special packaging and bearings aren't supplied either. Their biggest strength is the low weight (see picture 4). The finish is of a simple black anodized color. The format is quite traditional and just as their plastic counterparts (Align) they have two rectangle shaped inserts to line up with the frames. The stock bearings must be pressed in and a little of green loctite applied so the bearings don't start to spin inside the blocks. The main benefit I've found is that all 3 bearing blocks together weight 0.5gr less than the Align plastic blocks and yet they provide increased rigidity over the stock units.
The G-Force units are in a different category. I was deeply impressed by the quality finish. I think many manufacturers could benefit from learning something with G-Force's type of finish. I'm sure that if I would place them in a jewelery display, they would blend in just fine...!
The packaging is simple but care has been taken to keep the thrust bearings in place (see picture 1). Their weight is lightly above the stock plastic units but still much less than the Aligns upgraded metal bearing blocks (see picture 3 and 4).
In terms of design, the G-Force units seem to be from another world. I was a bit skeptical about the real benefit of using thrust bearings in the main bearing blocks but I'm glad I was wrong as you will see further down in this document. The pure solid design appeals to me very much and even though they are in fact very light, the design itself looks quite sturdy and beefy.
In terms of comparison, here is a set of pictures of the different bearing blocks on my precision scale:
All in all, the obvious conclusion is that if you just want to save weight (0.5gr total) with added structural rigidity, the MaxPro bearing blocks will do the job just fine. They aren't cheap though so everything comes down to the price you're willing to expend. I can hardly justify $60 US Dollars for a 0.5gr weight save but opinions may vary. The only reason I got them was to get my hands on the 3rd metal bearing block which is something that neither G-Force and Align are currently providing. Maybe in the future, G-Force will provide us a 3rd metal bearing block. I'm fully conscious that performance wise, you don't actually need it but its always nice when you're able to replace a plastic part with metal... right?
The installation of the G-Force blocks isn't quite straight forward as one thinks but it isn't difficult either. Before installation, one should disassemble the blocks and grease them properly with either white titanium grease (from Vario) or standard white lithium grease.
Please notice that it isn't required (nor desirable) that the end-user disassembles the radial bearing as it was pressed in using special tools at the factory. This will ensure that the bearing never falls out so one shouldn't mess with it unless absolutely necessary. The actual installation can be tricky because there is nothing that holds the thrust bearings in place and since the 2nd bearing block has to be installed upside down (so that the actual thrust race rests against the top of the main gear's one-way sleeve), you're going to have a hard time unless you follow one of the following two methods:
I was told that this method will be included in the G-Force manual on future batches of the bearing blocks as it is the simplest way of installing the middle bearing block. The trick is to install the middle bearing block first and without any thrust bearing. Once we have accomplished that, the next step is to pickup the helicopter by its head and just turn it upside down. In this position we can easily place the thrust bearing in its place and insert the main gear right afterwards. When we flip the helicopter again, the main gear will hold everything in place until we install the top block and the main shaft.
This method is a little more complicated to execute but will save you of flipping the helicopter upside down if you happen to be working in a tight area and have other components hanging of the airframe. In this scenario you can install the top bearing block first as you will apply a small strip of electrical tape on the bottom of the middle block before actual installation (see picture 6). The electrical tape will hold the thrust bearings in place while you slide in the stock main gear. Once the main gear is in place you can pull the tape off with a set of pliers and everything will lock in place. I personally prefer the 1st method but both do work quite nicely.
Once both blocks are installed properly, we only need to insert the main shaft back into place and tighten down the whole assembly (see picture 7). Don't forget to use blue locktite on the screws that hold the bearing blocks to the frame.
Once you've accomplished this, there is only one small thing left to do which consists in checking the clearance between the elevator arm and the top bearing block. G-Force recommends adjusting the elevator position to achieve the desired clearance but I didn't want to change my elevator link geometry and since only the top of the elevator arm was slightly rubbing against the block, I choose to file the top corner of the arm (see picture 8). The clearance is now perfect for me.
The entire installation procedure takes a little over 10 minutes even if you are extremely careful and slow like myself.
First Test Flights
After everything was installed and setup, I headed down to my field to do some flights and to check if I could notice any differences/improvements over the stock configuration. The first thing I noticed while I was carrying my 600N down to the flight line was that I couldn't feel the head rocking back and forth in the main blocks like it is normal with the plastic blocks (as a side note, it's because of the main shaft's sloppy tolerance that the 600N's main bearings become notchy so quickly). This didn't make any sense since I know that the problem comes from the sloppy main shaft tolerances and there is no way it could be corrected because bearings have stock sizes and diameters. Even Garf at G-Force told me not to expect that his thrust bearing blocks would correct that problem but it seems that at least they attenuate it to a large extent.
After some hovering to check the birds CG and controls, I started to perform my usual routine that consists in some smooth flying mixed with sudden stops, tic tocs, hurricanes, etc. One thing that became immediately apparent was that my collective management seemed to have improved during the night. The helicopter was keeping the head speed quite constant during pitch pumping type of maneuvers (even on just 20% nitro). Since I pretty much suck at collective management, its normal for me loose around 1000-1500 rpm during tic tocs with a high efficiency fan and around 2000 rpm with a high flow fan. I checked my Eagletree charts and I was indeed only loosing around 500 rpm which is quite astonishing. The engine seemed to recover much faster when put under load and the helicopter felt more locked in. That feeling probably was due to the fact that the airframe now has much less flex than before.
One final surprise was when I performed my usual final auto-rotation (with the engine shut off). The machine was somehow much quieter and the hang time became quite unbelievable. I was able to perform a full roll, flare, hover and land without much effort.
All in all I'm very happy with this upgrade and I can assure you that it is worth every penny performance wise.
reduces frame flex
no lateral inserts make it much easier to line up the frames
reduces drag on the main shaft thus increasing engine performance and auto-rotation capabilities
since the thrust bearings take out the axial loads, the radial bearings last much longer
super quality finish. Better than anything else I've ever seen
even unnecessary, a 3rd bearing block (even with only a radial bearing) would be nice
installation isn't straight forward so one actually needs to read the manual
price (even though once you've tried them out you won't want anything else)
I like metal parts even if they are pretty useless performance wise (also known as Bling) however, I think that G-Force has once again hit the nail on the head by supplying a product that not only looks as good as my wife's jewelry but also adds important improvements over the stock part. Anyone that thinks that these upgrades will only add unnecessary weight should think twice because the total added weight is 2.4gr... thats the same as 3 extra inches of servo wire or 5 squashed bugs on your blades(!). The added structural rigidity, the lower drag under load on the main shaft and the improvement in engine response alone justify the price of this upgrade. If I had another 600N, I would have ordered another set right away.
( 4 Votes )