Well, I started the new Caliber this weekend. I was away on business in California when it showed up at the house on Tuesday, and I wasn't due back until late Saturday
After daydreaming for a week about it, I finally got my hands dirty on the kit. Actually, dirty is a quite figurative word, as this kit is just the opposite. I have never built a top-end machine like this before, so I wasn't sure what to expect in the kit. What I found was beauty and precision all around. From the machining to the anodizing, this kit is a work of art.
I have in my hip pocket, access to some of the best pilots in the world: Wayne Mann, Dwight Shilling, and Cliff Hiatt. All three of these guys are flying this machine in F3C competition, and all three were on the US team at the 2007 Worlds. Wayne has especially been helpful in lending secrets to success, and even a few trick parts, to make sure this machine would fit even his standards for competition. My thanks to him for all the support he's already offered me, and for what I may need in the future.
What is a Caliber 90?
The Caliber series of competition helicopters goes back quite a few years starting win the Caliber 60. The machine has evolved over the past 10 years into the precision machine you will see born on these pages. The machine itself has some departures from the ordinary helicopter, such as belt drive, two-stage reduction transmission and axial flow, belt driven,ducted fan cooling system. The tail is belt driven, as is the main transmission via counter gears. The belt drives, three in all, make for a very smooth, quite transfer of power from the clutch, while dampening nearly all engine pulses. This helicopter is about as close to electric smooth as any nitro can get. The frame design is modular, stacked carbon plates built around a central frame case made of machined aluminum billet plates bolted together. These plates contain the bearings for the transmission and main shafts. There is no setting of gear mesh, everything bolts into place. The design is extremely rigid, albeit a little more weighty than the modern 3D bird. The main frame assembly is quite long, too, bringing the appearance of a much larger bird than a 90 Nitro.
The head design is unique in that you can set the damper hardness at any time without taking anything apart. Large, anodized squish rings are threaded onto the head yoke assembly that adjust pressure on the dampers as you tighten or loosen them. This allows you to adjust the dampening to your liking. You can adjust dampening to suit your desired head RPM, rather than the other way around, and you can experiment with different settings much more easily at the field. The head is also very large, however you can still run 720mm blades on this machine without interference. The Bell/Hill mixers are also a little different than most other helicopters, and are optimized for precision flying. The pitch control is eCCPM on this helicopter, with options for both 140 and 120° CCPM built into the kit. I chose for the 140° option, which requires the installation of a few minor parts to relocate the left and right T-levers.
Off to build.
First, the inventory of the kit is completed. Each sub-assembly is contained in it's own bag of parts, as like most other kits. One thing to be careful of - you may not use all the hardware from a bag before moving on to the next step. So keep tabs on your hardware. Here's the layout from the box:
The first step is to assemble the transmission ladder frame structure. This is the unit that contains the shaft bearings, and carries the primary transmission stresses. This "torque box" is what the helicopter airframe basically hangs from. It's simple in design, and extremely rigid. Each peice is machines from a solid aluminum billet about 1/4" thick.
After building the ladder frame structure, you bolt the two upper carbon frame plates to the sides, using a few spacers along the upper front portion. No big hassles here, just be sure to compare proper bolt lengths. Some are 3X6 and some are 3X8, so look over the diagram carefully. This is actually quite common throughout the kit.
Wayne Mann suggested that you do not LocTite the frame structure bolts, nor the canopy mounting stays. In the event of a crash, some bolts may shear off, and removing the LocTited remains is very difficult. Wayne doesn't have issues with any of these bolts coming loose, if properly tightened to begin with.
This kit actually has a lot of pre-assembly to it. Most bearings are already mounted and secured in place, such as the mainshaft and counter gear bearings in the Ladder Frame, and flange bearings in the upper side frames. Even the head is assembled, ready to install the flybar components.
Next you assemble the autorotation hub and counter gear pulley. This is another unique feature to this helicopter, in that the auto bearing has only a fraction of the load as does most other helicopters. This is due to the fact that the auto bearing is in the counter gear pulley, not the main gear. This allows a tremendous mechanical advantage to the auto bearing. The system also allows the ommision of a secondary tail drive gear. The tail drive pulley is mounted to the counter gear center shaft, which is always geared to the mainshaft gear. Speaking of maingears, take a look at this beauty! Again, masterful machining from solid aluminum billet forms the maingear center hub, with a CNC Delrin ring gear bolted to the circumference with 12 2X6mm bolts. This is pre-assembled at the factory, as well.
Next you install this auto-rotation/countergear/pulley assemnbly into the ladder frame, along with the primary drive belt, maingear, and mainshaft. You may notice a position for a third, center mainshaft bearing, and Wayne suggests utilizing it. This third bearing is not supplied in the kit, and requires a small bolt to capture it if you use one. Also, find and use a 25mm shoulder bolt through the maingear hub, as Wayne reports two failures of this bolt using the new YS 91SR engine. He also says that he's never seen such a failure of this bolt with the YS 91ST engines, however. I think it's good practice, with any engine, on a machine of this class.
Before moving to the lower frames, you mount the fan unit into the upper side plates. This is a neat system that uses a V-belt drive from the start shaft on the engine. The fan is a small, five bladed ducted unit that sits directly above the cylincer head. To give you an idea of how much air this thing will move...it's on a 1.3:1 speed-up from the engine shaft. So if you're engine is spinning 16,500 rpm, that fan is spinning over 21,000 rpm. Given that, make sure to put your fan assembly on a High-Point and balance it. Mine had one heavy blade that required a little trimming. Also, red LocTite the bearings to the center bushing, to prevent spun inner bearing races.
Now it's time to move onto the lower frame assembly. This is typical of stacked frame designs. Two vertical side plates of carbon are joined with spacers, plates, and bolts. Again, make sure to keep tabs on your hardware. Different lengths are called out in the drawing, so pay attention to exactly where they intersect. When assembling the lower plates to the bottom fuel tank mount plates, make sure you have the correct orientation of those plates, with the inner flanges of the tank support grommet holes towards the bottom. Some very nice lower rails anodized gold are bolted along the bottom of the side plates for rigidity and to spread the load of the bolts across the carbon plate.
Then, you move onto engine setup, with the installation of the clutch adapter, clutch, clutch bell, and start shaft/pulley. Unfortunately, the kit only comes with a clutch adapter for OS engines. Since I will be using a YS, I have to wait for a YS adapter to come. Therefore, I am skipping the engine install portion for now.
Then build up the fuel tank, and drop it in place between the rear lower frame plates. Next comes a tedious step of joining the upper and lower frames together. Again, typical of stacked frame designs, lots or spacers and bolts are used, as well as some plates. Again, lay off the LocTite here, and nicely snug down all the bolts. You know by now to keep tabs on your hardware. You should have a couple small piles of hardware by now, also, especially if you skipped the engine install like me, to wait for a YS adapter.
The landing gear is assembled and installed onto the frames. This is a very typical setup, with the exception of rubber isolators between the mounting locations on the frame and the skid struts. This reduces ground resonance and "vibe walking" if you fly off improved surfaces.
Moving on, you then assemble the swashplate, T-Levers, and washout unit. Again, lots of pre-assembly done. All bearings are pre-installed, and all the balls are on the swashplate. I had to remove the two left and right balls for the 140° option, but that's painless. The washout arms are actually supported by two ball bearings at the swash driver arms. That is a very rare feature, found only on very high end machines. This makes for a silky smooth cyclic action from the t-levers up. There is also an adjustable phase ring, so make sure you set that centered to start with.
The head is pre-assembled as well. All that's required is to install the flybar, control arms, and mixers. This machine uses these tiny little flybar control arms that would look small on a T-Rex. They work, though, and make sure you have them parallel. Next slide on the mixers and mixer keeper collars. Afterwards, the head is bolted to the mainshaft. This uses a threaded through-bolt and two pinch bolts. To get the head to sit true on the mainshaft, I smoked down the through-bolt, then secured both pinch bolts simultaneously. I spun the head by hand and stared at the head button for any eccentricity. I still have to rig my dial-indicator to it, but with my MK-I Government Prescription Occular Devices, it's pretty straight.
As of this writing, the farthest I have gotten is the building of the tail gearbox. Actually, there's no gears in it, but nonetheless...
It's a very simple structure made from two aluminum peices bolted together. The tail shaft is very easy to remove and re-install in the field, and the tail pitch control bellcrank is a work of art. The bell crank utilizes upper and lower links attached to the pitch plate, which itself is double ball bearing supported. The system is actuated by a push/pull system from the front of the tailboom via boom mounted servo.
That's all for now...more to come later this week as I get some parts needed to finish up.