Building the Fury Tempest FAI - Page Two
Rubber inserts are installed into the top of the fan which marry up with the bottom of the clutch. I've not seen this kind of arrangement before, but can immediately see it's merits in going some way to isolate engine vibrations.
Collets are supplied for both OS and YS engines. In my case I'm installing an OS 91 C-Spec engine.
The Xcell clutch systems do not have a one way start bearing like the JR machines so I've purchased a one way hex start shaft. The last thing I wanted was to have two different starting systems for my helis. A hex starter adapter is available from MA, but I have to wonder why they don't include it as standard given the popularity of the hex start system?
Comment has been made by others about the small size of the clutch in comparison to the large JR helicopters. I would have to agree that it does look small in comparison, but as I have not heard of any Xcell clutch problems, I'll just wait and see.
The clutch assembly then installed into the frames. What I found VERY cool was the use of a subframe assembly to mount the clutch block into the frames which made alignment a non-issue. This subframe had '7.66/7.75' stamped on the side so it would seem that when you change gear ratios, you get a new subframe which is fine by me! After going through the pain of installing new gear ratios into the Vigors and trying to sort out alignment, this was bliss!
Fitting the engine to the machine was a little tricky at first. The 'engine bay' area isn't as large as say the Vigors and putting the C-Spec in required a little gentle giggling, but nothing too drastic. Mating the top of the fan to the bottom of the clutch requires a little bit of effort to start with to get the pins and 'ball' assembly into the fan. This is aided however by a little vaseline on the rubber sections. Subsequent removals and fittings of the engine have proved less of a hassle.
What was more annoying was when it came time to fit the shroud finding that it didn't fit correctly around the C-Spec head (ie the head was too wide). It's not so bad that it doesn't totally fit, it's just now it's splayed out at the bottom.
I also had to take a hobby knife to the inside of the shroud to create an opening for the carb (which wasn't there).
I'm not sure what happened here, but as the C-Spec has been out a while now I would have thought the shroud would have been more accomodating. I am hoping I am proved wrong on my thoughts on the cooling system here, but at the moment, I feel that in this respect at least, the Vigor has the Tempest over a barrel.
I was a little worried about fuel starvation issues with the tank line coming in from the side, however there are bigger and better pilots around than I and they obviously aren't having any issues!
Attaching the rotorhead to the mainshaft is another dowel pin with a grub screw. In addition there are two bolts that attach from either side to 'clamp down' on the shaft. Very nice.
Tail rotor grips/pitch slider
The pitch slider is very smooth with small bearings in each arm that attaches to the tail rotor grips.
I made sure I read and re-read the instructions to make sure I knew what was up. With the instructions making frequent use of the words 'Red and Green loctite' I knew there wasn't going to be much of a chance of recovery if I got it wrong. It was off to Darryll's for a group conference on how the gearbox was to go together. Darryll is more mechanically inclined than I and fixes my mistakes on a regular basis.
You assemble the output and input shafts seperately then slide them into the metal gearbox. The output shaft is prevented by slipping back out by a circlip and a retaining ring which you tighen up inside the gear box until there is no free play. The input shaft is then inserted and the gear mesh is set. Now the problem here is you have to do this by 'feel'. You cannot see the meshing of the gears. With the Vigor CS's, there is a pretty large inspection hatch which you can open to see what's going on.
Once the mesh is set, a small amount of grease is applied through a small hole in the box, you then install the assembled pitch slider mechanism onto a bell crank support which bolts to the outside of the gearbox.
From there the tail rotor grip assembly is attached to the output shaft by grub screws that have protrusions that lock into the output shaft. Very similar to the Vigors.
The shaft drive (already assembled with the dog bones on it) is then fed through the boom. This proved to be much easier to do than the equivalent action on the CS.
The assembled gear box is attached to the boom behind the vertical fin mounts where it fits into the slotted sections. short Philips screws and a bolt gripping the mount secure the mount to the boom. The gearbox is screwed into the back of the boom resulting in a solid attachment of the gear box to the boom. Both horizontal and vertical carbon fins are attached at this point.
The carbon boom supports are attached to the horizontal fin mount and the main frames by the most beautifully machined ends you can imagine which thread onto inserts which are expoxied into the supports. They have a two degree offset in them to help with fitting. Unfortunately, I was only supplied with two of the four ends I needed. Luckily my mate Darryll had brought a new mill and was keen to see if he could make suitable replacements. We had envisioned that these would be a temporary measure until the replacement ends turned up from MA, however Darryll's support ends turned out so well I decided to fit them permanently. I also fitted a aftermarket boom support bridge.
The tail rotor pushrod is a thick, stiff carbon affair which also has threaded inserts expoxied into it with ball links threaded onto each end. Protecting the pushrod as it goes through the boom guides are two clear plastic shrink tubes which once positioned are 'heated' into place. The result is a much 'freer' action which is easier to get right than the CS setup.