Help please URGENT advice on tail boom needed?

[gramey]

I may be about to ask a really stupid question but having assembled my tail boom onto my heli I didn't notice at first that the torque tube is not engaging properly at both ends. If you turn the head the tail blades rotate only as long as there is absolutely no resistance in their way. As soon as you put your finger in the way the torque tube starts skipping over the drive so it appears it's only just engaging at one end or the other.

The two clamps at the front end have a ridge and I've got the tail boom butted up to these and the tail gearbox fully home so the locating screws will go in. If you put the tail boom past the ridge in the two clamps then it spreads the plastic clamps and is nigh on impossible to fit between the main frames.

I dismanteld it and measured the tail boom as 33 inches and the torque tube at 31.5 inches. Now I know the tail gearbox and front drive slide into this so that would account for some of the difference but is one of these too short or too long or am I doing something wrong?

Sorry it's such a long thread but I rellay need to try and sort this out for obvious reasons. Any advice is greatly appreciated, thanks.

[Bobbyk]

It sounds like the TT is not fully seated, but the boom is longer than the TT, the best way is to assembly the tail end first, the plastic clamps has an orentation they go in, the ridge face forward and holds the boom in place so the boom dont push forward in the boom.

Hope you get it sorted

Thanks

Robert

[ddavison]

Just checked my tail boom and torque tube and they measure the same as yours 31.5 and 33. Lets start at the rear first, there is a cutout(notch) on the end of the tube that goes to the rear(t/r end) the tail rotor gearbox has a protrusion on the output side that goes into that notch. Make sure you have the gearbox seated fully into the tube. Slide the torque tube fully into the tailboom and into the tailrotor gearbox coupling. Loosen the four bolts that bolt the front mounting block to the frames. Make sure the block is mounted with the ridge toward the front. Slide the tailboom into the front mounting block holding the tailrotor so it does not turn, turning the maingear back and forth to get the torque tube coupling to seat. It should hit first then slide into place. Dave

[malc1]

Mine gives you 5-6mm from the ball on the end of the Tube drive to the end of the boom with it fully inserted.

Looks like mines 31.5 as well.

David - no notch on my boom,is that a new design then?

[gramey]

No notch on my boom either, having dismantled my boom I re-assembled it by first attaching the tail gearbox and then inserting the torque tube. I didn't pay attention to which way the TT went in when I first assembled, it looked the same at either end, it but this time I made sure the orientation was the same as shown in the drawings. I pushed the TT in whilst turning the tail rotor until it slotted in before re-installing it into the frame. This time everything is rock solid with no slippage although obviously I cant see how far the TT has mated into either end.
Whilst I had it apart I did remove the shim which people say you don't need with the closed gearbox. I'm pretty sure however that the thickness of this shim is not the reason why it now works. My only concern is whether or not there's any possiblity of the TT moving and me losing drive to the tail, but perhaps I'm being paranoid!
Thanks for the replies and taking time to measure bits etc. it's appreciated.

[malc1]

Mines all together Ok .

BTW I emailed MA last night to get them to send over the correct length of tube drive to go with the 33" Spectra boom incase you didn`t get a reply.

They say its 31 3/8 inch long - more or less as per Davids post.

Sorted then.

[ddavison]

Okay you have the new split tail rotor gearbox clamp with the four screws in the rear. There are two bolts that go through the clamp, tail boom and thread into the gearbox. There is no notch with that one. I was just rebuilding the Stratus which has the older style clamp and three bolt gearbox. Glad yours is working OK now. Dave

[malc1]

David

Have you done anything to stop the boom moving in the clamp?

I was thinking about running a short bolt in one side when I do a bit more tomorrow..

[ddavison]

Are you talking about the front clamp ? If so yes drill and put a small screw in.

[malc1]

Yeah Dave the front one.

When the slow setting JB Weld on the boom supports has set tomorrow - I`ll look at getting one fitted.

[gramey]

I've seen it mentioned that some frame sets have a PEM thread in them which you can utilise to drill a small hole and clamp the tail boom. My frames do not have this so how do I go about locking the boom in? Also if I need to drill the frame, clamp and boom to lock it in do I need to dismantle it all before drilling? I'm thinking the debris will fall inside the boom when I drill but perhaps the amount would be insufficient to cause any problems..
Failing that do I just put CA glue in as opposed to drilling?

[pgkevet]

If you're going to drill it then do it properly..mark your drill hole position in the front mounting block.. pull the tail..drill your primary hole, clear any debris.. refit boom..mark through, pull it..pack it, drill it, tap it (or use a self tapper) then refit and fix.

From someone who has stacked his Spectra too often I can tell you it isn't worth having these thing go down due to silly mechanical issues. Pilot error is bad enough!

[gramey]

Thanks for that, I'll do as you suggest as although it's a PIA to pull it apart again, it's better than having swarf inside the boom that will simple act like grinding paste if it came into contact with the bearings.

[pgkevet]

coincidence but got to putting the boom back in on my rebuild today and had to also drill a safety screw..tapped and threadlocked it holds well...