help with compatible feathering shafts and DX7's

[chansen1953]

Hi guys,
I broke my std BELT CP head up too much, so I thought it might be cheaper to drop in a metal CNC head I purchased along the way. I think I am sorry I did now !1
I bent the feathering shaft, and now it seems to be difficult to find suitable replacements.
the shafts in this case are 3mm x 48mm, with hollow ends, threaded. The trex 450 ones might fit, but their lenght seems to vary and is not often quote din any aprts descriptions.
copterx is definitely much longer, at 58mm, (that would take a few packets of shims !!!)

Q1. Does anyone know of any other brand /model that uses 3x38mm feathering shafts ??
Otherwise, I may as well toss the CNC and go buy the parts I need otfix the std BELT one.
I do have a complete copterx head, which I bought as a spare for my CX450V2, which has yet to make its maiden flight. however I would need to get servo mounts and do the DTS mods ( planning on doing this anyway, but not today !!)
I am anxiously waiting on my DX7 and 2 x AR7000's to arrive, which I bought off an aussie Heli guy this week.
I Just cannot wait to plug this in and get programming. I presume I read the manual, read the video on dx6 programming swash in the sticky, and the rest will be common sense ??
Q2. Anyone know of any other resource I need to assist my learning curve on the DX7 ??

[copterboy]

Hi Chris, I haven't a clue about DX7's (yet ). But if you have a copterx head, then you can use that, but with the belt-cp swashplate (and swapping the steel balls to align one's on the upper part of the swashplate).

Here's how I did it....and you don't need to do the DTS mod (even though my pics/heli already had it done when I installed the new head). Just use the upper part of the copterx head and some new balls Improves the stability and responsiveness of the heli in flight/hover I found, compared to a cnc e-sky head!!

[exblade]

I have the exact same setup. The Esky cnc swash prevents the problem with the anti rotation pin, and is pretty easy to do. You will need to reset your servo links to get your pitch right. A bit different than the esky geometry on top. Huge improvement on my Belt Cp when I did this swap.

[bigdawg86]

Hey how did you to the DTS mod for your belt cp carbon? I have considered doing that but obviously its a bit different than the standard belt... a link to instructions would be cool. Thanks

[helihathnofury]

The Helifreak Tech-room has several DX7 setup vids; well worth a watch.

[chansen1953]

hi Guys, thanks heaps for the replies.
Well, I have actually got boored over the Anzac weekend (long weekend here in aussie), so I did the DTS mod using the servo trays option.
I have too much +ve pitch now. I have shortened the DTS links as much as can, but still too much +ve. At Zero throttle it is still 5' pitch. I was about to replace electronics with DX7 and AR7000 electronics, so I presume I can adjust this via the TX programming ?? Or should I get it closer mechanically first ??
(If I do this I will have to try and find much shorter Swash/servo links !!) - work !!
Well today, My DX7 Receivers have arrived, so goodbye ESKY electronics !!!!

I will spend the next few evenings seeing if
1. I can adjust the DX7 electroinics to move the swash down- I don't really need 3D mode anyway !!
2. modify the Swash-servo links to be shorter (replace actually !!) and get the heli mechanically correct first , before trying to get it right with my replaced electronics !!

I can guess that the second option will eventually be easier - but hey - I might learn something trying the apparent easier option !!

life's like that !!!

[Luke Warmwater]

Hmm....you need to get it as close mechanically as possible first. 5 degs is a lot to lose through programming! That said, until your Rx and servos are powered up, you can't do any accurate setup.

Firstly, which way up are the servos? If you have the servo arm connecting at the bottom, this maximises the distance between servo and swash. Turn the servos upside down and the connection is at the top. For less "pitch" (and I'll come back to that in a minute), you want servo turned so the connector is at the bottom.

Next, make sure the sero arms are horizontal. Do this with the Rx and servos connected and the motor disconnected. Set a linear pitch curve on the Tx (0% to 100% straight line) and move the throttle / collective to mid-stick. Once the servo arms are as close to horizontal as possible, set them accurately with the sub-trims on the Tx.

Then, connect the servo rods to the swash. The length of these should be set so that:
i) the swash is half way up the shaft between the frame and the bottom of the head.
ii) the swash is level.
....again, all of this with the linear pitch curve and throttle / collective at mis-stick. If your swash is too high, you get too much +ive pitch at mid stick; too low and you get -ive etc. Swash at half way is vital. If you can't achieve this, you have mounted your servo trays too high or too low! There is no work around; the swash must be the halfway point on the shaft or you simply can not get the right pitch range.

Only now can you start to think about pitch! Again, throttle / collective at mid-stick etc. You now use different rods to adjust pitch. Use the long rods that go up to the top of the head. Lengthen / shorten these to get 0 degs at mid-stick.

Good luck!

[Luke Warmwater]

Just re-read your OP and if I understand correctly, you have a Copterex style head, not the Esky!?

99% of my previous post stands....but after you have got the swash at the half way point, you need to work up the head, adjusting the links so that the see-saw arms / washout arms are all level etc. You can then adjust the pitch last of all, with the short arms at the top of the head. Remember, pitch is the vary last thing to do!

[chansen1953]

hi Luke, thanks for the info, very detailed
I currently have a CNC upgrade head, with the DTS mods, using servo trays. Yes, I can turn the servo's over, so arm is lower, which will lower the swash. I do have a Copterx head, but it is a standby - in case I bust the CNC or std belt one up too much to repair.
As I said in another post - I think the std Belt head is actually better than the CNC, which seems to always have something breaking, or coming loose or stripping !!
I will turn the servo over, fit the new Rx/Tx and setup as you suggest tonight after work. will let you know hwo it works out.
Thanks again. probably saved me hours trying to figure it out.

[Luke Warmwater]

Phew...I think that should sort it. This will lower the swash straight away and let you set the swash at mid shaft with zero degs pitch at mid-stick etc!

[CyprusDave]

There was a post somewhere, that when the servos are " upside down", on full downwards travel the end of the servo arm can hit the main gear. I guess it would depend on the length of the servo arm, and exact position of the servo tray, but worth checking.