600 My T-Rex 550 Rebuild

[trainrider06]

Phil back last spring I crashed my 500 and it essentially did the same thing!
I originally thought that I had just let it get too far away on a sweeping banked turn. (The heli seemed not have any control, and continued to drift out toward a lake, as I tried to correct it nothing seemed to be working)
Then all the sudden it turned away from the lake and I seemed to have control, I started bringing it back, and again seemed to loose control, this time at least it wasn't headed over the lake but it was over land, it just kept loosing altitude until hitting the ground going forward, and did a very nice end over end roll a few times. That was expensive! But I discovered that my ESC I was running kept cutting power to my servo's.

 

[Smoggie]

This is where the data logs come in really handy. I tend to default to blaming my dumb thumbs when things go wrong. Most often that is the cause but this last time when i was having trouble with my Agile 7.2 i checked the Vbar log and found this:

2:33 Satellite Data out of synchronization
The connection to the Satellites has to be resynchronized after some packet losses
2:34 Satellite Data out of synchronization
The connection to the satellites has to be resynchronized after some packet losses
2:34 Satellite Data out of synchronization
The connection to the Satellites has to be resynchronized after some packet losses
2:37 Satellite Data out of synchronization
The connection to the Satellites has to be resynchronized after some packet losses
2:39 Satellite Data out of synchronization
The connection to the Satellites has to be resynchronized after some packet losses
2:40 Satellite Data out of synchronization
The connection to the Satellites has to be resynchronized after some packet losses
2:41 Satellite Data out of synchronization
The connection to the satellites has to be resynchronized after some packet losses
2:41 Satellite Data out of synchronization
The connection to the Satellites has to be resynchronized after some packet losses
2:42 Satellite Data out of synchronization
The connection to the Satellites has to be resynchronized after some packet losses
2:43 Satellite Data out of synchronization
The connection to the Satellites has to be resynchronized after some packet losses
2:44 Satellite Data out of synchronization
The connection to the Satellites has to be resynchronized after some packet losses
2:45 Satellite Data out of synchronization
The connection to the Satellites has to be resynchronized after some packet losses
2:47 Satellite Data out of synchronization
The connection to the Satellites has to be resynchronized after some packet losses
2:48 Satellite Data out of synchronization
The connection to the Satellites has to be resynchronized after some packet losses
2:49 Satellite Data out of synchronization
The connection to the Satellites has to be resynchronized after some packet losses
2:50 Satellite Data out of synchronization
The connection to the Satellites has to be resynchronized after some packet losses

And it went on like that for page after page of the log.. i was really lucky not to crash.

 

[trainrider06]

Wholly crap! Scary! I wonder how often these issues go on and we never know, till one day....

 

[Heliman450]

Hi Steve, very interesting. I'll spend some time making sure I understand the logged data better and routinely have a look at it between flying sessions (if I can use that phrase?).

What did you notice about the heli's behaviour that alerted you to a possible problem?

Off to ask a question in the Tx. area,
Bye for now.

 

[Smoggie]

I'd noticed a few slight 'glitches' of the servos while flying that made the heli twitch. This happened a few times and I wasn't sure if it was just me. What finally alerted me was that the heli briefly lost power, just for a second. The power came back and I brought it quickly in to land, then right in front of me it did a couple of big 'glitches' and I knew this time it wasn't me.

I'm still not 100% sure what the specific problem was. I replaced both sats and both sat cables and repositioned the sats. I also added two 4700uf capacitors as a voltage buffer because the Vbar with sats is very sensitive to fluctuations in the supply voltage and the capacitors help dampen those fluctuations out. One of these changes did the trick because there are no more glitches and the log is error free.

FWIW here is some of the testing that Mikado did that shows the benefit of the capacitors against sudden high demand from servos: Power supply | VStabi

And also to dampen out sudden voltage spikes due to back EMF from servos: Reverse current of the servos | VStabi

I dont really think my problem was due to voltage fluctuations because the log didn't show any, but the capacitors cant do any harm, and I had some in my box of junk anyway.

 

[Heliman450]

Hi all, just a quick update.

My almost new DFC head from Steve is sitting in Swiss customs where it's been for almost 5 days. Full marks to the U.K.'s Royal Mail delivery service for getting it to Switzerland in 3 days as declared to Steve on posting day. I've received part of my order for the other bits from my local hobby store but there's still one thing with possibly a 2 weeks' delivery period

I'm wondering whether I'll be back in the air with it before the winter snow comes

 

[Heliman450]

Hi all,

Parts have arrived and all looking good. Let you know when I start the re-build.

 

[Heliman450]

Hi all, a quick update.................

Began the strip down this morning and discovered that there is a different one-way bearing set needed (#H60200) for the new main drive gear. Also, a tail servo mounting screw is missing on one side. Closer inspection shows that the plastic mounting for the tail servo is not very good and simply inserting new screws won't really be good enough, so a metal unit is on the list (#H55023). They aren't in stock at either of my local suppliers so it looks like an order will have to go in.

The main bearings are completely shot, so the new ones seem long overdue in that case. I can't say that they suddenly went noisy, but it must have been a gradual deterioration, which I didn't notice. I'll change them out again in the not too distant future.

Looking good but you never know, maybe there's something else waiting to bite me

 

[Tony]

In this hobby, I think there is always something out there to bite you lmao. Have you tried just cleaning out your bearings? A lot of times, the bearings will get dry, the grease that was in them gets hard, and small dirt particles will get in there making you 'think' the bearings are shot when all they really need is a good cleaning. The video below is how I clean all of my bearings. My skin is a little tougher than most people out there, so if you do it this way, wear chemical gloves unless you are like me and have hands of steel that are very hard to receive chemical burns.

How To Clean Bearings The Easy Way - YouTube

 

[Heliman450]

Good idea, I've seen the video before (a while back now). What about the new lubrication?

 

[Tony]

I use Team Trinity Bearing Oil. The stuff that I have is quite old now because you just don't use a lot of it. What they have now is called Royal Oil. It's a thin oil made for brushless motor bearings and wheel bearings for both on road and off road cars and trucks. However, it works perfectly well on a helicopter as well.

I'm not saying to run this stuff, it's just what I use. You can use just about any thin, light weight oil on these bearings including 3-1 oil or the like. I just trust the Trinity brand since I have used it since day 1 when I got started in Rc.

Royal Oil

 

[Heliman450]

Hi Tony, thanks for the tip and the reminder for the video. This morning, I bought some equivalent stuff. This afternoon, I fell in love...............................

Modellsport.ch | Velos Rotors 880 | online kaufen

The new 'love' in my life. I saw a completed example, truly awesome!

I only went there to talk to Hugo about the communication problem between my Spirit Pro and Jeti REX7 Rx. and I'm pretty sure that I've found the next heli to join my 'fleet' when I improve my flying skills some more.

What do you all think of it?

 

[Smoggie]

Yeah, the Velos is a beast, two motors, two ESC's four batteries, what a machine!

Not something you can build on a budget though!

 

[Heliman450]

Yeah, the Velos is a beast, two motors, two ESC's four batteries, what a machine!

Not something you can build on a budget though!

When the budget works out less than a turbine-powered scale heli, it works for me

It would also fit into my existing vehicle so thinking positively, the budget is massively reduced, hey, I could buy four of them for what I was thinking to spend!

 

[Smoggie]

Bear in mind if you havent already that the 2,000 CHF is for airframe and blades only. This isnt the sort of heli you would want to 'cheap out' on as far as electronics and motor etc is concerned, so the airframe cost is just the starter. I'd guess another 3,000 CHF to kit it out with good quality kit and just a single set of batteries.

It is a truly awesome heli though. A guy on one of the other forums says that they are quite overpowered with two 700 size motors so he used two 600 motors and battery sets, making it a lighter build. He says it still had tons of power.

 

[Heliman450]

Bear in mind if you havent already that the 2,000 CHF is for airframe and blades only. This isnt the sort of hely you would want to 'cheap out' on as far as electronics and motor etc is concerned, so the airframe cost is just the starter. I'd guess another 3,000 CHF to kit it out with good quality kit and just a single set of batteries.

It is a truly awesome heli though. A guy on one of the other forums says that they are quite overpowered with two 700 size motors so he used two 600 motors and battery sets, making it a lighter build. He says it still had tons of power.

Yes, I worked out the kit content/price. Not a bad estimate on your part for the full build either, I think. Good tip on the motors especially as I never expect to throw it (or any other) around the skies as per their video. There's probably a saving on the ESC's, too.

 

[Heliman450]

Hi all, back to my T-Rex 550 rebuild.....................

The heli is all together and checked out with the transmitter (Jeti DC-14) and everything works how it should. It just needs me to go through a new setting up process with the Spirit Pro. So what did I do so far?

1. Steve (Smoggie) did a deal with a little used DFC rotor head, which reduced the overall cost of the conversion/overhaul. I can still revert to the previous arrangement if I want to.

2. The 'new' rotor head has a different anti-rotation arrangement than my old one, so I had to change over one of the balls. I took great care to heat up the parts to be removed before trying to unscrew them (I've already made that mistake once in the past).

3. I was changing over to a bevelled main gear, why? Just because I like them better than straight-cut ones (the old one stripped).

3a Problem #1! The new pinion is much bigger and the helis have a different mounting plate for the motor. The solution lay with making the slots a little bigger with my trusty Dremel so that there's enough play to allow adjustment of the motor position.

3b Problem #2! The new pinion was very close to the mounting screws. The solution was to use thinner washers (I didn't measure the difference).

3c Problem #3! The pinion is too wide to go through the hole in the mounting plate. (Do I really want to go further with this or just buy a new, straight-cut main gear??), no - stick with it. The solution was to remove the mounting plate and the battery mounting, fit the pinion and trial-fit the grub screws. That works but I must remove the whole plate and motor together in future. Actually that makes the job easier anyway. I think it's a pain in the neck trying to get the screws in with the original arrangement.

4. During my test of the functionality it's obvious that the pitch isn't zero degrees at 50% stick. It looks like the link rods are too long and don't have enough thread to shorten them and bring the swashplate down a bit. This is tomorrow's problem so any feedback on the possible solution(s) will be much appreciated. I have a set of links for a 700 DFC heli, but the ball links are too big to fit the 550. Are the rod links the correct length and would a set of 550 ball links fit? Don't know yet.

Over to my friend's DX6/Blade 450 problem

 

[PLANETGETLOW]

I just sold 2 helis from my fleet and bought a 550. It has custom built frames, nice clean wiring, Talon 90, BeastX FBL system and overall is just a very rigid heli. I'm picking it up today hopefully.

 

[Heliman450]

I just sold 2 helis from my fleet and bought a 550. It has custom built frames, nice clean wiring, Talon 90, BeastX FBL system and overall is just a very rigid heli. I'm picking it up today hopefully.

What did you sell? I don't have a big enough 'fleet' for that to worry me

 

[Smoggie]

Yeah, the joys of upgrades and conversions! The motor moiunt from the later version of the 550 would probably have solved the pinion problems, though i'm not sure if the frames changed too at which point it probably becomes a new heli rather than an upgrade.


The DFC head sits lower and the swash sits lower on the shaft too, so you will need shorter links on the swash servos. The links from the 550DFC 'should' fit, I think.