700 700X First Mods

[Heliman450]

Hi all, some photos of my first mods to my 700X. Strengthening the canopy at the mounting points (kevlar patches), adjustable servo arms in combination with a set of 5 turnbuckles to give perfect adjustment without any electronic trimming in the B.D. Axon.

It flies very well!

 

[Smoggie]

Where did you get the arms from Phil? It's worth checking that the arms on the two front swash servos dont hit the metal motor mount stiffener and/or the upper frame member under full travel. To check for contact apply full positive collective then move the cyclic stick around in the bottom left and/or bottom right positions.

Any contact of the arms too the frame will cause the servo to stall and could cause them to burn out, so it really should be fixed.

 

[Heliman450]

Hi Steve, I remembered your previous advice and checked it out. Even though they are a little chunky, they don't touch. I even put an extra degree so the full range is 26 rather than the previous 24.

A friend of ours has his own tool-making business and he made me up the set of four and two sets of turnbuckles. He even provided me with a left-handed tap to help out with the ball link threads. It's much better cutting them than relying on the rod itself. Don't ask the price, it's all custom built stuff in my pursuit of perfection.

 

[Smoggie]

I've been doing a few mods to my 700X so thought I'd jump on the back of your thread Phil if that's ok?

First mod is a new motor. There is nothing at all wrong with the standard 850MX lump but i came accross a Scorpion HKII-4525-520Kv 'Ultimate' at a bargain price and couldnt resist. It fits perfectly and even snugs up tightly to the red alloy heatsinks. Due to the slightly higher Kv compared to the stock 490Kv motor I used the lower gear ratio (12t/112t) gearing option as fitted to the 800DFC. This motor saves about 60g in weight over the standard motor and seems for my purposes to have equal power, several pro level flyers use this same motor so I'm sure it will far surpass any requirements i have of it.

 

[Smoggie]

I also fitted the grip control arms from the new Trex 760X. These new arms are canted downward slightly and are intended to even up the + and - collective travel. As standard I had to adjust end points in the Tx to get even travel which while far from uncommon is a bit annoying.
these are the arms:

And this is the downward tilt with the idea of getting a 90 deg angle between link and arm:

The arms and new turnbuckles fit the 700X perfectly and work as intended in sorting out the geometry. Here they are fitted:

This is IMHO a good upgrade if you are fussy with achieving optimum setup. The arms also come with proper turnbuckles that make finer tracking adjustment possible rather than the stock links that have right hand thread both ends. I dont know why Align havent been putting these arms in the 700X kits?

 

[Heliman450]

Sounds great but the colour sucks alongside the red

 

[Smoggie]

Finally I replaced the tail servo after the original Align servo developed an intermittent fault. Randomly it would 'stick' in position, a nudge of the control rod would make it jump to a new position then eventually after a couple of 'nudges' it would start working again. This I think explains the crash I had on the first outing of the heli last year which i never really got to the bottom of. These intermittent faults are hard to pin down, the servo has been fine for a year then a couple of weeks ago started to play up while preparing the heli for flight.
Thinking a dirty 'pot' I stripped the servo and dismantled and cleaned the pot and since then it's been ok but as the fault was intermittent it's hard to say if it's truly fixed, so i got a new servo. I went for one the the brand new 'hall effect' KST servos (KST MS1035) so no more problems with pots (if that's what it was)!

 

[Heliman450]

After spending a small fortune on my custom bits, I decided not to make any more mods to my 700X. Now that you've burst my bubble on the Velos Rotors 880, I'm a bit lost where to go next.

I'm thinking that consolidation and advancing flying capabilities will be top of my list for next year. A lot depends on whether the pound can pick itself off the floor following Brexit.

 

[Smoggie]

Sounds great but the colour sucks alongside the red

Yeah, the colour coordination does leave something to be desired but not much can be done about that. 'Chrome yellow' is the Scorpion trade mark colour that they use on all their motors. I'd prefer it if they made motors and servos in 'neutral' colours (black or silver), but it's not something i get too excited about.

On the positive side it does pick up the yellow in the canopy!

 

[Heliman450]

The tail servo story is interesting........................... both my T-Rexes show what looks like a slight twitch but I don't have the feeling it's that bad as to be construed as sticking. I had considered changing them just to be on the safe side though. What would you recommend for the 550?

 

[Smoggie]

Phil,

This problem I had was quite extreme. The servo would move to and 'stick' at full travel, it would then be totally unresponsive to input from the Tx. If I nudged the control rod it would 'jump' to a new position but remain unresponsive to Tx input. After a few nudges it started working again. This fits perfectly with the symptoms i had when i crashed on first outing (uncontrollable pirouette) but as the servo was working normally after the crash at the time I didn't suspect a bad servo.
A slight 'fidgeting' of the tail in the hover is something different and is most likely due either to FBL setup or a little stickiness in the tail linkages. It's actually very common and if you are running low headspeed might be something that you just have to live with. I wouldn't see this on it's own as reason to change the servo, but you might check that the servo doesnt have too much 'slop' in it's gear train as this could be a cause too.

If you were in the market for a new servo for whatever reason the KST brand do offer great bang for buck and are very reliable. The 'basic' HV brushless BLS815 on cyclic and BLS805X on the tail work great at a price that's hard to beat. If budget is not a consideration then the options are wide but MKS has the reputation of being the Rolls Royce off servos.

 

[Heliman450]

Hi Steve, thanks for keeping 'on the line'................ so close to Xmas, too. Impressive! I only really mentioned it to sound you out. A friend at the club has a T-Rex 450, which also twitches in a similar fashion. All three helis have different gyros and my two haven't shown any deterioration since reducing the head speed. It was just one of those annoying little things that given time, can become a worry or even personal recrimination for not having taken some action when the heli is a broken heap of bits after the crash

Have a good one and a prosperous New Year if we're not in the Forum before then.