FBL Gyro Spirit Pro with Three Bladed Goblin

[Heliman450]

Steve, thanks for your suggestions and input. I've committed myself to falling back on Hugo on this one. I have a couple of theories myself but I'd rather hear his opinions before voicing them to him.

Keep up the good work

 

[Heliman450]

Hi all, Hugo cancelled due to a short notice business trip ..................... so I returned to the problem myself as he's not back until Wednesday.

First thing was to start from the beginning, so I hooked the gyro up to the laptop and began with the basic setup, oh no! The gyro was still set to the default setting of 'Horizontal zero degrees' and I installed the gyro 'Horizontal 180 degrees'.

The reason for my mistake was that I didn't recheck after following the Goblin manual's tip to set up the servos' neutral setting before installing them. This was a bit of a challenge as it turned out but it was good tip as there's hardly any space to fit/refit the servo arms when the servos are installed. Of course the mounting of the gyro didn't matter with all the bits on the bench but I forgot to go back and check the setting before going ahead with test hovers #1 & 2. As it turned out it wasn't very expensive but of course extremely embarrassing and frustrating. One mistake that I'll never make again.

Having smashed up one set of blades, I didn't want to go ahead and do-in another set so I made up a new set of three using some blades that were in the bottom of one of my spares' boxes. They were from a collection of 325 mm blades I bought when in Singapore (wooden, not carbon fibre). I figured that I only needed them to lift the heli off the deck, hold a stable hover and nothing more. They worked perfectly

I'm still going to see Hugo Wednesday and buy some new blades together with a spare set plus some upgrade bits. I didn't find out until opening up the packages that the Goblin servo arms are an upgrade together with aluminium servo mounts. I didn't like the standard plastic ones at all. I also need another battery mounting tray as I have three batteries. I'll stay with Velcro fixings rather than the double-sided fixing tape provided as standard but each battery will have a dedicated tray.

 

[Smoggie]

Good that you got it sorted, it pretty much had to be reversed gyro compensation (which is what having the orientation 180 degrees out gives you)

 

[Smoggie]

PS.. You should be able to put the cyclic gain back to the default value for the goblin 380 now. I'm sure most guys with the tri blade use the same gain value as the two blade with no issues, that's what I'd start with.

 

[Heliman450]

Hi Steve, thanks for the follow-up. I already increased the cyclic gain to 40% for yesterday's test hover and it seems OK to increase further for next time from what my limited judgement could tell. I'm getting better at such things with a little help from my RC-Help friends (just you really).

I want to learn as much as I can so your opinion is appreciated on this question....... the Goblin people seemed on the ball by pointing out the need for less cyclic gain, however, the Spirit wizard didn't offer me a 3-bladed option for the 380 from what I saw just quickly looking. Is there another, similar 3-bladed heli option that might give a better starting point for further tuning?

If you can think of one then I'll do some research on what pops up as different settings similar to what I did for my B.D. Axon. I've only used the Spirit Pro wizard once since originally discovering that it ends by saying you're ready to fly when that clearly isn't the case as there's no reference to setting neutral points, servo travel limits etc. throughout the process.

Bye for now.

 

[Smoggie]

The Goblin range (all sizes) are the most obvious helis that come in both two and 3 blade versions. there are others of course but the Goblins are the ones (if any) I'd expect to see in the list of standard setups. I'd be surprised if very different values were needed from the standard 2 blade setup.

 

[holtneil]

Hi you can always ask the spirit guys on there web site
What a gorgeous heli

 

[Heliman450]

Hi Neil, long time no see!

I've visited their Forum on a few occasions when I needed something specific that can be answered simply. I much prefer the more laid back and chatty nature of RC-Help.com

Latest update is that I've fitted the full compliment of upgrades and am ready to go for tomorrow. I was a bit puzzled to see that their list includes a tensioner for the tail belt. It makes a big difference to the belt and the amount of adjustment that is possible using the slots in the tail. Seems like a very odd item to be missed from the kit and listed as an option.

 

[Smoggie]

The tensioner is 'nice' insomuch that the position of the pensioner arm tells you if you have the right tension or not thus taking all the guesswork out of adjustment but to be honest once you get used to Goblins you can easily tell by feel if the tension is right or not. On the big Goblins it's just a case of hauling the boom back with every ounce of strength you can muster! Once settled in and adjusted following the first few flights the tension stays correct pretty much indefinitely anyway. I didn't bother with one on my 420 and it's been fine....and not having it fitted saves a few grams

Good luck with your next outing, hope to see a video soon

 

[Heliman450]

Hi Steve, I'm not a great fan of belts having experienced big problems maintaining the tension. That's one of the main reasons for switching to the T-Rex a while back now. I was very impressed with a friend's Goblin and decided to give it a try. First off the locking screws were completely forward. Now they're a bit forward of centre and the belt feels much better. I got my good lady to put the tension on the belt using a piece of string around the tail rotor shaft and pulling gently on the string while I held the body and tightened up the screws. She did a great job!

 

[Heliman450]

Hi all, at long last, I managed to achieve a maiden flight. Unfortunately, not without a bit more trouble to sort out. The tail rotor adjustment was working fine on the bench and during a pre-flight test also but not when the heli was being tested under power. I discovered that the tail rotor shaft grub screw had come loose and allowed the shaft to slip towards the left of the heli so restricting the amount of travel. After fixing the grub screw and retesting the Spirit Pro settings (again) all seems well.

Just needs a bit more fine tuning, hopefully in the next couple of days before the rain comes back.

 

[holtneil]

Hi I had same problem on the 630 all the grub screws need to be as tight as you can get them with out stripping them

 

[Heliman450]

Thanks for the tip Neil, I'll keep a close eye on it after each flight.

 

[Smoggie]

Phil / Neil

The tail shaft should have a 'dimple' on it that the grub screw locates into, so it really doesn't have to be especially tight. The tip of the screw locks into the dimple so you have mechanical interference rather than purely friction. You do have course have to use thread-locker to avoid it coming loose and you need to take some care on assembly to make sure that the screw hits the dimple.

To make sure that the grub screws are hitting their dimple (works with pinions and motor shaft with flats too) I back off the screw half a turn or so. If the shaft now has a little play but still wont turn then the screw is in the dimple, if the shaft turns freely then the screw must have missed the dimple. Once you are sure the screw has hit the target then tighten it down.

 

[Heliman450]

Hi Steve, I know about the dimple and located the grub screw in it no problem during the original assembly. I also used some thread-lock but I guess not enough as the grub screw still backed off. Having given it a much better coating this time after cleaning the hole and area with a bit of spirit to de-grease it, I'll keep an extra eye on it in future together with all the screws until I'm more confident with the heli's durability.

When I noticed the shaft sticking out (and the screw) I removed the screw completely, pushed the shaft back into position and refitted the screw until I felt the dimple. I then removed the screw, applied the thread-lock and then screwed it fully home. Seems fine now.

I'll see if I can manage a video in the near future. I hope the camera will focus ok.

 

[holtneil]

Me too , well it's nice to know it was not just me ! I had a good 50 flights before it went into a slow piro I was just glad I got it landed with no damage

 

[Smoggie]

My problem is typically the opposite. Thread lock gets in-between the pulley and the shaft and makes it a devil of a job to get them apart even once the grub screw is removed. I'm careful these days not to use too much.

 

[Heliman450]

As my experience of building/rebuilding has increased, I've seen examples (so far from others) of too much thread-lock. That's one of the reasons for me using it very sparingly, this on was just not enough. I normally keep a piece of toilet paper to hand and touch the screw to it before inserting it. That leaves the thread-lock pretty much only inside the threads with no excess to go anywhere else.

Weather's looking good but we're off to a wedding celebration today so no videoing just yet.

 

[Smoggie]

You do need enough thread lock to thoroughly wet the threads. I dont think touching it on a piece of tissue would ever apply enough. I do have some 'inside knowledge' in this respect because at work the Henkel top technical guy for Europe did a workshop with me and a few of the guys from work covering a range of their products. For blind holes the official Henkel advice is to apply the Loctite into the female threads, for the full length of the hole. That's not always easy on very small threads so applying enough to wet out the male threads will also do the trick. Better a be touch generous rather than skimping.

LOCTITE Threadlockers | How to apply LOCTITE Threadlocker - Henkel Adhesives North America Using a Loctite Threadlocker

I hope you enjoy the wedding (I hate weddings!)

 

[Heliman450]

Hi Steve, for the record, I put the thread-lock on the screw and remove the excess from it using the toilet paper. I don't apply the thread-lock from a piece of toilet paper. For small, open-ended parts with no access to the inner end of the hole I normally run the thread-locked grub screw right through before assembly and remove the excess before final assembly. Obviously this time I didn't do it properly but I won't make the same mistake again. Fortunately, no crash occurred.

The only experience I have of stripping someone else's work demonstrated very well that over applying is not the way to go. The bearings were heavily contaminated with it and disassembly was very difficult and resulted in me deciding to junk some parts. The overhauled assembly is working fine since.