APM 2.5

[salience]

After much trial and tribulation, I have to report that a direct-drive setup for the main rotor on a TRex500 is not feasible. I had high hopes for the iPower 105Kv, but in the end it just didn't have the true grit necessaary. Sure, it could lift my 3.2kg Trex into hover, with 1600-1900 HS and asymm blades, but was defitiely at it's limit, and would easily start to overheat thus reducing its power even further. Its specs are definitely overstated. Snooping around for other motors similar, it seems there just is not anything available that could work. Also I found that the hoped-for very low vibes didn't work out either, since the coupling of motor to shaft was very difficult to align - some kind of flexible coupling might work however. And possibly you could power a stripped down, lightweight bird this way - the lack of high rpm motor/maingear scream was quite nice!

So it's back to the big gear, and now some retuning, for advice on which I shall soon mosey over to the autotuning thread where the experts hang out. My heavy bird now requires some retuning with the new setup. It's still a bit wobbly from time to time, although it rarely does the hula-hoop gyration in loiter any more. Not really sure how that got cured, or why it occurred in the first place, quite severe at the beginning.

So I have (actually two...) of these iPower 105Kv motors on the excess equipment shelf if anyone is interested - they should be quite good for a multi. Considering you'd have to buy a third or and 4th, I'd be glad to let these go at almost any price offered - I certainly will have no use for them.

[R_Lefebvre]

Oh yeah? Just too much heat? Bummer. I was literally just about to buy one finally. I did just pick up a Goblin 380. Nice little heli. Belt drive to the main. Belt drive tail. And could probably be converted to DDVPT pretty easily. So wouldn't quite be as good as a full DD setup, but close.

[salience]

Howdy Rob,
I was wondering whether you were still sub'd here - heard from joly lately?
Nope, the 105 is definitely over-spec'd - could never draw more than 20A from it and it started to get a bit hot at that - 70-80C, at which point I landed quickly. Several tries. Too bad - it looked elegant.

2 105s for sale!

[R_Lefebvre]

20A! You're kidding, that's really overspecced. Too bad.

Yeah, I heard from Joly maybe a month ago. I think he's around.

[jolyboy]

Hi guys, yeah I'm around. Been away most of the time because of work unfortunately. Too bad the full DD setup wasn't feasible. I had a similar deal with mine and decided to go back to 3D style helix for my FPV. Still haven't flown my chase 360 FPV yet just not enough time.

[salience]

Originally Posted by jolyboy

Hi guys, yeah I'm around. Been away most of the time because of work unfortunately. Too bad the full DD setup wasn't feasible. I had a similar deal with mine and decided to go back to 3D style helix for my FPV. Still haven't flown my chase 360 FPV yet just not enough time.

Yep, disappointing especially having spent a batch of time on it. If the motor had lived up to its specs it would have been just barely feasible but only for non-demanding flight such as photo missions. It might be interesting to try a belt drive conversion for a low-vibe low-noise machine. But enough experiments for now. At least the DD tail conversion is a success. I definitely have something against gears! (Probably it was stripping a box-full of them in early days)

[R_Lefebvre]

Yeah, I have a Goblin 380 right now, and the belt drive is very smooth. It would also be very easy to convert to a DD tail. The only problem is the tail shaft is 5mm, which means you'd need to use a pretty large motor unless you used a stepped shaft or something.

[salience]

• 8 mm Main shaft.
• 5 mm Tail output shaft.

Seems a bit excessive! Maybe they had bought too much 5 & 8 mm stock for the larger birds.


You could use an Align tail unit...>

[R_Lefebvre]

Yes, I guess I could just use a different tail system.

Or just use these parts for a massive stretch.

[salience]

If anyone would care to post a .PARAM file for some monocopter they feel is fairly well tuned, that would be most welcome.

[salience]

Originally Posted by R_Lefebvre

Yeah, I have a Goblin 380 right now, and the belt drive is very smooth. It would also be very easy to convert to a DD tail. The only problem is the tail shaft is 5mm, which means you'd need to use a pretty large motor unless you used a stepped shaft or something.

As much as I dislike multirotors - ugly and ungainly! - I have to admit their popularity has brought us some great products, among which are new types of motors. I found a great T-Motor for my 500, and here's one with 5mm shaft that can take 8S.
http://www.helidirect.com/t-motor-mt3515-15-kv400.html
Might suit your heli if you still do these tail motor mods.

While we're on the subject of monocopters - actually bicopters - I'm just about to tune up a heavy TRex600 modelled on my successful 500 photoship, (see photo: coming in for a landing ultimate selfie ;>) but I'll be using a PixHawk and thus 3.21 firmware, a bit different than the 3.1 for APM. Just for comparison, if you have one, can you PM me a .param file for your (a) 600(s) size bird?

[R_Lefebvre]

It's funny you bring this up as I'm just about to convert over my Protos 500. But isn't that motor a little big for a 500 tail? That one probably has enough power to run the main rotor.

[salience]

Finally decided on how to finish the TRex600, this will be the tail motor for that one, with both main and tail on 8S. About the same weight as the Turnigy Aerodrive 4S I had planned on awhile back, and quite a bit more powerful. I've got a smaller T-Motor in the 500 - MN3110-15 T-Motor - kv780 - 80gr - 481W. But there I need both 3S and 6S. I've another T-Motor for a plane, just bench tested so far, but they are very nice motors indeed, well balanced, power ratings seem honest - better be at the price!

[salience]

Hey Rob,
If you are still here, a question: what output channel is used for controlling the tail motor? And then it will behave like ch8 controlling the main, re: failsafe etc.? Can I use a passthrough to ch9 instead?

There is absolutely nothing in the wikis that has anything to say about the tail motor implementation in trad heli...

On my 500/APM I bypassed the FC for motor control, using chs 9&10 direct from a FrSky X8R but on the 600 with PixHawk I think I'll let the FC do the job.

[R_Lefebvre]

Should be Channel 7 for the tail motor. Yeah, I need to update the Wiki...

[salience]

Perhaps a note to that effect in the "explanatory column" of MP complete parameters page where you set the type of tail.