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Old 06-11-2018, 09:47 PM   #1
james111333
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Default Real RAF Merlin collective project

So it's official, after many months of silently stalking this awesome forum, I've finally signed up to post so hello everyone!


I figured I'd start out with a build thread to cover the design and construction of my helicopter collective.



As of today I am the proud owner of a genuine RAF Merlin collective, I must say, the build quality is incredible, it makes my TM Warthog feel like a toy, especially the switches, it may even be more of a step up in feel and build quality than going from my x-52 Pro to the Warthog. The buttons and toggle's clunk is supremely satisfying.


Here it is, I'm hoping it's the only one of it's kind at the moment (when I turn it into a USB device I mean)






My plan is to connect it to a Lebodnar board and construct an axle base then using either a pot of hall sensor for the rotational position sensing but all this will be covered shortly, I think one of my main reasons for creating the thread was not to show everyone as much as to hopefully discuss various design options and throw ideas about as although I'm happy to execute the project, I still have a lot to learn so hopefully you guys will be kind enough to get on board share your experiences with achieving what we all set out to do.


Here is a very quick and dirty initial plan for the mechanism.

https://youtu.be/SqSDFWoDTuk

Essentially it will consist of a bearing mounted axle with a nylon disc fused to it, using finely threaded machine screws, I'd then be able to infinately adjust the clamping force to enable just enough slip to be moveable but still avoid drooping of the collective.
I'd like to implement an adjustable counter weight to balance it but due to space limitations, I may not be able to do so. Or at least I may be able to have a short counter balance arm with a cutom moulded lead weight to take some of the required force away from the crude friction system. I have looked at adjustable slip clutches but these are quite expensive.


I'll add to the thread very soon with much more info and to open up some discussions, I'm really keen in the meantime to read people's views on pots VS hall sensors for this aplication. mounting a pot will be easy but I will probably only use about 20% of it's 360 degree travel and I would like to think that the higher the resolution, the better. I love how insanely accurate my MFG crosswinds are and maybe a collective doesn't need that much accuracy but I still want to get it as high as possible. Any input would be awesome, including exactly what resolution DCS will recognise from a throttle or collective.


Many thanks, great to meet you all, James



Last edited by james111333; 06-11-2018 at 10:25 PM.
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Old 06-11-2018, 09:58 PM   #2
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It has 16 buttons and 2 x 4-way HAT switches as well as 2 x self returning rockers (like the red thumb switch on the TM warthog throttle). There are about 40 wires coming from the buttons but I think that a lot of them are from discrete circuits on the helicopter whereas I will be using a common 5v across all of them and then simply toggling them to on or off with the buttons. Would the BU0836A 12bit Joystick controller will be the right choice to go for? The HATs seem to be more like 4 way up, down, left, right buttons so no way to engage two at a time like down/left or down/right etc so I assume these will be seen as buttons too.


I am thinking the buttons and switches should be pretty easy once I have identified all of the cables but my next question would be; what would you all recommend for the highest accuracy to sense the angle of the collective? I guess my options are either a pot or a Hall sensor but I have only used hall sensors in the past for on off switching rather than a positional sensor. If the range on the collective is only say 60 degrees from fully open to fully closed, will I get enough resolution from turning a Pot through only about 1/5 of it's range?


The other option of the Hall sensor is a little more unclear, as I'm not aware of how accurately it could sense the arc of the collective axle which will probably have about a 10mm radius so if the arc was say 20mm, would the hall sensor be in range of the magnet at all times?



I haven't found out the required resolution in DCS yet but I'd like to get as accurate as I can. Will a pot be suitable given the limited amount of angle used? I know it is better to use as much of the pot's range as possible so I could consider gearing it down from the main axis so I get more like 270 degrees travel on the pot, the issue there though would be the additional engineering involved which I'd like to avoid.
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Old 06-11-2018, 10:02 PM   #3
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Looking great, Good luck with it.
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Old 06-11-2018, 10:18 PM   #4
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Thanks, I can't wait to get stuck in, I think the first job will be an hour with the multimeter and some masking tape to label all those wires!!


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Old 06-11-2018, 10:19 PM   #5
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I did the same with my Lynx collective. Hundreds of wires, most are redundant for what you’ll need and most you may well cut out cos they get in the way.

I tried both pots and hall sensors, but could never get the halls to work reliably so settled on pots (it was never intended on being a pro job mind you). It was more a rack and pinion type drive I used with the pots which actually works really well. I also have a motorbike steering arm damper get give it a better feel to which is also attached to a steel plate and some magnets to prevent it slipping down. I’m sure you find a better solution. Molevitch on here made some excellent posts about his own project with a Mil-8 collective.
It makes such a difference using it in the DCS though.
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Old 06-11-2018, 10:21 PM   #6
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For the wires, I took the back of the head off, exposing the switches etc, then pulled them all through. Much easier to work with I thought.
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Old 06-11-2018, 10:58 PM   #7
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Quote:
Originally Posted by mr_mojo97 View Post
I did the same with my Lynx collective.

Awesome, thanks, I'm just reading your thread now, seems like we have very similar ideas and hardware tastes
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Old 06-11-2018, 11:04 PM   #8
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Quote:
Originally Posted by mr_mojo97 View Post
For the wires, I took the back of the head off, exposing the switches etc, then pulled them all through. Much easier to work with I thought.

On the Merlin there is a screwed on faceplate which looks easy to remove to access wires and test continuity, each switch is also screwed in with Torx bolts so can individually be removed / accessed so I'm hoping it won't take too long to identify the redundant wires. Although I couldn't bare to cut them haha, it's still a serviceable unit!! I know it won't ever fly again but I want to keep it in it's original state. I'm not sure what the Lynx wires were like but these are all braided and manageable, nothing like the wires I use for my Raspberry Pi, they're just a tangled mess.
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Old 06-11-2018, 11:26 PM   #9
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Take a look in Bit-Tech 6127 HALL sensor, assembled like a pot.

https://www.youtube.com/watch?v=AE3l40g4YqY

Pay attention in "electric working angle" - you need get the model 30-45 or 60 degrees maximum.

For collective mechanism take a look in UO53 "multi-disk brake system":

https://forums.eagle.ru/showpost.php...&postcount=285

Last edited by Sokol1_br; 06-11-2018 at 11:31 PM.
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Old 06-11-2018, 11:40 PM   #10
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Sokol your wealth of knowledge on controls is just insane
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Last edited by Deadman; 06-11-2018 at 11:59 PM.
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