DIY collective - need some help

[Raven_Morpheus]

Hello

 

I'm nearly at the stage where I can buy all the parts I think I need for a very basic and compact DIY collective. I've attached a diagram of the size of the collective I'll be building, it's small and compact because I don't have a lot of room...

 

The basic parts I will be using are a Leo Bodnar BU0836A board, a hall sensor + a bic pen with magnets on to go over the hall sensor, the bic pen will then be put through the side of a project box and glued through a 22mm PVC plumbers pipe to provide the pivot point. For the base I'll use some wood, and for friction I'll use a hydraulic suspension damper (possible one each side), attached to the project box at one end and the pipe at the other.

 

At a later date I plan on adding a head with buttons and stuff on it, but that's an easy part, I'm more worried about getting the actual basic stick built first.

 

Problem is I can't get my head around using the hydraulic suspension damper and how to manage the friction.

 

This is the type od damper I'll be using - http://www.ebay.co.uk/itm/RC-Model-Car-Aluminum-98mm-R-C-Hobby-Oil-Shock-Damper-2pcs-OS340-/261465415561?pt=UK_ToysGames_RadioControlled_JN&hash=item3ce08d9f89

 

I'll take the spring off, and fill the damper with some of this for the friction - http://www.ebay.co.uk/itm/CORE-RC-Quality-Silicone-Shock-Oil-100-2000cSt-10-120wt-60ml-Bottle-/230892145987?pt=UK_ToysGames_RadioControlled_JN&var=&hash=item35c23e8d43

 

 

The thing I'm having a problem getting into my head is if the shock damper(s) with spring removed filled with the shock oil (I plan on using 1000cst 80wt) will be A) too stiff for me to move the stick down from an up position or actually be too soft (even though 1000cst 80wt seems to be at the top end of the scale) and thus not hold the weight in place once I put the head on the collective with buttons and stuff on it and B) if I'd need any other source of friction or counter balance and how to achieve it within the size parameters in the pic (due to space limitations where I play the game)?

 

Can anyone give me any tips on this?

 

TIA

Edited January 21, 2015 by Raven_Morpheus

[hannibal]

i dont have any suggestions to your thread..

i have worked with industrial dampeners and it was not a good experience (too much resistance = stress injury)

 

but your RC dampers are giving me motivation to make a long shaft F-15 style joystick!

[hannibal]

btw, i have built my collectives using derlin collar clamps... that worked great for me..

[KomodoSim]

Hi,

 

I use 20000cst oil in my Cyclic and Collective controls. Both still need friction devices to hold the controls in place. It will depend on the length of the arm and the weight at the end of it of course.

 

It will be trial and error until you find the right balance.

 

BR

 

Rich

[Raven_Morpheus]

Hi,

 

I use 20000cst oil in my Cyclic and Collective controls. Both still need friction devices to hold the controls in place. It will depend on the length of the arm and the weight at the end of it of course.

 

It will be trial and error until you find the right balance.

 

BR

 

Rich

 

 

May I ask what you make yours from? I'm thinking that because mine will be made of light PVC pipe and another ABS plastic project box for the head (eventually) that 20k cst oil would be enough (I guess my original plan of 1000 cst was a bit too low?) as there'll be very little weight?

 

 

An idea just occured - how about if I added a bicycle disc brake (would go well with the Ka-50 as that has a collective brake, so presumably I could wire up the brake lever to a button)?

 

I'm thinking that the V type of brake with disc would be the sort to use, but I wouldn't have a clue of how to invert it so that pulling the brake lever opens the brake instead of closing it (if that's even possible)? But that also might become rather annoying in the Huey because that doesn't use a collective brake and I'd always be pulling the brake lever!

 

I'm also wondering if this would work - obviously on the outside of the collective (but not show in my diagram), up against the PVC pipe I would have a piece of wood with a hole for the axis of the pipe to go through, the other side being the side of the project box (which will be housing the Bodnar board). So how about putting skateboard grip tape on the inside of the outer piece of wood (and possibly the side of the project box) so that it rubs up against the PVC pipe, thus causing friction. I could then perhaps add a weight in what will be considered the back end of the handle to act as a counter weight and possibly do away with the dampers then? Although again I have no idea how to really (or what to use as a weight given the limited room I have)?

Edited January 21, 2015 by Raven_Morpheus

[KomodoSim]

Hi,

 

The main control box and tubes are from aluminium and the other main components like the collective heads and throttles are SLS 3D Printed from Nylon12. A very strong and flexible material depending on thickness. If you want the damper to hold the Collective in place then 20000cst might be suitable for your setup if you're using PVC pipe and ABS head box. But you might need something thicker. You will have to experiment with this.

 

The brake system might work, again something that will need trial and error.

 

I would stick with the hydraulic damper as it would give you a hydraulic feel to the movement and it will also be much smoother motion. You will probably get some nose from the grip tape along with jerky movement.

 

BR

 

Rich

[Raven_Morpheus]

Thanks. Guess I'll have to suck it and see.

 

I still can't my head around how the dampers will stop the stick from falling, because to me it seems that if the oil is sufficient to do so it will also require a lot of force for me to move it down.

[KomodoSim]

The dampers work by moving the oil from one chamber to another thru a small orifice. (no sniggers from the back row please!) If the oil is thick enough to not go thru the hole without a small amount of force then the collective will stay in place until a force is put onto it. Does that make sense?

 

With my Multi-Grip system without the collective shaft attached its quite hard to move the pivot arm, but with enough force it moves and is smooth, but stiff ( wow this really is sounding more and more dodgy as I type). So with a longer arm i.e. the collective, its get easier to move, until a point where the weight of the collective is more than the required force to hold the damper oil in place and the collective will move.

 

Its finding the right balance of oil thickness against weight of collective.

 

Think I'll stop before it gets all out of hand, so to speak!

 

BR

 

Rich

[Raven_Morpheus]

Thanks yes that does make sense.

[Chic]

Rich,

Get back to work!!!!!

[KomodoSim]

Am I not even allowed a 5min break?!?!?:(:(

Edited January 23, 2015 by KomodoSim

[Sokol1_br]

Look at this collective, is used some kind of brake disk.

 

http://avia-sim.ru/forum/viewtopic.php?t=630&start=945

 

http://avia-sim.ru/forum/viewtopic.php?t=630&postdays=0&postorder=asc&start=270

 

Other ideas on start of topic. Google translator help.

Edited January 23, 2015 by Sokol1_br

[hansangb]

You can take a break *after* the Huey collective is done :) Can't wait to place the order. Thanks for all your help.

[whatever]

Hi there, I just "finished" (continuous work in progress) building my own collective, and I thought it might be useful to let you know the way I used the hall sensor.

 

I have also used the "bic pen and magnets" method for the throttle (to get 180° travel), but for the collective itself I used a magnet from an old hard drive (one of the long curved ones).

 

I discovered that these are unusual as they have two sets of poles and (more importantly) a N and S pole on each flat side.

 

As a result; if you run a hall sensor held flat along the curve of the magnet it goes from N to S over a space of about 10mm.

 

This means that if you attach the hall sensor to the end of the axle on a piece of plastic card screwed to the end of the axle so that it moves about 2-3mm above the magnet, and choose the distance from the magnet to the axle correctly you can use the full resolution of the hall sensor within about 30 degrees travel (as shown .. red lines are where i calculated the position of the poles using the sensor).

 

 

It works pretty well as the HDD magnet is generally mounted on a piece of metal with holes in to allow easy attachment to your contraption.

 

Heres a picture of the sensor over the magnet (I usually have a peice of 2-3mm plastic card in the gap).

 

And heres a picture of the Axle with small washers to get the spacing right and give the best results. (the axle is an 8mm aluminium tube, and I hammered a rawl plug in the end to get a central screw hole :).

 

The only doubt I have is about the linearity of the change (which is quite sudden when the sensor is touching the magnet but seems much more linear at 2-3mm distance).

 

I hope the pictures a) work and b) are clear enough to show what I'm getting at.

 

As an aside, I used 20mm thick sections of an 8 by 10cm nylon block to make most of the body (chopped with a circular saw).

 

This meant I could make a clamp for the other side of the axle by

a) making an 8mm hole and then

b) drilling a hole for a clamping bolt alongside it

c) using a tap and die set to put threads in the bolt hole, and then

d) sawing through the bolt hole sand into the axle hole to create a space for clamping, and cleaning the threads out of the top section.

 

I highly recommend nylon as a making material.

 

Hope you find this useful.