Author Topic: Turning turrets  (Read 3607 times)

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Offline radio joe

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Turning turrets
« on: 04 July 2013, 15:38:01 »
Hi all
When I built my Solebay I wanted to have the two turrets turning and with two micro servos with levers and push rods it was a limited success achieving about 35 degrees each side, for my next build of Cossack I want to have all four turrets turning in pairs fore and aft and get the full 90 degree each side, so I have been initially experimenting with a very rough mock up to see if this was possible, push rods were out, even with different size arms,
Then I thought pulleys might be the answer, I made a large pulley by cutting out one disc from 1.5mm styrene and two slightly larger discs from 1mm styrene and bonding them together with the smaller one in the middle and fitted the pulley to the servo  and then made a much smaller pulley the same way and fitted that to the mock up turret after fitting the servo to the mock up I used a rubber band between the pulleys and tried it with the RC connected I could see that it certainly worked but not that well, the problem was the rubber band had too much stretch in it so I then used some twine, to stop it slipping I drilled a small hole in both pulleys at the farthest points and tethered the twine to these holes and tried again this time it worked, and achieved about 80 degrees, so I knew it was possible, I made yet another pulley smaller than the last one and set it up again, this time I got the full 90 degree deflection both sides, it needs refining a bit and adapting for the confines of a model but I think I can do it. when looking at the photos remember I did say it was rough.
Joe.
« Last Edit: 04 July 2013, 15:43:13 by radio joe »

roy@origen.co.nz

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Re: Turning turrets
« Reply #1 on: 05 July 2013, 03:04:37 »
Joe, have you tried using one of Action electronics servomorph to alter the rotation speed and distance for turrets?

Offline radio joe

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Re: Turning turrets
« Reply #2 on: 05 July 2013, 08:48:05 »
Hi Roy, the servomorph would indeed be useful for slowing down the turning of the turrets to look more realistic, but it would not help in attaining the 90 degrees using pushrods as the rod on the pushing motion hits the spindle of the turret at about 35 degrees

Offline colin

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Re: Turning turrets
« Reply #3 on: 05 July 2013, 18:41:59 »
its just a thought, but a normal servos travel is about 90?
an undercarriage servo for re-tracks has about 180? travel, but i am not sure sure how big or small these servos are..!!

Offline radio joe

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Re: Turning turrets
« Reply #4 on: 05 July 2013, 19:30:42 »
Hi Colin, I tend to use micro servos because I use one for each turret, as the turrets are usually on different levels and micros are easier to fit into superstructure but I guess you're right they tend to have less travel.
« Last Edit: 07 July 2013, 15:34:41 by radio joe »

Offline kit

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Re: Turning turrets
« Reply #5 on: 31 May 2015, 10:37:46 »
Old thread reopened....

A standard or micro servo can be modified to give a 180 degree throw by putting a couple of resistors in between the potentiometer and the motor.  It won't slow it down but it will increase the throw.  The instructions are here; https://www.youtube.com/watch?v=ymW0Lwmw14Y but there are others as well.

I use Hextronix HXT 900 micros and mount the resistors outside the servo - fitting them inside the servo is fiddly and it usually took two goes to make one usable servo with the second one being junked.  Probably I'm just ham fisted but fitting the resistor outside the servo solved that problem. 

I just cut the wires between the potentiometer and the motor in the middle, drilled a couple of holes in the servo casing, ran the wires through the holes and soldered a resistor in between.  Also eliminates the risk of the iron touching the servo casing as you try to get at the potentiometer.

I used 3300 ohm resistors - you need two per servo.  Theoretically that should give a 270 degree throw but I found it gave a little over 180.  I didn't cut off the lug that restricts the servo throw to 180 degrees as that is sufficient for my purposes but don't forget to chop it off if you want a turn in excess of 180 degrees.

Then put the servo in the hull and stick the turret on top.
« Last Edit: 31 May 2015, 10:44:24 by kit »

Offline radio joe

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Re: Turning turrets
« Reply #6 on: 31 May 2015, 13:50:49 »
These days I use P96 servo morph to extend to 180 degrees and also slow the movement to a more realistic speed of turret movement.

Offline kit

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Re: Turning turrets
« Reply #7 on: 31 May 2015, 16:17:24 »
Hi Joe

I tried the P96 but it only extended the arc on my HXT900 by about 10 degrees - may just be that the P96 is not compatible with the HXT900 and I didn't try on any other servos.  I try and control the speed by hand but agreed it's a bit hit and miss!

The other thing obviously is price - the servomorph is £14 plus P&P whereas I bought 100 resistors for £2 on fleabay inc P&P.

As ever, there is no right or wrong in this game, it's all personal preference, budget etc etc etc

Cheers

Kit

Offline colin

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Re: Turning turrets
« Reply #8 on: 01 June 2015, 05:29:27 »
Quote
As ever, there is no right or wrong in this game, it's all personal preference, budget etc etc etc
if ever there was a truer statement...  ^^^ ^^^

Offline kit

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Re: Turning turrets
« Reply #9 on: 03 March 2017, 20:58:17 »
And more news on turning turrets....

On my latest build I wanted to be control five turrets and after a lot of searching around on the internet I found this http://modelradioworkshop.co.uk/shop/servo-control-devices/5-servo-turret-controller/ ...

I bought one a few months ago and fitted it last week.  It can control up to five turrets independently (but not all at once) using a single channel, extends the servo throw to around 180 degrees and has five speed settings varying between 5 - 25 secs (ish) end to end.  Most importantly, from my perspective at least, it works on positive control so if you take your finger off the stick, it stops where it is as opposed to returning to neutral which is really handy if you have 'wing' turrets - like me!

It takes a bit of getting used to but works well once you have got your head around it.  A couple of pics to show the arcs achieved - no resistors, just a standard servo.

Just in case anyone is building a 'Dreadnought' or similar!

Cheers

Kit

Offline Horatio123

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Re: Turning turrets
« Reply #10 on: 19 March 2017, 16:47:26 »
Forge Electronics who also sell through Scalewarship make a servo morph that will give 180 degree travel and also stop turret turn wherever you want it .  Forge is run by one of My Solent rcmbc members AlanBond .

Offline kit

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Re: Turning turrets
« Reply #11 on: 21 April 2017, 17:19:23 »
I also bought a second one to retrofit my Cossack but unfortunately it was defective.  After a quick exchange of emails I returned it to Mike who sent a replacement by return so after sales service impressive also