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old school motor question
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Valen
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its a mode some of the ESC's have designed to vary motor power to keep a constant RPM

like this
http://www.hobbyking.com/hobbyking/store/__8922__turnigy_k_force_40a_brushless_esc.html
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Post Mon Dec 01, 2014 2:58 pm 
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Nick
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ESCs for helicopters usually have a governor mode; perhaps this one will do the job: http://tinyurl.com/oln98yg . You need to use a brushless motor to work with an ESC in governor mode. You also need to work out how fast the current motor is running to pick a replacement brushless and battery voltage so that the new set-up covers the same speed range.

The good news is that there is a large gear reduction with that worm gear drive, which means any speed variation at the motor will mean a much smaller variation after the gearing.

I have 3 or 4 Nikon lenses hidden away; a short zoom, a wide angle, a 500mm mirror tele (probably too wide to fit your turret) and maybe a macro. Yours for the postage Smile.
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Post Mon Dec 01, 2014 4:20 pm 
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miles&Jules
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Omg Nick that is genius... That will be one serious christmas prezzy for us to play with…. thank you thank you. Yep let me know the postage and will put it into your account /paypal. Very Happy Very Happy Very Happy Very Happy

ok so the consensus is brushless is more constant than brushed... ok will check out those escs. So i would need to put the esc into governor mode via a programming card?
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Post Mon Dec 01, 2014 4:33 pm 
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Nick
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Most of those smaller controllers probably just use stick programming - maybe look thru the heli ESC section to fine one that has a programming card, which are so much easier to use.

I should still have the Nikon camera body if that is at all useful. It was nothing special but at least has a mounting ring... Will dig it all out tomorrow for you.
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Post Mon Dec 01, 2014 4:40 pm 
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miles&Jules
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Wow thats epic Nick…your lens donation will pretty much double our nikon lens collection. Can't wait to see em. Very Happy

Yep will have a look on the hk site for em….i have a plush 70 Daniel gave me for the original Judge Mental years back.. i might test that out later to see how smooth it runs. Razz
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Post Mon Dec 01, 2014 5:18 pm 
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Valen
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It's not that brushless is more constant, its just it has a microprocessor in there working to achieve that goal when you are in governed mode, its closed loop control vs open.

Gear reductions won't change the % error, if the motor is out by 10% then after going through the gear it'll still be out by 10%.

I figure the brushless should get you around 5-10% error, still lots of things that can float around in terms of temperature and such like.
You *might* get weird effects or oscillations as the controller hunts to keep the speed constant but that'll depend on the algorithm in the controller.

You could make something up that'd do it with arbitrary precision but it'd cost more than a small brushless and ESC ;->
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Post Mon Dec 01, 2014 5:28 pm 
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miles&Jules
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Thats good to know….i did have a thought though…i wonder how much louder a brushless is than a brushed? Would the botbitz type controllers have the same kind of microprocessor in them or do they not work that way?
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Post Mon Dec 01, 2014 5:41 pm 
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Nick
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quote:
Originally posted by miles&Jules:
Wow thats epic Nick…your lens donation will pretty much double our nikon lens collection. Can't wait to see em. Very Happy


I am sure you will get better use out of them than I will - ever since Kodachrome died, I have gone all digital with a different lens mount.

You probably won't have too much motor noise - the motor housing looks totally enclosed and you will probably need a low RPM motor. The shutter and film feed will be going at 25 fps and that probably means 25 RPM after gearing down. Chances are that the original motor is fairly low RPM to start with and its hard to imagine that a brushless will be noisier than a brushed motor at the same RPM.

Like you mentioned earlier, a quick test with whatever you have is a good idea before dropping any cash.
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Post Mon Dec 01, 2014 5:50 pm 
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Valen
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brushless motors work by using the microprocessor to indirectly sense the rotation of the motor then they switch the outputs (commutating the motor) that replaces the "brushes" in the motor. Sensored controllers and motors use a sensor on the motor to report the position of the motor back to the microcontroller so it can commutate it at low speeds and the like.

The botbitz ones remove that function to get cheap brushed motor controllers with 1/3rd of the brushless controller now sitting idle.

I should say about the reduction, I was talking about systemic errors, things like heat causing the clock in the microcontroller to drift and the like. The big gear reduction would help with mechanical sources of error.

If you can get a brushless with a skewed rotor it'll be less noisy than a standard brushless. A little less powerfull but much lower cogging.
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Post Mon Dec 01, 2014 5:55 pm 
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miles&Jules
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Yep will certainly use those lenses Nick….oh yes loved kodachrome RIP.

Sounds awesome guys will go the brushless then. Very Happy
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Post Mon Dec 01, 2014 5:59 pm 
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Nick
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Your new lens collection:

I found the lenses: they are a 20mm wide, a 35 to 105 zoom and the 500 tele. I also found an extension tube that can donate a mounting ring for your cameflex:



Now the hard part: finding a sturdy shipping box. Smile
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Post Wed Dec 03, 2014 9:05 am 
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miles&Jules
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Omg it really is christmas….always wanted a real 20mm nikon!….and those others will get some seriously epic shots of the moon and other long distance shots. Cant thank you enough…I will buy you some serious beers next Nats he he Very Happy
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Post Wed Dec 03, 2014 9:16 am 
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miles&Jules
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[URL=http://s1091.photobucket.com/user/milesandjules/media/moon30-12-14.jpg.html] [/URL]


i put that 500mm to use last night Nick Shocked

loving them lenses Very Happy Very Happy Very Happy
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Post Wed Dec 31, 2014 10:29 am 
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Nick
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Wow, not bad for a lens I bought 25 years ago in Hong Kong! What camera did you have the lens on for the moon shot?
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Post Wed Dec 31, 2014 11:03 am 
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miles&Jules
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Hi Nick its on a lumix gh4 its micro 4/3 camera so its already double the zoom length ..so that makes it 1000mm and then i think i used 2x in camera digital zoom aswell…so does that make it a 2000mm pic? Anyway its a cool lens…going to be even better on film. Very Happy
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Post Wed Dec 31, 2014 1:42 pm 
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