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PostPosted: Tue Jun 04, 2013 11:11 am 
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Hi,
I am building my own motorized panorama head. One thing which I think is what gearing ratio should I use. I want to use Nema 17 motor with a torque of 4.4 kg/cm. The shaft has a diameter of 5 mm. First I wanted to use the worm drive, but I can not find it anywhere. If you know where in Europe buy it for a reasonable price and that shop sends to Czech Republic, please tell me. If I used the conventional gear, what ratio would you recommend?
Thank you and please excuse my English.


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PostPosted: Tue Jun 04, 2013 11:59 am 
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I would definitely go for the worm drive on the horizontal axis because friction will usually prevent the motor/ drive train from runnning back.

This means you should be able to switch the motor off between shots to save the batteries.

You might have to use a smaller axle shaft for the worm, or choose a metal one that you can drill out.

Nylon gears should be strong enough but the difficulty might be fixing the worm to the axle so that it does not slip (otherwise the lens might rotate round and hit the tripod - expensive!).

I have used LEGO parts and these have adequate strength.

Perhaps parts for an existing design might be adapted such as food blenders, lawn mowers, oil pumps, speedo drives, etc.

For the vertical axis just about anything will do, gears, chain, toothed belt, etc since the only external forces are friction and wind.

Some friction is good, since it prevents movements due to wind meaning that you do not have to rely on motor power to hold it steady.

Personally, I would use worm drives on both axes because of the friction and it also minimises the parts needed.

To find the gear ratio, you have to decide what camera format, longest lens, camera orientation, and overlap between shots you will be using.

From that, you can calculate how much each axis has to rotate between shots.

Knowing how much the motor on each axis turns for each step you can calculate the minimum gear ration for each axis.

Try searching ebay - even if you do not find exactly what you are looking for it can give you an idea of what to try.

Also google pano head, there are some amazing DIY motorised pano heads out there.

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PostPosted: Tue Jun 04, 2013 12:51 pm 
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Thank you for your response. I would definitely like to use worm drive, but I have a problem to get the necessary part. I'll keep looking. As far as I know, most commercial robotic head have not worm drive and work well, right?


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PostPosted: Tue Jun 04, 2013 1:31 pm 
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tomas.obadal wrote:
Thank you for your response. I would definitely like to use worm drive, but I have a problem to get the necessary part. I'll keep looking. As far as I know, most commercial robotic head have not worm drive and work well, right?

Panoneed has worm-gears for horizontal and vertical movement. Switchable from 1-4Nm vertical and horizontal. http://klausesser.de/Panoneed/ (not finished yet - new Panoneed-domain coming)
Identical gears for hor. and vert. are essential in my eyes for the moves to be precisely reproducable.

best, Klaus

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Last edited by klausesser on Tue Jun 04, 2013 1:32 pm, edited 1 time in total.

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PostPosted: Tue Jun 04, 2013 2:04 pm 
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Really nice robot. A simple but effective design. Moreover, it can be take down to small sizes. Something like that I would like to achieve. I find this worm gear http://www.s-hobby.cz/rctruck/stranky/_38374-snekovy-prevod-1-30.htm, it's czech shop. Metal with gear ratio 1:30, which is I think more than enough. Just worm has a hole for the shaft 4 mm and my motor 5mm, but it should not be a problem.


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PostPosted: Tue Jun 04, 2013 2:12 pm 
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Commercial pano heads tend to have large power packs so can afford to use the motors to hold the unit in position.

I tried using gear trains for both axes but eventually went for worm drive on the horizontal axis because it used fewer parts for the same ratio.

The initial (LEGO) gear train was so stiff that the mechanism did not run back anyway! The friction in the worm system was less, it took fewer parts, less space and I eventually adopted that for both axes.

If you are planning to have a high-capacity battery and control all movement with the motor, a drive using two toothed wheels and a 'timing belt' (or the equivalent using plastic gears and chains) can be very efficient and easy to set up. See http://www.smallparts.com.au/technical/timing/

If you are only intending to use short focal lengths so will be taking few shots, you might well find that the motors you have specified will be accurate enough to work directly without any gear train.

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PostPosted: Tue Jun 04, 2013 3:11 pm 
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I'd like to use it even for gigapixel, so acuracy is important. Thank you for informations, I'm little bit smarter now. I will use worm gear.


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PostPosted: Tue Jun 04, 2013 3:26 pm 
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tomas.obadal wrote:
Really nice robot. A simple but effective design.

That was the intention.

tomas.obadal wrote:
Moreover, it can be take down to small sizes.

I doubt. The motors/gears as well as the batteries/accus have a size.
When you place them outside the rig makes the rig itself look smaller . . but it isn´t :cool:

You also need a certain height for the vertical arm - it provids you a smaller Nadir-hole. Easier to add an extra shot or being retouched.

Josef decided to integrate all parts instead of adding them externally.

best, Klaus

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Last edited by klausesser on Tue Jun 04, 2013 3:26 pm, edited 1 time in total.

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PostPosted: Tue Jun 04, 2013 3:50 pm 
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My english is not so good, so I guess I expressed myself badly. I meant this:
Image


Last edited by tomas.obadal on Tue Jun 04, 2013 4:00 pm, edited 1 time in total.

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PostPosted: Tue Jun 04, 2013 7:09 pm 
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Commercial pano heads tend to have large power packs so can afford to use the motors to hold the unit in position.

I tried using gear trains for both axes but eventually went for worm drive on the horizontal axis because it used fewer parts for the same ratio.

The initial (LEGO) gear train was so stiff that the mechanism did not run back anyway! The friction in the worm system was less, it took fewer parts, less space and I eventually adopted that for both axes.

If you are planning to have a high-capacity battery and control all movement with the motor, a drive using two toothed wheels and a 'timing belt' (or the equivalent using plastic gears and chains) can be very efficient and easy to set up. See http://www.smallparts.com.au/technical/timing/

If you are only intending to use short focal lengths so will be taking few shots, you might well find that the motors you have specified will be accurate enough to work directly without any gear train.

_________________
A sophistical rhetorician, inebriated with the exuberance of his own verbosity, and gifted with an egotistical imagination that can at all times command an interminable and inconsistent series of arguments to malign an opponent and to glorify himself.


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PostPosted: Tue Jun 04, 2013 10:42 pm 
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tomas.obadal wrote:
My english is not so good, so I guess I expressed myself badly. I meant this:
http://s24.postimg.org/6oxjb9kwl/V_st_i_ek.png

Would you prefer to have a head which does it´s work very fine or do you prefer to have it on your chimney for adoring it in the late evening hours sipping on a glass of port . . . :cool:;)

View it in real beneath a Rodeon or a Seitz - and then compare the price-tags :cool:

best Klaus

Ah - ok: now i understand what you meant . . :D

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Last edited by klausesser on Tue Jun 04, 2013 10:44 pm, edited 1 time in total.

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PostPosted: Wed Jun 05, 2013 11:53 am 
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I found that the hardest part was activating the camera shutter.

Here is a link to some of the methods I tried - http://www.flickr.com/photos/73571158@N00/5589231852/in/set-72157623635436569

Hope this helps.

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PostPosted: Wed Jun 05, 2013 6:06 pm 
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Thank you. Camera shutter allready works for me. I used two opto-isolators, one for focus circuit and second for trigger. It works great.


Last edited by tomas.obadal on Wed Jun 05, 2013 6:07 pm, edited 1 time in total.

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PostPosted: Sat Jul 13, 2013 5:40 am 
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http://www.ondrives.com/c/22/pf20nm

These sure look atractive.....now you'll need the more advanced anti backlash version especially for the vertical movement since the whole talk of the camera, rail, lens is pushing down on the axel of the motor. Even for the horizontal movement anti backlash gears can be used but physics dictate that this is not as essential.

Greats, Ed.

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