View Full Version : Cheapo Leadscrew with minimum accuracy requirement!
02-10-2010, 03:30 PM
I'm looking to make a motorized linear system to move a video camera (< 5kg), about 1m long. I'm a total newbie with this kind of thing but I thought a leadscrew and nut would be a good way of doing it.
For the intended use, I guess the accuracy/backlash etc is not really a problem so I'm just looking for something cheap but fairly reliable.
I was thinking of using SS leadscrew as it will be used in a domestic situations including outdoors. Is this 10mm leadscrew: http://www.worldofcnc.com/products.asp?recnumber=231 and this brass nut: http://www.worldofcnc.com/products.asp?recnumber=49 the right sort of thing to use?
Any ideas, cheaper suppliers or help would be appreciated.
02-10-2010, 04:17 PM
For a moving camera(If just surveilance?)Iwouldn't go for a lot of expense ie my choice would be stainless steel M12 threaded rod and associated SSnuts.
02-10-2010, 04:26 PM
Well Vikash that will work, depends on the speed you require and what levels of vibration you can withstand. What is your actual requirement?
02-10-2010, 05:49 PM
hi viklash.... heres my ten bobs worth.... i built somthing similar to carry an SLR but it was for a stop motion animation i was doing so it was hand cranked.... i used a builders level for the rail, cut a toothed printer belt and pinned it to one of the sufaces of the level, used one of the printer pullies as a drive and four small bearings ran on the inside of the builders level... super light weight
if you want it driven.... id use an RC servo with a servo tester with battery pack... dial in the speed and a away you go... your audio will be goosed by the servo but im guessing you allredy knew this
it shouldnt cost you much more than £50 in parts excluding the printer belt and pully.... if your interested in this low tec version let me know and ill try to get some pictures to show you what i mean (its stripped now but i still have most of the parts)
02-10-2010, 05:59 PM
It's for Videography, so smooth motion is imperative. I'll be mounting HD video camera with a pan/tilt fluid head which means there will potentially be some other forces at play during movement. No need for a stepper motor with precise control, just something that allows variable speed of movement ranging from very slow to perhaps ~5cm per second at the top end.
At the moment I'm using a manual push system using a ball bushing carriage on an extruded aluminium extrusion - this doesn't lend itself to consistent, repeatable results.
Perhaps I should try some SS rod from B&Q as a sort of proof of concept, but I assume 10 or 12mm trapezoidal leadscrew and nut would give far superior motion in terms of smoothness. Even a ballscrew is not out of discussion, although I'd prefer spending as little as possible for the results I'm after.
02-10-2010, 07:35 PM
Got a feeling that gear&rack will be the smoothest for this along with speed and slow tracking into the bargain.
The rackis the dearest component but willbe a lot better choice for me over leadscrew.
03-10-2010, 09:04 AM
If moving the camera in an arc is ok the old servo satellite gear could be the answer. There are two methods diseq and jack method. Look up superjack on ebay, the jack method is usually stronger and should be available second hand because most sat people have gone over to diseq.
03-10-2010, 07:41 PM
What about some chromed rail (25 - 30mm from wicks and acetal rod bearings pulled back and forth with wire would be a much cheaper option and an easy build? like in a printer the wire can be wound a few times at one end and a tensioner at the other. The bearings can be whipped up on a lathe.
04-10-2010, 10:28 AM
Thanks for the replies.
It does need to be motorized, so I'm not looking for anything to push/pull (only). I already use a push system (commercial design that cost £200 for 50cm) and I'm certain something better can be built for less.
I briefly looked at the superjack thing, but I don't think it satisfies the variable speed requirement and couldn't see it extending from 0 to ~1m either.
I thought the gear and track method wouldn't offer the finesse as slower speeds as a leadscrew/nut?
Mark, not sure where your posts have gone, but the head I use is the 701HDV.
These aren't strictly neccessary, but it would be nice if the system could be used manually as well as motorised (can a nut be pushed to turn a leadscrew easily?), and also it would be useful to be light enough to transport around!
04-10-2010, 11:02 AM
And would you believe it, someone's already done what I was thinking: http://vimeo.com/12876400
04-10-2010, 12:28 PM
Vikash the idea was not meant to be manual bu utilise a stepper at one end, the wire would be your leadscrew in effect
04-10-2010, 12:32 PM
Just looked at hat link and the track they are using is 'IGUS' linear rail. You can use that and still use the wire method which would do away with the need to mount extra gearing and would run smooth.
04-10-2010, 10:06 PM
hi vikash, not sure what happend to my post... 701HDV ill assume your using a pretty tubby camera on that, a builders level would be all over the place with that much weight on it, if you tend to film indoors then building a heavy rig isnt to much of a problem... if you go on solo missions out and about though i wouldnt right off the toothed belt or wire option, maybe even 2mm dyneema, it will help you keep the weight way down,, i was also thinking of rebuilding mine using two carbon tubes for rails (most of my stuff is in the mountains) maybe 15 or 20mm OD
ps: if you do give the rc servos a try you need to remove the feedback pot gear to get the servo to run endlessly in what ever direction or speed you dail in
have you got any of your work on vimeo?
06-10-2010, 05:46 AM
A modification of the zazaslider (http://www.zazaslider.com/) shouldn't be too difficult or expensive. The major expense is the Igus guides
There's a vimeo group (http://vimeo.com/groups/zazaslider) and youtube footage on this.
06-10-2010, 10:15 AM
I have a Glidetrack which is based on the Igus slider. In short I'm here because of that - and the need of something sturdier with finer and repeatable control. I don't think it's worth hacking it to motorize it somehow, mostly because of its cost. And it does have a place where portability is a concern (and cost in the commercial world).
However I find it lacking for product shots where smoothness and consistent speed is more of a priority. It's not nearly sturdy/controllable enough for vertical sliding shots (when mounted as intended on a tripod).
I have since purchased a 16mm ballscrew/nut (5mm pitch), a (geared) 300rpm 12v DC motor, and a PWM control board to control it's speed and direction. I plan to make a MDF carriage (simple U shape) sitting on a narrower U shape guide for initial tests. I'm just trying to figure out how best to support the ballscrew. BK12 / BF12 supports are overkill.
Thanks for the feedback so far.
Nothing on vimeo yet. I may upload some shots later on... I did toy with using RC servos as I have a few laying around. I didn't quite get my head around the controller required though and what it would allow exactly, although I might have another look into it.
06-10-2010, 10:55 AM
What sort of weight constraint do you have?
(I'm assuming this is the major consideration for a portable device)
06-10-2010, 11:17 AM
Well, we're not talking about time critical capture here, so the ease of moving it around is low in priority. As long as one person could move/set-up, I would guess up to 20kg wouldn't be unreasonable.
For any non-product or real-time videography where actual portability is required, like any social event or a wedding for example, it would be glidetrack all the way.
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