motor to pull camera dolly

[apostolakisl]

If you look at a manual winch, they have a ratcheting action with a little pin of sorts that can be pulled away from the geers to allow free movement. If you pull the pin back for a split second, it will let the winch unwind one tooth.

A solonoid could be used to do that, or any electromagnet that pushes the pin out of the way for a split second letting it unwind one "click". Also, grandfather clocks work that way, letting the weights slowly descend as they power the pendulum (mechanical of course, not electric).

And your diagram is very cute, but pretty much accurate. You didn't show the spring or whatever tensioning device you would use to keep it sliding to the right, but I think you get what I was saying.

 

[v1rtu0s1ty]

it's the spring where I am confused. I don't know where to put it.

Also, I haven't examined a winch in real life so I am not sure how it really works. What I am thinking is that it's similar to a fishing rod that holds the nylon string?

Is there a small winch that can be bought? I searched google and found some but looks like they're way too much for my requirements. I've seen like support for 2500 lbs. hehehe.

 

[v1rtu0s1ty]

check this out, will this work?

http://cgi.ebay.com/Harbor-Freight-Tools-Coupon-12-Volt-2000-lb-ATV-Winch-/230641635255?pt=US_Coupons&hash=item35b3500fb7

 

[apostolakisl]

No, those are powered winches. We are looking at releasing line slowly, not pulling it in.

The spring or other tensioning device is attached to the right side of your sled (as it would be oriented in your picture) and pulls it to the right. The winch holds it back, releasing a little bit at a time.

You don't even need a winch, just a wheel with teeth that you can periodically release one tooth at a time allowing your string to unroll and the sled to move toward the right as it unrolls.

 

[JimS]

Check google for camera trolleys - there are tons of sites with info. I had looked into this a while back but can't find my links... Most use skate wheels on round tracks as was pictured. For movement most use a small wheel with friction to the rail. They use various gear motors such as battery screwdrivers and others. Because of the slow speed you just need to get a high gear ratio. If the gear ratio is not quite enough then pulse the motor on an off. Because of the relatively short length you could use a length of threaded rod to get a higher effective gear ratio. Surplus places have windshield wiper motors very similar to the window lift motor mentioned for around $20 but the speed is a bit too high.

Tamiya makes a planetary gearmotor kit with two 4:1 and two 5:1 stages that can be combined in any combination for up to 400:1. I have read that it is possible to use multiple kits for even higher ratios - 2 kits could give 160000:1! And the kit is less than $20. Not sure how noisy this is if that is an issue.

http://letsmakerobots.com/node/3106?s=l

If you are planning to use this a lot and/or have a heavy trolley you might want to go with higher quality stronger parts but for light use this looks just about ideal. Couple it to a friction wheel with spring tension. You may even be able to get a wheel that fits right on the Tamiya gearbox.

Here is another site that may be helpful:
http://www.diyphotography.net/build-an-amazing-super-versatile-diy-time-lapse-dolly

 

[v1rtu0s1ty]

Just got back from Naperville Ribfest. Went there to just watch STYX!

I'll read up on your posts in a few. I've got a headache probably due to the loud sound.

 

[v1rtu0s1ty]

That video is wicked! That's how I am going to do it!

Thanks for sharing!!!

 

[tmbrown97]

With a high end DSLR, you need an external intervalometer. If you have a cheaper consumer grade Canon camera, you can use the awesome CHDK firmware (I use this with cheap Canon PowerShots to create portable 'sentinels') to do all of this.

You must mean with a high end Canon DSLR...

my Nikon D200 has this built in. I didn't realize that was unusual but it was one of the bigger reasons I went with the D200 over a lower model but just assumed Canon had it too since I knew those videos were taken with a Canon.

That said I don't necessarily think better of one brand over the other - they're both awesome camera makers!

 

[tmbrown97]

One other thought - power antenna motors. I can't find a good video link in the 20 seconds I searched - but the ones I've seen seem to work off a geared strip (like a belt) - that could theoretically be lengthened to any length... they're linear in nature and move both directions - you'd just need to slow the speed down. Just another potential option.

 

[apostolakisl]

Check google for camera trolleys - there are tons of sites with info. I had looked into this a while back but can't find my links... Most use skate wheels on round tracks as was pictured. For movement most use a small wheel with friction to the rail. They use various gear motors such as battery screwdrivers and others. Because of the slow speed you just need to get a high gear ratio. If the gear ratio is not quite enough then pulse the motor on an off. Because of the relatively short length you could use a length of threaded rod to get a higher effective gear ratio. Surplus places have windshield wiper motors very similar to the window lift motor mentioned for around $20 but the speed is a bit too high.

Tamiya makes a planetary gearmotor kit with two 4:1 and two 5:1 stages that can be combined in any combination for up to 400:1. I have read that it is possible to use multiple kits for even higher ratios - 2 kits could give 160000:1! And the kit is less than $20. Not sure how noisy this is if that is an issue.

http://letsmakerobots.com/node/3106?s=l

If you are planning to use this a lot and/or have a heavy trolley you might want to go with higher quality stronger parts but for light use this looks just about ideal. Couple it to a friction wheel with spring tension. You may even be able to get a wheel that fits right on the Tamiya gearbox.

Here is another site that may be helpful:
http://www.diyphotography.net/build-an-amazing-super-versatile-diy-time-lapse-dolly

That is so perfect. I had no idea prefab gears like that existed. So, no more worries about using bike gears! Using a threaded rod to push the sled is a thought I had as well, but I have never seen a threaded rod longer than 3 ft (at least not at HD/Lowe's). I used to have a genie screwdrive garage door opener which came with a roughly 10ft threaded rod which probably is as long and longer than you would need. I am sure there are dozens (or more) of those getting thrown out every day, if only you knew which trash can to visit! You might give Craig's list a try. My local one had someone selling a used one for $100. Changing out the motor with one of those other models and you have a nice 8ft or so smooth driving puller/pusher with all of the bearings and everything in place as well as a nice carriage to attach to your sled. You could even use the Genie track as one of your two rails.

 

[v1rtu0s1ty]

That is so perfect. I had no idea prefab gears like that existed. So, no more worries about using bike gears! Using a threaded rod to push the sled is a thought I had as well, but I have never seen a threaded rod longer than 3 ft (at least not at HD/Lowe's). I used to have a genie screwdrive garage door opener which came with a roughly 10ft threaded rod which probably is as long and longer than you would need. I am sure there are dozens (or more) of those getting thrown out every day, if only you knew which trash can to visit! You might give Craig's list a try. My local one had someone selling a used one for $100. Changing out the motor with one of those other models and you have a nice 8ft or so smooth driving puller/pusher with all of the bearings and everything in place as well as a nice carriage to attach to your sled. You could even use the Genie track as one of your two rails.

I bought threaded rod which I think is about 8 ft long at HD. I used it to lift my crt projector. Took me 12-14 hours just to get the crt proj up on the ceiling. LOL. I wasn't aware I can use a ratchet which is easier.

Found this pic from my archives.

 

[JimS]

That is so perfect. I had no idea prefab gears like that existed. So, no more worries about using bike gears! Using a threaded rod to push the sled is a thought I had as well, but I have never seen a threaded rod longer than 3 ft (at least not at HD/Lowe's).

It would seem like bike gears have their place - for low ratios and higher torque I am guessing. I haven't used them on anything but bikes. Might be good as a final reduction and use a gearbox for the higher speed/lower torque stages. What do you use for hubs? Seems like this would be hard for the rear free wheel sprockets.

On the threaded rod - You gotta expand your suppliers. Grainger has threaded rod in up to 12 ft lengths, MSC has up to 6 ft. And the prices are very reasonable. Support for long rods can be a issue though - especially if you run them fast.

 

[apostolakisl]

It would seem like bike gears have their place - for low ratios and higher torque I am guessing. I haven't used them on anything but bikes. Might be good as a final reduction and use a gearbox for the higher speed/lower torque stages. What do you use for hubs? Seems like this would be hard for the rear free wheel sprockets.

On the threaded rod - You gotta expand your suppliers. Grainger has threaded rod in up to 12 ft lengths, MSC has up to 6 ft. And the prices are very reasonable. Support for long rods can be a issue though - especially if you run them fast.

Well, never really needed a threaded rod longer than 3 ft so I never looked.

The nice thing about the threaded rod on a screw drive garage door opener is that the support, lubrication, carriage, and bearings are all built in.

I considered using threaded rod for my chicken coop door, but that would meant putting the motor on the door or using a sizable lever arm since I didn't want rod sticking out of the coop when the door was closed. The pinch rollers I used can be manually forced so there is a chance that a racoon might be able to pry it open. But I doubt it, you have to pull pretty hard and when it is shut there isn't really anywhere to grab.

 

[v1rtu0s1ty]

JimS,

For now, I'll use whatever I'll find in my garage or basement. You mentioned this previously:

They use various gear motors such as battery screwdrivers and others.

Am I right that I can use the gear motor from this rechargeable battery powered screwdriver? It says Type 1 2.4V and 150/min RPM. On the other side, it says NOM 2,4v.

 

[JimS]

JimS,

For now, I'll use whatever I'll find in my garage or basement. You mentioned this previously:


Am I right that I can use the gear motor from this rechargeable battery powered screwdriver? It says Type 1 2.4V and 150/min RPM. On the other side, it says NOM 2,4v.

I think that should work pretty well. You will need a low voltage power supply of course and some way to attach the load to the output. Hose clamps work good for holding the housing.