Knex Time-lapse Intervalometer




Introduction: Knex Time-lapse Intervalometer

About: Yes, I know that its spelled "projectile"

Updated, 21 July

Ive uploaded a much better video of a finished timelapse. It shows the full moon rising through clouds. Captured using the 10 second interval. Ive had to resize the video to make the filesize manageable.

Have you ever seen those time lapse panoramas on TV/Film and wished you could make your own?

Do you have a cheap digital camera, and some motorised Knex lying around?

Do you want to see a Knex instructable which isnt for a gun?

If youre answering "yes" to the above questions, then read on. This will show you how to build a structure from knex which will hold your camera, and press the shutter button every 2, 5 or 10 seconds. Then I will show you how to take all the individual frames and merge them into a smooth timelapse, which you can then convert into video to share.

Im going to post the instructions for my camera (Samsung S860) and the knex rig (using a Cyber Knex motor). You will probably have to make a few small modifications to fit your camera and motors into the frame.

Step 1: Camera Holder and Rocker Arm

This part holds the camera and also has the rocker arm which presses the shutter button to take a shot. The success of the entire rig depends on what you do here, so dont try and cut corners.

Your camera is probably going to be different from mine so you might need to modifiy this piece so that your camera fits in. It should be a tight, rather than just snug fit, so the camera doesnt wobble. But it shoudnt be so tight that it damages the camera.

1: The base plate. This is where the camera goes.

2,3,4: The rocker arm

5: Rocker arm and baseplate attached together.

6: Camera fitted in and ready for testing

Assuming you have the camera fitted in, adjust the rocker plate/camera position so the purple connector is just hovering over the shutter button. Now, turn on the camera, and lift the rocker plate gently with your finger. Hopefully, without too much effort the camera will auto focus and then take a shot. If it does, move onto the next step.

If it doesnt take the shot, all Im going to say is keep adjusting it until it does. Change the spacers around of the rocker axle, shift the camera, redesign the rocker arm. Anything which makes it work.

Step 2: Frame

This is just the frame which holds everything together.

1: Build this

2: Attach the part you built in step 1 to the frame

3: Keep building

4,5: Build these

6: Attach them together as shown

7: Add these spacers and connectors onto the grey rods. (same length as the yellow ones from the classic sets).

Step 3: Gear System and Cam

This part is what pushes the rocker up. Its very important that you put the right number of spacers in.

1: Build this, but be prepared to change where the white rod is if you find the cam doesnt work properly.

2: Clip it onto a red rod in the frame

3: Add the red gear

4: The cam

5: Where it goes

6: This is how the end of the rocker arm should fit onto the cam.

At this stage, you want to test that the cam works. Put the camera in and turn it on. Now, turn the red gear anticlockwise slowly. The cam should lift up, pushing the rocker up and hopefully taking a shot. If you continue to turn the cam, the rocker should snap back down. Keep turning it a few times to make sure it works.

If it doesnt work, then again its up to you to adjust it until it does. The main thing is where the white rod is connected to the grey connectors in photo 1. Try moving it to the next connector point, so its effectively one of the 90 degree red connectors.

7,8,9,10: Keep building the frame as shown.

Step 4: Motor and Gear System

Im using the Cyber Knex motor. All the other knex motors Ive seen should be able to fit in here with a little modification.

1,2: The motor and mount

3: Build this

4: Attach it.

5,6,7: Fix the motor into the frame

8: Build this onto the rod.

9: Put a small tire hub onto the motor rod.

Now you have to test the gear system. Put the camera in, turn it on, and then turn on the motor. You should see all the gears start to turn. The cam which pushes up the rocker should rotate slowly clockwise, and then push the rocker up, taking a shot. If you leave it running, then the camera should take one shot every 10 seconds or so.

Step 5: Gear Ratios

The default shot interval is 10 seconds. The rig can be very easily changed to give a 5 or 2 second interval. Before I show how to do this, Im going to explain which one you should use to begin with.

The timelapse is played back at 30 frames per second. In other words, if you take 30 shots with this rig it will give you one second of smooth video.

  • Using the 10 second interval, that will take 10x30=300 seconds, or 5 minutes. So, for every 5 minutes that you leave the rig running, you get 1 second of video.
  • Using the 5 second interval, you get 5x30=150 seconds, or 2 and a half minutes needed to get 1 second of video.
  • Using the 2 second interval, you get 2x30=60 seconds, or 1 minute needed to get 1 second of video.

What does this all mean? Well, basically the shorter the interval you use, the slower the timelapse appears to progress. For example, if you filmed a sunset using the 2 second interval, and then the 10 second interval, in the 2 second one the sun would move much slower. You would also capture more detail, like people moving by and birds flying etc.

It ultimately comes down to how much space you have in your camera memory, and how long the batteries in the camera will last.

For your first timelapse, I advise you use the 10 second setting, just because its simplest. This is the default ratio which you should have if you built it properly in the previous step.

To change ratios:

To change to either the 2 or 5 second interval:

Photo 1: Change the rod to look like this. If you turn on the motor now, the yellow gear should move but not the rocker arm.

Photo 2: This is for the five second interval. Loop an elastic band around the pulleys as shown. Now, if you turn on the motor, the rocker should move about every 5 seconds.

Photo 3: For the 2 second ratio, put the band between these two pullets but loop it round 180 degrees so it turns the cam in the right direction.

Step 6: Camera Settings

Im assuming that you have the rig set up and ready to go. However there are a few VERY important things you need to prepare before you do. Im also going to assume you know how to change most of the settings on your camera.


-The rig works properly and is taking photos every 10,5 or 2 seconds.

-You have the rig on a solid base to stop it from shaking.

-It helps to totally clear the memory card before you start.

-Set the photo size to the lowest it will go. On my camera, this is 1 megapixel, or 1024x768 pixels. This gives you the most frames for your memory, and makes it much easier to make a video from the frames later on.

-Have good batteries in the camera. Any old alkalines are fine for the motor, but if you can, put Ni-mh rechargeables in the camera. These last for at least 5 hours of continual use in my camera.

-Disable flash on the camera. Especially if you are filming a sunset or dull place.

Well, thats it. Put the camera in, turn on the motor and tape down the button. Watch the rig for a while and check its taking each frame properly - you might have to adjust the focus settings if its not. Then you can just go away and leave the rig until the batteries run out, or the camera memory becomes full.

Step 7: Viewing the Timelapse

Once the timelapse is complete, you are ready to import the frames. Create a new folder on your computer and copy all the time lapse photos from the camera into it.

Next, you need to download a program called "VirtualDub". Its a simple, free and open source video editor. You can get it here:

1: Open virtualdub and the folder with your photos in it

2: Select the very first frame, and drag it ontop of the virtualdub window. You should get a "scanning frame XXX.." message. Wait for it to import all the frames.

3: Virtualdub should look like this when the timelapse is ready. Simply press either of the little play buttons down in the left corner. You can use the mousewheel or the slider along the bottom to manually move through all the frames.

With any luck, you should see your timelapse play smoothly in the window. If you want to convert it into a video file, do the following:

  • If you want to resize the video, go to the "video" tab along the toolbar, select "filters" and then hit the add button. Select "resize" from the list. Change the %value which should already be highlighted. 50% halfs the size, 25% quarters it etc.
  • You can also set compression. This is a good way to decrease file size, but it can also lead to a loss in quality. Again, go to the "video" tab and select compression. Choose microsoft video 1. You can then enter a % compression value. 80% is a good tradeoff between size and quality. Higher compression means higher quality but a bigger filesize.
  • Now, go to File>Save as AVI. Simple.


Ive encountered many problems with both the camera rig and with converting the timelapse into video. Here are the most common:

The rig works, but its really loud

Most of the noise comes from the rocker arm snapping back down after its pressed the shutter. Try removing the white rod from the purple connector at the end of the arm, so just the blue rod holds it on. This should make the arm more flexible and quieter. (EDIT: Im going to upload a picture to show what I mean, watch this space)

I cant get fit very many frames into my cameras memory

Check that you have the photo size to the lowest it will go. This gives me about 2100 frames on a 1GB SD card. Next, try using a longer interval. The last thing is simply to buy a bigger memory card for the camera.

The timelapse comes out as very jerky

There are a few things that cause this. The main cause is that you have the rig on something unstable, like a tall wooden table. Small vibrations and wobbles become very apparant when you view the timelapse.

Sometimes this can be down to your computer. If you didnt put your photo size down to something like 1 megapixel, then virtualdub will struggle to render all those big photos quickly. Also, if youre on a laptop like me, make sure its plugged in and on high performance mode. For the record, my system is: 2GHZ core 2 duo processor, 2GB RAM and a 7900GS graphics card.

The video I made is a huge file.

Set compression (you did pay attention to this part, yes?) to something less than 100. 80 is good.

The video I made is small, but its really grainy/looks bad

Raise the amount of compression you are using. Anything below 70 for me gives really poor quality.


The rig is too big/ too ugly etc

Let me know when you have redesigned it ;)

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    Lance Mt.
    Lance Mt.

    13 years ago on Introduction

    Total annihilation? You sir, are Awesome. I'm 14, when i was 4 i was playing this hours at a time before preschool... PEE WEE RUSH!

    Lance Mt.
    Lance Mt.

    Reply 13 years ago on Introduction

    lol sorry i forgot, i also use to dream about it.. AS sad as that is, it suuuuch a good game

    That's cool! But I think my camera is a little too fat to fit in there... Anyways great! 5 stars.


    13 years ago on Introduction

    Hehe, this could be quite useful! If I only had a camera... 5 stars anyway!


    14 years ago on Introduction

    something of knex that actually serves a practical purpose... IT'S THE END OF THE WORLD!!! Interesting and cool idea though, bravo


    14 years ago on Introduction

    Awesome, although good k'nex guns are great, it's good to see something new!


    Reply 14 years ago on Introduction

    This is an awesome idea as I said before. I just made it. I'm going to make a recreation of some of the battle on Hoth from Star Wars made out of k'nex with it.


    14 years ago on Introduction

    Use the resize filter to make the video smaller. and adjust the framerate. Use XviD, Microsoft Video 1 is THE WORST CODEC EVER!!!


    14 years ago on Introduction

    Interesting. Just so you know though, Very few people have those motors. If possible, You might want to modify the instructions to make them for that standard ren motors, most people have those. Interesting Idea!


    Reply 14 years ago on Introduction

    i dont think the green cyber knex motors are very rare, you can get them off ebay quite easily and cheaply, on the other hand if you have only a basic knex set then you might want a modification so your motor would work on this model, another good motor that would work would be the gray plug-in motor that would never run low on battery.


    Reply 14 years ago on Introduction

    I don think they are all that common though. The set they came in sort of fell through so its not being made any more. I looked on ebay, and I could only get them for 60 of more dollars without shipping.


    Reply 14 years ago on Introduction

    really?, i found some on there for £20 and they include all the other cyber knex stuffs with them, but i can see where you are coming from, the set was made quite a long time ago and you cant get them in the shops anymore, and somone who hasnt been building knex for as long as some of us when the sets were in shops would say they were rare because they didnt buy the sets at the time. so i guess you could call them rare, was that the american or uk ebay?


    Reply 14 years ago on Introduction

    And 20 pounds is like $50 my currency, so its a bit of a difference.