Greetings forum and boy am I happy to finally found you.
A bit of background, I’m making a camera dolly tank for long exposure time lapse photography. The chassis is currently a wood prototype but contains an Arduino board, LCD, 12V motorcycle battery and a mount for a large DSLR camera. The primary use will be to run a sequence - take 30 sec photo, move 0.25 cm, take 30 sec photo, move 0.25cm, etc etc. So precision is key.
I’ve the chassis hooked up to a 2 x 9 link sprocket drive with 30 x 2" tracks. I’ve chosen this configuration because I need support at both extreme front and extreme rear positions to balance the weight and ensure a zero chance of toppling. I am open to suggestions however as my experience in tank design is pretty limited!
Anyway, to the point. With the above sprockets & tracks combined, I’m getting a terribly bumping ride. The sprockets ride over the larger track struts like a bump then drop down to a lower point for the thinner track struts. Too much to believe others are just accepting the sinusoidal journey, I must be doing something wrong. My terrible freehand paint impression below shows what I mean.
With the way the teeth are on the 9 link sprockets it almost like the only way I can get a smooth ride would be to sand down the larger valleys to the depth of the narrower valleys??
Surely I shouldn’t have to go to that extreme measure?
Would using the 6 teeth sprockets make a difference?
Any help at all would be very much appreciated, thank you!
Use the track rollers between the sprockets. If you install them in such a way as to support the weight of the robot on the track rollers instead of the sprockets, your problem will go away. I tried to take a picture of my track rollers to give you an idea of what I’m talking about. The Lynxmotion store sells white track rollers and 1.5" standoffs to use as axles on the rollers.
I actually came across your project thread after I posted this and figured that could be a solution… thanks so much for the reply - totally understood and off to make some modifications.
I’m going to have to disagree. I’ve also been plagued by the bumpy ride even though I have the rollers as you suggest. I was able to confirm this when I took the tracks and laid them flat, then I took both size sprockets and ran them up and down the inside of the treads. There was a noticeable bump due to the peaks in the teeth on the sprockets. I have a camera on my tracked robot, and the vibration is almost rendering the treads useless.
While I am still waiting for the standoffs and parts to arrive, I’m pretty confident what Machine27 suggested will indeed fix the problem.
You mentioned you ran the sprockets along the track and had bumps, as per my photo at the top of this thread, but if you try running the rollers along the tracks and not the sprockets the bumpy ride does indeed reduce dramatically if even noticeable at all. Try this - run a bushing on a screwdriver along the tracks and you will notice and very smooth ride. http://i782.photobucket.com/albums/yy101/gnathan/trackroller.png
I can say the white rollers that come with the tri-track kit do indeed make a difference. I bought two tri-track kits and prior to reading the directions I quickly put one of the kits together without the rollers & standoffs. When I attempted to run it, the robot looked like it was driving down a gravel road, extremely bumpy. After skimming through the directions on the second kit, I noticed the rollers that I failed to install on the first. When I installed them on the second kit and ran it, the drive was much, much smoother. Since then, unless I built the tracks with rollers the ride would be extremely bumpy.
If you are custom building your chassis, make sure to install the rollers correctly (similar to the position they sit on the tri-track kit from Lynxmotion). If you don’t, you will still get the bumpy ride. I’ve learned this with trial and error on my chassis prototypes I’ve built. I’ve had to rebuild the track mounts due to the roller positions being out of place.
Thanks for the feedback, i’ll take that heavily on board. What specifically are you referring to though in relation to the tri-track design? Is it simply not a case that the sprockets are raised and the rollers take the weight? Is there something else needed to be taken into consideration?
Many thanks everyone, this is helping me plan it out better
