The 3D model of the 2in track piece gives a pitch of 28mm approx 1.1 inch. Is that close enough for modelling?
I’d say it’s not … a .03" discrepancy multiplied by ten or more track segments would really start to add up. “Someone” should tweak the length of the 3D model. 
I know you all have seen this, but here is a really solid example by EddieB using foamies to help support the vehicle:
lynxmotion.net/viewtopic.php?t=1823
To attempt to summarize what is being said here, the design in that thread could be optimized by raising the sprockets off the ground and just leaving the foamies along the bottom. But is it really necessary in a little rover? I guess each modeler needs to decide that for theirself.
I think I’m starting to grok these tracked vehicles… but I’d really *love *to see a pic of the latest prototype taken perhaps from the bottom with the tracks removed which shows how the motor, hub, sprocket, idlers and panels are all interconnected. I’m ready to order my tracks (and electronics), but I’m still not 100% sure about what all I need on the mechanical side. 
Listen,
These tracks are great. IMHO you dont need to have all of the pieces put together in you mind before you leap. In fact, I am changing my original prototype for the 3rd or 4th time based on some the excellent examples shown here. Thats one of the best parts about building these things.
You take the collective brainiac power often shown here, add in some lynxmotion parts, some custom parts, some local hobby shop parts, blood, sweat and voila.
Try - try - try. Your thoughtful questions are evident of that. But given what I’m reading, your ready to buy - buy - buy. Get some track in hand and fantisize from there. You wont be dissappointed.
nough said
FYI - I have some pictures of the track system I’m making comin soon
Good luck
I hear ya! I’ve had my cart full a few times, and I’m ready to checkout. There are so many different kinds of bots to build that I just want to make sure I’m getting the right stuff. I’m going to make an order from lynxmotion.com after work tonight though.
I’ll be on the lookout for that and hopefully have something of my own to show in a few weeks when all my parts roll in and I get time to build! 
Now thats a story we all know. Since day one I’ve wanted a Humanoid, a Hexapod, an Octopod, a Tracked Bot and…
There are as many web sites as Robots that I really want and it kills me to decide what to do next. For a hobby, its a lot of money…
If 6 pieces fit perfectly around a sprocket then that would form a perfect hexagon. If thats the case then drawing a line from the centre of each rivet to the centre of the sprocket would form six equilateral triangles. Each side would be 1.07 inches therefore the diameter would be 2.14" from rivet to opposite rivet.
I think… (The missus is a maths teacher and she says thats right)
According to the missus
If 9 fit perfectly round the sprocket then…
Radius = 0.535/Sin(360/18)
Smart way to deduce the info. I will add it to the website.
I started out just wanting to build my Walk 'N Roll, but heck, now I want one of every type and I am building a custom biped now. 
I wasn’t interested in building a biped at all when I started out, but my Bipod has some hybrid features to it - it has legs that can walk hexapod style as well as humanoid style. I basically just added a fourth joint to an SES 3DOF style custom hexapod leg, and the leg design is about to undergo its 5th major revision. I am sure glad I have a good 3D CAD software package.
8-Dale
I have added the pitch diameter of the two sprockets to the website. Thanks for the help!