Lynxmotion modular track system and sprocket question

Hi,
I continue my Wall-E project. I received a track and a sprocket to have an idea and to test.
Before my new order, I have a question about sprocket and idler hub.
For my project, I will use the 3" track (http://www.lynxmotion.com/p-512-mts-track-3-wide-x-21-links-23-single.aspx) and either 15T or 18T sprockets for rear (and motorized) wheels and certainly the 12T sprockets for front wheels (http://www.lynxmotion.com/p-1113-mts-18t-sprocket-6mm-hub.aspx). I need to have 2 sprockets side by side by track (2 for rear wheel or 2 for front wheel).
Since it already exists a spacer for 9T or 6T sprockets (idler hub : http://www.lynxmotion.com/p-609-passive-idler-hub-3-pair.aspx), is there the same thing for the larger sprockets ? Or, may be, it is compatible ?
Or do you have a suggestion to do that ?
Thanks,
Nicolas

To confirm, you’d like to know if the 3" passive idler hub is compatible with two MTS sprockets? Unfortunately the spacing is off and the teeth do not seem to line up. However, you could 3D print (or cut) an appropriate width spacer. Ideally though in order to mount two MTS sprockets side by side (with 6mm hub), you need a 6mm diameter shaft supported at either end, and separated using either 6mm hubs or clamps (or set screw collars). If you can, support the shaft using ball bearings. A pillow block with a ball bearing with 6mm bore would be best, but we do not seem to carry any at this time.