Part 1 - Using C-Clamps
C-clamps work very well in connecting two modules together. You want to be able to get the C-clamp as far up into the underside of the two modules so that you are clamping as close to the top of your module as possible.
C-clamps are classified as 1", 2", 2½" etc in North America. This refers to the extent to which the screw of the C-clamp will open. What you really need to measure is the "throat" of the clamp - ie the distance from the screw to the side of the C. Or to put it another way, you want to measure the extent to which the C-clamp will get up into the module. The only way you can determine this before you buy C-clamps is to use a tape measure.
For example, here in Canada, our Canadian Tire stores sell a "2½ inch" C-clamp which has a throat that measures 3". This means I can get that C-clamp 3" up into the underside of the two module frames. I can also buy a "3 inch" C-clamp from Busy Bee Tools but this only has a throat of 2". This means I can only get that C-clamp 2" up into the underside of the module frames. The difference between the two clamps means that I can get the "2½ inch" C-clamp a full 1" closer to the top of the module than I can with the "3 inch" C-clamp.
Part 2 - Connecting Tracks Between Modules
There are two ways to connect the tracks between the modules. The method you use will depend to a certain extent on how many times you are going to move the modules and how much time you want to spend installing "joiner tracks" between the two modules.
The easiest way to make the "rail connection" between two modules is to simply lay the track across the two modules and then cut the rails (tape a couple of strips of duct tape between the two modules to account for the thickness of the saw cut.). However, you might end up with problems when you come to align the two modules, particularly if you have several track running across the modules.
The second way to connect the tracks across modules is to use a "joiner track". A joiner track can be as simple as a short 3" section of Atlas snap track or can be as complex as specially fabricated PC boards with rails soldered to the copper strips. For example, assume you will be using a 3" Atlas snap track to span the gap between the two modules. The track on each module will end 1½" from the end of each module. Slide a couple of rail joiners onto the end of each rail. Insert your 3" joiner track (1½"+ 1½" = 3") between the ends of track on each module and slide half of the rail joiners onto the joiner track. Voila, the tracks between the two modules are now connected.
Part 3 - Bridging the Gap
If you are in a club, you will be building your modules to standards or to a plan. This means that your track will have to be accurately located at each end of the module. For example, at Ottawa Valley HOTRAK, the track on my single-track Free-mo modules has to be located exactly 12" in the middle of the module. The track on my double-track conventional modules has to be located 2½" and 4½" from the front edge of my modules.
However, if there happens to be a gap between the end of my track (or the end of the track on the other module) (ie the distance between the modules is more than 3", assuming we're using a 3" joiner track), it's a simple matter to cut a small bit of rail, slide it onto the end of the rail joiners and then install the joiner track. Or, if the distance is shorter than the 3" joiner track, cut a bit off of the joiner track.
Part 4 - Making Sure The Track Doesn't Move
When you clamp your modules together, the two modules become one unit. No need to worry about the modules moving and hence no need to worry about the tracks moving. However, when you disassemble your modules, make sure you remove the joiner track before you undo the clamps. Otherwise, the modules will move, your joiner track could get damaged and the trackwork on your modules could also get damaged.
To minimize damage to the trackwork on your modules, install two track spikes in the last tie on both sides of each rail that will go across to the other module at the end of each module. Also, if you are using snap track or flex track with a plastic tie, install a pin in the middle of the last plastic tie at the end of each module. This will minimize any damage to your trackwork should the modules move when you don't want them to move. Damage almost always occurs when assembling or dismantling the modules and someone, in their haste, forgets to follow a proper sequence. Damage almost never occurs to the trackwork once the modules have been properly assembled and clamped together.
Bob M.