International 15 or 15A has seen a significant resurgence in popularity. This is probably due to the fact that a fast setup is comparatively easy to obtain (certainly easier then G12), the maintenance is low, they don’t break easily, they don’t blow up easily, they are much less expensive then the cobalt classes and are fast and fun to race. The podium at the 2006 Nats in Expert 15A is very instructive in what is a fast setup. The similarities are striking and point to the fact that a fast setup is easy to identify. You can certainly experiment in 15A if you want to but it’s not necessary. Open the links to go to pictures of the podium finishers, courtesy of Old Weird Herald.
Chubbies Roller
www.oldweirdherald.com/photos/gallery/2006usrawingnats_exp_i15/DSC08759
Lamo’s Roller
www.oldweirdherald.com/photos/gallery/2006usrawingnats_exp_i15/DSC08762
Tony T’s Roller
www.oldweirdherald.com/photos/gallery/2006usrawingnats_exp_i15/DSC08764These pictures show every thing you need to know about 15A rollers, Beuf Xpress, length between 4.50 and 4.40, GT1 72 pitch angle pinion and angle plastic spur, 10/44 ratio. Run with weight in the nose, ½ inch square of lead. Koford WX or WXX big hub (or giant hub) drilled and waffled tires cut to the hub or a touch past it. Body choice has more variety, Serpent, Viper with and without Rib, Z28 with and without Rib, and the Hurricane. Body choice is a function of the type of track being run, speedway – Hurricane or Serpent, “driver” king – Viper Rib or Z28 Rib. Cut runs from 137/27 for a speedway to 139/30 for a “driver” king. Ultimately body choice is the major variable in accommodating driving style and track style and requires experimentation.
The most common motor setup today is a Bat Can with an SMF Endbell and either Proslot Monster quads or, if you can find them, RJR flat top quads. Airgap at .512. There are different Bat Can options out there, it actually describes a style of can maching developed by Doug Bauer at Port Jeff Raceway. The scalloped machining on the trailing edges and the end of the can reduce weight without degrading the performance of the magnets.The next two links show the machining.
Doug's original prototypes used as a base the Koford 15A strap, known for it's very good magnetic properties. He had the Bat pattern machined and in some cases had the can thickness reduced. These were being done at Koford however when the move occurred the stock of cans was lost. Koford eventually developed the CNC version as a replacement. Pix of the CNC can follow.
The Koford can has the side scallops but not the end scallops, for best performance the end scallops should be hand ground . Also the Koford CNC can is .480 tall. It doesn't need to be that tall and can in fact bind up the motor a little. More usable RPM's are obtainable by hand grinding the top and bottom of the can to something closer to .400 tall. If you are concerned about your motor building acumen then a good way to start is simply buy a couple of motors or setups from Doug at Port Jeff. He and Erkle build 15A motors and rollers for everyone. If your intention is to run OM15A in the NEUSRA then you need two motors max ( you can even get away with one motor initially).
The newest entrant to the setup wars is the Cahoza setup distributed by GT1, just like there cobalt setups the 15A setup goes together easily and accurately first time everytime. They use a feathered can approach instead of the scalloped bat design.
Armature selection is pretty simple, Koford .500 diameter 40 degree timing, end of story. Proslot arms were THE ones for a long time but the new Kofords are set to max kill. Again the best place to get them is Port Jeff, Doug sells more 15A stuff then the rest of the industry combined. That translates to market power when ordering, he gets the best, first and as many as he needs. For you conspiracy theorists, forget the bullshit about cherry picking, he doesn't nor does he need to. I have been there when arms come in and you can stick your hand in and pick what you want. The reason is that the arms are so consistent today that the magic is in the setup and matching an arm to the setup through trial and error (the hard part). They are fast not because they cherry pick, they are fast because they are constantly searching for and finding optimal combinations. This isn't a commercial for Port Jeff it's just reality. It helps keep the cost under control, because it simplifies the purchase decision and reduces the need for experimentation, which while being fun sometimes is usually always expensive.