by chrisguyw » Mon Sep 23, 2019 4:56 pm
Hello 3nickel, First off, gear mesh set-up is no different for magnet or no magnet racing....the gears don't know the difference ;)
For inline, sidewinder, or, anglewinder configurations there should be just a tiny bit of "lash" free play between the pinion and crown/spur gear. As long as there is even a tiny bit of free play (all around the gear) you are good to go.
Once you have the gears installed, turn the rear tires to feel just a bit of free play between pinion/spur....spin the rear tires so the gears move a few teeth, and check again.....repeat this process checking around the complete circumference of the crown/spur. At no point should the spur "bottom out"....this will result in unnecessary friction, it will wear both your axle and motor bushings prematurely, and, will cause the motor to overheat, and potentially fail.
You may find that there is a slight difference in "lash" at different points on the gear.....this does occur, as not all spur gears are perfectly concentric, and sometimes, pinions are not installed correctly, and "runout" can occur.
You certainly can invest in much better quality pinions/spurs/crowns,....and, a good quality pinion press/puller, but, with a bit of fiddling, you can improve the mesh on stock gears.
If the gears are tight.......and I am hoping it is the gears, and that the bushings are not misaligned, rear tires are not rubbing the chassis or pinion, and that both rear bushings a correctly seated in the bushing cups.......if all the previous points check out, you can use a hobby knife or a small round file to remove a tiny bit of the plastic on the front edges of the motor pod where the motor snaps in, this will allow the motor to move just a hair forward in its housing....take a tiny bit at a time, check, and repeat until you have some gear lash at all points as the gear rotates.
If you do happen to take a bit too much off, resulting in the motor moving in its mount, you can use a drop of ShoeGoo etc. to secure the motor.....securing the motor with motor screws/ShoeGoo etc. is a very, I repeat, very, good idea regardless of how secure the motor feels in its housing.
As far as weight, there is no absolute correct answer,.....it will depend on such variables as,...motor, tires, gear ratio, track grip, track voltage, and, track layout. As a general rule, I build my cars with no weight added, and then track test. If the car pops out or deslots at the nose of the car, a couple of grams at the front,( behind the guide or at the front of the chassis sides) will help. If the car lacks traction, a bit of weight towards the rear of the car (back edge of chassis sides, or wherever there is space) will help. Weight placement can get a bit more complex, but, this is a good general starting point.
Too often folks rush to add weight to overcome handling issues without trying to discover the inherent cause of the problem.......I have seen countless cars at our local clubs', or, cars brought into the shop that are loaded with weight, but, have un trued tires (front and rear), twisted chassis, poor guide set-up, etc.etc., and once remedied, a ton of this weight can be removed......so, once everything else is sorted, use weight as a final tuning element,....not to overcome fixable issues.
A lighter well tuned car, will always be quicker than a car loaded with weight to mask inherent issues ;)
Tire truing, chassis flex, guide placement , etc, are all additional elements that will drastically affect the car,.....but,....these are different topics :D
Hope this helps, and let us know how you make out, or, if you need more info.
Cheers
Chris Walker
Last edited by
chrisguyw on Tue Sep 24, 2019 8:01 am, edited 2 times in total.