Tech help needed: Gears?

[ChallengerGuy]

OK, so in thinking about my running on the big commercial track I discovered my Lancia (factory Slot It inline set up, yellow crown gear) was topped out on the back stretch...other cars had more legs...So while they may have had 30K motors compared to my 21.5K factory job, is there a way I can level that playing field a tad?

[waaytoomuchintothis]

This is easy. Your car has the standard 3:1 ratio that comes from a 9 tooth pinion and a 27 tooth crown. If your car has any time on it at all, it is running 22,000+rpm at the motor, so at top end, you have roughly 7300rpm at the wheel. If you only change the crown gear to 24 tooth, you get a 2.66:1 ratio, and that translates to 8240rpm at the wheels, and that's a huge boost. The reason this works so easily is that you are already moving when you go for top end, which eliminates the problem of low end torque with a tall gear. Want more top end? Look at a pinion swap to a higher tooth count, but watch out for the ratio. At an 11 tooth pinion meshed with a 24 tooth pinion, you are dragging a 2.18 ratio, and you motor won't last more than a few races. Keep the car as light as you can, get all the traction you can, and drive with as much conservation of energy as you possibly can. You'll make the long straight your own territory. As always, completely ignore every car on the track but your own- drive your own race. The rest of the field will tell you when you win.

[ChallengerGuy]

Thanks!!!

[dr fabio]

The question that springs to mind is, why are you running 21.5k when the class allows for up to 30k? My rule of thumb for selecting gear ratios seems to work very well. If you are having to use your brake adjustment on your controller to lessen the brakes because its pulling up too hard then you are using too tall a ratio (i.e. 10/30 = 3.00) and you need to lower it to say 10/28 = 2.80. Keep lowering the ratio until you have just enough brakes for all the corners on the track without the need for the brake adjustment. If you dont have enough brakes and the car rolls on too much then increase the ratio, say you're running 10/26 = 2.60 then increase to 10/28 = 2.80.

This works well for non plastic non mag racing. For mag plastic racing then your guess is as good as mine.

cheers
dr fabio

[ChallengerGuy]

Thanks again...well, I am "run what you brung" at the moment so all I have are stock Slot.It cars. The track is wood, nice texturized surface and braided. My urethanes seemed to outperform the NSR tires so I am sticking with them. I will probably convert a couple of my cars to sidewinders with the longer gear to help on the open ended side of things. While doing so, I will invest in some 30K cans. Any suggestions on cans (aka motors) to buy?

[dr fabio]

Dont reinvent the wheel and just see what others are using. They have selected their motors by trial and error (and money). Use this knowledge and save on the money outlay.

cheers
dr fabio

[Cosmic Bilby]

[ChallengerGuy]

Thanks again - tomorrow (Wed nights) will be my first race night so I will look to others and see what they are using (you know, take spy shots of their cars!!) and otherwise just enjoy the ride. I have this crazy red can motor (I think it is an early MRRC red can like what I have in my Cobras) and it's installed in a Fly 917 Porsche. I will bring that beast and see what all happens.

[ChallengerGuy]

Oh, in looking over my toolbox, I had a couple of SlotIt (blue) 26 tooth inline gears handy. So, between those and the factory 28-tooth yellow ones (I counted - ugh), I should be OK to try a few things with what I have. But man, some of those NSR cars were blistering past me on the back stretch. I will have all the details tomorrow to share.

[waaytoomuchintothis]

You miscounted. Yellow is 27.

[ChallengerGuy]

I swear....hahaha...dang fangled tiny things. I think this means I am getting older. Sigh.

[ChallengerGuy]

SEE!!! The yellow is 28. I am not going blind. Phew.

[Dangermouse]

Too many teeth to count....I am saving that chart - save me counting teeth :grin:

[boopiejones]

I think you'll find that the only way to be competitive is going to be with a long can motor. I love the slot it orange motor, but it will be severely outgunned against a 30k long can on a big track.