Gearing for rc12r5

Can someone please advise on gear ratio for 9T/60A hobbywing with A123 at wan chai track.
thanks!

Are u running 1S A123 (3.3v) or 2S A123 (6.6v)?  what is the diameter of the rear tires?  (in 1/12, gearing is based on rollout and the tire diameter is a parameter to calculate rollout.)

I never knew you could play 1S A123. I expect you have to have a very faster motor for this.

I intend to play 2S A123. As far as the rear tire diameter... i cant answer this yet, depends on what Fatboy delivers! I'm really looking for a rough range to start out with and slowly fine tune.
thanks hardmankam.

typical rear tire diameter is from 44 to 46mm... so here i will assume 45mm.
from novak website for a 8.5R motor with 4cell NiMh (4.8v), the rollout is 40mm.  In your case, if you use 2SA123, your rollout should be a little less, so maybe 37mm (just guessing).

here is the rollout formula:
(tire diameter) x (Pi) x Pinion / Spur = Rollout
or
Pinion = Rollout x Spur / (tire dia x Pi)

If you use 95 spur, pinion becomes: 40 x 95 / ( 45 x 3.14) = 27

thanks hardmankam.
I've ended up playing my r5 with 2s lipo from my 1/10 cars, as my old lipo's dont have enough punch anymore for 1/10, but more than enough for 1/12. Just did a little modify to fit the 1/10 lipo running 22/96 and 9T. Whats great is that the batteries last for a very long time 4,200mah, but the top speed too fast for me to play full throttle at wan chai track, therefore i set  the forward throttle to 70%.

Show us a pic of how you modify 2S lipo into a R5.

2s Lipo in Wanchai, 18/100 with 8.5turn brushless, rear wheel 44mm diameter
can be full throttle with good control

Initially i just used small cable ties through the battery mounting holes, but this limited the chassis clearance to the ground. so then i came up using a larger cable tie with a hole drilled through one end to clamp it to the chassis at the front, using the smaller screws/nuts that come with the r5 for the battery bracket. At the back I used some posts (i think come from L4 or RC10LS), this limit the battery movement and act to secure the cable tie with a screw through it. On the bottom I used some foam(sticky on one side), (easy/cheap to find from shops - wanchai got one near track) to raise the battery so it doesnt effect the links. Also needed to raise the shock a little...2mm is enough at front, back of shock doesnt actually need to be raised at all.

I'd be interested to see how other ppl modify their r5 for 2s lipo.

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2s Lipo in Wanchai, 18/100 with 8.5turn brushless, rear wheel 44mm diameter
can be full throttle wi ...
swswsw 發表於 2010-4-9 10:08

                               
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Hi swswsw,
thanks for the info. I was worried before about correct gearing/over heating etc before which is why i ran 22/96, but these 1/12 dont seem to be so fragile to run as 1/10 so I will try 19/96. because these 1/12 so light seems you can get away with pretty much any gearing you want. Will let you know how i get on. (will play Sunday at wanchai!)

Initially i just used small cable ties through the battery mounting holes, but this limited the chas ...
xiang 發表於 2010-4-10 10:59 AM

                               
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又真係幾好方法wo , well done !

又真係幾好方法wo , well done !
RC881 發表於 2010-4-10 01:06 PM

                               
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   Very Good Design!! Well Done!!!

excellent design!  good job.

thanks guys...
if it helps anyone else out... then great!
Definitely makes it a cheaper option if you already play 1/10 and want to play the 1/12(r5).
I was struggling for a while as I didnt want to have to fork out for 6 lipo batteries for the 1/12.
Now my old lipos dont go to waste, but i think, after these lipo's die, i will go A123 for all my rc cars. Then i suppose i can just remove the foam.

hardmankam... u gonna make it down to wanchai this sunday?

as the track in Wanchai is so small, i found the control will be much better in overall track if full throttle can be given in the straight line.... finally with team power (short version) 8.5T, 18/100 is the best.

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swswsw - Am i right in thinking i recognise your car? u often play in wan chai?

yes quite often previously, except these few months vocation period...

yes quite often previously, except these few months vocation period...
swswsw 發表於 2010-4-11 07:39

                               
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swswsw - Haha! i know you! Do you know who i am?

many friends down there in Wanchai, guessing u're one of them.....will come again very soon..

lucky u didnt play today... track very very wet! we all left early for some food!