strange pinion problem
 

hi everyone. i own a non worlds bj4 and have fitted an LRP Sphere comp 2007 with an x11 6.5t motor. i was told to run a 14t pinion but when meshed correctly the motor is too close to the drive cup which is rubbing against the motor :wtf:. has anyone got any solutions?? or ideas/reasons?

thanks very much

14 is a bit small

i run a 19 pinion with my 4* (bout 5.5 i believe)

see what others say

what size spur are you running ???

i think its a 78 but am not fully sure

well i used to run my 6.5 in my S4 (same drive train as bj4) on a 18/81 so if your running a 78 spur the put it on a 17 or even an 18 ..

78x17 would give you a overall ratio of 10.323
which isnt to fare of for a 5.5 4*

ive got 78x17 as a ratio of 11.47 ??? thats for an S4

Sounds a bit over geared does that carl??
Last year I was told to run 13:00 overall ratio by Jurgen himself with the 3star. thats a 15t pinion on the Worlds car. At the weekend I was running the 5.5 motor in my Tamiya 501X with 12.6 ratio (15/87)

so are you saying i need a 16/17t pinion with my x11 6.5 and 78 spur??

yes matt , thats what i would be looking at running. try 16 1st see how you get on ..

sorry for this but the spur is actually a 72

so im guessing by that the 14t pinion is actually correct then :wtf:. so has anyone got ideas on what i could do to stop it rubbing on the drive cup??

okay, im very confused now lol

i would change the spur to be honest matt ..

same i would put the spur up to something like 78 or even 81. Then i would increase thje pinion size by a few to around 16-17 maybe higher.

this is on my non-worlds car, and am not sure a 78 or 81 will fit as the 72 is almost level with the chassis already

Get a Worlds Edition!

I never ran anything smaller than a 17t on the origonal car but I think that fitted no problem. Based on how I've been gearing my 5.5 recently i the WE you might get away with a 15t, but 14t is what you want to gear it on really.

I think RW make some white machined spur gears that you can get in 73/74 ect that would fit, so long as it doesnt stick out below the chassis you'll be fine.

i would, but they cost more money, of which i dont have :(. with a 14t pinion i get a final drive ratio of around 12.85 which is bang in the middle of what LRP recommend, with a 15t it comes out at 12, will this still be okay?? as LRP suggest 13.5:1 for high traction tracks and 12.5:1 for low traction tracks.

I gear my 5.5 X11 at 12.65 (16/81 in the WE).

12:1 might be a bit on the high side, put the smallest pinion you can fit on and run it for a minute or so, stop and check how hot it is.

do yoo think it will be ok if i fit a fan to the motor?

fitting a fan to the motor wont do owt, you need to fit a fan to the esc as thats what does the work now.

It's probably more the speedo thats going to get hot I would think.

thats where my second problem comes in, i have no way of cooling the speed control within the limits of the chassis and shell space [if that makes sense] i have no space to put a fan on the speed control as if one were facing across the fins of the heatsink then it would stick off the side of the car, if one blew on the side of it then it would make no difference.

Put the reciever on the top deck? I managed to get a KO reciever, Quantum 2 and a 35mm fan blowing at the motor between the back of the servo and motor endbell no problem in my origonal BJ4.

http://www.oople.com/rc/photos/nif20...es/nif008.html

i'm not having that, i've just squeesed an mtroniks genesis pro in to my bj4, and ive even fitted a fan on top of it - and it still has the big power cap fitted.

If i can fit that, i'm sure you could get a 2007 in yours, even if it is an original car!:p

right, ive got the reciever on top deck already, i have a normal size servo, its just the sphere is so tall, if i put a fan on top it will obstruct the shell, and it is facing the wrong direction for me to fit one pointing over fins of the heat sink, so i dunno what to do, as if i turned it round, the wires wouldnt properly fit and the board with the wires soldered onto would be nearly hitting the motor. i would put up a piccy but im embarrased with the motor soldering, haha

o yeah, and rich, the fan could fit there but then it would be blowing into the side of the speedo and heatsink, not across the fins

okay, i think i have it sorted. now i just need someone that is good at soldering that can make a good job of my speedo to motor soldering... anyone offering?? :D

Yep, a bigger spur is the hot ticket here my friend! :cool: