Here is the finished buggy. Just have to cut the tranny brace in the morning ,bolt it on. wire the speedo and receiver in, and go for a test drive!!:sneaky:

do tell more about that "second pinion" please. neat idea....never thought of that....different way to get that 4 gear tranny effect.

that "second pinion" im pretty sure is a idler gear. you can get idlers with different tooth counts from associated.

i painted a new body forr my buggy. its a losi phobia body and the sides are higher so the battery will fit better.

http://i655.photobucket.com/albums/u...94/nov9010.jpg

http://i655.photobucket.com/albums/u...94/nov9011.jpg

http://i655.photobucket.com/albums/u...94/nov9013.jpg

http://i655.photobucket.com/albums/u...94/nov9014.jpg

http://www.youtube.com/user/academyrulz

Ok, heres some pics of the finished Academy gv2 mid motor buggy.No body yet.Also some video of it on the track. ENJOY!!!:sneaky:

kudos to you sir and your hard work paying dividends. i dont run that car, however always like a guy who takes time out to build somethin he can make his own.

R

Not too much to tell.You are just adding an idler between the pinion and spur to produce opposite rotation from the out drives. No different than what X-factory did, just in a different place in the gear train.Adds an extra step when callculating the final drive ratio of the car.

Actually 'idler' gears don't change the final drive ratio of the car at all. If you have three gears in a row, A driving B which drives C (like a typical buggy transmission, top shaft drives idler drives diff gear) the idler gear can be whatever size you'd like. Check it:
A drives B: ratio is B/A
B drives C: C/B
multiply them together to get the full transmission ratio: C/A

AE top shaft is 20 teeth, AE diff gear is 52 teeth; the transmission ratio is: 52/20 = 2.6

The number of idler gears doesn't change it at all either: they just keep canceling out, and only change rotation direction.

If it is put in line where X-factory chose to put the 4th gear yes you are absolutly correct. Where I chose to put mine unless you run a 28t pinion (1:1 ratio between the pinion and idler) you are either underdriving that external idler, or over driving the idler depending on pinion size.

A 28p to 28t idler ,as I have it placed, is a 1:1 ratio

A 30t pinion to 28T idler, as I have it placed, is overdriven. Which in this case is overdriven to 1.0714285 rotation of the idler = 1 rotation of the motor.

A 25T pinion to 28T idler, as I have it placed, Is underdriven . Giving a pinion to idler ratio of 1.12 revolution of the MOTOR to 1 revolution of the Idler.

So you see where I chose to put the same 28t Idler that tranny has internally DOES directly effect the gear ratio as opposed to just mating the pinion to the spur.

Where If i had chosen to go the same route as you folks at X-factory did adding the second idler does exactly what you described.Merely makes it a counter gear to reverse the outdrive direction.I was trying to take advantage of the placement to make the gearing a little more brushless freindly for those of us that like to run 17.5's but hate those gargantuan pinions .I normally run a 34/74 on my standard gv2 for a large track.This configuration has allowed me to drop to a 30t pinion for the same track.

this misunderstanding Is my fault. I am calling the gear I added an Idler , which now it is actually a counter gear in relation to the normal position of the pinion/spur.

OK, but unless I'm mis-understanding you, the idler you've added then drives the spur gear, and you have a set-up like I described above (A drives B which drives C). The gain/loss in rpm of the idler is lost because you have a smaller/bigger gear driving the spur gear.

Here are some close-up pics Of what I did Paul. You will see what I am not so perfectly trying to say(I know what I mean LOL) Current set-up I am running is 27T(pinion), 28T counter gear, 65T spur /slipper Gear. Iternal tranny ratio is 2.42:1.

Which yeilds a 5.8258537:1 final drive ratio. This was calculated by ; Spur div. by 'Idler'= 2.3214285
then
'idler' div. by pinion = 1.037037
then
2.3214285 x 1.037037 = 2.4074072

Then

2.4074072(ext. drive ratio)x 2.42(internal drive ratio)= 5.8259254:1 Final drive ratio for a 17.5. When for the same track with a stock layout Gv2 I have been running 31T pinion 74T spur (=2.3870967) x 2.42 internal ratio= 5.776774:1 final drive ratio.

so see it does involve an extra step when calculating the final drive ratio in the manner of first calculating the external drive ratio (Spur Div. by Idler) x (idler div. by pinion) to reach the input ratio which is then multiplied by the internal tranny ratio to reach the Final drive ratio.

Yes( ithink) I was taking from your post that we were not on the same page as far as the 'idler' in question.

Your math is correct, but as Paul said just divide the spur by the pinion and you get the same ratio. 65/27 =
2.4074074074074074074074074074074. The idler doesn't need to be considered when calculating the ratio.

See , leave it to me to overcomplicate something I did to make my life more simple!!LOL.

haha, i do that all to often. i may have to try this though. see how it works out. i have some ideas already...may not work right though.

May I suggest an easier explanation(at least for me... :) ).
Every time the 27 teeth pinion was turning a round, its moving the counter gear by 27 teeth too, following by the counter gear turning the spur gear again by 27 teeth.

So the spur gear was move by 27 teeth every time the 27 teeth pinion turn "a round". No different in gear ratio with or without the counter gear.

If 10 counter were to line up, each will send "27 teeth turn" to the next one, and the spur still ends up with moved by 27 teeth at the other end of the transmission, on every "round" of the pinion.

The only different will be the additional friction of bearings and gear teeth.