• We are no longer supporting TapaTalk as a mobile app for our sites. The TapaTalk App has many issues with speed on our server as well as security holes that leave us vulnerable to attacks and spammers.

Apex Mountain Gearing ???

HAMMER

TY 4 Stroke Guru
Joined
Nov 2, 2004
Messages
827
Location
Oregon
Anyone heard what the "production units" gearing is going to be ???
 

In my owners manual it says it is 20/40 gearing. I have not taken the chain case apart yet.

Randy I am going to run a Team clutch on my Apex, any idea what helix I should start with? Thanks Paul
 
Thanks for the info... ;)!

This is my first 4-Stroke and I have no idea how it's going to react to clutching so I couldn't be much help to anyone at this point... I'm a quick study though... My wild azz guess with 10lbs boost and a huge 16x162x2.25 is that I'm going to have to squeeze that belt pretty hard to keep it from smoking in the clutches... The 3-pitch drivers Yamaha is using are 7-lug from what I understand, which are 1" larger diameter than 2.52-pitch 8-lug drivers, so I might even go 42 bottom if holding onto the belt in the steep & deep under max-load becomes an issue... Now, getting down to the nuts-n-bolts... I'm going to start with some parts I already have laying around a Blue 120/300 in the P85 primary, 70grams, and a Black/Red 155/222 in the TEAM with a straight 52* helix... I should end up under revving... Once I get it on the snow and see how it reacts under Low-Med-High loads I'll work the numbers from there...

Happy Tuning... :D
 
Stuff I was thinking about today.......did some math.

Standard Sea-Level 14.7psi + 10lbs boost = 24.7

Altitude 10,000ft 10.1psi + 10lbs boost = 20.1 -- Loss of 12.3% @ 10,000ft

(Boosted) 12.3% at 10,000ft…240hp x .123 = 29.5hp…210.4hp

600lbs / 210.4hp = 2.85 lb per hp

(Normally Aspirated) 30% at 10,000ft …200hp x .30 = 57hp…140 hp

500lbs / 140hp = 3.57 lb per hp

RX-1 Mountain (1:1 Clutch Ratio)

31/37 gear reduction (21/40 stock chain case)
9,800 x 83.7% = 8202 clutch rpm (82.20mph)
10,000 x 83.7% = 8370 clutch rpm (83.89mph)
10,200 x 83.7% = 8537 clutch rpm (85.56mph)

APEX Mountain (1:1 Clutch Ratio)

30/37 gear reduction (20/40 stock chain case)
10,200 x 81.1% = 8272 clutch rpm (82.25mph)
10,500 x 81.1% = 8515 clutch rpm (84.66mph)
10,800 x 81.1% = 8758 clutch rpm (87.08mph)

Drivers
 
To get circumference multiply the amount of driver teeth by the pitch.
Then take the circumference you get from that and divide it by 3.14

7 * 3 = 21 / 3.14 = 6.68"
8 * 3 = 24 / 3.14 = 7.64"
9 * 3 = 27 / 3.14 = 8.59"
 
8 * 2.52 = 20 / 3.14 = 6.42"
9 * 2.52 = 22.68 / 3.14 = 7.22"
10 * 2.52 = 25.20 / 3.14 = 8.03"
 
Here is a boost calculator that I made to simplify horsepower projections with altitude. If you want to see what the normally aspirated setup makes at altitude, put in a zero for boost. The base hp calc is to determine what the base hp is if you know what the boost and the boosted hp is. I threw that together to try to get an idea of what the new Polaris FST was going to be capable of. I read somewhere that the FST makes 138 hp at around 12 psi of boost. Whith that in mind, the normally aspirated hp is 76 so it looks like it would take about 25 psi to make 200 hp on that thing.

http://www.ty4stroke.com/download.php?id=10224
 


Back
Top