Clutch Tuning - Ulmer Racing Clutch stuff? Others?

[RJH]

WOW - good looking photo. Thanks

The Cat arms look good from the picture. I like that type of product.

I can't tell with the Yamaha - the area of concern is above the first rivit after the pin hole. See how it looks kind of flat.

I tell you what - they are good - its just me - who lives on every mm of surface of a clutch ramp!!!

If I feel the slightest bit of lost effeciency - well its a sickness I guess.

I'll ask the dude if they weldable.

 

[K-fab]

 

[RJH]

Ok – I found my notes - a 9T driver is 22.68 circumference. (they take the lugs into play)

Sled Example Only

Let say he spins at 11000 RPM
Let’s say the clutch is at 1:1
Let’s say our chain is 2:1
Driver – 22.68

11000/2 X 22.68/12 X 60/5280 = About 118 MPH (LOL)

Your Trick Car

11,000 RPM
Clutch 1:1
Gear Box 8:1
Wheel – 92.6

11,000/8 X 92.6/12 X 60/5280 = About 120 MPH :ORC

So unless you are running down the highway, with the wind, you may need at least a 13:1 or 15:1 to give the clutch a chance.

 

[K-fab]

Ok – I found my notes - a 9T driver is 22.68 circumference. (they take the lugs into play)

Sled Example Only

Let say he spins at 11000 RPM
Let’s say the clutch is at 1:1
Let’s say our chain is 2:1
Driver – 22.68

11000/2 X 22.68/12 X 60/5280 = About 118 MPH (LOL)

Your Trick Car

11,000 RPM
Clutch 1:1
Gear Box 8:1
Wheel – 92.6

11,000/8 X 92.6/12 X 60/5280 = About 120 MPH :ORC

So unless you are running down the highway, with the wind, you may need at least a 13:1 or 15:1 to give the clutch a chance.

Now this is EXCELLENT info!!!
I have 10:1, 9:1 and 8:1 gearsets that I can drop into my tranny.

Using the formula above:
With a 10:1 I would have a top end of 96.5
With 9:1 I would have a top end of 107.3

At 10500 RPM
8:1 would be 115.2
9:1 would be 102.4
10:1 would be 92.3

BUT, doesn't the driven clutch on the RX1 engine have a reduction? - so the actual rpm of the clutch is less - I'm not sure, but I think it's a 3/4 reduction?

11000 engine rpm would yeild 8250 clutch rpm
8:1 would be 90.5
9:1 would be 80.4
10:1 would be 72.4

10500 engine rpm would yeild 7875 clutch rpm
8:1 would be 86.4
9:1 would be 76.8
10:1 would be 69.1

 

[Srxspec]

Gear Reduction on the RX-1 is 37/31.

10,500 engine RPM = 8797 clutch rpm

Engine RPM / (37/31) = Clutch RPM

 

[K-fab]

Gear Reduction on the RX-1 is 37/31.

10,500 engine RPM = 8797 clutch rpm

Engine RPM / (37/31) = Clutch RPM

Cool - even more, better info!!

I'll have to go plug in the numbers again.

10500 engine rpm will yield:
8:1 gearset = 96.5 mph
9:1 gearset = 85.8 mph
10:1 gearset = 77.2 mph

I'll start out running the 8:1 ratio (that makes life easy, as it's what's in the tranny)

I got the clutch parts this afternoon and just opened the box.

The parts look sweet - I love machined stuff (I have a small machine shop - so it's sort of a passion).

Looks like I'm gonna play with a primary clutch tomorrow and then see if I can find a place to start messing with the computer and the FI mapping. Even w/o a dyno, I think I can make changes that, at least, do SOMETHING -maybe good, maybe bad. I'll never know until I start messing with it and learning how this stuff works.

Thanks for the help guys!

 

[Philabuster]

Now this is EXCELLENT info!!!
I have 10:1, 9:1 and 8:1 gearsets that I can drop into my tranny.

Using the formula above:
With a 10:1 I would have a top end of 96
With 9:1 I would have a top end of 107

At 10500 RPM
8:1 would be 115
9:1 would be 102
10:1 would be 92

BUT, doesn't the driven clutch on the RX1 engine have a reduction? - so the actual rpm of the clutch is less - I'm not sure, but I think it's a 3/4 reduction?

11000 engine rpm would yeild 8250 clutch rpm
8:1 would be 115
9:1 would be 102
10:1 would be 92

10500 engine rpm would yeild 7875 clutch rpm
8:1 would be 86
9:1 would be 76
10:1 would be 69

I may (and I already was considering) drop in the 9:1 gearset.

May I make a few corrections to your numbers?

The gear reduction in the RX-1 is 1.1935:1, so that means 10,500 engine RPM would be 8,798 drive clutch RPM.

My vehicle is also geared using the same 8:1 gearbox as K-Fab. My rear tire diameter is 31". Using the online gear calculators (I'm lazy), my final drive MPH at 1:1 clutch drive/driven ratio is 101.5 MPH @ 10,500 engine RPM. Even with the engine not jetted correctly and using the modified RX-1 clutch weights (way too heavy--engine was at 9,800 RPM), I was able to hit 94 MPH on the GPS on my first shakedown trip to the desert.

Tire diameter: 31
Diff Ratio: 8:1
RPM: 10,500
Transmission Ratio: 1:1
TransferCase Ratio: 1:1935 <--very important for the RX-1
MPH: 101.5 <--Calculated speed based on the 5 inputs above

http://www.4lo.com/calc/gearratio.htm

Here is the calculator for the sleds. This is of no use to us 'car guys' except to confirm the PTO shaft reduction value.

http://www.snowmobileworld.com/tools/index.php

IMHO, run the 8:1 gears for now, but keep the secondary clutch from shifting out soo soon. You have WAY more bottom-end torque than before. Even with my clutching issues, I can light up my 31" tires at will.

I certainly would not go with the 10:1 gears unless you just like going slow.

EDIT: Well it looks like I type slow. :exc:

 

[RJH]

You need to READ folks...............

We didn't say RX1 setup - we said SAMPLE SLED SETUP - It could have been a Phazer - the math was for comparing only!!

By the way - I like the looks of those weights.

The math RPM was at 11,000 but.........

If your the engine clutch is spinning at 8797 then yes - your speed is 96.42 mph

My SAMPLE was with a 9 tooth driver - I have no idea what is on the RX1 - it dosen't matter -so no need to reply on that please.