Rear Pulley and Torque spring winding Question
- Thread starter DRXRACING
- Start date
tiba_karotsu
OVERREV TUNING
the different angles control the rate of gear change, 36degree makes the rear pulley split quicker (less resistance) & 38degree makes it split slower (more resistance). it's just like installing stiffer or softer vario springs, lighter or heavier roller weights.
the vario springs are wound in reverse to keep them from binding & preventing the rear pulley from splitting.
the vario springs are wound in reverse to keep them from binding & preventing the rear pulley from splitting.
Is there an example you could use to help me understand the benefits, or use of the different angles. To help me better understand?
I know stiffer torque spring is to prevent belt slipping, heavier/lighter weigths dial in the acceleration, etc.
I just have not been able to determine what occurs when I chose one slot over the other. But have had the better luck always chosing the one that is the most straight up and down. Not the one laid over the most.
It is another one of those areas I do not fully understand and haven't seen it explained anywhere before.
I know stiffer torque spring is to prevent belt slipping, heavier/lighter weigths dial in the acceleration, etc.
I just have not been able to determine what occurs when I chose one slot over the other. But have had the better luck always chosing the one that is the most straight up and down. Not the one laid over the most.
It is another one of those areas I do not fully understand and haven't seen it explained anywhere before.
tiba_karotsu
OVERREV TUNING
38 degree slot (steeper angle) is for engines with narrow powerband (peaky), it is like having the engine stay longer in 1 gear before you shift in a manual transmission.
36 degree slot (shallower angle) is for the engines with a torquey, linear powerband, it makes the transmission shift to high gear quickly for best acceleration.
i fitted a Malossi torque driver on my aerox, i chose the 38 degree slot b'coz it has an untuned stock 50cc cilinder with a Leo Vince TT pipe, with a Malossi yellow vario spring & 21.7g total weights it runs exceptionally well, the engine is always in the powerband even when the vario springs start to lose tension from heat degradation.
36 degree slot (shallower angle) is for the engines with a torquey, linear powerband, it makes the transmission shift to high gear quickly for best acceleration.
i fitted a Malossi torque driver on my aerox, i chose the 38 degree slot b'coz it has an untuned stock 50cc cilinder with a Leo Vince TT pipe, with a Malossi yellow vario spring & 21.7g total weights it runs exceptionally well, the engine is always in the powerband even when the vario springs start to lose tension from heat degradation.
Hi Drx & Tiba, I hope you don't mind mind me joining
the class late. I've always been confused by this as well.
I have some questions on your answers..
If the engine has a narrow power band, wouldn't you
have to shift quicker/more often? Then, as you describe
the effect of the angles, the shallow one (36) would seem the
right choice?
Also the other way.. with wide power band, you would have
to shift less often, so so from your description the 38 would
be best?
I think I'm interpreting something backwards, but I don't
know what.
the class late. I've always been confused by this as well.
I have some questions on your answers..
If the engine has a narrow power band, wouldn't you
have to shift quicker/more often? Then, as you describe
the effect of the angles, the shallow one (36) would seem the
right choice?
Also the other way.. with wide power band, you would have
to shift less often, so so from your description the 38 would
be best?
I think I'm interpreting something backwards, but I don't
know what.
Joël
Weight kills accel
The spring delivers an axial force to the mobile pulley.
This force must be "transmitted" from the slots to the pins in the fixed pulley.
These slots divide the spring force in a rotating component and a axial component through their angle.
Of course, the bigger the angle of the slot with the spring direction, the larger is the force needed to move the mobile pulley in axial direction.
So it's an adjustment that is comparable with mounting a stronger spring.
As tiba puts it, more restistance in the opening of the back pulley.
The larger angle gives a better pickup and can prevent rpm drops during acceleration. But, if the resticance is too high engine rpm will raise too quickley at higher speeds and you'll lose power and speed.
tiba_karotsu
OVERREV TUNING
you are thinking manual transmission here, if you let the engine with the narrow powerband shift too quickly it will fall out from it's powerband & rpm drop occurs, you lose acceleration & topspeed in the process b'coz the gear ratio on the transmission will be too tall for the engine to pull that's why a 38 degree slot is selected for a peaky engine like a 50 or 70cc & even more so especially with a standard rear pulley diameter.
this is why old GP 50cc racing engine of the past have 14 to 21 speed gearboxes to keep it in the powerband .
tiba_karotsu
OVERREV TUNING
Thanks for all the great info ! I'm gonna chew on it for a while and try the different pulley slots once again to see the difference.
38* angle is the larger angle(More straight up and down) and the 36* is the smaller angle(More laid over) correct?
I want to make very sure I interpret the replys correctly.
I have a 120cc engine to build , 2- 117cc engines and a 2- 90cc engine. All will use the overange rear malossi pulley . And Malossi front variator 5112075. All jog motor style, going in ATV's.
38* angle is the larger angle(More straight up and down) and the 36* is the smaller angle(More laid over) correct?
I want to make very sure I interpret the replys correctly.
I have a 120cc engine to build , 2- 117cc engines and a 2- 90cc engine. All will use the overange rear malossi pulley . And Malossi front variator 5112075. All jog motor style, going in ATV's.
tiba_karotsu
OVERREV TUNING
yup, you have grasped the concept mijn vriend. happy tuning.
