clarification needed on driven clutch tuning ( spring colors)

[bob58o]

What I describe is for low end torque. Pulling Stumps.

Others have talked about raising the engagement rpm for a better hole shot.

I guess the difference is TQ vs HP?
Raising the rpm seems like adjusting a two-step launch rpm on a turbo track car, where trap time is much more important than what I consider “grunt”.

Tires and tire pressure, track prep, … all play a factor.

 

[panchothedog]

What is the tooth count on your torque converter sprocket? Most come with a 10 tooth sprocket ( when using a #420 chain ). You can go down to a 9 or 8 tooth sprocket. Both are commonly available. Either one of these will give you more low end power as well as lower your top speed. The 9 tooth will increase pulling power and decrease top speed by about 10%. The 8 tooth by 20% as compared to using a 10 tooth. Neither of these will alter clutch functions or shifting rpm. You are just simply gearing the kart lower. Much easier and cheaper to change the small drive sprocket instead of the larger axle sprocket. You can usually adjust for chain length by sliding the motor, as compared to cutting and removing a link.

 

[mouthfulloflake]

What I describe is for low end torque. Pulling Stumps.

Others have talked about raising the engagement rpm for a better hole shot.

I guess the difference is TQ vs HP?
Raising the rpm seems like adjusting a two-step launch rpm on a turbo track car, where trap time is much more important than what I consider “grunt”.

Tires and tire pressure, track prep, … all play a factor.

exactly, I want low geared stump pulling, not a hole shot.
I have an old suzuki quad 4 wheeler, it stays in low usually ( 1st gear) and often Ultra low 1st gear.
So I am too familar ( spoiled) with ultra low gearing)

 

[mouthfulloflake]

What is the tooth count on your torque converter sprocket? Most come with a 10 tooth sprocket ( when using a #420 chain ). You can go down to a 9 or 8 tooth sprocket. Both are commonly available. Either one of these will give you more low end power as well as lower your top speed. The 9 tooth will increase pulling power and decrease top speed by about 10%. The 8 tooth by 20% as compared to using a 10 tooth. Neither of these will alter clutch functions or shifting rpm. You are just simply gearing the kart lower. Much easier and cheaper to change the small drive sprocket instead of the larger axle sprocket. You can usually adjust for chain length by sliding the motor, as compared to cutting and removing a link.

Yes, I need to count that one, the axle sprocket is already large enough that its close to stuff I crawl over, even with 18" tires
My guess it is whatever came stock on this Yerf Dog 30002, since the rest seems to be stock stuff.

I assume that to be a 10 driver, 60 sprocket.

My property is not a pasture, or a yard, its the Ozarks, and its rocky, hilly, leaves, stumps, hidden ditches and furrows, so going 30mph in a kart is basically beating you into pain until you loose control and hit something or flip haha.

TO me, some lower speed, more grunt, low end crawling around with a 15-20 mph top speed would be way more useful.

I have dirtbikes for when I want to break the 20mph barrier

 

[panchothedog]

One of my karts is also a Yerf- Dog. Probably the same model as yours. I know that it's 5 didgets in the model number and it starts with a 3. Also has the 7" driven clutch where most are 6". So probably the same kart. I know mine came with and still has a 10 tooth sprocket. We run out in the Southern California desert that is pretty flat, so I am in continuous search mode for more speed trying to satisfy my teenage Grandkids. From following your thread and seeing what your objectives are, I 'd say forget the springs ( that will get you stronger acceleration, like for drag racing ) and change to a smaller drive sprocket. Much more in tune for the kind of driving you are doing.

 

[Rat]

Thank you Bob58o!

that clarifies what I thought about the spring colors, and I had read about the 3 holes to fine tune.
I very much appreciate you answering my questions!

The 7" driven is what I have, lucky me!

I will install the yellow spring and see what happens.

The yellow is a belt stretcher that is stiffer than Red (clone equivalent to Genuine Comet 30 stock green) and Gold is the stiffest.

I'm surprised and annoyed someone didn't already show this

 

[bob58o]

20 series, 30 series, inboard, outboard, Left wound, right wound, reverse wound, torsion springs, compression springs, with tangs, no tangs. Many different springs for different set ups.

Have never seen a gold driven spring on a 30 series. Only Green/Red or the Yellow.

That gold driven spring might be for flipping g a 20 series driven unit around to be be oriented outboard like a 30 series.
Or possibly to flip both units of a 30 series?

The 40 series with a backplate requires the Driven unit to be mounted outboard like a 30 series. That’s why people flip the Driver unit around. The 40 series also has a reverse wound spring as an option to be used with the outboard driven unit.

 

[mouthfulloflake]

its asymetrical 30 series genuine comet on this kart.

I have seen that chart, and it lists 3 driven spring options, but gives ZERO information about them

Rat, when you say belt stretcher, do you mean I shouldnt run the yellow spring?
I will see what the smallest sprocket I can goto on the jack shaft is, but it seems that will be a very sight change

I will also try and find some slightly smaller rear tires/wheels I guess to try and accomplish my goal.

or sell it to someone that rides in a pasture haha

Thanks guys!

 

[bob58o]

A smaller jackshaft sprocket may be the cheapest and easiest solution to your problems and the change won’t be slight.

I don’t know what the sprocket tooth ratio is currently

But for example, 72T of axle and 12 T on jackshaft is 6 :1.

Swapping a 10 T sprocket instead of of the 12T changes 6 :1 to 7.2 :1.

20% increase in torque.

Or if you currently run 60T : 10T, swapping the 10T to an 8T is a 25% increase in torque. A $15 sprocket swap is the first thing I’d try.

 

[bob58o]

The TC jackshafts sprockets I use are 5/8 bore.
I think type “C” style sprockets are what I use.
It possible you might need to shorten the key in the jackshaft to use a sprocket with built in key.

An increase of 20-25% TQ is significant.
Like adding another 100lb feet of torks to a car that already had 500 lb footsies.

 

[Rat]

Rat, when you say belt stretcher, do you mean I shouldnt run the yellow spring?

The Red spring all the China Copies use is equal to the Genuine Comet Default Green spring. A Yellow is significantly stiffer, by being stiffer it delays the the driven from closing up and lifting the belt as soon which in turn fights against the driver closing on the belt meaning it takes a lot more rpm and power to accomplish. The side effect of this strain is premature belt stretch.

Ultimately you're better off switching to stiffer garters (or clipping a couple coils of the end and reattaching them to themselves) or lighter weights in the driven to delay engagement rpm if that's the goal.
I have a yellow and switched back to the original spring simply because the gains were more insignificant than the damages and wasted power.

My not so Mini bike rig sitting on 2.50-18 motorcycle tires will pull the nose off the ground from a dead stop pretty as you please with a 10t. It does it so easily that it makes me a bit nervous, oddly not so much with the 9t but make no assumption it will still stare at the sky either way if I give it a flick and a goose.

 

[mouthfulloflake]

ok, I am trying to wrap my head around that.

there are weights in the driven pulley?

 

[bob58o]

ok, I am trying to wrap my head around that.

there are weights in the driven pulley?

No “Weights”

Spring.
Helix.
Sheaves

It’s about spring strength and helix ramp angle as the movable sheave moves and buttons slide on helix ramp.

 

[bob58o]

The way I understand it…
The driveR unit goes to a bigger O.D. Pulley.
As this happens, the belt pulls on the sheaves of the driven unit. The spring in the driven unit resists the pull of the belt. The more resistance, the more pull it takes for the driven unit to fully shift (the moveable sheave to open so the belt can ride lower and create a driven pulley with smaller O.D.)

The size of the driven pulley depends on the size of the driver pulley. So it may require simultaneous tuning of driver springs and weights with tuning of driven spring and preload.

Ideally, a variety of helixes with different angles would be nice for tuning purposes.

 

[Rat]

The way I understand it…
The driveR unit goes to a bigger O.D. Pulley.
As this happens, the belt pulls on the sheaves of the driven unit. The spring in the driven unit resists the pull of the belt. The more resistance, the more pull it takes for the driven unit to fully shift (the moveable sheave to open so the belt can ride lower and create a driven pulley with smaller O.D.)

That would be an exactly correct understanding, which is why it is also possible to go to heavy of a resistance in the driven and burn up belts much like being geared too low will do.

7" driven is an option as well, which gives a much better initial launch ratio and unfortunately it is my understanding they don't have as low end ratio

The size of the driven pulley depends on the size of the driver pulley.

not true as stated above, it just happens that 6x6 is the standard default

So it may require simultaneous tuning of driver springs and weights with tuning of driven spring and preload.

no, like proper engine tuning procedure one thing at a time.

Driver:
lighter weights = later engagement (higher rpm needed)

Stiffer garter springs = later engagement (higher rpm needed)

Driven:
Stiffer spring = Slower shifting ( stays at lower rpm longer/ takes more rpm to fully open)

Ideally, a variety of helixes with different angles would be nice for tuning purposes.

That would require either multiple modified driven units.
IN THEORY since the ramps are cast aluminum one could shave off the rivets in the front sheave holding the ramps on, dril and tap for some small button head allens that will effectively mimic the rivets as far as not being sharp and eating it up if you were to get the belt down that far.
I have ripped only one belt to shreds with the rivets by fully opening a driven and pulling the belt all the way down with nowhere else to go. Just barely nipping the rivets with the cogged edge isn't a major problem, it's when the belt is riding deep enough to pass as constant contact that is destructive.

 

[bob58o]

not true as stated above, it just happens that 6x6 is the standard default

I was speaking of a generic variable pulley system.

If belt length is fixed and pulley center to center distance is fixed, you can’t make only one pulley a variable pulley. They both must be variable.
If one pulley gets bigger (larger OD, higher riding belt), the other must get smaller (smaller OD, lower riding belt).

Not speaking about the static sizes, but during the shifting process.

Words always getting in the way of ideas.

 

[bob58o]

So I guess my claim was that in order for the driven unit to open fully, the driver has to close fully.

RPM determines the centrifugal force on the weights that opposes the garter springs.

I guess the spring in the driven unit and the torque load determine the “shape” of the system and the force on the weights only closes the driver unit as much as allowed by the driven unit.

I’m just having a hard time not seeing all the forces in the whole system.

The more compressed the driven spring is, the more stretched the garter springs will be. But I suppose that past a certain engagement rpm, the garter springs are insignificant vs the other forces.

 

[Rat]

I was speaking of a generic variable pulley system.

If belt length is fixed and pulley center to center distance is fixed, you can’t make only one pulley a variable pulley. They both must be variable.
If one pulley gets bigger (larger OD, higher riding belt), the other must get smaller (smaller OD, lower riding belt).

Not speaking about the static sizes, but during the shifting process.

Words always getting in the way of ideas.

Right okay that makes more accurate sense. In the case of a 7" driven swap you just go to a bigger belt

So I guess my claim was that in order for the driven unit to open fully, the driver has to close fully.

Not entirely accurate, but close enough for government work. There are variables that come into play; specifically wear, belt stretch, and proper initial fitment.

RPM determines the centrifugal force on the weights that opposes the garter springs.

Correct.
However it is the physical mass of the weights that determines their sensitivity to said rpm, and the garter springs stiffness controls the allowable amount of responsiveness in both accelerating and decelerating rpms

I guess the spring in the driven unit and the torque load determine the “shape” of the system and the force on the weights only closes the driver unit as much as allowed by the driven unit.

That's pretty much spot on. The driver decides what power of rpm goes out... but the driven decides at what speed that gets sent through the driveline to the wheel

I’m just having a hard time not seeing all the forces in the whole system.

The more compressed the driven spring is, the more stretched the garter springs will be. But I suppose that past a certain engagement rpm, the garter springs are insignificant vs the other forces.

Think of the garter springs as more of a leash, and the weights as more of a big dog trying to chase a squirrel... You can't stop the big fool, but you can keep him somewhat controlled.

I would think too stiff of garter springs would be an issue. Keeping in mind they control the responsiveness of the weights so if you mix and match to an engagement speed of let's say 3600, but your engine doesn't make power over 4k.... that's a dumbass mistake because you'd need to be reved damn near to peak power before it bites. That just comes down to how much power your engine makes, and the rpm it's peaking at though.

I've not had any serious issues with running full default on a TC, most of my issues have come back to other driveline issues after the fact (eg cheap belts, over geared, bad alignment, bad bearings)

I mentioned the yellow driven spring being relatively bad for belts, but there IS a small caveat. If you live in a dominantly flat region where even hills are few... it's that not bad with a good FD ratio for it to throw the power at.

My initial set up in NY was great (10/36) but was promptly a disaster in the mountains with winding roads so I'm now geared for the region (9/54) and have done a little more work to the engine itself.

 

[mouthfulloflake]

Yellow spring arrived today. ( from BMI)

I am pretty sure i have a 10 tooth sprocket on the jackshaft
so I will verify the bore size and see if I can order an 8

it turns out that the tecumpseh OOH60 starts one pull every time
but on bumps it coughing and loosing power, a couple of times in the last few days it failed to idle down and got a bit sketchy

so I have a few things to tackle here, I appreciate all of the knowledge and advice from this forum,

 

[Rat]

but on bumps it coughing and loosing power, a couple of times in the last few days it failed to idle down and got a bit sketchy

You have a plugged jet, plugged idle A/F delivery passage, air leak, or fuel restriction in general... failure to promptly return to idle when off throttle is the #1 dead tell of a lean burn situation l.

As for stumbling on bumps, when paired with the idle issue it points towards a kinked fuel, petcock problem, plugged inlet needle valve, sticking float, or a bad float level setting.