LO206 Clutch Help

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My sone will be running a flat dirt kart NKA Cadet with the LO206 engine black slide and 6150 coil. Any suggestions on clutch? As I see the rules only requirement is a dry clutch...so whats better the drum of the disc and why. And then how many disc and how many springs? Thanks
 
If you are allowed a disc clutch with your club/series, then my suggestion is to run a disc clutch.
They have an advantage in the first 60 feet of acceleration. After that, the clutch should be locked up 1:1 and make no difference except on starts and restarts.
Drum clutches are cheaper and easier to maintain.
Disc clutches require some maintenance to keep at their peak, but perform great when kept up.

FWIW, we sell fresh used Bully clutches set up for your application for $200 with your choice of driver.



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🏁Thanks and God bless,
Brian Carlson
Carlson Racing Engines
Vector Cutz
www.CarlsonMotorsports.com
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31 years of service to the karting industry
Linden, IN
765-339-4407
bcarlson@CarlsonMotorsports.com
 
With respect. My views are 180° opposite of Mr. Carlson.
On the low end, coming off the corner, the clutch is holding the engine at a given RPM, hopefully peak torque RPM, and it's transferring that torque through the chain to the axle. You can calculate the horsepower at the axle. While the clutch is slipping, the horsepower at the engine is different from the horsepower at the axle. While the clutch is slipping, I can calculate the horsepower at the engine, or, I can calculate the horsepower at the axle. They're different. They only become the same when the axle is turning, times the gear ratio, the same RPM as the engine. Do the calculations; torque X RPM / 5252.1 = horsepower. Let's say the engine is turning 3000 RPM, measured in torque, use the formula, and you know how much horsepower the engine is putting out in 3000 RPM. Now measure the horsepower at the axle. If the axle is not turning, you cannot calculate the horsepower. But as soon as it starts turning, the same formula applies. As the axle turns faster and faster, there's an increasing amount of horsepower at the rear wheels.
I've seen it demonstrated that clutches slip a small amount every time the engine fires, even after the clutch "locks up". It's my guess that the disc clutch slips just a little less than the shoe clutch at the moment the engine fires. This means more torque at the rear wheels i.e. more horsepower.
I believe the only difference a clutch can make in the amount of torque transferred to the rear wheels is the amount of heat the clutch produces. Producing heat means a loss of power going to the rear wheels.
If you agree with this, then you can see why I always tell people that they should be slipping the clutch at peak torque RPM. Peak torque to the rear axle means peak "horsepower at the axle"
 
You better check with the race director, I think that's a misprint should read drum clutch, all clutches are dry in the LO206 world. You want the Hillard Flame.
 
Anytime you write a novel and use the word "my guess and I believe" the other 500 words of rambling are null and void.....

If allowed a 2 disc bully would be the clutch to run. If you have to run drum then the Hillard is the answer.
 
Well, he did say "with respect." :)

Al, where do we differ 180* again?


60 foot elapsed times have always been significantly better with a properly set up disc clutch over a properly set up drum clutch (based on my experience with current kart clutches.)

Now, on a rolling start, it gets harder to test consistently. Even on our dyno, we lock the clutch up well below peak torque rpm just so we can get data at peak torque. On an acceleration dyno, you can see clutch engagement and record data, if just for a second. What you typically see is the rpm drop as the clutch locks up, then it will climb some more and drop again. It may do this several times before settling in. You really see what breaking a clutch in does as well. If you see too much chatter, then the clutch is set up too aggressive, ie too much air gap, leading shoes, etc. and can be accommodated for with correcting adjustments.
On the track, a clutch (shoe, disc, or otherwise) should be set to engage at peak torque.

I don't always agree with your terminology, "slip the clutch," as it tends to be a bit dated and 2 cycle-ese, but I do remember describing a bad carburetor mixture on the 2 cycles as "4-cycling" though :)

Can't say that I disagree with anything you wrote above, unless I'm missing something, which certainly could be the case.
 
Mid-70s, I was racing the MC101. Coming out of this one turn, with the clutch slipping, I noticed that a few yards out of the corner the clutch would lockup, the RPM would drop, and I would continue accelerating down the track. I started messing with the carburetor. Each time, coming out of that same corner, I would open the low-speed needle a little. Each time I did that, the clutch would lock up a little later and the RPM would drop a little less. After three or four times, I got rid of that RPM drop when the clutch locked up. It was just a smooth transition from slipping to not slipping. All of this was done with a oil bath shoe clutch, Burco if I remember right. In those days, we use to invert the second heat. I won the first heat, so I started last in the second heat. About 12 karts as I remember. I had an incident at the end of the first straight and spun, but I still won the second heat.
Disc clutches don't seem to have that same problem. They engage in a pretty straight line, regardless of the amount of horsepower at the clutch. I'm not sure if I am explaining that right. When I first used a disk clutch (1977 Nationals) I found that I was not necessarily faster out of the corners, but there was a big improvement on the top end. I had troubles with that clutch that couldn't be repaired so I didn't run the class.
 
I'm in agreement with you. Al. Question though...wasn't the slippage, or power wasted, with the drum clutch on top end that was the reason that your disc clutch felt better on top? (ie the disc clutch wasn't wasting/slipping away power (as badly) when it should be locked up 1:1?) That would be a design advantage rather than simply a set-up issue.

Gil's disc clutch design, Kermit's, Tim's, etal, have a propensity for engaging very hard and pulling our limited power engines down when they are set up to "hit" engage hard. The oval racers love this "hit" when the clutch engages because it launches the kart forward. Other designs (SMC is a good example) offer a much smoother engagement that is more like a torque converter in "feel," but for the most part oval racers haven't embraced that clutch for that reason.

Interestingly:
From my limited understanding, electronic transmissions in modern cars are designed to have that hydrostatic drive feel, but the average driver/consumer would be disappointed without feeling that transmission shift hard, so the program is written to give the driver more shift point "feel." Or at least that was the way it was explained to me by someone who knows a lot more about it than I ever will. :)
 
So many questions! I wish I had your ability to express myself in writing. I'm going to work on it, I think I understood all your questions, I'll need time, talk to you later.
 
Al,

It doesn't matter if it's a disc clutch, shoe clutch, or anything else. ANY clutch that is actuated centrifugally can have its engagement characteristics altered (for better or for worse), by a combination of the following:

- The ratio of spring force to shoe mass (assuming the clutch has spring(s) of some sort)

- Type of oil

- The relationship between the static and dynamic friction of the friction surface(s)

- The geometry of the actuation system -- weights, fingers, whatever you want to call them in a disc clutch. ("Air-gap" is part of the geometry)


It is considerably easier to alter engagement characteristics on a disc clutch because the actuation method has more items that can be "tuned". A disc clutch with any "range of adjustment" can easily be set up to "drop in hard", or engage so smoothly it's almost impossible to feel (and anything in between).

PM


alvin l nunley said:
Mid-70s, I was racing the MC101. Coming out of this one turn, with the clutch slipping, I noticed that a few yards out of the corner the clutch would lockup, the RPM would drop, and I would continue accelerating down the track. I started messing with the carburetor. Each time, coming out of that same corner, I would open the low-speed needle a little. Each time I did that, the clutch would lock up a little later and the RPM would drop a little less. After three or four times, I got rid of that RPM drop when the clutch locked up. It was just a smooth transition from slipping to not slipping. All of this was done with a oil bath shoe clutch, Burco if I remember right. In those days, we use to invert the second heat. I won the first heat, so I started last in the second heat. About 12 karts as I remember. I had an incident at the end of the first straight and spun, but I still won the second heat.
Disc clutches don't seem to have that same problem. They engage in a pretty straight line, regardless of the amount of horsepower at the clutch. I'm not sure if I am explaining that right. When I first used a disk clutch (1977 Nationals) I found that I was not necessarily faster out of the corners, but there was a big improvement on the top end. I had troubles with that clutch that couldn't be repaired so I didn't run the class.
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