Manual Clutch for Horizontal Shaft Motor

[John Matthews]

entropy is encroaching

must be off season
_________________
John Matthews
Heartbeat Power, LLC.

[Russell Stevens]

Back on topic, That's a cool manual clutch. Good work guys!

(Is that a little better?)

[Brian Degulis]

Yes the clutch stays engaged above stall speed wether the engine is pushing the kart or the kart is pushing the engine. What I think your over looking is that you will drop below stall speed on some turns. Second being at or above stall speed doesn't mean your fully engaged there is slip. With you foot on the brake of your TAG kart run the RPM up and you will see that the engine comes up above stall speed by normally 800-1000 RPM. If it were positive engament like a maual clutch the engine would have to stop because the kart isn't moving but it doesn't. So I think for this to work you'd have to replicate the slip in a centrifigul clutch with a manual clutch then try to adjust it to something better and I don't think you could do it.


Brian

[Danny Downs]

From one egghead to another, a centrifugal clutch has a driver and a driven element. The driver is coupled to the crankshaft at all times, and this is the rotating element that has the springs and weighted shoes attached to it. The Driven is the outer drum that has the sprocket. At the stall speed, the driver and driven are coupled together allowing the crankshaft to deliver power to the sprocket. If the engine RPM ever drops below this stall speed range, it will decouple from the driven element, no matter how fast the Kart is moving. You could be moving at 100 MPH but as soon as your engine rpm drops below that stall speed range, it will decouple from the driven every time. The clutch shoes on the driver element will not have enough rotational speed to displace outward and make contact with the driven, and even if the driver and driven were rotating at 20k, intertia does not allow these to stay rotating together. As soon as that Rpm drops, it's decoupled. Some clutches are self-energizing and allow themselves to form a wedge effect to bite even harder, but even these clutches will disengage below the stall speed.

Also Brian, you are right. That slip that your talking about that we need is possible...you just have to feather the clutch. The more practice the better you get with it.

[Russell Stevens]

Check with the Microd and dirt roundy round guys for sure. did you post this to 4cycle karting dot com?

[Brian Degulis]

[Kyle Geddes]

WANT. Seriously - who do I give my money too?

[Justin Martin]

How much slip does this clutch actually have?

I ask because I am working on different ways to feather an electric generator during braking.

I intend to eventually use a hydraulic clutch, but in the mean time this would be interesting or testing purposes.

The biggest thing is how well it does at feathering, I need quite a bit of feel as it will be used similarly to a brake.

[Steve O'Hara]

Just a few observations...

Top Fuel dragsters and Funny cars are single speed drives and they use a centrifugal clutch for the simple reason that the driver can't control the clutch engagement with the same degree of accuracy as the engineer can tune the centrifugal clutch. For standing starts it is no contest, a properly engineered centrifugal clutch wins hands down. Same applies to single speed karts where it is desireable to keep the engine in the meat of the power band... the driver could never consistently control the slip needed to get maximum acceleration out of the corners like a DXL or L&T clutch.
For a karting application the only place a hand or foot controlled clutch offers any advantage is for the guys who like direct drive but don't want to have to push start the kart. The TAG motors all have clutches that lock up at a very low rpm so that they remain locked all of the time while the kart is driven at speed so there would be no advantage to the hand controlled clutch unless it was used in a situation where the kart is geared so tall that the engine speed drops way out of the power band in the slowest corners. If that condition exists and the driver wants to slip the clutch to keep it in the meat of the power band he would be far better off with a typical wet disk centrifugal clutch like the L&T or the DXL.... it's a moot point... TAG karts are all spec engine packages and no changes are allowed.
I like the idea for the direct drive karts and would not mount the clutch on the engine, I would mount it on a jackshaft so there is no big flywheel hanging on the end of the crank. Anyone who has experience with direct drive kart engines knows that the key to their high over rev performance is the minimal weight added to the crank.
Direct drive racing is fantastic but for the logistics of starting and forming up an organized grid.... this clutch would allow the direct drive karts to be started with a plug in starter, warmed up and then the grid can be released from the pit lane in an orderly manner and the field doesn't have to try to form up at the high speeds needed to keep direct drive karts running... the drivers could disengage the clutch to rev the motors while forming the grid if the speed gets too low.
Nice to see someone working on something new for a change... think how different karting might be if someone had worked on a solution like this 30 years ago.... Oh, wait, someone did and it never caught on.
Seems like it was Hegar that built a very similar system in the 60s but I recall it being a pretty big clumsy package. Anyone remember any details on the Hegar unit???
Steve O'Hara

[Danny Downs]

Well you're close, but not fully correct. Top full drag racing is one of the only forms of drag racing that uses a clutch that is not completely controlled by the driver. Drag bikes, pro stock, bracket racing, etc. all use a standard type manual clutch or an automatic transmission equipped with a trans brake and a high stall converter. You're right about one thing in that a top fuel car puts out way too much horsepower for a human to modulate clutch control such that they can complete launches with consistency. You're also right that top fuel clutches have a centrifugal component that is applying a clamping force on the clutch. The key part that you are missing is that the dynamics of engagement (how much slip, rate of slip, duration, etc) are completely and precisely tuneable depending on track conditions whereas a standard centrifugal clutch does not have this. This is usually achieved by way of a secondary diaphragm spring to adjust the clamping engagement pressure of the clutch. This secondary diaphragm spring is actuated via a precisely controlled pneumatic signal that is tuned by the team’s engineer. In a standard centrifugal clutch, you can tune engagement speed based on the characteristics of the fly weights but it's impossible to tune the engagement dynamics. The engagement dynamics are entirely dependent on the friction material selected, the mass of the fly weights, and the geometry of the levers. Merely changing the engagement speed will have an effect on the engagement dynamics which is uncontrolled by the user. Top fuel drag clutches are probably the most technologically complex system in the entire car- they need to be in order to put down the right amount of torque to the wheels that is just shy of wheel spin.
In drag racing vehicles with lower power 50-3000hp, a manual disc style clutch is almost always used. This is because the engagement dynamics do not have to be as precise in order to get decent/consistent launches. When the driver is staging, he will usually rev the engine to a certain level above where max torque RPM. And then when he gets the green light, he quickly but smoothly presses the accelerator while simultaneously slipping the clutch to generate the right amount wheel torque just shy of wheel spin. The revs at this point will have lowered to at or near where maximum torque RPM.
Clutch control in drag racing is the most important aspect of drag racing. With a skilled rider or driver, our manual clutch will outperform any centrifugal clutch in a drag racing situation. This is because the user will be able to effectively and precisely modulate clutch slippage to the point just prior to wheel spin occurring. It doesn’t matter what type of standard centrifugal clutch you’re referring to on the market, you simply will not have the same launch control that our clutch will give. As a result, we have been getting an overwhelming response from mini bike drag racers that recognize the advantage of this clutch for their application.
Of course this is all just theory and engineering until it is proven on the track!

[Danny Downs]

BTW our rotating mass is only 2.9 pounds, same as a standard centrifugal clutch.

[Steve O'Hara]

I'm afraid you just exposed your complete lack of familiarity with the state of the art kart racing clutches. Anyone with karting experience dating back prior to the advent of the TAG and Shifter era knows that the kart clutches can be manipulated to produce just about any engagement characteristic desired by the tuner. By using different combinations of spring, weight, air gap and oil the experienced tuner can produce effects that range all the way from a straight pedal drop to a CVT effect.
Your comments about the drag racing vehicles are mostly correct but you obviously have not raced a modern sprint kart otherwise you would know that asking the driver to attempt to modulate the clutch slip with a pedal or hand activated device through each slow corner while dealing with the rigors of guiding the chassis around the corners at close to 2G lateral load is not going to work out well. I've seen your demo burnouts and spinning around in the grass... looks like fun but not competative kart racing.
Here's your challenge... get yourself a simple Yamaha KT100 powered sprint kart and develop your clutch until you think it is perfect and then we'll have a simple test... a head to head race for ten laps from a standing start and to make it interesting we'll put some money on the outcome. I'll use a store bought Horstman DXL or L&T just the way they sell them.
BTW, it is only fair that I advise you that I have a bit of experience in this field. In the early 90s I was racing in the Toyota Atlantic Pro Series, one of the most sophisticated and competative open wheel racing series on the planet. We were the only class of racing in the United States that used Formula 1 style standing starts so learning to execute perfect standing starts was paramount to success in the races. After two years of seeing how difficult it was for even the best drivers to consistently execute perfect starts I spent some time with my old mentor Tony Maglizzi of L&T clutches and set about designing and building a centrifugal disk clutch for the Atlantic car. Over the course of the 92/93 winter development I developed the clutch to the point where it was ready to race. At the midway point of the 1993 season I was the series points leader standing ahead of some familar names like Jacques Villenuev, Patrick Carpentier, Mark Dismore, David Empringham, Claude Borbonnais, Colin Trueman etc.
But for the unfortunate decision by the series promotors to abandon the standing starts for reasons related to television broadcasting my clutch design may have revolutionized the sport once I let people know what I was doing.
I've been down this road... you are a bright fellow but you have much to learn about the practical vs theoretical on this subject.
Let me know when you are ready to race.
Steve O'Hara

[Barry Hastings]

The year Scott Speed won just about everything in SKUSA at 103rd one of my friends said it looked like Scott was going to the clutch coming off turn 2. Didnt see it myself, but possible.

interesting theories. LOVE the L&T clutch for the 4 cycle with the flathead engines. REALLY loved the clutches when I had the L&T friction material put on SMC disks. They were great. BUT the higher torque Animal engines the clutch operates past where it is happy. Been looking for a replacement ever sense.

[Danny Downs]

Steve I appreciate the responses and it's always nice to have a veteran of the sport weigh in and give us some feedback. You're right that it's all just theory at this point, but we'll be sure to check in as we make progress and continue to develop the product. It might not have it's niche in racing, but it is a cool unit for anyone who is interested in go karting that wants to try something different.

-D

[Greg Wright]