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Thread: Clutch Stall

  1. #1
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    Clutch Stall

    What rpm do you set the clutch stall on a Sr. LO206?

    I've got a black spring in my Max-O-torque that's supposed to engage at 2900 is that about right?

    I'm also getting a Hillard Fury, got any set up advise?

    Thanks,
    Sundog

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    All clutches, every make and model, should hold all engines, every make and model, at peak torque. (Stall) With peak torque going to the axle, you have maximum horsepower at the rear axle. With maximum horsepower at the rear axle, you have maximum acceleration.
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    Most have the engagement slightly higher than that 32-3500.

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    Quote Originally Posted by Kart43 View Post
    Most have the engagement slightly higher than that 32-3500.
    I think, if you could measure the time you spend at any given RPM, you would find that the engine is at its stall RPM the greatest length of time. At least in that time between when you first get on it and the clutch drum RPM catches up to the engine rpm i.e. lockup. If this is true, why would you want less torque going to the rear axle during that period?? The more torque at the axle, the more horsepower at the axle. While the clutch is slipping, the horsepower at the engine and the horsepower at the axle are different. Look at the formula. Torque X RPM / 5252.1 = HP. The more torque you have at the rear axle, the more horsepower you have "at" the rear axle i.e. rear wheels.

    So if "most" are slipping their clutch above peak torque, "most" are not going as fast as they could. And that is an absolute incontrovertible fact.

    There's more noise, that's true, but noise is just a waste of horsepower, not a maker of horsepower. You don't think that noise gets generated for free do you. More heat coming off the clutch too, and it takes horsepower to generate heat, generated heat is a loss of horsepower to the rear axle.
    From the desk of Al Nunley 512-630-6215
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    Clutch stall speed not withstanding , if the clutch is slipping it is not delivering the full available torque. Then we would need to know how much is lost in order to know how much is being transferred. Is the transferred amount going to be any different , at different rpms if the amount of torque applied is greater than what the clutch can transfer ?
    Engagement RPM and stall RPM are not the same thing though the terms seem to be used interchangably. Causing some confusion as too what is going on.

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    Damn, Al. Yeah, in a Senior class, without a restricted carb, 206 motor will make peak torque around 3500 RPM, So your 2900 is a bit low on engagement RPM. Bump it up, you'll like the performance results.
    Last edited by Gonzari; 04-21-2017 at 09:23 AM.

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    Quote Originally Posted by alvin l nunley View Post
    I think, if you could measure the time you spend at any given RPM, you would find that the engine is at its stall RPM the greatest length of time. At least in that time between when you first get on it and the clutch drum RPM catches up to the engine rpm i.e. lockup. If this is true, why would you want less torque going to the rear axle during that period?? The more torque at the axle, the more horsepower at the axle. While the clutch is slipping, the horsepower at the engine and the horsepower at the axle are different. Look at the formula. Torque X RPM / 5252.1 = HP. The more torque you have at the rear axle, the more horsepower you have "at" the rear axle i.e. rear wheels.

    So if "most" are slipping their clutch above peak torque, "most" are not going as fast as they could. And that is an absolute incontrovertible fact.

    There's more noise, that's true, but noise is just a waste of horsepower, not a maker of horsepower. You don't think that noise gets generated for free do you. More heat coming off the clutch too, and it takes horsepower to generate heat, generated heat is a loss of horsepower to the rear axle.
    Question:

    Where is peak torque on a Sr. LO206?


    Let me add that peak torque can be moved slightly with some simple carb tuning and ignition timing variances on these engines. Keep in mind your saying: "Tuning is not easy."
    ie, one size does not fit all.
    Throw in that some sprint track configurations require the clutch to slip (more or less) in certain corners for better lap times.
    On your Fury, alternating black and white springs works well and will get you close. Don't be afraid to tune a bit from there.

    I think that kart43 has a pretty good handle on where the peak torque is, and subsequently where the clutch should come in.



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    Quote Originally Posted by flattop1 View Post
    Clutch stall speed not withstanding , if the clutch is slipping it is not delivering the full available torque. Then we would need to know how much is lost in order to know how much is being transferred. Is the transferred amount going to be any different , at different rpms if the amount of torque applied is greater than what the clutch can transfer ?
    Engagement RPM and stall RPM are not the same thing though the terms seem to be used interchangably. Causing some confusion as too what is going on.
    With no actual scientific test results to prove it, just logic, and a lot of track testing, the clutch holds the engine, while slipping, because it is absorbing all the torque the engine is producing. You don't need any testing to figure that out. The clutch transfers nothing, the chain transfers the torque to the rear axle. When the clutch is holding the engine at peak torque, although it doesn't transfer exactly the same torque as the engine is producing (it takes horsepower to generate heat) all clutches, unless one is producing a lot more (or a lot less) heat, do exactly the same thing. The exact same amount of torque goes to the rear axle. If the clutch is holding the engine at "peak torque", peak torque (that which is not lost to heat) is transferred to the axle. As the axle spins faster and faster during acceleration, the calculated (horsepower is a calculation) horsepower increases. As long as the clutch is slipping, the horsepower at the engine and the horsepower at the axle are different.

    Have you ever noticed, pulling out of the pits, with the accelerator floored, how the faster you go, the faster the kart seems to accelerate? Well that's the reason, the horsepower at the axle is increasing as the engine and the axle, divided by the gear ratio, get closer to the same rpm.
    From the desk of Al Nunley 512-630-6215
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    I knew I should have stayed out of this conversation.
    (The clutch transfers nothing) Really then explain how the torque gets to the chain.

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    Quote Originally Posted by Kart43 View Post
    Most have the engagement slightly higher than that 32-3500.
    I am sure the OP knows whats going on.
    I would use this info.

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    Quote Originally Posted by flattop1 View Post
    I knew I should have stayed out of this conversation.
    (The clutch transfers nothing) Really then explain how the torque gets to the chain.
    A minor point having to do with semantics. Don't get your undies bunched up! Ha ha
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    Al I think you are comparing these clutches to the wet clutches used on 2 strokes. We cannot afford the slip you refer to the line between go and no go is slim on these dry steel to steel clutches. Stall is a term used in fluid drive such as torque converters, or wet clutches. The device is in stall when one of two action must occur, the vehicle moves or the engine RPM drop. In the case of these clutches it is lock up you want anything between lock up and free running is generating heat and damage. Heat is lost energy.

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    Quote Originally Posted by Kart43 View Post
    Al I think you are comparing these clutches to the wet clutches used on 2 strokes. We cannot afford the slip you refer to the line between go and no go is slim on these dry steel to steel clutches. Stall is a term used in fluid drive such as torque converters, or wet clutches. The device is in stall when one of two action must occur, the vehicle moves or the engine RPM drop. In the case of these clutches it is lock up you want anything between lock up and free running is generating heat and damage. Heat is lost energy.
    No I'M not!!
    From the desk of Al Nunley 512-630-6215
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    People, just use your "ignore list" and you'll have a much better experience on Bob's.

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    Quote Originally Posted by sundog View Post
    People, just use your "ignore list" and you'll have a much better experience on Bob's.
    Your kind of hateful aren't you! Bury your head in the sand, that sounds like a good idea! If your real careful, you won't hear anything you consider bad, and if your real careful, but you gotta be real real careful, you won't hear anything at all. LOL
    From the desk of Al Nunley 512-630-6215
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    Quote Originally Posted by alvin l nunley View Post
    Your kind of hateful aren't you! Bury your head in the sand, that sounds like a good idea! If your real careful, you won't hear anything you consider bad, and if your real careful, but you gotta be real real careful, you won't hear anything at all. LOL
    There's the pot calling the kettle black.

    You should read your own posts.

    If you want the respect you feel you deserve, limit your posts to where you have real experience.

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    I'm with Kart 43.
    IMHO
    About the only time you are slipping the clutch on a LO 206 is when you are leaving the starting grid. I know of very few tracks where you slow down enough to disengage the clutch during a race.
    For the most part it's either locked up or not. There is a very narrow rpm window between starting to engage and fully locked.

  18. #18
    I've been around this sport for.50 + years . I understand what Al is saying .It's my opinion if one reads and thinks the issues out he post about your going to learn something . Next I don't understand the animosity toward his ideas and post .For what it's worth Al has likley forgot more about this sport then many of the so called experts of today think they know . Only my thoughts here .No posts or comments unless you wish to validate my point .Just saying .

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    Everybody knows the theories he's spammed every thread on here for years, don't need to hear it again for the millionth time then, the issuing arguments because he has no specific information about the question. Same thing over and over ad nauseam. So, I get my questions answered without his rhetoric by using the ignore list. Pretty cool actually.

    Sundog

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    Every month, maybe every week, or even every day, someone new comes to this board with questions. Maybe those questions have been asked many times before, and maybe you get tired of hearing the answer over and over again, but the person asking the question, for them, it's the first time they've heard the answer. The fact that someone will go to the trouble to answer that question over and over again, I think, is a benefit, rather than a detriment, of this board.

    There are discussions on this board to which I can add nothing, and/or, I have no interest in, so I just ignore them. Seems like a simple thing to me! No matter how erroneous I might think an answer is, I'm not going to bury my head in the sand. Can you imagine burying your head in the sand and then bragging about it??

    If I see an answer that I think is erroneous, I debate, I put forth other ideas to counter what I think is incorrect information. Now I'm not saying that I'm always right, that's not possible, but I think I am, and I'm willing to put forth those ideas. Isn't that the whole purpose of this board? It is, after all, just bench racing, doesn't everybody love bench racing?
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    Just a quick question on all of this but doesn't the type of clutch make a big impact on this?
    Take, for example, a Hilliard Flame clutch which has 4 contact shoes that have a substantial amount of free contact space not being used towards the drum.
    Then, take for example a Noram 2 shoe clutch that contacts the majority (or at least more) of the drum than the Flame.
    If you have more contact area to the clutch drum aren't you getting more usable power out of the motor?

    So yes, you can find that peak torque of a motor, but if you run a clutch that doesn't transfer all of that usable power, you're basically losing power at that point. Correct? No? I'm curious.

  22. #22
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    If the clutch will hold the engine at peak torque, it makes no difference how it does that, just that it does do it. If the shoes are making more contact, you might need stronger springs to get the engine up to peak torque, but the results will be the same. The only difference in the power transferred to the rear axle is the heat generated. Generating heat takes (uses up) horsepower, so the clutch that gets the hottest will be transferring less power to the rear wheels.

    Another minor point; if there is a spring holding the shoes from contacting the drum, just the act of swinging the shoes out against the drum uses up horsepower. Nothing gets done for free.

    It's like the waves in the wake behind a boat, those waves represent horsepower being used up. It's a perfect visual representation of horsepower.
    Quote Originally Posted by Mac_49 View Post
    Just a quick question on all of this but doesn't the type of clutch make a big impact on this?
    Take, for example, a Hilliard Flame clutch which has 4 contact shoes that have a substantial amount of free contact space not being used towards the drum.
    Then, take for example a Noram 2 shoe clutch that contacts the majority (or at least more) of the drum than the Flame.
    If you have more contact area to the clutch drum aren't you getting more usable power out of the motor?

    So yes, you can find that peak torque of a motor, but if you run a clutch that doesn't transfer all of that usable power, you're basically losing power at that point. Correct? No? I'm curious.
    From the desk of Al Nunley 512-630-6215
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    Quote Originally Posted by alvin l nunley View Post
    If the clutch will hold the engine at peak torque...
    That actually brings up another question...has anyone done a load bearing test with different clutches by chance? Can a Flame hold the same motor torque at a certain rpm than a Noram? Will one hold better than the other at certain rpms? I'm just using those two for an example but consider any drum clutch to compare.
    Granted, I understand that heat transfer plays a role in this, but just for now cut that out for reference.
    So for example, if at 3,000rpms...what if test clutch #1 can only hold and maintain 'X' amount of force while test clutch #2 can hold and maintain 'XX' amount. At that point wouldn't you want the clutch that can produce the best deliverable power at your motors desired max level of power?
    Last edited by Mac_49; 04-24-2017 at 01:31 PM.

  24. #24
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    If the clutch can absorb all the torque the engine is making, at a particular RPM, no other clutch can do better than that, unless it can do it and produce less heat. "Period" Now one or the other of the clutchs might hold up better, as in not breaking as soon, or as often, but as long as they're doing the job, that's all they can do.

    Now there is the possibility that, installing the clutch on a bigger engine, one might be more able to hold the load than the other, but that's a different story.

    Answer me this, if both clutches are holding the engine at peak torque, and are not breaking, and are not producing more or less heat, what difference does it make if one can hold more load in some other application?
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    Quote Originally Posted by alvin l nunley View Post
    Answer me this, if both clutches are holding the engine at peak torque, and are not breaking, and are not producing more or less heat, what difference does it make if one can hold more load in some other application?
    If they can both hold and maintain exactly the same then ya, it makes no difference. You're totally correct. But CAN all clutches do that across the board or are there better benefit rpms specifically for each clutch?

    Here's an idea I have behind it:
    Say you're opening a can of pickles and it requires 'X' amount of force to do it.
    If you use your hands you HAVE the ability to create 'X' amount of force, but you're just slipping.
    So you then grab a cloth or something which doesn't slip and use the same 'X' amount of force to open it.

    Same with clutches...every clutch has the ABILITY to hold and maintain the max power delivered from the motor, but based on material, design, layout etc...I would imagine that some would have a better holding force at different rpms.
    So for a LO206 engaging at it's peak takeoff power, would there be a clutch that is better than others because it can catch, contain, and deliver the max power?
    I'm no expert on this Al, so I understand I could be totally off, and if so I'd love to hear your thinking behind all of this.

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    Any clutch that engages and does not slip at your desired RPM is adequate to deliver the engines torque. You should not lose energy to heat if your clutch is locked up, you loose it if your clutch is slipping. You are asking is there a clutch that locks up at my desired RPM the answer is yes many. Your pickle example is a slipping clutch, and there are many of those usually just poorly set up or maintained.

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    Quote Originally Posted by Kart43 View Post
    Any clutch that engages and does not slip at your desired RPM is adequate to deliver the engines torque. You should not lose energy to heat if your clutch is locked up, you loose it if your clutch is slipping. You are asking is there a clutch that locks up at my desired RPM the answer is yes many. Your pickle example is a slipping clutch, and there are many of those usually just poorly set up or maintained.
    Right, so you're saying kind of in a way that I was in the fact that clutches have the ABILITY to hold all the power thrown at them, but if one design will slip at that desired power range (due to design) then obviously you wouldn't want to use that clutch if it can't hold on to the power that's being thrown at it.

    I'm just curious if anyone has tried this kind of testing to say one way or the other.
    If you set up 10 clutches to engage at the same rpm and test them on one motor where the power is constant...will all 10 of them deliver the same power output (at engagement) or will some be slipping where others aren't?

    It would be a pretty neat thing if you could tell someone "For the 206, at 3,000rpms, based on testing, "XYZ Brand" clutch was able to deliver the most power that the motor has to offer upon engagement." Could be the difference during launch on getting ahead where the other brand clutches would slip for a little bit.

  28. #28
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    Quote Originally Posted by Mac_49 View Post
    I'm just curious if anyone has tried this kind of testing to say one way or the other.
    If you set up 10 clutches to engage at the same rpm and test them on one motor where the power is constant...will all 10 of them deliver the same power output (at engagement) or will some be slipping where others aren't?
    It depends on your definition of, or your use of, the term "engagement".

    I call engagement that period of time when the axle rpm, multiplied by the gear ratio, is less than the engine rpm. In other words, while the clutch is slipping. When the engine rpm and the axle rpm, divided by the gear ratio, are the same, I call that lockup.

    Although I've never seen it scientifically tested or proven, I have this idea that all clutches slip a small amount even after lockup. It would be easy to prove with very precise and accurate tachometers on the engine and the axle. They wouldn't be slipping all the time necessarily, just that short moment when the engine first fires, or very soon after.I speculate that after lockup, some clutches do slip more than others. Pete Muller has shown us with his math that the heavier the shoes and the stronger the spring the more force is exerted as the rpm increases. Centrifugal force that is exerted by the shoe is a square function of the weight of the shoe times the rpm it is spinning. Like I've said before, using Pete Muller's math, heavier shoes, with stronger springs (so they still slip the same as lighter shoes with less strong springs) exert more force at higher RPMs. More force, less slip.

    All of this was discovered in the late 70s when we first started putting springs on our centrifugal clutches. Starting in 1977, the Horstman disc clutch pretty much made the no spring centrifugal clutch obsolete for two cycles.

    Either they are all slipping at the same rpm or they're not, you can't have it both ways.
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    Quote Originally Posted by alvin l nunley View Post
    When the engine rpm and the axle rpm, divided by the gear ratio, are the same, I call that lockup.

    Either they are all slipping at the same rpm or they're not, you can't have it both ways.
    I think based on this, it'd be a really cool experiment or science project. Seeing if some do slip a little more than others and by how much. I wish I had everything to do it but unfortunately Denver costs a little to much to have a lot of toys haha.

    I know it'd be a tough test to run with all the different motor classes, either 4 or 2 stroke (and say "This clutch performed the best with this engine class" but maybe sometime someone will be able to shed some light on a test they were able to run.

    Thanks for the input Al!

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    Clutch dyno.
    Plenty around .
    Someone knows.
    The premis (of the clutch holds it at peak torque)
    Has merit although it does not address the lost amount to slippage.

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