Clutch Info Please

[BREEZE]

I am looking for info on what demise to your clutch has happend causing you to have to replace or repair a fairly new one,,,say hp input,for the first bit of info,,as to a 35 HP or better installation,,,can you give me your thoughts on this? Thanks Breeze

[mudNmallards]

My personal experiences with centrifugal clutches mainly comes from racing go karts back in the day and chain saws but I have a pretty good amount on industrial clutches mainly used in the lumber industry (chippers, hog knives, debarkers etc) and on portable equipment at remote sites.

I’m mainly here to listen to comments, look at drawings and see people’s usage of these machines to help me decide on what my initial purchase of an AATV will be based on performance, reliability, capability and chronic problems. I may wind up in a year or so being in a group that will be designing a new type AATV depending on the results of marketability studies that are going on. ( so I have a dual vested interest so to speak)
As I search threads here I see numerous repetitive comments and failures specifically regarding bearings, chains, seals, transmissions, clutches and a few others. I pay real close attention to those.

If it please the board, I’m going to throw some clutch information out there I have gathered through the years to resolve chronic failures on heavy equipment. I’m sure most probably know all this but maybe a few do not and can use it to maybe put some chronic issues to bed. It may be possible to adapt this information and mitigate any problems or performance issues you may be encountering.

Its difficult for me to get too specific because most items I find do not have a manufacturers part #( which is not an OEM part #) for me to reference so I cannot get the exact technical engineering and application data but in general terms based on drawings and posted pictures I think I’m in the ballpark.

The selection process
Contrary to popular belief, the average OEM does NOT manufacture most component parts for their devices. They give their data to the component manufacturer and they either spec out a recommendation or design one for a specific application. There is a problem with that.( I have been involved with this more times than I can count and have suffered greatly for it) The widget manufacturer gives his recommendation based on the data the OEM gives and then the PRICE. A lot of times this sends the OEM into a coronary. They then come back and say “can you give me something that will “work” for 90 days or maybe 1 yr. ( whatever the warranty period is) This is why in many cases a component manufacturer will NOT put their company information on the part or list certain applications in their parts catalog. ( they do not want their name or product associated with certain things because of failure) A bad decision on the part of an OEM ( who is looking at pricepoint) is no reflection on the component when it is probably not the proper application for the product. Some OEM’s will call this a “trade secret” because they do not want you to know it either. (for obvious reasons and they might wind up in a class action suit)
I put that in this post because from what I’m looking at in pictures and hearing the size engines ( and load from the vehicle and drivetrain)- I would be willing to bet that a majority of the clutches are the improper size for the application. If that’s actually the case as I suspect, no amount of maintenance or direct replacement will restore the lost efficiency, stop the downstream wear on the drivetrain or maximize the life and potential of the machine.

Centrifugal clutches in general (without specifics, I have to be an average gross so take the following as an approximate range- not absolutes)

Most spring clutches ( what are usually called go kart or lawn mower clutches) are not designed to operate outside the torque of about 12-15 hp so anything beyond that is already damaging the clutch and greatly reducing its torque transfer efficiency. ( the suppliers I normally use tell me after 15, you have to go industrial grade, not consumer grade because of the service factor of the clutch) Remember, there are 2 kinds of torque also- the input torque ( what the driver gives you) and the output torque ( the load the drivetrain requires to turn plus any backlash from component clearance as well as tractive forces and any “shock loads”) If the clutch is not sized to the OUTPUT torque then the reverse torque forces will usually beat it to death.

Most spring clutches are not designed to be a true torque converter ( like a fluid coupling) so they have a design ratio that defines their upper limit of transferable torque. This is derived by dividing the driven into the driver. For speed applications this is about 6-10:1 and low end torque its about 14:1. ( there are some other variables that can affect that as well such as weight, motive traction, drivetrain slip and a few others)

The break-away torque- most manufacturers have an absolute ceiling a clutch will cease to be effective at. The generic formula for this is: T(usually in in/ lbs) = HP*63025/RPM * SF. Usually a clutch loses up to 50+% of its efficiency when this is exceeded.
So, regarding clutch failures, the 3 items above are the most common reasons equipment experiences premature clutch failure and the most common root cause is the improper clutch for the application.

OEM’s often “hide” certain data (mainly the service factor) because they do not want you to know this. See, everything manufactured that has an engineered performance factor has to be baselined to something. ( everything has to have a fixed point of reference otherwise claims have nothing to relate to and become meaningless). These devices are usually baselined against an ELECTRIC motor ( which has fixed torque over its rotational range almost at 100%) not an IC engine which has constant torque gaps due to the cycles. The service factor is normally above 1 ( which means designed for continuous duty). They also design them against the end torque of say a pump or gear drive and almost NEVER compute against intermittent load, shock load or free wheeling.( difference between a good sloping sine wave on a dyno versus a stair step)

The problem is that in vehicular applications (especially when tires or engines have been upgraded) all these things exist in vast amounts whereas in an engine driven generator, air compressor, mixer etc. they generally do not.

I would suggest to anyone who has chronic clutch/drivetrain issues or just feels they are not getting what they think they should from their engine to maybe contact 2 manufacturers I have used and give them your functional parameters and see if the clutch they spec out matches what you are currently running. (I’m normally vendor neutral but these companies have helped me out many times over the years) They are North American Clutch and Comet Industrial.

I believe many may find that installing the proper clutch for the actual parameters of your machine (even though there may need to be some modifications and the cost will be in the 3-400 range) will cover a multitude of “sins” and put many of those “nickel and dime” downrange problems to bed.

[thebuggyman1]

Great write up muddNmallards!
This thread came about because of me....(sorry everybody) and a conversation I had with BREEZE. Largely because of this http://www.6x6world.com/forums/max-a...tml#post114129 and member Toys4Me trashing a new comet 94c on a clone motor in his first time out with it.
The cost on the 94c is around $250, and the other three cost about $400.
I have heard nothing but good things about the comet 1190/1195, powerbloc80, and team aftermarket clutches. So I'm sure Any of them would be a good choice.
Putting that much HP and torque on the 94c kindof scares me, but there is no basis for that fear.....Basicly these things are a big mystery and I'm sure there is no simple explanation.
I also had a conversation with Tim (Obsessed) on friday...more about engagement, and coordination between primary and secondary than durability. Tim really knows his stuff, and I'm still scratching my head. It seems easy enough as a basic theory. The primary must squeeze hard enough to overcome the squeeze in the secondary, but it is really alot more complex than that. I think the problem is that our machines are not operated on flat level ground with a constant rolling resistance. Tim said he has seen secondary clutches not want to return quick enough to down shift properly. I have experienced that myself, trying to get out of a pond with a steep bank. You hit the bank turning the tires fast and have a hard time climbing the steep bank. When the RPM's drop, all because the secondary didn't downshift. You roll back into the pond, idle for a few seconds and it climbs right out. I have not tried the red spring in that machine yet, but I do plan on it. The problem is, it happens intermittently....how would you know for sure it was fixed?

[lewis]

This is why i recommend Quality Drive Systems. (Roy) is the fellows name i deal with, this is his field of business. He is the engineer for this field and runs QDS. You tell him the application RPM, what it's end use is and he comes up with the right numbers. He know what we are doing with these machines and is familiar with their application. Tried several places inquiring about clutches and the only thing most can do is ask the same old questions: What make, model, engine size and when i would say "Attex" the phone would go blank. They have never heard of them so no answers, same thing on the belts. If you tell them what clutch you have they may be able to replace it with like kind, but if you have the wrong clutch you will repeat the process again. Roy was recommended by Whipper and he has worked out great. He is a expert in his field and so far has been spot on.

All statements made by muddNmallards are spot on and thanks for the write up.

[BREEZE]

First of all, I would like to thank MudNmallards for your very informeitive and indepth views of the clutch adaption theroies and applications,,,And I also would like to thank Thebuggyman for making a post related to the clutch problem that he has some knoweledge of,,,,Kutos to both of you! Again both of your inputs is what is making this a great site for all the atv,utv,4,6,8,tracked and soforth,,I also am a design/fabracator with a small shop here where I reside here in SC,,Tho I have had many various challengeing moments with some sort of MFG say not so good of an idea app. This is why I was looking for some input on hands on expertise on the matter. I would rather spend a few more bucks (usually a good bit more) to have a durable made product that will last a good bit longer than haveing to repair a cheaper made type, and that ends up usually costing more in the longrun,,,I am not into saying (Mine is better than yours) or any better Bling than yours.It is very sad these days the way things are made as cheep as cam be made for the MFG to have a bigger profit margin in there favor than to make a ( Buy one that will last a very lomg time ) like in the years back,,,seems to me we all live in a throw away world these days and as for Quality and Workmanship has been replaced wirh the $ greed thing,,,Sorry for me getting away from the orgional point here but ,,,what can I say,,,Again Thank you both for taking the time to respond,,,,Breeze

[thebuggyman1]

Roy at QDS was one of the people I spoke with (thanks Lewis). He is very knowledgeable, and was recommending I go with the powerbloc80 and secondary combo. He is out of stock on the secondaries and wont have them for a month or so....Punt!
Jason at Team aftermarket knew his clutches well, but not the comet secondary, or red spring, or how we use our machines. His advise was to just have enough spring in the secondary to close it and let the primary do all the work. Sorry Jason, but that falls back to the pond thing I mentioned earlier. Tires spin real easy in the water, and not so easy climbing the steep bank. Probably good advise for a go kart though.
Roy did imply that the comet 1190/1195 was being phased out and parts were hard to come by......so I think I'll avoid that one.
I don't mind doing a little R&D myself, but at $400 each....this could get expensive quick.

[mudNmallards]

Thank all of you for the kind comments. I don’t mind giving my experience and expertise because I’m in the position where I have access to data, equipment and information not normally available to the consumer. Also, there will probably come a point in the future (if a prospective project comes online) where I’m going to pick the brains of everyone here because you have the real world “boots on the ground” experience on these machines and their usage in a variety of circumstances that I do not have. I’ll try to put this in layman’s English for those here who are not engineers or experienced technical types so they can benefit as well. There may be a sacrifice of technical literal accuracy for the sake of general understanding but for discussion purposes its accurate in the broad sense.

First, I’m still reading (and digesting) the threads on this board and I see various themes come up and these clutches seem to be a chronic and predominant one. I believe knowledge is one of the main tools in the problem solving process so please allow me to give a little more advanced class on these types of power transmissions because the actual problem ( not the perceptual or anecdotal problem) might be right in front of your face but you may not be recognizing it for what it is so a “fix” eludes you because many times people chase symptoms and just end up “moving” the problem to the next weakest link rather than putting it to bed. See, in industry when you have a million dollar machine that will lose hundreds of thousands of dollars an hour in downtime from failure to repair- people get real upset and pay people like me to find the root problem and fix it as opposed to consumer type systems where they can usually get away with “well John, you know these things just break and that’s how it is so just throw a new one in there and drive on”. People either accept the failure as the norm (and get used to paying for it) or make attempts to fix it which often just involve “beefing up” the immediate failed component giving the ILLUSION of repair but in reality just set the stage for the next weakest link to fail. They never really relate the two and seldom build failure out of the system.

Chances are the true problem and the obvious solution are right there in front of you hiding in plain sight- you just cant see the forest because of all of those darn trees in the way.
I need to start off with a quick class on English. I feel this is necessary because in physics/engineering certain terms have specific definitions and qualifiers that do not exist in conversational usage. This creates many problems because most technical information is written in “engineer-speak” and most marketing/consumer information is written in “conversation-speak” and that creates problems. ( think about the Titanic, the ENGINEERS said it was unlikely to sink ( under the accepted anticipated types of expected damage of the day such as a single torpedo or maybe striking a rock and knocking a single hole in the hull which they incorporated into the design- see the engineers QUALIFIED their statements against benchmarks)- the ADVERTISING people took that statement and “massaged” it into “unsinkable” and we all know the end result of that)

For the purpose of this, the following definitions apply:
Clutch- a device that transfers RPM and torque from a prime mover to a driven device while allowing for slippage for reasons such as starting under reduced load or to dissipate shock loads etc
Transmission- a device that “transmits” RPM and torque through it that inverts the properties relative to the prime mover. (RPM and torque have an inverse relationship similar to voltage/amperage where one goes up, the other goes down. This is in relation to the second law so transmissions [reducers] decrease RPM while increasing torque and other transmissions[ increasers] increase RPM and reduce torque)
CVT (Constant Velocity Transmission)- a type of transmission that uses a variator (device that senses load and adjusts the CVT as needed) to operate within an almost infinite range between the upper and lower ends of the RPM/torque values the system is designed for as opposed to a standard stepped transmissions that have built in specific ranges ( high/low range, 1st,2nd gear and so on)
Motion (in this conversation- when the wheels start moving the vehicle) - the “event” (or moment) where available torque from the prime mover overcomes all voids ( chain backlash, belts gripping in pulleys and transferring load, etc) closing them and then torque transfers from the prime mover (like water in a pipe) from the driver PTO to the output device (the tire) in a formula expressed as X+1 (X being when torque overcomes all voids and hits the wheel and then “1” is where the RPMs start the movement)

Theory of Operation
The prime mover is the source of the “power” ( available torque through whatever RPM range) so lets call that the “line” side. The driven side has all the resistive forces both static and dynamic. Lets call that the “load” side. What has been created here is a simple Constant Velocity Transmission that systematically balances incoming and outgoing torque during all ranges of motion.

(static defined as all the internal resistive forces as outlined above from the clutch to the point of contact of the wheel on the ground- dynamic being defined as any forces encountered during the rolling of the vehicle such as freewheeling[ where torque is released and RPM increases such as happens in mud] shock loads[ where resistance is greater than all available torque and motion stops such as when rut jumping where the grabbing force plus weight and other factors stop all motion for a moment and overloads the clutch until it releases[ hopefully anyway] and the ever present “slip force” where the transmission is fighting itself internally eating up torque because of tire and vehicle geometry results in the condition where all wheels are NOT turning at the same RPM and internally binding because of the absence of any type of limited slip capability)
Normally in an IC set up (internal combustion- there is a whole different set of rules for electric motors that won’t be discussed here) you goose the engine until it achieves whatever RPM the driver clutch is set to engage at. Its now under movement and does the same thing to the driven clutch. Now those clutches are in synchronous operation and together run until all static resistance is overcome. During this time the belt is trying to find its optimum spacing between the pulleys. Now you are moving and the line side drives the load side. The driver will normally be lower in the clutch at the start of any given change ( due to the fact it is the first to overcome resistive torque) and the driven is higher (once the vehicle is in motion, the force is transmitted smoothly so it turns easier- it will normally stay like this and adjust for any tractive spikes encountered because in the power train it would be considered the “variable” in relation to the “fixed” which is usually the engine because it is the more “constant” of the two) (In layman’s terms the driven pulley plays the role of shock absorber because the engine should be a constant source of even torque but there are an infinite number of resistive forces on the other end of the train) For discussion purposes we will say the two have now achieved a state of equilibrium so force can travel down the driveline.

Now you are rolling and strolling so as you goose the engine you increase RPM (speed) which wants to “dig in” the belt into the centerline which is corresponded to inversely by the driven clutch as it encounters and overcomes whatever resistive forces are encountered and again you reach equilibrium again at the new speed.

Strengths/weaknesses
Strengths- very simple, few parts, modular systems, easy to service, very reliable ( assuming proper design and load calculations) and have efficiencies above 90%
Weaknesses- There will ALWAYS be “dead spots” where the system is free wheeling while the belt is adjusting but these are usually minute and last for fractions of a second.( For IC engines only) There will always be internal dead spots where the system hammers itself increasing wear due to the fact that an IC engine(4 stroke) (unlike an electric motor in the same application) has only ONE load RPM (power stroke) and 3 unloaded RPM’s (intake, compression and exhaust) There’s nothing that can be done about that but over the life of a properly designed system- the effect is minimal.

IMPORTANT NOTE (Important for sizing, troubleshooting and comparing apples to apples)- By the functional criteria, these “clutches” ( V clutches used in tandem to form a CVT) are NOT centrifugal clutches so much of the information you read about CF’s will not apply and applying some of that information could work against you. A “true” CC has an inner unison ring attached to the shaft where there are a number of dogs (normally kept under stress by a spring which functions like a relief valve that opens and engages when a certain force is exerted) that are slung outward to grab a drum by inertia generated by RADIAL forces from the driver) The “V” clutch is more accurately described as a FRICTION clutch ( lateral force spring pushes the edges against the belt and grabs it) that is ACTUATED by the centrifugal forces applied to the belt by the driver. (remember the Titanic example- its simpler for the average person to relate to but not technically correct)

Adjustments
There are a multitude of adjustments depending on what the individual situation requires so those specifics are best handled per OEM recommendations.

Troubleshooting and Problem Solving
Assuming the clutches are adjusted properly and sized correctly for the application ( and excluding normal wear)- there is very little to tear up. Here are a few causes to look at.
Alignment-If you fail here, you just sighted the iceberg off the port bow. 90+% of all CVT failure and erratic operation starts here because it binds the clutches and that initiates cascade failure in a relatively short time.

All alignments start from the fixed end. In these vehicles that would be the driven clutch. (It’s the one on the fixed shaft.) This shaft and the PTO shaft of the engine MUST be parallel and perpendicular in all 3 axes. Then the pulleys must be faced equally on their own centerline to allow the belt to ride evenly. (alignment techniques are beyond the scope of this post because of the length) There cannot be any deflection or twist in the belt. Chances are that if the engine has no shims under it- there is an alignment problem.

Belt- NEVER put any kind of petroleum product on the belt. It will soak into the belt and destroy it from the inside. ( when we cut them and put the UV light on them under the microscope- you can really see it) The belt must be tightened to proper specification. If it cannot be then the motor needs to be reset to obtain it.

(note on belts- belts are made to ISO specifications and what that means is that for a given size, there is a RANGE of acceptability. This is a small number etched in the belt after the belt number. You could get a belt with say 10 on it meaning its within 10% of the dimension or 40 which means that belt is longer but within spec. This is what we call “matched belts” when using multiple belts. You need to find the lowest number you can. If you ever get the “right” belt but its too long or if you have 4 belts on something and when you tighten them you notice some are not as tight as others- its because that last number is not “matched”- this can cause problems)

Finish- as belts ride in these pulleys, they polish them. This creates heat, slippage and erratic operation. Periodically the pulleys need to be burnished by a scotch pad on a drill just like the average brake rotor. (some people will sand the belt also but my own experience tells me this is bad mojo except in extreme cases of belt glaze- its best to replace the belt)

If anyone has real chronic problems or wants more detail – just let me know and I’ll see what I can do to help.

[jeffery9076]

Nice write up guys. I did a terrible job lining up my clutches after the transformation from 6 chain attex to 4 chain. Could not get up any of the bigger hills I usually just walked up in the 6 chain no problem. I adjusted several times started blaming it on the rawhides I had to change to from wooly boogers. I was climbing small hill and it let out a squeal from hell. Took it home and made the wife line it up for me and I should say WOW . What a freaking world of difference. It was not the rawhides I love these tires for swimming. I have a brand new belt I will put on maybe. What is the difference in g force belts by gates I noticed whipper uses the on his high horsepower machines. I am running a 4 stroke 30 hp generac engine matching clutches from richard relics (I know expensive)I need to scotch brite the clutches.

[thebuggyman1]

I think you will find any modern belt to be far superior to the old stuff. Belts and hoses(rubber technology?) came a long way in the 70's/early 80's from the days when it was wise to change them every year or risk having your car towed to today when a serpentine belt may last 15 yrs (not recommended). In any case, rubber still ages, and even though you probably will not shred one, it will lose it's soft/suppleness and not work quite as well as a fresh one.