Seen a comment of this subject over on another forum....

...the guys telling you not to run the engine without a clutch are correct, kinda.
The engine will run just fine without it and it should not cause the run-away problem that you mentioned.
The engine was designed to have that extra weight on the end of the crank for balance reasons.
Torsional vibrations are the reason that the Rotax engines have dampners on both the clutch and flywheel.

I've run the engine without a clutch on. I had such a hard time to get the engine to run over 7 grand. Was totally furious, removed the clutch, started the engine, pegged it and did not care if the engine sent the connecting rods thru the case via air mail to China. :cussing:

...never did blow up. :angry:

hard time to get it to spin 7 grand without the clutch?? I personally don't think you could easily send a rod out the side unless you spin it at 20 grand (well, maybe not 20 grand), but as soon as you get past the pipe it'll just four stroke, kinda like a built in rev limiter....now if you lean it out big time and try it again you may have different results.....try it and let me know...

whuhh...now that I read what i wrote, i missed a few details. "tired last night"

It was one of our H2oX engines. When we would test on the beach the engine would barely muster up 7000+ rpm.
Why wont it go?
...did all the tests, compression, leaned the jets, checked ignition, changed ignition, changed stators, changed mag, changed beer brands, changed my gotch...
*sigh*
Put all of these engine parts including the crank into our "winning" engine....ran kick a$s..

Put all the parts back into the original engine....7000 rpm.

Took clutch off and the engine went off the tach. Ooh I was soooo mad im surprised that the engine didnt seize from overheating. Basically Rocketman pulled the tether when i wasnt looking.
...Oh well, didnt blow up like some guys will say if there is no primary on the engine.

Found the problem. Something about the bottom of one exh port being too low, shorting out the charge into the pipe or something like that. Changed the cylinders and the engine ran fine.

Anyhoo...my point is, I dont think that running the engine without the clutch will lead to disaster in the short time that people do run the engine like that.

:) Joe, I was told by a Ski-doo Rep not to run the engine without the primary clutch. I asked him the reason, and "he" told me that the primary clutch acts as a counter balance and could cause the crank bearings to go. It made sense to me because of the added vibration to the crank and connecting rods. But then again no problems with you running yours without the primary clutch. Hmmmm, makes one think a little bit. ;)

i have also heard about this counter balance and thats why u should never run an engine with out the primary clutch on it.

if you like to, or in racing situations, should, tear the motor apart and go through everything, you should never run it without the clutch on. if it is siting in the garage waiting for the snow to fly, and you go rideing to have fun on the weekend, or whatever, don't do it! harmonics and balance is the main thing, with no clutch and a heavy flywheel the balance is all screwed up, compression isn't exactly the same in all cylinders, the crank and bearings will be abused. the clutch isn't only balanced cintrifugally, but laterally as well with the entire bottom end ballenced as a unit. ;) but what do i know ??? ??? :D just an opinion.

man, these engines sound pretty tender if running w/o a clutch ruins them....I just can't see how a little bit of extra harmonics is gonna trash a roller bearing crank...I almost want to say any dampening afforded by the clutch is primarily for clutch longevity vs. the engine, just my guess....at work we run engines (four strokes) several hundreds of hours with SEVERELY out of balance pulleys and have yet to see any engine damage...just accesories breaking off is all.......

I would strongly advise not to run a snowmobile engine without the clutch...the reason being that it acts as a harmonic balancer to smooth out the power stroke of each cylinder...otherwise your crankshaft will literally go to pieces...any of you that have built an auto engine for the street or the race track will understand this...the more horsepower an engine makes, the more critical it is to have a harmonic balancer that is made to handle the horsepower...Motorcycle engines also have a harmonic balancer, ie-the clutch, F1 motors...any piston motor has one...the only engine that I can think of that does not have one is a turbine engine...Hope this helps...Al.

I believe that since the clutch is not pinned or keyed for positive orentation that is does little to balance vibration. If it was balanced with the crank,rod weight and piston weight than it has one correct way of going on and it should be held with more than a taper lock because a taper lock can slip. Even a neutral balance harmonic balancer is keyed to go on one way (350 chevy). Harmonic balancers disipate tortional vibration how does a clutch dissipate this motion? Running without a clutch should not hurt the motor until you reach an rpm that the crank tortional vibration comes in step with cylinder firing frequency. In the oct/nov 1999 snow tech had a great artical on engine vibration.

99zx: A snowmobile clutch ie, tra, is a balanced unit when both sheaves alignment marks are lined up...a tapered crankshaft on a snowmobile engine does not need a keyway...its a press fit...a harmonic balancer on a 350 chevy engine is keyed because the timing marks are on the harmonic balancer...the timing marks on a ski-doo are on the magneto, which is keyed to only go on one way...artic cat has available offset keys to change the timing...A harmonic balancer is alot smaller and weighs alot less than a snowmobile clutch...how the h/balancer works is there is two steel sheaves with a medium made of rubber or a fluid (Fluid Dampener for high performance) this medium acts as a shock absorber...a snowmobile clutch, just because of its sheer mass does the same thing...Hope this helps, Al. :)

Okay, I understand the whole balance issue. What happens to people who run a Comet clutch on a Ski Doo motor? Are they all balanced for a certain motor? Reason I ask this is that I plan on running a Polaris clutch on my 583 Doo motor? Is this going to prematurely ruin my crank bearings? I know other people have done this, but never heard anything bad about it. Is the weight difference so little that it doesnt effect things?

Originally posted by Allen Avram@Jun 28 2003, 09:57 AM
I would strongly advise not to run a snowmobile engine without the clutch...the reason being that it acts as a harmonic balancer to smooth out the power stroke of each cylinder...otherwise your crankshaft will literally go to pieces.
I'll have to remember that next time I spin a snowmobile mill up to 10 grand on the dyno. It's going to be real hard to adapt a TRA or Comet clutch to fit the waterpump (torque arrester) assembly. We are not compairing apples to apples here. The crankshaft on a two stroke cycle engine is internally balanced and has a fourth order balancer built into the magneto side. Pulling the permanent magnet's field through the laminated cores of the stator and generator windings effectively dampen harmonics experienced by the crank. secondly, the two stroke cycle engine experiences a firing impulse every rotation of the crankshaft as opposed to every two of the four stroke cycle engine thus eliminating first order high amplitude harmonic vibration. Ever wondered why triples have different mags and tachs compaired to twins (6 trigger vs 4 trigger). Automotive engines suffer from firing order impulses, harmonics created by cam and valve gear transmitted through timing chains hence harmonic balancers, composit camshaft drive gears, belt driven cams and externally (large block & 4.00" stroke small block Chev) verses internally balanced rotating & recipricating assemblies. :cussing:

wow, a v-king!! one of the absolute toughest looking boats in my opinion...along with the HST...........

Originally posted by kielbasa@Jun 29 2003, 11:28 AM
wow, a v-king!! one of the absolute toughest looking boats in my opinion...along with the HST...........
kielbasa, It's actually a V-King tunnel (center steering & foot throttle). I had it special order from O'Brian marine Ft lauderdale FLA. The Merc is 300 prop HP Blue printed and F1 transfer ports & twin plug heads. It'l touch 110 on radar, but very tricky to stay on the straight and narrow. She has a nasty side, Chine Walk and Blowing over in mild breezes. It's showing its age these days, I'm looking for a 22' Warlock catamaran but I'll need another 2.4.

The engine will run fine without a clutch and I agree with reducing torsional vibration amplitudes, but I disagree with any balance reasons.

Everything vibrates when it is impacted or forced upon. Depending on the size/mass/shape of whatever you hit or force upon, it will vibrate at a natural frequency.
*A tuning fork for example is tapped; you can hear it hum at its natural frequency.
If you hit it harder, the fork will vibrate at the same frequency, but it’s louder, you are increasing the vibration signal.
*If you rub your finger on the tuning fork it will vibrate at the same frequency but low enough signal you may not hear the fork sing.
*Rub the top of a wineglass with a wet finger using the right down force and the glass will sing at its natural frequency.
*Hit a piece of steel with a wooden bat, the steel will vibrate at its natural frequency.
*Hit the same piece with a hammer and the steel will vibrate at its same natural frequency.

The frequency of is always the same...the amplitude/signal strength will be different, the sound will be louder or softer.

So what's this have to do with an engine?
Every pulse of the power stroke imparts a "forced" vibration on the reciprocating assembly. The piston, the rod, the throws, bearings all will vibrate at their natural frequencies, but being that they are all connected they will combine and have one frequency that it resonates at...
...Each time the power stroke pulses.

Two ways to change the natural frequency of a unit.
1] Stiffen the structure - Raises the natural frequency. Vibrates more cycles per second.
2] Add mass - Lowers the natural frequency. Vibrates less cycles per second.

Example, for a tuning fork to make it hum at a higher frequency, you can place a piece of wood or steel or anything between the forks. You tap the fork now and it is stiffer, it will vibrate at a higher frequency.

Example, for a tuning fork to make it hum at a lower frequency, you can wrap several elastic bands around it. You hit it, the frequency will be lower. Say it vibrates at 60 times/second, now with the bands on it; it will vibrate at 55 times/second. It is heavier, you added mass. Clamp a pair of vise grips on the fork handle and it becomes one unit...a heavier unit. The time for the energy wave to travel from one end of the fork to the other is slower. The fork vibrates at a lower frequency.

A two stroke engine...You add the clutch and/or damper, magneto..etc and it will promote the natural frequency of the reciprocating unit to vibrate at a lower frequency. The power pulses will have less impact on the unit and become more of a force vibration.
On an engine with journal/sleeve type bearings its well known that if you do not have a damper unit of some sort damage will occur to the crank. Being that the crank has no rolling elements [roller bearings], without the damper a "whip" will occur at certain engine rpms. This whipping causes pressure points of the crank journal to touch the bearing material. So the oil wipes away and soon then the bearing material is wiped off...not hard to figure what happens next.

I cannot really see damage resulting from not having a clutch on the engine. There is no electrical arcing, contaminated lube, dynamic overload, bearing friction, material striking material, roller skidding. There has to be something done to cause metal degradation or a roller going over a subsurface defect to create an eventual failure.

The "no clutch" thingy just doesn’t hold much weight with me.


...hee hee hee. Ok guys, I was being kindof a smartass asking this question to see what kind of answers would come out. :devil: I do vibration analysis for a living, study/analyze bearings, balance any rotating system, oil analysis, ultrasonic testing, electrical problems.

i dont know of m/any reasons to run w/o a clutch. so why risk it? good or bad? more weight on the crank causes it to react slower. arent dampeners mainly just a big weight?

last winter i put on my 96 z tra on my 02 mxz and it sang , it sounded like the spring was echoeing . did'nt keep it on long , sounded like a symphony under the hood

Originally posted by Thumbdoctor@Jun 29 2003, 08:38 PM
kielbasa, It's actually a V-King tunnel (center steering & foot throttle). I had it special order from O'Brian marine Ft lauderdale FLA. The Merc is 300 prop HP Blue printed and F1 transfer ports & twin plug heads. It'l touch 110 on radar, but very tricky to stay on the straight and narrow. She has a nasty side, Chine Walk and Blowing over in mild breezes. It's showing its age these days, I'm looking for a 22' Warlock catamaran but I'll need another 2.4.
If it'll do 110MPH on water, that must be f***ing FLYING!!! Wow that must be a blast to drive.

Originally posted by mx_462@Jul 7 2003, 10:49 AM
If it'll do 110MPH on water, that must be f***ing FLYING!!! Wow that must be a blast to drive.
Drive NO No No; Fly on ground effect of water!!!

"On an engine with journal/sleeve type bearings its well known that if you do not have a damper unit of some sort damage will occur to the crank." tell me what happens ??? ? as I have been building sprint motors for several years now with journal sleeve bearings and no dampner.I know we are not the only ones doing it either,so what happens?I will add I can get a pic of the bearings out of the motor after 39 races and there is no copper showing. what I read is we'll wipe out the bearings,but in the last 10 years that has never happened,harmonics have nothing to do with it either.oil pressure is what maintains the clearance between the crank and bearing,now if I did not have proper pressure then what your saying would come into play."There has to be something done to cause metal degradation or a roller going over a subsurface defect to create an eventual failure" degradation of the metal comes from fatigue,resulting from the harmonics(which correct me if I am wrong is nothing more than vibration).

These sprint engines for sprint cars...
...do they have starters and/or get push started?

How many gears do they have in the transmission, but morely how many gears are used in a race?

no starters,they do get pushed off.transmission,they have none.you are either in gear or out.there is no shifting the engines are pulling the load the whole time the car is running,provided the car stays in gear.which means the bearings in the engine are taking a beating as are the rods,pistons and crank.we done some testing a few years back trying to build carbon fiber pushrods.they would not hold up once the engine hit 8400 rpm they exploded,everytime.what we determined was the cause was that the carbon fiber would not withstand the harmonics of the engine @8400.when I said 8400 it was 8400 everytime they exploded.we had 15 sets of pushrods made and none are still around,they all came apart when on the dyno.my point harmonics are not good for the engine ,as vibration as you know does cause fatigue.which leads to failure.

dooman is it possible that piston speed broke your rods and not harmonics? as rpms increase piston acceleration and deceleration are quicker.

he's talkin' pushrods...you know, four stroke....

i see. ah yes the other kind of motor.

sorry i was confused.

doesnt seem like a big gain could be made that way...please explain.

I think what they were trying to accomplish was reducing "sprung" weight in the valve train. Less weight in the valve train = more rpms, less valve float, more HP.

Brian


We now need to stear back onto the subject of running a sled engine without the clutch. ;)

all you guys like "safe". running your engine w/o a clutch is not safe period. not because of a runaway or balance problem for a dampening problem as was stated. the clutch acts as a damper and it cushions everything inside your motor. personally i wouldnt even run it w/o a belt on.

Originally posted by tifa_5_2000@Jul 17 2003, 05:03 PM
all you guys like "safe". running your engine w/o a clutch is not safe period. not because of a runaway or balance problem for a dampening problem as was stated. the clutch acts as a damper and it cushions everything inside your motor. personally i wouldnt even run it w/o a belt on.
Right on! You got it, and I wouldnt agree with you more.


Brian :hallo1:

I am with both of you,I would not run it without the clutch either. :thumbsup: was we straying from the topic brian :sarcasm:

Originally posted by dooman@Jul 15 2003, 11:11 AM
no starters,they do get pushed off.transmission,they have none.you are either in gear or out.there is no shifting the engines are pulling the load the whole time the car is running,provided the car stays in gear.which means the bearings in the engine are taking a beating as are the rods,pistons and crank.we done some testing a few years back trying to build carbon fiber pushrods.they would not hold up once the engine hit 8400 rpm they exploded,everytime.what we determined was the cause was that the carbon fiber would not withstand the harmonics of the engine @8400.when I said 8400 it was 8400 everytime they exploded.we had 15 sets of pushrods made and none are still around,they all came apart when on the dyno.my point harmonics are not good for the engine ,as vibration as you know does cause fatigue.which leads to failure.
How did you figure out the harmonics of the engine?
What did you use to analyze these frequencies?
What frequency did the engine resonate at?

Could the connecting rods have been forced past their elastic limit to explode?

What is the point of this topic? :(
Why would you want to even try to run the engine without a clutch? :slick:
Cant go anywhere without it. :lol:
I dont know how you can even start it anyway, I have my clutch off right now and I can barely turn it over for fear of snaping the rope. :ohmy:

Just wondering :undercover:

By them selves the clutches are balanced neutral.

The weight of the clutch spinning on the end of the crank allows for the firing impulses to be more even.

Example when spinning at a low RMP the extra mass that comes along for the ride helps the crank rotate around between the firing of piston 1 and the compression of piston 2. There is a window of declining force after TDC of piston 1 and the compression increase of piston 2. Without the extra rotating mass the firing is more uneven. It is hard to explain. Basically the mass carries the rotation around through the rising and falling strokes better than not having the mass there at all.

Having the belt installed is a good idea for other reasons. Primarily to keep the clutch fron damageing itself.

My 2 cents. I could be wrong but it is common physics.

Chris

M]What is the point of this topic? :(
J]I am vibration analysis technologist and. I like to see what people think and what they here whether it be fact, heresay or rhetoric.

M]Why would you want to even try to run the engine without a clutch? :slick:
J]To prove the ticking sound is not the clutch.

M]Cant go anywhere without it. :lol:
J]Wont go anywhere if ticking turns into bOOm.

M]I dont know how you can even start it anyway,
J]Simple...switch to on...prime w/gas, pull chord...

M]I have my clutch off right now and I can barely turn it over for fear of snaping the rope. :ohmy:
J]You have arms the size of Arnold then.

M]Just wondering :undercover:
J]thereyago..

Ok joey, you allways have an answer for everything :hallo1:

I only run a little over 140psi and it is a bear to turn over :whatever: Can imajine what 150+ compression would be like w00t

Do we all remember the "fluid dampener"? When it first came out it was like $400.00 w00t So what ever happened to it and did it really do anything?

So, Joey...? What do you think of Redline's new isolation system?

Redline'snew system on Max sled (http://www.maximumsled.com/maximumsled/snowmobile/articles_layout.asp?articleid=473&zoneid=4)

A waste of good design money? Or just a good idea with time well wasted?

If there are any industrial millwrights lurking out there, I bet they'd think the elastomer element looks like a Lovejoy insert.... doesn’t it? he he
Just them saying about lower belt temperatures due to the element between engine and clutch then this would be great for a troubleshooting tuner. Temperature on a primary clutch can tell the tuner a few things wrong with the system; i.e.:over rev due to lack of flyweight
I agree with their other claimed benefits.

I'm not so sure on the design eliminates vibration between the engine and transmission.
To me the element under load is like a steel band, otherwise it would shear in half, no?
Being steel bands are flexible, maybe the vibration would be attenuated slightly at first, however I know factually the elements get "torqued" from acceleration and take on a permanent set. When this happens, the machine will usually show a marked increase in vibration, which with vibration data recorders can easily be seen. Simply replacing the coupling elements cures the problem. I kind of like the little or no maintenance feature of this coupling.

...im a Reliability specialist involved in Vibration analysis, and study deterioration of many types of couplers in industrial environments.

I like the idea of the designers trying to seperate the engine heat and vibration from the whole CVT system. I like tha fact that it looks "simple simon", but I remain a little sceptical. I'm sure it doesn't iliminate 100% of the vibration, at least with this system you could use lighter clutch components and not have to worry about the long term "damage" of engine/clutch harmonics. Plus it looks perdy :D

CIS (http://www.redlinesnowmobiles.com/pages/clutch.html)