rk clutch and prerotators

[turbodog]

Is there anyone running a RK400 clutch on a gyro? How does it affect your prerotator engagement? Carey

[GyroRon]

I got one, works great. Smoother than without clutch

[gyro]

where do you get those clutches and do they fit in a rotax b box?

[Chuck Roberg]

Gyro, suggest you contact LEAF http://store.leadingedgeairfoils.com/
They show several clutches for the Rotax. But on their web site it does not say what gear box they are for.

I also checked CPS. Their clutch is only frr the "C" box.

[quadrirotor]

You can use those clutches only on "C" boxe: you can't crank the engine through this clutch so no "E" boxe!...and there is no place in a "B" boxe.

You must use this clutch on a gyro with big CARE, as there are some strong clues that suggest that a free wheeling prop in flight may become a strong brake that could lead you in a tumbling!...

[quadrirotor]

You must use this clutch on a gyro with big CARE, as there are some strong clues that suggest that a free wheeling prop in flight may become a strong brake that could lead you in a tumbling!...

[turbodog]

Ron that is what I figured, I have always disliked having to idle the engine so high with the regular gearbox setup. I have flown them on fixed wings and really like the lower idle speed. I doubt that there is enough braking force to cause any tumbling. Thanks Carey

[chuter]

I've got a clutch on mine and so far I really like it.

My engine idles around 2000-2100. I've tried pulling the throttle back to idle while flying and the engine rpm doesn't go lower than 3000. The clutch is still engaged at this speed.

I haven't tried actually shutting the engine off.

The next step would be to try throttling back to idle, reduce airspeed enough for the prop to slow down enough to disengage the clutch, then put the nose down to gain airspeed with the prop actually free wheeling.

[GyroRon]

The next step would be to try throttling back to idle, reduce airspeed enough for the prop to slow down enough to disengage the clutch, then put the nose down to gain airspeed with the prop actually free wheeling.


With the RK clutch, the prop is basically attached to a drum to there is no way, no matter how fast the prop is spinning for the clutch to stay locked up when you reduce power. The engine is connected to the clutch pack, a pair of shoes that push outward on the inside of the drum when the speed of the engine and clutch shoes is fast enough to overcome the force of the centering spring. If you adjust the idle on the engine down low enough, the prop will " disconnect " from the engine as soon as you reduce power to idle.

I set my idle down from around 2100-2200 before the clutch, to around 1300-1400 without. And it idles very smoothly and will sit there at idle all day like that. Chuter I think you need to adjust and lower your carb slides to lower the idle rpm and you will like the clutch even better. As it is you are only leaving a 200-400 rpm window between idle and clutch engaugement, I think a spread of 800-1000 is better.

[giro5]

My trike with a 503 and clutch had a vibration at 3500 rpm. CPS said to just go up thru it or down thru this rpm but don't stay at it. Never felt any hold back when reducing to idle and the prop was freewheeling which was every landing. Including pulling the control bar in for high speed - as fast as I could go- in the trike ie about 50 mph. Normal decent was 35-40 mph.

[chuter]

Ron,

I was thinking that as long as the wind through the prop keeps it above the speed where the clutch disengages then it stays engaged.

It seems to me that the shoes would stay slung out against the drum whether the engine or the prop is doing the driving; they don't care as long as it's above the engagement rpm...........what do you think?

[GyroRon]

Ron,

I was thinking that as long as the wind through the prop keeps it above the speed where the clutch disengages then it stays engaged.

It seems to me that the shoes would stay slung out against the drum whether the engine or the prop is doing the driving; they don't care as long as it's above the engagement rpm...........what do you think?

Sorry, but your wrong! :)

the only thing that the clutch is attached to it the engines crankshaft. When the crank is spinning fast enough, centrifical forces on the clutch shoes throws them out, making contact with the inside of the clutch drum. The friction of the material on the shoes face and the pressure of the centrifical force is all that makes the shoes turn the drum. Once you lower or totally take away the centrifical force - by bringing crankshaft speed down, such as bringing engine to idle or stopping the crank altogther, by turning the engine off - there is nothing to hold the shoes against the clutch drum. The prop would freewheel at this point.

If the spring in the clutch were to fail, it could possibly jam the shoes into a position that effectively locks them in place and give the effect of what your describing, but even then, the way this type of clutch works, it is really a one way power delivery, from the engine out... not the prop in.

[chuter]

Ron,
But...........if when I pull the throttle back it never goes below the engagement speed, then the shoes never pull away from the drum.

Ok, next time I fly I'll do my test; pull the throttle back to idle, keep my airspeed up and see what the engine tach says. Then slow the airspeed way down so (if my theory is right) the prop will slow enough to let the clutch shoes disengage and see if the engine rpm drops.

If the rpm drops then the clutch was staying engaged even though the prop was the driving force.
It may be a few days before I can get out to the airport to try it.

Want to bet a cburger on it? You already owe me one for figuring out you listen to country music.:whoo:

Edit: Ron, what happens on yours when you slowly pull the throttle back, keeping your airspeed up as you nose down? Does the engine go to idle at around 1300rpm?

[GyroRon]

Chuter.... I am beginning to wonder if were talking about the same thing here.

I am saying a few basic things...

1. When you lower the engines Rpm low enough to the point that the Centrfical forces no longer are strong enough to push the clutch shoes out again the drum, the clutch will no longer be locked up... NO MATTER HOW FAST THE PROP AND CLUTCH DRUM IS TURNING

2. That in order for your clutch to be working like it should, you need to set your engines idle several hundred Rpms lower than where clutch engagement begins - which is typically 2400 on mine -

What you have said in your posts that is clearly wrong is that either the prop or engine could cause lock up on the clutch. Only the engine can lock or unlock the clutch as the clutch shoes are only attached to the engine, not the prop.

I think you have your engines idle set too close to the rpm of clutch engagement and this is why you have seen the effects you have seen.

Edit: Ron, what happens on yours when you slowly pull the throttle back, keeping your airspeed up as you nose down? Does the engine go to idle at around 1300rpm?

This most basic way I can answer this question is this, As long as I have enough throttle opening on my engine to achieve a engine rpm of 2400 or higher, the clutch is basically fully locked up and it is as if there was no clutch at all, it is as if the engine and prop are directly linked to one another. Once I reduce throttle opening to a power level below what is needed to achieve 2400 rpms, the clutch shoes begin to retract from the clutch drum and the prop to engine link is no longer there.

Think of the clutch on a car or truck. Centrifical force isn't what holds the clutch shoe again the clutch drum ( I know it is usually a clutch disk and friction plate on a car or truck, but it is the same thing ) A heavy spring holds the two together. When you step on the clutch pedal the clutch is pulled away from the clutch " drum " and the engine and wheels are no longer connected. If you were to picture how it works when driving a car or truck this way and just imagine that at or below a given engine rpm the clutch pedal is pushed in , maybe this would make more sence

[chuter]

I think we're seeing the clutch the same, I'm just saying that once it's reached its engagement rpm, it's engaged, like there is no clutch (like you said). After that it stays engaged until the rpm of the clutch drum/shoes/crankshaft falls below 2800 rpm.

If the prop never lets it get below 2400-2800rpm, then it seems like it would stay engaged as a solid unit.

Next time you go flying try what I suggested. I haven't tried it yet so I'm just going on shade-tree engineering theory.

[GyroRon]

Chuter I HAVE tried what your saying.... I almost always on every landing go from 70 mph airspeed and 5500-6000 rpms and suddenly chop the engine to idle and the engine instantly goes to idle, meaning the clutch has disengaged. Either you have your idle set too high or your being too gentle with the throttle lever.

You are not getting the point that the clutch shoes are attached to the engine only and if you reduce engine speed the clutch shoes will pull away from the drum, no matter that the prop is spinning.

[GyroRon]

Can't someone else here that is smarter than me help explain this? Maybe Chuck Beaty or Udi or someone else can find a better way to explain how a clutch works so Chuter would understand?

[chuter]

Ron,

I've known how a centrifugal clutch works since I had a go-kart at 13 years old, and then I worked on cars for a living for about 28 years. I think I get the concept.

You may be right about my idle being too high. All I'm saying is that from what I've seen with mine up to now, it appears as though the clutch is staying engaged if the airspeed stays up.

I'll try what you've suggested about setting the idle down and see what happens.

[GyroRon]

Well Mike, use the Go kart for example.... If your hauling ass down a hill with the Go kart and you take your foot off the gas pedal, doesn't the clutch disengage?

I am not suggesting your not smart or understand how things work, just that your not understanding that the clutch you and I have on our gyros works exactly the same as the one on a Go kart.

[richardkennedy]

I think you're both right. I think Michael is indicating that even though the throttle is pulled back to idle, the prop rpm is keeping the engine crankshaft turning too fast to reach the disengagement speed of the clutch. Kinda like when you downshift on a manual transmission, the energy from the inertia of the vehicles weight and momentum make the engine rev up.

[chuter]

At this point we just have to test the theories.

[Aussie_Paul]

[QUOTE=GyroRon;141506]Well Mike, use the Go kart for example.... If your hauling ass down a hill with the Go kart and you take your foot off the gas pedal, doesn't the clutch disengage?
QUOTE]

Ron, that statement got me thinking. I have never used a centrifugal clutch so I am thinking theory wise.

I don't believe that the go kart clutch would disengage due to the wheels driving the engine. The drive is direct from the ground to the wheels to the clutch to the engine and does not allow the engine to get low enough in rpm for the clutch to drop out.

Take your foot off the gas pedal in your car and the engine rpm does not go to idle. The engine rpm HAS to get below the clutch engagement rpm to disconnect.

It is very easy for me to get confused with this.:D

Aussie Paul. :)

[GyroRon]

Richard and Paul.... Think about how a clutch works, a RK-400 clutch ( go to their website and LOOK at the clutch shoes and drum! ) and then please tell me how the prop turning or the wheels spinning on the Go kart can keep the shoes in contact with the drum once you reduce the power to idle.

I am telling you guys I do almost all my approaches as simulated engine outs and by this what I mean is I will be flying downwind just a few hundred feet off the side of the runway, at cruise airspeed and power settings, and suddenly yank the throttle closed, and then turn quickly to final and land. When I yank the throttle closed the engine instantly disconnects from the prop and engine rpms drop to idle power of 1300-1400 rpms. If what your saying is true, then my engine would stay at a Rpm of at least 3500 to 4000 Rpms till I landed. I am telling it doesn't.

[Timchick]

I believe you Ron.

[gyro]

Guys this is so simple don’t turn this into another thread like the one (plane on a conveyor belt…will it fly?)

I work with centrifugal clutches all the time. Regardless if it is attached to the engine the outer housing will over ride it and act like a Jake brake.

Let me explain….let’s use the go cart thing as this is where I have experienced it. We ride down hills all the time and when we take our foot off the gas the momentum of the cart keeps the outer housing spinning so fast that the pads stay engaged for awhile, (it even makes a weird sound when it’s the wheels driving the clutch and not the engine), anyway when we get close to the bottom of the hill the clutch housing RPM drops and then it disengages and the cart actually picks up speed as it is no longer trying to push against the compression of an idling engine. The engine was well into idle before we got to the bottom of the hill.

Now a prop is going to act quite different as it does not carry the momentum (gear reverse ratio) that a heavy go cart does. When Ron chops the power, the drag on the prop is so great that it slows almost in unison with the engine RPM that it disengages and free wheels. Unless you’re in a 150 mph dive I don’t think that the prop could keep the (outer housing) of the clutch spinning fast enough to stay engaged.


I know this still may have some grey area to some so let’s add a Pic and put on our thinking caps

Below is a pick of the inside of a centrifugal clutch lets say it take 1000 rpm to over come the 2.0lb springs and allow the 20oz pads to sling themselves into the outer housing. Now the engine is throttled up to 2000rpm the 20oz pads now weigh twice as much and due to the G forces from the RPM.

Now we need to add a fly wheel that this clutch is driving such as a 100lb disk. Let’s now kill the motor… Natural thinking would be that the pads would instantly retract but they must first slow down to the point that the 2.0lb springs can pull them in. Remember now these pads are planted hard against the outer housing and until it slows down and the centrifugal weight of the pads becomes less than that of the retracting springs you will have an outer clutch override!

[Aussie_Paul]

Exactly Gyro.

Aussie Paul. :)

[Chopper Reid]

"Chopping" the power isnt what I would call good practice full stop.

[chuter]

My observation of my machine agrees Gyro's explanation, but let's not discount Ron's observation on his machine.

Maybe there's a difference between tractor and pusher; my prop being in cleaner air.

And I haven't really tested this thoroughly; Ron may be right about my idle being set too high.

If weather allows I'll go to the airport this weekend and do some more checking.

(This isn't exactly a critical part of the gyro flight envelope, but it's giving us something to stew about):wacko:

[Aussie_Paul]

Michael, I don't think there is any doubt at all that your idle is set too high for an engine with the clutch.

Aussie Paul. :)

[chuter]

My thinking on keeping the idle as high as possible without engaging the clutch was to try and minmize plug fouling.
Maybe it doesn't make that much difference, but 2-cycles in general tend to foul plugs at idle.

[Aussie_Paul]

The modern 2 strokes don't seem to be a problem with that. My friend here has been operating with the clutch for several hundred hours at 1400 rpm idle and no problems.

Aussie Paul. :)

[chuter]

I thought one advantage of oil injection was supposed to be less fouling at low throttle settings........? (I use premix).

[gyro]

Chuter. It would be nice if you and Ron both could put prop tacs on your machines (provided they both have the same prop and pitch). I'm curious... what would be the rpm of a tractor at 60mph vs a pusher at the same speed.(engine at idle) I think it's obvious that a tractor get the cleanest air and would spin faster but how much???