Psru

automan1223

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Prop hub

Prop hub

Somewhere on my computer I have a photo of a prop hub that separated the shaft that was driving it as it was in TWO PIECES. It would be great to see what "improvements" you guys made vis a la prop shaft / hub retaining system.

The clutch is a bad idea. EVERY CLUTCH I have ever worked with develops problems somewhere down the line.

If you really wanted to have a piece of engineering. Make the unit driven by a sprag setup. A one way roller sprag is the way to go. They are smooth at all power settings, cold, hot, high & low. Minimum moving parts, no clutch to wear out or come out of true to vibrate and go self destruct. Copying some elses design may be a place to start but not where it should end. That is piracy.....and it is not well received here.

Jonathan



Not wanting to upset some of the belt driven and geared PSRU experts, I often wonder if they fully understand the requirements of a propeller reduction gearbox and the damaging effect that the torsional excitation produced by piston engines can have on gears, shafts and propellers. Subaru engines are not alone in this predicament; all engines have some degree natural frequency. A PSRU cannot be treated as an isolated entity.

In a moving mechanism, the dynamics of springs have to be analyzed too, valve springs in an engine have their own natural frequencies, and the core mechanic must ensure that springs are operated well under their first natural frequency at maximum engine speed, if not, risk damage to the pistons because the springs may not return the valves in time.

Our centrifugal operated pressure plate/clutch will not absorb and vibrations other than give back in this case the Subaru engines the proper balance and most important able to idle the engine without the propeller engaged. Starting a car in gear is not so health for the gearbox. We are working on a prop brake as with the centrifugal clutch there is a down site with the loss of glide distance after an engine out and we are stuck with a wind milling prop. The original reversed engineered box has been elongated to take the additional centrifugal clutch and after some Dyno testing and a flight implementations and to impress the buyer we have to accumulate at least 1000 hours and I guess at 2000 hours they will be sold.

To avoid confusions, the posted pictures, have the centrifugal clutch omitted (obvious reasons) but it gives some indication on our R&D. Hopefully we would be able to market the centrifugal clutch not only for Subaru engines.

Thanks
Albert



 

1946

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Somewhere on my computer I have a photo of a prop hub that separated the shaft that was driving it as it was in TWO PIECES. It would be great to see what "improvements" you guys made vis a la prop shaft / hub retaining system.

The clutch is a bad idea. EVERY CLUTCH I have ever worked with develops problems somewhere down the line.

If you really wanted to have a piece of engineering. Make the unit driven by a sprag setup. A one way roller sprag is the way to go. They are smooth at all power settings, cold, hot, high & low. Minimum moving parts, no clutch to wear out or come out of true to vibrate and go self destruct. Copying some elses design may be a place to start but not where it should end. That is piracy.....and it is not well received here.

Jonathan
The mentioned clutch has no friction to wear out; once certain rpm are obtained the fingers work on the pressure plate and lock up the propeller. Reverse engineering is not copying, it’s improving a product, and I am aware many are misinformed about it. I appreciate your suggestions.

Thanks
Albert
 

NoWingsAttached

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Thanks for the photos Albert.
 
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1946

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Thanks for the photos Albert.
Ops, this is a response to a removed post.

We wanted to keep the initial box housing but to accommodate the centrifugal clutch had to be elongated and some modifications as pointed by Hillberg ,looked seriously at sprang clutches; we think they do work well but it would mean even a longer elongations to the box. We are using the flexible coupling (Centaflex) between engine and box shaft but still we don’t know until Dyno test are performed and measures are taken and see how it will behave with the centrifugal clutch. In respect to wear and tear, you have a good point, everything wears out eventually.

Thanks
Albert
 
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Heron

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I think it is time to let go on the poking . . .if this is a serious venture!
Mentioning what people know or don´t, think or not is just invitation for more of the same.
Lets move on! Will e-mail you . . .
thanks
Heron
 

automan1223

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Clutch vs sprag.

Clutch vs sprag.

You are adding more weight and complexity to the unit for a minimal gain in benefit. You could rework the output shaft to accommodate a sprag and not have to change a thing box wise. The sprag could fit under the driven gear and work its magic.

J
 

1946

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You are adding more weight and complexity to the unit for a minimal gain in benefit. You could rework the output shaft to accommodate a sprag and not have to change a thing box wise. The sprag could fit under the driven gear and work its magic.

J
I am hearing what you say, the original box was delivered with a used re-machined flex plate welded onto a crown gear, the Subaru EJ254 DOHC N/A OM flywheel weighs 7.2kgs with the original arrangements (flexplate) we were missing nearly 5kgs thus losing the harmonic balance of the engine. The centrifugal clutch/pressure plate and the flywheel come to what the prescribed Subaru OM flywheels are delivered. We firmly believe in keeping the engines balanced to factory specifications.

Since you mention twice sprang clutches, I would suggest to read this interesting article about the magic’s of the sprang clutches and perhaps a warning to their implementation in a PSRU.

Picture shows the original arrangements of the PSRU

Thanks
Albert



A Dangerous Hoax

One of the most dangerous designs we have seen is a PSRU that contains a sprag-clutch with a magic-sounding name ("LCD", or "Linear Coupling Device"). Surreal properties are claimed for this magic device, specifically, that "...it isolates all the engine shock and torsional excitation from the gearbox".

That’s a curious claim in view of the fact that the clutch is downstream of the input gear in the examples we have seen (located in the output shaft in one case, and in the idler shaft in another). But, on the other hand, nothing claimed by that particular peddler is surprising.

It’s even more curious that the purveyor of this PSRU alleges that "...the magic device can couple and decouple as fast as 75 times per second, which breaks the resonance feedback loop". However, the manufacturer of this "device", which is no more than a commercial sprag clutch, states in their engineering data that the maximum rate ever achieved with this clutch is 20 Hz. However, that PSRU peddler has demonstrated himself to be completely untroubled by contradicting published engineering data or widely-accepted scientific facts.

We have already shown through some fundamentally simple calculations (Vibration Basics) that the destructive PSRU vibration loads are applied at frequencies ranging from 240 Hz to 320 Hz. (three to four times faster than the max CLAIMED rate of the wondrous "device", and more than 10 times its ACTUAL rate).

SO IF a one-way clutch which actually HAS a maximum rate of 75 Hz were driven by an 8-cylinder engine, it would become a solid coupling above 1125 RPM, barely above idle. Therefore it is clear that, even if this "device" COULD couple and uncouple at 75 HZ, it would be completely inert at the frequencies which excite the destructive vibrations.

The design of this particular PSRU caused the first mode resonant frequency of the propulsion system I examined (a V8 engine, this vendor's PSRU, and a composite propeller) to be about 3700 RPM (right at the bottom of the cruise range). At max takeoff RPM (4700) the system was not even close to crossover RPM (5230). Imagine the forces at work to destroy that system.

There are other severe problems with this sprag-clutch implementation, however. The PSRU vendor claims that the clutch decouples the propeller from feeding back vibratory energy into the system. It purportedly does this by disengaging the engine from the PSRU during the part of the torque cycle in which the instantaneous engine torque is low (a torque "valley"). So far, so good.

But when the next cylinder of the engine fires, the PSRU input shaft accelerates freely (it is not driving any load because the magic-clutch has decoupled). When the shaft speeds match, the output shaft is still at a relatively constant speed while the input shaft is accelerating rapidly. Suddenly, BANG, the clutch re-engages, imposing an extremely high shock load on the gearbox and propeller because the re-engagement of the clutch picks up the entire engine output over a period of a few microseconds. These high shock loads (hoop stress) fractured the vendor's early version of the clutch outer race in a relatively short time. The only way it could be made to survive was to make the walls VERY thick ( heavy ) And that simply moved the impact loading problem to another component.

Further, even if the clutch did reduce the gain of the resonance feedback loop, it does nothing to isolate the gears or the propeller from the torsional excitation (engine peaks times transmissibility) the engine produces.

Worse yet is the fact that with a one-way clutch in the PSRU, when the pilot reduces the engine power in flight (for a quick descent from altitude, for example) the propeller becomes freewheeling. Thus, if the airspeed remains high during the descent, the propeller can easily overspeed and shed a blade. Compounding the problem, the pilot is unlikely to detect the overspeed until a disaster happens, because both the sound of the engine and the reading of the tachometer confirm to him that RPM is decreasing.

The vendor of the PSRU-with-sprag-clutch adamantly denied that the propeller will freewheel when power is reduced. Then later, to validate his design, he produced an engineering analysis of his PSRU by a university professor. That study states unequivocally that the propeller will freewheel when power is reduced. When questioned about that discrepancy, the vendor responded: "The professor does not know what he’s talking about". Amazing?

A client of ours proved in flight tests that the propeller on this PSRU does freewheel when power is reduced, exactly as stated here. He also found, to his chagrin, that when it freewheels in the landing flare, it removes the expected propeller drag and greatly extends the rollout.

Note that helicopter gearboxes use a sprag (one-way) clutch between the engine and the rotor drive gearbox. The purpose of that clutch is to automatically disconnect the rotor system from the engine in case of an engine failure. That allows the rotor system to be propelled by the sinking of the helicopter through the air, thereby allowing the pilot to maintain control of the aircraft during the descent and to use the energy stored in the rotor system to decelerate the aircraft to a successful landing. It’s called "autorotation".

We have used a pair of sprag clutches in the input coupling to our double-engine gearbox (the Mark-14) for the purpose of automatically disconnecting a failed engine from the prop and allowing the remaining good engine to continue to power the prop. Because of those sprag clutches, the Mark-14 allows the prop to freewheel when power is reduced (described above), but it is an acceptable compromise since the gearbox was designed primarily for a race application.

EPI.Inc.
 

StanFoster

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1946- Now that last post was very interesting and educational.


Stuff
 

1946

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C´mon guys . . .you started to frighten me . . .
Making sense? Whats next . . .???
Heron
It is hard, hopefully some will take notice there is a lot to be learned here and some interesting innovation come to light.

Thanks
Albert

 

Heron

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I haven´t!
But if they are interested we can use Private messaging here on our Forum . . .
So far, it all looks good, but when its time for hard ball, lets see . . .
WE need more options, I need a job, it is on a field that I like, aviation, have some knowledge, can travel abroad, speak several languages.
Good candidate, if the product has some quality, it will be a match!
Heron
 

automan1223

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Eating Cake.

Eating Cake.

Listen, .....that was a nice long winded article written by someone who has ZERO time with proof of concept under their arse. Sprags work, and they work well. They work with cars, trucks, aircraft etc.

I have been running a New Horizons gear box that uses a sprag for well over 200 hours. Runs great, smooth, powered by a worked subaru ej 22. or should I say carb fuel supply. Engine made close to 700 lbs of thrust on a heavy 2 place before it crumpled the nose wheel.

There are units in service well over 1000 hours.

What is the problem ?

Build it, see what it takes to blow it up. But please do not "borrow" someone elses homework.
 
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automan1223

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This whoppper needs a happy meal toy !!!

This whoppper needs a happy meal toy !!!

Quote from post #

"Worse yet is the fact that with a one-way clutch in the PSRU, when the pilot reduces the engine power in flight (for a quick descent from altitude, for example) the propeller becomes freewheeling. Thus, if the airspeed remains high during the descent, the propeller can easily overspeed and shed a blade. "

Seriously I have to laugh. I have done many a power off decent to 100 IAS and never had the prop overspeed and spit itself apart.

I do not know what atmosphere you have over there but I can assure you who ever is writing this clap trap needs to get their hands dirty in the "real world" and learn something about mechanical 101.... Power pulses, torsional pulses, vibrations are all part of an engines combustion cycle. A clutch only freewheels up to a point, then the tons of centrifugal pressure the weights apply to the clutch friction make the "coupling" a DIRECT CONNECTION like it was not even there !!!. Putting a rubber isolator might help absorb some of these vibrations up to a point,...but that donut can fail and come apart. I have seen them fail from heat AND vibration. Esp on the ends of the automobile driveshafts they were ORIGINALLY installed on. But hey, your subaru engines must be running so rought and bad over there that you need this extra "engineering". to make your units survive.

The only engine that will eat most boxes is a rotary engine but that is a whole different animal.



Jonathan
 

1946

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Listen, .....that was a nice long winded article written by someone who has ZERO time with proof of concept under their arse. Sprags work, and they work well. They work with cars, trucks, aircraft etc.

I have been running a New Horizons gear box that uses a sprag for well over 200 hours. Runs great, smooth, powered by a worked subaru ej 22. or should I say carb fuel supply. Engine made close to 700 lbs of thrust on a heavy 2 place before it crumpled the nose wheel.

There are units in service well over 1000 hours.

What is the problem ?

Build it, see what it takes to blow it up. But please do not "borrow" someone elses homework.
I have seen in China some incredible dangerous homemade aircrafts, they fly too, but I don’t thing will take a ride on it, with that said, if your sprang clutch works well then you don’t have a problem, our problem is that we can’t take risks implementing industrial sprang clutches on our PSRU and, therefore we went with the flywheel integrated centrifugal clutch. If our clutch proves to be successful, we could offer the flywheel integrated centrifugal clutch to owners of the original box. It could be a win-win situation. Life is not a concept.

Thanks
Albert
 

Heron

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Automan
New Horizons, is that one of Larry´s?
thanks
Heron
I guess my application was rejected! :(
 

1946

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Looking good!
I am sending appication for a job with your company!
Heron
Applications taken only if you are over 70 and must come in company with both grandparents.

Thanks
Albert
 

1946

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Heron, are you not over 70, and your grandparents love to travel, I think you have a new job :)

I was made aware of this post by BoneyM, on HomeBuiltAirplanes.com

Re: PSRU
""""""""""""""""""""""""""""WARNING""""""""""""""" """"""""WARNING"""""""""""""WARNING""""""""""""""" """"""""""""""""
1946 or Albert has been stealing pictures from this forum and using them on RotaryWingForum, many of the pictures I have seen here are being used by Old Albert on that other forum as he is claiming they belong too him and that his company is building such items. """"""""WARNING""""" 1946 or Albert may just scam you out of your hard earned money, don't let him do it, Please go to Rotary Wing Forum and look up 1946 and or PSRU, there is a 20 page thread with old Albert claiming to be someone he is not !!!!

""""""""""""""""""""""""""""WARNING""""""""""""""" """"""""WARNING"""""""""""""WARNING""""""""""""""" """"""""""""""""


Tim Stevens , Hamilton, Ontario, Canada , Aka BoneyM122 and BoneyM, you are indeed a very troubled man, you constant hounding , untruths and derogatory posts her and on HomeBuiltAirplanes.com is an indications you certainly need some kind of help, with that said , I challenge you, here and now to prove your claims pictures posted by myself are stolen or otherwise. Since you won’t be able, is up to the members to make up their own minds about your claims and mental condition.

Thanks
Albert
 
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