E-Props ...who has first hand experience with these

[LoonyBob]

Under static conditions, propellors are running with a very high degree of recirculation, which remains significant up to 20~30kts foward speed (light aircraft). Recirculation gives a weird spanwise inflow velocity distribution on the blades, and so a weird lift (thrust) distribution - not very representative of flying conditions..

A look at fixed pitch props on TC'd aircraft (Cherokees, 172s etc) shows that a maximum static RPM of ~85% of full power RPM, will allow a healthy RoC, and WOT level flight without engine overspeeding; a 65% cruise of 1.5~1.6 Vs1 is typical, but 75% gives not much increase, as the prop is becoming depitched. This can be tweaked by adding a bit of pitch - a "cruise" prop - at the expense of a longer TOD.

Fitting a CS prop to such a beast will give markedly better TO performance, simply because the engine is allowed to develop near full power for the entire TO roll and initial climb. At the top end, the CS prop will not change the airframe's power needs, but should offer 5~8% better cruise.

Whilst Cherokee 172s are somewhat draggy, RAAus machines range from very draggy to very clean; however, a static WOT RPM of ~85% of full power RPM is a good starting point.

Note that most fixed pitch props for TC'd aircraft have "overtwisted" blades (twisted beyond optimal performance for the speed range in question), because (a) tradition [most propellor makers still don't use blade element theory!], and (b) it tends to meet the overspeeding requirements for certification without much difficulty.

Most (all?) composite RA blades are a tad undertwisted, which limits the propellor's efficient speed range.

 

In summary: a CS prop will yield near-optimal TO performance for any aircraft, though not much if Vs1 >= 30kts; and should give optimal cruise, but not huge increases, subject to blade twist. A VP prop is a step in the right direction.

The D18 gets a ground roll of ~110m, a healthy climb, and will cruise at Vno on a fixed pitch prop. The climb and fuel burn can be improved by drag reduction, and reducing the TO roll by ~15m is not worth the weight of a "live" prop...

[LoonyBob]

1 hour ago, skippydiesel said:

Hi Kyle,

 

Three questions:

• Is there a CS (Glorious) E-prop in Australia?
• Why have E-Prop opted for hydraulic pitch change, rather than one of the electric systems?
• Is there an In-Flight-Adjustable variant of the Glorious (or plans to offer one)?

Electric props tend to have slow actuation (the forces can be quite high), and I do know that an early version of a well-known German VP prop on a 503, used to "hunt" when using a CS controller, and sometimes allowed engine overspeed at the end of climbout. Hydraulic actuators give both more force & more damping...

[skippydiesel]

My limited experince is with the Airmaster electric system and way back when I was in GA, hydraulic .

 

So far (about 60 hrs) I can say the Airmaster is not at all slow to move between changes, seems to have no problem adjusting pitch, whatever the situation and neither hunts or allows overspeed.

 

The Airmaster can be used like a traditional CS, with the pilot controlling all pitch changes or in semi automatic ie preset Takeoff , Climb, Cruise.

 

[facthunter]

Adjusting the pitch stops is the only way to be safe with overspeeding.. Nev

[Blueadventures]

Fitted a 175 size 3 blade E-Props to a mates Vixxen A32.  The agent for foxbat is happy with them and said at least a 10 knot speed increase should be seen. The static is set at 5,410 rpm presently so will see what WOT S&L 2,500 feet gives and adjust accordingly.  The owner of the Bristelle at our airfield is totally happy with the E-Props he bought from Mark on the forum.

[BrendAn]

1 hour ago, Blueadventures said:

Fitted a 175 size 3 blade E-Props to a mates Vixxen A32.  The agent for foxbat is happy with them and said at least a 10 knot speed increase should be seen. The static is set at 5,410 rpm presently so will see what WOT S&L 2,500 feet gives and adjust accordingly.  The owner of the Bristelle at our airfield is totally happy with the E-Props he bought from Mark on the forum.

10 knots is a huge increase. What is it that makes e props perform so much better than other brands.

[facthunter]

The SALES Pitch??   Nev

[Blueadventures]

23 minutes ago, BrendAn said:

10 knots is a huge increase. What is it that makes e props perform so much better than other brands.

Best to read their webb site and Mark Kyles posts; from my experience like the company say set RPM for 5,500 at 2,500 ft straight and level and they are at their best, don't waste your time with any other setting.  I tried 5,800 after being at 5,480 rpm thinking that would be good, I instantly learnt that it's a no, no; could not even get to 100 kts.  Reset to 5,500 rpm and now 108 kts plus. I've fitted and adjusted 4 E-props now and many others and would not hesitate to recommend them over other brands around.

Edited May 8 by Blueadventures
spelling

[Blueadventures]

6 minutes ago, facthunter said:

The SALES Pitch??   Nev

Not really a sales pitch, more just stating what to expect speed wise compared to the original propeller sold on the aircraft.  They are sold with a guaranteed refund and like had been posted will loan a prop for a trial so you after fitting you either send prop back if unhappy or send payment; how many aviation or other products do that.  Best if any doubt track down an owner with one and seek answers about how they find them.  Thier a bit like when radial tyres overtook conventional tyres years back.

[Kyle Communications]

Eprops are designed from the ground up by very smart people versed in fluid dynamic and using some very trick software. They just dont copy and remix old designs. You have to remember that the Eprop for Rotax engines was specifically designed for the engine that has a gearbox. NOT a direct drive although later this year they will release their new prop for the Jabiru series of engines which is a 2 blade. You can of course get a 2 blade for a rotax but that is a waste because again it was designed for a gearbox engine. It also helps that it is the lightest propellor you can get with the latest materials. Everyone also notices the vast difference when starting and stopping the engine...no more big clunks..The blades are not wide like all other props..this reduces the drag of the propellor. One thing to remember of course is that reduced drag will affect your landing approach. Every single customer who has bought a Eprop from me has been super happy and every single one has had a dramatic increase in cruise speed. Also they all cant believe how smooth they are..they are a huge level above anything even with the best dynamic balance you can do on a normal prop. I have sold over 70 props now and in fact another 2 are on order this week. If you set them up as per the instructions they tell you then you will get the performance. If you listen to the "old guard" you will NOT get the performace. The designers know what they are doing.

One of the first few props I sold was for a A22 foxbat..he got 8kts increase in cruise..he used to love is Warp Drive props...he sold all 3 he had after using the Eprop. I dont want this to be taken as a sales pitch. It isnt. Its just information to chew on but the best recommendation is from the people that use them. I dont have to have any sales pitch..they sell themselves. 

[Area-51]

What does a blade replacement cost on these units?

[Kyle Communications]

I have never had to replace a blade only for anyone. Not sure on the freight cost but the blade themselves are AU$650 each. I would have to find out the freight.

 

Each part of a Eprop has a embeded chip in it with the parts specs recorded in it when its made. I will require the serial number of the broken part so they can make the replacement to the exact same specs. This is required for balancing of the prop to make sure the blade you require is the same weight.

[Area-51]

36 minutes ago, Kyle Communications said:

I have never had to replace a blade only for anyone. Not sure on the freight cost but the blade themselves are AU$650 each. I would have to find out the freight.

 

Each part of a Eprop has a embeded chip in it with the parts specs recorded in it when its made. I will require the serial number of the broken part so they can make the replacement to the exact same specs. This is required for balancing of the prop to make sure the blade you require is the same weight.

Thanks, just wanting to know for maintenance planning... Aware of the block chain micro chip feature; great idea...

[Blueadventures]

Some real life in service E-Prop experience just for info.  The prop I fitted to a Vixxen  A32 912ULS yesterday is achieving 5,400rpm S&L (This will be adjusted to get the 5,500 rpm in the near future)  The owner is happy and advises that at WOT at 5,400 = 127kts.

 

At 5,200 rpm his preferred cruise he now gets 122 kts (Was 108 kts with the Keiv propeller)  a 14 knot improvement and is totally happy with prop.

Edited May 9 by Blueadventures

[facthunter]

 Sales "pitch" was a play on words. Prop efficiency can be determined  in various ways and there have been plenty of them  of high efficiency  already produced perhaps not so much for what we fly . You can't invent thrust or get over 100% efficiency. Matching it to the Plane is always important. You can certainly play around a lot and get nowhere..  I'm not intending to bag this prop. I thought the Kiev prop was a great performer in a past experience  with a skyranger.  Nev

[Blueadventures]

1 minute ago, facthunter said:

 Sales "pitch" was a play on words. Prop efficiency can be determined  in various ways and there have been plenty of them  of high efficiency  already produced perhaps not so much for what we fly . You can't invent thrust or get over 100% efficiency. Matching it to the Plane is always important. You can certainly play around a lot and get nowhere..  I'm not intending to bag this prop. I thought the Kiev prop was a great performer in a past experience  with a skyranger.  Nev

All good, understand. Kiev are the preferred with Skyranger kits and UK builds historically.  I had a DUC first and very happy with it (my only dislike was the gold coloured anodised alloy boss that gets corrosion and needs attention otherwise the corrosion will get away) and now the E-prop which is the best by far.  Have experience with the heavy Fiti props would not buy one now, Bolly also on a Skyfox good prop and good service, similar to Kiev but in my description both are old style build materials.  DUC are good and a progression towards the lighter designs with better resins etc.  E-Prop are now the bench mark with their design and materials and now have many years in service and props in use plus 4,000 hours so one set should see out 2 Rotax engine lifes.

[Red]

On 09/05/2024 at 1:17 AM, Blueadventures said:

Some real life in service E-Prop experience just for info.  The prop I fitted to a Vixxen  A32 912ULS yesterday is achieving 5,400rpm S&L (This will be adjusted to get the 5,500 rpm in the near future)  The owner is happy and advises that at WOT at 5,400 = 127kts.

 

At 5,200 rpm his preferred cruise he now gets 122 kts (Was 108 kts with the Keiv propeller)  a 14 knot improvement and is totally happy with prop.

Importantly did he get that improvement in the airspeed/RPM ratio with no change in fuel consumption or throttle position?, without knowing that or having a manifold pressure reading for both setups it can't be taken at face value, you can of course change the airspeed/RPM relationship on any prop just by altering pitch but the engine load changes

Edited June 15 by Red

[AndysAtCoffs]

Hey Guys...Ive been off site for a long time.....but reading this thread I feel I can add to it in a hopefully positive way.

For a number of years Ive worked for a local contracting company that manages tree mulchers, those huge beasts that have a 1200Hp cummins KTA Diesel engine and a rotating drum with big teeth that would happily get rid of the average human in about 1.1Seconds.

Anyway, interesting thing is that those really big heavy drums with teeth all over them when they spin need to be balanced.... Any guesses as to what we use to balance them.... Yep a smart avioinics PB-4 prop balancer...the major difference is that the test weight can be up to 1Kg in weight......don't recall needing that much test weight on a prop but. I guess if your way out of balance.......

And the other major difference is that a drum is not really like a prop in that a prop is really considered to be a spinning disk which is in one plane.... A drum is just a really long shaft which is balanced as a 2 plane balance where weight added to one end obviously affects that end but also affects the other and vice versa. The smart avionics PB3 and PB4 balancer has a module added to it to allow 2 plane balancing.

Why is this all relevant here.... well you guys have been talking about extensions being used and props sitting on the end of teh extension. IMHO that turns a 1 plane balance using any prop balancer into a job that requires a 2 plane balancer. Is it possible to balance out all vibrations in a 2 plane shape with a 1 plane balance...Nope not at all possible!!!! I know cause I worked with the SmartAvionics guys to test the 2 plane balancing module which had never been used before. Up until I did that I tried for days to balance a drum with a single plane balancer. I could get one end perfect but the other end never could be perfected until we changed over to 2 plane.

So I'm guessing that you may solve the vibration issues if you balance the prop and the extension shaft using a 2 plane balancing method. This will result in correction weights being added to the prop and the end of the shaft that connects to teh engine. I don't know that as fact that this will solve it but it may be worth looking into....

Here's the manual from SmartAvionics that talks about the PB4-Balancer. Have a look at pages 57 through 61 especially teh diagrams showing situations where a 2 plane balance is required and see if in your mind it fits the scenario described? https://smartavionics.co.uk/pb4/pb4_ui_manual.pdf

Regards

Andy

[AndysAtCoffs]

Oh yeah should have added that there are some practical limitations as to how you would balance such a config. The accelerometer has to sense at the point where the extension is bolted to the gearbox/direct drive shaft and then at the opposite end of the shaft either at the front of the prop, or if it was a direct drive engine at the rear of the engine. If there is a reduction gearbox involved then the rear of the engine is not a viable measurement point. In such a case you may be better removing the extension and prop and balancing on a purpose built balancing rig..... that'll be cheap to create and be done in an afternoon....not!!

Also worth noting that you need to do dynamic balances at the rotational speed you intend for the device to work at....so a balancing rig will likely need the same input power as your engine is capable of producing but be direct drive and not through a gearbox...at least not where the accelerometer measurements are taken....

alternatively balance the prop extension on its own using a 2 plane balance at the cruise RPM you want and the prop separately and hope that mating them together maintains the extension shaft balance.

Ive done lots of 2 plane balances over the years, so much so that we provided balancing to other users of big rotating devices....There's defiantly science involved...lots...and to many mechanics and owners of machines it was all simply magic!!!! one day a machine might take 2 hours to balance...teh next day a similar machine might take a day and a half...... why??? magic!!! Edited December 11 by AndysAtCoffs

[facthunter]

Anything with length HAS to be dynamically balanced. The rotation rate used doesn't need to be high unless things are distorting massively. . Static balance is good enough for most U/L props. Balancing engine Gearbox Prop combos  all together is fraught with  hazards and complications. Nev

[AndysAtCoffs]

Nev, The Accelerometers included with these balancers are sensitive devices but in my experience work best when you are at or near to intended operating speeds. a tiny (barely evident) vibration at slow rotational speeds uncorrected can become teeth rattling at higher speeds. An accelerometer, that is fit for purpose, has no issues sensing "Teeth rattling"  but may well struggle with slow and barely evident vibes at low speed. In my limited prop balancing experience, you want to dynamically balance at the speeds your going to have your props spend most of their time at.

 

Also while defining job realities... A dynamic balance can imho absolutely fix vibration at any one speed...it may, however despite being smooth as silk at that one speed  be a complete disaster at another speed if you haven't first statically balanced. So when you intend to dynamically balance always statically balance first. Manuals on prop balancers cover this in detail...usually

 

Andy

Edited December 11 by AndysAtCoffs

[facthunter]

Been balancing stuff for more than 50years Andy. Balance is done for many reasons including internal loads. If you balance each  part you do a better job and can inter change parts quickly. Static balance is only suitable where the object has minimal length.  Reduction gearing introduces   issues direct drive doesn't have.    External overall smoothness doesn't mean all is well in there.   Counterweight extra shaft rotating engines have Higher bearing loads as the factor is higher, .  Weight prohibits their use in aircraft engines  (and they are a silly idea anyhow). Cranks in aero engines are as light as possible  and don't have the balance weight cars etc do (Excepting  Radials) where they are massive with say Nine  reciprocating bits hanging off One crankpin. to oppose.. There's also "Torsional " vibrations which you can't feel, that can be destructive at critical RPM's. and put great loads on the reduction gears  and crankshaft. Nev

[RFguy]

It's an interesting engineering problem, to put in in tech terms, in most applications, the internal state is much larger (has more degrees of freedom) than the few observable parameters which are measured (by the accelerometer). 

[facthunter]

A "FIX" at the delivery end May Mask an emerging problem inside also. Any change in engine vibration should be taken as a warning.. SOMETHING is NOT right.  You don't just wait till it blows up. Some Jet engines have vibration meters  for that reason. Nev

[AndysAtCoffs]

the other issue with an extension shaft is that generally, in the ones I've seen, there are 2 flat plates that are bolted together with the engine/gearbox output flange with 6-8 bolts around the circumference, and the prop at the other end. They are supposed to be made so that the plate on the engine end, and the other are at a perfect 90 degrees to the shaft (and so perfectly in parallel to each other so that when everything is bolted up and you look for run out by spinning the gearbox/engine and measure at the haft as far away from the engine/gearbox as possible you don't see any/very little  which means the surface was at that exact 90 angle all around. If there is any introduced runout because of a manufacturing defect or the uneven bolt tensions have pulled the shaft away from its center position then no matter how good the static balance the shaft at speed will introduce a vibration because its center of mass is no longer in line with the output shaft of the gearbox/engine. If the runout cant be Zero'd with bolt tension variations/adjustments, then a dynamic balance can help counter the vibration but to me that's a bit lipstick on a pig..... swap out the pig....

 

At least thats what Id do....YMMV