Prop Selection

[skippydiesel]

1 hour ago, Kyle Communications said:

 

 

The big issue with the CS unit is the hardware design of the prop hub...sounds easy but not so much at all. The forces and stresses to make stuff move at 2300rpm and multiple blades...yeah..better engineers than me do that stuff. I know my limitations 🙂

 

Don't under rate yourself - Rather than try to develop an IFA hub and blade set up - why not purchase a good system "off the shelf". Then use your off the shelf black box, your favorite linear actuator, some bits from JayCar (or similar), a bit of machining and we are in business.

[OZJohn]

Servo for CS.pdf I have been using CS propeller on Rotax for the last 8 years. Very satisfied with the result. Maintains propeller speed within 100 revs over the range of 4800 to 5500 engine revs.

Operated by pushrod by servo motor mounted on top of gearbox. Push for coarse, spring loaded for fine just in case anything goes wrong. Moves blades through a 10 degree range.

Can also be used as fixed in flight adjustable by the flick of a switch if required for training.

If you require any further info PM me. John.

[RFguy]

ok , it has a linear actuator . (servo motor may be inside the mechanism, could also be a continuous motor)

[Kyle Communications]

What sort of dollars?...never heard of them

 

[Blueadventures]

1 hour ago, OZJohn said:

Servo for CS.pdf I have been using CS propeller on Rotax for the last 8 years. Very satisfied with the result. Maintains propeller speed within 100 revs over the range of 4800 to 5500 engine revs.

Operated by pushrod by servo motor mounted on top of gearbox. Push for coarse, spring loaded for fine just in case anything goes wrong. Moves blades through a 10 degree range.

Can also be used as fixed in flight adjustable by the flick of a switch if required for training.

If you require any further info PM me. John.

Could you post some images on the parts as it sounds good and interesting.  Thanks.

 

[skippydiesel]

So

1 hour ago, OZJohn said:

Servo for CS.pdf I have been using CS propeller on Rotax for the last 8 years. Very satisfied with the result. Maintains propeller speed within 100 revs over the range of 4800 to 5500 engine revs.

Operated by pushrod by servo motor mounted on top of gearbox. Push for coarse, spring loaded for fine just in case anything goes wrong. Moves blades through a 10 degree range.

Can also be used as fixed in flight adjustable by the flick of a switch if required for training.

If you require any further info PM me. John.

Veeery Interesting OZ John - Another Czech aircraft company (how many are there). On face value it would seem to adhere to the KISS principal. Pretty much what we have been discussing of late (me thinks they have stolen our concepts ha ha).

 

One thing I dont understand is why they opted to place the servo on top of the gear box - yes I can se the lever effect but must play havoc with the ability to present a small engine cowling profile.  this is where either a step/linear drive could be brought to bear.

 

I would also ask for a heap of additional information:

 

Aircraft performance from TO role , climb to cruise with RPM & if possible, fuel consumption for each phase. If the latter a problem perhaps your trip planed fuel consumption.

 

Cost delivered to AU if you have it

 

Photos of your installation (with & without spinner)

[Wirraway]

Apologies, but I haven't read all 7 pages of this thread. My bad, I know.

 

However, just thought I would share something that may not have been brought up here.

 

On the FB page Recreational Aviation Australia Discussion (RAAus/RAA)

a poster talks of putting the Airmaster CS prop on his Brumby 610. Weight of 11.8 kg, but he is yet to do a W & B calc.

914hp Rotax, and will instal floats. CSU allows for Beta, apparently handy with floats. FYI

Edited November 3, 2020 by Wirraway

[skippydiesel]

Thanks Wiraway - Yep! the CS can have (Beta needs to be specified/ not automatic) other talents beside maximising available thrust at different stages of flight.

 

As for the weight - the Airmaster CS that would suit me is 9.1kg, about 5.5 kg heavier than my current ground adjustable.

 

My battery, mounted on the firewall,  is 6.6 kg and may be the best relocatable (with appropriate cable upgrade) ballast that I have (other than adding lead to the tail somehow) to minimise/negate the balance equation without loosing more "pay load".

[skippydiesel]

Mhalc - Sorry mate - Got your e-mail contact but being an old fart cant seem to find out how to return comment.

 

Only 4% improvement in cruise and a deterioration in ground role/TO - that would concern me greatly.

[skippydiesel]

MT - Propeller update;

 

After an initial cryptic, 2 prop recommendation, they have got back to me with a little more detail (still not enough) &  3 prop recommendation

 

MTV-1 is a 2-bladed electric constant speed propeller, approx. 10,5 kg

MTV-34, 3-bladed hydraulic constant speed propeller, approx. 10,5 kg

MTV-33, is a 2-bladed hydraulic constant speed propeller, 6,5 kg

We prefer MTV-34 for your application.

Following  find a link to our homepage for more details: https://www.mt-propeller.com/en/entw/pro_hydr.htm

 

I asked for the reasons /rational for their recommendations but so far nothing .

 

I provided  a detailed breakdown of my aircrafts performance, with existing ground adjustable Fiti propeller, and  asked for their estimated changes to this - so far nothing.

 

I have tried to make sense of the technical details (above web site) they have provided, without any joy.

 

My inclination is to focus on 2 blade props as, in general , they seem to offer:

• Lighter installed weight - less impact on W&B so preserving most of my pay load with only a small adjustment for balance.
• Slightly faster (than 3 blade) cruise - this is  my objective
• Similar TO performance - again meets my goals
• Slightly less cost  (than 3 blade) - always a good thing
• Less maintenance - perhaps

 

The only down side may be a bit more cabin noise (than 3 blade) but as I have never experienced a 3 blade and my aircraft is already supper quiet. this seem to be a bit of a subjective/ephemeral benefit - may apply more to metal fuselage types. 

[skippydiesel]

Further correspondence from MT-Propeller:

 

Not sure if the % shown below are in relation to my existing Fiti ground adjustable ( I gave them my current performance figures) or relate to the 3 propellers recommended - I suspect the latter.

 

"following please find pro and contra arguments for each propeller:

MTV-33: lowest weight, good overhaul performer

MTV-34: slightly heavier, better take of by 5 %, better climb by 3 %, same cruise

MTV-1: performing like MTV-34 and electric"

 

Interesting that the only performance improvements would seem to be in TO/Climb and relate to acceleration (5%) which is to be expected with a multi blade prop.

 

"We would prefer hydraulic propeller because of cheaper price and 6 times faster pitch."

 

My read on the above -  pitch change speed my have been an issue with the erly electric CS props and current offerings may still be a bit slower than hydraulic but is this really a consideration in normal flight (as apposed to aerobatics). Price is always a consideration but MT have pretty much priced (their electric offering) themselves out of the market

 

Below is their recommendation regarding Rotax 9 series engines for their props

 

ULS 2 engine is for electric, fixed pitch or ground adjustable propeller

ULS 3 engine is for hydraulic constant speed propeller.