Interesting experiment with props and thrust testing

[GyroDoug]

so when I get my Sport Pilot CFI this winter, my gyro will have the power to train heavier students with power in reserve if needed.

Ron,

I am excited to hear that you are planning to get your CFI and do training in an open air tandem CLT Gyro. We seem to have lots of CFIs that will train in a side by side enclosed machine but for the guy who plans to fly a single open frame machine there aren't near as many options. I am sure you will make a great CFI and I wish you all the best with your endeavor. (I just wish you lived closer to the west)

Gyro Doug

 

[GyroRon]

Well I am going to try to get the rating. I think I have most of what I need to get it, but I need to learn how to train and get with some of the better instructors out there and see what kind of program they use to teach students. Stay tuned....


Tim, I checked it, it still works!

 

[birdy]

This time there might have been a ever so slight increase in power, almost unnoticable really and I can only think the cooler less humid air had something to do with that. I might have had 50 more engine rpms on average than the weekend before

Ron, the general ruel with DA V performance is, the thicker the air [ cool n dry] the LESS erpm youll get over thiner air.

We can get big DA variations here in less than 3 hours.
Sunrise on a cool winter morning will always have less erpm than 3 hours later wen the air warms up. Sumtimes up to 200+ erpm less.
The Engine will be breathn thicker air too, improveing power, but the increase in drag on the prop overrides any benifit in power.

 

[Aviomania]

Ron,
I am Glad that there is nothing wrong with your engine, and that the problem was due to aerodynamics of the prop.

I agree with you that warpdrive props are very good because they can take a lot of punishment. The only downside is that the weight and the gyroscopic effects are more than other props.

BUT.......... as i explained the aerodynamics involved in the original post https://www.rotaryforum.com/forum/showthread.php?t=17836&page=2 post #22 the static thrust results are a bit misleading.

WHY?....

As i mentioned before sport and Kiev props have much grater twist on the blade than warpdrive. this causes the inner part of the blade to be at grate AOA, therefore stalling at static RPMS, leaving only about 2/3 of the outboard blade producing thrust.. which is the most effective by the way. That is also the reason why the increase of thrust vs RPMS is not so grate on the sportprop.

The Warpdrive on the other hand has ALL the blade working because the twist is not grate. That is why you got better static thrust with warpdrive.

Bat what happens as the airspeed increases????

when the propeller is spinning, the airflow at static rpms meet the blades at 90* to the direction of rotation. the difference between root and tip of the propeller is the airspeed... slow at the root, fast at the tip.
As the forward airspeed of the aircraft increases the airflow at the blades start to change direction therefore meeting the blade at LESS AOA. at the root of the blades the AOA changes more than at the tips as the forward speed increases.

NOW.... here is where the difference of sport/Kiev prop is, compared to the warpdrive.

That grater twist which has the blades staled at the root, now that the airspeed is increasing the root starts to work, giving you GRATER thrust at higher speeds ( or at least reduces at much lesser rate). On the other hand warpdrive's thrust reduces as airspeed increases. SEE DIAGRAM.

so... although warpdrive has grater static thrust at, lets say 50 mph sport/Kiev props have more thrust.

Next time you will fly with the warpdrive you will notice (maybe) less top speed.. but for sure less climb performance at higher speeds, as well as more gyroscopic ( & inertia) effects... Let me know.

Personally, i like warpdrive when i fly from rough Fields, & Kiev for performance.

Kiev has some more aerodynamic improvements than warpdrive as well.

I hope i explained it as clear as posible.... English is not my first language

P.S.

Good luck with your CFI rating !!!!!!

 

[XXavier]

Very interesting post... Thanks. I once had (in a pusher FW) a three-blade WD. Heavy, but indestructible...

I'll print your post right now, for later study...

Regards

Xavier

 

[scottessex]

Yes, I am happy it isn't the engine that caused the loss of rpms. Of course it might not matter much soon anyway as I am in talks with someone to help me put together a 120-150 hp engine to put on her so when I get my Sport Pilot CFI this winter, my gyro will have the power to train heavier students with power in reserve if needed.

Are you going to pull the engine off your Titan?

 

[GyroRon]

Nicolas, I agree with your post. The only thing I am not sure I agree 100 percent with is how much of a performance difference in flight the warp drive will have over the Kiev. My Warp drive has quite a bit of twist, to me it looked to be nearly as much twist as the Kiev. I flew my gyro with the Warp drive after the thrust test and I honestly could not tell the gyro was any different than it was a few weeks ago when I was flying the Kiev. Of course my gyro tops out at only about 80-85 mph, the engine is over reved at that point with all 3 props that have been on it. I like the Kiev, but I believe it is easily damaged, the bolt that went through it and caused the damage was small, it would not have hurt the warp drive.


Scott, my plane only has 80 hp....

 

[Skyjinks]

As some of you may be aware from this thread https://www.rotaryforum.com/forum/showthread.php?t=17836

All my thrust tests have had a simular result and that is when the pull first starts the rpms peak out and you get the highest rpms and highest thrust, but within a few seconds the rpms start to drop off a little and thrust drops off a little as well. I can only guess that this is due to the heat building up in the engine and a reduction of power

I think the loss of thrust after initial power up is more likely due to vortex ring than engine heat. We used to manufacture big industrial fans and when we tested if the vortex breaker was left off, the same charachteristics as Ron describes occured. Same as a Heli rotor too in vortex ring effect so if the gyro was moving forward at anything more than a few miles an hour rather than static this loss of performance would not occur

 

[Russ]

Warp vs Sport Prop

Warp vs Sport Prop

I compared a 68" Warp Drive to a 68" Sport Prop on my 618 Dominator and found that climb rates and top speeds were near identical. The Sport Prop was much quicker to react to throttle changes though. The Warp was way stronger.

 

[Aviomania]

Nicolas, I agree with your post. The only thing I am not sure I agree 100 percent with is how much of a performance difference in flight the warp drive will have over the Kiev. My Warp drive has quite a bit of twist, to me it looked to be nearly as much twist as the Kiev. I flew my gyro with the Warp drive after the thrust test and I honestly could not tell the gyro was any different than it was a few weeks ago when I was flying the Kiev. Of course my gyro tops out at only about 80-85 mph, the engine is over reved at that point with all 3 props that have been on it. I like the Kiev, but I believe it is easily damaged, the bolt that went through it and caused the damage was small, it would not have hurt the warp drive.


Scott, my plane only has 80 hp....

My experience with kiev prop is that it performed better than warpdrive. Granted it was on a FW. Gyros are more draggy so changes will not be so noticeable.

I have a 72" warpdrive on my 2 seater ( i also prefer warpdrives on pusher aircraft just because they are strong). I also have 72 inch powerfin and 72 inch Kiev prop. When i get the time i will make some tests on my gyro (with 105 hp engine) and check the deference in performance (with instruments) and let you know.

Ron.. If you can, please give me the details on the following so i can check something.

Static RPM, in flight rpm, reduction ratio and prop diameter.

 

[automan1223]

Listening to the Experienced Timers....

Listening to the Experienced Timers....

I was told by several high time builders you cannot beat a Warp Drive on a gyro.

I think Ron is discovering why that is.

No prop is 100% bullet proof but it comes close.

I know I an happy with my prop and it has some hits from grass field and gravel farm road operations.

Jonathan

 

[GyroRon]

Nicolas Static rpm is 6800-7000 depending on how cold the engine is - the hotter it is the slower the rpms. In flight, well at full throttle in straight and level? I am not sure, over 7000 rpms. Gear ratio is 3 to 1 , prop is 70.5 inches in diameter

 

[Aviomania]

Nicolas Static rpm is 6800-7000 depending on how cold the engine is - the hotter it is the slower the rpms. In flight, well at full throttle in straight and level? I am not sure, over 7000 rpms. Gear ratio is 3 to 1 , prop is 70.5 inches in diameter

Ron, the reasons you did not NOTICE difference between the props are, first, gyros are not the most efficient flying machines so a little deference is not easily noticeable and second you are turning the props at lower RPMS.

if you allow your engine to rev at 7200-7300 rpm at cruise, the tip speed of your prop is around 740 f/s. The maximum POTENTIAL of your prop will be reached if your tip speed is around 835 f/s ( 8200 engine RPM in your case).

THE DEFERENCE of the kiev/sport prop is that there aerodynamic design is more efficient at high tip speeds than other props.

In your case if you had a smaller reduction ratio you COULD notice a difference between the props IF YOUR engine could spin the prop at tip speeds of ~830 f/s WITH A PITCH that will result to the same gyro's top speed. Most probably you will need more HP for a 70.5 in prop.

selecting the best prop / reduction ratios for an engine / airframe combination, can be calculated in theory but it will take testing in real life to fine tune it.

OK.... OK..... this is important for the boys with high performance aircraft that are involved in racing, aerobatics or record seting..... not for the recreational gyro pilot.