Thrust Test Results

[scottessex]

Well finally, The weather was right, about 60 degrees, I had to burn a day of vacation, my good buddy Phil (R) was able to play hooky from work, we had a day of making noise and writing down numbers. some very surprising results.
I would like to thank Tim Chick for the use of his freshly rebuilt 503 as test mule.
Props tested ranged from 52" to 70" and yielded interesting results.

52" Ivo pitch 17* rpm 6500 Thrust 270lb
55" Warp pitch 11* rpm 6500 Thrust 291lb
60" Warp pitch 9* rpm 6800 Thrust 322lb
60" Ivo pitch 9* rpm 6800 Thrust 330lb
70" PwrFin Pitch 3* rpm 6500 thrust 350lb

we also ran the 60" ivo with a little more pitch 11* to bring down the rpm to 6500 and ended up with 315lb thrust.

Then just to see I hooked up the dominator with the 582 and 4 blade ivo, I have the prop pitched to where it flys the best, I can throttle back to about 5500 rpm and still cruise about 65mph BUT that does not yield the best static thrust as I can only hit about 6200 rpm on the ground.

582 ivo 4 blade 13*pitch rpm 6170 315lb thrust

pulled 315lb. This was very surprising, but it just goes to show you that static thrust is not a end all beat all wat to measure thrust.
The 52" ivo I am sure would pick up and become alot more efficient as airspeed increases. on the other hand the 70" prop moved alot of air, but at 3* pitch, after about 30mph it would act like a parachute, well maybe not that bad but it sure wouldn't gain much speed.

So there you go take it for what it is worth,
I am still going to change the gears in the gearbox to the 2.0 to 1 and re run the 52"ivo.
So here are your numbers. enjoy. :)

[Ron E]

Scott,

Where on the prop blade did you measure the pitch? Tips? 75% prop radius?

I will soon be offering a 2-blade non-electric in-flight adjustable prop with (up to 72" diameter) Warp Drive blades that can be used with Rotax C and E gearboxes for 2-strokes and for the 80 HP Rotax 912. This would make more HP available for prerotation on gyros. I will have a selling price determined in a few days.

[scottessex]

Ron, we just used a WarpDrive protractor at the tips, about 1" in from the tip, I do understand that that is not actual inches of pitch as if the prop was screwed into a solid block of butter for one revolution. :) just to get a measurement that was consistent throughout the tests.
Same with the scale, it is not "calibrated" or certified, but we used the same scale on all the tests.

[Dean_Dolph]

Scott, I would like to commend you on your test and particulary on how you hooked up the scale. Intentional or not it demonstrates a very safe way to do it. If anything on the scale hookup let go then the chain limited how far the machine would move.

[Fl90]

Cool Scott, thanks for your time and effort. I will await your results with the 2.0 set.

Phil.

[gyro]

thanks Scott, I'm running a 60"WD with 9*pitch

I was wondering what the thrust was, now I know....I feel good about me Ol 503.

[Fl90]

Helava prerotator drum in those pics. Is Tim going for jump take off capability?

Phil

[greg spicola]

Good job Scott!:first:
And every mad scientist needs a good assistant (Phil)

Greg

[Phil_Ruffin]

Good job Scott!:first:
And every mad scientist needs a good assistant (Phil)

Greg

OR.... every Good Scientist needs a MAD Assistant!!! :drum:

[scottessex]

Hey, it's the least I can do for the gyro community. :)

[Timchick]

Helava prerotator drum in those pics. Is Tim going for jump take off capability?

Phil

My FW UL friend flies his UL like a bush pilot. I'll need all the help I can get to get out of the places he gets us into. :p

Scott,
Thanks for taking the time to do all that. It'll be interesting to see what the other gears do.

[Timchick]

Phil could've put some t-shirts behind the prop and then sprinkled some paint into the airflow to create some custom t-shirts. :)

[Phil_Ruffin]

Phil could've put some t-shirts behind the prop and then sprinkled some paint into the airflow to create some custom t-shirts. :)

Yeah, we should have done that! Not sure if Scott would want a custom paint job on the front of his truck though..

[Papa Smurf]

Good test. Good clear easy to read post. Thank you!

[scottessex]

Uh yeah the truck could use a new look.

No problem Tim, Thanks for the "test mule" and Thanks Phil R for the help.
I think that the 2-1 gears will work out on the short prop
That way we can take some pitch out of it.

Very interesting results.

[Fl90]

I'm hoping for 310 or so from the 55" WD with the 2.0's. However, after a recent discussion with someone that has done a similar change, the reduced pitch and torque roll may be the only benefit. So, I'll wait on the edge of my seat.

Thanks, again. Phil.

[GyroRon]

I am trying to see what was interesting about the results. It seems to me to go along with what has been a given all along, that the bigger the prop and more thrust you get.

I agree that the biggest prop with hardly any pitch would run out of steam as soon as you picked up any airspeed, and I also agree that the props with alot of pitch would probably pull harder as airspeed increases and the props with less pitch would pull less as airspeed increases. My guess is the 60 inch prop is the best choice. The smaller props do seem to have done pretty good, and if the gyro was streamlined and you wanted to fly fast, they would probably push you along pretty good as high airspeeds, especially the little Ivo.

I wish there was a way to try to replicate airspeed while doing the thrust test. It would probably take more people to do it, but perhaps another gyro in front of the test stand, running at high power setting, the prop blast from #1 gyro might replicate airspeed for the 2nd gyro that has the scale hooked up to it.

Why didn't you pitch the smaller props to also run 6800 rpms?

Next time you do this, it would be interesting to try to do all tests at the same rpms, and then perhaps two different rpms per prop, say 6500 and then 6800. I have found that with some engines you get more static thrust at 6350-6500 rpms than at max redline of 6800.

[scottessex]

I agree Ron, I we had more time it would have been interesting to try different rpms, As you know when Rick Martin was at our fly in we re pitched his gyrobee added more pitch, slowed the engine down some, but it flew a whole lot better.
Same with my dominator, if I pitch it for max rpm on the ground it fly's like a dog, with a little more pitch I only see 6200 rpm on takeoff, but the cruise performance is so much better. But the static thrust was only 315lb, but at ROC 2 years ago it pulled 340-350.
It does seem that 60" is about the optimum size, but the 2 small props did better than I thought.

[GyroRon]

Different scales, different temps and locations, different fuel, etc.... all will give different numbers. I have seen the same 582 powered Dominator - my old white one - have pulls from 325 lbs up to 370 lbs. Nothing on the machine was changed, just the fuel, location and scale used.

Having various props tested on one engine with the same location, fuel, and scale is a great service though, and yes the smaller props did better than expected.

Of course something to consider, a popular size prop for direct drive Subaru, VW and even Macs ( I think ) is a 52 inch by 26 inch prop. I know from first hand experience that a EA-81 Soob, and a 1835 VW, and a 90 super Mac, all pull around 300 lbs with the 52 inch prop. These engines, at the rpms they run direct drive on gyros, are making simular power to a Rotax 503, around 50 or so ponys

[scottessex]

I got the gears changed :) Just a little while till we do another test.....Hey Phil (R) ya busy?

[Fl90]

The bigger props run a higher tip speed, so they will pull more. I agree, there's also more area on the large prop, so the air has to be accelerated less. But, if the little prop gains 10% with the 2.0s, I think the smaller airframe equals out the combo, as a smaller, less weight and less drag machine can be built around it. So, I'll wait and see.


Phil

[gyromike]

Scott,

Sticking a pitot tube into the propwash may also give you an idea of what sort of top speed you'll get out of different props, pitches and gear ratios.

My propwash is ~100mph, and I top out at about 85-90.

[Timchick]

The benefit of using a smaller prop is not having to change the airframe when converting over to the Rotax. If I went with a 60" prop I'd have to do a drop keel mod, taller mast, etc. I'd like to change out the engine without making any major mods and then fly it while I build something else.

[Phil_Ruffin]

I got the gears changed :) Just a little while till we do another test.....Hey Phil (R) ya busy?

I'm busy through lunch Thurs. but can come most anytime after that.

I am still trying to get that fellow we talked about yesterday down to McGowan land for a demo flight sometime this weekend (Friday or Sat.) But want know which day we're going until tomorrow.

Shoot me a PM or call.

[Brent_Brown]

I think 6500 on the ground is to high. 6800 is to high on the ground. At that ground RPM you have to back off the power as soon as you take off or you will go over the red line. I try to sset it up so I can fly without worrying about red line.

If you look back at my NZ 202 that had a 73" powerfin pulled 340 pounds with the RPM at 5500 WOT on the grond with a 2.88 to gear. I think it was 9* at the tip.

my 670 with a 3.47 to 1 E box and a 75" powerfin is set to load the engine at 6000 the the ground. I will see what the settings is, not sure right now. The prop is stalled on the ground at 6000, but after I get up to takeoff speed 40 MPH she spinns up fast and can hit 7000 rpm if you hold it full power. I had it up to 80 mph but I fly it at 50 mph most of the time. So far I am happy with this set up. Not sure what the thrust is but I would think it is higher than any 618 is pulling.

[Timchick]

After some discussion with Scott we decided to trim the 55" WD prop to 52", the largest allowable prop I can use without modifying my gyro mast height. He changed the gearbox gears to 2:1 and we did a thrust test today when I was picking up the engine. I don't know how many degrees he set the 52" WD to but it pulled 270 at 6250 rpms. I plan on trying this setup on my KB-2 first to see how it does. Even though the WD prop pulled more at 55" I would've had to change my mast to use it. If I have to change the mast I'll go up to a 60" prop. I brought Scott's scale home with me to check the thrust on my 72 hp Mac using the same scale before I remove it.

[CLS447]

This is great stuff ,guys ! Keep up the good work !

[Fl90]

Cool, Tim.

I'd like to see you fly it short.

Phil.

[scottessex]

I put the Suzuki on the stand, still have to hook it up, but we'll do some numbers on the snowmobile engine!

[Timchick]

Scott can correct me if I'm remembering wrong but I believe he said he couldn't get enough pitch out of the 52" Ivo with the 2:1 gears. It's an older Ivo that uses pitch wedges.

[giro5]

Tim, I am curious what you pull with the Mac. On mine using a bathroom scale in front of the keel up against a brick wall my 72 mac with a 48 x 24 Tennessee prop only pushed 185 lbs if my memory is correct at 4000 rpm (WOT) elevation 5500 ft.

[Phil_Ruffin]

After some discussion with Scott we decided to trim the 55" WD prop to 52", the largest allowable prop I can use without modifying my gyro mast height. He changed the gearbox gears to 2:1 and we did a thrust test today when I was picking up the engine. I don't know how many degrees he set the 52" WD to but it pulled 270 at 6250 rpms. I plan on trying this setup on my KB-2 first to see how it does. Even though the WD prop pulled more at 55" I would've had to change my mast to use it. If I have to change the mast I'll go up to a 60" prop. I brought Scott's scale home with me to check the thrust on my 72 hp Mac using the same scale before I remove it.

Yeah,,, I see how it is. You come within a few miles of my house and not so much as a Hey! :noidea:

Now that I think about it I'm sure I was way too busy to come over! :D :focus:

[Timchick]

Tim, I am curious what you pull with the Mac. On mine using a bathroom scale in front of the keel up against a brick wall my 72 mac with a 48 x 24 Tennessee prop only pushed 185 lbs if my memory is correct at 4000 rpm (WOT) elevation 5500 ft.

Based on the data of other Macs I expect my Mac to pull somewhere around 290+ lbs.

Phil,
Sorry I didn't give you a heads up. I wasn't sure how close you were to Scott.

[Timchick]

I went out to the airfield today with a future gyro pilot. George Spicer drove down from Enterprise, AL to check out my gyro. I flew the pattern a few times so he could see it fly and then I set up the scales to do a thrust test on my Mac. Some of the FW guys wanted to check their pulling power so we hooked up a Gull with an HKS and then a Hurricane with a 503 to see what they'd pull.

My Mac with a 46x30 Troyer prop pulled 270 lbs. I expected it to pull a little more than that. Since my 503 with the WD prop also pulled 270 lbs I'm really excited about getting it on the gyro.

The Gull with the HKS has a 72" Kiev prop and it pulled 260 lbs. Don't know what his pitch setting is.

The Hurricane has a 503 with a 66" Ivo prop and it pulled 245 lbs. Don't know what his pitch setting is either.

[gyromike]

Tim,

I didn't know you were swinging such a small prop on your Mac.
We would always run a Tennessee Prop 52x24 on the 72 Macs, and 52x26 on the 90's.

I pulled 300 lbs. with mine @ 3300 - 3400 RPM static. I get about 36-3700 max RPM in flight.

Never thrust tested a 72 Mac.

How much pitch was in the Warp prop?
If it's a bunch the prop may be cavitiating some.

[Timchick]

Scott thinks the 52" WD prop has 10 degrees of pitch. The gearbox has 2:1 gears.

[NoWingsAttached]

I have really got to get down to brass tacks, and test my set up on the bee. THis thing has a 6250cc Hirth, and the tach says 6000 rpms max throttle THe Ivo prop measures 31" from ctr to tip, so is that really a 62" ?? Sure measures like it. The thing runs better with more pitch, less eng rpm. When I de-pitch to get 6400 rpm it barely takes off. I gotta get a hand-held tach to verify the panel tach. It MUST be wrong. THis thing does NOT feel like 62 HP at 500 lbs. IT feels like 45-50. IT flies great at 52-5400 rpm

[NoWingsAttached]

OK, I spent a LONG time today testing Ivo prop pitch and engine revs and thrust. Here's what I found out. I used a certified dynomometer, not a big fish scale or some bathroom scales. THis is a very expensive precision instrument, with a variation of accuracy of less than 1%, and readable accuracy of 10 ft lbs. So, at around 300 ft lbs, the gauranteed accuracy is +/- 3%.

Guess what? I found that I could get readings ranging from 285 FP to 350FPm using the SAME prop pitch!!!!!! depending on how the test was conducted. SOOOOOO, you guys REALLY need to do your homework to get REPEATABLE test results. Your tests are pretty much garbage, unless you can show that your tests are conducted through a FULL range of engine RPMs, and FULL range of prop pitch, and each test must be conducted AT LEAST 3x to prove reliability of stated results.

1. Wind MUST be dead calm. Even a 1-5 MPH incidental wind will skew the test results beyond acceptable variation limits.

2. Pitch tests must be incremental in 1-degree pitch variations, from minimum to maximum pitch, typically 8 - 13 degrees. This will yield a CURVE, so that one result has a predictable variation from the previous and following data points.

3. Engine RPMs must be recorded at each 1* pitch variation.

4. Test results of each pitch test must be repeatable. You must have a minimum of 3 readings within 1% variation of each other at each pitch setting for acceptance.

5. Engine run-up must be exactly the same for each test. Example: 4000 rpms for 4 seconds, 5000 rpms for 4 seconds, 1000 rpm increases at the rate of 1000 rpm each 3 seconds to maximum RPM.

6. Each of the above steps is crucial, and variation from the outline is unacceptable.

7. If you are doing a single pitch test, and comparing results to another type of prop, then you must have a proper engine run-up that is comparable and repeatable at least 3x within 1%.

8. Any adjustable-pitch prop must be tested throughout the entire pitch and maximum RPM range, not just single or double comparable pitches. This is due to overall average pitch variations of the different designs. Tip pitch + engine RPM is NOT acceptable as a measurement of average pitch and comparable engine RPM. THis is a misconception of available thrust.

9. Test results MUST state an error efficiancy. There is no such thing as a scientific test with no error range. Typically a scientific test is acceptable within a range of +/- 5%. THerefore, a test that shows 300 ft Lbs thrust will have an error of 15 ft pounds. A test that compares one blade at 300 ft lbs and another at 270 will therefore mean that the blades are scientifically comparable, within the extremes of range of test error. Example: My test is guaranteed 3%, well below the acceptable standards. So at 300ft lbs, my test is acceptable from 291 to 309 FP.

[Timchick]

...... Your tests are pretty much garbage, unless you can show that your tests are conducted through a FULL range of engine RPMs, and FULL range of prop pitch, and each test must be conducted AT LEAST 3x to prove reliability of stated results.
........


Who made you the pull test authority? :puke: We were comparing different props on the same engine (except for the FW guys) to see which prop did better. The measurement on the scale may not be exact but it's good enough to see which prop pulls more than the other.

Now go over to Jake's thread on rotors and tell him how unscientific his results are.

[gyromike]

(snip a lot of bull****...)


So is it a 1% margin of error, or 3%?
And are you measuring in foot-pounds, or pounds?
Torque or thrust?

And what is this "readable accuracy of 10 ft lbs"? That's far from being a precision instrument.

:rolleyes:

[scottessex]

What good is a test at 4000 rpm? The purpose of setting the pitch on the prop is to limit the RPM of the engine, or LOAD the engine, Then it is a good idea to get the carbs jetted correctly to that power setting,
Besides, static thrust tests don't mean squat anyhow, as far as flight performance, it is kind of like a tractor pull, just a reference, My gyro has pulled 350lbs static, but I have the prop pitched so it makes 320 on the ground, @6200RPM, of course in flight I will see 6500RPM, and it would obviously be making more thrust at a higher RPM, along with actual movement throught the air, you can get more static thrust onthe ground, but it won't mean Jack in the air.

Did you record the temperature and barometric readings, for your scientific test?

So before you call us a bunch of idiots, the comparison was for different sized props on the same engine, on the same day, If I was doing a thesis, or work to get a gorvernment grant, I am sure we would have been more scientific, But hey nobody got paid for this, and I sprung for the gas.

So congratulations on your results, So are you the new propeller guru? How are you at 2 stroke engine maintenance?

[kc0iv]

The major factor I don't see in your test is blade efficiency. As loading changes blade efficiency changes.

Question there did you purchase or rent a propeller dynamometer?


Leon
(kc0iv)

[NoWingsAttached]

Your test is not repeatable. Period. How long did you burn in the engine at run-up? What is the margin of error on your scale? WHat is the maximum limit of the scale? what are the increments on the read-out?

Did you stab the throttle for one test, then gradually run up for another? Did you get at least 3 readings at each data point that were within 1% of each other?

If you hang a known weight from your scale, and do it three times from zero, and all 3 readings are identical, then that is a good start.

However, it is a probably that if you hang a 100 lb weight, a 200 lb and then a 300 and 400 and even 500 lb weight, you will start to notice some variations. THese are your error percentages, and must be less than 5% through the entire range of the test equipment, and typically is 1-3% error. Also, other factors must be taken into consideration and built into an error scale, such as repeatability and changes in engine temp, fuel density and air temps and humidity and pressures. THese things all change throughout a test. So it must be accounted for. THere is no such thing a 100% reliable test. With a typical test with a variation of 3% reliability then a 300 lb thrust test is only accurate to +/- 9 lbs, and a blade that measures 291 and a blade that measures 309 are therefore the same. Unless you can prove otherwise by repeatable testing. Even at 1% error, your blades will be comparable at 297 and 303.

If your increments are in 10 lb increments, then your degree of readout accuracy is 1/2, or +/- 5 lbs. That, in and of itself must be stated to assess the validity of your results.

[NoWingsAttached]

Scott: Hey, sorry man, I really like you, didn't mean to ruffle your feathers dude! I get pretty arrogant and caustic, sometimes I am a little hard to take. Please forgive any transgressions here. I value your friendship too much to want to piss you off like I did.

[Mac]

Scott Essex indirectly referenced Density Altitude.

Density altitude can really do a double whammy , it hurts engine performance and propeller airfoil performance. It is probably not too significant if test are done on the same day, then again, it might amount to 5 - 15 lbs if reading were taken early in the morning verses a reading taken in the hottest time of the day?

Density altitude for Amarillo (3,585 foot field elevation) this morning (10:53) was 2,337 feet.

Density altitude for Amarillo in July will be in the 6000+ range.




Density Altitude:
http://www.pilotfriend.com/calcs/calculators/density.htm

Wauchula/Bartow current conditions: http://forecast.weather.gov/MapClick.php?CityName=Wauchula&state=FL&site=TBW&textField1=27.5458&textField2=-81.8099&e=1


PS -- Keep doing those thrust test whether they are as methodical as Greg's or a crunched for time test at a flyin.

[NoWingsAttached]

Tim:

Who made you the pull test authority? We were comparing different props on the same engine (except for the FW guys) to see which prop did better. The measurement on the scale may not be exact but it's good enough to see which prop pulls more than the other.

Sorry dude, really. I go off half cocked when I'm half lit...Pardon me, fellas, but no, your test data is not bery reliable or useful. Your test here is questionable on so many levels, I just thought I would take the shotgun approach and let you know. Go over and read my last reply on my thread about answering your understandably indignant question concerning my credentials. Yes, suffice to say here that I am qualified on this subject, both professionally and academically.

One thing I can assure you is that I proved that you can take the SAME prop, SAME throttle settings, SAME pitch, etc., and produce results that are 20-25% in error with the previous data point and test! So, the results posted here, as they are posted, with no test parameters set and no predictable data points given are really not worth much. The data given is not apples to apples. It is not repeatable, since no info is given as to how the test was run. Was the throttle punched up from 3000rpms? Was it burned in slowly? Was it run up exactly the same for each and every test point? THese are things i am interested in.

I recall Chris Burgess explaining to me one day that he had been told by numerous old-timers in gyrocoptering that the best way to set your pitch w/o a dyno or scale was to pitch it somewhere in the neighborhood of allowing max engine revs 400 rpms below max allowable operating revs, but I think he mentioned that this was because the flying revs were always going to be higher than the static ground settings, not due to engine torque sweet spots. So, I must maintain, given the results of my testing, that you should set your prop to allow max engine revs to never approach max, but instead try to get a copy of your engine torque specs and set up your prop so that in flight your max engine revs are just beyond the torque max, where torque starts to just fall away. Otherwise, you are just wasting fuel with a prop setting that is under-pitched, and producing MUCH LESS than optimal thrust for good solid power up and climb-out.

If anyone doubts this, I would like to do more testing on this at Bensen Days, and see if my test is repeatable with other gyros and engines and props.

So, this thing here is as simple as this: how was your test run? Particulars, please. If you ran one prop on the motor at one RPM and one setting, then what were the other settings and findings? THese must be the same for all props and pitch settings. You can't just say max rev is 6500 for one prop/setting, and 6800 for another test, and the thrust is yadda yadda yadda. That is not useful information.

I have proved with one test session that maximum thrust is NOT a factor of maximum operating engine rpm and HP output. It IS, however, a direct corollation to maximum TORQUE. So any test that throws maximum engines revs out there as the end-all to the thrust test is flawed. You MUST first determine your engine's TORQUE sweet spot. Once that is established, then you can proceed to adjust a prop's pitch to that sweet spot and then, and only then, will you find the optimal performance settings for your individual prop/engine combo. If you have a fixed-pitch prop, then all that is just a waste of time, and you are stuck with max thrust results for that prop throughout the entire operting range of the motor it is bolted to. Your results here then are propably (bad pun, sorry)somewhat valid for these props, but you way missed the boat on the IVO and WD dude.

[Timchick]

I follow what you're saying about setting the pitch to the torque curve and not max RPMs and that does sound like it's worth trying. I couldn't figure out how to change the pitch on my wooden prop to do the tests your way. As far as repeatable, I tested my mac 3 times and it pulled the same all 3 times so I'm satisfied with my results.

[NoWingsAttached]

I'd really like to get set up for Bensen days, with a metal strap that will wrap around the tail wheels of most any gyro for a quick and easy set up, and start writing down numbers for thrust results of as many different gyros as I can, just to see what develops. Your thread here is what really got me going. I've had the scale, and just needed somebody to post something like this to get me interested.

The result is that now my gyro flys and climbs better than ever! HahA! SO, definitely some good came out of this discussion as far as I am concerned. :)