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Thrust measuring?

cjensen

cjensen

Well Known Member
dan said:
You guys are gonna love this...we did the thrust measurement tests today at Robert's hangar. It was fun to say the least. And the data will speak for itself. No, I'm not going to give any hints. I do have a spreadsheet and some charts, but you ain't gettin' it until Robert's report is done... :D
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thought i'd start a new thread for this subject. i know you aren't allowed to post the results yet, but dan, can give me (and maybe others) an idea of what it is you were testing? sounds interesting whatever it is, but i'm not sure i understand what was being done here...

:eek:
 
Here's the gist...

Robert Paisley (Eggenfellner Subaru dude extraordinaire) managed to borrow a "digital fish scale" type inline tension measuring tool from Sensenich. I don't know the details on how he acquired it. That went inline in a tie-down rope setup. Each plane would rev up to full power (some people chose to do different RPM tests), brakes off, and we'd note the peak tension in the line in pounds. This was a reading of thrust, at least a relative reading between the 7 or 8 planes we tested.

We had 2 different Subaru setups, my angle valve IO-360 + Hartzell, two parallel valve IO-360s (one with Hartzell, one with Whirlwind 200RV), an Avid Magnum O-290, and a Grumman Traveler O-320. We also had lunch... :p

I have an Excel spreadsheet of the data and two charts, one which plots all of the data points by RPM, and another which plots a comparison of peak thrust. If Robert doesn't use that spreadsheet in his report (I think he's planning to), then I'll post it here after his report comes out.
 
that does sound very interesting, noisy, and fun! :D looking forward to the results...any time frame?
 
Not sure, but it should be soon. Funny that I originally posted this in the "Eggenfellner West" thread, because, well, it was a set of tests run by Robert Paisley that included two Subarus...and it happened to be at Eggenfellner West. Funny how easily sidetracked people get when you start debating engines.
 
What you are talking about is "static thrust". We used to do this all the time on ultralight type aircraft. To be quite honest, it has very little meaning for an airplane that flies as fast as RVs. It may have some meaning as far as take-off is concerned, but at speeds much over 100 mph, it has little effect.
Mel...DAR
 
Mel said:
What you are talking about is "static thrust". We used to do this all the time on ultralight type aircraft. To be quite honest, it has very little meaning for an airplane that flies as fast as RVs. It may have some meaning as far as take-off is concerned, but at speeds much over 100 mph, it has little effect.
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I don't disagree, but when you take 7 airplanes with different powerplant/prop setups and run the same test, at least you get some sense of their relative strength -- even if it's only representative of the start of the takeoff roll. Hard to deny that this is at least interesting to many people.
 
Every test tells you something

dan said:
I don't disagree, but when you take 7 airplanes with different powerplant/prop setups and run the same test, at least you get some sense of their relative strength -- even if it's only representative of the start of the takeoff roll. Hard to deny that this is at least interesting to many people.
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Back in the day when I was testing computer performance, we used to say "every benchmark tells you something". How meaningful it is for how the device is used in the "real world" is a different story.

Here in Switzerland a static thrust test is required for every homebuilt, just to make sure it has enough power to fly! Seriously!
 
True, happy are we, drop it

Mel said:
What you are talking about is "static thrust". We used to do this all the time on ultralight type aircraft. To be quite honest, it has very little meaning for an airplane that flies as fast as RVs. It may have some meaning as far as take-off is concerned, but at speeds much over 100 mph, it has little effect. Mel...DAR
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TRUE, but interesting.

dan said:
I don't disagree, but when you take 7 airplanes with different powerplant/prop setups and run the same test, at least you get some sense of their relative strength -- even if it's only representative of the start of the takeoff roll. Hard to deny that this is at least interesting to many people.
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Dan, I can tell you are almost giddy with delight and chomping at the bit to spill the beans on the data. Yours must have been the highest. Am I right? lol

rv8ch said:
Back in the day when I was testing computer performance, we used to say "every benchmark tells you something". How meaningful it is for how the device is used in the "real world" is a different story.

Here in Switzerland a static thrust test is required for every homebuilt, just to make sure it has enough power to fly! Seriously!
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Does Switzerland still require a gear drop test? ouch! :eek:

Cheers George
 
Gear drop test

gmcjetpilot said:
Does Switzerland still require a gear drop test? ouch!
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Yes, but it's normally done by the kit supplier. Or, you have to have a finite element analysis done on the landing gear. The first type of any experimental metal aircraft "certified" in the country has to have a wing loading test. Every non-metal experimental aircraft has to have the wing loading test done. I'm told that at least two have failed, one at less than 1G.
 
Robert is up to his ying yang in R&D projects currently and is trying to find time to compile and publish the results of the test. Should be soon. :)
 
Haven't heard from him. I should just post the Excel spreadsheet (with charts) here...
 
I'll give you some news-- don't pull from the tie down ring on an A model; otherwise you'll come close to damaging the rear bulkhead-- I sure don't know where I'd start-- if I had to fix THAT.

even with my wimpy composite 72" prop I did some damage. dan outpulled me by over a 120lbs. IIRC.
 
Anxiously waiting.
lurker.gif
 
Static thrust

This is great info, "Mr. Anonymous" - thanks for sharing it. I've gotta say, the results that are the most surprising to me are Pete's. Good stuff!
 
I was also very surprised by Pete's data. I guess weight & drag (particularly cooling drag) play as significant role in determining in-flight performance as, well, everybody says they do... :rolleyes:
 
dan said:
I was also very surprised by Pete's data. I guess weight & drag (particularly cooling drag) play as significant role in determining in-flight performance as, well, everybody says they do... :rolleyes:
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A few months ago I tried to make this point on the Eggenfellner list. Robert Paisley had stated that his comparison flights with Dan Checkoway represented a "perfect" horsepower comparison. I responded by pointing out that there were other variables...cooling drag, propeller differences, mufflers hanging in the breeze, etc. Robert's response to my post was fairly dismissive...he discounted these variables...particularly the cooling drag argument. Thereafter, Jan blocked my attempts to respond, even thought my thoughts were entirely constructive and polite.

Dan Vandenberg
 
Missing something "In flight performance"

djvdb63 said:
A few months ago I tried to make this point on the Eggenfellner list. Robert Paisley had stated that his comparison flights with Dan Checkoway represented a "perfect" horsepower comparison. Dan Vandenberg
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I am missing something? Did you guys do side by side flights? What was the results? Thanks. George

I thought the Eggy group forum was sanitised. That sucks. You know that says something.
 
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gmcjetpilot said:
I am missing something? Did you guys do side by side flights? What was the results?
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It was just one day Robert and I were flying along side-by-side. Robert had a heavy passenger and I had an empty right seat. Robert easily pulled away from me by about 3+ knots. I'm not sure what his fuel burn was.

After that I wanted to go up and "bracket" several airspeeds at several altitudes and compare fuel burns. We never did that test. I'm ready any time, but I think Robert is pretty busy.
 
Roger! Got it, thanks Dan

dan said:
It was just one day Robert and I were flying along side-by-side. Robert had a heavy passenger and I had an empty right seat. Robert easily pulled away from me by about 3+ knots. I'm not sure what his fuel burn was.
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Yes, thank you. I was wondering the fuel flow thing also, at 50" or 34.5" of MAP that must be sucking some gas. G
 
this is strictly passing on information that i read on the subie yahoo group tonight...

jan says that the H-6 with new redrive will push 900lbs of thrust!!! :eek:

i have nothing substantial other than he typed it...

(i'm still very uncertain about the new redrive and prop combo, even though i have a deposit on one. glad i don't need and engine RIGHT NOW!! :rolleyes: )
 
This version of the data might be interesting to some:



This plot shows the normalized data (assuming your HP numbers are correct...). There is a 20% deviation if you look at people's max lb/hp.

It would appear that the 3 blade guys don't generate as much lb/hp (or they are lying about hp). I thought that besides being 'turbine smooth' :) 3 blades were supposed to generate more static thrust.

What Hartzell is on the Fred's plane?

Where you using an optical tach or each plane's instrumentation?

Fuel flow would have been interesting so we could have a better estimate of HP.

chuck
 
chuck said:
What Hartzell is on the Fred's plane?
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I'm fairly certain it's the 72" C2YK 7666-A4, same as mine.

Where you using an optical tach or each plane's instrumentation?
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Each plane's instrumentation.

Interesting plot...something to consider is that Fred's "180hp" engine is probably producing more like 195hp. It's one of the "hopped up" parallel valve setups. And Robert's setup may be 220hp, but at what manifold pressure? At 50" of boost, who knows what the horsepower output really is.

Fuel flow would have been interesting so we could have a better estimate of HP.
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Even then it doesn't really translate directly. I did lean my mixture, but it was a WAG. I didn't sit there and run for a while, tuning my EGTs for peak power. I just kind of slapped the lever where I thought it should be to produce max power at that altitude. I don't know how the others leaned. My point is that fuel flow alone doesn't translate directly into horsepower.

I think the purpose of this test (Robert can speak to the real purpose, since the whole thing was his idea) was to get a relative sense of how much power these engine/prop combos can produce.
 
Prop it up

chuck said:
This version of the data might be interesting to some:

This plot shows the normalized data (assuming your HP numbers are correct...). There is a 20% deviation if you look at people's max lb/hp.

It would appear that the 3 blade guys don't generate as much lb/hp (or they are lying about hp). I thought that besides being 'turbine smooth' :) 3 blades were supposed to generate more static thrust.

What Hartzell is on the Fred's plane?

Where you using an optical tach or each plane's instrumentation?

Fuel flow would have been interesting so we could have a better estimate of HP.

chuck
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Chuck great observation, but I would say full power at no airspeed is out of the "props" normal envelope or may be more accurately at the extream end of the envelope. Props that are optimized for high speed cruise may have less static thrust? Any way very interesting bench mark. I am all Lycoming guy but I can be happy that the Subaru's made a good showing. However as Dan pointed out cooling drag and other factors like weight affect overall performance.

George
 
dan said:
And Robert's setup may be 220hp, but at what manifold pressure? At 50" of boost, who knows what the horsepower output really is.
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Just a reminder, Robert is running at 50" MAP not 50" of Boost.

Nathan Larson
 
Thats IT

dan said:
I think the purpose of this test (Robert can speak to the real purpose, since the whole thing was his idea) was to get a relative sense of how much power these engine/prop combos can produce.
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Bingo, that is exactly right. It is just a "Static Thrust" test and its fairly easy to compare. It does indicate thrust, which is both prop efficency and engine HP indicator.

I am glad the Subie did well. However a 2.5L with no blower, 28-29" of MAP would obviously have much lower T. Regardless that is their "configuration" benchmark, fuel flow or not. Its there for all to see. Now how does that relate at 200 MPH? Its a differnt story; not a stand alone predictor of flight performance. G
 
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dan said:
I think the purpose of this test (Robert can speak to the real purpose, since the whole thing was his idea) was to get a relative sense of how much power these engine/prop combos can produce.
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I can see it now, 'air-plane pulls' at fly-in's complete with announcers and flames, smoke......

It is certainly interesting to see who can pull the hardest. IMO though it is not that interesting that a 220hp supercharged engine can generate more thrust than the 200hp engines. That is sort of a given on some level.

I'm curious about the details, why did the -4 seem to do so well, why do the high hp engines do poorly when normalized, why is the whirlwind's thrust/rpm slope so much steeper than the MT, why is the 125hp w/fixed pitch almost the most efficient combination?

In order to answer these questions care must be taken in getting the data so valid conclusions can be drawn. For example CS props tests probably should run several pre-arranged RPM/MP combinations, leaned to 50ROP. An external tach should be used to get that part right, fuel flow should be noted.... Wish I had friends with all those engine/prop combinations...

Chuck
 
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chuck said:
...why did the -4 seem to do so well...
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Fred's -4 is extremely strong. I don't know what he did to the engine, i.e. high compression, porting & polishing, etc., but I gotta assume it's one of those "190hp" parallel valve 360s. I can find out the details.

Also FYI, Fred's -4 can easily outrun me by 2 knots in an all-out side-by-side cruise fest at around 4500'. We did that about 2 months ago and he pulled away from me.

There aren't many normally aspirated 2-place RVs proper (non Rockets) that can pull away from me. The only two that I know of are RV-4s with hopped up parallel valve IO-360s.

Fred's airframe is also straight as an arrow.

Oh...by the way, Fred will be selling it shortly, as he's got an HR-II in the oven. Email me privately if you want Fred's contact info. If I were in the market for a used RV-4, Fred's would be a sweet one!
 
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