"Gross" and "Net" rotaries power outputs.

[Bletchley]

Thank you Greybeard, this is a very interesting subject and I think we may be slightly at cross-purposes (misunderstanding one another), as I do agree with you that the British engineers appear to have measured rotary engine output as 'gross' (without any reduction for windage) rather than as 'net' (with a reduction for windage). I do not know why S D Heron is quoted as having made a distinction between the use of a 'dynamometer' and a 'torque stand' (maybe terminology has changed between then and now, or perhaps Andrew Nahum has misquoted), but the meaning nevertheless seems clear: the rotary engine builders "insisted" that the "windage loss... was recorded as useful horsepower". This is evidence, I think, that British practice was indeed to record the hp as 'gross', as is your reference to Report no.448

I am not convinced yet, however, that the French practice was, instead, to record the output as 'net' (with a reduction for windage), although I do admit that it is an intriguing proposition. S D Heron is not quoted as saying "British rotary engine builders" but "rotary engine builders" (of which the vast majority were French), and I don't think the difference (or rather lack of difference) in level speed between the Clerget and the Bentley Camel is sufficient evidence for this proposition, as there appear to be other reasons, already mentioned in this thread, to account for it. Why also, for example, did pilots think that the Bentley Camel was so much better than the Clerget Camel, if the power diferential was so small - and why would the Air Board record the output of the 9BF (a British built engine) as 'net' whilst recording the output of the AR1/BR1 and BR2 as 'gross' (that doesn't make sense to me)? Some documentary evidence from a French source that confirms that they did indeed record the output as 'net' is required now, I think.

Thank you for being so patient with me, and for the link

Bletchley

[Machinbird]

Originally Posted by Greybeard

............................................
I would be explained what a "dynamometer" is intended in previous quote: as a mechanical engineer, I don't know any device to measure power different from "torque*RPM" system, where torque is measured by just a dynamometer (more precisely a brake, a water brake, I think, at that time).

Thanks as always for your big help.
GB

GB, I think the historical use of the term torque stand is important. You undoubtedly realize that there are two locations that the torque of a rotary engine can be measured. One at the propeller attach point and one at the engine mount. The conventional dynamometer measures torque at the brake which is attached to the propeller attach point by some sort of shaft. This is net horsepower. But if you were to measure the torque at the engine mount, you would have a higher torque which would represent the sum of torque due to windage and the torque of the brake and would represent Gross horsepower. Undoubtedly the term "torque stand" refers to this different way of measuring horsepower. For non-rotary engines, the torques at both locations would be the same and it would be easier to measure torque at the brake.
Sid

[Greybeard]

Originally Posted by Machinbird

The conventional dynamometer measures torque at the brake which is attached to the propeller attach point by some sort of shaft.

Sorry, I still can't understand.

I believe, whatever can be the engine, we have always a rotating stuff and a fixed one: we can attach a dynamometer only to the fixed one, for obvious reasons, while the rotating one is braked and its revolution counted.

If it would have been so easy to separe the two kind of powers WHY, please, Air Ministry would have provided all that apparatus of Report No.448?

S!
GB

[FlyXwire]

I think ya'll need a little break here, so maybe a period drawing will provide the needed diversion.



In the meantime, I want to commend Dave Layton on his previous posting here, and the very succint points he made on the first page of this thread (for emphasis).

[Kacey]

Originally Posted by Greybeard

I fear it's not so. Report No.448 by Technical Department at the Air Ministry, May 1918, it's not clear about; B.R.1 is credited with 150 HP at 1250 RPM and then are sperimented losses for windage, leaving to think 150 HP is "gross" power output. Do you think, or have evidence that B.R.1 could otherwise develop about 180 HP inclusive of windage? In addition (and again): why B.R.1 powered Camel should have same speed of Clerget powered one, with 24 HP more?GB

GB,

As you know I too have wrestled with this data!!!

I go back to sources like Jane's 1919 (the table I sent you) and Aerosphere 1939.

I find that the BR.1 is listed as a rated 150hp@1250rpm, with normal output at this speed of 154bhp@1250rpm, with a 5.9:1 CR. It's maximum output is listed as 156bhp@1300rpm. These are BRAKE HORSEPOWER I'm assuming from a dynometer test(which means that friction, dynamic and windage losses are netted out, because their not being read by the dyno).

Notice also this the 5.9:1 CR engine, or high compression BR.1!

So!! When we start to talk about the original Admiralty Radial (AR.1) built for the RNAS were talking about a lower powered version of the engine above!

Can we agree on that????

Therefore, when I see the BAB listing for the AR.1 as a 150hp@1250 engine, I say "OHOA PARTNER!!!!!" This is a smaller horse! So I'm going to get less pull!!! Right!!

It appears the Admiralty Radial is being "misquoted" as a BR.1(HC)!!

I've cal'd what it's actual output "most likely" is, hope someone can confirm or dispute these figures:

Admiralty Radial AR.1, misrated 150hp@1250,with actual output of 127bhp@1250rpm and 128@1300rpm, with a 4.7 - 5:00:1 CR.

Basically, I took the BR.1(HC) and reduced it's compression to arrive at these figures for a AR.1/BR.1(LC).

Now, when I use these figures in my correlations I get the AR.1 powered Camel 1F.1 with a speed of 111mph@1300rpm@10,000'(BAB data says 111mph)

I get the BR.1(HC) Camel 1F.1 with a speed of 120mph@1300rpm@10,000' (BAB data says 121mph)

Close enough for ME, and I'm a stickler for this data, as you know!!!!

Anyway that how I see the data sources fitting together!!


Respectfully Submitted,

KC

P.S. Bletchley, where is this Report#448? Is it in the data I got from you?

[Machinbird]

Originally Posted by Greybeard

Sorry, I still can't understand.

I believe, whatever can be the engine, we have always a rotating stuff and a fixed one: we can attach a dynamometer only to the fixed one, for obvious reasons, while the rotating one is braked and its revolution counted.

If it would have been so easy to separe the two kind of powers WHY, please, Air Ministry would have provided all that apparatus of Report No.448?GB

GB, The link to report #448 is here:http://naca.central.cranfield.ac.uk/...arc/rm/448.pdf
You may want to re-read the intent of the experiment. It is to determine airframe related effects on windage both at rest and in flight for a particular airframe and engine combination. Static windage torque was not identical with inflight windage torque. The cowling and the propeller both had substantial effects on windage torque as did airspeed. There is no need of an apparatus such as described in the report to measure windage torque of an engine operating on a stand. Obviously since I am using the word torque here, we are referencing some common rpm for an apples to apples comparison. I could as well have said horsepower and still been correct.

FlyXwire, Thanks for the picture. Your picture of a torque stand pretty well demonstrates the concept. With RPM data, you will have Gross available horsepower (assuming the prop blast does not upset the scale.) The stand illustrated appears to be a bed type stand, but perhaps with the correct adapters, you could mount a rotary engine to it.

[Kacey]

Originally Posted by Machinbird

[/B]
GB, The link to report #448 is here:http://naca.central.cranfield.ac.uk/...arc/rm/448.pdf
You may want to re-read the intent of the experiment. It is to determine airframe related effects on windage both at rest and in flight for a particular airframe and engine combination. Static windage torque was not identical with inflight windage torque. The cowling and the propeller both had substantial effects on windage torque as did airspeed. There is no need of an apparatus such as described in the report to measure windage torque of an engine operating on a stand. Obviously since I am using the word torque here, we are referencing some common rpm for an apples to apples comparison. I could as well have said horsepower and still been correct.

Oh, my god not those wooden model engine tests again!

Well, I took the time to read those things (both of them Report#448 & #591)
and I will still agree they are good for 'WHAT THEY WERE INTENTED TO DISCOVER'.

Which were the effects of forward motion and upward forward motion, cowling, venting and a few other phenomenon on rotary engine performance.

And as long as we all understand they don't represent friction and other dynamic engine losses, then hears what I was able to pull out of the Report #448 data.

If you look diagonally across TABLE #5, you will see that the rotary engine is rotating at 1150 and 1250rpm without a cowling and without the propeller in the top left two data figures.

THIS WOULD REPRESENT THE ENGINE TESTED ON A DYNOMETER STAND WITH THE ENGINE ROTATING IN A ZERO VELOCITY WIND

Next skip diaganolly across the table to the bottom right side and you will find the figure for the rotary engine rotating inside the cowling with the propeller rotating in front (i.e. just like on the real aeroplane) with a supplied wind speed of 70mph and 120mph.

GET READY FOR THIS!!!

The 70mph @ 1150rpm real unit engine simulation is 21% LOWER than the BARE ENGINE DYNO test at the same RPM!!!

The 120mph @ 1250rpm real unit engine simulation is 3% LOWER than the BARE ENGINE DYNO test at the same RPM!!!

BOY WAS I LOOKING FOR DATA LIKE THIS!!!!!

Maybe the reason the ROTARY ENGINE MANUFACTURERS were screaming about the DYNO test NET-TORQUE reporting method was they suspected that the real effects were less than the static test stand figures!

As these very sophisticated wooden engine model tests so now clearly show!

Bet you didn't see that coming!! I didn't until it jumped out at me!!

Anyway, just some more rambling thoughts.

Respectfully Submitted,

KC

[Greybeard]

KACEY

You hit the mark. Absolutely. No comments to add on my side. Congratulations and thank you.


BLETCHLEY

I would only comment that IMHO Clerget 9BF wasn't a "bluff": its 148 bhp reported on Air Board Data Sheet must be "net", since they give a top speed of Camel available only by some 20 hp more and comparable with that got with B.R.1.

MACHINBIRD
I agree about reasons for Air Ministry to have that sort of testing apparatus, but still it is unclear for me how to measure net power (perhaps sort of torque converter as part of the water brake applied on rotating side of engine?). Anyway, they could (and did) measure "gross" and "net" horsepowers... then happily mixing them even on same official document! LOL


So far, I would try sort of "resumé", hoping to complete it, with your help, adding all other main rotaries of WWI:

Le Rhone 9J: 130/110 (respectively "gross" and "net" power output, rounded to closest ten) @ 1250 RPM

Clerget 9B: 150/130 @ 1250 RPM

Clerget 9BF: ?/150 @ 1250 RPM

A.R.1: 150/130 @ 1250 RPM

B.R.1: ?/150 @ 1250 RPM

S!
GB

[Kacey]

Originally Posted by Greybeard

KACEY


MACHINBIRD
I agree about reasons for Air Ministry to have that sort of testing apparatus, but still it is unclear for me how to measure net power (perhaps sort of torque converter as part of the water brake applied on rotating side of engine?). Anyway, they could (and did) measure "gross" and "net" horsepowers... then happily mixing them even on same official document! LOL


So far, I would try sort of "resumé", hoping to complete it, with your help, adding all other main rotaries of WWI:

Le Rhone 9J: 130/110 (respectively "gross" and "net" power output, rounded to closest ten) @ 1250 RPM

Clerget 9B: 150/130 @ 1250 RPM

Clerget 9BF: ?/150 @ 1250 RPM

A.R.1: 150/130 @ 1250 RPM

B.R.1: ?/150 @ 1250 RPM

S!
GB

GB,

Please correct me if I'm wrong (I know you will).

But you can ONLY measure 'NET TORQUE' with a Dynometer set-up.

From this "Net Torque" you can convert to Net HP (BHP). The only way to come up with Indicated HP (gross hp) is to measure Friction/Dynamic hp required to turn the mechanical engine parts.

This is WHY NACA performed their 'Friction HP' runs on the Liberty and H-S engines.

NACA Report#102 and #103 and #46.

This entails driving the 'non-operating' engine (after is has reached operation temperature) with an external dyno-driver and measuring the torque required to 'reciprocate' the non-operating engine at different RPM's

Of coarse you have to make sure you are driving the complete lubrication system so you are getting the 'true' friction torque and not some higher figure based on faulty lubrication.

Anyway, after you have the FHT/FHP figures you simple add it to the BHP (net) figure to obtain the Indicated Horsepower(IHP/Gross).

I do not believe there is a way to READ Indicated/Gross Horsepower directly!!!

To get Rotary Engine Indicated/Gross HP you have to add the TWO factors (1)windage and (2)friction.

The Reports #448 and #591 address only the 'windage' factor.

Just my thoughts on the subject.

Respectfully Submitted,

KC

[Bletchley]

Some more information

It looks to me as if the time-line for the introduction of these four engines was Clerget 9B French-built (used for the RFC Camels only) - Clerget 9B British-built (used by RNAS mostly on the Strutter and Triplane, but possibly on prototype or early RNAS Camels as well from March/April 1917?) - A.R.1/B.R.1 Low Compresion (used on RNAS Camels from June/July 1917) - Clerget 9BF (Used on RNAS Camels from July 1917?) - B.R.1 High Compression (used on RNAS Camels from August 1917?). There is likely to have been very considerable overlap, as new engines were phased in, and after April 1918 8 Naval was re-equiped with Clerget Camels with 9B engines from RFC stocks (presumably French built).

This is based on:

1. Date of Sopwith Camel flight tests listed in the Air Board Data Sheets

Clerget 9B: March 1917
A.R.1/B.R.1 (LC): April 1917
Clerget 9BF: July 1917
B.R.1 (HC): August 1917

2.Information from Graham Mottram's little pamphlet on Bentley Aero-Engines:

"It is difficult to determine precisely when this engine [A.R.1/B.R.1] first ran on the test bed. It was probably in the late summer or early Autumn of 1916... [and] ...by the end of the year, reliability had been improved to the level where some production engines could be made. Three engines had been delivered by the end of March 1917. One of them was fitted...to the Sopwith Camel naval prototype... [and] ...production engines were ordered for Camels for the RNAS. On 4 June 1917, Flt. Cdr. A. M. Shook of 4 (N) Squadron at Dunkirk used a Bentley powered Camel (N6347) to shoot down an enemy fighter...the first combat victory for the new engine... Under the pressures of war, production and development went along side by side. There were changes to the BR1's compression ratio...

3. This, from W. O. Bentley's memoirs:

"Harrassed by Russell (as if we needed and spurring on!), we got the [A.R.1/B.R.1] prototype on the test-bed by the early summer of 1916... and the B.R.1 was ready for the Admiralty Inspector... by the late summer and in production by the autumn [1916]... Later we raised the compression so that the Camels got more speed at heights above 10,000 feet"

4. Memoirs of Leonard Rochford (3 Naval) and Christopher Draper (8 Naval).


For those that do not have the Air Board Data Sheets, here is the respective climb figures:

Clerget 9B: 6.0 (6,500 ft), 10.6 (10,000 ft), 20.7 (15,000 ft)
A.R.1: 5.5 (6,500 ft), 9.8 (10,000 ft), 20 (15,000 ft)
Clerget 9BF: 4.9 (6,500 ft), 8.5 (10,000 ft), 15.75 (15,000 ft)
B.R.1 (HC): 4.7 (6,500 ft), 8.3 (10,000 ft), 15.9 (15,000 ft)

You certainly seem to be on to something here, GB! I am still not convinced by your net/gross argument, but the early BR1 (AR1) certainly does not appear to have the performance to justify its 150 hp rating or its reputation - it is clearly only marginally better than the 126 hp Clerget 9B, and has a performance clearly inferior to that of the 148 hp Gwynnes/Bentley Clerget 9BF. The later high compression BR1 is also, clearly, only marginally better than the 9BF.

Bletchley