Conspicuous by Their Absence

[aleatorylamp]

Big Zeppelin Engines

Hello Ivan,

Thanks for your very interesting, well expounded and detailed reply, and for confirming some of my assumptions. I respect your opinions very much as they have a larger knowledge base than mine.

I further delved into the old documentation that I have on the engine in question:
The Mercedes DIVa engine was a class IV aero engine, with 260 specification Hp, (factory guarantees etc), with 267 Hp effective for military use. Maximum power was in reality 275 Hp, but not for continuous use, and I have seen no documents that indicate if this was for 5 or 10 minutes, or if it was ever used. I expect that in those days it was rather avoided because of a high risk of structural damage, so one could say there was no WEP. I do know, however, that the 267 Hp was maximum continuous at 1450 RPM. I also found the data relative to the idle speed, which was 300 RPM - I think the minimum for FS2k2 is 410 RPM and for CFS1 it may be around 450.

Initially these engines operated normally and safely at 800 RPM on airships and suffered some damage when stressed to continuous 1200 or higher RPM below rated altitude, but this was quickly corrected, and as of the rated altitude, maximum of 1450 RPM could be safely maintained. Maximum speed was 73 kt, and cruise speed, 54 kt. Take-off (rotation) was 48 kt, stall 43 kt, and cruise-climb 50-51 kt. Expedite climb was 46-48 kt.

I haven´t been able to find the RPM for the lower altitude gated throttle positions, only the Hp calculation by which power at sea level would be about 227 hp, which sounds reasonable. Could that be calculated?

Incidentally, the smaller (also 6-cyl and high-compression 4.6:1) 180-200 Hp Mercedes D.IIIaÜ engine, used on the Fokker DVII, was rated at altitude (which altitude is not stated) for 204 Hp at 1600 RPM, and rated at sea-level for 174 Hp at 1400 RPM. These engines were not able to operate at full throttle at sea level, utilising a self compensating carburettor. This engine had a warm-up idle speed of 200 to 250 RPM, and then a normal idle speed of 300-350 RPM.
The normal version of this engine was the 160 hp Mercedes D.III with a compression ratio of 4.5:1

One could perhaps suppose that the D.IVa being a larger engine with higher compression ratio (4.82:1 or 4.94 :1, depending on the source) than the DIIIa, that the difference between high and low altitude RPM would also be greater, maybe 300 or 350 RPM, so perhaps the estimated 227 Hp at sea-level would be at an estimated 1100 RPM.

In the simulator, once you get 267 Hp at 4300 ft, and aim for 227 Hp at sea-level, would the RPM not be given automatically? ...or is this maybe a silly question?

As regards Table 512, I´ll have a go at shifting all the columns over by one - to the left, I presume?

OK then, thanks very, very much again,
Cheers,
Aleatorylamp

 

[aleatorylamp]

Big Zeppelin Engine Propellers

Hi Ivan,
Well, well... I think you deserve a drink, or even a treat you to your favourite meal!!
I moved the columns in the 512Table from the Hurricane to the right - not to the left, as the numbers compared to the P51D, which worked worse, and the lower numbers that I had in my own, which worked a little, indicated this. Then, the first column obviously had to be extrapolated, and... lo and behold! ... the results are getting much better, although the idle RPM has gone up to 512.

I would understand this change to the propeller pitch, probably as the blades being "bent" to improve performance, to a more feathered angle for the much lower HP, and that in my old 512 Table, the much lower values meant they were too feathered... Now we have:

Sea Level, just after Take-off:
1126 RPM - this would probably be within the expected range
233 HP - slightly above the expected calculated sea-level 227-230hp power range

4300 ft rated altitude:
1264 RPM - a bit low - I´m aiming for 1450 RPM
268 Hp just 1 Hp too high!
73 kt: Speed seems on the dot, but of course this is really a matter of Zero lift Drag adjustment.

Now, lowering manifold pressure below 31.6 gives much lower results.
I have boost gain at 4.2 and will try changing that later and see what happens.
I´m off to work now!
Cheers, and thanks again!
Aleatorylamp

 

[Ivan]

Engines & Propellers

Hello Aleatorylamp,

Sorry about not getting back sooner, but without reliable Internet access, posts are challenging at times.
My son needed his computer for homework and the iPad was in use much of the time. I still have not had a chance to download your Big Zeppelin yet.

First of all, thanks for the compliments I think, but unfortunately I believe in this case I believe you are heading in a direction that will not yield useful results in the long run.

In a sort of realistic view of the world, you must first get your engine running properly on the test bench before trying to fly it.
To do this, you need to have both proper Engine RPM (most important) and then proper Engine Horsepower.
I suggest first getting the basic engine dimensions correct which I believe you have done.
This is a normally aspirated engine (not supercharged) so the absolute Manifold Pressure should be limited to 29.92 inches of Mercury (Ambient Sea Level Pressure as in Standard Temperature and Pressure).

To match Engine MP and RPM, I suggest strongly that you use a Constant Speed Propeller. Let the simulator decide the propeller pitch (mostly).
You will most likely find as I did that the Engine cannot achieve full RPM. This is where you start tweaking the Power Coefficient Table (Record 512). Don't worry about what exactly this means at this point because this table will get thrown away when you are done and be rebuilt anyway.

********************************************************************************************
THIS is where I got stuck earlier:
At this point, you will realize that the performance parameters of your engine do not match reality. While it is possible for an engine to gain a slight amount of HP as it rises from Sea Level, it won't be much.
You need to decide (and this is where I can't help) what is the power limitation at Sea Level and what the proper HP should be.

We understand that the engine is not authorized for full throttle operation below 4300 feet, but HOW is power reduced?

1. Is it a RPM limitation? We CANNOT easily handle this in CFS. The player can easily use full RPM at any altitude and while we CAN limit this with the propeller tables, we should not because it would cause a lot of ugly side effects.
In other words, this is a procedural limitation for engine operation and we can't enforce those.

2. Is it a Manifold Pressure limitation? We CAN sort of implement those although I am uncertain about some of the altitude effects you may have.

Now Here is how to implement Case 2:
First tune the engine for 29.92 inches MP at sea level (I test at 500 feet) for 267 HP.
Take it to 4300 feet and adjust TORQUE and FRICTION to get your proper power output.
Record your actual MP used to achieve this. Most likely it will be around 27 or 28 inches or somewhere below STP.

Throttle back to your reduced Sea Level MP and see what the power is. Most likely you are going for power rather than MP in this case. Don't worry about getting it exact at this stage because the fixed pitch prop we are switching to later will take care of a few extra HP. In other words, Aim for a few HP above what you actually want.
Record this MP. This will be your base maximum MP.
Use supercharger settings to get the higher MP you need at 4300 feet.

Now Here is how to implement Case 1:
First part is the same: Tune the engine for 267 HP.
Next decrease RPM using the Propeller RPM control to the speed you want.
Use the Torque and Friction tables to adjust it to match your proper HP.
Be careful here. It is possible to create some pretty interesting situations which are entirely illogical.
Now remember that the RPM limitation is procedural. The player may ignore this at will.

To Be Continued.

 

[Ivan]

Engines & Propellers (continued)

Now that we have a properly functioning engine fresh off the test bench, we can decide how to make it drive an aeroplane.

Table 512 is interesting because it combines a lot of factors together that I find to be non-intuitive.

It represents the Propeller Power Coefficients at various Blade Angles and Advance Ratios.
(Yeah, you already knew THAT, so what did I just say?)

So what exactly IS a "Power Coefficient"?
Here is where things get dangerous because it is my "understanding" of how things work.

It is a measure of how difficult a propeller combination is to turn; It is a measure of air resistance.
(Inertia is handled elsewhere)

Here are the factors that contribute to this:
1. Propeller Diameter
2. Engine Reduction Gear Ratio
3. Number of Blades
4. Propeller Activity Factor - Are the blades narrow or broad chord?

Your propeller is a rather interesting case because it is HUGE and yet not terribly efficient.
The Huge part is only so in relation to Great War era aeroplanes. Later propellers were harder to turn which is why you can't get full RPM when using any of the stock Table 512s.
I could not either which is why I suggested shifting the columns over by one.
In other words, pretend that the big two blade wooden propeller at 25 degrees nominal pitch is similar to a bigger metal propeller at 20 degrees.
In reality this is just a "quick fix", but it is the best idea I know of until I can figure out how to generate Table 512 on my own.
I was actually pretty well on the way to doing this with a combination of a couple spreadsheets and a C Program until my laptop decided it was done. I happen to need this for a couple aeroplanes of my own but was spending a fair amount of time until recently on a certain Design Study.

As for Idle RPM, I believe it is quite possible to tune this VERY low by tweaking the Torque Table and Throttle Tables, but I suggest you do not do this until the high RPM power settings and propeller are final.

As for your mention of Maximum and Minimum Governed RPM in an earlier post, I don't believe those parameters actually do anything other than affect the animation of the propeller.
I use those to control Propeller Animation which I started describing in a Propeller Animation Thread a couple years ago but haven't continued because I didn't see there was any interest and because the screenshots all got lost with the prior crash. I call it a description because although I can get the effects I want, I can't predict how the numbers actually affect things. I just list the working combinations I have found in a notebook.

Hope this Helps.
- Ivan.

 

[aleatorylamp]

Big Zeppelin Engine throttle control

OK, Ivan!

Don´t worry about not getting back soon enough, it´s definitely sooner that I expected!
I´ll have to re-read your 2 last posts for more detail, but for a start, I have to explain more clearly how these engines worked.
Because of the lack of oxygen higher up, normal engines started pinking and leaning the fuel cured this to prevent damage - and of course power went down. It soon occurred to them that increasing the compression they could compress more air to burn more fuel, to get more power higher up, but couldn´t give full throttle at sea-level because the engine would break. The metal wouldn´t handle the pressure in the cylinders.
On the normal D.III Mercedes engine (150 cu. inch per sylinder with 6 cyl) they had a compression ratio of 4.5:1 and got 160 Hp. Changing the piston shape they came out with the D.IIIaü "over-compressed" engine managing a 4.64:1 ratio and had a carburettor which automatically limited low altitude throttle. The power at altitude was 180-200 Hp at 1600 rpm, and lower down, 175 hp at 1400 rpm. BMW had an even more spectacular one.
The Mercedes D.IVa was bigger (220.6 cu inch per cyl) and the compression ratio was 4.82:1 or 4.92:1, depending on the source, but this one could not be managed automatically by the carburettor, and had to be controlled manually. First they had 3 throttles which would be sequentially activated one after the other, depending on the altitude, the third of which gave full throttle at the rated altitude. It was mechanically more practical though, to have only one throttle, with 3 barriers.
For sea-level take-off, the throttle would be advancesd to the first barrier or gate, and then the navigator would come and remove it, say at 1400 ft, and the pilot moved the throttle forward to the next barrier. Then the navigator would come again at 2800 ft and remove it, and the pilot would advance the throttle to the next gate. Then, at 4300 ft, the navigator would remove the last gate and the engine had its full 267 Hp at 1450 RPM at that altitude.
Theoretically, were full power given at sea-level, this engine would have delivered 307 Hp, had it been able to withstand the cylinder pressure, which it couldn´t , and would have blown up.
So the reasoning here is that this can be mimicked by using a virtual turbocharger for this system, whereby the .air file manages the throttle position relative to altitude so that the simmer doesn´t have to do that - because if it were manual and he didn´t do it, low altitude preformance would be completely unreal because the 307 Hp would have blown the engine apart in real life, but not in the simulator.

It´s like having a 227 Hp engine (sea-level performance) with a turbocharger that sets in progressively, giving full 267 Hp at 4300 ft.

More comments later - tea-time and back to work for the afternoon!
Cheers,
Aleatorylamp

 

[aleatorylamp]

Throttle and propeller control

Hi Ivan,
More to the details in your last 2 posts: Even if the results of the new Table 512 are approximate, hence only useful short term, at least there´s a sensation of getting somewhere!
After my explanation on how the engine works, the increase from the allowable sea-level 227Hp to the 4300 ft 267Hp-maximum, is in theory analogous to a turbocharger, so then we do need the extra manifold pressure, becuase otherwise we´d be getting no extra power. The Mustang increased it to just over 2 atmospheres, and the Hurricane just under 1.5.

For the moment, "my" increase is very little - just over 1, but it must be there, otherwise, there
would be no point. Using 29.92 we might as well have a normal 307 sea-level Hp engine that we can´t fully accellerate until it´s higher up, and when we can do so, with the altitude loss, we would be getting our desired 267 Hp at the desired altitude.
I´ve just implemented the constant speed prop, and the full throttle readings for level flight at
4300 ft are:
rpm: 1267
HP: 268
speed: 73 kt
angle of pitch: -2.33

By the way you said:"Table 512 is interesting...It represents the Propeller Power Coefficients at various Blade Angles and Advance Ratios. (Yeah, you already knew THAT, so what did I just say?)"
To be quite honest, not really... I only get the gist. Is "Advance Ratio" the shift in blade angle on
a variable pitch propeller? Why is the number negative when you are going full speed ahead, or is it the advance ratio which is negative relative to a neutral position? Prior to take-off at full power it was 6 or 7 and then gradually it goes down to 2 or 3 as it climbs.

OK, so now I can further tweak Table 512 - I more or less expected that but I suppose I´ll have to look for more specific coordinates along the X (blade angle) and Y (advance ratio) axes of this
table. I know the numbers represent the resulting thrust, but why can they be negative? And moreimportantly, what am I looking for to find where it needs tweaking?

OK, I mustn´t worry about what it means because we will throw it away and re-build it anyway.
OH DEAR! AFTER ALL THAT WORK... but OK.
OK, so the power limitation and how it is achieved has been explained.
No problem, it´s neither a (1) RPM LIMITATION (no governor needed!) nor a (2) Manifold pressure limitation (no waste gate needed!).

This "virtually turbocharged" engine cannot be tuned to 267 Hp at 29.92 sea-level Manifold pressure. Although in the simulator you give full throttle, Maximum throttle is in reality only at about 70% because our virtual turbocharger has a critical altitude of 4300 ft, so Hp is at about 227 at sea-level, and can´t be tested for 267 Hp at 500 ft.

The manifold pressure setting is at present at 31.6, and by reducing throttle to get a 29.9 MP
reading, power goes down from 228 to 208 Hp during climb or from 242hp and 1173 RPM at 73 kt to 221 hp at 1139 RPM at 71 kt during level flight - All this at sea-level, i.e. 250 ft altitude... and, at 500 ft, we have:
1173 RPM
243 Hp
-2.25 pitch.

This may not be exactly what you mean, but perhaps the data is useflul...

Anyway, as neither case (1) nor case (2) apply, do Torque and Friction adjustments still apply?
Well, it seems to be working better in principle, with the new Table 512.
1.- Propeller Diameter: 14 ft. but the setting in the .air file is 11.2 ft.
2.- Engine reduction gear ratio is 1:1 (direct drive).
3.- The propeller has 2 Blades
4.- Blade chord: see photo. I suppose they are quite wide.
I entered a fixed-blade setting for 25 degrees, but for the moment it´s using constant velocity
propellers. I´ll have a go at idle fine-adjustments in the mean time.

Definitely very interesting stuff indeed! Thank you... again...
Cheers for now,
Aleatorylamp

 

[aleatorylamp]

The kicker

Hi Ivan,
Just when one thinks it´s getting better, comes the kicker!
The constant velocity propeller was inadvertedly limited in the .air file with a minimum of 23 degrees instead of 15 or 5, and when I corrected it, everything changed - of course.
All the results I was getting that seemed to coincide with the theory went haywire.

Idle went up to 770 rpm, Sea-level Hp rose to 294, RPM rose to 1480, and at rated 4300 ft altitude now RPM is almost OK at 1456 but Hp is at too high at 305.

OK, so now it may make sense to reducethe MP setting to 29.92 and see what happens - it´s this, all slightly lower: 1459 RPM, 275 Hp at sea-level and 1456 RPM and 285 Hp at 4300 ft. Perhaps this is what was to be expected at 29.92 MP - I don´t know.

Probably this the correct moment to further move Table 512´s columns one more position to the right.

Well, now I´ll have to re-study the situation and I should edit the posts to correct misleading information, perhaps.

Cheers,
Aleatorylamp

 

[aleatorylamp]

Corrected test results

Hi Ivan,

Here is corrected information for results with Table 512 columns moved 1 position to the right:
Tests with the correct constant speed propeller and with Manifold Pressure parameter setting at 29.92
in the .air file, as you suggested. This was impossible with the faulty constant speed propeller I had before! Sorry...

Sea-level: MP 29.2 to get 267 Hp (Full throttle gives 275 hp), RPM=1456
4300 ft : MP 28.3 to get 267 Hp (Full throttle gives 285 hp), RPM=1456

I did another set of tests with Table 512 columns moved 2 positions to the right, but the results were the same, only the speed was 1 kt. slower.

I hope this makes some sense now. It makes less sense to me, but it seems more like what you expected, I believe.
Cheers,
Aleatorylamp.

 

[Ivan]

Ways to Cheat

Hello Aleatorylamp,

You sure have been busy!
A lot of what you are hitting is what I was trying to warn you about: You are working too many inter related variables all at once and each time you change one thing, the side effects mess other things up.

I suppose it is worth commenting that superchargers dont quite work the way you think they do.
Yes, the Mustang might have 60 inches Manifold pressure available at 15000 feet (or whatever altitude), but it ALSO has 60 inches MP at Sea Level! The Hurricane also has full boost at SL. Your aeroplane doesn't quite behave that way.
It must still be either Case 1 or Case 2 that I described earlier. Engine damage is simply not implemented here.
The rise in HP at intermediate altitudes is real, but it isn't very much up to 4300 feet. If critical altitude were 25000 feet, there would be much more of a rise as I described with the JuMo 213.

I also did some experimenting tonight and will cover it in the next post.

 

[Ivan]

Ways to Cheat Explained

I started off with my own FokkervEindecker for my testing. I tried the Zeppelin, but wanted something that was more agile and responsive to autopilot.

I first tried to set something like 27 inches MP at 4300 feet because that is what you get with a normally aspirated engine.
That didnt work because I was still getting 29.9 inches MP at SL even tho I set it for 21 inches. horsepower at SL was 312 or so which is pretty close to the expected 307 HP.
I was getting 269 HP at 4325 feet and 1450 RPM in both altitudes.

Here's the Cheat....

I thought about it a bit and figure since this is purely Engine Development, I can throw any old prop I want on it just to the power curve I am trying to tune. Since Diameter is a huge factor and easy to factor out of the Power Coefficient AND also easy to tune, I adjusted it until I was getting full 1450 RPM without the angle limits interfering.

Next step was to put a spread between the SL power and the 4300 foot power. This is hard because there isn't much difference in altitude. To do this, I adjuster the prop diameter until I was barely getting 25 degrees with a Constant Speed propeller at 4300 feet.
At a lower altitude, the prop would lug a bit and achieve both lower RPM and lower power. I also had to drastically increase the drag to hit only about 85 MPH at 4300 feet. 73 knots is 84 MPH.
As soon as I changed the lower pitch limit to 25 degrees, I got the power reduction I was expecting.

At this point I could also tune the Idle speed which is done wth Throttle Effectivity and Torque.
Here is what I have as of tonight:


Propeller Diameter is 8.0 feet
Propeller Pitch 25 degrees
Engine Idle Speed 412 RPM
229 HP at 1348 RPM at 50 feet above Sea Level
252 HP at 1449 RPM at 4325 feet above Sea Level.

I believe I can still get a bit closer by adjusting the Friction Table and fine tuning the Torque Table.
Although I am very certain I can get pretty close to the documented power levels, the Torque Curve and Friction Curve of this engine will look quite weird with high numbers near Idle and Maximum RPM but with a big dead spot just under Max RPM.

I am definitely learning something from this exercise....
Good Night.
- Ivan.

 

[aleatorylamp]

Ways to cheat

Hi Ivan,

Thanks for the info and effort! Very interesting results. Looks like we are getting closer, and I´m glad to hear you are enjoying it and finding it interesting. For a moment with all my mistakes I was fearing it could be exasperating for you, but I see this is not the case. Good job!

Yes, there is a comment in my documents as to the suddenness of full power being available at the rated altitude with these engines. Although 3 barriers were there to stop the throttle lever at different altitudes (I suppose it was proportional thirds), nevertheless at 4300 ft, full power was suddenly available. I had put it down to the mechanical division of having 3 barriers. With 5 it would have been more progressive, and with only one, much more sudden, perhaps. I suppose when you say there´s a hole, that´s the effect.

Incidentally, I´ve just tried out your Eindecker - I´d downloaded it a while ago but with all this Giant engine stuff only remembered today. It is a beautiful piece of work, and certainly gives the feel that flying this aircraft was reputed to have. Nimble, agile, and manoueverable! I remember re-working the Parasol version of this plane with the cantilever wing for FS98 with the Oberusel rotary engines. I see you also like doing the rotary engine animation. Great stuff!

The feeling of fascination that I get when I investigate all this old technology and then try it out on the simulator, is that so much inventiveness was necessary and so much risk was involved, that it was admirable how these people managed to fly with the technology, materials and knowledge available at the time - not only the Germans, but all the pioneers. Much of their stuff had to be handicrafted...

OK, then! We do seem to be getting somewhere!
Cheers,
Aleatorylamp

 

[Ivan]

Big Zeppelin Engines

Hello Aleatorylamp,

The Big Zeppelin Engine has finally finished bench testing. Next step is to fit a big wooden propeller to it and see how it works in hauling around a Giant Aeroplane.

Things pretty much worked out as I expected with tuning the Friction and Torque curves.
Friction is not changed much from the stock P-51D other than adjustment of the maximum RPM,
Interesting thing is that I forgot to do this for the Eindecker but it didn't seem to have much effect.
We NEEDED some fine tuning here to put in the "Big" drop in torque at around 1300 RPM.

I employ some pretty good aircraft mechanics in my workshop and although I am not always sure what they are doing, they like to prove themselves by always tuning their engines for a couple horsepower over the specifications or slicking down their airframes for a couple MPH over what may have been achieved on the real aeroplane.

Idle speed is now 410 RPM and the mechanics say they can bring it down well under 400 RPM if you want, but you need to get a good propeller before actually doing that tuning.

Some other mechanics are busy laminating big sheets of wood in preparation for carving and balancing a 14 ft propeller.

Attached are some screenshots showing the numbers we are getting.
The 50 foot and 4325 foot shots are there for obvious reasons. The other shot is to show that the HP does not continue to rise much above 4300 feet altitude.

The mechanics figure that 227 HP at 50 feet probably would drop by one or two if corrected back down to Sea Level.
It is rather hard to find a place that allows flight exactly at Sea Level.

Next Step is Record 512.
Hope my theory there is good.

- Ivan.

 

[aleatorylamp]

Big new engine

Hi Ivan,

Sounds great! Your mechanics are very diligent indeed, and have achieved interesting results. Thanks for the report.

Here in our shed in the back yard the apprentices just unpacked the big new shiny HC Zeppelin engine, and with an old propeller from the scrapyard next door they gingerly tried it, but are telling me now that they prefer to wait until the new propeller arrives before continuing trials with it.

At the moment they´re experimenting on an old second-hand engine they re-built from parts they got from scrapyard, and are trying out different settings for manifold pressure, boost-gain and suchlike for different sized props they managed to find somewhere. I told them not to make too much of a mess in the shed.

Let´s see if they make any headway!
Cheers,
Aleatorylamp

 

[Ivan]

Propellers

My folks are having a great deal of difficulty working in Laminated Wood. The first try ended up as a mess of splinters but they have no idea why things didn't work.

I would suggest that your guys go ahead and mount the Zeppelin Engine they received. It will at least give them an idea of the general level of flight performance and handling they can expect and perhaps there is other tuning that they may wish to do.

My guys put a low pitch stop at 25 degrees, but if your fellows are working with the engine, they may want to remove that stop and even trim down the propeller blades some more so that the engine possibly choose either a coarser or finer pitch than 25 degrees. In that way, they can get a real measure of the engine power curves which my mechanics didn't do.
My mechanics were only going for Idle RPM and Full Throttle. Your guys might want to check for part throttle and low RPM operation.

Basically what you have at the moment is a big 6 cylinder Zeppelin engine swinging a 4 blade P-51 Mustang Propeller that has been cut down from 11 feet to 8 feet. The performance that you get won't be dependent on anything I am still working on.

The Pieces in the AIR file you are looking for are:
Record 330 - Propeller Type - I didn't modify anything here and it might be wrong.
Record 500 - General Engine Parameters
Record 505 - CFS Engine Parameters
Record 506 - Throttle Efficiency
Record 507 - Fuel - Air Mixture - I didn't modify anything here.
Record 508 - Engine Torque versus RPM
Record 509 - Engine Friction versus RPM
Record 510 - Propeller Parameters
Record 511 - Propeller Efficiency - I didn't modify anything here but you should to tune performance.
Record 512 - Propeller Power Coefficient - Am working on this one.

Also you might want to adjust Drag Coefficient in Record 1101 to get the proper maximum speed.
I would also suggest setting up parameters for and enabling autopilot to make testing easier.
It isn't easy holding direction and altitude while watching gauges change.

BTW, it is also possible that my guys won't figure out the big wooden propeller thing for a while if ever.

- Ivan.

 

[aleatorylamp]

New Engine

Hi Ivan,

The apprentices mounted the new engine on a neighbour´s EindeckerE3 (I don´t know how they managed with the size... but they did it!) and I tried it without tweaking anything. Having more than double the power of the Oberusel, it is certainly nothing to laugh at - it climbs like a hotrod!!

Anyhow, it´s amazing how engine performance is very close to what would be expected on the Giant. I think that any tweaking I will do, will first be on the EindeckerE3 - the maximum performance at 4300 is slightly high for my liking, and I think I´ll reduce slightly to spec. as it´s a max. continuous, but that will be no problem, I expect.

Now, the apprentices are mounting the engine on the Giant for trials, and for the moment, they haven´t a clue what´s going on - obviously the Eindecker propeller will not be of any use, and the type they have on the other 3 Giant engines, is a bit off, but they don´t know why... Some are still inspecting the chord on other propellers to see where they can start sanding, and others can´t stop taking turns flying the Eindecker - and they can hardly believe how it works so well!

I´ll re-read the recent posts and see if I can come up with an idea.
For the moment anyway, it´s really a great start with the new engine - thanks a lot!

More later.
Cheers,
Aleatorylamp

 

[aleatorylamp]

4 new engines on the Giant!

Hi Ivan,
We´re just having a party here in the shed with the apprentices. Their tutor had promoted them to 3rd class air mechanics for the successful Eindecker trials. After that, they installed and adjusted it on the Giant with the other 3 new engines. They followed all the instructions and specifications and adjust everything by the book, even the torque and friction sections. Then, for want of a decent propeller, they made three more identical ones to one they used with the Eindecker trials - and it worked so well that their tutor immediately promoted them to air mechanices 2nd class! The 4 engines together worked with no excess power or RPM, presumably due to the Giant´s lumbering weight and speed. The next step will be fine adjusments to squeeze out 11 rpm, 2 Hp and 2 Kt. The´ll look into the turbocharger first, I think. Here´s the report:

Engine Idle: 411 RPM
Open throttle flight:
Sea Level, MP 29.9
- level flight: 1356 rpm, 237 hp, 70 kt
- moderate climb: 1270 rpm, 220 hp, 54 kt
4300 ft, MP 29.4
- level flight; 1439 rpm, 265 hp, 71 kt.

So, this is really something to celebrate! Thank your engineers and specialized mechanics!!
Cheers,
Aleatorylamp

 

[papingo]

papingo........

this is all very interesting stuff.
in fact I have my old af99 files
out again.due to Ivans P38 stuff
dear mr aleatorylamp your text
appears as mid-grey writing on
light grey background.....
so its hard to read!
I'm currently looking into dp.files
which can be hard to follow
>>papingo

 

[aleatorylamp]

text colours and Dp files

Hello, Papingo, nice to hear from you.

In case the colour problem spreads to your AF99: In the blueprint window (or your greyprint..!!) there is a little menu at the top where the Color option brings down a window which will allow you to change the colours of things.

However, I fear you mean something else, don´t you?

Seeing you´re working on Dp files, I was wondering... perhaps you´d be interested in tweaking the Dp files for the Giant biplane I´m preparing for upload. The model is finished, and the .air file, almost. I could send you the plane by e-mail, if you like.

Kind regards,
Aleatorylamp

 

[Ivan]

Default Screen Colours

Hello Papingo,
Glad to see you again.
I believe Aleatorylamp's posts might always be using the same colour font and do not adjust to the display scheme.
I use the SOH default (Light Blue / White) so everything looks fine. Those selections are on the lower left of your screen if you scroll all the way down.

I was also working on DP files for the Lightning before this Big Zeppelin Engine diversion.
It seems like a worthwhile diversion because I believe I actually learned quite a lot in doing this project and some of that new knowledge will most likely transfer to other projects.

What kind of Aeroplane is your DP file for? I have collected a fair amount of data on WW2 Aircraft Guns that might be helpful to you. If it is something like the Big Zeppelin, I won't be as much help because their armament at the time was most likely just a bunch of 7.92 mm MGs and there isn't much argument about the hitting power of those guns. Ammunition weight might be a bit debatable though because guns of that era didn't use disintegrating link belts.

- Ivan.

 

[Ivan]

Big Wooden Propellers

Hello Aleatorylamp,

I have some good news and some bad news for you.

First, the Good News:
My mechanics found an old German wood worker who claims to have actually flown during the Great War. He helped us out a bit with the glue formulas and a bit on the carving and now we have a serviceable though not necessarily optimal 14 foot propeller for the Giant Zeppelin. It survived flight testing fine but my mechanics didn't spend the time polishing or contouring the blades beyond what was absolutely necessary for the test flights.

Next, The BAD News:
The reason why my initial tries at the Big Wooden Propeller didn't work is because I did not take into account the HUGE change in Advance Ratio with a change from 8 feet to 14 feet in propeller diameter. It is proportional as you might expect but it was a factor I neglected.
The side effect is that with the Advance Ratio now much lower than before, the Propeller Thrust is also much lower than it was before. It is roughly 2/3 of the original value.
If you don't want to fiddle with the necessary adjustments, just edit Record 511 for Propeller Efficiency. An alternative is to adjust the Drag downward by a lot, Your choice might be determined by where your climb rates are currently. Are they too low or too high?

8 Foot Propeller Advance Ratios:
0.0 - Zero MPH as you would expect
0.2 - 26 mph
0.4 - 53 mph
0.6 - 79 mph <-- Our Target Speed is 85 mph which is just a little above this.
0.8 - 105 mph

14 Foot Propeller Advance Ratios:
0.0 - Zero MPH (The only thing that DIDN'T Change.)
0.2 - 46 mph
0.4 - 92 mph <-- Our Target Speed is 85 mph which is a little BELOW this value.
0.6 - 138 mph

Note that Advance Ratio is based on TRUE Airspeed, so does not vary with altitude.
What this means is that while we were using the Prop Efficiency for 0.6 Advance Ratio earlier, we never get above 0.4 Advance Ratio now.

It is still possible with a few adjustments to get a reasonable level of performance as can be seen by the screenshots attached. Check your email soon.

- Ivan.