New Version of MotoCalc!

[stefanv]

Capable Computing, Inc. is pleased to announce that MotoCalc version 7 is now available!

Version 7 adds many exciting new features, including:

Smarter, faster MotoWizard.
Wiring Wizard to help with multi-motor setups, and even generate a wiring diagram.
Single-click update of the entire database.
Side-by-side comparison of different results.
Sharing of user-contributed data.
Parallel cells and/or speed controls.
Over 850 motors and 100 cell types.

The upgrade is a free download (or $10 for disks) for registered users. And if you're new to MotoCalc, you can try it free for 30 days.

For more details, visit www.motocalc.com.

Stefan Vorkoetter
Capable Computing, Inc.

[blfinche]

I install and am running it on Windows 2000, but I can't change the size of the main window. It has vertical and horzontal scroll bars.

Bobby

[stefanv]

Are you running windows in a "large-fonts" mode? What is your screen resolution. The window should just come up the correct size. When you were using version 6, did you have to resize the MotoCalc window?

Stefan

[Mitch G]

I just downloaded the v7.0 and it looks good.
First of all, thanks for making the update free for existing Motocalc users. Most companies would charge for an upgrade like this.

I like how lipolies have been added, and I also like the comparison screen.

Finally, it seems that motowizard is a bit smarter now. At least it thinks more like me. It now suggests a setup I'm using quite successfully. :)


Mitch

[mluniewicz]

I too cannot resize the window. I don't believe I had to resize the window for version 6. I'm running Windows XP Home.

- matt

[boomerace]

Good Job! I am very pleased!!:D
boomer

[Patrick Plawner]

Love it, Love it, Love it, Love it, Love it, Love it, Love it, Love it, Love it, Love it, Love it, Love it, Love it, Love it, Love it, Love it !!!


The "Shared" data will be the biggest hit !!!! just wait few weeks.

The parallele stuff is also very smart. I am playing with it more than ever now :)

Great product !

[stefanv]

Thanks for all the kind words!

Regarding window sizes:

Some of the windows are slightly larger than they were in version 6, to make room for more stuff.

Unfortunately, we introduced a bug that made the window sizing possibly get mixed up if you were running in Windows "large fonts" mode. We've since fixed that bug. Any of you that have installed version 7 and have this problem, please download the update again, and re-install it, and things should work fine.

Sorry for the inconvenience.

Stefan

[Martin Hunter]

Thanks for the update, Stefan! I'm really digging the comparison window.

Martin

[Patrick Plawner]

Noted that when using the wiring wizard, it does not allow 2 brushless motors, in parallele, with only 1 ESC

[William A]

Very nice Stefan,

Question, once 7 is installed, OK to uninstall 6 without destroying my registered status ?

[stefanv]

Patrick:

Yes, that is correct. Although this will work with some speed controls and some motors, it's not really a reliable way to do things. See this month's "Lunch with Keith" on the E-zone.

William:

Yes, once you've got version 7 up and running, you can uninstall version 6 without fear of losing your registration.

Stefan

[tim hooper]

Thanks stefan!

tim

[stefanv]

I've just put out MotoCalc 7.01, which fixes the few problems that people have been reporting. Specifically:


There was a bug in the Contributed Data Browser window. When you clicked the Add Checked Items to MotoCalc button, the items in the last tab in which you selected things would not be added, unless you changed to a different tab first.
Contributing an airframe if you were running in Metric with Prop Sizes in Inches mode would result in the wingspan not being converted to inches. Other users downloading that airframe would then get a wing span 2.54 times larger than it should be. This is now fixed.
There were a number problems in the display of various parts of MotoCalc when Windows was running in "Large Fonts" mode. These have been fixed, and MotoCalc works as well in this mode as it does in the standard "Small Fonts" mode.


Please see http://www.motocalc.com/motoupdt.htm for information on how to download and install the update.

Stefan

[Patrick Plawner]

Quick turnaround, well done !

[Patrick Plawner]

you need to add ".htm" at the end.

[stefanv]

Fixed it (I had forgotten the .htm).

Thanks for your quick turnaround. I know who's going to be on my beta tester list next time. :)

Stefan

[Neil Stainton]

MotoCalc 7 is very impressive Stefan. Thanks for making the upgrade available free. I particularly like the additon of gearbox efficiency to the calculations, though I am sure that I will appreciate the other new features, as I learn to use them. The wiring diagram is a programming tour-de-force!

Well done & thanks again,

Neil.

[FAA]

Please not the following descrepancies between versions ^.05 and the new Ver 7.00

Here is my Magic 3D in Version 7:

---------------------------------------------------------------------------------
MotOpinion - Magic 3D
100ft above Sea Level, 29.92inHg, 50°F

Motor: Jeti Phasor 30-3; 1200rpm/V; 2.8A no-load; 0.034 Ohms.
Battery: Sanyo CP-2400SCR; 10 cells; 2300mAh @ 1.2V; 0.0053 Ohms/cell.
Speed Control: Generic Brushless ESC; 0.006 Ohms; High rate.
Drive System: Magic; 15x10 (Pconst=1.11; Tconst=0.95) geared 2:1 (Eff=95%).
Airframe: Magic 3D; 725sq.in; 63.8oz; 12.7oz/sq.ft; Cd=0.048; Cl=0.22; Clopt=0.45; Clmax=0.94.
Stats: 92 W/lb in; 67 W/lb out; 18mph stall; 26mph opt @ 58% (20:03, 86°F); 38mph level @ 80% (10:34, 104°F); 1312ft/min @ 34.5°; -343ft/min @ -8.5°.

Possible Power System Problems:

The steady-state battery temperature at the hands-off cruise airspeed and throttle setting (approximately 178°F) is higher than the suggested maximum temperature for this cell type (140°F), which can result in battery pack damage. A lower current would decrease the battery temperature.
Current can be decreased by using fewer cells, a smaller diameter or lower pitched propeller, a higher gear ratio, or some combination of these methods.

Power System Notes:

The full-throttle motor current at the best lift-to-drag ratio airspeed (35.8A) falls between the motor's maximum efficiency current (25.1A) and its current at theoretical maximum output (113.7A), thus making effective use of the motor.

Aerodynamic Notes:

The static pitch speed (46mph) is within the range of approximately 2.5 to 3 times the model's stall speed (18mph), which is considered ideal for good performance.
With a wing loading of 12.7oz/sq.ft, a model of this size will have very sedate flying characteristics. It will be suitable for relaxed flying, in calm or very light wind conditions.
The static thrust (63.8oz) to weight (63.8oz) ratio is 1:1, which will result in very short take-off runs, no difficulty taking off from grass surfaces (assuming sufficiently large wheels), and steep climb-outs.
At the best lift-to-drag ratio airspeed, the excess-thrust (36.2oz) to weight (63.8oz) ratio is 0.57:1, which will give steep climbs and excellent acceleration. This model should be able to do consecutive loops, and has sufficient in-flight thrust for almost any aerobatic maneuver.

General Notes:

This analysis is based on calculations that take motor heating effects into account.

-----------------------------------------------------------------------------------


Here it is in version 6.05

-----------------------------------------------------------------------------------

MotOpinion - Madic 3D
100ft above Sea Level, 50°F

Motor: Jeti Phasor 30-3; 1200rpm/V; 0.034 Ohms; 2.8A idle.
Battery: Sanyo CP-2400SCR; 10 cells; 2300mAh @ 1.2V; 0.0053 Ohms/cell.
Speed Control: Generic Brushless ESC; 0.006 Ohms; High rate.
Drive System: Magic; 15x10 (Pconst=1.11; Tconst=0.95) geared 2:1.
Airframe: Magic 3D; 725sq.in; 63.8oz; 12.7oz/sq.ft; Cd=0.048; Cl=0.22; Clopt=0.45; Clmax=0.94.
Stats: 89 W/lb in; 69 W/lb out; 19mph stall; 27mph opt @ 59% (20:27); 39mph level @ 81% (11:01); 1340ft/min @ 34.3°; -352ft/min @ -8.5°.

Power System Notes:

The full-throttle motor current at the best lift-to-drag ratio airspeed (33.9A) falls between the motor's maximum efficiency current (25.5A) and its current at maximum output (117.5A), thus making effective use of the motor.

Aerodynamic Notes:

The static pitch speed (47mph) is within the range of approximately 2.5 to 3 times the model's stall speed (19mph), which is considered ideal for good performance.
With a wing loading of 12.7oz/sq.ft, a model of this size will have very sedate flying characteristics. It will be suitable for relaxed flying, in calm or very light wind conditions.
The static thrust (63.8oz) to weight (63.8oz) ratio is 1:1, which will result in very short take-off runs, no difficulty taking off from grass surfaces (assuming sufficiently large wheels), and steep climb-outs.
At the best lift-to-drag ratio airspeed, the excess-thrust (35.6oz) to weight (63.8oz) ratio is 0.56:1, which will give steep climbs and excellent acceleration. This model should be able to do consecutive loops, and has sufficient in-flight thrust for almost any aerobatic maneuver.

General Notes:

This analysis is based on calculations that take motor heating effects into account.

---------------------------------------------------------------------------------

[FAA]

Here is my Modeltech Me-109

Ver. 7.0
------------------------------------------

MotOpinion - Me-109 Mega20-30-3
100ft above Sea Level, 29.92inHg, 50°F

Motor: Mega AC 22/30/3; 1350rpm/V; 1A no-load; 0.032 Ohms.
Battery: Sanyo CP-2400SCR; 10 cells; 2300mAh @ 1.2V; 0.0053 Ohms/cell.
Speed Control: Generic Brushless ESC; 0.006 Ohms; High rate.
Drive System: Me-109 Drive Mega; 9x6 (Pconst=1.31; Tconst=0.95) direct drive.
Airframe: ME-109 Global; 360sq.in; 64.9oz; 26oz/sq.ft; Cd=0.055; Cl=0.47; Clopt=0.67; Clmax=1.24.
Stats: 90 W/lb in; 75 W/lb out; 23mph stall; 31mph opt @ 53% (24:37, 65°F); 37mph level @ 61% (18:35, 68°F); 1099ft/min @ 23.9°; -279ft/min @ -5.9°.

Power System Notes:

The full-throttle motor current at the best lift-to-drag ratio airspeed (37A) falls between the motor's maximum efficiency current (15.9A) and its current at theoretical maximum output (127.6A), thus making effective use of the motor.

Aerodynamic Notes:

The static pitch speed (64mph) is within the range of approximately 2.5 to 3 times the model's stall speed (23mph), which is considered ideal for good performance.
With a wing loading of 26oz/sq.ft, a model of this size will have a very high flying speed, requiring the undivided attention of an expert pilot. The high weight will provide good penetration, even in strong winds.
The static thrust (43.2oz) to weight (64.9oz) ratio is 0.66:1, which will result in short take-off runs, and no difficulty taking off from grass surfaces (assuming sufficiently large wheels).
At the best lift-to-drag ratio airspeed, the excess-thrust (27oz) to weight (64.9oz) ratio is 0.42:1, which will give steep climbs and excellent acceleration. This model should be able to do consecutive loops, and has sufficient in-flight thrust for almost any aerobatic maneuver.

General Notes:

This analysis is based on calculations that take motor heating effects into account.

------------------------------------------------------------------------

Ver 6.05

--------------------------------------------------------------------------


MotOpinion - Me-109 Mega20-30-3
100ft above Sea Level, 50°F

Motor: Mega AC 22/30/3; 1350rpm/V; 0.032 Ohms; 1A idle.
Battery: Sanyo CP-2400SCR; 10 cells; 2300mAh @ 1.2V; 0.0053 Ohms/cell.
Speed Control: Generic Brushless ESC; 0.006 Ohms; High rate.
Drive System: Me-109 Drive Mega; 9x6 (Pconst=1.31; Tconst=0.95) direct drive.
Airframe: ME-109 Global; 360sq.in; 64.9oz; 26oz/sq.ft; Cd=0.055; Cl=0.47; Clopt=0.67; Clmax=1.24.
Stats: 89 W/lb in; 74 W/lb out; 23mph stall; 32mph opt @ 54% (24:27); 38mph level @ 62% (18:40); 1081ft/min @ 22.8°; -287ft/min @ -5.9°.

Power System Notes:

The full-throttle motor current at the best lift-to-drag ratio airspeed (35.9A) falls between the motor's maximum efficiency current (16.1A) and its current at maximum output (130.1A), thus making effective use of the motor.

Aerodynamic Notes:

The static pitch speed (65mph) is within the range of approximately 2.5 to 3 times the model's stall speed (23mph), which is considered ideal for good performance.
With a wing loading of 26oz/sq.ft, a model of this size will have a very high flying speed, requiring the undivided attention of an expert pilot. The high weight will provide good penetration, even in strong winds.
The static thrust (42oz) to weight (64.9oz) ratio is 0.65:1, which will result in short take-off runs, and no difficulty taking off from grass surfaces (assuming sufficiently large wheels).
At the best lift-to-drag ratio airspeed, the excess-thrust (25.8oz) to weight (64.9oz) ratio is 0.4:1, which will give strong climbs and rapid acceleration. This model will most likely readily loop from level flight, and have sufficient in-flight thrust for many aerobatic maneuvers.

General Notes:

This analysis is based on calculations that take motor heating effects into account.

-----------------------------------------------------------------------------

[FAA]

It is clear that the Current (A) calculation algorithim for 6.05 is more accurate, given that it is within 1 A (typically) of actual values.

In fact, I have always been amazed how closely 6.05 calculates current, to actual values.

Version 7 is pushing this error even higher !

I have tried 6 more models and they are all consistently higher. In fact they are all between 1 to 2 amps higher !

That makes 8 models that I have run so far and all have higher errors in them.

Can some other people out there run some "known" models to see if my results match with others ?



Nick

[FAA]

Well ,

I ran the numbers for my Bandit FVK Hotliner.

Results are as confusing as ever between the two versions:

Version 6.05:

-------------------------------------------------

MotOpinion - Bandit Hotliner
100ft above Sea Level, 50°F

Motor: Hacker B40 14S; 3043rpm/V; 0.0287 Ohms; 0.95A idle.
Battery: HR-4/5FAUP; 10 cells; 1950mAh @ 1.2V; 0.005 Ohms/cell.
Speed Control: Generic Brushless ESC; 0.006 Ohms; High rate.
Drive System: Bandit prop; 14x9.5 (Pconst=1.18; Tconst=0.995) geared 4.4:1.
Airframe: Bandit Hotliner; 372sq.in; 54.5oz; 21.1oz/sq.ft; Cd=0.046; Cl=0.25; Clopt=0.59; Clmax=0.94.
Stats: 112 W/lb in; 92 W/lb out; 24mph stall; 30mph opt @ 52% (32:48); 47mph level @ 78% (13:51); 2191ft/min @ 54.8°; -298ft/min @ -6.4°.

Possible Power System Problems:

The steady-state motor temperature at the best lift-to-drag ratio airspeed (213°F) is very high, which will significantly affect efficiency and motor longevity. A lower current would decrease the temperature.
Current can be decreased by using fewer cells, a smaller diameter or lower pitched propeller, a higher gear ratio, or some combination of these methods.

Power System Notes:

The full-throttle motor current at the best lift-to-drag ratio airspeed (37A) falls between the motor's maximum efficiency current (15.5A) and its current at maximum output (127A), thus making effective use of the motor.

Possible Aerodynamic Problems:

The static pitch speed (51mph) is less than 2.5 times the stall speed (24mph), which may result in reduced performance at typical flying speeds and a low maximum speed. This situation is usually acceptable for an electric sailplane or other slow-flying model.
Pitch speed can be increased by using a higher pitched and/or smaller diameter propeller, a lower gear ratio, a higher cell count, or some combination of these methods.

Aerodynamic Notes:

With a wing loading of 21.1oz/sq.ft, a model of this size will have flying characteristics suited to an experienced pilot. The plane will fly fast, and be readily able to handle fairly strong winds.
The static thrust (70.6oz) to weight (54.5oz) ratio is 1.3:1, which will result in extremely short take-off runs, no difficulty taking off from grass surfaces (assuming sufficiently large wheels), and vertical climb-outs. This model will probably be able to perform a hover or torque roll.
At the best lift-to-drag ratio airspeed, the excess-thrust (43.1oz) to weight (54.5oz) ratio is 0.79:1, which will give very steep climbs and incredible acceleration. This model can easily do consecutive loops, and has sufficient in-flight thrust for any aerobatic maneuver.

General Notes:

This analysis is based on calculations that take motor heating effects into account.

--------------------------------------------------------------


Version 7.01 FOR THE EXACTLY IDENTICAL PARAMETERS

------------------------------------------------------

MotOpinion - Bandit Hotliner
100ft above Sea Level, 29.92inHg, 50°F

Motor: Hacker B40 14S; 3043rpm/V; 0.95A no-load; 0.0287 Ohms.
Battery: HR-4/5FAUP; 10 cells; 1950mAh @ 1.2V; 0.005 Ohms/cell.
Speed Control: Generic Brushless ESC; 0.006 Ohms; High rate.
Drive System: Bandit prop; 14x9.5 (Pconst=1.18; Tconst=0.995) geared 4.4:1 (Eff=95%).
Airframe: Bandit Hotliner; 372sq.in; 54.5oz; 21.1oz/sq.ft; Cd=0.046; Cl=0.25; Clopt=0.59; Clmax=0.94.
Stats: 120 W/lb in; 95 W/lb out; 24mph stall; 30mph opt @ 51% (31:49, 59°F); 45mph level @ 77% (12:50, 66°F); 2264ft/min @ 60.1°; -290ft/min @ -6.4°.

Power System Notes:

The full-throttle motor current at the best lift-to-drag ratio airspeed (40.5A) falls between the motor's maximum efficiency current (16.7A) and its current at theoretical maximum output (146.6A), thus making effective use of the motor.

Possible Aerodynamic Problems:

The static pitch speed (51mph) is less than 2.5 times the stall speed (24mph), which may result in reduced performance at typical flying speeds and a low maximum speed. This situation is usually acceptable for an electric sailplane or other slow-flying model.
Pitch speed can be increased by using a higher pitched and/or smaller diameter propeller, a lower gear ratio, a higher cell count, or some combination of these methods.

Aerodynamic Notes:

With a wing loading of 21.1oz/sq.ft, a model of this size will have flying characteristics suited to an experienced pilot. The plane will fly fast, and be readily able to handle fairly strong winds.
The static thrust (73.5oz) to weight (54.5oz) ratio is 1.35:1, which will result in extremely short take-off runs, no difficulty taking off from grass surfaces (assuming sufficiently large wheels), and vertical climb-outs. This model will probably be able to perform a hover or torque roll.
At the best lift-to-drag ratio airspeed, the excess-thrust (45.6oz) to weight (54.5oz) ratio is 0.84:1, which will give very steep climbs and incredible acceleration. This model can easily do consecutive loops, and has sufficient in-flight thrust for any aerobatic maneuver.

General Notes:

This analysis is based on calculations that take motor heating effects into account.


--------------------------------------------------------------------

Current draw calculations between the two program versions differ by 3.5 A ?????

Thats an 8.64 % Error just between the two programs !!!

Actual measured value on the model is 36 A !

Version 7.01 is showing an error from actual of 4.5 A

Version 6.05 is showing an error from actual of 1 A



So far Version 7.01 has yet to match any numbers that I have. Not even within the 3% error that you are saying Stefan.

Make sure folks that you keep your version of 6.05 BEFORE you install version 7.01 !!

You will want to do these checks yourselves, with known figures.

This is a total of 9 models that I have run so far and the new motocalc is giving me figures that are way off from actuals and higher than ver 6.05.

I would like you to give us some examples of data runs Stefan, like the ones I have posted here, that show comparisions between the two versions the you have performed

I am sure you must have done some verification and validation checks, like any other good engineer, during your checks. That would help me see what is going on here.

This is very frustrating.

Data don't lie and neither do actual results.

Nick

[stefanv]

It looks as if a problem may indeed have crept in. I've turned off all the things that I feel might affect this calculation, and there's still a difference. There was extensive testing of the results along the way, so I'm not sure how this went unnoticed, but nonetheless, it is there.

I will investigate further, fix, and report back.

Stefan

PS. Cross-posting to two threads only because the messages to which I'm responding have been cross-posted.

[FAA]

Thanks Stefan.

I will stop posting in the other thread, because this is probably the better forum for this discussion.

Nick

[opualuan]

I have notice an increase in amp accuracy with 7 on a mega 4 turn, worse with a miniac extreme in 7. something is up...

[stefanv]

MotoCalc 7.02 has just been made available at http://www.motocalc.com/motoupdt.htm

It includes a fix to the increased current problem described by FAA in numerous postings above. The problem turned out to be due to an error in, of all things, the air density calculations (it was making the air too dense, which makes the propeller harder to turn, and hence increases the current).

Stefan

[stefanv]

Please note that when a gearbox is involved, MotoCalc 7 will still give you slightly higher currents than MotoCalc 6, due to the gearbox efficiency (or rather, the less than 100% efficiency that MotoCalc 6 assumed).

Also, when brushless motors are involved, there will be a very slightly higher current in MotoCalc 7 due to the revised heating model used for brushless motors.

Neither of these increases are anywhere near the magnitude of those caused by the air density error that was fixed.

Stefan

[opualuan]

miniac extreme 6:1, 12.5x8 thin carbon folder, 2s2p etec 1200. 6.05 says 24.4A, 7.02 says 27A, similar rpm's.

actual benchtest was just under 24A. it went from VERY accurate to off by more than 10%...


on the other hand, my brushless picojet (3s2p tp2100, 6x4apc) went from 21.9 (6.05) to 22.6A (7.02). benchtest is 23.2A. rpm's were still close to actual.

why would the miniac be off by so much more?

[Neil Stainton]

I have a difficulty when trying to compare test runs & MotoCalc predictions - I assume MotoCalc will be modelling the operating point half way though a flight, with a warm/hot motor; but most of my testing is done with HOC packs (for repeatability) and cold motors (short test runs, longer top off recharges).

For this reason I never worry too much about getting MotoCalc to mirror reality exactly. Stefan, what is your advicer about test runs?

On the other hand I have recently been optimising the prop on a competition LMR model and comparing MotoCalc's rate of climb figure with actual ROCs captured by an ALTI2 altitude data logger, and have found it very accurate - ie within 5%. This is better than I would expect considering the number of unknowns.

Neil.

[Bill Glover]

Providing major upgrades like V7 free of charge to existing users is outstanding service, and much appreciated. Many thanks Stefan.

[FAA]

Stefan, First off "great response" !

I wish my software engineers would turn around revisions that quick.

Now to the issue at hand:

I ran the model cases for the FVK Bandit and my Modeltech ME-109. The reason for these two is that they represent a good combination since one is running a hacker B40-14S with a Maxon 4.4:1 gearbox and the other a direct drive Mega 20/30/3.


Here are the comparitive results for each Motocalc version so far, including actuals.
======================
FVK Bandit

V. 6.05 = 37 A
V. 7.01 = 40.5 A
V. 7.02 = 39.2 A
Actual = 36 A
-------------------------------
Errors between Actual and each version

V. 6.05 to Actual = 2.7 % (+1 A Error)
V. 7.01 to Actual = 11.11 % (+4.5 A Error)
V. 7.02 to Actual = 8.16 % (+3.2 A Error)
-------------------------------
Relative Errors between V.605 and 7.01 and 7.02

V. 7.01 to V. 6.05 = 8.64 % (+3.5 A Error)
V. 7.02 to V. 6.05 = 5.61 % (+2.2 A Error)

=======================

=======================
Modeltech ME-109

V. 6.05 = 35.9 A
V. 7.01 = 37 A
V. 7.02 = 36.6 A
Actual = 32.2 A
-------------------------------
Errors between Actual and each version

V. 6.05 to Actual = 10.3 % (+3.7 A Error)
V. 7.01 to Actual = 12.97% (+5.2 A Error)
V. 7.02 to Actual = 12.02% (+4.4 A Error)
-------------------------------
Relative Errors between V.605 and 7.01 and 7.02

V. 7.01 to V. 6.05 = 2.97 % (+1.1 A Error)
V. 7.02 to V. 6.05 = 1.91 % (+0.7 A Error)

=======================


I hope this helps others with their evaluation.

From what I can see, version 7.02 that Stefan released has addressed the error conditions for the direct drive case (as shown in the numbers for the ME-109). The ME-109 always had a higher error between calculated and actual, that is why the relative errors between versions is more of an indicator than anything else.

For the FVK Bandit with the gearbox, things are still a bit off. There was a clear improvement of 3% in the calculation between versions 7.01 and 7.02, so things have definetly gotten better.

The strange thing in all for this, is that in 10 models that I ran so far in versions 6.05, 7.01 and 7.02, version 6.05 is producing results that are much closer to the real world.

This is probably frustrating to you Stefan, because I am sure that you spent a lot a time and energy into making this a better product.

Having done much work in the Avionic simulation design areas for years and having authored numerus papers on the topic, it reminded me of the fact that a more robust modeling scheme, just adds further complexity errors, that can add up and manifest themselves in areas or within variables least expected. So, in the end, the model you "thought" would produce higher fidelity and better resolution falls victim to Chaos Theory and has the opposite effects.

Simulation and modeling is a tricky world.

I am sure as time goes on, you will probably be able to pin down the issues that are causing this.

Great effort on your behalf and cudos on your quick turn around.

Nick

[rpage53]

I'm seeing an anomaly with the zero speed battery temperature in OPINION. It warns that that KAN1050's will overheat at 6A but the warning disappears at 8A and doesn't even reappear over 20A. They presumably would be hot then.

Rick.

[stefanv]

Odd. Can you send me the project (using Copy Project from the Projects menu, and then pasting that into an e-mail).

Thanks, Stefan
stefan@capable.ca

[Jim Taylor]

I downloaded Motorcalc for a trial, and maybe I don't know how to use it, but I really don't understand the battery temperature warnings. In my Switchback 3D and UrbanFlyer, both with GWS 300C-B and 9X7 prop. my 8 cell 720 AAA's only get warm, not hot, and certainly not 523 deg. F. I question some of the other data also, but as I said I may be doing something wrong.

Jim


MotOpinion - UrbanFlyer
Sea Level, 29.92inHg, 68°F

Motor: GWS GW/EPS-300C; 5313rpm/V; 1.6A no-load; 0.5 Ohms.
Battery: Sanyo 720AAA NiMH; 8 cells; 720mAh @ 1.2V; 0.04 Ohms/cell.
Speed Control: Castle Creations Pixie 20P; 0.0025 Ohms; High rate.
Drive System: GWS GW/EPS-300C-BS; 9x7 (Pconst=1.18; Tconst=0.995) geared 4.43:1 (Eff=95%).
Airframe: UrbanFlyer; 310sq.in; 14.9oz; 6.9oz/sq.ft; Cd=0.05; Cl=0.22; Clopt=0.46; Clmax=0.94.
Stats: 50 W/lb in; 15 W/lb out; 14mph stall; 20mph opt @ 77% (12:17, 154°F); 28mph level @ 101% (7:46, 203°F); 157ft/min @ 5.2°; -258ft/min @ -8.6°.

Possible Power System Problems:

The steady-state battery temperature at the hands-off cruise airspeed and throttle setting (approximately 523°F) is higher than the suggested maximum temperature for this cell type (122°F), which can result in battery pack damage. A lower current would decrease the battery temperature.
Current can be decreased by using fewer cells, a smaller diameter or lower pitched propeller, a higher gear ratio, or some combination of these methods.



MotOpinion - Switchback 3D
Sea Level, 29.92inHg, 68°F

Motor: GWS GW/EPS-300C; 5313rpm/V; 1.6A no-load; 0.5 Ohms.
Battery: Sanyo 720AAA NiMH; 8 cells; 720mAh @ 1.2V; 0.04 Ohms/cell.
Speed Control: Castle Creations Pixie 20P; 0.0025 Ohms; High rate.
Drive System: GWS GW/EPS-300C-BS; 9x7 (Pconst=1.18; Tconst=0.995) geared 4.43:1 (Eff=95%).
Airframe: Switchback 3D; 265sq.in; 12.4oz; 6.7oz/sq.ft; Cd=0.046; Cl=0; Clopt=0.39; Clmax=0.9.
Stats: 60 W/lb in; 18 W/lb out; 14mph stall; 21mph opt @ 79% (11:49, 157°F); 182ft/min @ 5.7°; -329ft/min @ -10.3°.

Possible Power System Problems:

The steady-state battery temperature at the best lift-to-drag ratio airspeed and throttle setting (approximately 264°F) is higher than the suggested maximum temperature for this cell type (122°F), which can result in battery pack damage. A lower current would decrease the battery temperature.
Current can be decreased by using fewer cells, a smaller diameter or lower pitched propeller, a higher gear ratio, or some combination of these methods.

[stefanv]

It looks like you've probably entered the airfoil information incorrectly. Notice that it is saying you need 101% throttle to maintain hands-off level flight. At that throttle setting (continously), you will cook your battery.

Can you e-mail me the project (using Copy Project from the Projects menu, and then pasting that into an e-mail). It's hard to tell if anything is going wrong just from reading the MotOpinion report.

Thanks, Stefan
stefan@capable.ca

[rpage53]

I emailed my project.
I wonder if there is an air pressure setting still working here on battery temperature. Do you consider cooling air from the prop blast? Wouldn't think so but that would fit the pattern.

Rick.

[stefanv]

Okay, I see what's happening. In the 7A scenario, the plane doesn't have enough power to maintain hands-off level flight. Thus, MotoCalc can't use that airspeed (and corresponding throttle setting) to compute the battery temperature. So instead, it computes the temperature at zero airspeed and full throttle.

In the 22A scenario, there is enough power for hands-off level flight, so MotoCalc computes the battery temperature at that speed and throttle setting. The battery current at that throttle setting is only 3.6A (the motor current is higher due to the transformer effect of the high-rate speed control and the motor windings).

I may change MotoCalc in the future to not compute the full-throttle battery temperature, and instead simply indicate that the model can't maintain hands-off level flight with that power system.

Stefan

[Jim Taylor]

Stefan, You're right, the UrbanFlyer airframe weight was to high. I've corrected it and here is the new data. The battery temperature still seems too high. The SwitchBack 3D data I posted before was using all downloaded data and the UF used all download data except for the airframe. I have an IR thermometer, but the batteries have never seemed hot enough for me to bother checking them. I'll check the battery temperature the next time out (if it ever quits raining). Maybe I don't understand the information presented but I would expect the hands-off cruise airspeed and throttle setting to be around 4-5 Amps which shouldn't produce 258 °F. I've emailed you the UF project data.

Jim

MotOpinion - UrbanFlyer
500ft above Sea Level, 29.92inHg, 80°F

Motor: GWS GW/EPS-300C (est); 4833rpm/V; 0.7A no-load; 0.214 Ohms.
Battery: Sanyo 720AAA NiMH; 8 cells; 720mAh @ 1.2V; 0.04 Ohms/cell.
Speed Control: Castle Creations Pixie 20P; 0.0025 Ohms; High rate.
Drive System: GWS GW/EPS-300C-BS; 9x7 (Pconst=1.18; Tconst=0.995) geared 4.43:1 (Eff=95%).
Airframe: UrbanFlyer; 310sq.in; 14oz; 6.5oz/sq.ft; Cd=0.05; Cl=0.22; Clopt=0.46; Clmax=0.94.
Stats: 64 W/lb in; 39 W/lb out; 14mph stall; 19mph opt @ 54% (24:56, 98°F); 28mph level @ 75% (12:24, 112°F); 659ft/min @ 22.7°; -255ft/min @ -8.6°.

Possible Power System Problems:

The steady-state battery temperature at the hands-off cruise airspeed and throttle setting (approximately 258°F) is higher than the suggested maximum temperature for this cell type (122°F), which can result in battery pack damage. A lower current would decrease the battery temperature.
Current can be decreased by using fewer cells, a smaller diameter or lower pitched propeller, a higher gear ratio, or some combination of these methods.

[stefanv]

I've made some changes to how MotoCalc deals with battery temperatures, and released version 7.03. Here's the summary from the release notes:

In the contributed data browser, you can now click on the column headings to sort by that column (alphabetically by description or contributor, or by date with the most recent contributions first).
When unable to compute a throttle setting for hands-off level flight, MotOpinion will use the throttle setting for best lift-to-drag ratio airspeed. If that cannot be computed either, it will use full throttle at zero airspeed. In both of the above cases, it will now issue a detailed warning about the implications of the above.
If the battery temperature in MotOpinion exceeds about 95°C or 200°F, the actual temperature is no longer displayed, since it cannot be estimated accurately. The message also indicates that proper cooling may alleviate the problem.

Update as always is available at http://www.motocalc.com/motoupdt.htm

Stefan

[Jim Miller]

I've been playing with Motocalc and been getting stall speeds which don't move much with airframe weight.

Shaw and Ryan use Stall Speed (MPH) = 3.7 * SQRT of Wing Loading(OZ/SQ FT).

Is that what you're using as well?

The result is that whether I have a relatively low or high airframe weight I always get around 14mph stall speed. My calculations indicate that stall speed should get down to about 12mph.

jtm

[stefanv]

MotoCalc uses a more sophisticated method that takes the airfoil, aspect ratio, and other factors into account. However, all other things remaining equal, you should still be getting a square-root relationship between stall speed and wing loading. What wing area and range of weights are you trying?

Keep in mind that because of the square-root relationship, the stall speed changes more slowly than the wing loading does. Also, MotoCalc rounds the final answer to the nearest mph. Just as a hypothetical example using the formula above, wing loadings ranging from 13.34 to 15.33 oz/sq.ft would all give stall speeds in the range of 13.51 to 14.49 mph, which would be rounded to 14 mph by MotoCalc.

Stefan

[Jim Miller]

I suspect we're in the fuzzy range of roundoff errors compounded by the weak sqrt function. I was expecting that 15.25oz/sqft wing loading would have produced 14.5mph stall and a reduction to 11.9oz/sqft would have produced 12.7 mph stall. This is a difference of nearly 2mph but with rounding could be shown as 1mph.

tnx
jtm

[Russell2]

So what happened to the motor and battery temperatures? I downloaded v7, and motor temps displayed for v6 aren't there. Like electrocalc it will let me prop for rediculous situations without a peep. Example, Mega 16/15/4, 8 cells, 20 oz auw 12x12 prop, v6 says motor temp is 680 deg F, v7 says batteries little warm but everything else aok ??? What am I doing wrong?

[boomerace]

Originally posted by Russell2
So what happened to the motor and battery temperatures? I downloaded v7, and motor temps displayed for v6 aren't there. Like electrocalc it will let me prop for rediculous situations without a peep. Example, Mega 16/15/4, 8 cells, 20 oz auw 12x12 prop, v6 says motor temp is 680 deg F, v7 says batteries little warm but everything else aok ??? What am I doing wrong?
I'd be interested in hearing where the motor temps went also although my MiniAC on 9 1050 KANs 6.5 said it would be about 212 degrees and after my flight at mostly vertical climbouts the motor was warm but didn't burn fingers and 212 and above sure will!
boomer

[opualuan]

just checked another of my setups, my geared mega 3T is off by more than 8 amps (motocalc says 35, instead of ~27)... to be fair, it was also off in motocalc 6 by quite a bit, still not sure why...

[FAA]

That a look at my data further up on this thread.

Look at the delta error between versions. Does it fall within the range of error precentage that I posted ?

Nick

[Jim Miller]

When Compute Report/Inflight and the window is maximized so as to be able to see all the rows. If the Throttle setting is reduced by clicking say at the 50% point on the slider bar the window resizes from maximum yet still shows the double rectangle indicating it thinks that it is maximized.

Wierd.

jtm

[rpage53]

Originally posted by Jim Miller
the window resizes from maximum yet still shows the double rectangle indicating it thinks that it is maximized.
That happens when you don't have enough columns of information to fill a maximized window. It is just getting rid of empty space. Weird, but not a problem.

Rick.

[Jim Miller]

Not a major issue for sure but the fact that the window still thinks it's maximized says something is wrong with the window control that they have coded.

jtm

[Neil Stainton]

I've just started to use the increasingly powerful Filter facility. To find the best prop for an LMR glider I used (in MotoCalc 6) to manually find every combination of dia and pitch that pulled my desired current, and click on the In Flight button and note the rate of climb. In M7 I can set the max current, the max pitch ratio, desired pitch speeds, give it a range of props and pitches, and then sort the Static Analysis report by the RofC column to find the best props directly. Bravo! However it would be really nice if the filter also allowed a minimum current to be set, then there wouldn't be so many irrelevant combinations listed.

Also I really miss the motor temperature figure. I understand your reasons, Stefan, but think that reinstating it - but calculated more accurately - would be very helpful. I have thought about the maths involved, and I am sure you could estimate the temperature of the motor at the end of the battery, based on the its heat capacity, initial temperature (initially ambient), and rate of cooling (based on the difference between the motor temp and ambient, slighly affected by air density). You could assume un forced convection. I have done some thought experiments involving hot water and thermos flasks for estimating the specific heat capacity of a sample motor, but I am sure you don't need any help with the science. BTW it would make an interesting QF article!

Neil.

[stefanv]

Regarding the window resizing problem: It will be fixed in a future maintenance release. This is the first report of it, but looking back through the versions, I see that its been there since at least MotoCalc 5, maybe longer.

Regarding the "window control they have coded": We didn't code it. It's the standard window control provided by Delphi.

Regarding motor temperatures: I'll have to give some more thought as to how this might best be handled.

Stefan

[FlyByMike]

Originally posted by stefanv
Regarding the window resizing problem ... I see that its been there since at least MotoCalc 5, maybe longer.Stefan I'll vouch for that. Never was a big deal to me.
-Mike

[opualuan]

how about making rate of climb a filterable value?