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Posted by cloud_9 | Jan 01, 2014 @ 11:03 AM | 4,355 Views
Drill bit sizes.
Posted by cloud_9 | Nov 28, 2013 @ 08:10 PM | 7,364 Views
Drill Bit Sizes for Screws and Taps
(from Great Planes Dead Center Engine Mount Hole Locator package)

Drill Sizes for Sheet Metal Screws
Screw === Pilot Hole
#2 --- 1/16"
#4 --- 3/32" or 5/64"
#6 --- 7/16
#8 --- 1/8"

Drill Bit Sizes for Tapping
Bolt === Pilot Hole
2-56 --- 5/64"
4-40 --- 3/32"
6-32 --- 7/64"
8-32 --- 9/64"
10-24 --- 5/32"
10-32 --- 5/32"
1/4-20 --- 13/64"
Posted by cloud_9 | Nov 26, 2013 @ 02:27 PM | 4,951 Views
This is from the web site for Hot Slots

Understanding R/C Brushless Motor Ratings

kV Ratings

Ok, lets start with kV ratings. The letters kV stand for the the RPM of your motor per volt with no load. For example if you own a brushless motor with a kV rating of 4600 and 12V. Take the 4600, multiply by 12 to get 55,200 RPMs. This is the max RPMs that this motor can reach under no load. Once you get it inside your vehicle, this will come down due to friction.

Almost all brushless motors will have the kV ratings stamped somewhere on them. Some motors will have kV ratings on the motor can, others on the motor leads, but some you will only see on the motor�s spec sheet.

Ok. now you are this far, so what does this mean to you really?

A motor with a higher kV will have more top end speed, but not as much acceleration/torque.
A motor with a lower kV will not be as fast, but will accelerate faster.

So, now you can decide which one works best for your kind of racing. You have the room to really crank it up and reach top speeds? A higher kV will get you there. But maybe you are on a shorter track, and what you want is acceleration out of the corners, then look for a lower kV number. Still not sure which way to go? Try something in the middle!

Note: If motor heat is an issue then a lower kV rating with a higher voltage battery will give you the same effect.

The big thing to remember when using kV for your Brushless Motor Ratings is that your...Continue Reading
Posted by cloud_9 | Nov 03, 2013 @ 02:01 PM | 5,247 Views
These remarks about the choice between a gas and a glow engine, and relative positives and negatives, have been gleaned from several threads on RCU, RCG, and FG.

Unfortunately as I started collecting these it was just for myself and I did not record who contributed each one. When the collection started to seem blog-worthy, I didn’t know where to find all of my appropriations, so I’ll just say, these are from several brilliant and gracious folks who have shared their knowledge and to them go both the credit and my thanks.
I replaced an OS 120 FS with a DLE 20. OS 120 w/muffler weights about 32 oz. DLE 20 weights 29 oz with muffler and ignition modual. But it will need a battery so weight comes out about the same. The DLE 20 is slightly longer front to back than the OS so you should measure for that or expect to modify the firewall area. You have more flexability re the cg because you can put the battery were needed for cg. On one of my gassers I had to put both batteries under the cowling to get cg. On another I put the battery way back in the tail under the rear stablizers to balance. The DLE turns the same prop 300 rpm more static that the 120. Also the DLE is shorter top to bottom except for the spark plug boot. I've put DLE 20s on airplanes from so called 60 size to 120 size. I'll admit the 60 size is somewhat over powered, but the 15-17 cc gasser have about half the power of the DLE 20 and are only an ounce or two lighter. I have a couple of RCGF 20cc gassers....Continue Reading
Posted by cloud_9 | Jun 19, 2013 @ 11:58 AM | 5,230 Views
Question by Captain MoMo in response to "Determining power requirements"

Thanks for a nice summary and explanation. How do I determine whether a certain 3s motor can be run on 4s? I have a Turnigy 2815 EDF motor and it says 3s for power supply and I want to know how I can determine if I can safely run a 4s as the power supply. Appreciate the feedback.

Hi, there are two ways to do it using your watt meter: by watts or amps...which are actually the same thing looked at differently.
Watts: you look at the maximum watts listed by the manufacturer, then multiple your volts times your amps = your watts, to see if you are exceeding the motor's watt limits. 3.8 volts per lipo cell (or 4.2 at full capacity). How many amps are you using? Well it depends on the prop and how many amps are drawn when running it. Put a prop on it and measure the amps drawn as you increase throttle. Actually with most meters you can just measure watts used directly, it does the multiplication for you. Whether you measure amps and multiple it times number of cells times 3.8, or you just watch the watts directly, you want to make sure the watts measured does not exceed the max.

Amps: Another way is to just look at the motor's max amps rating, and be sure the amps measured does not exceed the listed max amps.

If you don't have a meter or don't have the prop in hand, then you have to find some estimate of how many amps the motor uses with various props. You should be able to get that...Continue Reading
Posted by cloud_9 | May 24, 2013 @ 07:19 PM | 5,575 Views
A discussion of what the graph in the main window is showing, in which Landru clears up my confusion
Posted by cloud_9 | May 24, 2013 @ 05:09 AM | 5,816 Views
Alaska asks: Wing loading -vs- plane size
I know that wing loading is an important factor in the way a model flies. Does model size enter into it? Suppose I have a 36" span plane and a 72" span plane, both with wing loadings of 16 oz/sq ft. Will they have approximately the same flying characteristics? (given a similar airfoil, power / weight ratio, etc)

Griffin replies: To get a cubic wing loading of 6.5 on the smaller plane to match the larger, you would need to get the weight down to 12oz and have a wing load of 8oz. In theory, the two planes would look like they are flying at the same speed, and they would stall at a relatively similar airspeed. It's not a perfect system of course, but it is about 200 times more helpful than wingloading....


PS, figuring cubic wing loading can be done on a calculator, but I like to cheat and use this great on-line calculator:
Posted by cloud_9 | May 21, 2013 @ 10:00 PM | 5,403 Views
Magister Power System Numbers for a Turnigy 4250 Brushless

Dimension: 48mm x 42mm, 68mm(with shaft)
Weight: 199g (kv1000) (not including connectors)
Diameter of shaft: 5mm
Length of front shaft: 18.7mm
Lamination thickness: .2mm
Magnet type: 45SH
Max performance
Voltage: 4S
Max current: 45~54A
Prop: 10x5~11x5.5
Thrust: 2050~2450g
For 2000-2500g 3D model airplane.
Kv (rpm/v) 1000
Weight (g) 199
Max Current (A) 54
Resistance (mh) 0
Max Voltage (V) 15
Power(W) 0
Shaft A (mm) 5
Length B (mm) 48
Diameter C (mm) 42
Can Length D (mm) 27
Total Length E (mm) 68

Prop..........Size........V.........A........W.... ..RPM.....Thrust
Xoar..........10x5.....11.68.....36.2....424....11 220.....2lb 12oz
APC.........10x5.....11.60.....35.6....413....1119 0.....3lb
APC.......11x5.5.....11.28.....46.4....524....1026 0.. .3lb 12oz
MAS.....11x7x3.....10.85.....51.0....554.....9680. .. .4lb 2oz
APC.........12x6.....10.98.....56.7....623.....939 0.. ..4lb 6oz
Posted by cloud_9 | May 21, 2013 @ 09:52 PM | 6,018 Views
1. Power can be measured in watts. For example: 1 horsepower = 746 watts
2. You determine watts by multiplying ‘volts’ times ‘amps’. Example: 10 volts x 10 amps = 100 watts

Volts x Amps = Watts

3. You can determine the power requirements of a model based on the ‘Input Watts Per Pound’ guidelines found below, using the flying weight of the model (with battery):

• 50-70 watts per pound; Minimum level of power for decent performance, good for lightly loaded slow flyer and park flyer models
• 70-90 watts per pound; Trainer and slow flying scale models
• 90-110 watts per pound; Sport aerobatic and fast flying scale models
• 110-130 watts per pound; Advanced aerobatic and high-speed models
• 130-150 watts per pound; Lightly loaded 3D models and ducted fans
• 150-200+ watts per pound; Unlimited performance 3D and aerobatic models

NOTE: These guidelines were developed based upon the typical parameters of our E-flite motors. These guidelines may vary depending on other motors and factors such as efficiency and prop size.

4. Determine the Input Watts Per Pound required to achieve the desired level of performance:

Model: E-flite Brio 10 ARF
Estimated Flying Weight w/Battery: 2.1 lbs
Desired Level of Performance: 150-200+ watts per pound; Unlimited performance 3D and aerobatics

2.1 lbs x 150 watts per pound = 315 Input Watts of total power (minimum)
required to achieve the desired performance

5. Determine a suitable motor based on the model’s power...Continue Reading
Posted by cloud_9 | May 11, 2013 @ 11:25 AM | 8,955 Views
From Everydayflier:

4.2 100%
4.1 90%
4.0 80%
3.9 70%
3.8 60%
3.7 50%
3.6 40%
3.5 30%
3.4 20%
3.3 10%
3.2 0%

From NoFlyZone's blog, numbers from IA-Flyer:

It also seems that we will maximize our Li-Po life by taking them down to no lower than 20% of their capacity. Here is the latest and greatest information I have managed to gather from extensive reading on this subject.
"Resting" Voltage per cell
4.20v = 100% of our battery's amp capacity remains.
4.03v = 76% of our battery's amp capacity remains.
3.86v = 52% of our battery's amp capacity remains. (A good voltage to store our Li-Pos at)
3.83v = 42% of our battery's amp capacity remains.
3.79v = 30% of our battery's capacity remains.
3.75v = 20% of our battery's amp capacity remains. (Where we want to take our Li-Pos to for long life)
3.70v = 11% of our battery's amp capacity remains. (Detrimental 'battery voltage dump' begins)
3.6?v = 0%
In line with the above, we do NOT want our Li-Po's resting voltage to be less than 3.75v per cell, which would mean we had used about 80% of their capacity.

Store them at about 3.85 volts per cell (about 50%)
Fully charged: 4.20v/cell x 3S = 12.6 volts
Storage voltage: 3.85v/cell x 3S = 11.55 volts
20% left: 3.75v/cell x 3S = 11.25 volts
Posted by cloud_9 | May 11, 2013 @ 11:24 AM | 6,502 Views
A diagram of how CCCV charging works.
Posted by cloud_9 | May 11, 2013 @ 11:23 AM | 5,891 Views
Graph of zip charging A123 cells, using Dan Baldwin's Terminator II. At the right, voltage reaches cutoff level, connection is terminated (presumable causing voltage spike), amperage drops, final voltage at full charge.
Posted by cloud_9 | May 11, 2013 @ 11:20 AM | 5,919 Views
Tip Stall and Flaperons
Discussion / Posted by cloud-9 / Jul 10, 2008 @ 12:05 PM / 7,900 Views / 0 Comments / Reply
Why flaperons increase the tendency to tip stalling. Comments and corrections most welcome.

Full length flaperons:

The angle of attack at the root is usually greater than at the tip, thanks to washout, even when flying level. Thus, in level flight, stall starts at the (trailing edge of the) wing root. When banked and turning, the inside wing tip travels slower than the root, the outside wingtip travels faster than the root. The inside wingtip generates less lift, since it is traveling slower. So when turning, there is a tendency for the inside wing to drop, and a tendency for the outside tip to lift, relative to flying level. This can lead to tip stall.

When flaperons are dropped, the overall angle of attack is increased, and stall tendency is increased (stall speed is decreased). The whole wing is more likely to stall. This magnifies effects of turning on lift and stall behavior of the wings tips and tip stall likelihood is increased.

Flaperons on outer wing:

When the flaperons are only on the outer part of the wing, the angle of attack of the outer part of the wing is increased (stall speed decreased) but the inner part of the wing is unaffected. Thus, when turning, the effect of this difference in stall characteristics of the inner and outer wing are added to the above-described effects, and tip stall probability is increased further.

...Continue Reading