Author Topic: Light set up for a 14x5 prop 3B (Read 1409 times)

TDM · « **on:** November 06, 2009, 06:15:42 AM »

How do you balance the weigh of the batteries the size of the motor to get the most out of the power plant as well as having the lightest Set-up for the ship. There are trade offs but where would you rather make them.
I am making a larger stunt plane about the size of Stega maybe a bit larger and I am pondering on what motor battery combination to use. The surface area is 640 square inches and the target weight is 55-60 ouces.

I am considering

TGY AerodriveXp SK Series 42-50 650Kv / 1150w
Turnigy 3300mAh 4S 30C Lipo Pack
Pheonix Ice Lite 50
14x5 prop Gator 2b or 3b

bob branch · « **Reply #1 on:** November 06, 2009, 07:11:02 AM »

Dorin

First thing to consider is that if you are going to come in at that weight you are not in Strega territory, you are 15 to 20 ounces lighter! You are actually in T-Rex territory. Just as a reference an AXI 2826/12 will fly a plane to 63 ounces on 63 ft lines at 5.3 sec laps with an APC 12X6 E at about 8300 rpm plus or minus 100 rpm for drag factors WITH AUTHORITY on a 4 cell pack and under 2000 mah for a 5.30 sec pattern. That gives you the pattern and 8to 10 laps to spare. We are doing that conservatively on 3000 mah 4 cell packs here and 2600 is no problem. Pushing the wieght if you can balance it some are starting to use 2200 mah packs but school is out on longevity there. We are just starting to test that locally.

If you are going to fly on 4 cells you will want a bit higher KV. The 2826/12 is a 760 KV motor and this range has proven very good on 4S packs to get into the 12X6 rpm range. The pusher version will require a hundred or two more rpm but is well worth it performance wise and mah draw will still be under 2000 mah for the same time pattern.

bob branch

TDM · « **Reply #2 on:** November 06, 2009, 10:13:09 AM »

Thank you Bob.

Can Axi handle a larger prop but smaller pitch?

bob branch · « **Reply #3 on:** November 06, 2009, 10:26:16 AM »

Dorin

I fly it with a 15X6 on RC 3D planes. Of course you have throttle there, but its not a problem turning a larger diameter lower pitch prop. The thing you will want to look for though is the KV going to be high enough on 4 cells or will you have to go to 5. Some of the folk who fly 5 inch pitch can give you a good idea of what rpm you need for your line length and lap time goal. Then see if you will have the kv to get there. Higher KV motors generally use more amps so be aware of that. Its the reason Rick Sawicki and I fly on the /12 wind of the 2826 vs the 10 some others use. You may want to go to 5S which the motor will handle. I was really kind of trying to give you what works motor, prop, battery in a plane that size reather than trying to match your prop diameter request. I think you may be looking to turn a lot bigger prop that what you need. I am flying an 82 ounce electric strega with a 13X6.5EP and ita all the prop you need. I will be trying a 13X4EP next week with it that the Adamisin's have had commissioned by apc that is working very well in theirs on 6 cells. Their Strega is a few ounces lighter than mine but you are looking at a much smaller and lighter airplane. Strega is 742 squares. My PA-51 version of the arf on a pipe comes in at 78 ounces without fuel.

bob branch

Igor Burger · « **Reply #4 on:** November 06, 2009, 11:12:55 AM »

Quote from: Dorin Morosanu on November 06, 2009, 10:13:09 AM

Thank you Bob.
Can Axi handle a larger prop but smaller pitch?

be carefull, both, lager prop as well as lower pitch will need MORE power

RandySmith · « **Reply #5 on:** November 06, 2009, 11:27:56 AM »

Quote from: Dorin Morosanu on November 06, 2009, 10:13:09 AM

Thank you Bob.
Can Axi handle a larger prop but smaller pitch?

Using the lower pitched and larger diameter prop you are asking about will put you closer to using 3000 Mah or maybe a little more

Randy

Dennis Toth · « **Reply #6 on:** November 06, 2009, 03:09:33 PM »

Dorin,

Welcome to the Bright side! The last time I saw you was at the 99 Nats. Are you still in the prop business? We could use some very thin light carbon props for electric, pushers at that (you need to try the pusher set up, it is very good). Your project sounds great. The size you are in is close to Bob Hunts ship (maybe Bob or Dean and add the details) but what has worked is the AXI 2826/10 or 12 with a TP Pro Lite 4S1P 3900mah pack with a prop set to around 5.8" pitch @8800 - 9000rpm. Look in the "Whats your setup" thread at the top of the forum and you will get a very good idea of the different set ups for various size / weight ships. One tip I give all that are starting out in ECL is to spend your money on a first class charger, this will protect your batteries and prevent problems.

Best, Dennis Toth

Howard Rush · « **Reply #7 on:** November 06, 2009, 07:45:19 PM »

Time for both you guys to start going to the Nats again.

TDM · « **Reply #8 on:** December 21, 2009, 02:31:35 PM »

What about a TGY AerodriveXp SK Series 35-48 1100Kv / 770W it looks like it would run on a 3S Battery . What do you say? Maybe on a 12.5 x 4.5 pitch around 10000 Rpm. I wonder if it would eat too many Amps?

Mark Scarborough · « **Reply #9 on:** December 21, 2009, 03:25:21 PM »

You may look at the Hacker series of motors, say the Hacker A30-8XL which is a higher KV. My in progress setup is to use this in a 640 inch airplane with the same target weight.

Dean Pappas · « **Reply #10 on:** December 21, 2009, 06:34:06 PM »

Hi All,
Thanks for the prod Dennis.
I take a slightly different tack than many others: first, I like to have more voltage headroom so that the governor has the "poop" not to mention the pop to immediately stamp out the transient RPM losses we see when maneuvering. This means that I like to prop for between 70 and 75% of Kv times the battery voltage. As an example, that means a 900 Kv motor on a 4S pack turning in the low 9,000s. On 67 or 68 feet that means a 6" pitch prop. On closer to 60 feet it means maybe a 5.

Obviously everything scales with battery cell count so that either Kv or pitch go down proportionally with more cells. I don't like running at 85 or 90% of the Volts*Kv product because, even though the low voltage overhead setup is more efficient, it will not have the drive exiting corners of what I described above.

My rules of thumb have been
1) choose the running RPM based only on the Kv and cell count. (0.7 ~ 0.75 times Kv times Vbattery)

2)Once that RPM is known, and the line length is chosen, the pitch is dictated to you by two. (unfortunately the number on the prop is not the one you really need!)

3)Once a prop with that pitch is chosen (some lie high, others lie on the low side) use as much diameter as possible, or add blades, until the airplane pulls well everywhere.

4)How much draw and how much battery? Planes on 60 feet of line need 0.63 Watt-hours per ounce of ready to fly weight just to fly the schedule. Planes on closer to 70 feet of line need 0.7 Watt-hours per ounce. Example: a 53 ounce plane on 67 feet needs 53*0.7 watt-hours of battery or 37 watt-hours. Assuming a 4S battery of 14.4V I divide 37 by 14.4 to get 2.6 amp-hours of battery capacity used.

5) use no more than 75% of the battery (others say 80, but i think it leads to premature battery capacity loss) so that 2.6 A-H of consumption demands a 3.4 A-H battery. (Okay, I'd go for 3.3 too, but most good 3.8 or 4 A-H packs weigh the same as 3.3s, so why not have the extra capacity and baby the cells at the same time.

6) In general, low RPM is more efficient, but high RPM/low pitch has somewhat better resistance to wind-up in runway wind. This last point is certainly to be argued, but I think the sweetspot is around a 4.5" pitch for lines around 60 feet and around 5.5 for lines out at 70 feet. Prop snarl starts when the multiplied product of diameter and RPM is greater than 130,000 and gets un-electric when above 140,000.

I apologise if I got long-winded again!
take care,
Dean P.

Dennis Toth · « **Reply #11 on:** December 22, 2009, 07:47:37 AM »

Dean,

That is a great post. We needed a straight forward process to work our way through the universe of chooses. I think this should be added to the "set up" thread.

Now if you have a similar process for using one of the "Motor" programs to help narrow the motors please post it.

Happy Holidays to all.

Best, DennisT

Dean Pappas · « **Reply #12 on:** December 22, 2009, 03:22:17 PM »

Hi Dennis,
I don't use the motor calculators for picking motors, I tend to use it only to verify the initial prop diameter choice.
I'll write that out in just a bit.
Happy Holidays, Gang!
Dean

Author Topic: Light set up for a 14x5 prop 3B (Read 1409 times)

TDM

Light set up for a 14x5 prop 3B

bob branch

Re: Light set up for a 14x5 prop 3B

TDM

Re: Light set up for a 14x5 prop 3B

bob branch

Re: Light set up for a 14x5 prop 3B

Igor Burger

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RandySmith

Re: Light set up for a 14x5 prop 3B

Dennis Toth

Re: Light set up for a 14x5 prop 3B

Howard Rush

Re: Light set up for a 14x5 prop 3B

TDM

Re: Light set up for a 14x5 prop 3B

Mark Scarborough

Re: Light set up for a 14x5 prop 3B

Dean Pappas

Re: Light set up for a 14x5 prop 3B

Dennis Toth

Re: Light set up for a 14x5 prop 3B

Dean Pappas

Re: Light set up for a 14x5 prop 3B