What would be an appropriate motor for models in the 680 inch range with a target weight around 65 ounces? I have an unbuilt Score with all the covering stripped that is an easy electric conversion (already has RC type firewall mount) and an unbuilt Brodak Legacy kit. I am new to this and not sure how to size the motor to fit the model and the battery. (I am figuring on at least a TP V2 3900 mah 4-cell 20C-40C 14.8 battery.) There must be published guidelines on this subject but not sure where to look.

also check the "e-Strega flies" thread.

Mike,

Set-up #1 (plenty of power)
Turnigy SK 42-50-650
Turnigy 25C 5S 3300 cells
Phoenix ICE 50 ESC
Will Hublin FM-2 Timer
13 x 4 or 13 x 6.5 APC "E" prop

Set-up #2 (higher power)
Turnigy SK 42-50-650
Turnigy 22C 6S 3000 Li-Poly
Phoenix ICE 50 ESC
Will Hublin FM-2 Timer
13 x 4 APC "E" prop

The 6S set-up flew the EP Strega very well on 66' eye to eye .018" lines @ 5.0-5.3 sec/lap.  The ARF Strega weighs 79 ozs.  Power was no issue.  The Score should respond well to either power system.  I recommend the Turnigy cells because they can be charged up to 3C and that makes turnaround time for multiple flights very reasonable.  I would also recommend the Turnigy Accucell 8 charger because it is inexpensive and has a bunch of bang for the buck.  All of these items except the ESC and Timer are available through www.hobbycity.com  Shipping is quick and the quality is very good.  The timer is direct from Will and I get my Castle controllers from Tower Hobbies.

Hope this helps!!

Archie Adamisin
Muncie, Indiana

Thanks guys. Looking at the prices for the TGY SK42-50 for $26, and the TGY 3000MaH 6S 20 Lipo at $35, those prices seem impossible compared to say AXI and TP motors and battery prices. Is this for real, and is the product any good? If so, why do lots of users apparently opt for AXI 2826 motors for $150 and TP batteries of about this capacity for $150? Does this mean you DON'T get what you pay for??

2012? Well, I can always hope ... That's also the year I will qualify for Medicare!

I do note that the TGY lipo is relatively heavy compared to the TP "lite" series, but I guess the underlying question is, so what? 677 inches with a thick airfoil will carry a lot of weight.

Mike:
Kim's advice about buying quality is spot-on.  The question is how to spot and judge that quality?  He notes that the high price components are also high quality components and I will not dispute that.  However, I think there are equal or nearly equal quality components available for much lower prices.  I think the way we choose the sytem and ho hard it has to work also determines how long it will last.

In brushless motors the only "wear" parts are ball bearings - nothing else touches.  some of the smaller lighter motors are built with 3mm 1/8" or 4mm motor shafts.  The motor shaft is a major structural part of the motor (reducing any flex) so a larger motor shaft is good, plus it naturally leads to larger ball bearings.  The SK42-60 uses a 5mm shaft and is appears to be very robust - Archie's recommendation to use it is based on the fact that he has one and is very enthusaistic about it.  Electrically the SK motors are suspposed to be built using thin stator laminations (supposed to be a good thing) and I am not sure how to judge if there is a low price versus high price version of coppoer wire.  The price looks like fiction, but you are buying at the source from someone who builds millions of motors.  Also as you will see the shippping costs will make up for some of that price advantage!

Batteries are a little tougher to judge - ya can't SEE the working parts!  However I think we are very much in the era where battery quality and performance is growing in leaps and bounds while production capabilities are driving costs way down - much like what happened with PCs awhile back!  Still remember my Packard Bell 486 machine discounted to $2400...!  The Thunder Power packs have always been very good, but the gap has shrunk to much smaller than what it was.  Oddly enough there is precious little DATA or real life anecdotal experience that says that today's CHEAP batteries really wear out too fast!  Today's "cheap" packs have a faster discharge rate, and a faster recharge rate then did the high priced packs of a few years ago.  What drives battery size weight and costs are the higher "C" ratings.  However we really do not need high C rated batteries.  Personally I am avoiding anything below a 20C rating as being "old technology" - I guess some of Kim's advice IS rubbing off on me!

I think the best place to spend money is on the battery CHARGER/BALANCER.  This is where (IMO) the biggest strides have been made.  A good charger will help maximize battery life, a bad charger will bring down even an expensive battery.  Again the Hobby City Accucell 8 may be the best charger you can buy at any price.  The Accucel 6 ihas many of the same features and costs less.  Either will treat your batteries well.

On the ESC - no place to scrimp!  The Castle Creations Phoenix 45 or tne new ICE-50 with the built in data-logger are excellent.  I have no direct experience with the Shulze so I cannot comment but Kim can certainly answer any questions about it.

I am using only Will Hubin timers and am vey happy with them.  Others are using Ztrons and JMP's and they are happy with them.  Go figure.

Finally, one way to add longevity is to keep the stress levels low.  A SLIGHTLY larger motor or SLIGHTLY higher capacity battery will not have to work as hard as their optimized alternatives.  The biggest battery I am flying now is a 3600 mah - on a bird that only uses 2600 mah for a pattern.  This is in a 61 oz profile flying on 018" x 66' lines with a 12x6 pusher prop.  At the end of the flight the motor temperature is hard to sense - scarcely above ambient.  That in my opinion is a low stress combo that should last for a long time.

Mike:
Actually when you buy the Score power package, take a look at Vector sized motors too.  The SK35-42-1000 ($17.51) and Rhino 4sx2350 pack, matched to a Phx 35 and a 11x5.5 APC turning 9400 RPM will turn that Vector everyway but LOOSE!

BTW have you looked over the "List your Sert-ups" thread.  William DeMauro's excellent SV-11 package is similar to what you are looking at.

Well I'll put in an ad for my Vector 40!

A nice combo for electric flight!

Wow, the prices for motors and decent Lipos from these suppliers really put an end to the argument that electric is "too expensive!" We are talking an electric equivalent of the LA46 here! Motors for 40-size planes in the $20 range, batteries for $25-35, timers for $15-20. The ESC is still a little pricey, but that will surely change. I had shied away from E-power because the "good" batteries are $150 and "good" motors about the same, and you need two or three batteries to get in a decent practice session. But at these prices for evidently very servicable stuff, what is anyone waiting for? Thank goodness for enthusiast forums like this one!

Okay, having read all the above and the Strega and SV-11 reports, here is my shopping list for an E-Score:

Motor: TGY SK 42-50
ESC: Castle ICE 50
Timer: Hubin
Battery: In 3300-3700 mah range, 4s or 5s, 20C to 30c, TGY or Rhino
Charger: TGY Accucel-8
Prop: APC 13 inch pusher when available

So, do I get a smiley face for this parts choice? The real head scratcher is still the battery. Users report putting back in from 2000 to 3000 ma after a 6-minute stunt flight, so the "80% discharge" guideline indicates a battery around 3300 at least. I don't know the reasons why 4s or 5s rating, but the higher ones seem to deliver more current with less heat. Some good candidates are the TGY 3300 4s 20C, TGY 3300 5s 30C, Rhino 3700 5s 20C, Rhino 3700 4s 25C. I don't know what criteria to apply choosing a battery, so any help is appreciated. This is actually easier than I imagined, except for the battery choice. Having others blaze the trail helps a lot!

Thanks Alan. I have read and tried to understand your many posts on this subject (I have no electrical engineering background or experience at all) and am starting to get a dim feeling for the relationship between volts, amps, watts etc.

I am now thinking the TGY 42-40 may be a better choice for a 65-70 oz plane than the 42-50. The 42-40 is rated 750kv/600W and a 45A ESC is recommended, while the 42-50 is rated at 650kv/1150W and calls for a 60A ESC. The Castle ICE 50 may be too low in capacity to handle the needs of the 42-50 (though I see that the Strega's new setup uses the 42-50 and the ICE 50). The Score is 677" with an Imitation airfoil (I know because I have both) while the Strega is around 750" and a thicker wing. The Score presumably needs less power to fly well compared with the E-Strega. Am I thinking right about motor selection?

Sorry for so many questions, but I figure this discussion will assist lots of other newbies out there (including, I notice, my neighbor PTG).

Mike,
I just did a check of those two motors on the Hobby City website and they both appear to be out of stock. When ordering from them you should always try to order in stock items as waits for back orders can be lengthy at times. This one is in stock TR 42-50A 700kv Brushless Outrunner / 720W
http://www.hobbycity.com/hobbycity/store/uh_viewitem.asp?idproduct=2099 and might make a decent substitution for a 5 or 6 s battery. Hopefully others that know these motors better than me will chime in.
William

I have been running both the 42-50 and 42-40 in rc on a test plane I use for motor comparisons. I think the 42-50 is much more stout and a better match for our uses as long as you are not tied to a particular battery pack at the get go. Its got a lot more guts than the 42-40.

bob branch

Out of curiosity, how long are the magnets/stator in these motors? I think the dimensions for the Turnigys are the outside dimensions. For AXI and Scorpion, the numbers (AXI 2826 or Scorpion 3020) indicate the stator diameter and length (length also = permanent magnet lengths). The length is usually about the length of the iron can.

I am guessing the 42-50 has magnets that are about 26mm in length, and the 42-40 probably ~16mm in length. If that is true, then the 42-50 really would have much more power capability.

We have a club member with a Score converted to electric - He bought a 42-40 for it (and smoked it on the test stand) so I lent him a '4250' (equivalent) motor that I have while I rewound his 4240.  Long story short, the 4250 was adequate (tho marginal) and in my opinion the 42-40 would NOT be satisfactory for a competition stunter.  My 4240 rewind was measured at 820 Kv, btw.  The 4250 that I lent him was measured at (I think) 790.  For him, as a sport flyer, the Score with the 4240 is OK.

So I would agree that the 4240 is going to be overworked and the 4250 will be <just> OK.  All of the above assumes 4 cells and a 12-6 prop.

Mike,

On 4S, I agree with the 12 x 6 would be marginal, but the 13 x 6.5 would be better yet still a bit light.  Go to at least 5S and you will have no issues with power.  I plan to run my 42-50-650 on 6S on a 13 x 4.5 Pusher @ 10,000 rpm on a 700 sq in 58-62 oz design I drew up last month.  This set-up was great for the Strega.  5S would also yield the same result, but would need a bit more capacity.

Archie Adamisin
Muncie, Indiana

See my followup post under "Part 2." I reached the same conclusion about the Score and am building a Claus Maikis China Clipper instead. My wet-power Score flys very well with Enya 61CXS Pro and 13 x 5.2 Mejzlik 3-balde. Good design, but a little homely.

Correct in that a 5s is 18.5 volts.

For the most part, the motor and the ESC don't care what the voltage is - it's the current drawn which you have to keep within limits ... in the case of an RC model using several servo's off of the BEC, then you have to keep the input voltage within the specified limits because the onboard 'voltage conversion' is sensitive to the input voltage as well as the current draw.  In our C/L models however, we don't have any large current draws on the BEC and in fact, most of the ESC's we use here don't even have a BEC - we simply tap voltage to run the timer from the same spot that runs the ESC logic - so there is no real issue with using a higher voltage.  

A rather long-winded way to say, nope ... it's really not an issue.