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Old Oct 18, 2001, 01:37 PM
Registered User
Exton, PA, USA
Joined Jul 2001
35 Posts
AC-130U Gunship conversion

I need some basic information regarding the possibility of getting a project off the ground. I just received a set of 1/12 scale plans of a C-130 from palmer plans and was wondering if it can be converted to electric flight. The instructions say the target weight is 22 lbs, I know I can build it lighter if I use different materials. Also what size motor and gear ratio would be required. I have never done a multi powered electric and could also use some ideas on motor/esc/battery hookup.

Model Dimensions:
Length: 97.75 in
Wingspan: 132.84 in
Wing Area: 1745 sq in
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Old Oct 19, 2001, 03:52 PM
Mike Swan
Oroville, California, United States
Joined Oct 2000
372 Posts
Have you tried motocalc its in the links its been pretty useful in figuring out the power end of building.Mike
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Old Oct 21, 2001, 01:17 AM
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KenMizell's Avatar
Bellevue, WA
Joined Sep 2001
97 Posts
AC 130

Popular choice this week. I would like to build one too.

Use 4 Mega ACn 22/45/3 Brushless motors with 4 Jeti 40 amp sensorless brushless ESC without BEC and 10 Panasonic 3000 mah NiMH cells per motor and 4 seperate Nimh cells for flight pack.

This will give you about 8 min. cruise with 68 watts per lb with about 315 watts to each 10x6 prop. (ElectiCalc)

Depending on your prop choice, you could easily make them counter rotating on one wing.

That is 5 pounds of batteries so it will be hard to keep your weight down.

Send pictures.
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Old Oct 23, 2001, 12:49 PM
Registered User
Exton, PA, USA
Joined Jul 2001
35 Posts
Thanks for the power setup info. I was not expecting to have to use four speed controllers, is their a single esc that can handle the power out there? Also would it help to gear the motors. The plans call for 11x5 3 bladed props, I am currently looking for some 4 bladed ones that will look a little more scale.
Well enough on the power problems, I started the trussed box frame last night and things seem to be going well. Maybe I'll have something by Christmas
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Old Oct 23, 2001, 03:12 PM
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Eddie P's Avatar
United States, NV, Reno
Joined Mar 2000
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Don't go brushless for your C-130. As long as there is such a price difference between brushed and brushless, you can find very succesful ways to keep costs in line for a model that has a naturally draggy airframe and four powerplants. (unless of course you start getting any much bigger than what you are talking). Brushless motor setups are GREAT for ducted fan stups where RPM is a major factor, or hotliner fast models where RPM and very powerful bursts of thrust are the name of the game. A scale multi-engine aircraft can and will fly very well on a brushed setup.

A solid brushed motor combo will cost 20 times less and be more suited for a 4 motored model. Because you are looking at so much model here, you will probably have to wire your motors in sets of two, with two different speed controllers. The Astro 204D is good for 60 amps continuous, and would be very comfortable running 2 motors at a time (like both inboard motors for one ESC, both outboard motors for the other).

There is a C-130 that Roddel Model of Germany puts out that has similar dimentions to your design and it is powered by 4 speed 600 motors. You can get larger brushed motors too, but watch the prices as when you get bigger here the price gap between brushed and brushless closes slightly. They use a bungee launch on the Roddel kit but looking at the Mpeg on their site (can't find address at this time!) the model really hauls and could probably easily ROG if it had wheels.

You were asking about geared setups - you could easily gear your motors to swing a larger prop and have a more realistic flight profile. You are talking more money and tinkering, but your model is gonna be big so why not go the exra mile here. It will loose high end speed, and gain low end thrust. But, I've never seen the Hurc go fast in any phase of flight, so this would certainly be a move closer to scale. You wouldn't need to do it to have the model fly though, it would fly fine direct drive if that was your choice.

Remember, KEEP IT LIGHT or you just may HAVE to go brushless! With that size of a model you will have lots of opportunity to save weight, or gain weight. I'd also recommend getting Motocalc and running some numbers in there to narrow down your motor and battery choices.

Ed
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Old Oct 23, 2001, 05:57 PM
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Bill Glover's Avatar
United Kingdom, Bracknell
Joined Nov 2000
12,040 Posts
There's a HUGE (4.3M / 14' span) electric B29 on the UK display circuit that ROGs off grass with an r/c Bell X-1 slung underneath, and that's powered by 4 geared S700s and 64 cells IIRC. Pretty low-tech, but very effective.
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Old Oct 25, 2001, 02:47 AM
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ScottS's Avatar
Houston,TX
Joined Mar 2000
1,217 Posts
Quote:
Originally posted by Eddie P

A solid brushed motor combo will cost 20 times less and be more suited for a 4 motored model. Because you are looking at so much model here, you will probably have to wire your motors in sets of two, with two different speed controllers. The Astro 204D is good for 60 amps continuous, and would be very comfortable running 2 motors at a time (like both inboard motors for one ESC, both outboard motors for the other).

Ed
Could you provide some numbers for this 20x cost difference?

I can still see an advantage, in using few controllers with brushed motors. But right now the easy of use and less maintenance makes brushless look pretty good.
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Old Oct 25, 2001, 03:10 AM
high-speed freak
opualuan's Avatar
San Jose, CA
Joined Sep 2001
3,863 Posts
that's the great thing about brushed motors. no maintenance. they die, you swap them out, something tough to afford with brushless.

anyone know about using some of those very high power car motors with gearbox for this model? at $20 a pop... might be worth investigating. definitely get motocalc, it will help you figure out if a certain combo is even a possibility.
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Old Oct 25, 2001, 07:09 AM
D.G.B.
KOMET 44's Avatar
Southington, Connecticut, United States
Joined Jun 2000
2,952 Posts
TMP, (1)The power trane needs to be half the weight of the model (2) L ook to see what kind of wood is used.Chances are there is a good amount of plywood.this is where you'll need to do some thinging and use lite wood .This winter i will be starting my german tranport plane .it has a 15' w.s. but will weigh in at 16lbs ready to fly.And yes i will be useing the cheap can motors.july2001 E.F.I. International has a GREAT artical on Mr.Ivan Pettigrew.He has a 1/2 dozen BIG planes on cheap buggy motors but nearly all gearboxes are home made.Look for any post's by Martin Irvine he did the interview and i believe he knows him good.remeber LITE IS RITE!!!!!!!! stefanP


Negative ghost rider,the pattern is full...
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Old Oct 25, 2001, 08:43 AM
Speed Demon
GregG's Avatar
Antioch,CA,USA
Joined Dec 1999
12,335 Posts
Quote:
Originally posted by Eddie P
There is a C-130 that Roddel Model of Germany puts out that has similar dimentions to your design and it is powered by 4 speed 600 motors.
Ed
That huge "Herc" by Roedelmodell can be found <a href=http://www.roedelmodell.de/englisch/sherc.htm target=blank>here</a>. Ther are great pictures of it and a couple of short videos <a href=http://www.roedelmodell.de/englisch/glry2.htmtarget=blank>here</a>.
I like the text they include on the description page.

"XXL C-130 Hercules Let the ground shake!!!

Did you believe that the '600-class' just includes 'baby airplanes'? - Then cry tears of fear if this monster is roaring towards
you! :-)

Do you have problems with mice out on your flying field? - Just make a low pass with the Hercules - and you won't be able to find one single mouse within 1 Mile vicinity!"
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Old Oct 25, 2001, 12:09 PM
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Eddie P's Avatar
United States, NV, Reno
Joined Mar 2000
7,607 Posts
ScottS said:
>>>>>Could you provide some numbers for this 20x cost difference?>>>>>

Well, getting the calculator out, 4 Graupner speed 600's @ $17.01 ea, One New Creations M-80 ESC, $90 ea. 20 loose cells of 2400 mah Sub C @ $130.... $288.04 total, for the entire 4 engined powertrain.
Now for brushless.
4 Mega 22/45/3 motors @ $ (appx.) 220.00 ea, 4 Jeti 40amp ESC @ $88 ea, 40 loose cells of 2400mah sub C @ $260.
Total is $1492.00, and we haven't even spent a dime on the model and radio setup yet.

Yes, you are correct, it isn't 20 times the price, just more of a generaliztion here. But for 1500 bucks in just the model's powerplant, somebody's first multiengine project (as he said) just got pretty pricey (into turbine range), and we haven't even touched on the RF feedback issues involved in brushless multi-motor, long wired, big model applications.

>>>>>I can still see an advantage, in using few controllers with brushed motors. But right now the easy of use and less maintenance makes brushless look pretty good.>>>>>>

Brushless is really the way to go, like you said here, for many different applications. Mabey I'm wrong, but I have personal 1st hand knowledgve via a friend, heavily involved in multi-motored brushless models, that some advanced thinking has to come into play when you get more than one brushless motor in the mix. Not so much for an experienced e-modeller, but for a first time multi-motor project, especially 4 motors, in that size of a model.... I'm not so much going against your brushless statements but trying to give tmpalfalvi, a self described new comer to multimotored e-flight, a suggestion for likely 1st time success.

Ed
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Old Oct 26, 2001, 11:54 AM
Registered User
Exton, PA, USA
Joined Jul 2001
35 Posts
Thanks for all the advice. I think I will go with the standard brushed motor setup with two jeti controllers. As for construction the fuselage warren truss should be done by sunday if all goes well this weekend.
I will try to post pictures of the model as it progresses through the construction.
Ted
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Old Oct 26, 2001, 02:11 PM
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DICKEYBIRD's Avatar
COLLIERVILLE, TN USA
Joined Jun 2000
617 Posts
Hi tmp,

You mentioned warren truss construction....are you making a triangulated rectangular fuse structure with 4 "mini-bulkheads" at each station to complete the circular shape then sheeting it? I have been "think building" a Convair 340 for a while now and have sketched a stucture in TurboCAD using one of Laddie Mikulasko's & other's methods (copying one person is plagiarism, copying several is RESEARCH!) I am planning to use a rectangular basic fuse structure then gluing foam blocks on the outside between the mini-bulkheads at the various stations, then carving & sanding away anything that doesn't look like a round fuse with big fillets; then covering the thing with 2 overlapping layers of brown wrapping paper/thinned Titebond before priming & sanding.

I'd like to hear details of how your 130 structure goes together...pics perhaps?
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Old Oct 28, 2001, 10:39 PM
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Blackhornet's Avatar
South Florida
Joined Sep 2001
43 Posts
Is there any one in the US that imports the Roedelmodell C130.
And if so how much.
I saw the video, would love to own one.
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Old Oct 28, 2001, 11:49 PM
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ScottS's Avatar
Houston,TX
Joined Mar 2000
1,217 Posts
Quote:
Originally posted by Eddie P
ScottS said:
>>>>>Could you provide some numbers for this 20x cost difference?>>>>>

Well, getting the calculator out, 4 Graupner speed 600's @ $17.01 ea, One New Creations M-80 ESC, $90 ea. 20 loose cells of 2400 mah Sub C @ $130.... $288.04 total, for the entire 4 engined powertrain.
Now for brushless.
4 Mega 22/45/3 motors @ $ (appx.) 220.00 ea, 4 Jeti 40amp ESC @ $88 ea, 40 loose cells of 2400mah sub C @ $260.
Total is $1492.00, and we haven't even spent a dime on the model and radio setup yet.

Yes, you are correct, it isn't 20 times the price, just more of a generaliztion here. But for 1500 bucks in just the model's powerplant, somebody's first multiengine project (as he said) just got pretty pricey (into turbine range), and we haven't even touched on the RF feedback issues involved in brushless multi-motor, long wired, big model applications.


Ed
You are still cheating alittle... comparing a 20 cell setup to a 40 setup isn't really apples to apples. There is no reason not to use a 20 cell brushless setup if 20 cells works for a brushed setup. I think the Jeti 15/4 ($89) or Jeti 30/3 ($99) would be much closer motor matches. If you want to deal with the startup issues you might also be able to get by on 2 controllers instead of 4, but even with 4 controllers and 30/3 motors.. this brings the total down to $878. This is still 3 times the cost of your speed 600 setup, but a far cry from 20x. I would still be considering the brushless setup, there is really no comparison in quality between the Jeti brushless and a Speed 600 in my opinion, but this is more of a personal preferance.
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