Giant Multi-motor How to build cheaply.

[edoc]

Sorry I don't have the answer to building Giant Multi-Motor planes cheaply. I am hoping you will help here.

I have a good friend who has converted mostly to Electric. However, limitted funds have prevented him from building any really large electrics.
He is planning on purchasing the Hobby People C130 and would prefer electric power. http://www.hobbypeople.net/gallery/190130.asp

Specifications:
Wingspan: 100" (2540mm)
Length: 74" (1880mm)
Engines: 4 x .25 - .32 Two Strokes, 4 x .30 Four Strokes, or 4 x Brushless Electric Motors
Radio: Minimum 5 channel (6 with optional retracts)
It would have been nice if they had included finished weight in the Specs. However, I believe we can get a good idea of motors needed from glow motors used.

He asked me to see if it were possible to convert this plane to electric for under $500. I would appreciate any Motor/ESC/Battery/Servo ideas you have especially if you have done a simular project. If we are successful, I am hoping he will join RCgroups and photo the build for us in this thread.

Thanks,
Tim

[edoc]

I would like to keep it as simple as possible. John has a 3 amp 3S charger. Having to purchase an expensive charger would be a deal breaker. At the field I would be able to charge multiple packs at a time for him. Also, 3S could eliminate needing a seperate reciever pack or a UBEC.

Battery:
I think this will be the big cost problem
I am thinking 3S, 3to6P (depending on capacity) set up that can handle 140 to 160 amps might do it. Even a bunch of used 3S packs of different capacities can be used in parallel.
Maybe 4S A123s would work well. I have no experiance with them. Can you use a BEC on 4S? Is this project possible on the lower voltage of 3S A123?
Any suggestions?

Motors:
http://www.bphobbies.com/view.asp?id=V450327&pid=W392031
One with a little lower KV to throw a 10-11 inch prop would be better.

ESCs:
4 of these? http://www.bphobbies.com/view.asp?id=A0780192&pid=B2049175
Would one BEC be adequate? Could 2 BECs be used in parrallel?


As I work on this I am thinking a 3S Lipo Twin such as a B-25 would be a fun plane for me.
Tim

[Rob Schaffer]

Go over to the Glow-To-Electric Conversion Forum, SCALEFAN has done this plane, twice. First time ended in a stall-spin-crash, second one was great! He has a good thread on building tips, do's-don'ts, and a full explaination of his power system.

Glad to see another one, Rob

[mountainman2442]

Tim,

While cheap means different things to different folks, I'm guessing I have less than $400 in materials in my Short Solent (http://www.rcgroups.com/forums/showthread.php?t=682384) built from Ivan's plans (http://www.geocities.com/ivansplans/). I never try to keep track of expenses in this hobby, first, so the wife never finds out, and second, so I don't either!

There are several others who have built large multi motor planes from Ivan's plans. LukeZ's Solent (http://www.rcgroups.com/forums/showthread.php?t=463117) , Rudderman's Mars (http://www.rcgroups.com/forums/showthread.php?t=122092) , falconhob's Mars (http://www.rcgroups.com/forums/showthread.php?t=696752) , and flypilot's Sealand (http://www.rcgroups.com/forums/showthread.php?t=683121) should give you an idea of how Ivan design's his planes. While Ivan's designs aren't the foundation for a "Top Gun" winning model, the above mentioned folks (myself excluded) have done a damn fine job with theirs.

John

[edoc]

Thanks for the help and information guys, I reposted on Scalefan's C-130 thread.
Tim

[eflightray]

To build cheap, scratch build, use brushed motors and nimh.

Scratch built B17, 100" span, balsa fuz, white foam wings, 4 Speed 600 7v2, 4 Olympus belt drives, home made retracts.

The cost is usually relative to the amount you buy as against what you make.

Not exactly a 'scale' model, (I don't actually do scale, just models that look the part and usually fly better, lighter).

[wrenwright]

To build cheap, scratch build, use brushed motors and nimh.




+1

Eflightray,

Can you give some more 'specs on your power system for your B-17?

For an idea what can be done with inexpensive brushed motors and nimh cells, do a search for Rudderman's build thread on the 120" Martin Mars water bomber.

He used four Kyosho Mag Mayhem motors with gearboxes, 10" props, and 18 cells. From the videos, it flies like a dream.

[eflightray]

Wrenright

Here's a link to my thread on the B17, B17 Love hate relationship (http://www.rcgroups.com/forums/showthread.php?t=570555&highlight=b17)

Also my Web site (http://web.ukonline.co.uk/ray.archer/) where there are some pictures and my B25.

I assume you have already seen Ivan's Plans (http://www.geocities.com/ivansplans/) web site where there are plenty of multi engined models, most use brushed motors.