Boomerang1

I'm used to building jets & larger scale models but a friend bought a 'job lot'of
old engines & I ended up with a near new Cox Pee Wee complete with throttle sleeve.

Time to finally complete & fly my 'first' radio model, a Roaring 20.

I never got his to fly as I could not get the DC Dart diesel engine to run properly.

The original had Mattel pulse radio. - John.

vicman

My Feedback: (10)

Welcome back to reality my friend
Going 2.4 with this one?

Boomerang1

Yep, back to my roots!

27 mhz radio is long gone so it's either a 36mhz reciever or Futaba 2.4

I have some tiny servos so I'll check out what's available in the way of recievers.
What's the go on light weight batteries these days?
Tiny 2 cell lipos with a reg or is there something small, light & avaiulable that will plug straight in?

John.

vicman

My Feedback: (10)

I haven't drank the lipo/regulator kool aid yet but there are some pretty nice 5snimh with about 350mah that do nicely.

Boomerang1

Thanks, I'll snoop around for 'normal' batteries.

I have been making my own regulators, really easy to do & just 3 components, a chip & 2 capacitors.
I use them on models to seperate retract servos from the flight servos in case gear gets jammed, I tap
off the motor lipo batteries instead of the radio battery.


John.

Trisquire

It looks like a mini Top Dawg.

Boomerang1

Not surprising, it's from the same designer, Ken Willard.

There was quite a few similar designs around at the time, sort of a half way step
between the safety of a high winger & those scary low wingers! - John.

Raymond LeFlyr

My Feedback: (2)

For my 1/2As this past season I have used 1S lipos and a cheap regulator from Hobby King. For as little as I used Nickel-based batteries in the past I rarely got two seasons from a receiver pack. Given how cheap (and available) these 1Sers are - I feel that I'm ahead of the game (also I fly a lot of UM ARFs - sorry I couldn't resist the little cuties).

Boomerang1

1S or 2S lipos?

1S is only 3.7 volts. Do you mean you use 2 x 1s cells & solder them
to make a 2S pack then regulate them back to something like 5 volts?

John.

Raymond LeFlyr

My Feedback: (2)

Nope, Maybe I used the wrong term (Regulator) but what I have boosts the 3.7 volts to 5.0. For what its worth I have a 1S charger that works off 3S lipos and can do four at a time so I can keep 'leckies in the air constantly.

MJD

My Feedback: (1)

If you're going 2.4 then how about a LiFe 200mAh pack, 6.6v, and no regulator?

Or if you use your own regulator, then a 430mAH or 200mAh LiPo down to 5v will do nicely.

Boomerang1

Most recievers are fine on higher voltages but some servos get a bit angry.

Not sure about mine, I have some GWS picos & a heap of little cheapies from Hobby King.

Raymond, any more info on the gadget that boosts voltage? Make? Model? Home made?

John.

vicman

My Feedback: (10)

Purple pill

Raymond LeFlyr

My Feedback: (2)

Contrary to what poor ole Vic may think about my reliance on the advantages of "better living through chemistry" - - - here's what I happily use in my 1/2As . . . (Please don't judge poor ole Vic harshly, sometimes he confuses me with the super heroes that he grew up dreaming about. tsk tsk)

http://www.hobbyking.com/hobbyking/s...dProduct=11784

Boomerang1

Would certainly help deliver the juice!

I noticed Raymond's post mentioned HobbyKing, found these gadgets:

http://www.hobbyking.com/hobbyking/s...dproduct=11784

http://www.hobbyking.com/hobbyking/s...idproduct=7884

Both boost a 1s lipo from 3.7v to 5v to power a reciever. Cheaper than purple pills to! - John.

Boomerang1

All in the timing, Raymond was posting while I was searching! - John.

Raymond LeFlyr

My Feedback: (2)

Yes, I can identify with the importance of timing - I'd like to type some more - but it's time for me to take my medications.

toolmaker7341

boomerang1 can you post what components needed to make a regulator 7.4V down to 5V

Thanks

Trisquire

I noticed that the box says, "Designed by Ken Willard, noted R/C flyer and Nationals Winner." Would anyone happen to know what event Willard won at the Nats?

Raymond LeFlyr

My Feedback: (2)

Given that I'm trapped here due to a "Wintry Mix" I will waste your time with my conjecture about Ken Willard's NATS win . . . Is it something to do with sailplanes?

Given that his designs were mostly "sporty" and small ones to boot - except for one slope glider that I can recall (was it Topsailer?)

For what its worth, he ranks among my favorite designers along with Clough and Malmstrom.

Now I'll go back to watching daytime TV.

Boomerang1

Busy yesterday, shopping for a reciever & tiny wheels, downloaded & printed a plan,
dug out some servos, park flyer control horns, canopy & carbon tubes for pushrods.

I promised myself to finish my last project before starting another one but the Roaring 20
is so small it won't disrupt things too much.

I really should mix some fuel & give the engine a run. The mix I've found is:

Castor oil - 10%
Coolpower Synthetic oil - 10%
Nitro - 15%
Methanol - 65%

Should that be ok?

Mike, this is the voltage reg I use, just 3 parts, the chip & 2 tantalium capacitors.
I have used it on 3 cell lipo packs but it can probably handle much higher voltages.
Excuse the drawing, it was done on some default program on my laptop.

I usually make an aluminium bracket to mount it to the model & this acts as a heatsink
but it doesn't have to be very big. The higher the voltage of the large battery the harder
the reg would have to work & the more heat it would have to dissipate but from 7.4 volts
to 5 volts is a very small step. Keep in mind also, the more servos the greater current &
more heat. You should be fine driving 4 average servos & a reciever. - John.

fizzwater2

My Feedback: (61)

let's say you have an average current draw of 500 milliamps.

At 7.4V in, 5V out, the regulator will be dissipating about 1.2 watts ((7.4V-5V)*0.5A = 1.2 watts.

A 3S Lipo, 11.1V = (11.1-5)*0.5A = 3.05 watts. that would require some heatsinking for a TO-220 package. Stall a servo for a bit, the current goes up quite a bit, and power dissipation in the regulator goes right up with it.

A linear regulator like the LM7805 makes for nice quiet power (little electrical noise) but isn't very efficient at all.

You can find switching regulators (sometimes referred to as "BEC", or battery eliminator circuits) that are a lot more efficient at the expense of some power supply noise.

Castle makes a pretty neat little 10 amp regulator that I've had good luck with.

vicman

My Feedback: (10)

I made a glo igniter based on avery similar circuit to Boomer's

fizzwater2

My Feedback: (61)

Raymond - that Hobby King thing you showed is a "boost regulator" - a switching regulator that steps the voltage up from your input voltage to a regulated output voltage of 5V.

Other types of "BEC" things that require a 2S or higher input are "buck regulators" that are switchers that step the voltage down to 5V from your input voltage.

The LM7805 in the post above is a linear regulator - only used to reduce voltage to a regulated output. Essentially the same current flows into the input as flows out of the regulator, so any voltage overhead is just dissipated as heat in the regulator. Not very efficient when compared to a switching regulator.

Me, I've been using 2S LiFePO4 batteries (LiFe) without regulators, but haven't been flying any small planes. For those I'm tempted to use a 2S LiPo with a lightweight BEC, probably from Hobby King, because I'm cheap.

MJD

My Feedback: (1)

I recently bought a couple of the lightweight Novak 3A regulators for 2s LiPos and small models, 8g IIRC. They weren't too expensive.