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Hi All,
I’m designing a fuselage for my latest electric. It will be a replacement for the one I built too flimsy for the Satellite 320 wing and tail. Simple rectangular box with a pylon. The width will be about 3/4 inch, just enough to enclose the DT servo. I think I’ll just velcro the battery to the side opposite the timer for simplicity and ease of servicing.
Anybody have any thoughts on this matter? I’m looking for practical rather than elegant. I know all the “experts” likew Bernie Crowe have everything neatly enclosed but they don’t have the number of crshees, er. hard arrivals that I do.
Thanks, John in Kalifornia.
Here is something to remember:
Any structure in front of the battery will need to be re-built after a hard landing.
Batteries on the outside are safe.
Inside the pylon can work but you need it slide in from the front.I’ve just been reminded that the F1Q rules say battery must be tethered to the model. What would constitute a legal interpretation of that rule?
John
John,
The FAI code states: 3.Q.2. Characteristics
External Battery packs are required to have a safety tether to the fuselage.The example I recall are models by Chuck Groth. The NiCad batteries (cylinders) were stringed together to what looked like a long cigar. As Chuck’s models were very light, they were placed under the fuselage held with Velcro straps. The intent was to jetty off the battery in a hard landing. We might have included this in the original US proposal to CIAM to prevent batteries falling from the skies.
But this will not work for a LiPoly batteries as any puncture will eventually cause the batteries to swell and potentially explode. Lipo batteries have to be well protected in landings (downwards and forwards) and easily replaceable with a fresh battery. This site has pictures of various models in other threads you might find helpful and Bernie Crowe definitely knows what he is doing.
In addition, I always use a female Dean connector (small and large) on the batteries side to guard against shorts that will destroy a LiPoly battery immediately. Others use zero-resistance female connectors at each end, clearly marked for polarity. Also note that the connectors are included in the battry’s weight so the leads should be rather short.
Wiring on connectors that CAN be connected backwards is a big NO NO. There is a standard for the Deans Ultras and also the Molex connectors used on R/C cars. Female is always on the power source, like batteries or wall sockets.
On my smaller batteries I use the Deans micro connectors that have a male and female on the plug. The red ones are for the battery and mate with black ones on the speed control and charger. The positive is the female and the male is the negative (ground) on the battery.
You must use the same convention on ALL your stuff or you WILL fry something. The Sermos/Anderson/Powerpole connectors are good but can be cross connected, especially if one is color blind or careless. There is a fuse in the CBA battery analyzer that will blow, hopefully before you hurt something inside it, if you connected it to a battery backwards. Ask me how I know.
John in Kalifornia
I use Jeti gold connectors with the male on the positive and the female on the negitive. It is imposible to connect to the charger or the model incorrectly. The only draw back is unless someone else is using the same configuration you cannot share in the event of a failure or to help another flier out. Scott and I use the same configuration.
I have room enough in my fuselages to move the battery (with female Dean connectors, btw) and adjust the CG. To prevent damage there always is a hefty peace of foam rubber in front, length to fit the CG pos.
Just watch out, that the LiPo can’t move backwards and ruin your trim!One of Trevor Grey’s early electrics carried the battery pack inside his fuselage behind a fly-off door. Inside, in front of the pack was a “ramp” of about 50-60d egrees with a plywood face. In a stall-in or oyher rough landing, the pack will slide forward, kicking the door (mine are attached with magnets) open/or off, both saving the battery and slowing its mass considerably.
My Lucky Lindy has such an arrangement. At the January Eloy biggie, I launched it with less than a full charge: It stalled violently, swooping smack into the C pillar of a parked vehicle. Battery ended up in the truck bed, airplane on the ground about ten feet away. No damage to either aircraft or auto. Bad pilot error, however.
On Dan Berry’s advice, my last fout electrics have “open” pylons that straddle the fuselages, which are just wide enough for the rear facing D/T servo (,44″-.55″). The ESC and its leads are pushed inside from the front, the wires then poking out the timer bay (motor run and D/T lugs to servo), while the battery female is teased out through a hole on the opposite side. The battery pack is then mounted outside with Velcro(tm).
Some might question the sanity/safety of the method, but to date, there have been no incidents, accidental or otherwise. The planes in question range from e36 to 350 square inch units.
JO
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