View Full Version : Help! Spitfire's a little tooooo hot!
Got a minor problem with my spitfire - It's a 28 inch span direct drive speed 400, fitted with Jeti 18Amp speed controller, 8 cell 600AE, running a 5 1/4 x 5 1/4 EP speedcam prop.
Finally got it all rebuilt yesterday after I "borrowed" the electronics for another project, and with it being a brand new set up I thought I would get an approximation on the flight times by stakeing it down and running flat out.
Battery lasted around 6 or 7 minutes - not too bad.
Problem is that when I came to change the battery over, it was so hot I could hardly touch it, and the 4mm gold connectors left a nice pattern in my skin.... /ubbthreads/images/graemlins/blush.gif
I think that running it staked down would put additional strain on the motor and draw a tad more current, but would it make this much difference?
I tried the same pack on the Piper, and though it was warm, it was not anywhere near as hot!
Oh yea, it sure will increase the load, a whole bunch.
The battery will most likely get hot in flight, but not hot enough to burn you.
Also remember that you don't fly at full throttle the whole time either. I'm suprised you didn't cook the controller.
I'm getting a pico jet any day now - it'll be running a similar setup. When I was finding out about the best setup for it, from several people that have flown them. The consensus was to use a Jeti 350 esc (35amp) as it gives better performance & is kinder to the battery packs.
& yes running the motor flat out on the ground will put more strain on the system compared to when it's in the air.....you won't be running full throttle all the time during flight either.
Cheers Guys - I thought it would put a bit more strain - just did not realise how much!!
The speed controller is only temporary - it came in a complete set up I got second hand for a rediculously low figure, so I was not too concerned if it did cook - perhaps I'll be a bit more cautious with it!
As to whether it will need full throttle at all times is a different matter - she's a bit of a beast and needs all the speed she can to get in the air, so although not flat out, it will be certainly be not too far off!!
/ubbthreads/images/graemlins/crazy.gif
probably would have helped if I'd stuck to the plans instead making a fair few mods!!
Did you buy a kit or scratch build?......if scratch build - what plans?
Just interested as I'm making a spitfire at the moment.....only difference is mine has a 12" wingspan.....very small - but hopefully will fly ok....if not I'll make some changes & try again.
Soundman, 12" huh. I just built a 14" tigermoth. eighs 27 grams ready to fly. Rudder/elevator with esc. Uses Selmen Acctuators.
It's built from plans that came in RCM&E, though I moded it to have 4 channel rather than 3, and with undercarriage for smoother landings.
Took it for its maiden voyage last night, and have to say it was less than successful! Tried a grass take off first, but other than a few bounces it just would not get off the floor. I now think there is definitely something awry with the electrics, as it flattened the 600 mah pack in 2 take off attempts, and again it was all red hot. /ubbthreads/images/graemlins/frown.gif
I've checked the AUW, and it is only around 1/4 oz heavier than the original design. Not a minute amount I know, but still, I would not have expected it to cause that much difference!
I'm going to see how much current it's drawing before I attempt any mods to bring the weight down, and am loathed to attempt a hand launch until I know for certain that the electrics are OK.
Not a good flying session last night - I also managed to shorten the Cub by a few inches. What really got me annoyed was yet again it was a mystery as to what caused it - flying beautifully, when all of a sudden half way through a steep banked turn just no response - nose dived straight in.
Sat having a fiddle for 5 minutes, nothing, no response, then all of a sudden just sprang back into life (at least the receiver did - nothing else will be "springing" anywhere for a while!!!)
Ho Hum, back to the workshop!
Lozmod has recently bought a Pico Jet, nice little plane, flies like a $%@£", thats good by the way. Uses an Extra 22amp ESC without any problems.
Soundman - You got the plans for this 12" wing span spitfire? Can you PM them to me, what Electronics and motor are you going to use? IS it foam or Balsa?
The reason that people recomended to use the 35amp esc, is that they used a lower rated one - then installed the 350....it gave a performance boost.
The spitfire is balsa construction, but could be adapted to use foam. The plans were made in 1970 for free flight - so they need a little bit of modification.....but it's all quite straight forward - if it doesn't work on the first build, I'll try again.
Electrics etc. it's going to use an rffs system, starting off using a kp00 motor & prop, going to use some Bob selman actuators if I can get hold of them, power will come from a 145mah kokam. AUW is expected to be somewhere around 25-30 grams, compared to my lil skeeter which AUW is 22.3 grams.
Could I have a peek at those plans as well?
Cheers!
Sao - they're just a humble pdf I'm afraid - but you're welcome to them if you want them.....old stylee hand drawn from the 70's.
Martin - If you do get them in cad perhaps you could run me off some hard copies?!!
I've got a little further with my spit now - swapped out the motor for a new one - remembered it was a "borrowed" 4.8v( /ubbthreads/images/graemlins/blush.gif ) from a previous plank that had taken a nose dive - I think the shaft might be slightly less than true!
I've also swapped the prop for the original off the cub (6x4 standard plastic).
The new 6v seems to have a lot more power and dragged it quickly up my garden, which is both bumpy and steep, with no problems, even managing a small hop, and after 6 minutes of that at near full power on the floor the esc and wiring was still only warm, the battery and motor where only just virging on hot.
Cheers Mate, I keep promising the wife I'll have a 12 inch one someday.... /ubbthreads/images/graemlins/tongue.gif
reddog_20091
02.07.03, 16:58
yeah i want one
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I've got a little further with my spit now - swapped out the motor for a new one - remembered it was a "borrowed" 4.8v
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You don't want to be using that motor direct drive with those props, way too much current draw, hence battery heat.
Jetis are not the best controllers and we don't stock them for a damn good reason.
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