This is my first thread, so this is probably a bit longwinded, but stick with it please!
I was at the Cape Girardeau FLI (great event by the way) with my Sebart Su-29 140 with the following set up;
Futaba FASST 7ch receiver - R617FS
Powerbox Digiswitch (http://www.powerbox-systems.com/e/powerbox_systeme/digi_switch/start.php)
2x Thunder Power G8 2100 mah Lipo (one direct to ign, other through reg to receiver, both situated next to each other)
2x Futaba 9350 (elev)
2x Savox 1268 (ail)
1x Savox 1256 (rud)
1x Savox 0352 (throt)
DLE 35RA
A brief history of the airframe first – it used to be my Dads and he had relatively low torque, non digital servos in it. I bought it about 6 months ago, and swapped all the servos out for those above and everything worked faultlessly until the Cape Girardeau FLI.
Here’s a timeline of what happened;
I first started the engine up and all seemed fine, so I went to take off and it nosed over smashing the prop. At the time, I thought there’s a high possibility that was my fault, as I’d put an aggressive throttle curve on it and wasn't quick enough on the up elevator in the grass. At that stage, someone kindly gave me a new prop and a couple of other people supplied the necessary drill and drill bits.
Ready for the next attempt – as soon as the motor fired, all radio contact was lost – un-commanded full throttle and full deflections (and thanks for a sturdy/ prepared helper!)
After a series of range checks, and moving the lipos about two things were noticed;
· The heatsink of the Digiswitch was at 175 degrees Fahrenheit. (someone had a temperature gun.)
· Moving the RX lipo further away from the IGN lipo seemed to solve the issues, even with the regulator at the temperature above.
We checked the current draw, and with all servos cycling the max draw was 2.8A – too close to the limits of the reg. Regulator manual states capacity as approx. 1 - 3 A (dependent upon available cooling and type of battery) Subsequent testing has shown that the heatsink gets very hot while cycling the servos in an air-conditioned house, so I’m pretty confident that changing the servos out after I bought it has got the old regulator struggling.
Now, acknowledging that the regulator was not really up to the task, why would the radio issues only happen with the motor running?
This system has worked faultlessly for 6 months beforehand, but, the plane has never been out in that sort of heat.
Someone also lent me a CC BEC Pro and that solved the issues as well, but I can’t remember the position of the lipos when we tried that unfortunately. I’ve got a feeling that I moved the lipos back to their original positions to rule that out and no radio problems were encountered.
So, I’m pretty convinced it was a combination of the high temperatures, and the reg being under sized. However, I don’t understand why moving the lipos further apart (with the original reg) would fix it, given that the setup has worked for so long (albeit in cooler temps)
If anyone has any insight, I’d appreciate it. In the mean time, I’ve just got to wait for the Fromeco Sahara (CC BEC Pros were out of stock) to arrive and hopefully that should sort it out.
Finally, thanks to everyone that helped out, I think there were about 6 people at the peak but I’m awful with names, so if you recognize the saga above, give me a shout so I know who you were!
I was at the Cape Girardeau FLI (great event by the way) with my Sebart Su-29 140 with the following set up;
Futaba FASST 7ch receiver - R617FS
Powerbox Digiswitch (http://www.powerbox-systems.com/e/powerbox_systeme/digi_switch/start.php)
2x Thunder Power G8 2100 mah Lipo (one direct to ign, other through reg to receiver, both situated next to each other)
2x Futaba 9350 (elev)
2x Savox 1268 (ail)
1x Savox 1256 (rud)
1x Savox 0352 (throt)
DLE 35RA
A brief history of the airframe first – it used to be my Dads and he had relatively low torque, non digital servos in it. I bought it about 6 months ago, and swapped all the servos out for those above and everything worked faultlessly until the Cape Girardeau FLI.
Here’s a timeline of what happened;
I first started the engine up and all seemed fine, so I went to take off and it nosed over smashing the prop. At the time, I thought there’s a high possibility that was my fault, as I’d put an aggressive throttle curve on it and wasn't quick enough on the up elevator in the grass. At that stage, someone kindly gave me a new prop and a couple of other people supplied the necessary drill and drill bits.
Ready for the next attempt – as soon as the motor fired, all radio contact was lost – un-commanded full throttle and full deflections (and thanks for a sturdy/ prepared helper!)
After a series of range checks, and moving the lipos about two things were noticed;
· The heatsink of the Digiswitch was at 175 degrees Fahrenheit. (someone had a temperature gun.)
· Moving the RX lipo further away from the IGN lipo seemed to solve the issues, even with the regulator at the temperature above.
We checked the current draw, and with all servos cycling the max draw was 2.8A – too close to the limits of the reg. Regulator manual states capacity as approx. 1 - 3 A (dependent upon available cooling and type of battery) Subsequent testing has shown that the heatsink gets very hot while cycling the servos in an air-conditioned house, so I’m pretty confident that changing the servos out after I bought it has got the old regulator struggling.
Now, acknowledging that the regulator was not really up to the task, why would the radio issues only happen with the motor running?
This system has worked faultlessly for 6 months beforehand, but, the plane has never been out in that sort of heat.
Someone also lent me a CC BEC Pro and that solved the issues as well, but I can’t remember the position of the lipos when we tried that unfortunately. I’ve got a feeling that I moved the lipos back to their original positions to rule that out and no radio problems were encountered.
So, I’m pretty convinced it was a combination of the high temperatures, and the reg being under sized. However, I don’t understand why moving the lipos further apart (with the original reg) would fix it, given that the setup has worked for so long (albeit in cooler temps)
If anyone has any insight, I’d appreciate it. In the mean time, I’ve just got to wait for the Fromeco Sahara (CC BEC Pros were out of stock) to arrive and hopefully that should sort it out.
Finally, thanks to everyone that helped out, I think there were about 6 people at the peak but I’m awful with names, so if you recognize the saga above, give me a shout so I know who you were!
Last edited by a moderator: