Posted by Reegor |
Aug 27, 2013 @ 01:12 PM | 2,022 Views
I've seen so many people doing the same thing that I have copied my advice and put it here for reference.
Syndrome: Buying a "start from scratch" FPV setup, then trying to sell it off bundled together.
Example: Here is a note I wrote to someone who had paid $2400+shipping for a giant FPV setup (the X-8 wing). He was asking $2100, and wanted to sell it as one bunch. In the $2400 he purchased:
A $470, 18 channel radio
$200 for RealFlight, a flight simulator
The actual aircraft and its electronics. It is an X-8, which is huge and awkward - not a good starter aircraft for anybody!
Telemetry, including a GoPro camera, another camera, DVR recorder, HD TV to use as a screen I guess, video RX and TX.
Batteries and charging equipment.
A good autopilot, but one that takes a lot of tinkering (APM system)
===============Here is what I wrote to him ============
You will do a lot better to split it up. For example you have a Futaba 8FG radio. Everyone who appreciates an X8 will already have a radio - only by pure luck will they happen to want another, and to have decided on that particular model of Futaba. Same for the RealFlight simulator - everyone either has one already.
The other option is to find someone who will "take it off your hands" and do the work of...Continue Reading
This flyer was only getting 3 minutes of flying time on his batteries. It turns out he had telemetry readout of his instantaneous battery voltage, and he had set the alarms at too high a voltage. Here is his description, and my response.
Originally Posted by MrMention
I have it set for 2 alarms. The first one goes off when the cells at 3.80 and the second at 3.70. If I back off the throttle the cell voltage goes back up, but I usually fly at half throttle. The plane feels better with 25c batteries vs the 20c I was using.
I dont know if its the prop or what. I also have the frsky amp sensor so I can see how much amps and watts Im pulling while I'm flying but I cant test it yet because I have to update the firmware of the lcd to display the data.
Your thresholds are set too high. 3.7 volts is too high - that's roughly the 80% discharged level of a Lipo. 3.5 or 3.4v is considered the "fully discharged" level. Take a look at this thread for voltage versus discharge curves.
Second, your measurement includes the voltage drop when you are pulling amps. That voltage drop is not accurately representing the true battery voltage. When you are at full power, the V drop could be 1.2volts (0.3 volts per cell equivalent). That means the voltage at the battery is 1.2 volts higher than it is at the measurement point. So a few beeps when you goose the throttle does not mean it's time to come down. (...Continue Reading
Posted by Reegor |
Aug 13, 2012 @ 02:33 PM | 1,978 Views
Here's what I wrote in response to a review of a kit of parts from RTL fasteners. I'll try to supplement it with a specific list of exactly what I got, and what I wish I had gotten.
After reading a review of RTL's non-metric assortment, I was able to put together my own (metric) collection for about $70, from http://www.trimcraftaviationrc.com. I got sizes from M2 to M4, with a variety of ends and lengths. I also combined it with a set from Harbor Freight that had a storage box and large sizes - M5 and up.
Trimcraft charges only $3 for any amount of shipping, and for small amounts they send it First Class mail.
A few comments, wherever you source from. Others with more building experience than I have can probably do better.
The metric numbering system is even better than you suggest. Mn means diameter is n millimeters. So an M3x8 weighs and has strength roughly 2.25x an M2 x 8. (3 squared = 9; 2 squared = 4)
I should have gotten a few M1.5s (1.5 mm)
I got both Phillips head bolts, and Socket head cap. Phillips are easier to use, but for some reason I feel more secure with the socket head. There are various other kinds of heads available.
It's more useful to get a wide range of lengths than to get every possible length in a range. Usually you can make something fit if it's a few mm too long, but if you need 30mm and you only have 25, you are out of luck!
I should even have gotten some Phillips M4 x 40 and possibly M4 x 50. I was trying to use plywood on the inside of a fuse to brace something fastened to the outside.
Keep the parts in the bags and cut a hole in the corner.
I followed RTL's list and got some non-metric screws such as Servo Mounting Screws #2x7/16" . For some reason it's harder to find metric screws than bolts. The screws are very useful e.g. for cowl mounting.