I am embarrassed to say I found out that my EMax BL2820/07 motor had a phosphor bronze or copper ring (like the one in the picture) when I came to reassembly -  I had not noticed it on strip down. OD 6mm, ID 5mm, Length 1mm.  It slips neatly over the drive shaft. I followed advice from an experienced electric F2b flier, and installed it on the shaft between the Eclip and the rear bearing.  Do you guys think this is correct?  It appears to have no internal purpose.

Many thanks.

From my experience, the EMax BL2820/07 is a cheap and cheerful equivalent of a 40 engine. I run mine with an APC 11x5.5 prop and 4S batteries. Spares are also cheap and readily available.

I was using 2200 mAH packs for 5 minutes flights with a Brodak Smoothie - a little on the low side perhaps, but then I don't yet fly square manoeuvres. 

I'm guessing at 20 - 25, but don't have measurements/logged data. I use a 40A ESC with this set up, and it seems to be fine.

Hi Chris,
I've used a lot of the E-Max/Arrowind 2820 motors and they work really well for a .40 size engine replacement. The E-Flight Power 15 is about the same but a better quality motor. Most likely the Cobra 2820/12 is about the best deal right now, so you have a lot of choices. The battery size also has to do with what is readily available and popular for the R/C models, so the 4 cell 2200 mAh 25C is a good choice for a 5 minute motor run. You don't need a higher C rating than 25 for C/L stunt.........you just add weight. However the battery size all depends on the weight of the model. I've added a chart of one of my old test models called the Eze 40 and it weighed 1100 grams or 38.8 oz. It flew the pattern easily on that battery for even a 5 min 30 flight with the APC 11 x 5.5 E prop. Most of the profile models I've tested for this size weigh from 1100 grams to 1300 grams (46 oz). At 46 oz the 2200 battery is pushing it's limit for a 5:30 flight, so the trick here is to keep the weight down. Something like a Banshee can be built light if you get rid of the heavy nose with those engine bearers. Electric motor's do not vibrate like the older engines............especially the Fox 35, so it's not necessary to make such a solid nose. It sure needs to be rigid, but does not need to be anywhere near as heavy.

You can see from the chart below taken from my Eagle Tree data recorder just how the current goes up and down during the flight. The average for that flight was around 18 amps, so your guess of 20A is pretty good! There are many threads on this site that show how to calculate everything and that is what makes e-power so nice. You don't need a dyno to work out power as everything is easily measureable. The other trick is to just keep asking questions on this forum and many will jump in and help. Have fun!

Keith R

My pleasure Chris. If you need some ideas on a simple electric nose construction, I have the plan of my Eze-Pro profile stunter that has been built many times. I also have some photo's to help, so send me a PM and I'll get your e-mail to send you stuff if you like.

Keith R