I want to know what the secret is when choosing a Motor for a certain model How do you figure out the proper KV and amperage rating for 64mm 68mm fan units so that when you plug in the battery it dont just smoke the esc & motor

IMHO, it's more an art than a science. There's some trial and error involved, unless you go out and research to find out what other people are using, and simply copy what they have.

That would be great if I know people who flew EDF but I dont so Im turning to the guys on here for help

One thing about fans that is different from prop planes is that you can just change the prop to a different pitch or diameter to alter the amp draw, but you can't with an EDF. Usually you need to start with the model and fan size. You can determine the best batteries - size and cell count- to fit the airframe. The overall weight can be roughtly calculated from that point and the wattage per unit weight from that. You have to research to find out the Kv the motor will need to hit the wattage output for the fan you intend to use. The weight of the motor will also give you a good indication of the maximum power it will accept in before releasing the magic smoke out. You may have to reitterate a few times to get the final design but it usually works for me.

This fancalc site has a few of the higher end fans listed: http://www.s4a.ch/eflight/fancalc_e.htm

Thanks for the link now can you tell me whats it spose to help me do isnt there anyone that reads these forums that can help direct me to get a motor fan combo that dont catch fire the first time you attach the battery???

Well - as was said - some of your own homework would be in order, however - tell us what you are building and what you want out of it.

To ask as you have is very vauge and does not have a simple answer.

You want a sure thing? get a Violet fan setup, it will work... and cost $1,500. Bob has done all the homework for you and done it right.

I have the lexani sr-71 I bought just airframe and wanted to use better motors and gear then what I been reading in the forums about this RTF versions. I bought a pair of electricfly 4850 motors put them in the 64mm fans, balance the unit and with 40amp esc and a 4s 5000mah battery, wired the esc in parallel the first time I test ran the unit and im not talking wide open maybe 1/4 stick the motors smoked and melted the ESC

bro if im going to drop 1500 for a edf I would go the extra 5 or 6 and just go turbine

Well for starters, you need a seperate esc for each motor when using brushless. No idea what to use, but a 40amp esc seems undersized for a 4cell 64mm fan. As mentioned, read some more, look at setups on youtube videos, do more searching...I know it seems like guys are very standoffish in these forums, like they don't want to share info for some reason, but truth is most of the guys really don't have that much experience on here with edf's and can't help ya out that much anways. As mentioned, asking for help is great, but ya need to be as specific as possible, include airframe, what you might already have for equipment and so on...The biggest thing to help yourself out is reading and understanding included instructions that comes with esc's, motors, planes(for power needs). I never had an esc that didn't have at least rudimentary instructions on what battery you can use, basic wiring etc.

It's not that we don't want to share info - but everyone wants everything handed to them these days. To that end you get 10 threads on the same thing in a week.

As for your problems topgun - it's no wonder you melted everything 4850 KV motors on 4S in a 60-70mm fan will run anywhere fromn 50-70 amps! Now I assume you have 1 esc per motor or you would be asking answers for a different problem.

I'll start by telling you there is no cut and dry answer as different quality and type of motors will absorb different powers (low quality, Chinese motors will not do much). Same with batteries, fans, and esc's.

I do have a pair of GWS 64mm fans with 3900 KV motors and on 3S they pull about 17 amps each. Go to 4200 KV and they will pull about 28 amps each. Generally speaking 3000-4000 KV motors are for 3S and 4S anything more than that and you are good for 3S only and upwards of 5000 KV and more is really only suited for 2S. That being said - like everything in life, there are exceptions to this and these are very general rules only.

I somewhat suspect that a 5000mah battery - while good for the amps - is too big and heavy for the plane you are putting it in. (A twin 64mm fan plane). Two of these would probably do well in your plane: http://www.rcgroups.com/forums/showthread.php?t=1138514

I suggest you go to that site as well for anything electric related - everyone hangs out there, with lots of good info.