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Please help with motor size/amps/compatibility

#1
Hi All :)
I got a little overambitious with my first planes and learned the hard way that I should have started with training wheels. I already have the C power pack motor but the next models (tiny trainer, simple scout, FT flyer) I want to build call for A and B packs. I wanted to buy motors that were close enough in specs but had un-threaded shafts so I could use prop savers. I ended up ordering (shipped but not yet received) the Turnigy D2826-6 2200kv for the A and Turnigy D2826-10 1400kv as the B pack, along with a couple 800mah 20C (30C for 10 sec) batteries. I was anxious and overwhelmed when ordering late at night and overlooked some details like dimensions, amp draw/C rating. My ESC is a 35A that can handle 45A for 10 sec. I'm afraid I just bought myself the following problems...

-Both too large in diameter for the firewall/noses of FT designs using A/B packs
I'm guessing a little creativity can solve the size problem in most cases but not sure it's worth the trouble.

-On the heavy side for small planes
Enough to mater? I plan to fly slow for a while so I do want to keep weight down but not sure 20-30g will be noticeable in planes this size.

-Drawing too many amps for battery
Not sure how to do the math on this but https://www.ecalc.ch/motorcalc.php does actually have the 2200kv motor in the demo version, looks like I might be ok on that one regarding the 20C rating on the battery.

I'm a little confused by the FT store, the B pack motor is 935kv but FT 3 pack which uses a B motor suggests 1300-1500kv. Should I return both motors and batteries? If so, what do you suggest I get as suitable A and B pack motors? I'd rather return the boxes sealed for a full refund than open and test (though I do have telemetry that'll show amp draw).

Thanks!
 

DamoRC

Well-known member
Mentor
#2
If you have your heart set on smaller builds then theD2826s are oversized for the planes although I suspect the tiny trainer could handle the 1400kv model and might not fry your battery if you prop to the small side.

The 2200kv will likely hurt the 800mah battery - it's a 350w motor. Say on 3S it pulls approx 30 amps max. Your battery can deliver 0.8 (the mah converted to amp hour) x 20 (the c rating) which is 16 amps.

There are a number of FT planes that's would work well with these motors but if you want the smaller lighter slower planes then you'll need to send these back.


DamoRC
 

Merv

Well-known member
#4
Your 2826 motors will fit nicely on the FT fire wall. @DamoRC is correct, your battery will only give 16 amps. Sounds like you could use a larger battery. The 2826’s & larger battery (2200 3 s) will work nicely in a Storch or Bushwhacker or any other FT plane of similar size.

So I start with the plane, what size motor will it take, start with the recommendation. Next how many amps will it draw. Next get an ESC that can supply the motor plus a few more for the servos. An ESC with more amps is not a problem, so long as the weight is not an issue. Finally size the battery to supply enough amps for the motor & servos, again more amps are not a problem, but the weight could be.