Motor for pusher jet

[patrnflyr]

I've posted earlier on the HL Sukhoi XXL thread but I need a little help in explaining to me this motor choice. The plane should be arriving by the "mail chick" today (even though mine is a middle aged bearded one!). I have an Eflite 400 4200KV inrunner motor and an EFlite 400 outrunner. I thought that if I lowered down the diameter and pitch of the inrunner's prop enough (something like a Zagi prop), I could use it as a direct drive motor for this jet. It was in a Cobri gearbox flying 3D stuff and has performed very well there. I plan on using it with a TP 1320 3 cell battery (new generation) and CC25 ESC. Do I really need to go and buy another motor or can I use this. I definitely don't want to buy a brushed ESC for the stock motor so that's out of the question. I am totally brushless in all my equipment. Thanks in advance for your help.

[srh990]

The outrunner is a better bet, running the Eflite 400 4200kv through Motocalc with a Gunther prop shows around 50A peak. This motor is only of any use in a gearbox, you can't get a small enough prop to use it with the setup you have!

[patrnflyr]

Thanks alot for your advice. Guess I'll have to go with the outrunner! Here's another question. How do the stock brushed motors work then as a direct drive "speed 400"? I would think they would need a gearbox also to keep it reasonable. Better yet, I think I'm just going to have to get some book to learn all about electric motors so I can figure this out. I can't keep bothering each of you every time I get a new model!:o

[srh990]

Unfortunately as soon as they write the books they're out of date! I'm not sure of the correlation between a brushless motor direct drive & a motor called a 400 which is only useful in a gearbox, maybe its down to relative kv's & efficiency?

It might be worth trying the trial version of Motocalc, I've got the full version now and although its not always totally accurate it does give an indication of the differences between various setups.