P68C Advice

[Mike S]

Ok I got this aircraft from gareth and need some advice.



The current motors are brushed RS-380PH



Options

This would need either
1. A 30 amp brushed ESC that can take lipo's and split it out to the motors (but would burn out the motors at full power)
2. a pair of brushless motors and a pair of brushless esc's. (preferred option)


My plan was to use a AR500 with speedcontroller and lipo but Gareth suggested that with the current motors this would burn out at full power. So I want to use brushless motors with speed contollers to replace the old motors.

So any ideas on which motors to get to replace the above and which speed controllers and of course the correct lipo to power it all.

The control surface hinges are the tape type and the tape has dried out so I have to decide if to use tape or to put in hinges

Not much then.

[Sheraz]

easy...

 go IC   

[Tim Marshall]

estimate the AUW  and for scale flying you need 100w/lb -150w/lb.   THen try looking thru  BRC's list of motors for something suitable ;  they don't give suggested prop sizes until you buy   but something with  1500kv might be a good start   125w generally use about 6"  250 w about 9".   Micron have a range as well and both have competitive EScs.   

More data will get you more advice here and on RCME modelflying too....tut tut you were unsure whether your club buddies would be of any use so you posted there as well!

[Mike S]

yep you got me lol.  That sound of wind was all that going over my head Tim. Auw (all up weight) is this with everything in the plane as if ready to fly the reason I ask is I have not got any of the electronics and Of coures the next question how do I weight it?

[Dave]

http://www.towerpro.cn/english/motor/2408.html

two of the 2408, 2409, 2410 series should work well and are cheap (twin 30A ESC)

two of these on my PBY ; very aggressive breaking water surface tension and have enough power to lift an aircraft with allot of water in fuselage
Large delta in power from the brush 380/sp400 (8x4 prop seems to be the ticket)
 

[Mike S]

Thanks Dave....

The motors you suggested are they the new equivalent of the motors that are on the plane at the moment?

What sort of 3cell lipo as in mah power for these if running the suggested 18amp esc and how do I connect the two escs to the receiver?

Do think is shows that i know nothing of electric aircraft.

[Gareth]

Mike,

My plan was to use a AR500 with speedcontroller and lipo but Gareth suggested that with the current motors this would burn out at full power. So I want to use brushless motors with speed controllers to replace the old motors.

The Receiver will be fine, I have a brushed 30amp ESC that i can send your way to try out with those motors. The brushed motors if running at full most of the flight power will burn out over time, I have used one for about 20 flights and didn't have any issues. If you look about online you will find that people do burn them out but mainly when they get flown hard.

With the Brushless motors you could go with an in-runner to go in the same place as the current ones or look at an outrunner that would mount on to the back plate where the current mounts stick out from. I would have thought that 2 small outrunners on 8x6 props would be great, if you look at the right motor setup you could use 20amp ESC's, this would them work on a 3s 2100 or 2 3s 1320's

The control surface hinges are the tape type and the tape has dried out so I have to decide if to use tape or to put in hinges

The Hinge will work with either tape or Mylar. Tape will be easier as you can line it all up and use some hinge tape and stick it all up.
The Mylar will be harder as it will need a slot cutting in at an angle from the closest point on the surfaces, but should provide a tougher joint. I would have thought that the tape if done on both sides would be more then strong enough.

Gareth

[Dave]

PBY was equipped with twin 280 geared motors out of the box (11in props)
Flew one event prior to swap…
My take was…Pulled hard left in the water (no water rudder) 280 motor/prop combo required a gentle touch in the power run up.
PBY rudder is a bit small and the big props made directional control in water difficult UNTIL the aircraft speed was up & the aircraft was on step.
8X4 direct drive worked great for me, able to perform loops and rolls but a bit scary due to the small elevator and rudder
I used one 2200 25-30c battery with no issues (slightly warm to touch after flight)

I have found the cheap bell motors are significantly more powerful than the 380/sp400 battery life is extended greatly

 

[phild]

Mike
 the advice you have been given by Tim is about OK the only thing I would add is that 100 to 150 W per pound is a bit over the top for a twin you will get away with 100w per pound max. I have recently purchased two motors from BRC infact motor and 33amp speed controller as an item for about £33 per side. these will run on 3s batteries. I don't know what size plain you have, but if you weigh it then add about 150grams perside for motor and speed controllers, and probably 250 grams for a reasonable sized 3 s battery.
I wouldn't go to any expense in getting the thing flying with the 2 brushed miters.
 You will need quite a high revving motors as it wouldn't appear that there is a lot of room for much over a 8inch prop.
Phil

[Mike S]

Thanks to everyone for your advice, cant say i understand it all but I am learning. Gareth gave me a lot of advice about the hinges and the motors and suggested asking you guys on here and rcme,

So if I leave the motors,props and servos in then add a rx and 3s lipo then weigh the plane I should get a rough estimate of the auw, I have no idea what the manufacturers suggested weights are. but tried to find the weight and seems to be 2lbs 12ounces.

Wing span length is 52" (132cm), wing width 7.5" (19cm)
Fuselage length is 36" (91.4cm, fuselage width at widest point is 3.5" (8.8cm)

Next question is the servos they are Jamira HES-388N there is two in the fuselage not sure about the ones on the wings yet but might be the same as they are covered over. Not sure of the what volts these servos are as all I could find out about is:

Jamara HES-388 N 31x31x16 mm 24 g, 2.4 kg/cm  0.23s/60.

[Gareth]

Thanks to everyone for your advice, cant say i understand it all but I am learning. Gareth gave me a lot of advice about the hinges and the motors and suggested asking you guys on here and rcme,

I advised about asking on this forum, not about RCME you traitor

Next question is the servos they are Jamira HES-388N there is two in the fuselage not sure about the ones on the wings yet but might be the same as they are covered over. Not sure of the what volts these servos are as all I could find out about is:

Jamara HES-388 N 31x31x16 mm 24 g, 2.4 kg/cm  0.23s/60.

Mike, 2.4kg will be enough (not like its got HUGE 3d surfaces), i would expect them to be 4.8v servo's so using the bec from the ESC should do the job perfectly.

Gareth

[Mike S]

Sorry Gareth my mistake about rcme. Lol.

So if I was to say the models auw was 3lbs then that would be at 100w per lb 300watts at min or at 150w per lb 450watts max power needed

So any setup in this range would be ok

Does this sound right?

[phild]

I would look for two combo 150w motors and 20 amp speed controllers that will be plenty for that sort of aircraft. The bigger the motor the bigger speed controller you will need the costs will go up considerably.

Have a look at BRC Hobbies who do a good selection of motor speed controller deals, If you phone them they will help you out with what is the best setup for the kit.
What size props will fit between the motor mount and the fuselage? you will need to know that so that you can make the correct choice of motor with the correct revs per min per volt. I assume that you have some 3s batteries which will do the job.
Phil

[phild]

I have just had a look at BRC and they have a combo of a BRC2212 10T with a wasp 20 amp speedo for £21 per set. It has 1400 RPV which would work well with a 7 inch prop 7x5 which will give you all you need. That would be my choice for your aircraft. you will need to beef up the firewalls to secure it too but otherwise you shouldn't have a problem.
These speedo's will drive your servos, but remember that with two speedos you will need to remove the red wire from one of them when you set it up.
Phil
Power calc with 7x5 prop on 3s = 164 w 767 g static thrust 17.77 amps with luck that would give very near vertical performance. which is far in excess of what the manufactureres gave you with the 2x 400 cans

[Mike S]

Thanks Phil. I have looked on brc hobbies and found the combo set:

http://www.brchobbies.co.uk/?page=shop&action=additem&item=482

I will order two of these.

Now you said I have to remove the red wire from one of the speepo's can you explane a bit more about this.

Mike