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[Z750Jay]

Hi
Decided to go down the brushless route for my springer tug like thing I am building. I am trying to work out what size motor I need. The prop size is 60mm dia in a fixed kort nozzle and I am going to be running at 6v from a pair of 7Ah batteries that will be in parallel.


I was thinking of something around the 800 - 850 kv mark - not going for scale speed,just plenty of pull and if I can obtain stupid speeds for my Clarkson moments it would be great

[Calimero]

Speed and pull are two different things. If you want pull the propeller will probably have a much bigger impact than the motor.


For maximum pull a low pitch ratio (0.8-1.0) prop with wide blade area will get you the best result.


Do you already have the props ? What diameter and pitch are they ?


I think 800kv is too fast for a 60mm prop. I run a 40mm (Raboesch 147) prop with a 800kv@6V motor. Springer tends to dive at full throttle. But it offers great pull with a 45mm low pitch prop (Raboesch 174).


I'm using this outrunner from Hobby king: http://www.hobbyking.com/hobbyking/store/__29478__Turnigy_Aerodrive_SK3_3542_800kv_Brushless_Outrunner_Motor_UK_Warehouse_.html


With my 50mm props I'm going to use two of these (620kv):
http://www.hobbyking.com/hobbyking/store/__29414__Turnigy_Aerodrive_SK3_4240_620kv_Brushless_Outrunner_Motor_UK_Warehouse_.html?strSearch=4240-620


While you can certainly keep speed down by limit travel on the throttle channel, I'd still choose the right motor from the start.


And if you're building a shoebox/springer, speed is essentially a non issue.

[Z750Jay]

I am using the Robbe kort nozzle with supplied 60mm props. 3 big broad blades - not sure of pitch but they look like a low speed lots of grunt style to me.
The ones you linked to were out of stock so I am probably going for these


http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=29477


Just got to work out which ESC to go for

[Calimero]

I went with a 1/10th car 60A ESC, this one: http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=29642


For my next project, I'm going to use a smaller/cheaper one: http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=28715


You need two of these, as each motor requires its own ESC unlike brushed motors.

[Z750Jay]

Ordered the motors and the slightly more expensive ESC, now just waiting on the postman

[Z750Jay]

Thanks for all the advice and I did remember together a programming card for the ESC whole I was at it!

[Calimero]

I also got their Trackstar programming card: the parameters displayed on the card don't match what the manual says. I was a little puzzled.


Now I program my ESC over the TX (throttle up sequence and so on). Takes 5 minutes and an inordinate number of BEEPs but it works quite well.


I see that the motor you ordered has 4mm bullet connectors. Small power ESCs like the one I linked usually come with 3.5mm bullet connectors. HobbyKing has adaptation plugs or you could of course snip the connectors on either the ESC or the motor and solder the appropriate diameter connectors.

[Z750Jay]

I am lucky, I work in Portsmouth Dockyards electrical workshop refurbishing/rebuilding all sorts of electrical stuff so have access to an array of electrical repair and building components plus my own work area.
The boss is quite happy for me to "practice" my skills at lunchtime so

[Calimero]

Ha ha ! You should be able to find some sort of suitable connectors. 

[Z750Jay]

Not had a chance to start the build with all the BBQ's that I have had to go to.
Having sat while waiting for SWMBO to get ready looking at my box of bits and having found an old Seaport hull in the loft the other day I thought I could  put one of the motors in it and finish off the çonversion. Then I could get stared on the springer thing as bulďing the hull toom me ages last time