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[tmb51]

Hi All

I am looking at replacing the standard 550 robbe motors in my model for brushless motor but am unsure which ones to go for?

As the boat has been modified for static dive, I'm planning on running it on 7.2V NiMh's

Ideally I would like the motors to be able to be slotted into the existing motor mounts so what ever I replace the originals with needs to have the same fixing positions!!

Any help/suggestions welcomed

Tim

[Subculture]

Difficult to give a recommendation for something like this. Perhaps some of the people with U47's could chip in. A few extra bits of information would help.

What props are you running- diameter and pitch?

What speed do you want the boat to run at? As standard the U47 is quite nippy, as the boat is designed as a dynamic diver. You don't need that speed if statically diving, but some people prefer a fast boat.

Regarding hole sizes, that will limit your choice of motor. I would consider making some adapter plates, as brushless motors can be much smaller than they're brushed counterparts. You'll probably want some new couplings too, as most brushless motors suitable for your tub will be 3 or 4mm shaft diameter.

My thoughts are that a pair of 28-30mm outrunners rated somewhere between 700-1000kv will be about right. I find Hobbyking excellent for inexpensive brushless motors and controllers.

[tmb51]

Hi

I'm running 40mm brass Low-cavitations propeller screws with high output at a low RPM and was looking for something that will give a reasonable turn of speed when needed.  But was also looking for a longer run time as the standard motors, reading around, draw quiet abit and I would prefer a longer running time.

I was hoping to be able to swoop them straight out but making an adapter plate is not a problem, and if I can get 3mm shafts they'll fit straight in.

Will have a look at hobbyking, many thanks

[Subculture]

Okay. I would look towards the lower end of the RPM range for those size of props, in fact you may be able to go even lower still, say 600kv. I haven't tried this motor, but it's very inexpensive and worth a look-

e.g.- http://www.hobbyking.com/hobbyking/store/__6943__TURNIGY_Bell_TR2410_12_600kv_Outrunner.html

I've got one of these 800kv motors, which is superb, very torquey and will spin a 40mm prop easily, as I've tested it on a two blade 50mm X-pitch (70mm pitch) prop, which it spun at over 6000RPM-

http://hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=8622

These are also fantastic motors, but I don't think they will fit into the confines of the U47's pressure hull-

http://hobbyking.com/hobbyking/store/__6246__hexTronik_DT700_Brushless_Outrunner_700kv.html

[nick_75au]

Can't offer any better advice than what Subculture has offered, Spot on IMO

Cheers
Nick

[timsenecal]

i am a little bit late here, but the u47 i have was built for static diving, and used the speed 400 from graupner, which are 1500kv motors, but they were put through 3:1 planetary gearboxes, and all this was running on 5 cell nimh batteries (6 volts), and it was using either the 35mm or 40mm brass props from alexander engel (can't remember which).   this gave a very scale speed

so...  


i would try to find a 28mm to 36mm brushless outrunner that has something around 500kvm rating.


something like the 36mm outrunners subculture showed us on a previous posting:

http://www.engel-modellbau.eu/catalog/product_info.php?cPath=108_217&products_id=2425&osCsid=kfrtrajm3rq2q543grbt6cjrk7

[Subculture]

Not suitable for U47, but Hobbyking do an interesting motor for quadcopters. This is 530kv rating with 22 poles, so it should be a very torquey beast indeed. More expensive than the usual Hobbyking fayre, but still a cheap motor.

http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=17923