Model Boat Mayhem

Technical, Techniques, Hints, and Tips => DC Motors (Brushed) and Speed Controllers => Topic started by: colin-stevens on July 28, 2012, 07:44:51 am

Title: What motor size for a 'Russian G5'
Post by: colin-stevens on July 28, 2012, 07:44:51 am

Just received my new project (Russian G5 motor torpedo boat) and am looking for motors. she is 965mm long with 180mm beam(approx). reckon i will want 40mm props. she has a stepped hull. been recommended 1700kw brushless. done a bit of searching and ended up none the wiser. can any one help?

Colin

Title: Re: mototor size foe russian G5
Post by: nick_75au on July 28, 2012, 08:16:36 am

What voltage will you be running, 1700Kv on 7.2 Volt max, a 1000Kv-1200Kv 28 mm out-runner on 12 volts (3 cell Lipo) per shaft would get her going, shouldn't need more than a 40 amp esc per shaft. Any particular info you need?

Nick

Title: Re: mototor size foe russian G5
Post by: colin-stevens on July 28, 2012, 09:12:39 am

err. all i know is i dont want to use Lipo. got a feeling its going to be a wet boat. I have 7.2v on the shelf, where they have been for some time, reckon they are  trashed as not taking long to discharge/charge. so new batteries as well. never did get motor set up, always trial and error, especially on fast boats, and looking around seems that brushless are quite a bit more expensive, and a damned more choice. Not even sure whether to use outrunner or inrunner so any pointers much appreciated. not a lot of room in the hull so battery power will be consideration.
Colin

Title: Re: mototor size foe russian G5
Post by: HS93 (RIP) on July 28, 2012, 09:34:55 am

are you just running a single motor? if so you can up the revs/speed by using two 7.2v nimh packs 14.4v I dislike li Polly in scale boats it is so easy to kill them even with an alarm fitted on them


Peter

Title: Re: What motor size for a 'Russian G5'
Post by: nick_75au on July 28, 2012, 11:26:41 am

I prefer out-runners and would pick a higher voltage over a lower one adjusting the Kv to suit, Dont know about more expensive, can get a combo ESC and motor out of china for under 20 pounds plus shipping.

http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=8495   9.50 Pounds

http://www.hobbyking.com/hobbyking/store/__24567__HobbyKing_30A_Boat_ESC_3A_UBEC.html  8.25 Pounds

Run on 10 cell Ni-XX

Pretty similar to the combo I used in the Glynn Guest Miami Crashboat hull

(http://static.rcgroups.net/forums/attachments/1/4/2/9/4/2/a1995098-24-Picture%20020.jpg)

Nick

Title: Re: What motor size for a 'Russian G5'
Post by: colin-stevens on August 02, 2012, 06:35:52 pm

Thanks for that. Been doing some looking and found this one, seems to me to be a bit more powerful, can any one tell me if I am right?

motor Size: 2858
RPM/V: 2630kv
Max Load: 38A
Max volts: 14.8v 2~4s
Max Watts: 700w
Resistance: 0.0222

Title: Re: What motor size for a 'Russian G5'
Post by: nick_75au on August 03, 2012, 06:32:44 am

My opinion is the Kv is too High even on 7.2 volts. you want about 12000 RPM maximum on the 40 mm prop.

The boat I ran in the picture ran 2 different out-runner setups, a 1000 Kv direct drive and a 3200 Kv with a 3:1 gearbox on 10 cell Ni-mh. The result was the same ok2

Nick

Title: Re: What motor size for a 'Russian G5'
Post by: colin-stevens on August 03, 2012, 12:05:13 pm

Cheers for that. Going with your original reckomendation. Just might get a higher Amp rated ESC to cver me if i want to change motors. will that work? and thanks for taking the time.

Colin

Title: Re: What motor size for a 'Russian G5'
Post by: nick_75au on August 04, 2012, 12:59:52 am

Nothing wrong with using a higher amp ESC. Its a boat so weight is less of an issue.

Nick

Title: Re: What motor size for a 'Russian G5'
Post by: colin-stevens on August 04, 2012, 06:30:56 am

thanks again. after nearly 2 months of not making my mind up going for your suggestion. thanks for the time.
there will be a build thread soon, so watch out in the warship section.

Colin

Title: Re: What motor size for a 'Russian G5'
Post by: colin-stevens on August 05, 2012, 11:38:54 am

I have ordered 2 motors & 2 ESC as per youre suggestion, thanks again.
Would i need the programming card, whatever that may be?
Cheers

Colin