RC Submarines RC submarine discussions.

HELP PLEASE! Problem with Robbe U47 U-Boat running Rokraft 8367 ESC

Reply
Old 04-03-2014, 08:21 AM
  #1
jasona
Thread Starter
 
Join Date: May 2003
Location: FramlinghamSuffolk, UNITED KINGDOM
Posts: 256
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default HELP PLEASE! Problem with Robbe U47 U-Boat running Rokraft 8367 ESC

Hi everyone,

Well I'm stumped.

I acquired a beautiful Robbe U47 running the Rokraft 8367 ESC. It has worked fine for years, but has just recently started playing up.

There are two big batteries for powering the twin motors, and a smaller, separate RX battery for powering the receiver (I was always puzzled as to why they did it that way in this age of BEC). It's also wired through what appears to be a relay. Is that what it is? I mean the blue thing next to the ESC - see picture.What is that?

So here's the problem:

  • The motors only turn on a fraction of throttle, in both forwards and reverse. Full throttle and they stop.
  • I've re-calibrated the ESC several times, but still the same problem
  • The batteries are all healthy - they all cycled up to capacity
  • I got a 30 amp mtroniks marine ESC, and tried connecting it up in the same way as the existing set-up: Still incorporating the RX battery, still going via the relay (if that's what it is). Everything worked and the ESC responded to the transmitter, but the motors wouldn't turn over
  • I then tried a more modern, standard, simplified set-up: No relay, no RX battery, just connecting the Mtroniks ESC directly to the motor batteries. Again, everything worked and the ESC responded to the transmitter, but the motors wouldn't turn over

Therefore, I'm stumped! I've put everything back to how it was and have started looking for another Rokraft 8367 ESC, but they're bloody expensive for what they are.

Any suggestions?

Many thanks in advance, really hope to hear from someone!

Jason.
Attached Thumbnails
Click image for larger version

Name:	U47 ESC.jpg
Views:	132
Size:	874.9 KB
ID:	1983679   Click image for larger version

Name:	UBoat ESC RX & Relay.jpg
Views:	232
Size:	516.2 KB
ID:	1983680  
jasona is offline  
Reply With Quote
Old 04-07-2014, 03:04 AM
  #2
jasona
Thread Starter
 
Join Date: May 2003
Location: FramlinghamSuffolk, UNITED KINGDOM
Posts: 256
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

Anyone? Anyone? Bueller?

Otherwise, I'll just order another 8367 ESC and see if that fixes it.
jasona is offline  
Reply With Quote
Old 04-23-2014, 02:35 PM
  #3
subsinker
 
subsinker's Avatar
 
Join Date: Jan 2004
Location: Dwight, IL
Posts: 518
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

Hi,
If you have already replaced the ESC and that didn't fix the problem then obviously that is not your problem....the reason many people have separate battery packs for the receiver (including myself, I do it too) is to prevent the esc from shutting down and the model not responding to commands should the main drive batteries go flat. True, it does create a little more hassle with batteries but what would be worse, an extra battery pack to maintain or swimming for your U-47? I personally would try an other radio, see if that fixes the problem. If that is not your problem, try the motors. The stock Robbe motors are fair at best. They draw a ton of current and over time they may have gotten even more power hungry.
subsinker is offline  
Reply With Quote
Old 04-23-2014, 02:38 PM
  #4
jasona
Thread Starter
 
Join Date: May 2003
Location: FramlinghamSuffolk, UNITED KINGDOM
Posts: 256
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

Thanks so much for replying! The radio is fine, in that everything else is responding, so I guess it's motors next!

What are the stock motors on the Robbe U47? Speed 600 or something? So what would be a present day equivalent of that? I mean, which motors could make eligible replacements?
jasona is offline  
Reply With Quote
Old 04-23-2014, 03:38 PM
  #5
subsinker
 
subsinker's Avatar
 
Join Date: Jan 2004
Location: Dwight, IL
Posts: 518
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

I used Al Matevas setup...expensive but it is belt driven, reliable and draws less than half of what the stock motors draw. http://www.shipsnthings.com/indexNS.htm
subsinker is offline  
Reply With Quote
Old 04-24-2014, 06:10 AM
  #6
jasona
Thread Starter
 
Join Date: May 2003
Location: FramlinghamSuffolk, UNITED KINGDOM
Posts: 256
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

Thanks again!
jasona is offline  
Reply With Quote
Reply


Thread Tools
Search this Thread
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off



All times are GMT -8. The time now is 02:58 AM.