ORIGINAL: BIKERBOBW
<p class=''MsoNormal'' style=''margin: 0in 0in 0pt''><font size=''3'' face=''Times New Roman''>Hope some can help me develop a drive train for a PT boat that I am building. I am new to RC so have a lot of questions.</font></p><p class=''MsoNormal'' style=''margin: 0in 0in 0pt''><font size=''3'' face=''Times New Roman''>The PT boat is at a scale of <st1:time minute=''20'' hour=''13''>1:20</st1:time> so therefore will be about 48” long and guessing at a weight of 20lbs with batteries motors etc.
I am hoping to get it up on a plane and a run time of 30 mins. Is this run time achievable and realistic?</font></p><p class=''MsoNormal'' style=''margin: 0in 0in 0pt''><font size=''3'' face=''Times New Roman''>I am considering Gaupner speed 600 or Astro marine 425 motors running on 12 volts each; with all 3 running forward and only the ctr <span style=''mso-spacerun: yes''> </span>capably of reverse. Will these motors achieve my desires or will smaller motors work?</font></p><p class=''MsoNormal'' style=''margin: 0in 0in 0pt''><font size=''3'' face=''Times New Roman''>What would you recommend for batteries Gel cell or NimH cells? If NimH how should the pack be built; 10 cells in series = 12 volts but how many in parallel to achieve run time?</font></p><p class=''MsoNormal'' style=''margin: 0in 0in 0pt''><font size=''3'' face=''Times New Roman''>Finally can you recommend a ESC that can handle the above? Will I require a ESC for ea motor?</font></p><p class=''MsoNormal'' style=''margin: 0in 0in 0pt''><font size=''3'' face=''Times New Roman''>Thank you for your consideration and await your reply</font></p><p class=''MsoNormal'' style=''margin: 0in 0in 0pt''><o
><font size=''3'' face=''Times New Roman''> </font></o
></p><p class=''MsoNormal'' style=''margin: 0in 0in 0pt''><font size=''3'' face=''Times New Roman''>Robert G Wager</font></p>
</p>
Ok, well yes you can run either of those motors. On that size of boat using three motors will certainly get you up and planing. With the Graupner 600, I suspect you can get it up on two motors.
If you want to run all three motors, with only the center running in reverse, I suspect that the easiest way to do this is to run two ESC controls. The two out board motors run on a forward only R/C type ESC with the braking feature disabled, and the center motor running on a forward/reverse ESC. You can look at ESC from Mtroniks, I have had good results with them. The Viper has a reverse that can be disabled, and the Marine series have proved to be fairly reliable.
As for batteries, a boat that large can carry SLAs, but they will be heavy. I would go with some NiMds and run them in two to three packs of 10 set in parallel, that should keep you running for a while. Plan on about 10-15 minutes full speed run time if you have some good matched cells. Keep an eye on the c-rating of your batteries, I would go for 15 C or above.