tamiya pt-15 conversion

[ernest2]

i have started the conversion of my tamiya pt-15 1/72 scale. i have already made the holes for mini-jet and have it attached to the hull already. i am now in the process of figuring how to fit all the electronics and batteries inside the small hull. i have decided on using AA batteries (1800mah). next on the to-do-list is making 2 - 3 battery holder (torpedo shape), which i dont have a clue yet how to make.

[Frank Hurd]

Looks like you have made good use of the Jet Drive. What motor are you going to use?
Frank

[ernest2]

frank i will be using a standard tamiya 540 motor (mabuchi i think).
here's some additional progress pics. i have repaired most of the damaged especially the railings and the antennas. hopefully i will finish the electrical so that i can run this weekend.

[Frank Hurd]

Look forward to some photos of the maiden run!
Frank

[ernest2]

ok, ive just test the pt-15 on the water for the first time and i might say, i'm a bit disappointed with the top speed. doesnt really get into plane, more like running on harbor.
how big is the difference between running 1800mah AA size as compared to 1400mah 2/3A? will it get into plane? the AA's i think just don't have what it takes.

[Frank Hurd]

Ernest, how many cells are you using? Unless you are drawing too many amps on the 1800 mah batteries, changing to sub "C" isn't going to help. If your motor will take more voltage, then that will help. Try adding a cell to see if that will increase your speed.
Frank

[ernest2]

i have measured the amps drawn, its about 3.5-4amps continuos. the problem is the AA don't give enough power. my esc can only hadle 7.2volts. thats why i am considering buying an intellect 7.2v 14002/3a, but no luck here, out of stock, guess i have to try sub-c then

[ernest2]

ok i figured why the AA's were too slow, it the connection between the batteries, made my own bars (out of solid electrical copper wire) and the boat goes out on plane :D . its even better with the sub-c but its also too heavy already.

[Ghost 2501]

looks sweet :)

[Frank Hurd]

Even the first picture looked good! It really looks good-Congratulations!
Frank

[ernest2]

thanks! here's a little video, not very good thou.
http://youtube.com/watch?v=L8hTTMcEHVY

[Shaun Hendricks]

Cute & quiet! That thing wasn't making hardly any noise... very nice build.

[ernest2]

ok i have finished converting the boat to brushless setup and finally have the time to test run the boat, and i was quiet satisfied with the result. i am using a small brushless, 20mm dia x 40mm long and it got too hot after only 2 mins of running (that i don't like). so anybody that have ideas how to cool this visibly underpowered motor is very welcome :D .
anyway here's a little video of the test run. (pls forgive the crappy vid) ;)
http://youtube.com/watch?v=AGJWONPqukU

[Frank Hurd]

Ernest, That boat really moves!
To cool your boat, may I suggest a cooling fan like the car guys use? It attaches to the motor and is actually a small computer fan. I ordered mine from an online shop in China(I forgot who). The units are anodized aluminum and clamp tightly to the motor and the fan is on top. I got the idea from Stephen's thread on his Lindberg PT boat.
Frank

[ernest2]

frank, i actually put a cpu fan on top of the motor, but its rated for 12v and i only have 8cells AA batteries. the motor can diameter is 20mm by the way.

[redboat219]

Ernest2,
Your boat rocks! Even sounds great!

Red

[quicksilver]

hey there, if you want to try water cooling, she'll run well, running the cooling system off the jet unit. Mine works great, she pumps water through at less than 5mph. In fact at WOT I had trouble with leaks from the immense pressure. Were talking over 25mph. However I did fix that little problem. Any ways.

You could put your pickup inside the boat, right above the impeller.....right above. Just drill a small hole for the pickup and put it in flush with the duct, so it obviously doesnt foul the impeller. The centripetal force will pump water up the line. You may have the build up the are a bit to get a good surface to epoxy the pick up on. Heck you could put it out the side of the pump, it doesnt even need to be on top, if you have clearance problems. What ever you do, make sue the pick up is right at or behind the impeller, it doesnt work as well in front of the impeller.

That's another great thing about model jet boats that people dont think about, built in water pump. :)

btw that one line effectively cools my motor, the brushes and the esc. Mines not a very "cool" setup either. But she stays cool with this system.

[der kapitan]

Ernest, your boat looks really great, and I wouldn't worry about the transom looking nonscale. What SHOULD it look like with a drive system like that? ;)

You designed it, the drive concept and all, and it's impressive---. :)

Cool---. :D

[ernest2]

thanks guys! the boat runs great and hope i can solve the heat issue so i can run longer.
quicksilver i have tried that setup in my other boat, though the pickup is at the steering nozzle, i will use that on this boat

[quicksilver]

I only suggested at the impeller if you were concerned about preserving the scale appearance and didnt want a hose on the outside. I noticed I got more pressure off the main nozzle than the steering nozzle, but than I dont know how much space there is on the minijet.

[ernest2]

i have finished my motor cooling and seems to be doing ok, heat is totally gone. but i noticed during testing that the esc and especially the batteries are hot. for the esc i am planning on mounting it on a flat aluminum and run a cooling tube, and was also thinking likewise for the batteries. anybody have any other ideas? i really need to cool the betteries or my pt might become a sub. :eek:

[quicksilver]

batteries actually dont like cooling, they draw power best when they're warm, but if theyre hot, you've got wire/batteries problems. What cells are you using?

[ernest2]

theyre hot in my opinion thata why im worried it might damage the plastic hull. batteries are nimh AA 1800mah, not really designed for high current application.

here's a couple of pics of the watercooling

[Ghost 2501]

AA batteries will bake at high currents, could pop as well

[ernest2]

hi! can i please ask the masters on how to weather my boat? it looks very dry right now and i thought it might be nice to add some rust or dirt on to it. altough theres lots of dust on it right now, but not really what i want. :D