low turn motors

[BoatDoc]

what is about the lowest number of turns that i can run in a boat? i've heard not to go below 12 because of a lack of torque. i can buy parts and build down to 8 turn motors and i'm wondering if it's worth it.

[MattHiggins]

"i've heard not to go below 12 because of a lack of torque."

In my opinion, that used to be the case a few years ago, but today's electric motors have much more overall power. I don't believe a 6-turn would be a hot setup in a boat, but with newer, stronger magnets in today's motors, I believe you could easily find a 10-turn or 9-turn with enough grunt to get a boat up and going.

[BoatDoc]

i'm thinking about a motor with either 8-10 turns...probably a double or a triple. i'm trying to build a 4 cell 'rigger. it will be for straight lines runs only so i'm not concerned about having power through a turn. it shouldn't be very heavy, i'm going to do a foam/glass build up. it's pretty much a project for fun just to see if i can do it.

[MattHiggins]

If that's the case, I'd just get the lowest turn you can find. Sounds like a fun project. Let me know what kind of results you get.

[kelleysislander]

Y'all,

Take a look at AstroFlight's marine motors, especially the AstroFlight 25 Marine. 5 turns, 6-18v, 20-50A, 1550 rpm/volt, and it can handle 500 watts. They make the Cobalt 05 for electric flight, 7 turn, 400 continuous watts... which can be easily adapted for a boat.

Those motors aren't even in the same league as the "can" motors out there. They are the most energetic little things you'll probably ever run in any application. They were originally developed for electric flight and have set a number of records...

HTH,

bk

[BoatDoc]

i'll be sure to check that out. my plan right now is to build a motor using a trinity can and integy arm. i'll most likely use a P-94 endbell. i'll add water cooling to the endbell as well. the cells will be integy matched GP3300's and i haven't decided on the ESC as of yet. this boat will be almost 100% scratch built. weight is the major concern on this project. as for those astro flight motors...the rpm/v rating probably won't be enough as i'm only going to have 4.8v. this little project is still only in early planning...i need to make sure that i can get everything i need and keep it within my budget before i really get started.

[Fluid]

Double post, sorry. See below. :rolleyes:

[Fluid]

You cannot choose an 05 motor without knowing the intended use. How many cells? Hydro, cat or mono? Direct drive or geared? Surface or submerged drive? Sport running, oval racing or SAW? Without knowing these points, you'll likely choose the wrong motor.

You mentioned 4.8 volts so I'm assuming 4 cells. I hold the NAMBA 4-cell SAW mono record (34 mph) with a 7-turn Reedy Ti, but that is too much motor for anything but SAW running - I'd not run it for longer than 45-60 seconds. I've run 53 mph with my 4-cell rigger with a geared 5-turn, and the record holder (53.7 mph) runs a 6-turn direct....again these motors are not for sport running, they will burn up if run for longer than 45 seconds. For sport running you'll get almost as much speed with 8 or 9-turn motors but they will be much easier on your cells and ESC. The ESC is the next problem....no waterproof ESCs are currently made which will work on 4 cells. You can get an older Novak or Tekin car controller and try to keep it dry....

Light weight is important, but even more so is boat design and setup. Wire drive is the best for top speeds, we use 0.047" wire for SAW racing but 0.098" flex cable is almost as good. Use the shortest wires possible, the best connectors, align the drive with the motor perfectly, sharpen the prop and make certain that the ride surfaces are perfectly smooth and straight. Do not use a tiny boat for high speeds - 20"-22" is small enough for high speeds but large enough to be able to run on non-perfect water. Good luck and let me know if I can help.

[n.h.schmidt]

Hi BoatDoc I wish to ad a few things to Fluids advice. His advice is very good and you can't go wrong using it. I just want to fill in a few holes. For a speed control the Hughey three speed control will work very nicely. It can switch any amt. of current you will likely use. Very reliable and no glitching at all ,even with AM radios. You have to use a seperate receiver battery . You would likely need a receiver battery for a esc too because they tend to brown out with only four cells to draw on for the BEC. I have watched Ed Hughey himself using these controls at Batavia for the last five years,including 4 cell riggers. Probably the most reliable 4 cell setup there is.
I have seen 6 turn motors used in 4 cell riggers when used with a gearbox. With the gearbox you can control you amp draw easily. Very fast too. For a prop the X632 is good or a 1732 .
Fulids advice about the boat size is right on. You can't go smaller just because of four cells. Many have tried and blew off the water because of it. n.h.schmidt

[BoatDoc]

thanks for all the good advice. fluid...it definitely seems like you know what you're talking about! my intention from the start has been to make it a purpose built SAW boat. it's also a learning thing for me as it's only my 2nd electric boat. i'm sure i'll be asking more questions as i go...but i'm pretty much set on my path. schmidt...thanks for your advice too, i'll definitely check out that 3 speed. i'm open to a lot of ideas here. once i get started on building i'll keep y'all posted.

[Fluid]

Ed's controls are very good, and I've used them in some 4-cell boats. Their biggest problem is their size - they need a lot more room than an ESC does when you include the extra servo. They also benefit from air cooling, and an open hull is not the way to go fast. You could trim off the coils and make it an on-off switch, reducing the size somewhat, but when you can buy a used 4-10 cell ESC off eBay for under $60....

I always use a receiver battery - a 9v radio battery works great. It's light, small, and cheap. It also lasts for a long time on a SAW boat as long as you don't forget and leave the receiver on....

[BoatDoc]

i tried the on/off way once, and i didn't really like it. i'd like to try an rc-hydros esc. i've also been toying around with the idea of building an esc, i've found a few resources for that but i'm not sure.

[BoatDoc]

what kind of amperage should i look for when shopping for a good 4 cell esc. i've noticed that some of them are kind of pricey...like in the $200+ range. there are cheaper ones that i've seen too, but i'd like to know what kind of #'s to look for. since rc-hydros won't be making 4 cell controllers anymore, i need to look elsewhere.

[BoatDoc]

what about this one:

http://www.shopatron.com/product.phtml?product_id=NOV1785&mfg_id=135

[MattHiggins]

Check out the LRP Quantum 2. It's tiny and can run submerged in water. I run one in my N-1 mono and it works flawlessly.

[BoatDoc]

looks great...except for the price tag :eek:

[Fluid]

The amperage depends on the use - for SAW running, you'll want someting which will handle about 80 amps continuous, they'll usually handle all the peak current you throw at them if you're in the ballpark with setup. Realize that most car controllers amps are severely over-rated....some I've seen used, which were supposed to be good for 100 amps, fried at less than half that. If the specs say "any motor" then you're probaly safe.

You do not need a fancy programmable ESC for high speed boats, just one which will handle the voltage and current. Most current racing models which can run 4 cells will be good choices. Ditto used ones off eBay, but watch for damaged product!

[BoatDoc]

sounds good to me! there are a couple that i'm looking at for this project. will running a water cooling line through the heat sink make a difference? or am i wasting my time with that idea? i was thinking about drilling a hole through it and running a tube to help draw heat. i'm really looking for something that can handle a heavy workload, as i don't have lots of $$$ and a single speedo may have to pull duty in 2 or 3 boats. and back to motors for a minute...will a torgue ring help out on something that's only got 6-8 turns? friggin' electric newbies just ask waaaay too many questions :D

[Fluid]

* For SAW use, watercooling isn't usually needed. It adds weight, complexity, drag at the pickup, and because you are not running the boat for longer than 30 seconds or so at a time, heat buiildup isn't that bad. Drilling the FETs risks damaging them, I'd recommend not doing it for that reason - although the idea is a good one. If you can find one of the finned aluminum heat sinks that slip tightly over the FETs, you can drill this for a water cooling tube.

* A torque ring can help increase motor torque and efficiency in 05 motors at the expense of a little rpm. But the little thin ones sold at the LHS are not much help at all. Make one from an old 05 can - one without vents or with few vents. Heat it up with a torch to melt the glue and pull out the magnets. Cut the PTO end off the motor, leaving a ring about 1" wide. Cut this along the long axis to make a "C"-shaped ring. This will slip perfectly over an 05 motor - place the gap in the middle of one of the motor's magnets. This is like using stronger magnets, but it is almost free. On direct drive 05s in particular, this is helpful to swing more prop.

[BoatDoc]

for the heat sink i was going to drill the removable heat sink for the cooling. i like the idea for the torque ring. i'll see if i still have one of my old motors laying around and give it a shot.

[69dart]

for torq single winds are the best but i have a brushless in a proboat miss bud torq isnt a issue for me but a good low mod is the revoloution series 9 single should have more than enough grunt for a boat since it wheelies my stampede no problem and it has a 25 tooth pinion and 72 spur thats pretty hi any ways take a look at the revoloutions series motors great stuff

[69dart]

ps for an esc check www.offshoreelectrics.com

[DLM]

Boat Doc, if you drill hole thru cooling, make it brass as heat will make brass warm fast and help aid in cooling. i want you to try one of your 05 motors and 2 magnets, Hook motor up to batteries and place one magnet on the exterior of can directly onto magnet and then place the other magnet on other side. See if you can hear a rpm increase and if not turn each magnet over and you will hear the rpm increase. When you hear increase, you can retard advance and that will increase torque. I use neodyne n38 bars the size of 1" x 1/4" x 1/8", rpm goes up about 750 rpm. Then i can put a cooling coil on can and a 1" square fan which blows directly onto brushes. I see now Trinity pickup on this and a couple of other. I have done this for years.

[Fluid]

When the magnetic flux is increased on an electric motor, the rpm goes down. This is why today's motors can use such low turns; an 8 turn was unheard of ten years ago, but with modern magnets we need lower turns to keep the rpm up. This reduces the resistance of the motor and gives a net increase in power. If you get an rpm increase by placing magnets on the outside of the can, you are cancelling out part of the magnetic field of the magnets inside the can, defeating the entire purpose of having stronger magnets in the first place. :(

Retarding timing advance reduces motor power and efficiency. The amount of timing an 05 motor needs is determined by its magnets, armature windings, and load. The higher the amp draw a motor uses, the more advance it requires. Too little timing advance will burn brushes and overheat the motor - don't do it! The correct timing leaves a very slight burn mark on the trailing edge of the comm plates. Too little timing causes more burning. I've seen motors pulling high amp draws with the entire rear third of the comm plates eaten completely away because the racer refused to believe he had too little timing. You can have too much, but most racers use too little. On my 4-cell racing motors I use up to 0.4" of timing advance, the motors last a long time, and they are very fast. :cool: