Delta Force 34 hydro motor

[Peter A]

do you have proof that its common to have major failures specifically because of RPM? Maybe upload a youtube video proving this? as most motors are conservatively rated at 60k.

things that will cause failure
1. too large of a prop
2. to small of a motor
3. too small of an ESC

increase motor size, decrease prop size, increase ESC, increase cooling. blaming RPM on a failure is silly unless you're spinning flex shafts apart or something.




P.S. I've been casually racing buggies and road coarse since 1997. Thinking that because somebody is new to a mostly dead internet forum means they dont know basic physics is a low effort mentality.

Guys like Fluid have been building and racing boats a long time. He himself has set records and raced, even written a book about FE boats. He knows what he is talking about!

Myself, I have listened and learned, I try to educate others, but have to watch them burn stuff up. I've messed up and burned up motors and esc's too, I have a box full of them, some because of some dumb thing I did, some, well who knows why.

The end of it all, is that those of us with a bit of experience, try to give the best advice we can when someone asks the questions, so they can enjoy this hobby and have the most fun running their boats.

[Bande1]

Guys like Fluid have been building and racing boats a long time. He himself has set records and raced, even written a book about FE boats. He knows what he is talking about!

Myself, I have listened and learned, I try to educate others, but have to watch them burn stuff up. I've messed up and burned up motors and esc's too, I have a box full of them, some because of some dumb thing I did, some, well who knows why.

The end of it all, is that those of us with a bit of experience, try to give the best advice we can when someone asks the questions, so they can enjoy this hobby and have the most fun running their boats.

excellent. post up some proof with all them years of experience.

Ironically this member just posted his 133mph run with 1700kv on 8s. 48k RPM
https://forums.offshoreelectrics.com...amaran-133-mph!!

[Fluid]

excellent. post up some proof with all them years of experience.

Sure, typical clueless newbie response. Yet another for the IGNORE list, congrats!




.

[Bande1]

Sure, typical clueless newbie response. Yet another for the IGNORE list, congrats!




.[/COLOR]

that's a weird response. Asking for evidence makes you want to ignore someone? No comment on the mans 133mph run?

[Peter A]

Bande1, instead of running off at experienced and well respected model boaters, how about you go and drop $3-5k on a boat to to do 130+ mph. Try building and setting one up. Then you might learn why advice is given the way it is.
Not everyone is after world record speeds, and just because you think 50k rpm is the way to go, just makes it your relatively inexperienced opinion, in fact you seem quite fixated on it. From what I've seen you own experience seems to be largely rtr boats that you slap a higher kv motor in.

Have you ever been in a model boat club? Or joined a national organisation? Raced or been around other model boaters?

As Jay has pointed out, you tube videos generally only show the successes, not all the fails.

[Panchothedog]

Bande 1 Nobody is doubting the validity of the video you are posting. What they and myself included are telling the O P, Tim Cross is that running a boat in this manner is very risky and usually leads to expensive lessons.
Dealing for myself, I am 75 years old, I have been running fast electric boats since 1987, I have built or purchased more than 45 electric boats during that time.When I first got into the hobby, long before the internet,
U-tube, brushless motors, or Lipo batteries I was reading magazine articles and learning from you guessed it Jay Turner. Fluid. I'm my VERY EXPERIENCED and educated opinion there is NOBODY on planet earth that is as knowledgeable about high speed model boating than Jay Turner. You are doing nothing but showing how pig headed and ignorant you are by continually arguing about someone who went real fast and put it on a video.During your first couple of post you rant on and on about mono's not being able to run large props and chine walking. I wonder if you even knew that the guy is building a hydroplane. Your remarks had nothing to do with the boat that was being discussed. Quit before you make even more of a fool of yourself.

[Bande1]

Bande 1 Nobody is doubting the validity of the video you are posting. What they and myself included are telling the O P, Tim Cross is that running a boat in this manner is very risky and usually leads to expensive lessons.
Dealing for myself, I am 75 years old, I have been running fast electric boats since 1987, I have built or purchased more than 45 electric boats during that time.When I first got into the hobby, long before the internet,
U-tube, brushless motors, or Lipo batteries I was reading magazine articles and learning from you guessed it Jay Turner. Fluid. I'm my VERY EXPERIENCED and educated opinion there is NOBODY on planet earth that is as knowledgeable about high speed model boating than Jay Turner. You are doing nothing but showing how pig headed and ignorant you are by continually arguing about someone who went real fast and put it on a video.During your first couple of post you rant on and on about mono's not being able to run large props and chine walking. I wonder if you even knew that the guy is building a hydroplane. Your remarks had nothing to do with the boat that was being discussed. Quit before you make even more of a fool of yourself.

Then it should be really easy to post up plenty of videos of boats failing. I dont understand what the problem is? I got 25 videos ready to go showing 45k+ RPM boats not having problems.

instead of going by "he is experienced and well respected" just post science and evidence.

[Bande1]

uh oh another member here posts up running 45k RPM with a 2000kv on 6s

https://forums.offshoreelectrics.com...801#post767801

[paulejr]

Well, being new here and new to FE, seems like y'all got more mojo picking each other apart with some ego instead of sharing you experiences with those like me wanting to have a bit of fun in (my) later years.
That being said, my rehab of a 40 year old, xnitro 36 Dumas Hydro AVL is about done and here is the list of the guts of the thing.
Leopard 4092 1480 kv, TZW 160 ESE on 6s ( 2 x 3s) G2 Smart 5000 , 11.2v , 100c, choice of props ? not sure and would take a recommendation seriously. boat weighs in at 7.6 lbs . No, it ,may never race but just getting it up to modern speed limits on the lake is enuf for this 74 year old hull... as ever , God bless and Happy Trails!!!

[Panchothedog]

Nice choice of motor for your Dumas hydro. Plenty of Guts for that size of hull. Is it the shovel nose hull. I think it was called the Miss Unlimited. Most of my experience is with the Octura brand props. Shooting from the hip, I would think an x445 would be a good starting point. 3 blade props can be a little more forgiving in the handling compared to a 2 blade, but take substantially more power to turn in the same diameter. A x442 three blade might be a little small for the size and weight you will be pushing. The CNC
Aluminum props sold here on OSE offer a bigger selection of 3 blades in the
43 to 46 mm range. Do you own a temperature gun? A very important piece of equipment, especially for your situation. You are kinda out there on your own with not a lot of reference points to draw from. Is your boat running the stock submerged driveline? That will be more taxing on the entire power
system. When you first start running, go for 60 to 80 seconds of good hard running, bring it in and check temperature of motor, ESC, and batteries. Try to keep everything under 120 F, at the end of a FULL run. Do you have a voltage checker? Are you aware that Lipo batteries should not be run down below a certain level. Sorry if I am getting over simplistic. Don't know how much you know. How fast are you looking for. A end over and flip at 40 mph
can be very hard on a old wooden hull. Especially with the added weight of the batteries. They land harder. Work up to modern speeds gradually.

[paulejr]

Panchothedog,
Thanks for the response, having flown Typhons for the last 5 years , am very familiar with LiPo's quirky requirements . I'm guessing the prop at the 43-46 mm range and 1.5-1.9 pitches would be a starting place ,I have to get in some glass filled for testing before laying out another 60$ for one of Dasboata's hot props, of which I have (1516)on my mono and it runs right at the national speed limit! Another Octura 440 used on the same hull and will try on my UL-19, too small for the U-1 Atlas Van Lines pickle fork but will use it as starting point. I have been researching telemetry radios and can't seem to pin one down although I do like Futaba and have run them since the 70's when I raced with factory rep out of Compton CA. So now I am mostly up to speed, thanks to the good info on this forum and your taking time to go over things . As always , God bless and Happy Trails!

[Bande1]

watts = volts x amps

lets say you have a 2000w motor

when you run lower voltage you in turn demand higher amperage to achieve 2000 watts. That is what is burning up speed controllers. You keep insisting to run lower voltages than the motors rating (most ~2000kv motors are 22v-30v for a good reason) so when you run these low voltage setups you then demand more from your wiring and ESC. 6s doesnt need 5mm connectors so much as 3s and 4s do. Go feel your wiring after a run at low voltage. its hot. It may even be melting solder joints. because you are stressing the ESC and wiring by drawing too many amps at too low of a voltage. the higher your motors voltage and the lower voltage packs you run the worse it will be.

a 2000w motor at 15v will draw 133A. that same motor at 23v will draw 86a. guess what happens to your 90a esc and xt60 connectors at 130a? you're not being "safe" by recommending these too low of voltages for an arbitrary RPM limit.

will a motor run hotter at peak voltages? yes. but thats why you have a cooling jacket on the motor and not on the wires. If you want to spin slower or run cooler then lower your end points, lower your motor timing, or run a smaller prop. -5% end point will drop temps dramatically.

[paulejr]

So, if one is running two 3s 11.2 v in series , the esc is seeing 22.4 v at 6s. the esc at 160amp. Now that means the watts are at about 3500? With the motor rated at 2600 watts ( burst at 4200), ( Leo 4092 ) that means one need a 36 v supply to keep from burning up the esc ? For a 1480 kv ,3.5D. Looks like one would need a 200 amp esc. Producing about 33,152 rpms. a bit low for racing and a bit high for comfortable sport running. solution? melty melty ?

[Bande1]

the esc doesnt produce a constant amperage. 160a is its max capacity. amperage is based on load while voltage is constant. IF you put a huge prop on the boat it could max out and overheat the motor.

if you have an appropriate prop for the boat-motor combo and you change to 4s, your amperage will go up and you will see hotter wires. if you prop up on 4s to match your speed on 6s you going to get wires REALLY hot. desolder hot.

you can limit the amperage available in the esc in your controller by turning the throttle end point down. ensuring everything stays cool.

[vvviivvv]

I hope nobody takes this thread as sound advice.... and yes i do have some boats that spin very high rpm at very high power levels


Quote from a old thread...

To understand why low speed throttle is bad, you need to know a little about how ESCs work.

In general, with a constant load a motor's RPM changes as a result of the average voltage it sees. Since a battery is a (relatively) fixed voltage, we need some way to vary voltage seen by the motor. A microcontroller is a digital device - it can generate only "on" and "off" conditions. How does one take a fixed input (battery) and an on/off control and make an analog (variable) output?

The answer is by going on and off very quickly, varying the relative amount of on and off pulses. The longer you are "on" and the shorter "off", the more average voltage the motor sees. This is called "Pulse Width Modulation" or PWM. The on-time is called "duty cycle" and is repeated at a certain rate (times per second) called "frequency." The duty cycle is controlled by the transmitter, the frequency is controlled by the speed control.

In a brushed control, this goes directly into the two motor leads, with the coils and mass of the motor acting to average out the pulses into a more-or-less linear value.

In a brushless control, the same thing is going on, with an added twist. Not only are the pulses varying the voltage, but the voltage must be moved between the 3 different wires in order to simulate the plates of the commutator (comm) on the armature.

Now, why is low speed bad? The on/off switching is done with a device called a FET. A FET is a low-resistance switch when fully turned on. When it's not fully turned on, it has a resistance which varies depending on exactly how turned-on it is. This is called the "linear mode." When in linear mode, a FET is like a big resistor - you know, those things inside your slot car handle that get HOT, or like the ceramic thing in your old mechanical speed control. The problem is, FETs don't like to be in linear mode - as they warm up, they get more and more resistive. But the motor at low RPM is less and less resistive, meaning it will draw more current.

What you have is a situation that can quickly degenerate into what we call "Thermal Runaway" - the heating of something causes it to heat itself even more.

So why don't ESC designers not run FETs in linear mode? Well, we try real hard not to, but it's a matter of physics - you can't completely eliminate it. If we make the linear mode time very short, it adds bigger capacitors to the board to provide the necessary energy, and people complain about size. They also complain about glitching their radios, as the speed at which the FETs are switched then generates radio frequencies. If we spend more time in linear mode, we can eliminate the glitching in the radio - but then we run into potential heat problems. Engineering always is a balance of competing problems and solutions.

What happens at low throttle is that the FET goes into the linear mode for a larger percentage of the on-time. That means the FET spends more time heating than it should - and hot FETs have more resistance, meaning next time they are in linear mode, they will heat up even hotter. At the same time, the motor is at lower RPM and therefore pulling more amps (a stalled motor will draw the maximum current).

You can get a lower RPM (ie, a lower average voltage) at maximum duty cycle only by lowering the input voltage. The speed control will run better with a lower input voltage even though it may be passing more amps simply because there will be less time for the FETs to be in linear mode. It is not an exaggeration to say that the FET may have 10X or more resistance when in linear mode. Heat generated is directly related to resistance.