Help with Motor Selection 50' tunnel hull

[trddrift]

The hull is an Australian built 50'' tunnel hull by Mark Jordan i'm using 300 amp swordfish hv controller and TP5850 7Y motor (which has expired) with the new MHZ Zdrive and 2x6s zippy 45c 5000 packs. The problem i have is the drive is 1/4 inch shaft so its hard to run or find anything under 60mm with x 460 prop. On the data log was pulling 170amp (very unhappy with speed) tp state 125 amp continuous on the 5850 7y. My understanding is that this motor combined with 12s and this prop would have had a much lower amp draw. Hence the reasoning behind wanting Lehner 3080 or new 2225 something around 600 kv. Here are some pictures of my boat, any help would be much appreciated as i am starting to get fairly frustrated considering the amount of work i have put into this hull. IMAG0371.jpgIMAG0372.jpgIMAG0366.jpgIMAG0356.jpgIMAG0368.jpg

[iamandrew]

that prop does NOT look okay....

[trddrift]

It's a arrow shark prop but i never ran it with this set up.

[iamandrew]

http://www.offshoreelectrics.com/pro...od=hug-b8666sp

could re do the strut in the "motor" for the 3/16 size if you wanted to but if the hull is 50in long then you probably want to stick with a full 1/4 setup

the prop you have look like its from a rigger or something

[gerardobrandao]

Interesting that i already thought about a catamaran like yours......


Those Hulls are powered by an modified gas engine...like zenoah..or Rcmk....for good performance...
We are talking about 7 to 8 HP.....
Concerning we are talking about a 580 kV motor * 12 cells *3.7 volt (good nominal voltage per cell at high amp draw above 100amp) = 25752 Rpm..good... :-)
8hp = approx 6000watt....

6000 watt / 44.4 (12s voltage under load) = 140 amps average...... OK nothing uncommon.... :-)


2 things:

1 .....Swap that prop....its useless in there....

2 You have the power...you have the rpm...soooo..... I would go for the motor....
Although its a good price/motor quality, I think it won't pull that beast the way you want to....
If I were you, I would have bought a slightly lower kV motor in order to the rpm fall to the gas engines area....concerning props and trimming..
That MHz unit shure looks nice, but I bet it looses some power because of the mechanical losses...
What is the gear ratio from the motor to the prop!? is it 1:1, or no!?
What speeds do you expect!?


You are getting in the absolute power (danger zone) .....


Best regards


Sent from my ASUS Transformer Pad TF300T using Xparent ICS Tapatalk 2

[RandyatBBY]

I would start with the smaller 1/4 to 3/16 shaft conversion and smaller props. It is surprising how a little prop (X447 to X455) will push a large boat when the RPM are not loaded. Then go up watching the temps.

[trddrift]

Interesting that i already thought about a catamaran like yours......


Those Hulls are powered by an modified gas engine...like zenoah..or Rcmk....for good performance...
We are talking about 7 to 8 HP.....
Concerning we are talking about a 580 kV motor * 12 cells *3.7 volt (good nominal voltage per cell at high amp draw above 100amp) = 25752 Rpm..good... :-)
8hp = approx 6000watt....

6000 watt / 44.4 (12s voltage under load) = 140 amps average...... OK nothing uncommon.... :-)


2 things:

1 .....Swap that prop....its useless in there....

2 You have the power...you have the rpm...soooo..... I would go for the motor....
Although its a good price/motor quality, I think it won't pull that beast the way you want to....
If I were you, I would have bought a slightly lower kV motor in order to the rpm fall to the gas engines area....concerning props and trimming..
That MHz unit shure looks nice, but I bet it looses some power because of the mechanical losses...
What is the gear ratio from the motor to the prop!? is it 1:1, or no!?
What speeds do you expect!?


You are getting in the absolute power (danger zone) .....


Best regards


Sent from my ASUS Transformer Pad TF300T using Xparent ICS Tapatalk 2

Thanks for the input, on paper i thought my setup would have been fine but the amp draw was about 150 - 160 from the logging off the ESC in which the TP motor just got too hot with the x462 prop. I originally started with X460 prop the amp draw was around 120 but speed was quiet poor and temps after 2 1/2 min was still very high. But considering TP rate this motor to 12000w with 120amp continuous with out water cooling, so taking in mind my cooling i expected the level of performance to be much higher from this motor. The MHZ drive is a ratio 1:1 and when ran on the bench resulted in 19amp draw unloaded. So my way of thinking is to buy a motor like neu or Lehner which we all know should be up to the task. Im hoping for 80-100kph if possible. The prop in the picture was just a prop i had sitting around from a previous gas project and just put it on to see the boat with it during the building stage. It had a prop shop 1760 2 blade and now its got an x460 and an x462. Thank again for your time and any input towards the ideal motor setup would be greatly appreciated.

[trddrift]

I would start with the smaller 1/4 to 3/16 shaft conversion and smaller props. It is surprising how a little prop (X447 to X455) will push a large boat when the RPM are not loaded. Then go up watching the temps.

Was considering machining the prop shaft down to 3/16 to except smaller propeller but considering the size of the hull i was hoping to get a motor to swing props up to 70mm.

[RandyatBBY]

Save the extra work and just buy one all ready made. It takes a lathe grinder to do it right. I sell the ones Octura makes. I have three different sizes of lathes and it is just a waist of time for me to try and make one. I spend a lot of time just getting the solder joint true. But if you are good with a lathe and do not mind spending the time to build one and like the challenge go for it.

Get as big of motor possible with the correct Kv. It is more displacement and torque with your high voltage it will lower amp draw.

We did have one of the big 92 inch cat that ran on two 3080 . be very careful little things can happen that will cost you a lot.

[numse1964]

Hi trddrift

You may have seen this motor on the MHZ site.

http://www.mhz-powerboats.com/E---Motoren/Sirius-Motoren/Motor-Sirius-5698-2-5Y---1-150KV.html

The data look good for a 10 S setup. 12 S may be too much.

Best regards Henrik