Homebuilt ROVs Forum

Ok, maybe its the cold meds, but I seem to have worked myself into a corner...

I have been trying to find a way to trim my budget. If I go with my current plan, I am a bit over budget just on my thrusters.

I think I will go with the following motor:
http://www.hobbyking.com/hobbyking/stor ... unner.html
Spec.
Brushless
Kv: 1050rpm/v
Operating Current: 6A ~ 20A
Peak Current: 23A

Now: It looks as if I have two choices for ESC with reverse if i stay with Hobbyking.

:arrow: Option A:
http://www.hobbyking.com/hobbyking/stor ... ramm_.html
Spec.
Cont. Current: 18A
Burst Current: 50A
Resistance: 0.001ohm
Suggested Motor: Around 12T / 2030kv
Battery: 2-3 Cell Lipo
BEC: 6V/ 1.0A Output
Motor Type: Sensorless Brushless

-or-

:arrow: Option B:
http://www.hobbyking.com/hobbyking/stor ... R_ESC.html
Spec.
Cont. Current: 35A
Burst Current: 190A
Resistance: 0.0015ohm
Suggested Motor: Around 9T / 3650kv
Battery: 2-3 Cell Lipo / 4-9 Cell Ni-XX
BEC: 6V/ 1.5A Output
Motor Type: Sensorless Brushless

There is only $8 plus change difference in the ESC, but added over 6 thrusters, and that is a good chunk of change.

I have a hunch, the correct answer is Option B. Is the extra spec worth it? I am not even confident that I have the right pairing...

And... Discuss...

I think you should go for the 35A option, because the motors will always drag more current when running a prop in the water

I'm think of using these: http://www.hobbyking.com/hobbyking/stor ... verse.html

They are a bit cheaper than your option B but only 30A

I hear you about budget!!! I thought this would be inexpensive but I am in Over $1000.00 so far and nothing in the water yet!!!

ROV Budget

7" Color TFT LCD 2 Video Monitor $33.77
9 x 4.0mm Propeller Adapters $16.96
5 x 3-Blade(40x52mm)Boat Propeller $19.49
JR XP6102 Complete Radio System $139.66
JR ON/OFF Switch + DSC Cord $15.75
6 x 750KV Brushless Motors $71.90
4 x Underwater Plugs $27.95
540TVL HD Mini Camera $57.92
2 x DC 12V Cooler Fans $1.98
DC-DC 12-35V 150W Converter $9.55
2 x RCA Plug Males $1.35
5 x RC Servo Y Extension Cables $2.56
2 x 50W LED 6500K 34VDC Lamps $31.98
2 x 67mm Glass Lens Reflectors $10.99
Silicone HeatSink Thermal Compound $0.99
Water Detector Alarm $9.70
4 x 3S 11.1v 5000mAh 50C LiPo's $115.86
2 x 3S Balancer Chargers $13.95
Red LED 3 Digit Battery Meter $2.99
Lipo Parallel Charger Board $14.88
6 x Deans Style Male Connectors $10.49
4 x RCA Male to Male Couplers $4.95
6 x Lipo Battery Alarm Indicators $16.74
Red & Black 12 AWG Silicon Wire $4.35
75 pairs 4.0mm Bullet Connectors $28.38
Secondary Water Alarm Sensor $14.18
Custom Made Hemisphere $40.50
Hardware & Materials Aft Closure $80.00
Servo Relay $22.55
Slip Ring Connector $11.86
Silicone Potting Compound $0.00
1 - 1mm Thick 12"x12" Copper Foil $7.00
1 - 3M 5200 Marine Adhesive $15.21
10 - EC5 Connector Pairs $17.59
1 - Pelican Case $40.00
More Epoxy, Sand Paper, Paint $75.00
Neutrally Bouyant Tether $150.00
__________________________________________
Total $1138.98

bikerbones1968 wrote:I hear you about budget!!! I thought this would be inexpensive but I am in Over $1000.00 so far and nothing in the water yet!!!

Oh good! Here I thought I was going a bit crazy! I'm out almost 400GBP and I havent even started on the build!

Hence the reason I had to tighten up the reigns a bit...

not cheap to build thats for sure...KR2, have you considered the run times you would get at the amp draw of the motors?? You seem to be going to pull alot of amps, Im trying to keep my main thrusters amp draw below 10 amps each. Im also considering if I can run motors at a lower current for the dive thrusters. Im going to try and do everything I can to save the battery extend my run times.
The real question is where do I need the power and where can I skimp on it?

Hey David,
I just got my props today, so I hope to build up a thruster test rig over the weekend to get an Idea of what the motor I got will do. Likely going to have to drop my AXI motors for Turnigy, but the test should be similar... I hope...

the 18a one should be fine. the 35a rating on the motor is the worst case stall current, which you should never hit. in reality, your motors will probably draw under 10a at full speed.

After a few cups of tea, and dinner, I have resumed my search for an affordable Motor + ESC combo, and believe I have a totally new option!

:arrow: Motor:
http://www.hobbyking.com/hobbyking/stor ... Motor.html
RPM: 750kv
Voltage: 7.4v ~ 11.1v
Weight: 97g
No-Load Current: 0.8A
Max Current: 14A
Max Watts: 210W
Price: $12.13

:arrow: ESC:
http://www.hobbyking.com/hobbyking/stor ... ramm_.html
Input: 2-3S LiPo
Cont Current: 18A (50A)
BEC Output: 1A / 6V
Size (mm): 31.5 x 24 x 15
Weight: 19g
Price: $16.56


If i have done my homework correctly, the max draw on the motor is still less then the listed cont load on the ESC, with room to spare.

I would then pair two thrusters to one battery pack.
Ideally this one:
http://www.hobbyking.com/hobbyking/stor ... _Pack.html
Minimum Capacity: 5800mAh
Configuration: 3S1P / 11.1v / 3Cell
Constant Discharge: 25C
Peak Discharge (10sec): 35C
Pack Weight: 482g
Pack Size: 149 x 49 x 30mm
Price: $41.79

And on top of all that, the price is MUCH better then my current test rig!
Target: 200GBP ($320.00) for propulsion.
Original Design: 312 GBP ($500.00)
This configuration: 190GBP ($297.51)

Great choices IMHO. From what I have learned the lower KV rated brushless motors are a better choice, less cavitation issues running props. Those ESC's are plenty large enough. I got the 30 Amp ones and they dont even get warm at all. The 5800 mAh Lipos are great!! I bought 3S1P 50C 5000 mAh ones off ebay. Theres a link on here somewhere.

What props did you decide on? This has all way been a sea trial thing to me, first with boats now with an rov...