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14 comments:
“Tool repair goddesses.”
How do you go about sealing rotating shafts that would go from water-proof compartment to outside of the ROV? Would out use a sealed bearing or simmer-rings and/or other??
This is a tough question! It is one we have struggled with for years. If you are looking to seal thruster motor shafts, the best thing to do is purchase motors that have already been waterproofed like bilgepump motors or trolling motors. In fresh water, and electric motor will work without being waterproofed although it will have a shorter life. Shaft seals are used on both bilge pumps and trolling motors. You might see if you can get ahold of an old bilge pump and take it apart to see how the sealing was done. Tell me what kind of motors you are using and I'll see if I can track down some better information ok?
The Tool Goddess
Tool repair goddes,
My teem and I were thinking of using 55 turn rc motors to power our rov's trusters. WWe chose these because of there low RPM and amp draw. however we would need to water proof them. In a prievious post my teem-mate asked you about using a simmer-ring to seal the output shaft.Our idea was to us two of these in a row to insure a good seal. Would this work? You recomended using bilge pump motors. How many amp do these draw under load? Would we be beter off using these rather than the 55 turn motors? We are plaan on using props off of a SesBotix BTD150 truster. Thanks for your help.
I like to use 500 gph bilge pump motors. These draw about 5 amps under load. They will draw more if they become stalled and also the initial start up. How many amps are you allowed for your bot? If you look at the places to get parts section on the main page, Cabela's has bilge pump replacement cartridges (that is what I use!) availabe for purchase at a pretty reasonable price. There is a steep learning curve in trying to seal motors. The engineers that have worked with us to develop bots in a bag kits for educational purposes have moved from home sealed motors to bilge pumps for that very reason! If you have already purchased your motors and want to try to waterproof them, be aware that the minute you put something on the shaft, you create resistance to shaft motion that can and will create major headaches. The Mabucci motors I used to use would stall if one single strand of hair got onto the shaft! Fill me in on how many amps you have to play with, and if you still have a budget for motors, or have settled on the rc motors. Good Luck!
tool repair goddess,
How much thrust do the thrusters that you show how to make produce? How many anps of current is required to make this thrust? And how long do these bilge pump motors last?
Thanks
Hi There!
It has been awhile since I did Bollard testing on my thrusters. I will test them in the next week and get that information back to you.
I seem to recall that the maximum amps they drew was 5 amps each when fully stalled. What I don't remember is exactly how much thrust each generated.
Are you familiar with Bollard testing? If not I will do an article on it. It is actually pretty easy to get a pretty good picture of how much thrust you are generating with a simple device made of PVC, a gram fish scale, and a pool to test in. If you'd like an article on it let me know!
Oh! I forgot to mention that these thrusters last a long time with really vigorous use. Camp Sea Lab, and The Bots in a Bag programs both use them and have not had to replace a thruster motor for over two years. Since the motors only cost about $12.00 each and the propeller and prop adaptors run about $6.00, the total cash oulay for thrusters components is $54.00 if you use three thrusters. You will still need to purchase tether wire, switches and project box.( a tupperware box will work!) You will also need a fuse holder,a fuse, and some banana plugs to plug your bot into the battery.
I mentioned it on the front page, but I wanted to be sure that you knew I wasn't ignoring you! I will be doing bollard testing on a motor today and will post an article on it tomorrow to tell you how much thrust is generated by a 500 gph bilge pump motor. I will re-test the amperage draw at that time so I'll have current data for you. Hope that is useful!
Well, I finally got the bollard test done. The 500 gph motors with the octura prop and prop adaptor that I list in How to Build a Motor Controller Assembly draw 3.13 amps going eiether in the forward or reverst directions and they generate .31 kg (.68 lb)of thrust in the forward direction and .27 kg (.59 lb)of thrust in reverse. When the motors are completely stalled they draw 5.2 amps. Hope this helps you! The Tool Goddess
Hi Tool Goddess,
I'm attempting to build an ROV for my final year Degree and was interested in your use of bilge pump motors. Who is the manufacturer of the pumps and what kind of depth rating do they have? Many thanks.
Sorry it took so long to get back to you!! I have been out of town in places that had only dial up so I did not spend any time on the web. The motors I use are Mayfair Bilge pump replacement cartridges (500 gph). They have been tested to 40 feet. For greater depth you would want to move to trolling motors. If you choose to go with trolling motors the control system becomes much more elaborate and will require programming skills. If you want to use the bilge pump motors but would like to pulse width modulate them instead of using simple switch box technology, there is a kit available from
Carl's Kits It is Kit # 166.
the only caveat is that you must beef up the high current path to accommodate the amperage draw from the motors.
Tool repair goddess.
I am very interested in using the Mayfair Bilge cartridges for my ROV. In your post of March 10,2007, you mentioned propeller and prop adapters and that they run about $6.00. Would you please tell me where you get these adapters?
The parts are available here:
Thruster Components
3 Mayfair bilge pump cartridges 500gph,(you want the replacement cartridges) available at Cabela's
3 prop adapters from Master Airscrew (MAS 3200) available at Tower Hobbies
3 Octura propellers from:
Octura Models Inc 7351 Hamlin Ave Skokie, IL 60076 (847) 674-7351
The part numbers you need are listed below:
1250 PL (left-hand)
1250 RPL (right-hand) Use 2 of one and 1 of the other
If you call Octura you can order the parts. The lady I spoke with was very nice, and very helpful! You must send them a check and then they will ship out the parts. It sounds cumbersome but I got my parts in under a week.
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