Determining specs for unmarked electric motors
Determining specs for unmarked electric motors
(OP)
Hello,
This is my first post here and I registered as per my specialty which is marine biology but it seems I'm the only such member. I do however, have an electrical question if it's allowed to cross forums.
We're planning to develop and ocean going autonomous data and specimen collecting submersible robot. I'm in charge of component procurement and I hope to mitigate the high R&D costs by scavenging used components to try out prototypes first.
I've located a source for used electric motors but they are all unmarked except for the occasional voltage stamp. How can the other specs, such as amps, torque, rpm or even voltage be determined on these unmarked electric motors? Is there a machine to connect them to which tells the specs or are there shops that specialize in this? Also, I have a multimeter and a benchtop power source if this is typically done with these tools. If so, how?
Thank you.
This is my first post here and I registered as per my specialty which is marine biology but it seems I'm the only such member. I do however, have an electrical question if it's allowed to cross forums.
We're planning to develop and ocean going autonomous data and specimen collecting submersible robot. I'm in charge of component procurement and I hope to mitigate the high R&D costs by scavenging used components to try out prototypes first.
I've located a source for used electric motors but they are all unmarked except for the occasional voltage stamp. How can the other specs, such as amps, torque, rpm or even voltage be determined on these unmarked electric motors? Is there a machine to connect them to which tells the specs or are there shops that specialize in this? Also, I have a multimeter and a benchtop power source if this is typically done with these tools. If so, how?
Thank you.
Bretina
FL, USA





RE: Determining specs for unmarked electric motors
You may guess motor voltage from the equipmet you are scavenging from. The battery voltage is usually, but not always, the peak allowed motor voltage.
If you are worried about research costs, there must be a lot of better ways to reduce them then to use unspecified motors with unknown remaining hours and problematic spare parts supply.
Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.
RE: Determining specs for unmarked electric motors
And the inevitable fire or damage that makes your robot inoperable caused by not getting everything exactly correct...
The reason you can acquire those so inexpensively is precisely BECAUSE whomever has them now recognizes that the risks and costs to investigate them are higher than any potential replacement cost. Time to move on to Plan B... As Gunnar says, start with what you NEED by having a mechanical engineer determine minimum torque and speed requirements, then have an EE match those to you electrical system capabilities, then look for bargains that match those criteria. They are out there.
By the way, the reason you do not find any other Marine Biologists in an Engineering forum is likely because, at least when I was in school, biology tracks were not considered "Engineering"!
"Will work for (the memory of) salami"
RE: Determining specs for unmarked electric motors
Yes, it will be battery powered and likely DC 12v. The source for the used motors says they test them to be sure they work and if they can be easily opened, they will to check for unusual signs of wear. The savings are 80-90% and available locally.
I'm stunned this isn't a relatively easy thing to do since electric motors have been around for over 100 years already.
Bretina
FL, USA
RE: Determining specs for unmarked electric motors
Yes, but BECAUSE it is not easy to do after the fact, 99.99% of motor manufacturers permanently affix engraved or stamped metal plates on the motor stating exactly what it is and what characteristics it has. The ones that do not are those that do not want the users to be able to replace them with off-the-shelf motors, forcing them to buy from the machine OEM. Those motors then are the ones that end up in the hands of recyclers who sell them for 80-90% off!
Basic rule: you get what you pay for.
"Will work for (the memory of) salami"
RE: Determining specs for unmarked electric motors
Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.
RE: Determining specs for unmarked electric motors
I try not to limit myself and instead be open minded. I know many important inventions have come about by accident to novices and cross field curiosity and collaboration.
Thanks for your advice.
Bretina
FL, USA
RE: Determining specs for unmarked electric motors
Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.
RE: Determining specs for unmarked electric motors
To be honest, half the people here couldn't spec a motor for an application if their life depended on it. They use whatever they have seenother people use in the past. If really chicken they order it 50% bigger. Sizing a prop to a motor always ends up as an experiment.
RE: Determining specs for unmarked electric motors
Bretina
FL, USA
RE: Determining specs for unmarked electric motors
Well, I have no doubt whatsoever that Gunnar can spec out a motor, so by the process of elimination I that means you are talking about me. Looks like I'm doomed if my life ever depends on it....
"Will work for (the memory of) salami"
RE: Determining specs for unmarked electric motors
I think that we had better leave the actual specification to the specialist
Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.
RE: Determining specs for unmarked electric motors
All those are likely to be available as surplus, difficult but not impossible to find specs, and if everything works out perfectly the first time, available from OEM in higher quantities.
RE: Determining specs for unmarked electric motors
But I have to admit that I AM NOT capable of specifying a motor with these criteria, or even copying someone else.
Just a WAG but the motor that aims the camera may not be suitable for operating a grapple to retrieve a 500 lb or 1000 lb treasure.
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Determining specs for unmarked electric motors
Being autonomous these will be let loose to signaling back data about conditions where they are. If it looks interesting, we'd signal it to collect a small sample. They won't be like the big, manned "Transformer" looking ones.
Bretina
FL, USA
RE: Determining specs for unmarked electric motors
RE: Determining specs for unmarked electric motors
Bretina
FL, USA
RE: Determining specs for unmarked electric motors
Buy a Turnigy 130A power meter for about $30 shipped. It is ideal for getting the numbers Watts, amp hours, peak values etc. I've seen resellers charging up to $130 for this same device, so it it is more than $30 keep looking. You will end up making it part of the final device after testing phase.
You will want your motors reliable. I have checked a lot of motors by monitoring brush current with a scope under a light load. Consistency is not the hob goblin of small minds. If you see a periodic anomolie in the waveform there is likely a winding or commutator problem.
RE: Determining specs for unmarked electric motors
Also, since you are not requiring the motors to be watertight I am assuming that they will be located within the robot. This brings up the issue of cooling. Based on the motor efficiency, waste heat will be given off and will accumulate within the robot. At some point the temperature will rise to the point that the motors overheat. Another way to look at this is that most motors are rated for operation in a certain ambient temperature, usually 40C maximum. Operating in environments above this temperature will cause the motors to overheat.
RE: Determining specs for unmarked electric motors
Although they will be drifting at times, preparing for continuous operation will take care of both scenarios. Following you advice, we'll need to add some kind of sealed heat exchanging system to it. I don't think that will be a real challenge to do.
Bretina
FL, USA
RE: Determining specs for unmarked electric motors
E.g:
http://www.silvercrestsubmarines.co.uk/rovsinfo.ht...
Obviously it depends on your budget and how much you put a cost on time and failure.
RE: Determining specs for unmarked electric motors
Bretina
FL, USA