can u run a small hobby motor submerged in rubbing alcohol? - Page 1
Forum section: electronics / beginners

author: Capernicus
author_rank: Frequent Contributor
timestamp: June 04, 2021, 05:01:07 am
content: I heard that rubbing alcohol is a polar solvent and it does conduct electricity, but its only a small amount.If u submerged a hobby motor in a vat of it, could you run the motor under the surface of the liquid in a bath type situation?This would help me if it could, because I could use it to help wash a complicated 3d resin print with lots of moving parts, and ifI could hook it up to a motor in the alcohol (which u use to cleanse 3d prints post print) I could help it from fusing up its mechanical pieces.So, does anyone know if it would run or not? Thanks!

author: jpanhalt
author_rank: Super Contributor
timestamp: June 04, 2021, 05:05:54 am
content: You can run them under waters. For brushed versions, that is one way to help seat the brushes.Don't know about "rubbing alcohol," but it is usually only 60% to 70% isopropyl alcohol (OPA) with water. Should also work in pure IPA.I might worry about build up to the resin from your printer. Presumably you would keep that from happening by cleaning.

author: floobydust
author_rank: Super Contributor
timestamp: June 04, 2021, 05:24:41 am
content: NO! DON'T DO THIS!My junior high buddy was being silly and ran a small motor in IPA.He lifted the motor up and it instantly caught fire, the brushes arcing ignited it. Then the IPA bath caught on fire. The flame is blue and hard to see. He got badly burned, so I say this is not a good idea. IPA is not a lubricant either.

author: Capernicus
author_rank: Frequent Contributor
timestamp: June 04, 2021, 05:30:56 am
content: Quote from: jpanhalt on June 04, 2021, 05:05:54 amThanks for the advice. The idea is its going to keep the print moving whilst it hardens the gooped on resin, its a major problem with resin printing.Quote from: floobydust on June 04, 2021, 05:24:41 amOh yeh I forgot!!! Its flammable of course... I spose you wouldnt want a spark would you, so ud have to do it extremely low voltage.Damn... I need to keep thinking. I wonder if I just ran it in distilled water, it wouldnt clean it as good, but if i just keep it running while it slowly hardens from the uv, maybe itll still work if it just keeps it moving?If theres no oxygen involved, then it wouldnt ignite under the surface of the liquid tho would it?

author: dzseki
author_rank: Frequent Contributor
timestamp: June 04, 2021, 05:45:17 am
content: Quote from: floobydust on June 04, 2021, 05:24:41 amThat is the important part! In cars the gas pump (a brushed DC motor) is submerged in the gasoline tank. If there is not enough free oxigen around then no fire will happen. Actualy arcing is not the same in fluids as in air either.

author: jpanhalt
author_rank: Super Contributor
timestamp: June 04, 2021, 06:00:51 am
content: Re: Fire.Of course, that's an issue. That's why I specifically mentioned a "brushed" motor in water. I suspected you were going to use abrushlessmotor. That's what I would do.Just FYI, hot water heating systems often have the circulating pump motor fully immersed. Those motors run off mains current.Edit: I just came back to clarify that "wet" motor statement and find that james_s beat me to it. The entire motor is not submersed. But the armature is wetted by the water to avoid the inherent problems of a rotating seal.

author: james_s
author_rank: Super Contributor
timestamp: June 04, 2021, 06:08:31 am
content: Quote from: jpanhalt on June 04, 2021, 06:00:51 amI've only taken apart one of those pumps, but it was an induction motor with the rotor inside an aluminum housing that fit inside the stator. The rotor housing was exposed to the water but the stator was sealed off and dry. An induction motor has no electrical connections to the rotor.Fuel pumps are submerged though as mentioned above, either inside the fuel tank or down under the car. Either way the fuel flows through the (brushed) motor cooling and lubricating it.

author: AndyC_772
author_rank: Super Contributor
timestamp: June 04, 2021, 06:13:04 am
content: I have actually done this once, and can confirm the motor runs just fine.The motor in question was from a vintage tape deck I was restoring, and I needed a way to effectively clean old, dried-up lubricant from inside the motor itself. The experiment was conducted outdoors, in the fire pan of my BBQ.I certainly wouldn't do this indoors, because of the fire risk. Instead, use a magnetic stirrer, and keep the motor outside the IPA container.Fire risk aside, the dissolved sticky resin will coat your motor inside and out, and after the first use it'll never run properly again.

author: Capernicus
author_rank: Frequent Contributor
timestamp: June 04, 2021, 06:39:19 am
content: Quote from: AndyC_772 on June 04, 2021, 06:13:04 amSo IPA literally puts the plastic in solution! I never knew that, the motor could be a scratchy, but its a bit of a waste indeed.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: June 04, 2021, 06:46:21 am
content: Well, yeah, you're washing/dissolving stuff, right?...Can always have a second bath with fresh IPA and give it a whizz in that. Turn it off when moving between to avoid the obvious fire hazard. I mean that's pretty duh, don't expose an arcing, fuel-soaked motor to air, right?Ya, I don't have a problem with it. Just follow basic precautions, and have something handy to smother a fire should one start (do everything in a metal bowl with lid?), to dilute fuel if it gets loose (water), or extinguish flames if all else fails (dry chemical extinguisher).Can even distill the IPA to recycle it, if you're so inclined. Kinda requires specialized hardware (some kind of still), so unless you've got something handy, meh, the alcohol isn't terribly pricey or anything.Tim

author: gcewing
author_rank: Regular Contributor
timestamp: June 04, 2021, 07:05:00 am
content: As well as the fire risk, I'd also be concerned about the alcohol dissolving the insulation in the motor. Might not be good for it long term.I suggest keeping the motor out of the liquid and driving your immersed mechanism with a shaft.And definitely use a brushless motor, to minimise the risk of igniting fumes from the alcohol.

author: Zero999
author_rank: Super Contributor
timestamp: June 04, 2021, 08:03:43 am
content: Quote from: Capernicus on June 04, 2021, 05:30:56 amThe low voltage won't protect against arcing, because small, higher voltage spikes are produced, as the commutator disconnects poles on the armature, as it spins. Yes, keeping it submersed will prevent fire, as there's no free oxygen.I'd be worried about excessive wear, since alcohol isn't a very good lubricant.

author: AndyC_772
author_rank: Super Contributor
timestamp: June 04, 2021, 08:19:01 am
content: Guys, fire safety check here. Assume itwillcatch fire, and plan accordingly.If you really have to do this, do it outside, somewhere where a fire can be safely contained.IPA that's been used for cleaning an SLA print is pretty nasty stuff. When it evaporates it'll leave behind a thin layer of resin, and that stuff stinks and causes an allergic reaction by contact - you really don't want it on your hands or anything you'll touch. It's also sticky, and becomes almost impossible to remove once it's been exposed to light and has cured.You don't have to distil the IPA to extend its life. Instead you can just leave the container in the sun for a couple of hours - the resin cures and precipitates out, leaving relatively clear IPA on top of a gelatinous mass that's somewhere between a thing from a 60's B movie and the worst failed homebrew experiment you ever tried.If you can filter this without the filter becoming completely clogged, then you can recover IPA that's OK to use to rinse a fresh print for the first time. (Warning: you may try the process once and decide to simply dispose of the used IPA and replace it with fresh next time).SLA printing is a photochemicalprocess, with firm emphasis on the 'chemical' part. After any print, I always end up spending half an hour cleaning everything thoroughly, and I end up with a plastic bag full of paper towels soaked in stinking resin, plus filters, gloves and any other disposable items that have become contaminated.Funnily enough, printer manufacturers (as well as anyone else showing SLA printers in use) never show this part of the process.

author: janoc
author_rank: Super Contributor
timestamp: June 04, 2021, 08:34:08 am
content: Why to try to submerge a motor in a vat of alcohol? Which, even if it doesn't catch fire, will reliably destroy it over time due to dissolving lubricants? (alcohol is used for de-greasing stuff ...)Why reinvent the wheel here? Laboratories deal with issues like this every day and this is a solved problem.You can either use a shaker, e.g. something similar to this:Magnetic stirrers are great if you need to deal with liquids that are e.g. corrosive (the stirring element is completely encased in glass/ceramic/plastic):Or you can always go with the classic design and use an overhead stirrer:You don't need to spin your object around, just make the alcohol swirl with one of the above designs to make sure it gets everywhere in the model and you are set. You can either get a ready-made device (new or from eBay, etc.) but most of these are fairly simple to improvise. There are also plenty of projects showing how to DIY one.

author: Ranayna
author_rank: Super Contributor
timestamp: June 04, 2021, 08:57:38 am
content: A magnetic stirrer came to my mind as well immediatly.Submerging a motor in a flammable liquid solvent can't be good, either for the motor, or for you...

author: jpanhalt
author_rank: Super Contributor
timestamp: June 04, 2021, 10:53:00 am
content: I believe the question of submersion has been answered. Moreover, a brushless motor (AC or DC) improves safety. Remember that magnetic stirrers are not completely safe either. The get warm, the vapors are heavier than air, and the risk from sparks is still present.I have not done resin 3D printing, but understand that the printed object is covered with unreacted resin from the vat in which it is made. Washing can involve many rinses to get something that is not sticky. Soxhlet developed a continuous flow method that provides fresh solvent to wash/extract solid materials.IPA is easy to work with, and the apparatus does not need to be made of glass. Have you considered scaling it up to accommodate your print. The print could be rotated in the distillation receiver so all sides are washed.Source: Wikipedia: SoxhletNB: Side tubes 6 & 7 are often omitted in the laboratory. They provide for replenishing the pot. If the material being washed is in a porous container, then that does the same purpose.

author: Capernicus
author_rank: Frequent Contributor
timestamp: June 04, 2021, 12:45:08 pm
content: The print is a lot of enclosed hinges and a normal agitated vat wont work, I wont get enough circulation internally in the model, I need to actually spin the hinges.Quote from: jpanhalt on June 04, 2021, 10:53:00 amThat looks interesting thanks.

author: janoc
author_rank: Super Contributor
timestamp: June 04, 2021, 01:00:41 pm
content: Quote from: Capernicus on June 04, 2021, 12:45:08 pmUse the overhead stirrer setup and attach your model to the rod that goes inside the vat, keeping the motor outside.

author: janoc
author_rank: Super Contributor
timestamp: June 04, 2021, 01:06:30 pm
content: Quote from: jpanhalt on June 04, 2021, 10:53:00 amYes but even brushless motors have bearings that need lubrication. I can't imagine how being submerged in a solvent can be good for that.Also, the fact that IPA is non-conductive doesn't mean it actually stays non-conductive after the uncured resin has been disolved in it (plus there is always some water content, it is not 100% alcohol). Something that may not matter that much for a brushed motor with no electronics because the resistance remains quite high but a low speed brushless motor not generating much back-EMF is either going to have a built-in driver or at least some Hall sensors which may not like the increased conductivity.Submerging a motor in this is really a terrible idea, regardless of whether it is a brushed or brushless one.

author: mindcrime
author_rank: Unknown
timestamp: June 04, 2021, 02:13:28 pm
content: Possible? Yes. A good idea? Probably not, IMO.That said, I'm biased. As a former firefighter, I tend to view everything through a "fire safety lens" first and foremost. And while youcando this withoutnecessarilystarting a fire, I'd encourage you think about "the number of things you have to do just right" versus "the number of small goof-ups or accidents that could make this go badly wrong" It's all about risk management. And I personally would probably judge the risk of fire as being excessive, when using an electrical device in/near a possible source of flammable vapors.

author: tooki
author_rank: Super Contributor
timestamp: June 04, 2021, 03:05:05 pm
content: Quote from: Capernicus on June 04, 2021, 06:39:19 amWhat exactly did youthinkhappened to solids when you dissolve or suspend them in liquid? (Like when you mop the floor, wipe down the kitchen counters, clean flux off PCBs, etc.) I don’t mean this to be snarky, I’m genuinely curious.

author: firehopper
author_rank: Frequent Contributor
timestamp: June 04, 2021, 03:34:44 pm
content: get one of these to do what you want.https://www.amazon.com/dp/B08626WF87?psc=1&ref=ppx_yo2_dt_b_product_detailsits cheap and works really well.. I have one.

author: jpanhalt
author_rank: Super Contributor
timestamp: June 04, 2021, 03:54:13 pm
content: I suspect there are also solvent recovery systems available. IPA 99% seems to be running about $15 to $20/gal in quantities less than 5 gallons.I did search on vapor-phase cleaning (one can set of a Soxhlet that way too), but I didn't find anything in the consumer market. For complex shapes and biomaterials with small pore sizes, there was some stuff, but it also may have used different resins.

author: Doctorandus_P
author_rank: Super Contributor
timestamp: June 04, 2021, 06:58:37 pm
content: Instead of submerging the whole motor, just connect two tubes to an external pump.The pump sucks up fluid from the bottom of the tank, and pumps it to the other tube. That way you have a jet of fluid that deeply penetrates into nooks and crannies. You do **not** want much pressure, as this will splash your liquid all over the place, but just a gentle flow.Systems like these are available as commercial products.One of the problems with stuff as flammable as IPA though is that if the mixture of air and IPA is "just right" (or "just faulty", depinding on how you view it) the mixture is not only flammable, but can become explosive.Just type in "dust explosion" on youtube to get an idea of how dangerous mixtures of air and flammable stuff can become.

author: ogden
author_rank: Super Contributor
timestamp: June 04, 2021, 07:17:22 pm
content: Gasoline fuelpump:

author: rdl
author_rank: Super Contributor
timestamp: June 04, 2021, 07:37:32 pm
content: Three things are needed for a fire to start: oxygen, fuel, and heat.For the application in the op, seems like a recirculating pump set up would be best.

author: wizard69
author_rank: Super Contributor
timestamp: June 04, 2021, 10:55:50 pm
content: Being involved in large scale extraction operations from UV cured monomers, I really think your best bet is a tank with a pump designed to pump alcohols. One of your bigger problems with IPA is that it disappears pretty fast, that is turns to vapor and hopefully gets blown away. So a tank with a fairly tight lid is a real good idea if you want to avoid replacing your IPA frequently.The second avenue to consider is an impeller circulator driven by an external motor. These are pretty common in laboratories, and large industrial processes, however you still have the issue of rapid IPA loss if you can not get a good seal.Now you might say building a tank for alcohol extraction will be expensive. That is only true if you don't improvise. For example 5 gallon buckets are pretty cheap, PVC plumbing is pretty cheap also, alcohol resistant plastic tubing can be a possibility, even stainless steel plumbing would be cheap in the amounts required. Buying a pump might set you back a bit but it will be far less than the cost of your 3D printer.

author: Capernicus
author_rank: Frequent Contributor
timestamp: June 05, 2021, 02:47:03 am
content: Of course!!the idea where I have a longer external axle that will turn the machine outside of the liquid should be possible to put into the design, thats a good idea.And if I use something other than an electric motor to turn the machine over is another better idea. (Like a hydraulic pump instead.)Ive done lots of theory on hydraulics as well, I just didnt think of it. Thanks alot everyone for the help.Ill probably go with the hydraulic/pneumatic pump solution, it should be pretty easy to print out a little pump that goes with it.So I should be able to do it with the motor unsubmerged anyhow, thanks for the help!

author: Nominal Animal
author_rank: Super Contributor
timestamp: June 05, 2021, 06:26:53 pm
content: I'd use a peristaltic pump with EDPM or silicone tubing. (EDPM, ethylene propylene diene monomer rubber, is used in hydraulic fluid tubing and garden hoses.)In a peristaltic pump, the tubing is compressed/deformed using a roller to make the liquid flow, and there is no direct contact between the fluid and anything else except the tubing. Lots of people have 3D printed their own (see e.g. Thingiverse), but you can also find them at eBay/Amazon/Banggood/AliExpress etc.You can also use cheap 28BYJ-48 geared stepper motors with a cheap Arduino-compatible microcontroller and ULN2003 Darlington drivers at 5V (from, say, an USB power bank) via some levers to move the direction of the pump output about, to ensure varying flow patterns within the IPA tank. Maybe even have a few different pumps, controlled via relays or MOSFETs by the microcontroller, to vary the flow patterns.

author: wizard69
author_rank: Super Contributor
timestamp: June 05, 2021, 07:39:24 pm
content: If you have a source of compressed air there are small air driven motors available that you could consider. I didn't mention them because buying new they can be costly compared to some choices. Well that and few people have a large enough compressed air source.Quote from: Capernicus on June 05, 2021, 02:47:03 amThere are lots of pump possibilities available but the Peristaltic design mentioned above can be a good choice. However some caveats. First you may need a bigger motor than first thought as compressing the hose and running a roller over it takes a bit of power all by itself. Second you may need a bigger hose than first imagined to get good flow. Third tolerances are important, you might not get the best results out of a printed pump.Now for those tolerances you will likely get better result s with a DIY pump if you avoid the need to pull a significant vacuum to lift the fluid from the tank. Even better would be to operate with a positive head on the inlet. Also for practical needs install alcohol resistant valves in such a way that the hose can be easily replaced without draining your tank, you might also suffer from leaks. In peristaltic applications the hose does wear to expect to replace it from time to time. Because hose is so critical here and there are wide tolerances on extruded hose the pump shell should be adjustable to allow optimal compression of the hose by the shell onto the rollers.The issue of hose wear is such that some commercial manufactures have come up with quick change hose segments for their pumps. Effectively a short hose with hose barbs on each end. This can save you the effort and cost of replacing dozens of feet of hose when the pump wears out the working bit. You can also use the short hose approach in conjunction with hard pipe / tubing. Pump manufactures will sometimes have purpose built hose available which may be worth considering. Not all hose is the same even if the base material is the same. You need the right mix of compressability and good wear characteristics.QuoteYep no need to submerge. For a DIY project that will have to be low cost it is far cheaper and safer to find an alternative approach. Alcohol fires are nothing to sneeze at, you will want to do all of your design work with the idea in the back of your head of what will happen if this fails. The idea of a peristaltic pump is better than immersion but you still have to consider what might happen if a hose cracks and 5 gallons of alcohol leaks all over. Leaks can be extremely bad in an enclosed area due to rapid evaporation. A circulation solution is pretty easy, doing it safely isn't and should be a huge portion of your design and build time.

author: Renate
author_rank: Super Contributor
timestamp: June 06, 2021, 12:42:23 pm
content: The gasoline fuel pump amazed me the first time I saw it.I thought that they were being pretty cavalier about safety.Still, the old fuel level senders were an 80Ω rheostat with an open sliding contact that sits in gasoline too.I understand that if you have any gas left in the tank that the atmosphere is saturated and despite having oxygen it won't ignite.I just worried about what would happen if you ran out of gas completely and maybe got some additional air in through the filler.Since the pump is working off a sucker a bit above the bottom of the tank it's almost impossible to get all the gasoline out.Apparently 100 years of experience show that tanks don't explode (often?)

author: jpanhalt
author_rank: Super Contributor
timestamp: June 06, 2021, 07:50:24 pm
content: Quote from: Renate on June 06, 2021, 12:42:23 pmDon't test it. Apparently, the vapor pressure of gasoline at 100°F is between 304 to 684 mmHg according to Google (I would have guessed lower.), which is above the upper explosive limit, assuming that tank is at atmospheric pressure. A lot of assumptions there, however. In grad school, a fellow student determined that the ignition temperature of diethyl ether is below the temperature of "burning tobacco." He tossed a lit cigarette into a trash can that had ether soaked rags in it. It did not end well.If you do test it, do it on a small scale and report back. PS: Don't try it at 60°F.

author: Zero999
author_rank: Super Contributor
timestamp: June 07, 2021, 02:44:02 am
content: I remember playing with an old fuel pump, I found in a pile of junk next to the road, when I was a child. It still had some dregs of fuel left in it and it didn't blow up, when run in air. I tried water, which made a nice water pistol, until it inevitably corroded and seized up.

author: calzap
author_rank: Frequent Contributor
timestamp: June 09, 2021, 04:47:31 pm
content: Quote from: jpanhalt on June 06, 2021, 07:50:24 pmThere must be some additional safety factor, either intrinsic or engineered. What about the case of a gas tank puncture? The liquid drains out, and the volume is replaced with air to some extent. Even if the liquid volume is not replaced with air initially, the owner or a mechanic will be removing the tank cap at some point, which will allow air in. Gasoline vapor is heavier than air. So, gas vapor should go out the hole in the bottom and be replaced with air. At some point, there will be an explosive mixture that a motor or sensor spark could ignite.Even if air doesn’t enter spontaneously. Owner or mechanic may flush the tank with air prior to installing an epoxy patch. There can’t be any liquid dripping from the hole if the patch is to have any chance of working. I tried this on a punctured tank. No one was allowed near the car while the tank was being flushed with air. And, no, I didn’t turn on the electrical power until liquid gasoline had been placed back in the tank. The much-touted, expensive patch failed in one day. I was tempted to flush the tank with carbon dioxide and weld-on a patch. But I resisted that stupid impulse and took the car to a mechanic to have the tank replaced.Mike in California

author: Renate
author_rank: Super Contributor
timestamp: June 09, 2021, 05:05:29 pm
content: I had a leak in my 50 gallon tank.I just waited until the level was below the leak and used a JB Weld fuel tank epoxy and fiberglass to patch it.That epoxy is tough stuff.Later I had to pull the tank to replace the fuel pump, but that's another story.I had a motorcycle fuel tank that split on a weld.(It was exciting when it happened.Nothing like seeing a few gallons of gas pour over a hot block.Fortunately nothing happened and I was already 30 feet away when it occured)I took the tank to be welded.At the weld shop they left it outside on a stand with a steam hose in it for an hour.

author: james_s
author_rank: Super Contributor
timestamp: June 09, 2021, 08:06:10 pm
content: Quote from: calzap on June 09, 2021, 04:47:31 pmThe pump itself has an intake screen and the inlet opening is small, that ought to act as a flame arrestor. There is no mechanism to prevent the pump from running in an empty tank though. I have never heard of a fuel tank explosion caused by the fuel pump igniting vapors in a car, I'm sure if it was happening someone would have mandated a low fuel cutoff on the pump.