Does a fast gearbox generate more electricity?

[@IZuzivowoI]

As others have pointed out, you need to measure voltage and current at the same time. Also, when measuring current, your multimeter is set to mA, but your leads are connected to the unfused 10A sockets. This will give unreliable results.

[@Dr_Mario2007]

Yep, the more amperage drawn, the most the voltage will drop. And the more connection the more resistance would be present is true also, thus unreliable results.

[@alanguimaraes3383]

Yeap. But we need to recognize that the results are pretty accurate. You are absolutely right about the error, but it's just not that negligible when we're up to huge machines.

[@eliasbinde2629]

Yeah you need to plot resistance against voltage to actually get any sort of idea as to what power it produces

[@haaziqhehe5024]

0:17 its funny when the big one spawns

[@fabioaugustozuluagagiraldo9050]

BUENAS TARDES DONDE PUEDO CONSEGUIRLO COMPLETO COMO ESTA EN EL VIDEO

[@xTHERANGAx]

This man sure does love his 3D-printed gearboxes

[@mr.engineear0987]

He should make metal ones and put them to torque test

[@mr.engineear0987]

@GlueEater87 people who don’t

[@mr.engineear0987]

@GlueEater87 neither here lol

[@bunkerofclarence]

yeah, just start up a company and partner up with another company who makes valves

[@slurper5300]

More gear boxes

[@DC-ox4rc]

You need to measure current and voltage at the same time, NOT measure unloaded voltage and then multiply by the short circuit current.

[@FT91-z5j]

That’s the chines way for any Produkt they advertise 😂 But you right he needs an powermeter or he should measure the voltage over nen given resistance.

[@Comfy_Bed]

would it give massively different results?

[@evaldas2490]

@@Comfy_Bed Well in the video he also mentioned that he couldn't spin the motor as fast as he could when he connected the leads. So it would be best if he connected some wire with known resistance or use a low value resistor and measure the voltage drop through the resistor then use P=V^2/R formula.

[@dancoulson6579]

I agree. You need to consider that when the supply is loaded, the voltage drops. You need to calculate the dropped voltage by the amps being drawn to figure out the real wattage. Most generators have a 'sweet spot' where they're most efficient too. ie, if you over-load the generator and pull too much current, the voltage will drop significantly. Since the power is voltage * amps, it actually reduces the power delivering capacity. So let's say you could pull up to 2A before the voltage drop starts to happen. If we're generating 10V and pulling 500mA, we have 10V * 0.5A = 5W of power. But we could draw 1.9A and get 1.9A * 10V = 19W of power. Now we'll draw 3A which drops the voltage down to about 2.5V... 2.5V * 3A = 7.5W of power. Most modern phone battery charging circuits take advantage of this to charge the battery as quickly as possible with any power supply - They'll ramp up the current until they detect voltage drop. At which point they'll knock back the current draw by a fraction. This gives the hightest current available for the 5V supply over USB.

[@badrobot8195]

The test also need to be done on same motors to prove the variable "speed" has any effect

[@TheObserver567]

You need a flywheel on the fast gear set to maintain speed and store energy momentum. For the big generator just get a slight faster speed and wala!

[@gavinwilson5324]

r/BoneAppleTea

[@juango500]

voilá!

[@ginnungagap9793]

Getting the gearboxes to spin faster: mounting them with bolts/screws would be a great idea so you didn't have to hold them down for the spinning. This may look like a heavier-duty more industrial stand than what you've been printing, but that way, you could both get a faster and more consistent turn of the crank. And, speaking of the crank, if you increased the distance between the crank shaft and crank handle, you'll have significantly increased leverage, and thus an easier time to spin quickly and consistently. Seeing a metal gearbox would be fascinating. It would be a great way to compare the friction outputs of similar gearboxes with different materials; not to mention spin speed and electrical output differences.

[@BenjaminMarshallScienceMan]

Great video! But unfortunately as others have pointed out, you didn't measure power correctly. It doesn't look like anyone has explained how you should really do it, so try this: You should buy a power resistor. A 100 Ω resistor rated for 25 W would work fine and only costs like $5. BTW power resistors can also greatly exceed their power ratings for short periods of time, so it's fine if you produce over 25 W. Once you have it, connect it to the output leads of the generator, and hook up your multimeter to measure the voltage across it, and do some simple math. If you have a 100 Ω resistor and see 12 V across it, then you know your current because 12 V ÷ 100 Ω = 0.12 A. You'll also know how much power you're generating because 12 V × 0.12 A = 1.44 W. Good luck to you! PS. I don't know if you'd be interested, but I have a bunch of experience in 3D printing entire electric motors and have dabbled into 3D printing magnetic gearboxes. It might be cool to collaborate on something.

[@divinedragon17]

thanks for the info bro

[@N0Xa880iUL]

Yep. Knew measuring voltage and current separately was not the correct idea. My question is, would it be correct to measure power by using two multimeters at the same time? One for current and one for voltage?

[@1992jamo]

Nice work on the gears, looks like you've stepped things up a lot in how you've designed/put these gears together. Question though: You're measuring the voltage without load, and the current is being measured with the meter acting as a dead short.

[@IZuzivowoI]

He is using permanent magnet DC motors as generators, therefore the output will be DC. But yeah, voltage and current must be measured at the same time.

[@1992jamo]

@@IZuzivowoI Cheers, I've updated comment. Not sure what I was thinking

[@DiacnikYT]

You didn't ask a question

[@1992jamo]

@@DiacnikYT It's implied, i'm questioning their methods because measuring voltage without load, and measuring current as a dead short is meaningless.

[@zachlistofficial]

That makes sense from a mechanical perspective as well. If you're riding a road bike, you can pedal the smaller gear ratio a lot faster to pick up speed and get going, and the big gear ratio, while requiring much more force, outputs a lot more power.

[@Lunarcreeper]

3:27 if you are wondering why he doesn't just hold its handle. it's because for some reason when it's connected to something it's meant to power it becomes extremely difficult to move and feels almost impossible to get a good grip on

[@_vizec]

The “some reason” is Lenz’s law

[@danek_hren]

​​@@_vizec almost. The reason is the DMM uses a shunt resistor, and the current goes through it, so it's essentially short-circuits the generator, thus it draws all available power. This creates opposing magnetic fields making it difficult to spin.

[@LifeontheBellCurve]

As someone who rebuilds industrial DC generators for steel mill conditions, I can tell you that most of the MG sets run at 1200-1800 rpm but I have seen some slower. They have a synchronous motor (an AC stator with a DC rotating field element that maintains a consistent speed without slippage) coupled to several (separately excited or series excited) DC generators on both ends of the motor. There is a direct mathematical relation of work done in HP to the output voltage and supplied possible amperage output. Horsepower = Torque x RPM / 5,252 and 1 HP = 745.7 Watts. Knowing this, you can deduce that the rpm can vary but what really leads to a higher output is the torque in the system. You can build a DC generator to maintain a certain EMF at variable rpm by adjusting of your excitation field in response (the bread and butter of series excited generators) but the actual amp(flow) output under load leans more on the torque of your driving force. AC generators are a completely different beast and are more dependent on RPM over torque with the speed being the deciding factor in the output frequency. Most run at 3600+ rpm with 3600 being more common in the United States in order to make that 60Hz frequency.

[@jespermller6956]

A fun little test. and thanks for that, I really like your videos. But it just does not quite work out in reality. You will need to measure the energy you are getting into the system at the same time to get an idea of the output. And you can not measure voltage and amp separately, it must be done simultaneously with 2 multimeters. In the test you use 2 different generators, it will certainly also give different results. Suggestion: how about setting a motor to drive the input shaft, use the same generator at different gears, measure amp and voltage simultaneously.

[@irfankhan2378]

You need to do comparisons on a standard load not just the open load voltages or currents. Although its ok for simple scenarios. You can also start with the law of conservation of energy or just the fact that if gear ratios increase or decrease speed, they do the inverse for torque.

[@Skyfighter64]

On that high speed gearbox, you need a bushing on the crank handle hole. This will spread out the forces, prevent enlarging of the hole itself, and make for a more secure crank handle. A bushing and bearing would work even better, but as we see in the video, even trying to use that crank for only a short bit wallowed out the hole it was in.

[@frozby5973]

Also a larger crank could help with ease of use

[@aliozanerbektas]

No. It's about how much power you input into the gear, minus the friction loss, times the efficiency of the generator.

[@itsglizda345]

2:05 You are using your multimeter in 2mA range, so you arent getting 200mA from that motor, you are getting less than 1mA (0.234mA), and 2:43 you set it into 20mA range, so from that bigger motor you are getting 2-3mA - barerly to light up an LED, you can connect LED and see how much power you are really generating. For generating power purposes you should always use brushless DC motors, because they use permament magnets

[@UsmanKhan-jh4eo]

I don't know what u r talking about but I definitely got an impression that the KZbin guy has really messed it up.

[@sapientboxcreature8415]

You should try covering the gears with magnets and surround it with a lot of copper wire to make your own generator

[@onwardromansoldier1]

As an engineer, im triggered... Nothing about this makes a shred of sense.

[@electronresonator8882]

may I know why you still avoid planetary gears for this gear up ratio ?

[@3DPrinterAcademy]

I was actually thinking about making a planetary gear video soon!

[@RobertSmith-me3gs]

@@3DPrinterAcademy please do.

[@nelly4590]

@@3DPrinterAcademy if you need a hand I can provide the STLS for a planetary… we can work on the ratios together

[@claytonsmoking]

@@3DPrinterAcademy what generator was the larger one?

[@nightmareinaction629]

3:58 love this he already knew all his views have common electrical sense

[@karyjas1]

generators have a perfect speed at which they have the highest productivity, but the input energy also matters - the harder you crank the handle the more power you put in, but lots of gears invite a lot of friction, which is power lost. Makes sense a bigger generator will be more productive. When you hooked up to measure current, the multimeter became a load, and that resistance of the generator was the effectiveness of converting input energy to current. The small one didnt give much resistance, which means its not an effective generator.

[@peterknoppers424]

Multiplying Voltage with nothing else connected by short-circuit current does not yield achievable output power. You will have to attach a decent load resistor and measure Voltage AND power under that load. What constitutes a decent load depends on the specifics of the generator. If you don't have those specifics, measure it's resistance while it is stationary and use that value for the load resistor.

[@genepozniak]

I was looking at this as a means to make a gravity "battery" more efficient, as in needing the weight to fall more slowly, thus decreasing the distance it has to fall. Over a certain weight, the torque would be irrelevant, for all practical purposes. A flywheel might help even further, though it might not be necessary.

[@vincentrobinette1507]

Better bearings would greatly narrow the margin between high speed low torque, Vs. Low speed, high torque. The gears themselves, look really good. If they spun on precision ball bearings, that would reduce the losses of going through that many stages. I would start with a good crank bearing, since that's the one that takes the most severe radial load. making the axle longer, to put space between the bearings, will make them more stable against the cantilever loading caused by turning the crank by hand.

[@alexanderthef8]

Saving this for the power comparisons, but would still like to see the gear stack work on the large motor

[@estaticethan1752]

Do it! Do a metal version of this!

[@Engineezy]

Great description! Finally someone addressed the power vs speed principle

[@loganyoung2964]

Somthing that would probably help you is getting a solid surface you can turn better plus use triangles to help with the turnes and make the gears closer together

[@goldenturtle3261]

i have been wondering this for ages thank you so much im gonna subscribe since you did this.

[@mrpotat680]

In theory, yes; theres a major increase of torque required and on top of that quite a bit of energy is lost to friction and entropy.

[@mrpotat680]

he says that in the video later on I see

[@E-GaN]

Well, you need to connect a voltmeter and a currentmeter together since the open circuit voltage and the loaded voltages are diffetent. And also when the probe is in the 10A range, switch the meter to 10A range.

[@gavinlynas2833]

I'd be interested to see you use a higher gear ratio for more spins, attach the bigger motor, extend the handle way out at about 75°, then add a heavy weight at the end. The handle will only turn roughly a quarter but the spins a power generated should be high.

[@stgigamovement]

Please do the metal one

[@genepozniak]

2:50 "When you're measuring current [amps], there's a lot of resistance in the motor." I've been using a multimeter my whole long life, but I don't remember ever reading this in the instructions. In fact, Googling text instructions about this produced nothing. It was only when I looked for video instructions on how to measure generator current that anyone mentioned this. Learn something new every day! 🤔

[@SimchaWaldman]

Nice work!

[@jonathanbrock3462]

Make the gears from metal!! That would be great to see

[@iluha168]

I love how the video ends at 4:20

[@alexanderreiner7694]

Anyone who knows a bit about friction knows the answer up front. Still a nice Video

[@danielroy8232]

seems like, for this to be a fair comparison, you'd have to use the same alternator for both setups. different sized alternators will have different efficiencies.

[@sorrynoescape2417]

Soooo which one can charge my phone?

[@Mujhe_Credit_nahin_chahiye]

Insert it directly to the 11KV Transformer 😊😊😊

[@saberblue33]

4:20 He clearly is a cultured man.

[@bobaduby]

As a control I think he should be using the same generators for both gear ratios. Metal and nice bearings will help so he can crank of them as hard as he wants

[@jackasshomey]

the speed to power generation potential of your gearbox will directly correlate to what kind of induction motor your using, if your using a high RPM low torque motor then high speed will work better but if your using a low RPM high torque motor the opposite will apply, that's why they use high torque for water turbines and low torque for wind turbines

[@greggory7655]

What if you designed a small custom motor that is specifically designed for the small and fast gear setup? You did mention the coils and magnets play a big role in current generation so perhaps making an hybrid motor will improve the output?

[@matejmotuz108]

Motors and generators with higher frequenci are generaly smaller than wlow frechency machines with the same power output , so less cost on materials

[@superbpancakes4092]

I see the handle is very loose on the fast gearbox, making it metal would be a good decision, if you oiled it.

[@MarcStollmeyer]

You can just buy metal gears from SDP/SI and it would be a lot cheaper than 3D printing them.

[@3DPrinterAcademy]

I don't see that have compound gears unfortunately

[@MarcStollmeyer]

@@3DPrinterAcademy do you have access to a lathe? Drill out a pinion big enough for bearings to go inside, drill out a spur with an interference fit with the hub of the pinion, press fit (or thermal press fit) them together.

[@faithgaming7495]

I would like to see a full metal version of the gearbox

[@vikrambamniya2801]

One flywheel added on motor rotor and make last spike wheel gear with one direction free rotation mechanism will provide greater afficiency

[@smortboi1320]

Damn, the devs knew what we would try to do. We will find infinite power!

[@jimbobkentucky]

Thanks for this!

[@jasmijnariel]

2:22 when you dont use the handle, and create a false reading

[@ПростойЧеловек-к8г]

So amazing video and explaining

[@ongoingrhyme57]

Try increasing the length of the lever for more of that sweet, sweet, leverage.

[@jlh2119]

What would happen if you were able to drop a weight from a height as input to drive the crank? Already out of my wheelhouse ...would adding a capacitor after generator help to reduce the start force needed?

[@fredcarson2791]

Any generator will provide more electricity if driven at a higher speed but there will be an optimal speed above which the output will begin to fall as mechanical and electrical losses increase. The losses will appear as heat.

[@RobertSmith-me3gs]

I imagine that you could run quite a few small generators on that setup though. I'm curious how many you could fit and what those numbers would look like.

[@XInfinity2024]

Maybe if he extended the small gear on the last one he could move the large gear out further and put a bunch around the big gear

[@rajanwilliams3844]

Do you carry out live streams?

[@WIZ56575]

Let me start by saying your video was well done, there's only one little problem with it and it can be solved with going through history. Keep in mind I realized that you were doing a basic demonstration but these demonstrations were also done when I was in high school , studying automotives and gear ratio If you know where I'm going with this then you should realize that these problems have been solved. But people in today's society seems to be talking about them much less then we were in the past. Small suggestions to anyone who reads this go back and read old Popular Mechanics not to say that they didn't have the technology we have today but they solve a lot of problems that are not even being mentioned in today's time. I told a friend this a couple of days ago and he called me back and he solved the problem with this suggestion , if you take 2 different devices that you think have nothing to do with each other but 1 solves 1 problem and the other solves another problem why not find out How to combine them into one. This is called unity. Now if you haven't guessed it I am the person who created and develop over unity , my name is Lloyd G stovel And you'll hear me talk about these things quite often on my channel. I just recently started talking about how to overcome many of these things that seem to be misinterpret or just outright says impossible on my channel why because one Most of these things have already been done so I don't understand the big secret but it seems to be one anyway. I'm not going to lecture you here if anybody wants to know more this take a little look at the channel and overti'll explain as much as I can from a person who comes from your past. Let's see if that helps or ignored!

[@freshwatermenace7422]

Hook the tiny fast generator to a drill that powers the gear box and see if it can sustain itself 🤙🏻

[@ajithbhaskaran672]

It's simple the RPM must be above the motoring speed such that it goes into generating mode.😎

[@matejmotuz108]

Only when motor recuperates , when you turn motor/generator it generates some energy , usualy there is rpm range at which power generation is efficient , but it doesn't necesseraly mean motor have to rotate at higher speed to generate energy . If motor is conected to voltage source it runs (unexpected) and if you stop electric current , motor will slow down and eventualy stop , but while doing so , generates energy , but voltage (voltage does not mean power/energy , but both are lower in this case ) and power are lower so than , for example , power = current * voltage , so if you have 300Watts of power , it can be 100 volts (voltage) and 3 amphers(current) or 10 volts and 30 amphers , now energy flows from higher voltage circuit to lower voltage circuit , and sience it doesen't make sence to focibly spin slowing down motor , we can convert power to higher voltage than send it into source (electric converter handles that) But motor without power source will always have higher voltage than 0 , so it wil be a source of power , but if you connect it to some source of power , current will flow from higher voltage to lower , but you ussualy won't get much power from spinning motor/generator on low rpm

[@UncleKennysPlace]

Power output, in wattage, versus power input, will give you the efficiency. Nothing else matters. And that wasn't measured in any meaningful way. I have a generator that will put out 50 kilovolts.

[@3DPrinterAcademy]

The results show that the gearbox with more gears is considerably less efficient

[@NirateGoel]

@@3DPrinterAcademy It doesn't, you didn't measure input power therefore efficiency calculation is impossible. Ignoring the obvious issue with your output power measurements.

[@venos_gg]

Yes, please make the solid version.

[@pakopaku]

May i suggest adding small heavy flywheel to start the first momentum and help for the next momentum

[@acki4168]

there's a problem in your calculating . When you measure the voltege across the motor , the internal impedence's motor is zero. Because it's like an open circuit (the impedence of a multimeter has to be very high, in this way the current flow is almost zero). So you can get an accurate voltage's value. But when you connect the motor to the tester, for measure the current, in this case the impedance of a tester is almost zero, so the motor sees two impedances, that of tester and internal motor. You have so a drop voltage that you're not considering.

[@NoahKuzel]

The short answer is yes, unless it has a voltage regulator on it. Because otherwise a alternator would create more voltage as rpms increase, but it doesn't create more than 14.?? Volts at any given time.

[@nakoda1610]

i instantly know the big one should be better if you have the same watts of input bcs of the resistance on the gears

[@3DPrinterAcademy]

Yep. More 3d printed gears means more friction and less efficiency.

[@livinginavandownbytheriver2349]

Great gear builds. Too many variables at once tho. You change one variable at a time while doing the scientific method for accurate results.

[@MegaShock11]

You should make a self cranking gear box for you to bypass cranking it yourself

[@hironshy5337]

3:45 , you forgot to speak about the Energy efficiency of the motors ^^ It make a significative difference. Biggest generators have better efficiency. The type of motor winding and there characteristics are also a part of the equation. . . But i understand that you want to keep it more simple

[@Joege]

Das pretty sick man.

[@lokerosenlund5637]

He can try using the power outcome of the gearbox to spin the gearbox.

[@mcgavin098]

Apply a significant load and there will be great difficulty keeping up higher RPMs.

[@pavanra7453]

Use ball bearings from rod to gear, for smoothening the spin

[@christopherleggett1623]

Add a flywheel to your design so you can produce the torque you need to push the big generator

[@Domo6768]

Please put up where you got the big generator

[@Wesley_H]

Sooo…. Hook the big generator to the high ratio gears maybe?

[@3DPrinterAcademy]

The high gear ratio gearbox doesn't have enough torque to spin the big generator

[@Wesley_H]

@@3DPrinterAcademy You can do anything with a long enough lever.

[@bananamaniac2]

You should try this with planetary gear sets

[@ricardoescuderorodriguez1912]

Its interesting, in general we could describe de open load voltage of a CC machine in terms of speed and exciting magnetic flux, for permanent magnets we could say that the magnetix flux is going to be constant, so your open load voltage is going to be speed dependent only. Besides that the amount of mechanical power you inject in a system is equal to torque times rotational speed en rad/s. You have to consider that the amount of mechanical power wasn't exactly the same for both cases. Whatever it was a nice experiment though :) .

[@oliverherss]

Hi, sorry to be THAT guy, but to messure watts, you need to measure volts and amps at the same time. Because, when you load a power source, the voltage usually drops from an open circuit.

[@AstralGnome-64]

Does this wear down the 3d printed parts? And is this gearbox available to 3d print?

[@NelsonKosgei]

Try making the crank longer, thus you get more torque

[@tygonmaster]

This confirms that size does indeed matter

[@hbzandbergen]

The power stays the same, when you ignore friction loss

[@burnologist229]

If you are up to the task you can DIY a foundry and cast aluminum gears with sand

[@andrewcomtois6542]

If you make a model out of metal try to get the tolerances as tight as possible

[@AverageReviewsYT]

So what’s best for charging amps or volts?

[@3DPrinterAcademy]

It depends, for charging a phone the voltage will have to be 5v (USB standard) and the more current / amps the faster it will charge the device.

[@AverageReviewsYT]

@@3DPrinterAcademy didn’t know if the excess volts but less amps would be an issue or not

[@rovicktrono9244]

Try making a bigger version of those many gears into a big one for comfortable spinning when you spin it or you could also use magnets as source of spin.. I'm no science man but I am pretty amused to this kind of things. May sound ridiculous but I still belive in magnets generating energy, like finding right angle for the north and south pole of a magnet pushing each other again and again to produce fast rpms combined with your gears with that big generator for strong electric current!!! Just theoretically, never tried it myself 😂😂😂

[@alansmithee419]

On top of what others have pointed out, have you made sure you're inputting the same amount of wattage into each system? Sure, the small one produced less, but how do you know this isn't just because you were inputting less energy?

[@IoMarievoet]

hi, what are your dimensions of the gears? for a science project :) thx

[@LonelyPix]

Can you like make gear box like this which like makes the last gear spin soo fast that in a hour atleast you can power up your whole house for 10 minutes, it would be such a energy saver

[@mattybear312]

Make a fast gearbox with so many gears that it breaks the sound barrier

[@Thelonuh]

Could an unwinding spring be used to automate the crank for some time? A big, strong spring like the ones used in garage door openers? And for that matter, wouldn't increasing the time it takes for the first gear to revolve once (maybe by adding gears to the system then compensating for the added necessary force with a stronger spring?) mean that the spring would take longer to unwind, thus elongating automation? How far could that be taken? How long could an unwinding spring automate the system? If it could. I'm no engineer and I'm sure the nature of my questions reveal my ignorance. But I thought it seemed like a simple enough mechanism with potential.

[@daniellands6984]

Can you explain how to start 3d printing from scrach.

[@LaxM]

A high speed drill should be used to spin the high-gear ratio box.

[@ted_van_loon]

making those gears out of metal doesn't need to be expensive at all if you are smart. look closely at the gears they have no complex shapes and so are easy to stamp cast. essentially just get very fine sand somewhere or add someting to white sand to make it more sturdy when dry, but finer sand is beter. just put it in a simple frame, push the gear into it and shape some sand around it, pull the gear back out for the hole in the center since you will probably will break the sand there, you can either already put in the axis this way the gear will be stuck to it directly after casting due to shrinkage. another method is using a thin roll of paper make it the size of the axis, put sand in the middle. you can cast it with general aluminium since that is very easy to find. or you can use zamac, such as za12 which is much cheaper if you need to buy it, and also is much more easy to cast, melting at a lower temperature yet stronger in general. essentially for a few dollars you can litterally cast clones of your gears, due to the shape you don't need to do complex things like buring or dissoving out the gear shape, instead you can just press/stamp it in and take it out. of you lack hand coordination then you can use a 3d printer to pull the gear back up by using the z axis of the extruder. or for people not having those make a simple structure, 2 wooden beams or planks above eachother or one thick enough one, drill a hole through take a rod fitting finely through it but still easy to move up and down, attach the gear and and pull the rod to take it out. ofcource if you have a hand which isn't to shaky you don't need such things especially if you can find propper fine sand. make sure the sand is dry before casting however. while if you know what you are doing sometimes you can get away with it being slightly moist, for beginners it is best to make sure it dries. molten metal is hot. hot water expands to steam, so steam explosions in metal, which might not always be fun.

[@graphenepixel8231]

Your multimeter looks exactly like mine.

[@soheil5710]

Better to connect the motor wires to a known resistor, then calculate power via: Power = (Voltage^2) / Resistance

[@senthilvar2000]

why are you not using the same motor on both version ?

[@maxmartin4225]

Instead of a hand crank could a heavy weight on line that unravels as it falls (slowly due to the resistanceof the gear ratio), maybe the height of the room for prolonged duration?

[@mr.bright684]

which 3d printer do you use?

[@tiemen9095]

The measurement method is highly flawed but the result is correct. The mechanical power is torque X RPM, and the only thing a gear does is exchange torque for RPM or vice versa, and lose a bit of energy through friction in the process. So more gears is never more power. It also depends on how well you can crank it, and it seems like it is much easier for your hand to crank the big generator than the fast one. Therefore, likely you are adding more power into the system with the big generator. A slow but powerful drill with constant power output would have been a more precise way to add power. Also, you cannot measure the open circuit voltage and short circuit current and multiply them to get power. That is simply not how it works: that small generator's voltage output will plummet the moment you load it and allow it to generate current. Use a resistance to dissipate the power instead and measure the current through the resistor and voltage drop over the resistor. Best is to use two multimeters to measure simultaneously but I can understand that you have only one, so this method would allow you to to measure current and voltage in different setups and multiply them to get a decent method of the power output.