Author Topic: generators: ideal target rpm for target voltage  (Read 4907 times)

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brandnewb

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Re: generators: ideal target rpm for target voltage
« Reply #33 on: June 24, 2022, 08:26:04 AM »
Did you use FEMM for the calculations or unaided?

I made a mistake in my original calculations. I am sorry about that.

The number of turns per coil should be 32, not 250 as I stated previously.
Somehow I calculated for 3 coils per phase instead of 24 coils per phase.

My calculations were for only one stator with 72 coils on one side of the magnet rotor.

On the other hand, if you only get 134 millivolts with a coil of 9 turns, that tells me that the flux reaching the coils is slightly less than I calculated for. It also depends on how far the test coil was from the magnets.

As for the online calculator, I have no idea where you get the default RPM. As far as I know, there is no default RPM on that calculator. I don’t know where you got the 137.5 RPM.

They seem to have a default TSR value of 6, which is a bit low for a HAWT, but too high for an H-Darrieus VAWT.

Ed

brandnewb

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Re: generators: ideal target rpm for target voltage
« Reply #34 on: June 24, 2022, 12:35:17 PM »
Never mind. I'll be printing a disk for traditionally arranged magnets and run the exact same experiment again. Using the same multimeter, same coil, same position of the coil on the disk and of course 60 rpm

Then we'll have something tangible.

Please give it a few days. I'll report back

brandnewb

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Re: generators: ideal target rpm for target voltage
« Reply #35 on: June 24, 2022, 02:38:43 PM »
wow, I made a huge error in my approach in collecting data it seems.
I believe Marry B tried to warn me about this is my other thread. My apologies for not catching that sooner.

There is no theoretical zero point where two opposite poles meet. I came to the wrong conclusion because I always held the Tesla meter the same way. Always perpendicular to the disk rather than the opposite of perpendicular to the field lines direction.
I just tried again with a traditional arrangement and this time changes the orientation of the meter and there it was. A constant high reading!!. I feel so silly ;(

So it might well be that traditional is indeed just much better. I'll report by how much once I have data.

But now I have a new worry. In case I do go traditional then a 5mm disk is really too thin. Although I had always planned to use high temp resin to coat the disks, whether repelling or traditional the resin alone will not be enough to make the disk strong in a traditional scenario.

I can make it thicker, which I think I should do anyway due to magnets really do not like getting hot.
https://www.kjmagnetics.com/blog.asp?p=temperature-and-neodymium-magnets

But now the question is by how much thicker. I don't want to go too thick as not to waste perfect flux doing nothing. But too thin and the magnets risk getting too hot and demagnetize.

MagnetJuice

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Re: generators: ideal target rpm for target voltage
« Reply #36 on: June 24, 2022, 03:55:41 PM »
I think we are making progress.

When I did the calculations, I used .25 Tesla for the value of flux. Using the traditional way (face of magnets out) the Tesla value would be about .46 for the N45 magnets.

The voltage measurement that you did confirmed that the value of .25 Tesla that I used was very close to what you have now.

That means that if the magnets are arranged in the traditional way, you can expect to get over 75% increase in voltage for the same RPM.

If you stack the magnets, you can almost double your flux, reduce the diameter, and you can print a thicker form.

Like this:



I'll do some calculations later today, using the traditional arraignment and see what the difference would be.

Ed
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brandnewb

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Re: generators: ideal target rpm for target voltage
« Reply #37 on: June 24, 2022, 04:08:46 PM »
WOW!! This is getting exciting.

Earlier I was opposed of reducing the magnet count due to rpm reasons. But since I learned here that 60 rpm will make the turbine not have any power having 96 magnets for field refersal frequency reasons is no longer a valid focus point.

So I think I will go straight to stacking then rather than experimenting with different setups.

It will enable me to print the magnet and coil disks in a single print rather than 4. sweeeeet!!

I am so glad at the moment, If you guys are interested in more experiments I am more than willing to run them anyway just to return the favor.

If you guys are all good as is then I will skip to the stacking design at once.

did I say sweeet already? :)

I think we are making progress.

When I did the calculations, I used .25 Tesla for the value of flux. Using the traditional way (face of magnets out) the Tesla value would be about .46 for the N45 magnets.

The voltage measurement that you did confirmed that the value of .25 Tesla that I used was very close to what you have now.

That means that if the magnets are arranged in the traditional way, you can expect to get over 75% increase in voltage for the same RPM.

If you stack the magnets, you can almost double your flux, reduce the diameter, and you can print a thicker form.

Like this:

(Attachment Link)

I'll do some calculations later today, using the traditional arraignment and see what the difference would be.

Ed

JW

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Re: generators: ideal target rpm for target voltage
« Reply #38 on: June 24, 2022, 05:42:15 PM »
brandnewb!!!!!!

Your doing it again. DO NOT answer your own posts. Have consideration for your fellow members. I am considering blocking you for 30 days...

JW

JW

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Re: generators: ideal target rpm for target voltage
« Reply #39 on: June 24, 2022, 05:55:43 PM »
Instead of multiple posts, open a word pad file. That way you can refine your remarks as a draft, and only post once with a complete train of thought.

MODERATOR EDIT: Vulgar language and aggressive attitude not permitted on this site.
« Last Edit: June 26, 2022, 08:38:10 PM by SparWeb »

MattM

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Re: generators: ideal target rpm for target voltage
« Reply #40 on: June 25, 2022, 05:26:15 AM »
JW? The project isn't uninteresting.

brandnewb-

Be aware the limits of stacking.  Some magnets do not really do anything when stacked.  Stacking of ceramic magnets may show almost no gain.    Stacking thick magnets may show so little gain you are better off not. 
« Last Edit: June 25, 2022, 10:20:39 AM by MattM »

JW

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Re: generators: ideal target rpm for target voltage
« Reply #41 on: June 25, 2022, 06:40:31 AM »
Here is a PM from brandnewb
Hello JW,

I do not mean to offend and/or annoy.

Would moving all my threads to the dairy section, like has been done once earlier, be a solution to my rambling offending/annoying anyone?

I hope that helps.

Kind regards,

I dont think moving any posts is the answer this time. I just don't like to see the front page loaded with repeated posts.

I think the multiple replies are crowded on the front page on the forum. Like I said use wordpad or something similar, make a draft combine all the potential reply's in to a single reply. We like reading long reply's.

No harm no foul...     

Damit I just found a bug in the forum software. On to the next thing.

MattM

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Re: generators: ideal target rpm for target voltage
« Reply #42 on: June 25, 2022, 10:22:22 AM »
Can't he modify for 24 hours already?

JW

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Re: generators: ideal target rpm for target voltage
« Reply #43 on: June 25, 2022, 10:58:41 AM »
Its best if we leave things intact, like you said its an interesting topic. Over time if its intersecting/best he can just combine his posts. this is nothing more than combining all the reply's he is making, use full drafts before his reply's would reduce the # posts. That would work. So instead of multiple reply's if he could condense a draft on wordpad there wouldn't be repeated posts, which throws off the trajectory on the main post list.   

So making a draft that combines his convective posts[ into a single draft would work.       
« Last Edit: June 25, 2022, 11:15:46 AM by JW »

MagnetJuice

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Re: generators: ideal target rpm for target voltage
« Reply #44 on: June 25, 2022, 11:13:07 AM »
Yes Matt, stacking magnets has limitations.

In his case, his magnets are only 5mm thick, it should be OK.

What can I do TODAY that would make TOMORROW a better world?

DanG

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Re: generators: ideal target rpm for target voltage
« Reply #45 on: June 25, 2022, 04:23:25 PM »
Darwin’s Stacking Law:  As complexity increases so does the chance that one or more magnets goes free-range and destroys stator & other magnets…. Once seasonal (example: sun heating on a calm day) & operational thermal heave/shrink cycles AND moisture (corrosion and/or ice heave) work on magnet matrix unless mechanically bound (hard to do) one magnet will creep or flip out, murderizing the entire jenny alt…

Also note the OEM of neo-magnets use silicone and other persistent lubricants to decrease wear & tear of production equipment -  even faint traces if not completely solvent washed will help defeat any glues/epoxies the end user smears on them.. .
« Last Edit: June 25, 2022, 04:34:03 PM by DanG »

MagnetJuice

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Re: generators: ideal target rpm for target voltage
« Reply #46 on: June 26, 2022, 02:27:01 AM »
DanG, I am glad that you raised that issue; very important.

Years ago I did a test with .5 inch round magnets. They were .25 inch thick. I wanted to know if they would hold up under high RPM.

I took 8 magnets and glued them in pairs (4 pairs) then glued them to a 7 inch saw blade.
I took it outside and spun them with a corded drill at around 1200 RPM for a few minutes. I did it remotely because I didn’t want a magnet in my skull. They held up fine.

Before I glued them with epoxy, I cleaned them with WD40, then with 99% isopropyl alcohol. After that I used steel wool to roughen the shiny finish, then more cleaning with isopropyl.

I only put one drop of epoxy between the 2 magnets and between the magnets and the saw blade.

Maybe Darwin’s Stacking Law hadn't been discovered yet.  :D

I think that brandnewb wants to use this for low RPM anyways.

Ed
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brandnewb

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Re: generators: ideal target rpm for target voltage
« Reply #47 on: June 28, 2022, 03:04:04 AM »
Thanks guys for all the contributions thus far.

Normally I'd be all over responses but I am going to try and be less chatty as long as this thread is not in the dairy section.

Anyway I have an update regarding the construction of turbine blades.

Basically there are many roads that lead to Rome.

I have tried several prints settings and basically one can print really sturdy blades.

All my tests are done using the NACA 0015 airfoil shape and a printer nozzle diameter of 0.4mm

14892-0

On the left we can see a 0.3 layer height with a wall count of 4 including 3 internal stiffeners (on the monitor one can see how the stiffeners have holes, i'll explain more later)
This print is still a bit bendy but is absolutely strong enough for mild testing in controlled conditions and it really wants to come back to it's original shape.
Once one is satisfied with the performance then one can fill the hollow structure with pour-able foam (that is why the stiffeners have holes) to make it testable in high turbulent conditions.

If tests then are also to ones liking one can make the blades battle ready by putting glass fiber sheets with resin on top of them.

The up side of this method is that I can my carbon fiber PLA, increase wall count to make it so strong that one does not need to worry about foam and or fiber glass.
But that would only add to the already way too long print times (13 hours for a single 33cm high by 20cm chord length piece)

I do have larger nozzle sizes though but I am not done yet experimenting as on the right we can see a 0.4 layer height 3 wall count, without internal stiffeners test.
The layer height makes it more easy to get resin in the groves to harden it. Now this configuration is not strong enough but adding resin does greatly increase the strength.

I am now printing a 4 wall count 0.4 layer height test without stiffeners to see where this resin path will lead me.

Print times can be reduced massively like this and adding resin is a matter of minutes.

The good thing about 3d printing is that although depending on the print settings it can take hours if not days. But during that time one is free to do other things.

I've also figured out a way to attach the pieces together in a strong manner and as to be able to change the angle of attack on the fly. More about that later when I have actual prints of those components.

Now before I spend days if not more making all the components. Is the NACA 0015 the ideal airfoil to start out with or should I really be using some other airfoil?

Please excuse me for being blund but all the research I find is very technical and sometimes even wooly. I for one can't makes heads or tails from any of it :(

EDIT: Also, printing molds of any shape is baked into the Cura slicer software. It's a simple toggle and then one has a mold to print one can fill with foam and coat with fiber glass.
I am certain that making blades will become as easy and little time consuming as baking pies in the future using 3d print technology.
« Last Edit: June 28, 2022, 03:29:06 AM by brandnewb »

brandnewb

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Re: generators: ideal target rpm for target voltage
« Reply #48 on: June 28, 2022, 12:19:48 PM »
Fear not though.

I have got an insane amount of PLA left and also an insane amount of drive to figure out what is the best way forward

I do really do not like this 2mb limit on image postings :( it makes my already troubled process even more troubled. :)

Anyway here we have a .4mm layer height 2 wall lines, yet with a similar structure 4mm retracted and then filled in at 20%

14893-0

I could go on for days trying to figure ut the best way to print.

I would really hope that one of you just tell me which airfoil to use?

EDIT: btw this print is nearing a stiffness that one can use for testing in calm environments. (non turbulent)

Mary B

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Re: generators: ideal target rpm for target voltage
« Reply #49 on: June 28, 2022, 12:50:50 PM »
Print a rounded area down the center sized to fit common aluminum tubing. Slide a piece in as a stiffener. Could even stack sections for longer blades.

MagnetJuice

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Re: generators: ideal target rpm for target voltage
« Reply #50 on: June 28, 2022, 01:30:23 PM »
A lot of people say that a symmetrical profile like the NACA 0015 or NACA 0018 should be used for a VAWT. After doing a LOT of research, I have some doubts about symmetrical profiles for H-Darrieus.

All my research shows that something like this should work very well.

14896-0

Also, Delft University of Technology in your country had good results with simulations of this profile.

14897-1

The small negative camber on the inside helps with self-starting.

Thicker blades start easier, but have more drag and run slower.

Thinner blades with a sharper, pointier leading edge have less drag and run faster, but are harder to self-start.
Thinner blades are best when there is a small drag device in the center of the turbine to help with the start.

That section that you printed looks really nice. I think that 3D printing will be useful for printing blades, but not for printing alternator parts. Not with the present technology, maybe in the future.

I still have to do some calculations for your alternator but I have been very busy with other projects.

Ed
What can I do TODAY that would make TOMORROW a better world?

brandnewb

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Re: generators: ideal target rpm for target voltage
« Reply #51 on: June 28, 2022, 06:11:57 PM »
Print a rounded area down the center sized to fit common aluminum tubing. Slide a piece in as a stiffener. Could even stack sections for longer blades.

WOW, you keep hitting the mark far more than you miss it. Once again My sincere apologies for not always directly seeing what it is you are meaning to say.

Yes!! that is an excellent idea!!

And I should (and want to) add, Thank you!! Marry
« Last Edit: June 28, 2022, 06:57:21 PM by brandnewb »

brandnewb

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Re: generators: ideal target rpm for target voltage
« Reply #52 on: June 28, 2022, 06:17:14 PM »
Yes Ed, Thank you!!!

If Adriaan does not object then I am going with this suggestion. I mean why not Adriaan?

Yes, our country still has some things left to marvel over and be proud of luckily. But that will soon change I am afraid.

What are you looking to calculate further then my brother? Have not we already concluded that I was deluded?

A lot of people say that a symmetrical profile like the NACA 0015 or NACA 0018 should be used for a VAWT. After doing a LOT of research, I have some doubts about symmetrical profiles for H-Darrieus.

All my research shows that something like this should work very well.

(Attachment Link)

Also, Delft University of Technology in your country had good results with simulations of this profile.

(Attachment Link)

The small negative camber on the inside helps with self-starting.

Thicker blades start easier, but have more drag and run slower.

Thinner blades with a sharper, pointier leading edge have less drag and run faster, but are harder to self-start.
Thinner blades are best when there is a small drag device in the center of the turbine to help with the start.

That section that you printed looks really nice. I think that 3D printing will be useful for printing blades, but not for printing alternator parts. Not with the present technology, maybe in the future.

I still have to do some calculations for your alternator but I have been very busy with other projects.

Ed

MattM

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Re: generators: ideal target rpm for target voltage
« Reply #53 on: June 28, 2022, 07:43:29 PM »
Surely you know how to layout patterns.  So use the 3D printer to make your supports.  Your skin stiffness dictates your spacing.  Drill holes in the nose of each spacer.  Place a peg in the hole.  Drill holes vertically through your spacers for a (threaded) rod to pass top to bottom.  Use a pattern to evenly mark holes horizontally into your spacers for where you can fasten the skin.  Drop your spacers one by one onto the rod.  Cut tubes that can fit over your rod to hold spacing vertically.  Tighten nuts down to hold the skeleton together.  Mark your skin and pre-drill.  If your worried about the skin sagging the run wire top to bottom every inch or so, and keep it tight to support your skin.  You may have to notch slits so the wire sits flush to the spacer, and doesn't push out on the skin.  Slide the skin over the nose pegs.  I'm assuming your skin is vinyl or pvc paneling.  Add plumbing primer and slow curing glue over the spacer sides, but only on the side your working on first.  Then do the second.  Use countersunk screws to tighten down the skin into those pre-drilled holes on your spacer.

The real trick is how to fasten your wing to the rotor.

JW

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Re: generators: ideal target rpm for target voltage
« Reply #54 on: June 28, 2022, 07:58:06 PM »
brandnewb
If Adrian does not object then I am going with this suggestion. I mean why not Adrian?

He has a website something the other day he established himself.

I was the one who added his site to his url on the signature of his posts. He is a longtime member of fieldlines.   

MagnetJuice

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Re: generators: ideal target rpm for target voltage
« Reply #55 on: June 29, 2022, 04:18:43 AM »
To see my name in the same paragraph as Adriaan is an honor to me.

I have learned so much from Adriaan; from his reports and from his posts on this forum.

I agree that he is an asset to this forum and to The Netherlands also.

Ed
What can I do TODAY that would make TOMORROW a better world?

brandnewb

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Re: generators: ideal target rpm for target voltage
« Reply #56 on: June 29, 2022, 08:42:35 AM »
brandnewb
If Adrian does not object then I am going with this suggestion. I mean why not Adrian?

He has a website something the other day he established himself.

I was the one who added his site to his url on the signature of his posts. He is a longtime member of fieldlines.   

Yes I know, I am so serious about this project that I even looked up Adriaan's contact details on his website a while ago and called him. During that phone conversation we settled on 20cm chord length and I made the promise to keep informing about progress/results whether good or bad.

Based on all contributions made here by members I can home in on something worthwhile and I think I have struck stiffness gold now by using circles all throughout the chord that touch the outer(only) wall. One or more of those circles can be used to place aluminum rods through.

And once I have a spinning turbine that actually generates something I can be happy with then I'll release all my work open source.

Still, if one is just as excited as I am and wants some source files already just let me know.

EDIT: i'd love to share an image but this size restriction is nagging a bit. I'll jump through all the hoops once I have something more robust.
« Last Edit: June 29, 2022, 09:06:39 AM by brandnewb »

brandnewb

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Re: generators: ideal target rpm for target voltage
« Reply #57 on: June 29, 2022, 09:43:54 AM »
That section that you printed looks really nice. I think that 3D printing will be useful for printing blades, but not for printing alternator parts. Not with the present technology, maybe in the future.

Please allow me to give more context brother.

I never intended to only build a PLA based wind turbine alternator/It turns out that  PLA is just for place holding.

The name of the game is to always flow with the data. So now.

My intend is to use 3d print technology to aid in prototyping. Although Give it a few years and then maybe filaments are strong enough. For example I have a very expensive roll of carbon fiber filled filament.

Once the prototype phase is done I will switch to mold mode. And cast parts out of aluminum.
« Last Edit: June 29, 2022, 10:41:49 AM by brandnewb »

MattM

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Re: generators: ideal target rpm for target voltage
« Reply #58 on: June 29, 2022, 11:54:34 AM »
The good thing about stretched skins is that they provide structure between bracepoints.

Mary B

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Re: generators: ideal target rpm for target voltage
« Reply #59 on: June 29, 2022, 12:31:10 PM »
Another benefit of the aluminum tube don the center, it gives you a solid attachment point for the spars that go back to the center hub.

brandnewb

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Re: generators: ideal target rpm for target voltage
« Reply #60 on: June 30, 2022, 03:16:18 AM »
After some more experiments I am happy to announce I think I found the golden ratio in terms (using PLA and 0.4mm nozzle size) of print speed, material use and stiffness.

please see the rae 2822 airfoil as stiff as it's gonna get using 3 wall lines at 0.4mm layer height..

In fact this route might end up being too rigid! I really would like some flex to be able to deal with impact from hail and what ever mother nature can throw at us.
But since I am now going more modular with modules of 50mm each, replacing one if there should come impact damage should be a piece of cake.

14898-0

The trick is to have the walls overlap during print time. A little counter intuitive it is that during modeling we have to keep some space. One day I find a way to actually print what I am modeling but for now I am just working towards a print I am looking for by trail and error.

I will no longer bother going the foam route since I have something this rigid and strong and will be using the aluminium rod suggestion I will be ordering to run through the blades.

Also, and please do not tell this to my municipality. I think I will try and defy the local code. Maybe a 3m diam turbine just looks better ;)

Now to make sure we all are on the same page. I was really busting my b@ls here getting closer to something worthwhile.
14899-1

And as stated above I think I found it.

It's confirmed. I found a way to print a blade too stiff for it's own good.
14900-2

I am going to try to see if I can reduce rigidity to make it more hail storm survivable..

I realize that there are some protrusions. at the tail. But that is not my focus for now. Sure I'll make sure i'll align the circled stiffeners properly next time.

This path is going somewhere!!
« Last Edit: June 30, 2022, 11:21:13 AM by brandnewb »

JW

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Re: generators: ideal target rpm for target voltage
« Reply #61 on: June 30, 2022, 08:35:00 AM »
Quote from: brandnewb
My government does not allow for firearms so I have non.

Yaaa thats pretty far of topic. I have no firearms either not a big deal, Law Enforcement carry's for us here in the USA. My ex-wife has a carry conceal permit...

bigrockcandymountain

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Re: generators: ideal target rpm for target voltage
« Reply #62 on: June 30, 2022, 09:43:41 AM »
I have quite a few guns here in Canada and am legal to own them.  It is a pretty easy process to get a licence to own guns here, except for assualt rifles.  I don't have a 3d printer and none of my guns are quite what you would need for your experiment.  They are all either .22 rim fires, shotguns, or high power hunting rifles. 

Living in the country, it is wise to have guns.  I can't imagine not having them. 

I have been shooting since i was about 6 years old and reloading ammunition since i was 12. 

I get the feeling it would take more thickness than you'd be willing to wear to stop anything but the weakest bullets.  Where are you located?

bigrockcandymountain

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Re: generators: ideal target rpm for target voltage
« Reply #63 on: June 30, 2022, 09:54:44 AM »
We could maybe move these last few posts to a new topic in the pub?

brandnewb

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Re: generators: ideal target rpm for target voltage
« Reply #64 on: June 30, 2022, 10:58:21 AM »
I have quite a few guns here in Canada and am legal to own them.  It is a pretty easy process to get a licence to own guns here, except for assualt rifles.  I don't have a 3d printer and none of my guns are quite what you would need for your experiment.  They are all either .22 rim fires, shotguns, or high power hunting rifles. 

Living in the country, it is wise to have guns.  I can't imagine not having them. 

I have been shooting since i was about 6 years old and reloading ammunition since i was 12. 

I get the feeling it would take more thickness than you'd be willing to wear to stop anything but the weakest bullets.  Where are you located?

I am from the wrong side of the pond, in The Netherlands.

I am not sure about the extend of this forum but there will come a time in where I will be suggesting floating cities as a sub topic to many fora.

JW

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Re: generators: ideal target rpm for target voltage
« Reply #65 on: June 30, 2022, 11:54:26 AM »
Quote from: bigrockcandymountain
We could maybe move these last few posts to a new topic in the pub?
Modify message

No problem i will make a new topic in the Pub, and transfer these replys, let me finish my second cup of coffee

We wil call it Guns and Ammo