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PostPosted: October 27, 2011, 10:35 am 
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Joined: October 8, 2011, 3:53 pm
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Location: Niagara Falls, ON.
Heh, maybe I'm not with it this morning, I translate that as "I ground tied the ground side of the circuit and nothing bad happened" ..... so? :D

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PostPosted: October 27, 2011, 11:29 am 
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Joined: May 2, 2009, 1:03 pm
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Location: The Humid State of North Carolina
RoadWarrior222 wrote:
Heh, maybe I'm not with it this morning, I translate that as "I ground tied the ground side of the circuit and nothing bad happened" ..... so? :D
I'm never with it!! Always behind it or in front of it, but never with it!

No, that was simply an attempt at figuring out why everyone is looking for voltages that I can't find. I am always the one to try something, make it work and then have the engineers run about trying to figure out how that isn't supposed to work and it was never designed to do it and it's electrically impossible till they actually sit down and figure it out. Then it magically gets incorporated in the next design.

I just ran it as a 120v unit rather than the 208V it shows in the diagram. The "neutral" in the house was simply a grounded leg anyhow (Not a true neutral leg). Straight from the box to the pole. 6" away from the fence pole I used to test earlier.

To me this is more like a bee and its ability to fly. Aviation engineers have stated time and time again how it's impossible for bees to fly, but yet every day, without much difficulty, they do. Maybe this is one of those cases too. It shouldn't work, it should have voltage here, but it does work and it doesn't have any errant voltages that I can find. I'll be trying the light bulb test as soon as I get the garage set up to verify/dispel the conjecture.

I can't explain it, can anyone?

Cheers,

Ken

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Never become a pessimist. A pessimist is correct oftener than an optimist, but an optimist has more fun, and neither can stop the march of events.-Robert A. Heinlein


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PostPosted: October 27, 2011, 4:27 pm 
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Joined: April 16, 2011, 11:05 pm
Posts: 239
Location: Melbourne, Australia.
botbasher wrote:
To me this is more like a bee and its ability to fly. Aviation engineers have stated time and time again how it's impossible for bees to fly, but yet every day, without much difficulty, they do.


A bicycle is absolutely impossible.
If anyone ever built one, it would just fall over.
Any engineer will tell you that you must have at least three wheels.


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PostPosted: October 30, 2011, 8:03 pm 
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Joined: April 16, 2011, 11:05 pm
Posts: 239
Location: Melbourne, Australia.
Anyhow, back to reality, and Locost home brew plasma cutters.

This idea will not work in the US, because of your crazy and unique American power distribution system.
But for anyone outside of the US that has access to proper three phase power, here is what I propose to do....

I already have an old low cost 240 volt stick welder that provides a pretty good ac constant current output from about 20 amps to well above 100 amps.
Open circuit no load voltage is around 75 volts.
Current is adjustable by setting a vertical slider rod which plunges into into a shunt gap transformer.
The low voltage secondary winding is fully isolated from the mains.
This is typical of many ancient "buzz box" stick welders with which we are all familiar.

I have just run some tests with different resistive loads at different current settings, and the constant current feature, while not perfect, will be significantly better than just a high power series "water resistor" in series with a constant high dc voltage.

What I propose to do is buy two more IDENTICAL welders through e-bay, as they are quite commonly available, and fit a 150 amp four diode bridge rectifier to each individual welder.
Then connect all three transformers and rectifiers in series.
When driven from three 120 degree 240 volt phases, the dc ripple currents will pretty much cancel, the dc voltages will add, and with a bit of extra series inductance, it should make a very good quality fully isolated adjustable 200 volt constant current supply.

The main reasons for doing it this way are low cost, FULL MAINS ISOLATION, very low dc ripple current, current adjustability, and massive continuous current capability at high duty cycles.
And it should be pretty easy to do, and be as safe as it can possibly be....

It still needs some extra features to make it fully workable, but that should be fairly straightforward.
The difficult part is getting a good quality adjustable dc high current source, and that is the part I am addressing here.


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PostPosted: October 30, 2011, 11:15 pm 
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Warpspeed wrote:
This idea will not work in the US, because of your crazy and unique American power distribution system.
Shhhh... don't tell my PC... It works just fine as it is and if it actually hears that versions in other countries have better working conditions, it'll go on strike and I'll never be able to get good help out of it again!!

Cheers!!

KS

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Check out Firearm Finishes & Coating for options to ceramic coat your Locost parts. Hundreds of stock or custom colors including Chrome and Clear Coating options now available! High Temp options for hot bits!! Plastics too!!

Never become a pessimist. A pessimist is correct oftener than an optimist, but an optimist has more fun, and neither can stop the march of events.-Robert A. Heinlein


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PostPosted: November 9, 2011, 11:05 am 
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Joined: November 9, 2011, 10:37 am
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botbasher,

Iv'e built plasma cutter that works ok , but would like to improve the cut and increase max cut depth.

Dose it make a difference on how the caps are connected, Ive connected them only across the DC side of the recifier and not like the plasnator guy plans that show the caps connected via the AC side and connected the DC side ?

Also will changing the tip size will this allow thicker metals to cut. (I have the same PT31 gun) ?

Have increased resistance which has inproved cutting thicker steel but this increases current and would prefer to keep the current down.

Cheers

DS


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PostPosted: February 15, 2012, 10:59 am 
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Location: The Humid State of North Carolina
Garagejunkie wrote:
botbasher,

Iv'e built plasma cutter that works ok , but would like to improve the cut and increase max cut depth.

Dose it make a difference on how the caps are connected, Ive connected them only across the DC side of the recifier and not like the plasnator guy plans that show the caps connected via the AC side and connected the DC side ?

Also will changing the tip size will this allow thicker metals to cut. (I have the same PT31 gun) ?

Have increased resistance which has inproved cutting thicker steel but this increases current and would prefer to keep the current down.

Cheers

DS
Hey GJunkie!

Sorry for the delay in answering.. Life called and I had to answer!! I got to meet my daughter for the 1st time just a few days before her 1st birthday and have been making regular 1000 mile trips to deal with all that entails!

OK.. back to car stuff!!!

Caps: You have to connect the caps to the DC side otherwise it won't work (or will work, but not nearly as well!). Caps store energy and if you put them on the AC side, the alternating cycle charges and discharges them instantly (ok, 60x a sec..), but if you put them on the DC side, they accept the increased voltage, store it and then discharge it all at once into the work, creating the plasma arc you need to cut.

Cut Depth: While trying to keep the amperage down yet cut deep, is the holy grail of the DIY PC units. Since we typically have rudimentary controls, our only real variable is air pressure. Increasing the air pressure (to a point) will help cut thicker materials. Unfortunately this has limits, because if you increase the pressure too much you blow the arc out the tip and either damage the tip or make horrible stuttering cuts.

I found a secret to this effort, allowing me to cut 3/8" easily as I would 1/8"! That secret... Drill a hole! If your cutting a 3/8 plate, drill a hole within about 1/8" of your starting point in the same line as the cut. The hole only needs to be a bit bigger than the hole in the tip.. I tend to use 1/8" bits

Why you ask? Think of it like a lens on a laser in that what it does is force ALL the plasma into a single channel and forces it to make the cut where you want it instead of going in any direction the material or tip send it. Once started it's easy to run from there. Then you simply cut the remaining 1/8" section between the parts from the edge. I have used this several times to start cuts in thick pieces or in tubes with great success. It will gouge start, but this assures that I can control not only the molten spray, but have minimal dressing to do.

The "starter hole" method combined with air pressure manipulation (up to a max of about 48psi before the tips paid a price!!) have let me cut pieces that I didn't think I could have. Using a new tip on the thicker cuts also helps, but that would be the same on any unit, even purchased ones.

Hope this helps you to obtain better cuts from your unit. Love to see some pics of what you ended up with!

Cheers!

KS

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Check out Firearm Finishes & Coating for options to ceramic coat your Locost parts. Hundreds of stock or custom colors including Chrome and Clear Coating options now available! High Temp options for hot bits!! Plastics too!!

Never become a pessimist. A pessimist is correct oftener than an optimist, but an optimist has more fun, and neither can stop the march of events.-Robert A. Heinlein


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PostPosted: April 26, 2014, 3:16 pm 
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Joined: February 25, 2014, 4:32 pm
Posts: 1
This is for botbasher or anyone who would like to have something to read

I just want to say THANK YOU

I have had the plans for this PLASMA CUTTER for years and had never got it to run like it should. Back in 09 I bought the plans to build this cutter but the plans were different than they are now , I tried to get it to cut with the same problems you had with and I did not build it his way BUT I have bought all the parts like he did.

I had given up on it for years until I came across this site w/your input. I went out to garage and took it apart and did build it all over again like you did w/leaving that one wire off and IT WORKS. I went and built a new box for it took a lot of pictures to show you and when I went to upload them the site said the pictures were to big , if some one can tell me how to make them smaller I will send off to the group

BOTBASHER THANKS


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PostPosted: December 11, 2014, 6:06 pm 
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Joined: December 11, 2014, 5:46 pm
Posts: 1
I need some help with my plasma torch build.Someone that has build knowledge.Also where to find some parts. I know there is a formula for series or paralell capacitors I have a lot of cap multiples .I also have torrid trans formers and huge 110 tansformers out of huge audio power amps. I also have several good microwave transformers.Its a nightmare Im a diy guy and I have been and into electronics but never this kind some one help me if you can richard johnson (Madd Hatter)


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PostPosted: December 15, 2014, 2:44 am 
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Joined: December 15, 2014, 2:31 am
Posts: 1
send them to my email rramjet1954@hotmail.com I have eichholdsw complete plans but he wont answer any questions or returny emails he could be dead for all I know.My issues are with my caps and my high voltage transformer I have everything else nailed down I have a very large pair of 110 volt torrid trans formers .Ive got huge audio power amp transformers micro wave tx Im about to tear down a 50 inch sony cathode ray Tv .Im so frustrated with this Thank for the time and kindness of your reply ....Rico :BH: :BH: :BH: :BH:


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