Thread: Inverter stick comparisons

Thanks Rusty, the technique of drawing the pool along works fine. I have been welding my little head off and the BOC 130A hasn't skipped a beat.

I have 2.5mm rods and have the power down to 90. It "feels" like it wants to go lower but 90 is the minimum power specified on the packet. How malleable are those recommended power settings on the sticks?
Down at 70 it feels controllable and the weld seems to penetrate OK on 3mm angle iron. Dunno?
Magic little machine though!!

Some people claim that DC welders are effectively "hotter" than AC welders for the same amps, meaning you can run at lower amps with your DC machine.

I, frankly, don't know how true that is - I haven't gone between an AC and DC machine since I got the BOC 130, and I don't really believe the amp dials on welders are particularly accurate.

From memory, I thought typical 2.5mm rods were 55-90 amps, while 3.2mm rods were 90-125 or so, in which case you probably should be running lower amps than 90 on the 2.5mm rods (unless they're some special type).

Hi Rusty,

A 50hz sinusoidal wave can have it's DC equivalent value determined by multiplying it by 0.707 (R.M.S - Root Mean Square) so in other words whatever the AC power of your welder, if you multiply it by 0.707, this will be the equivalent DC power. In other words DC is of course far more powerful because it is always on and does not vary as does AC.

John

Originally Posted by RustyArc

Some people claim that DC welders are effectively "hotter" than AC welders for the same amps, meaning you can run at lower amps with your DC machine.

I, frankly, don't know how true that is - I haven't gone between an AC and DC machine since I got the BOC 130, and I don't really believe the amp dials on welders are particularly accurate.

From memory, I thought typical 2.5mm rods were 55-90 amps, while 3.2mm rods were 90-125 or so, in which case you probably should be running lower amps than 90 on the 2.5mm rods (unless they're some special type).

Your observations are spot on, Rusty. The 2.5mm rods "felt" much better at the lower amperage indicated by the dial. I believe the indication was around 60 or 70 so that would be correct.

I thought sinusoidal was something that came charging out one's nose? Does that refer to the shape of the AC wave?. This is a high quality forum IMO, lots to be learned from knowledgeable people - thanks..

Yes, sinusoidal is the shape of the waveform. It is commonly known as a sine wave. The alternator at the power station spins at 3000 RPM so if you divide 3000RPM by 60 seconds you get 50 rotations per second - 50 cycles per second (50Hz - 50 Hertz). The shape of the wave is sinusoidal because the wire in the rotor (spinning bit) goes in and out of a magnetic field therefore the voltage rises and falls reverses polarity then rises and falls again.

Three Phase - if you wanted to know.
There are three of these windings physically 120 degrees apart on the rotor so the output is 3 x 240v when measuring across a winding with respect to the common connection of all three windings but because they are 120 degrees apart they are out of phase (not in the magnetic field all at the same time. In other words, you can measure 415V R.M.S between the phases. A good way to understand 3 phase is to look at a 3 bladed propellor. The distance between the centre (neutral connection and common earth) and the tip of a blade is for example 240 volts, the distance between the tip of one blade and the tip of another is greater ( this is 415 volts).

3 phase motors = more torque
In lamens terms it's like a 1 cylinder engine versus 3 cylinder, the 3 phase setup provides more torque.

Regards
Pete (Tokentools)

Grahame, just a quick one about your orignal list.

Why did you put the Air Tuff on there? It seems very cheap compared to its competition. Has there been any positive feedback on these?

Hoestly,I can't think why I threw that in.
Probably when i googled and threw in in with out thing to much about.

For that price I don't see it being very good.
grahame

Hi All
OK, I got some scrap metal and started welding with 2.5mm rods at about 50amps (on the dial). Initially I left a lot of drops of chook $#!&. Also I had trouble making the weld flow. After owning the BOC 130 for three weeks I read the instruction manual and it showed the rod being moved in little circles. So I did this and it seemed a bit better. Rusty did tell me to do that!! I then got a "project" which was to re-attach the pole we use to hang our cooking utensils off. It is a solid steel pole mebbe 25mm across and where it attaches to its fixing plate had come adrift. So I cleaned the area up as best as I could and started. It was . OK ... but didn't seem to flowing and attaching to the pole. Looking through the visor I thought I'd have to spend longer with the rod on the thicker metal but this didn't seem to be the case. After many weld on, grind off, weld on, grind off and weld back on again; it looked solid.

Then I attacked my outboard trolley which was made of thinnish 50mm square tube. Aha! Blew holes in that didn't I? I popped a bit of flat steel on it and welded that to make it the new top. At one stage I did blow a hole in it but tried to weld it up and it worked!!

How much of welding is confidence? At the moment my welds appear to be strong but I have very little confidence in their structural integrity. I keep seeing our fire pole bending over and pouring the casserole gently out into the flames to the uproarious delight of our camping mates - my welds as the culprit

The BOC came with a jaw grip type torch, are the screw ones better? The rod seemed to move about a bit?

Thanks again
Peter

You're a brave man having a go at thin-walled tubing I've turned many pieces into colanders from blow-throughs.

The one thing I learned after a while was to be willing to tweak the amps knob - it's so easy to do on that unit. You may find that with the thick sections you're not putting enough amps in, or you're starting to move before establishing a decent weld pool that spans the joint and touches the 2 pieces and establishes some real heat in the metal.

Conversly, for the thin stuff, again be willing to tweak the amp knob, but be prepared to get moving almost straight away (though you still need a proper weld weld pool), and also be prepared to stop the weld before the heat builds up too much and you start blowing holes - on some tubing it makes quite a distinctive noise just before blow-through. At a pinch you can get away with a series of short stitches, which, done well, can look like a decent weld.

As for clamp versus twist, I thought the same thing, so when I bought my unit I also bought a twist holder with the intention of replacing the clamp, but soon found the clamp holder worked just fine, and was able to return the unused twist holder to BOC for a refund.