Lincoln Bullet Welder 250 take 2

[Marc]

Hi there! My Lincoln Bullet welder has finally arrived from Queensland. The guy had it in his ute and was telling me it weighted 300 kilos but a bit of a push around told me it was not even 300 pounds, so offloaded it on my trailer and off I went to a repairer who knows the machine. After a couple of weeks, the machine is ready, he is very happy with how it works, very smooth. Plenty of brushes life left in it, amps regulation works very well, the controls for amps and volts are not worn, however ... you where waiting for this right? ... he tells me that he measures the voltage with the machine running with no load and he gets 44 V, yet changing the voltage by turning the knob up or down does not change the reading. He has no way to measure the voltage whilst welding and does not know if the control may work when welding or not ... (?) anyone understand how this voltage control is supposed to work? Your answers as usual are very appreciated

[NCArcher]

Pinched from an old welding forum. Has a bit of info.
If you know the model number you can download a manual from the Lincoln site.

IIRC this welder was developed specifically to burn the new 'low hydrogen'
electrodes developed to solve cracking problems encountered in the welded
steel hulls of Liberty ships during WW2. It was considered a breakthrough
development in welding technology. This generator was most commonly rated
at 300 amps @ 60% duty cycle but IIRC it was also available in a 400 amp
version. IMHO it is the best welding generator ever built, (now ducking and
running). This generator was built with many different drive units, the 3
phase motor generator units are commonly called Lincoln bullet welders due
to their shape, they are GREAT welders but fell into disfavor because they
are noisy, and since they have brushes and moving parts, do not like the
dusty and gritty conditions in most welding shops. Because of this they are
often best located in remote sound insulated clean rooms, and the control
units are often run through the wall so they can be accessed from the shop
area. This generator is also often mounted on different gas engines, the
most common IIRC was a 6 cylinder flathead Continental (or Hercules?) but I
have seen them on Ford flathead V8s and there are many military versions
with other engine drives. They are not commonly used because they are too
heavy for a 1ton welding truck and they burn a lot of gas. The much loved
SA200 is a similar machine but does not have the same fine control over
welding voltage and slope.

IIRC, the left control is an infinitely adjustable amperage control and the
right control has four sectors marked on an infinitely adjustable voltage
control. IIRC, the voltage control is marked large electrodes, ?????, ???
positional, and special applications. IIRC the special applications section
is used for TIG, (which in WW2 would have been called Heliarc). I spent a
lot of time using one in a school when I was doing my pressure certificates
and found it very controllable, but not a machine that you can just walk up
and test on, for that a single control transformer machine is much easier to
set. IIRC the area between the middle and top of the second voltage range
(??? positional, just ccw from special applications) was the sweet spot but
required a lot of tweaking to get set just right and to optimize for
different positions and for the root and cap passes. You can get the same
heat but a different slope by lowering the amps and raising the volts or by
raising the amps and lowering the volts you will get a softer arc with less
dig.

It was a great experience to use this machine for training in a school
setting and it taught me a lot about arc length and manipulation. I was
doing root passes with 6010 and with 7018 straight polarity as well as
capping with 6010 and 7018 reverse polarity.

These machines are often available cheap (copper salvage price) or free,
from people who either do not know what they have or are not prepared to use
and maintain properly.

These machines can weld a lot better than most of us are capable of and are
a great learning opportunity.

[Karl Robbers]

The voltage will change when welding and is easy to check.
Simply set it at minimum volts and run a bead, then at maximum and do the same. The minimum voltage weld will sit up more and the arc will be noticeably shorter than the high voltage weld which will tend to spread more.
Think minimum volts for open root joints and higher voltage for fillet welds etc. Or just set it in t he middle and leave it there.
Have you got a manual for your welder? They are readily downloaded from lincolnelectric.com note no .au on the end.

[Karl Robbers]

I assume your welder is a DC 250 MK. Here is the relevant manual.
im132.pdf
It will tell you all about how to set the current and voltage dials.

[Marc]

Yes, that's the one, I have that manual thank you.
What I couldn't understand from the technician is why didn't the multimeter show the changing in voltage when turning the knob.
Anyway, I'll know soon enough when using it. Thank you Karl. By the way it is not that noisy. About what a water pump noise would be.
There was a lot of dirt, even grass inside, the commutator was a bit bumpy so he made it smooth. Found a few power leeks that needed fixing, changed the plug from an old metal one to a new clipsal, plenty of brushes left, all in all seems to have had little use.

[Karl Robbers]

The old Lincoln bullet welders are damn near bullet proof. You will find that it will make a bit more noise when it comes under load. Some welders may have fancy digital readouts for amperage, Lincoln bullet welders give you feedback by the pitch of the whine as the amps go up. The Lincolns are not as noisy as my old EMF DC generator welder though, it would outdo a jumbo jet on takeoff.
I will be seeing my tame welder repairman on Monday, I will pose the question regarding the OCV.
There are still some places using the larger SAE series welders to power sub arc and heavy gouging, so the old DC generators are still doing an honest days work.
One advantage of the DC generators is that they run 3 phase, whereas a typical large stick welder of the era would have been single phase 415V, therefore the old bullet welder will run on less amperage than its transformer cousin. My Lincoln SAE600, (600A@100% or 750A@60%), sucks 53A of 415V goodness, where a Lincoln Idealarc 400 transformer welder, (400A@100% 500A@60%), is somewhat more greedy and gobbles up 63A.
The DC gennies will run right alongside any inverter and probably outdo it in my opinion, but I wouldn't like to carry one up a ladder