Theory...and i don't know how...

[Barrett Russell]

Ok, so I got to wondering about needle speed (NOT HPS), and how to get past needle hang up, and if it is wanted.

So first, it seems quite obvious that when converting rotational force to linear, that the speed will come to a dead stop at both end of the linear travel. The shorter the stroke, the more TIME the needle is in the skin regardless of HPS. A traditional machine on the contrary is not so affected by stroke length, as the snap and speed of the needle IN THE SKIN, in a properly tuned coil machine, relies solely on the rear spring tension (coil stick feels odly like running a rotary). So to minimize skin hang up using a rotary (i come across this while i bg shade as well as lining on occasion), it would seem to make sense to run a longer stroke than common in a coil machine, which is what one typically sees in rotaries anyhow. However, this longer stroke would most be benefited to lining, paradoxical to a coil machine. My question is, has anyone actually measured needle speed of a coil machine at skin depth portion of the cycle given what so be the hps? 50% duty does not equate to the speed either, for this simply indicates contact times between points. Further, has anyone tried, be it vibrating as hell, something like a 6 or 7mm stroke length? I think special tech has done some crazy long strokes. Ever tried for lining? This long stroke regardless of hps will increase needle speed in the portion of the cycle, insanely fast at 45d and 135d of the cycle, but mimic more the speed at the business ends of the needle. Just a thought.

also, wasn't really sure where to put this post.

[Sekt]

At 6 or 7mm, the power required to drive the needle/s is allot more to get the same hits per second as 3 or 4mm. So you have to wack up the volts but my guess at 6 or 7mm, the current motors will not run a 7mm machine or if they do, the motor will get pretty hot. The other point to note is a motor rated to run well at 4mm has some give in the motor itself, as it will bog down, giving feedback. So if you used a motor capable of a 7mm stroke without getting hot, it would be heavy, with little feedback in the skin.

[Barrett Russell]

hmmm, I have never relied on give feel while using rotaries. The one thing i like however is i can feel the penetration through the tube better with them, i can FEEL the depth. Also give might be the wrong word. There is no give in an electric motor, it may slow a bit is all. As for pushing 7mm vs 4mm, the only thing relative would be fly wheel/excenter weight (sorry if terminology is incorrect), because the needle bar is further from the fulcrum of the motors rotational center (must clarify, i am thinking this design for an a-bar driven stile machine or dd), its drag is slightly more, however once the balanced excenter is spinning, you could allow the weight to work with you in way of torque? especially with those artists who leave the machine run, would be a benefit. but really i dont think a 22mm remax motor would have trouble pushing 7mm at all.

[Barrett Russell]

also...because the needle is more in the skin/main drag portion at the end of the rotational cycle with a larger excenter, the fulcrum exists exponential greater at 45d and 135d, which would relieve an incredible amount of skin drag on the motor.

[Barrett Russell]

in any case, i will machine up a 7mm, and do some test lines, quick like, single pass, alongside a shorter stroke and tell ya'll what i think feel wise and ink deposit wise, ill let them run a while as well and measure temp.

[Sekt]

There is no give in an electric motor

I disagree, there is give but not the kind of give/yield of a spring. A motors give is not spring tension, but magnetic spring. If there was no give, the machine would not be capable of slowing down, but I don't want to nit pick over words.

however once the balanced excenter is spinning, you could allow the weight to work with you in way of torque?

Well rotational torque is very different than momentum, and I think you could be getting the two mixed up? Torque is a moment of force, whereas momentum is mass and speed combined. Torque would relate to the power of the motor, momentum would relate to the mass of the flywheel. But momentum in my humble opinion, is a character of all the best machines. Although mass, and velocity doesn't necessarily have to be with the flywheel, in the case of some of Nicks machines some momentum is generated with the counter balanced arm bar. However balancing the mass of the arm bar with an opposite and equal weight on the other side of a flywheel, would give a very special characteristic. In my opinion, a flywheel aids the motor in its work, allowing a lighter, motor, with the same punching ability as a machine with no flywheel, and at lower volts, giving the machine longevity also.

i dont think a 22mm remax motor would have trouble pushing 7mm at all.

Lots of motors can push 7mm and bigger. That's not the issue. Thing is, sacrifices must be made, and one must weigh up whether these are worth having a bigger motor in the first place.

[Sekt]

A good example of momentum is, say you have a nail, and you rested a hammer on top of the nail, and pressed as hard as you could. It wouldn't be possible to press the nail in the wood. Now say you used a one inch by one inch piece of wood, but as long as a hammer, and tried to whack the nail in- still wouldn't be able to do this, because in the equation of momentum, you need mass, and speed. Even though you now have speed, as baton of wood is long, you don't have mass, even though you have plenty of power/force/torque. Same with a machine. Some will try to build a machine, not understanding this principle, then because the machine doesn't have enough momentum, it won't drive a large mag. So they'll try to make up for this lack of momentum by using a bigger motor. But then that has its disadvantages, and the machine design suffers.

Say you now used the business end of a hammer. Now you got mass, and velocity, and can easily drive the nail in. Thing is the power hasn't changed when trying to press the nail in, or whack it in with a baton, or use a hammer.
Its the same with a machine. The more mass, say in the form of a flywheel, the more the machine is able to drive the nail in! Even a very small motor will be able to drive the needle in, if it has the correct mass. Although at some point, the mass will become too much for the motors ability to drive it.
A flywheel is effectively a hammer. Then again some prefer to have more or less momentum depending on what suits their style. Just my two cents... the builders here are experts at this kind of thing.

[slicksteel]

yep that is why some coil builders will put a bar the is thicker on the end or wider-more mass to sling.

[Barrett Russell]

Very good points sekt, and yes torque was a horrible misuse of terminology. I meant thrust by way of rotational mass via the flywheel. hence my saying the larger excenter acting as a flywheel may actually compensate for the increased needle speed/drag of a longer stroke. I would like to hear some machine builders chyme in, however i understand reasons for why they wouldn't want nor feel compelled to join in on my naivety.

[Sekt]

Cool bro we're all learning, me most of all. Glad post was useful =]