V-belt adjustment

[Evo160K]

Is there a rule of thumb on a Singer 45 for determining when a rubber v-belt is adjusted properly?  A search of this forum found nothing.  Thank you.

[Singermania]

I expect an engineer will give you some serious technical advice on this, however in our business we find that its rule of thumb.... ie if its too loose it slips and or flaps, if its too tight you and the machine will find the handwheel hard to turn (assuming the clutch is disengaged on a clutch motor) and you will stress the motor and burn out its bearings.

 

[Gregspitz]

should it be real easy to turn manually with a speed reducer attached to a servo motor...

I can move mine but it takes a bit of effort..maybe I have to loosen the belt from the motor to the reducer???

 it is sewing fine

[mikesc]

Don't "fix" what isn't broken..

[Evo160K]

Thanks Singermania, that helps.  Thank you.

[Singermania]

No, once you put a speed reducer into the equation the gearing, friction and inertia are working against you and it does become a bit more difficult to turn, however (depending on  how strong your are) it should still be able to get rolling.... again when its too tight it will be really hard to turn over.   We find on the box style reducer that the first thing to slip is the small reducer pulley as it doesn't seem to have the depth of other pulley wheels.

[Gregg From Keystone Sewing]

See attached.  I've never used this or needed to; after a while, we do it by feel.  But, if you don't know what is too tight or too loose, here is a baseline guide.

Too loose, the belt will slip.  This is not a timing belt or chain on an engine; you'll never damage the machine by slipping the belt on the pulley if it is too loose.  

Too tight, at the motor can jack rabbit start, as where you push down on the motor treadle and the motor goes from zero to 60 with no control in between.  This can also put excessive load on the machine and motor pulley and prematurely wear out these parts.  

Edited July 15, 2016 by Gregg From Keystone Sewing

[Art]

Gregg is correct about the belt situation.  About an inch of deflection with a moderate push sets things up just right.  Now with today's servo motors, a 1/2 inch is ok too.  In the days of the clutch motor (probably still that way in factories) you would back off the brake and set the belt loose.  A lot of folks used the balance wheel and their hand as a kind of brake so they liked the belt tension sometimes a little looser than nominal.  You're not going to hurt much setting the machine up a little loose, but setting tight enough to load the bearings other than the bare minimum is not going to be great.  After a while working with machines, they have a particular sound when the belts are too tight.

Art

[graywolf]

Rule of thumb for setting v-belts in general:

1/2" inch of slack.

That is on one side between the pulleys, of course.

Never, ever, less than 1/4 inch as you are likely to damage something.

1 (one) inch and it needs to be tightened because it is likely to slip. Actually if your belt has stretched to where it has one-inch or more of slack to ought to be replaced (assuming it started out properly adjusted).

There are exceptions to the above for very long or very short runs of belt, but if you shoot for that half-inch you are usually good to go.

[Art]

I'll stick with 1" for a clutch motor, and some of my servos are set-up that way too.  Never a problem, 1" isn't much given the length of belt.  

Art

[Singermania]

Like I said, you were bound to get some serious technical advice.  Trying to work out deflection from a given centre force is a bit serious, not withstanding that all A or V belts are not created equal and will flex or stretch a bit differently.    Really its simple enough, if its too loose it will slip, if its too tight it will bind up the machine and the belt will practically ping if you flick it with your finger.   Its a wet rainy day here and am catching up on some leisure time, hope everyone out there is also having a good Sunday.

[Art]

Hotter than the hinges on the door to hell here, but finally some rain to cool it off a bit.  Isn't it supposed to be winter down your way, it should be raining or snowing.

Art

[Wizcrafts]

I spray belt no-slip from auto parts stores on my v-belts on my Cowboy CB4500. That way I don't have to overstress the belts and bearings.

[Evo160K]

Thank you good people one and all.

[Singermania]

You're right Art, its Winter here, but up in Queensland its usually shorts and t shirts all year round, so long pants and socks is cold for us..

[Gregspitz]

just after reading this thread..I started sewing with my roller foot machine with the speed reducer in thicker material and the belt slipped!  quick slight tightening AND used some belt dressing I had from the auto parts store that I spread evenly on both belts with a small sponge...and it seems to be working better than ever!

thanks everybody AGAIN!!!!!!!

have a great day

[GPaudler]

Though it's often cited and is about as scientific as most people care or need to get, a simple measurement of V-belt deflection really isn't very meaningful. 

It's not important but understanding the mechanics might help someone if slippage should become a problem. It's helpful to think of it in terms of friction due to surface contact. A skinny belt on small wheels has much less surface contact than a fatter belt on big wheels so will need less tension to resist slipping. The material and finish of the wheels makes a difference as do the material, age and condition of the belt.

Wiz's suggestion to use belt dressing available from auto parts stores in spray cans or squeeze tubes is good, especially for older, oxidized belts, for achieving maximum friction.

So sure, try adjusting for 1/2" of deflection (though how hard are you pushing?) and if it doesn't slip, then you're good. If it still slips, make sure that your V-grooves and belts are clean and rust-free and treat your belts to some dressing.

[graywolf]

"How hard are you pressing?"

Should be just enough to take up the slack. That is all you are interested in.

Belt dressing, auto transmission fluid works very well. Don't soak, just dampen.

Once again, I am writing from the viewpoint of a electro/mechanical engineering technician with with about 60 years experience. Sewing machine repair, I am just a hobbyist.

[Evo160K]

You people are awesome.  Thank you.