Difference between using a Larger Pulley vs. Speed reducer?

[tofu]

Speed reducers aren't cheap and they take up a lot of space.  From what I understand, it's just a smaller pulley turning a larger pulley.  Please correct me if i'm wrong.

 

What would the difference be between using the speed reducer or just slapping a 3x larger pulley/flywheel directly to the machine? Do you not get the torque multiplication? Does it stress the servo more than the alternative?

 

It seems large pulleys with proper bore sizes are readily available for under $50, while speed reducers are around $100-120. One could even 3d print a pulley out of nylon if he or she were so inclined.

 

Best,

Chris

 

 

[nylonRigging]

There probably someone here more Tech. that can articulate better on the mechanical science definition . I think the main thing of importance is efficiency . Amount of power put in, related to the amount of power received at the end result.
like you say, It does take up extra space with addition of another belt and pulley .
I have a couple of tables with common used setup (under table ) pulley wheel reduction between motor and machine . The power felt sewing is so much stronger than when just using a single changing of one pulley and a belt size .
Multiplying pulley's . By adding another pulley and belt in-between the drive motor 'clutch or servo' , and the sew machine hand-wheel pulley . The 'torque and the power' is pretty strongly and plainly felt with even using the slow RPM or even in higher ranges of speed .
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[katit]

There is no difference if you can achieve needed ratio using smaller pulley at motor and larger on machine.

[CowboyBob]

Yes,it will slow it down,you will probably need to extend the belt slot so the belt doesn't rub.

[nylonRigging]

10 minutes ago, katit said:

There is no difference if you can achieve needed ratio using smaller pulley at motor and larger on machine.

There must be a upside benefit reason, as multiple pulley and belt reduction placed between motor and machine have been around long before I was born and sewing .
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[katit]

9 minutes ago, nylonRigging said:

There must be a upside benefit reason, as multiple pulley and belt reduction placed between motor and machine have been around long before I was born and sewing .
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Reason is that they do lot more reduction in compact package. Yes, it doesn't seem so because "box and pulleys" but it's under table out of sight. To achieve the same reduction very big pulley needed and convenience for operator reduced (turning large wheel by hand)

It's easy math to calculate reduction, but box used for compactness, nothing else.

Quote

and when the speed of the driven shaft must be reduced beyond what reasonable sized pulleys can produce, speed is commonly reduced by placing an intermediate shaft and pulleys between the motor pulley and the drive pulley 

 

Also, keep in mind, those reducers were sold long ago(?) along with clutch motors. Today I don't think you need to buy expensive reducer box, I'd rather spend money on good servo motor. How slow do you need to go? Motor I got from @Gregg From Keystone Sewing starts very slow and I can do 1 stitch with light tap on pedal (with needle positioner)

 

Edited March 15, 2019 by katit

[tofu]

20 minutes ago, katit said:

Reason is that they do lot more reduction in compact package. Yes, it doesn't seem so because "box and pulleys" but it's under table out of sight. To achieve the same reduction very big pulley needed and convenience for operator reduced (turning large wheel by hand)

It's easy math to calculate reduction, but box used for compactness, nothing else.

 

Also, keep in mind, those reducers were sold long ago(?) along with clutch motors. Today I don't think you need to buy expensive reducer box, I'd rather spend money on good servo motor. How slow do you need to go? Motor I got from @Gregg From Keystone Sewing starts very slow and I can do 1 stitch with light tap on pedal (with needle positioner)

 

Sounds like you more or less end up with the same result. Working on a budget, if the larger wheel fits, it seems to be the better alternative. 

 

As far as how slow I want it, I've seen some videos where the user is able to control the machine throughout the entire needle movement, not just 1 tap per stitch. This level of control seems like it would make it easier to sew small intricate shapes, which is something I do. The alternative is just spinning the wheel by hand. 

 

 

Thanks for the info everyone.

 

Best,

Chris

[dikman]

I've replaced the handwheels with larger pulleys on a couple of my machines and it works fine, it's a pretty simple way of slowing a machine down. Some don't like it because of the aesthetics , they think it looks "funny", but that is the only negative to doing it. As Bob said you may have to widen the belt slot. I've also fitted a speed reducer AND a larger pulley and it goes pretty slow with that setup!!

[nylonRigging]

19 hours ago, dikman said:

I've replaced the handwheels with larger pulleys on a couple of my machines and it works fine, it's a pretty simple way of slowing a machine down. Some don't like it because of the aesthetics , they think it looks "funny", but that is the only negative to doing it. As Bob said you may have to widen the belt slot. I've also fitted a speed reducer AND a larger pulley and it goes pretty slow with that setup!!

Much More than just aesthetics and what is pleasurable to the eye .  And it's great to have electronic speed selection with Servo drive motor, but there is more to it, than just the end result of RPM desired . I can electronically select my RPM command on motors to turn any speed I want . So why add additional pulley's and belts in-between the 1 tiny pulley drive, and the 1 Large machine handwheel pulley ?
The addition of the pulley reduction in-between the drive motors and machine drive shafts . whether you put it under table or above table for 'aesthetics' appearance .
( I interpret it ) Reason is, It delivered more Lb/ft energy to the Needle for a end result, Using less energy required from drive motor to make that Needle crawl threw the Thick material resistance you give it . 

Question ? . ( For example ) on one of my tables with pulley reduction under-table . You have a 13" Diam.  handwheel with/10" diam. pulley, and with belt, going down to a 1.5"Diam. pulley off the Servo drive with electronic speed select . So why do I need the additional pulley/belt reduction inbetween the drive motor and the machine drive shaft to punch 346 threw 12 pieces of webbing ?
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[Matt S]

2 hours ago, nylonRigging said:

Much More than just aesthetics and what is pleasurable to the eye .  And it's great to have electronic speed selection with Servo drive motor, but there is more to it, than just the end result of RPM desired . I can electronically select my RPM command on motors to turn any speed I want . So why add additional pulley's and belts in-between the 1 tiny pulley drive, and the 1 Large machine handwheel pulley ?
The addition of the pulley reduction in-between the drive motors and machine drive shafts . whether you put it under table or above table for 'aesthetics' appearance .
( I interpret it ) Reason is, It delivered more Lb/ft energy to the Needle for a end result, Using less energy required from drive motor to make that Needle crawl threw the Thick material resistance you give it . 

Question ? . ( For example ) on one of my tables with pulley reduction under-table . You have a 13" Diam.  handwheel with/10" diam. pulley, and with belt, going down to a 1.5"Diam. pulley off the Servo drive with electronic speed select . So why do I need the additional pulley/belt reduction inbetween the drive motor and the machine drive shaft to punch 346 threw 12 pieces of webbing ?

Yep, it's a torque thing. Digital servo motors like we commonly use on sewing machines can spin at a very low or very high speed. (Jack JK513 can go between 200 and 4500RPM for instance.) However the power at 200RPM is very low which isn't very useful for, say, punching a thick needle through stiff leather. Having a step-down pulley or gear transmission between the motor and the machine definitely helps. Clutch motors have a little more torque at low output RPMs than servos because of the mass that's always spinning. (Interestingly stepper motors have the same torque at almost-zero as they do at full throttle. One day I'll get around to putting a direct-drive stepper on a machine.)

How you get that reduction (store boughten pulley reducer, DIY speed reducer, small motor pulley, ridonkulous big pulley fabricobbled in place of the machine's proper balance wheel) the speeds are the same buuuuuut there are other factors at play. Can you get a store-bought reducer and how much will it cost you? Does your motor take common replacement pulleys? How much space under the table do you have? What 

Why are speed-reducer boxes popular? Well they're not all that popular outside of our little niche. I live near London, with probably a dozen industrial sewing machine dealers, quite a few small leather-trade factories and maybe hundreds of individual craftspeople in an hour's drive of me -- and I doubt so many of them I could count on my two hands have heard of such a thing. The nearest dealer I know of that sells them is Sieck in Germany. Most industrial machines sold over here have no more than a 2:1 ratio between machine and motor. Most are closer to 1:1.