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.

[mikesc]

fabricobbled

A perfectly cromulent word.. :)

Edited March 16, 2019 by mikesc

[dikman]

6 hours ago, nylonRigging said:

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 ?
.
 

Simple answer is you don't need one. Don't forget that most machines that people are fitting reducers to only have a 4" handwheel, NOT the 13"/10" that you have.

"fabricobble" - good one, a word that is very applicable to my various efforts. Along with the classic "fettle".

[luxuryluke]

In my limited view the makeup of the pulleys and belts is also important. Slick pulleys and worn out belts is a potential point to consider.

My machine has like a 3.5” handwheel. Installed the consew 3000 servo yesterday with the 75mm stock pulley. The 45mm pulley just arrived. Both pulleys seem to be made of rough cast aluminum so they’re sticky. Also, the SR2 “3/6/9” speed reducer arrives imminently. This servo has the lowest speed setting of 200rpm. I’m fabricobbling my own urethane round belts to fit. This topic is interesting to me but I haven’t seen how slow I’ll be able to sew yet. I’ll find out in a few days. Will report. 

Edited March 17, 2019 by luxuryluke

[rchaven]

I just got my new industrial walking foot machine. It's a New Tech GC-0303 which is a clone to the Juki DU-1181N. It came with a brushless servo motor with a separate control box. Out of the box the machine sews to fast for me at the lowest setting of the control box. I set it at "2" but when the petal is pressed the speed on the box says 500. So it's off by 300 rpm. When set to 10-15 or higher at lowest speed again 500 to fastest 1000-1500 or higher depending on what speed is set. I ordered a smaller 45mm wheel for the motor. Installed the smaller pulley with better slower speeds at the needle but the box still only goes to 500 even when speed is set at 2-4. Still not the stitch by stitch control I would like to have. So after looking at all the different variants of the SR2 speed reducer, Iand looking at $150-180 to my door, i decided to fabricate my own reducer. I did hours of internet research trying to find ideas for a simple inexpensive reducer. I decided to build my own and after collecting all the materials I got it built, installed and am very happy with the results. I now set my control box at 35 and sew as slow as I like and speed up to what ever speed I need, or can handle. Only a couple of things to mention, first I can no longer rock my machine back for access underneath. Also my needle positioning sensor no longer seems to work correctly. I have tried re adjusting it many times for both needle up and needle down positions with no luck. Thankfully it's no longer needed as I can easily control needle position with treadle. I would have loved to just have swapped out the motor pulley and hand wheel to achieve this option, however I dont think I would have achieved the same amount of needle torque. Sorry if my post is rather long. There isn't much good info out there about industrial walking foot machines and leather sewing in the mainstream internet. I suppose if I'd have found this site first last week my life may have been a bit easier.

[katit]

19 minutes ago, rchaven said:

 I would have loved to just have swapped out the motor pulley and hand wheel to achieve this option, however I dont think I would have achieved the same amount of needle torque.

Your reducer looks approximately ~ 1:6. To do same with 2 pulleys (top and bottom) you roughly need:

a. Bottom pulley 75 -> 45mm so it's about .8 reduction

b. In order to achieve same reduction as you have with a box you need to reduce by additional x5.2 on top. So, it means from about 6in pulley to 30in in diameter.

 

This is what would it take to achieve same reduction/torque which is not possible because you don't have 15 inches from top shaft to your table.

[Matt S]

I've run machines on 1:6 ratio before. Running at lowest speed is certainly better (especially on lower-quality servos) but the max speed is very limited. Most servos top out at 4500RPM, which at 1:6 works out to 750SPM. This is close to the top speed of certain heavier machines (Juki 441 for instance) and fair enough in those circumstances. The massive increase in power at low RPMs would probably be worth it alone, especially with big needles. However for an upholstery-weight machine that's losing a lot of speed -- a lot of machines can cope with more than 1,000SPM and many more than 2,000. Not everyone can or wants to make use of this capability but for those of us that do it's a real time saver. Imagine sewing a sofa, a boat cover or a couple dozen 6ft dog leads at 750SPM!

[dikman]

rchaven, nice job, yet another variation on building a speed reducer. There is no doubt that using a speed reducer will give slower speeds than just replacing the handwheel with a larger pulley but it just depends on what a person wants and which is the easiest (cheapest?) method to use. One of mine is down to 1 stitch every 2.5 seconds, a bit extreme perhaps, but..........

Oh, and because you're new here you obviously won't be aware but there have been a few posts about speed reducers and needle positioners and basically they don't work well together!

Edited March 19, 2019 by dikman

[luxuryluke]

There's no way I have the equipment in the garage to come up with something that impressive, @rchaven. Nice job!

Spokane! Another Washingtonian. Welcome to the forum!

[luxuryluke]

Speaking of pulleys and reducers, I prepared a urethane belt to fit with a torch and razor blade. It worked out well and it grabs the small 45mm pulley rather nicely: