Difference between using a Larger Pulley vs. Speed reducer?

[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: