Thickness/Torque Capability Difference

[MartelloDesigns]

HI All,

I have a Seiko STH flatbed (The Japanese made equivalent of the Consew RB205/6 etc) , with good servo motor. I added a larger handwheel for a little bit of speed control. 

My question is, what determines how thick/dense of leather a machine can comfortably get through? My machine has no problem with sewing say a 5oz piece to a thinner piece, but if I put 2 5oz together, or anything really thicker than that it basically just binds up and won't get through it. It is not a threading or bobbin binding, it just feels like the motor just doesn't have the 'oomph' to get through that thick stuff. Also, it is not the presser lift or a question of the pieces fitting under the foot- they fit easily. On occasion I can see the motor pulley either just locked up (motor humming like its trying) and sometimes it will be the belt slipping, which is already pretty tight. 

Is it just a question of the motor power? Meaning, I get a new more powerful servo motor and all is well? I know having a dual wheel speed reducer provides additional torque, but is it that much of a difference? I had the Cobra 26 before, and it would just laugh at these thicknesses and go right through. The Seiko is very smooth and sews beautifully on thinner or less dense leathers.

Thank you!

[Wizcrafts]

You answered your own question. Just buy a speed reducer. A 2:1 reducer doubles the punching power at the expense of the top speed. I get my motors and reducers here.

32 minutes ago, MartelloDesigns said:

I know having a dual wheel speed reducer provides additional torque, but is it that much of a difference? I had the Cobra 26 before, and it would just laugh at these thicknesses and go right through.

 

[kgg]

41 minutes ago, MartelloDesigns said:

Is it just a question of the motor power?

I would say the problem lies in your speed reduction. I am going to assume you have a 2" pulley on your motor, you increased the diameter of the hand-wheel from 4 to 6 inches and with a motor speed of 100 rpm's.

1) The original speed of the hand-wheel would have been 50 rpm's. Changing the hand-wheel to 6 inches would increase the torque and reduced the hand-wheel speed to 33.3 rpm's.

2) Installing a standard intermediate speed reducer (6" large pulley with a 2" small pulley) between the machines

       i) original 4" hand-wheel and the 2" motor pulley you would increase the torque and further reduce the hand-wheel speed to reduce the 17 rpm's

      ii) if you keep the larger size diameter hand-wheel (6") you already installed you would again increase the torque and further reduce the hand-wheel speed to reduce the 11 rpm's 

I think the problem of the belt slipping maybe poor sidewall contact or belt type not matching both pulley profiles. Other things could be incorrect size of hand-wheel pulley, glazed motor pulley, incorrect distance between hand-wheel and motor pulley and / or undersized motor or a bad motor. 

I think installing a intermediate speed reducer would probably solve your problem as long as the proper belts and pulley distances are done.

When sewing are you just putting the doubled leather under the presser foot and going for it or are you hand-wheeling the needle down through both layers to let the machine have a run at it?

kgg

 

[Constabulary]

I have speed reducers on all my machine stands, most 3:1 ratio. But a more powerful motor with 750W for sure will make a fifference as  well.

Speed reducer can be DIY as well - some pictures from what was posted here in the forum:

https://www.google.com/search?q=DIY+speed+reducer+site%3Aleatherworker.net%2Fforum&tbm=isch&ved=2ahUKEwjLq5a_8br7AhXROewKHfAhCeMQ2-cCegQIABAA&oq=DIY+speed+reducer+site%3Aleatherworker.net%2Fforum&gs_lcp=CgNpbWcQA1DKDVi3GGDWJmgAcAB4AIABuAGIAd8EkgEDMS40mAEAoAEBqgELZ3dzLXdpei1pbWfAAQE&sclient=img&ei=DiJ5Y8vsDdHzsAfww6SYDg&bih=878&biw=1680

Edited November 19, 2022 by Constabulary

[MartelloDesigns]

Thank you guys for the helpful feedback!

*I have tried both hand cranking into the leather and letting the motor try and pick up from there, and just letting the machine try it from the start. 

I'm not sure about pulley distances, and what the correct distances would be. I just make it work, lol.

I will get the speed reducer. Expensive, but that Box Style looks perfect for my application. 

Thanks again!

Rick

 

[kgg]

10 minutes ago, MartelloDesigns said:

I'm not sure about pulley distances, and what the correct distances would be.

Here is a good staring place to understand pulley reduction for single or multiple pulleys: www.blocklayer.com/pulley-belteng

kgg

 

[327fed]

If your belt has gotten slippery or your pulleys glazed wth oxidation, use some Bon Ami (or Ajax powder) on the pulleys and run them a little. Will take the glaze off. 

[Wizcrafts]

2 hours ago, MartelloDesigns said:

I'm not sure about pulley distances, and what the correct distances would be. I just make it work, lol.

I will get the speed reducer. Expensive, but that Box Style looks perfect for my application. 

If you call Toledo Industrial Sewing Machines (866-362-7397), they will ask for your current v-belt length to your motor and its pulley size. Then they will know what belts to include with the reducer.

 

[CowboyBob]

19 hours ago, Wizcrafts said:

If you call Toledo Industrial Sewing Machines (866-362-7397), they will ask for your current v-belt length to your motor and its pulley size. Then they will know what belts to include with the reducer.

 

I sure WISHED we could but there's no way to know what belt to send,they need to install the reducer,measure the length needed & buy them locally @ an auto parts or lawnmower shop.

[327fed]

Here is an online calculator when you get the reducer installed. Need the center to center and the diameter of the 2 pulleys. You also have some adjustment in the system. However, I still made 3 parts store trips to match mine. It will get you in the ballpark. Buy a couple, return one. Parts guy asked me if that was the last swap. 

https://sudenga.com/resources/figuring-belt-lengths-and-distance-between-pulleys/

Edited November 22, 2022 by 327fed