Contact US

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Pulley system for cardboard pulp shredder/mixer --- REPOST

Pulley system for cardboard pulp shredder/mixer --- REPOST

Pulley system for cardboard pulp shredder/mixer --- REPOST

Hi everybody, sorry for reposting this message again, for some reason it has been deleted, very sorry if i'm breaking any rules, I just desperately need help on that one.

I am building a machine for a friend who works with cardboard pulp, he is also a performance artist and would like a machine where 2 or 3 performers can activate the machine by hand with pulleys and wheels, and shred the pieces of cardboard that are soaking in a container filled with water. There is 4 pulleys in total and the last driven pulley is attached to a shaft with blades on it, this whole assembly constitutes the shredding mechanism.

Currently the artist is shredding the cardboard with a hand drill on which is attached some very small DIY blades. The drill runs for about 30 minutes at 8000 RPM and he manages to get the consistency he wants.
In my idea of his machine 2 performers would spin a horizontal wheel bar of 2 meter(6.56168 feet) diameter at about 5 to 15 RPM and that wheel bar is attached to a pulley which is driving a 1:5 pulley, that 1:5 pulley is attached to a 1:1 pulley which drives another 1:5 pulley. Since the blade that will be made for this machine is about 12 times bigger than the original blade he was using, I am not sure that we need as many RPM as the drill gives. But I am not very sure either. Anyhow, I thought that just a little less RPM than the drill would do the trick, maybe 5000 if that is even doable. All pulleys will be made of wood and the wheel bar will be in steel tubes.

However it is my very first time working with pulleys and ratio and I lack experience in safety, in feasibility and in physics.

I do not know how to obtain the RPM I want for the rotating blade while having a decent of size for the whole machine. I have attached some pictures that give you guys dimensions and other drawings to see the machine better. Obviously the pulleys will not be floating, I just havent thought about the structure yet, I wanted to have your opinion first.

I am wondering if such a system will output the results I want, if it is durable and safe.

Thank you very much for your help !


RE: Pulley system for cardboard pulp shredder/mixer --- REPOST

the drawing is not readable when it is zoomed up. can you repost it as an attachment but make the text dimensions larger thus easier to read.
I don't know why the admins deleted the post, I am guessing no one is going risk and say this is safe. and may only make suggestions, and you assume the risk if it is safe.
this requires complex design knowledge, with many factors, such as a free body diagram, the s/n curves of the material. stress and strain, and will work, with a margin of safety. and so on.
if you agree to assume all risk then we can start from there. what is the Horse power of the motor, RPM, and the torque requirement of the input pulley.
what are the required rpm, velocity. and torque of the blades. my suggestion in real life hire an engineer to help with all my comments.
also there are off the shelf components on the internet which would reduce cost instead of custom manufactured parts.

RE: Pulley system for cardboard pulp shredder/mixer --- REPOST

Thanks for your answer and feedback mfgenggear!

In the end I managed to make it work and the performance was a success!

I'll post a video when the official reel is published.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members! Already a Member? Login


Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close