×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

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!
  • Students Click Here

*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

Jobs

Excessive gear ratios in fan belts

Excessive gear ratios in fan belts

Excessive gear ratios in fan belts

(OP)
What does excessive gear ratios mean in belt fans? Many consultants say to avoid them and use direct drive. How do I calculate the savings if changing the pulley to direct drive

RE: Excessive gear ratios in fan belts

It means what it says.  There is a practical upper limit to the speed reduction that can be achieved by V-belt drive. As you increase the size of the larger ( usually driveN ) sheave, the angle of contact, or wrap, on the smaller sheave decreases, unless you ibcrease the centre distances.  This can lead to higher slip and less efficiency.  
Yes , direct drive is more efficent,  but your load has to operate at motor speed.  If you need speed reduction, then you can use a gear reducer, but you have to get the ratio correct. V belt speed reduction is typically less expensive than a gear box, and has the advantage that the ratio can be easily and inexpensively adjusted by changing one sheave.
There are numerous other factors to consider as well including but not limited to ambient conditions ( hot / dirty ) horse power, maintenance access, light or severe duty service, etc.  
Another option is using a timing or synchronous belt, where the cogged belt drives a toothed sheave.   
However there are literally  millions of V belt drives out there working just fine ( virtually every automobile.)
Your local bearing house will be able to help you with your application.

RE: Excessive gear ratios in fan belts

Quote:

...but your load has to operate at motor speed...

...And motor speed is easily made continuously variable, precisely and over a very broad range. The caveat is that the torque multiplication you achieve with speed reduction using a gearbox or belt drive  does not happen with a variable speed motor.
 

----------------------------------
  Sometimes I only open my mouth to swap feet...

RE: Excessive gear ratios in fan belts

If you must use a belt there are poly vee belts that can use a very small motor pulley dia efficiently.

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!


Resources