Pantograph drawing: need help pls - diyAudio
Go Back   Home > Forums > Design & Build > Equipment & Tools

Equipment & Tools From test equipment to hand tools

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 15th December 2009, 03:42 PM   #1
diyAudio Member
 
Steerpike's Avatar
 
Join Date: Jan 2006
Location: Johannesburg, South Africa
Default Pantograph drawing: need help pls

Does anyone know anything about pantographs?

I made a rudimentary 'test' setup from strips of plastic an wood, before I go all out on making a metal one, but my prototype doesn't work!

I want a scaling factor of around 10:1, i.e., the drawing must be 10% of the stencil size, so that any errors tracing the stencil are almost invisible on the drawing. I made (A+B)=50cm (about 15 inches).

I figured the scaling factor would be
A/(A+B) = C/(C+D)
and to maintain a 'square' aspect ratio A=C and B=D.
(my diagram is a little distorted, but tha actual machine is accurately measured)

But I'm getting some very trippy drawings that look like Salvadore Dali's. So my trigonometry is wrong!

Does anyone know the correct trigonometry for this thing and what I did wrong?
Here's a neat online illutration of operation, but they don't give any info on how to calculate the arm lengths:

*** pantograph Java applet***
Attached Images
File Type: gif panto..gif (7.6 KB, 63 views)
__________________
Steerpike's Toybox

Last edited by Steerpike; 15th December 2009 at 03:44 PM.
  Reply With Quote
Old 15th December 2009, 08:07 PM   #2
diyAudio Member
 
Steerpike's Avatar
 
Join Date: Jan 2006
Location: Johannesburg, South Africa
I've figured out WHY I'm getting distorted drawings - it's because the pen is slightly offset from the fulcrum.
But I still need assistance to figure out a way to compensate for this. It's physically impossible to place the pen right at the fulcrum - unless it involves a very elabrate bearing with a hole in the centre.
__________________
Steerpike's Toybox
  Reply With Quote
Old 15th December 2009, 08:16 PM   #3
diyAudio Member
 
neutron7's Avatar
 
Join Date: Dec 2003
Location: Toronto Canada
just make an ofset for the stylus which is 10 times (or whatever your scaling is) as much as the pen is offset and in the same direction., in your case D would have 10x the distance between the pen and its closest pivot added to it.
  Reply With Quote
Old 15th December 2009, 08:28 PM   #4
Account disabled at member's request
 
MJL21193's Avatar
 
Join Date: Mar 2007
Looks to me like dim "C" should be equal to dim "B", forming a square in other words.

Also, moving the pen to here will help:

panto_.gif

Last edited by MJL21193; 15th December 2009 at 08:38 PM.
  Reply With Quote
Old 15th December 2009, 08:43 PM   #5
diyAudio Member
 
Steerpike's Avatar
 
Join Date: Jan 2006
Location: Johannesburg, South Africa
Quote:
Originally Posted by neutron7 View Post
just make an ofset for the stylus which is 10 times (or whatever your scaling is) as much as the pen is offset
That's what I thought at first; but it doesn't work. Hard to explain what happens in words... the offset required changes as the arm angles change. A fixed offset on the stylus doesn't correct for that.

BUT, I have found an alternative design, that I will try tomorrow. How to set the scaling of this arrangement is also a mystery for now - I'll have to revise some geometry!
Attached Images
File Type: gif Panto1.gif (5.5 KB, 48 views)
__________________
Steerpike's Toybox
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
PCB Drawing for STK4231V ? thoronx Chip Amps 1 26th June 2008 08:04 PM
drawing freeware??? aardvarkash10 Full Range 12 15th May 2008 12:33 PM
My first GC PCB drawing... flying Chip Amps 8 14th January 2005 06:24 AM
CAD Drawing Doug Everything Else 8 8th October 2003 02:52 PM
Ariel 6 drawing kid Multi-Way 8 1st May 2002 02:30 PM


New To Site? Need Help?

All times are GMT. The time now is 05:07 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2