Using Librecad to analize bike geometry

Hello Everyone!

im new here, and i wanted to know how can i do this.

the basic idea is using a PNG image of the bike itself, and draw some lines representing elements of the bike geometry, by example, seatube lengt, i draw i line between the center of the crank and the top of the seatube.

and after doiung that, inserting some know values in my models so that it gives me the exact lengt and values of all the lines i draw.

following with the example lets say that i drew a line to know the effective toptube length, from the center of the saddle to the top of the stem, but i dont really know what is the exact dimension of this, but since i know the dimension of the seatube, i cant use it to determine everyting else.
this can also help me find out the values of head angle, stack, reach, and all the other measurements related to bike geometry just by using an image of the bike and a know value.

i know there must be a way to do this but i couldnt figure it out by myself so i opted to ask for help here.

Thanks in advance!

Hi,

this is surely possible. A quick search showed me these threads:
https://forum.librecad.org/Can-I-define-distances-between-points-in-Librecad-2-1-3-td5719156.html#a5719159
https://forum.librecad.org/Scaling-imported-images-td5711385.html#a5711554
https://forum.librecad.org/image-reference-td5718665.html

They handle similar issues and show solutions. You may find more with forum search.

Basically import the image.
Draw a line of known length on the image.
Measure the drawn line length.
Use measured length and real world length to scale the image.

Put the image on a separate layer, that you can disable it, because there is an issue that you can't select entities which are on the image.

Armin

It would be worth running through https://dokuwiki.librecad.org/doku.php/tutorial:carport

Hi, in plus of what are already replied, I want to put emphasy on taking the image with the less distortion possible.
Near shots put lot of distortion, which is null at the center and high at the edges, the ideal are shots taken from as far as possible, maybe with a teleobjective
Also the bike should be perfectly perpendicular to the camera sight as possible.

Other than that, as explained in the other posts, it is just a matter of inserting the image and drawing, scaling and measuring over it.

A late reply on this but one way of getting an image taken parallel to the plane of the bike frame is to place some sort of coarse  "grid" object against the bike (something with horizontal and vertical lines) and rectifying the image, either using the rear screen guidelines of a digital camera or via software.

Hugin panoramic stitching software (free!) can rectify an image on parallel lines.  There is a tutorial on the Hugin website on how to do this.  It can also be used to rectify an image of a building facade, which can be drawn over in Librecad to create an elevation drawing.

One thing to watch with drawing over rectfied images - objects that are not on the plane of rectification will be either at too small or too large a scale, and not in the correct position.  Therefore care has to be taken with this approach.

Hallo,

eine sehr gute Möglichkeit zur Analyse und Berechnung der Fahrradgeometrie bietet folgende seite, die ich auch selbst verwende, da ich selbst Rahmengeometrien berechne bzw. konstruiere.

https://www.bikecad.ca/

Hier kann man sich hier mit Passwort registrieren und die Software als Webanwendung kostenlos nutzen. Man kann alle notwendigen Geometrien berechnen und seine Ergebnisse speichern. BikeCad Web finde ich ausreichend und sehr praktisch.

Viele Grüße
Peter G.