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I just downloaded Turn117.lsp and ran the lisp a few times with my WB67 block.  However, each time I run the lisp, the program only draws the path of the midpoint of the rear axle.

I watched the YouTube video on how to run the program and saw that the lisp is supposed to generate a whole lot more data than just the one axle path.

Any ideas on how to make the other lines appear?  (I did check to make sure all the layers are thawed and on)



I'm assuming you're referring to Turn.lsp by Tom Haws. The routine can be downloaded from his website here:

also here:

and from the AutoCAD Wiki here:

If you haven't visited the Wiki, I suggest you do so as that is where the most current updates and information about the routine can be found.

To use:
1. Appload the routine.
2. Create a layer which will be the path of the left front wheel. Set that layer as current.
3. Look up the minimum turning radius for the AASHTO vehicle you are modeling in AASHTO's Green Book.
4. Draw a polyline representing the path of the left front wheel making certain that your turning radius is greater than or equal to the minimum turning radius as listed by AASHTO. Your turning path will need to be clockwise. There is a way to model counterclockwise but that is a litlle bit more involved.
5. Insert the desired vehicle block. These are also available from the websites listed above. I recommend downloading from the Wiki.
6. Align the vehicle block with the polyline. (The vehicle block needs to be at the same angle as the starting portion of the polyline. Make sure the starting portion of the polyline is straight for a good distance before starting your curve. Make sure all sections of the polyline are tangent.) You'll see a little circle in the center of the left front wheel of the block. Make sure this little circle is on the starting endpoint of the polyline. Be certain that the path of the left front wheel is a POLYLINE and not line and arc segments.
7. Type "turn" on the command line (no quotes) to run the routine.
8. At the prompt, enter "g" for generated vehicle.
9. Select the vehicle block.
10. Select the starting endpoint of the polyline.
11. Accept the defaults for plotting the path and vehicles along the path.

Also, Turn.lsp does not generate a path along the center of any of the axles. What you were most likely seeing was the path of the trailer hitch.

The routine can be tricky for some when first learning to use it but you'll get it. Just stick with it. Also, my instructions above are from memory as I'm not currently at work, but I'm fairly certain they are correct. I'll check tomorrow and if anything is different I'll post an update.

Good Luck!


Addendum to the above. I ran the routine at work today and thought I'd add an additional note for clarity.

After step 8 above, where you enter "g" for generated vehicle, another promp will appear. Just hit "Enter" at this prompt. This will enter the default which reads <select previously generated vehicle>. Then you can proceed with steps 9 and 10 above.

Have fun! It's a great Lisp routine!

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