Well, I took the plunge and started working to put a cab on my JD 420. We've had a couple of heavy snowfalls in the past week, and I put a lot of seat time in Ol' Green--including several hours while the white stuff was still coming down--ended up with soggy pants from the waist down, not to mention my Walls jacket and stocking cap.
I love my Bolens HT23 with it's front end loader--makes short work of clearing out driveways gutters after the city plow buries them. But, for sheer ease of handling and convenience, the power steering and short turning radius of the JD can't be beat--guess I'm going to have to hang on to both of these sweethearts. I've set the JD up with a rear blade and front snowblower. We have a lot of "golden age" people in our neighborhood, so I and a couple other neighbors work to keep their driveways and sidewalks clean. I pull the snow out of the drive way, then push it along the curb. The snowblower clears the entire sidewalk in one pass. Anyway...
I've put off building my own cab as I couldn't figure how to make sure it fit the contours of the fenders, hood, etc.
Then it hit me--just take a picture of the machine dead on from the sides, front and rear, then take measurements.
The picture taking part was easy, but taking measurements was slowwww.
Then I had another thought (hmmm, two in a week, I'm really on a roll!!)
I can import .pdf files into CAD, and the CAD program would allow me to make adjustments to the design. I use Draft Sight by Dassault Systeme--makers of Solid Works 3D CAD. It's an AutoCAD clone. It's totally free, and is very powerful. If you're looking for a good 2-D CAD program, I strongly recommend it!!
Anyway, even though the imported .pdf file is essentially just a picture--you can't adjust any of the picture's features, etc., you can "trace" over the picture with CAD commands such as line, circle, arc, etc. You then move the .pdf file and the features you've drawn are a part of the CAD file and can be added to, edited, etc.
What I did was to take several pictures of the tractor--putting the camera as perpindicular to the axis of the tractor as I could, and also parallel to the ground. It didn't turn out perfectly, but I got real close.
I then used MS Office Picture Manager to edit the picture and get as much contrast as possible--especially on the fenders, hood, floorboards, and other areas of the tractor that would interface with the cab.
I knew the wheelbase of the tractor (52"), so the areas that needed really precise hole placement was the center of the front and rear wheels.
I then turned the picture over and marked each hole with a drafting pencil (H lead) then drew lines to the holes, using a straight edge. I marked a "+" at the center of the wheels.
This obviously creates a mirror image of the picture, but you can change it back later using the CAD program.
I then scanned my penciled drawing into a pdf file, then imported it into my CAD file.
The picture was quite large, but I first traced all the lines and located the centers of the wheels using CAD commands, then moved the pdf "overlay" to reveal the CAD outline. I then used the program SCALE function to scale the drawing down so that the distance between the points for the wheelbase was 52".
I then used CAD to draw the cab onto the drawing. I used 4 different layers to do so-- 1 for the tractor outline, 1 for the Cab outline, 1 for construction lines, and 1 for dimensions. This allows to me to show all, or various parts of the drawing--for example, I turned off the Construction Line layer when I exported the CAD file to .pdf (JD 420 SIDE.pdf).
Here is the CAD drawing of my cab for the JD 420.
I have drawn the outline and major dimensions for the left side of the cab, and the back. I also put an arc segment into the drawing to show the sweep of the hood when it is opened, as I don't want it to interfere with the front of the cab. It's not complete, yet, but you can get an idea of the basic outline of the cab and major dimensions.
1. Angling the front window inward from the top to help snow and rain run off easier.
I originally planned to make the cab out of 1/2" exterior grade plywood, primed and painted with high quality exterior paint. We have a local company (Kwals) that has an excellent satin finish exterior paint for $35 a gallon- a gallon of primer costs about the same. I planned to use 2x2 wood reinforcement on corners, etc. A gallon of each will be more than enough to paint the cab.
As for the windshield...
This has been a long post, and I still haven't covered everything--mainly because this is a far as I've got, but I will keep you posted as work progresses.
Edited by Utah Smitty, December 26, 2013 - 12:49 AM.