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Jd 420 Cab Project

jd 420 jd420 cab home made cab home made gt cab cab

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#1 Utah Smitty OFFLINE  

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Posted December 26, 2013 - 12:21 AM

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.

 

JD420 RH EDITED.jpg JD420 RR - Copy.jpg
 

At first I thought of placing a blank sheet over the picture and tracing the parts I needed--however, this didn't work very well as I couldn't get enough precision.
 
I then thought of using a large pin to put a hole through the paper from the front to define lines, arcs, radii, etc. Basic geometry teaches that a line is the shortest distance between two points, so only two holes are needed to draw straight lines. For curves I made a series of holes close together that traced the profile.

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.

 

JD 420 LH LINE DWG.JPG JD 420 RR LINE DWG.JPG

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.

 

JD 420 LINE DWG.JPG

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.
 

Some of the features that I included on the cab include:

1. Angling the front window inward from the top to help snow and rain run off easier.
 
2. Angling the back as well to make allowance for the angle of the seat back.
 
3. Beveling the lower portion of the back wall to insure that the rear mounted JD fuel filler is outside of the cab. (not yet shown in the drawing).
 
4. Angling the lower front portion of the cab to enclose the foot rests--making enough allowance for brake pedal travel.

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.
 
Using plywood has several advantages-
 
1. It will go together faster than building a steel frame and attaching a metal or fabric skin, as the plywood is a major structural element.
 
2. Door and window openings can be cut from the sheets of plywood, reducing need for metal framing.  If you're careful, you can cut out the doors, then use the cut out pieces for the actual doors. You can install a narrow piece of wood or metal around the opening on the inside to lap over into the cut out area and provide a stop and basic seal.  A little open cell foam glued or stapled to it will be more weather proof.
 
3. Wood can be worked easily with basic tools, and repaired easily too.  Exterior grade glue can be used to clamp the pieces together using screws to hold the pieces. The screw heads can be countersunk slightly, then covered over with a good quality wood filler.
 
The disadvantages of using wood are:
 
1. It's not as weather resistant as steel or plastic--it will need to be painted every 3 or 4 years to keep from rotting.
 
2. Although I don't know this for certain, I suspect that a solid wood cab will be heavier than one made from steel tubing with sheet metal covering.
 
I haven't yet settled on whether to make a steel frame, or use the wood.  Time is a concern--I'm off until January 6th, and we're supposed to have 7 straight days of above freezing temperatures during the day--I want to be finished by then.
 
I have the steel (2" wide channel), a cutting torch, cutoff saw, and a welder, but nothing to knock the mill scale off with other than a disk grinder or wire wheel-- Looks like it would take a lot of time to clean off the scale, then prime and paint the steel, plus I won't be able to paint it indoors due to fumes, and it won't really be warm enough outside.... looks like the wood route is going to win for now.

As for the windshield...
 
I have some large pieces of polycarbonate in the form of camper windows that I can use for the rear and sides of the cab.  I intend to use glass for the front so I can use a windshield wiper.
 
Your only real choices for glass are tempered, or safety (laminated) glass.  Tempered glass can't be cut after tempering without use of a tempering oven to anneal it, so I couldn't re-purpose a glass table, or the doors to a stereo, etc.  I can buy Tempered glass--a 1/4" x 36 x 24 sheet is about $150 delivered. On the other hand, I can get the same sized piece in laminated glass from a local glass shop for about $75. Safety glass has the added benefit of helping to deaden sound--Being in the cab with a 20 hp Onan at max speed is like being inside a kettle drum while the Orchestra plays "The Charge of the Light Brigade". You can also add foam, carpeting etc to the inside to help cut down the noise level.
 
Many people use rubber molding to install windows in their cabs.  However, there are some excellent glass adhesives available nowadays that makes the job much simpler.  Regardless of whether I build a wood or metal cab, I would make a front window frame from metal in order to glue the windshield to the surface of it.  It would also have provisions for a hinge so I can open it for ventilation, etc.
 

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.

 

Regards,

 

Smitty


Edited by Utah Smitty, December 26, 2013 - 12:49 AM.

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#2 boyscout862 ONLINE  

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Posted December 26, 2013 - 05:58 AM

Sounds like a good project. You may want to reconsider the 1/2" plywood. 3/8" may be strong enough. I have an old canvass cab. Its frame is just 3/8" rods. If I ever build a GT cab, I'll probably use 1/2" EMT. I've got the bender and welder so it would be easy. Stay warm. Good Luck, Rick


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#3 Alc ONLINE  

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Posted December 26, 2013 - 06:26 AM

I'm not sure if you would want to use this material for the glass or hard plastic , I bought the 22mm vinyl  for my mini greenhouse I made a few years ago , it sits on the southside of our house and it still looks good . I warmed it up before stalping it to a wood frame so when it cooled it was  tight .

 

http://www.farmtek.c...s;pg105129.html


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#4 JDBrian OFFLINE  

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Posted December 26, 2013 - 08:01 AM

Smitty, this sounds like a great project. I would be worried about the weight of a wood cab. You could estimate the materials and calculate the rough weight. Heres a link to a company that makes a very nice cab for all kinds of small tractors. The features and construction details may give you some ideas.http://www.originalc...roducts_htc.htm


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#5 Arti OFFLINE  

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Posted December 26, 2013 - 09:52 AM

Looks like a great start on the project.. I did something similar a few years ago and used 2x2 's for framing, I cut a grove in the 2x2 stock a little over 1/4 inch wide and 1/2 inch deep

Then used 1/4 inch exterior plywood as the panel material glued into the grove. This makes a light weight strong panel, For a finish I used exterior Enamel that lasted for several years.

For the side and back windows I used the plastic window material that Alc was suggesting. I was very pleased with it.

I'm not sure if you are planning on leaving the cab on however these tend to get heavy very quickly and can be a handful to put on and take off so weight is a consideration.

You could make a frame out of 1 by 2 wood and glue a skin of 1/4 inch paneling on both sides that would be somewhat more insulated and super strong.

I'm sure you will enjoy the cab when it is finished.
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#6 Utah Smitty OFFLINE  

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Posted December 26, 2013 - 11:04 AM

Sounds like a good project. You may want to reconsider the 1/2" plywood. 3/8" may be strong enough. I have an old canvass cab. Its frame is just 3/8" rods. If I ever build a GT cab, I'll probably use 1/2" EMT. I've got the bender and welder so it would be easy. Stay warm. Good Luck, Rick


Thanks, I'll check out the 3/8" plywood--it will make things lighter.

 

I thought of using EMT as well--I have a manual conduit bender and a welder... my reasons for not using it are:

1. it would be harder to drill straight holes through the tubing to attach hinges, front window, etc.
2. thefe would be added prep time making the fish mouths, copes, and gussets needed to ensure strong weld joints.
3. You'd have to take time to clean the galvanizing off the areas where you'll weld--otherwise it messes up your weld, not to mention the hazard of the zinc burning and breathing poisonous fumes.

FWIW,

Smitty


Edited by Utah Smitty, December 26, 2013 - 11:25 AM.

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#7 Utah Smitty OFFLINE  

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Posted December 26, 2013 - 11:31 AM

I'm not sure if you would want to use this material for the glass or hard plastic , I bought the 22mm vinyl  for my mini greenhouse I made a few years ago , it sits on the southside of our house and it still looks good . I warmed it up before stalping it to a wood frame so when it cooled it was  tight .

 

http://www.farmtek.c...s;pg105129.html

 

Thanks.  I bought something like that here locally, though I'm not sure if it's as thick.  I planned to use it for side and rear windows if I ended up making a soft-sided cab. 

 

It says it's vinyl--makes me wonder if I can glue it with PVC cement to the vinyl billboard tarp I bought for my shed project??? That would simplify making windows...

 

Smitty



#8 Utah Smitty OFFLINE  

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Posted December 26, 2013 - 11:33 AM

Looks like a great start on the project.. I did something similar a few years ago and used 2x2 's for framing, I cut a grove in the 2x2 stock a little over 1/4 inch wide and 1/2 inch deep

Then used 1/4 inch exterior plywood as the panel material glued into the grove. This makes a light weight strong panel, For a finish I used exterior Enamel that lasted for several years.

For the side and back windows I used the plastic window material that Alc was suggesting. I was very pleased with it.

I'm not sure if you are planning on leaving the cab on however these tend to get heavy very quickly and can be a handful to put on and take off so weight is a consideration.

You could make a frame out of 1 by 2 wood and glue a skin of 1/4 inch paneling on both sides that would be somewhat more insulated and super strong.

I'm sure you will enjoy the cab when it is finished.

 

Thanks.  I hadn't thought of cutting a groove in the 2x2's, but that would seal the cut edges of the plywood... I may just try it.

 

Smitty



#9 hdg4400 OFFLINE  

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Posted December 26, 2013 - 12:31 PM

Utah Smitty:

Sounds like quite a project, and probably beyond anything I could do. Though if I tried it for my 318, I would probably build it out of wood with separate panels I could bolt together. Hopefully that would ease installing and removing it.
I had a metal cab for my JD 140, which probably would have fit my 318. It had canvas doors with plexiglass windows, and canvas that went around the front to keep snow out. The back window was also plexiglass but the front was glass and it had a hand powered windshield wiper. The whole thing attached to the fenders and the foot rests.

I found that just my body heat kept me warm in it, sometimes too warm. Also, my breath would fog up the front window. I also put a 12v floodlight (from Northern) on one fender, it better see when backing up.

I'd be worried about gluing the front window with all the vibration. Mine was in a rubber gasket. The back window was actually a panel that was secured with clips and could be removed quite easily.

On the 140, I had to make a little door at the base of the rear panel to be able check and add transmission fluid.

I don't think I have any pictures of it on or off the tractor, but will check and post them if found.

Again, sounds like quite a project, and looking forward to progress reports and pictures.

Harlan
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#10 Utah Smitty OFFLINE  

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Posted January 03, 2014 - 09:37 PM

Well, things have moved along on the cab, but came to a screeching halt yesterday.  A guy I know asked me to sell the tractor to him 3 months ago.  I told him I didn't want to sell it, but gave him a price. When I followed up with him, he still hadn't raised the money, but was trying to get a loan, borrow from family, etc. 

 

I hadn't heard from him for a while so I texted him and said unless I heard from him immediately I was going to put a cab on the tractor and just keep it.  Two days later he texted me and asked if I had finished the cab for "his" tractor.  I think he was just joking, but I was a little irritated as I had started cutting out the sides and back when I didn't hear from him, and couldn't use them on anything else, and wasn't going to give it to him.  So I told him if he wanted the tractor he needed to pay for it, and for the cab materials, and gave him a deadline.

 

This morning he said he was coming to get it Saturday morning and would have cash in hand... He asked me what I'd charge him to finish the cab, but I told him I didn't have time to do it since I start work again Monday, and need to get a cab on my Bolens HT23...

 

Anyway, long story short... I quit working on the cab, and, there's a strong chance he'll be here tomorrow to get the tractor, loader, etc. I hate to see Ol' Green go <sniff> <sniff>--she was a good working tractor--I was spoiled by the power steering and sharp turning radius, and the dual hydraulics in the front, etc.  My only real complaint is the hydro is lever controlled, instead of foot controlled... wasn't a problem when operating the snow blower or back blade, but I needed an extra hand when I was operating the loader....

 

So anyway, I can now focus my attention on the HT23 and get the PS installed, a cab, etc.  Still may want to find another JD at some point, though...

 

Smitty


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#11 twostep OFFLINE  

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Posted January 07, 2014 - 12:09 AM

so is this gone now?



#12 Utah Smitty OFFLINE  

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Posted January 07, 2014 - 05:55 AM

so is this gone now?


Yep... He came and got Ol'Green last Saturday... wish I hadn't sold her after I saw how well she handled clearing snow. I went over to move my Bolens HT23 and It almos seemed like she was sad, too.

Smitty
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#13 IamSherwood OFFLINE  

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Posted January 07, 2014 - 06:47 AM

Darn, I was getting right into reading this build, and now it's dead.

I hope you build one for the Ht23. Yes?

I'm guessing you did well selling that 430. Congrats. You'll find another, and

have a good start already on a cab for it.


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#14 Utah Smitty OFFLINE  

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Posted January 08, 2014 - 08:06 PM

Darn, I was getting right into reading this build, and now it's dead.

I hope you build one for the Ht23. Yes?

I'm guessing you did well selling that 430. Congrats. You'll find another, and

have a good start already on a cab for it.

Sorry about that. I DO plan to put a cab on the Ht23--it started snowing today and there's two more days of snow in the forecast.

 

I plan to use the basic shape of the JD420 cab, but have to allow for the FEL and differences in the Bolens fenders, etc.  I have some 3/4" square tubing and some thin 2" channel, so I might just use that for the frame and put some 18 ga sheet metal I have on it... guess I'd better get crackin'

 

Smitty


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#15 IamSherwood OFFLINE  

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Posted January 08, 2014 - 09:20 PM

Some day, I may get around to building some sort of a windshield. I don't

really care to be in a total enclosure. I would just want to keep the dust that

blows back, off my legs. Right now, I just take a raincoat, and lay it on my lap.

I kinda like the winter in my face. It makes me feel like Geo Clooney in "The

Perfect storm" Aaaargh. :rolling:







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