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EX JUNK's Seat Construction


Well-Known Member
This tech article was provided by EX JUNK.

First off I started with a sketch of what I wanted the interior to look like.

I then "dummied" it up using some 2" styrofoam that I got at Home Depot.

I then transferred things to a wooden mock up in order to build the framework.

After I was satisfied with the dimensions of the wooden mock up, I proceeded to build the aluminum seat base.

You will notice, in this picture, that I paid particular attention to the rake angle of the seat base. That is very important to having a comfortable seating position.

You will also notice that the seat back is angled in relation to the seat bottom as shown in this picture. That, too, is very important to comfort. If you are in doubt of any of this, take a look at any factory seats and you'll see the angles that I'm referring to.

I incorporated a total of five mounting points for the seat. There are four in the bottom front with the two outer ones attaching to the frame and the two inner ones attaching to the floor only.

The three mounting points on the seat back attach to the reinforced body structure.

Next I attached the foam to a plywood base with contact cement and "carved" the desired pattern with and electric carving knife (my wife was not real happy with that) and a 4" grinder.

The seat back drops in and attaches in a very similar way that a factory seat rear attaches.

The seat bottom also mounts like a factory rear seat.

The completed interior. The seat frame sits 1 3/4" off the floor at the front of the base and tapering to floor level at the rear. The front lip of the upholstered seat is 5" off the floor.

All in all it makes for a very comfortable seat that is relatively easy to build. The cushions are easily removable for cleaning.

Shaping foam can be done with a kitchen electric knife and a grinder
How thick and how dense is the foam you sit on? I was thinking about making a frame and nylon webbing to cushion my butt a little more for long runs.
How thick and how dense is the foam you sit on? I was thinking about making a frame and nylon webbing to cushion my butt a little more for long runs.

I got the foam from an auto upholstery shop so I do not know the density of it except it that it is the proper density according to the shop. It is only a couple of inches where my rear sits but is extremely comfortable. My wife, who has severe back problems and arthritis, has absolutely no problems on extended rides.

Sorry raising an old thread from the dead but this needs a bump! Ex, you make this look so easy!!! Let me tell ya, I'm gunna need some big time help with my C-cab. Thank you for the this!
Thank you for the compliments.

I seen the diamond plate you used what other materials did you use?

On the base I used 1"x 1"x 1/8" angle, 2"x 2"x 1/8" angle, 1"x 2"x 1/8" tubing (cut that at an angle to act as a riser to get proper seat angle) and some 1"x 1"x 1/16" angle that I opened the angle to attach the piece of stainless that covers the driveshaft tunnel. (I bent that stainless around a large steel post.)

On the backrest there is 1"x 1"x 1/8" angle for the upholstered part to rest on. The backrest is attached to the base with some 1 1/2"x 1 1/2"x 1/8" angle that I opened the angle on to get the proper rake angle for the backrest. I also used some 1 1/2" angle brackets on the front to strengthen the backrest.

I think that if you examine the pictures closely you'll be able to see where and how all the parts were used in the construction of the seat.
Jim, you took this to your upholsterer and they took it from there?

I need to bone up on what exactly an upholsterer needs to do their magic.


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