My son is obsessed with construction equipment ( like most little boys ) but his favorite by far is the skid steer. I have no idea why, maybe because it is small and compact and once you start looking for them they are everywhere. He can spot one a mile away in the middle of a busy construction site and since I don't have room in the garage for a full size skid steer I decided to do the next best thing!

Logistics:
My first thought was something wearable but since he is only 2 and I didn't want it to be lame and dangerous, I decided on something he could ride in. At the moment we have a whole selection of stroller so that seemed like a perfect frame and it saves it from having to be durable enough to roll and turn.

Now i've got an idea, a kid, a frame and I can really get started.

Step 1: Planning

Everybody knows what a bobcat looks like right? I could have just free-handed something and started cutting but I didn't want to waste time (the time for building this came mostly out of sleeping time with 2 kids in the house) and material so I started looking in Sketchup's 3d Warehouse at the existing models until I hit upon one I liked, the Carepillar Skid Steer 236b. (http://sketchup.google.com/3dwarehouse/details?mid=ef2791b1894dd31478fe949fc1419876)

This model is much more detailed than I would like and I need to simplify it before I can make my templates. I exported a 2 cad drawing from Sketchup ( I have a Pro license at work, if you can't export as a .dwg it is easy enough to export a .jpg and trace it.)

After tracing the exported image and simplifying it along the way, I drew a 4x8 box and planned my cuts to be as efficient as possible.

If you have access to a large format printer run off a print of what you've drawn and go to town. I was able to piece them together from 11x17 and print it on scrap. A little taping and I was ready to go.

Below are the model and the CAD drawing.

Step 2: Cutting! Gluing!

Planning everything out so extensively meant I knew exactly what I needed and it was time to head to the store.

Materials:
2 - 4x8 1in Rigid Insulation
2 rolls black duct tape
1 tube construction adhesive (make sure it is ok for insulation, some adhesive will melt the foam)
1 handful of course thread screws or various sizes
1 roll of painters tape for temporary holding
1 can of permanent spray adhesive (look for one ok for foam)
1 quart of the paint of your choosing, depending on brand of skid steer you want to create.

Tools:
Box knife and blades
Jig saw with fine tooth long blades
120 grit sandpaper
Sharpie

Layout:
Lay your foam sheets out somewhere flat, trace your templates and get to cutting!

Cutting:
I taped the two sheets together since the two sides are identical. When you lay out the cuts make sure that the printed side of the foam is on the inside since it is a pain and will take more coats to paint over.

I only planned out the two sides of the skid steer, planning on just winging the rest so I planned those pieces as efficiently as possible to make sure I had enough for the middle.

Once I had all the pieces cut out I used the adhesive to attach the pairs of pieces and sand them smooth and then assembled those to create the two sides of the skid steer. Areas with extra stress like the arms that hold the bucket, I put several screws in addition to the adhesive.

I hadn't really planned on how it would attach to the stroller and every one is going to be different so grab your stroller and look for where you can attach the sides. I wanted to be able to easily attach and remove it to ideally it would just rest on there. The particular stroller we have has a Y-shaped frame that makes this really easy.

Measure and temporarily attach the sides and cut the pieces for the middle. Remove the stroller, assemble the pieces. Here I used some long 4" screws I had left over from another project and the construction adhesive rather than spray to attached faces to edges.

Now I've got a pink skid steer shell!

Step 3: Details

The main part of the shell was done, now to make it more real. No construction equipment is complete without a bucket. Using the leftover foam and with a toy bobcat as a guide I pieced it together with some 4" screws and construction adhesive. To add some realism and give myself a larger gluing surface area I traced a paint can and cut it in half to make a bracket. With spray adhesive I attached these to the arms and with construction adhesive and some screws added the bucket.

I thought the roof looked a little blank so I cut out some circles and made a couple lights.

The only thing not made of foam was the the hydraulic cylinders, I used a mailing tube and a paper towel roll. I traced the angle onto the tubes and cut them with a miter saw. Using some scrap foam I center the smaller tube within the larger one and the filled the gap with construction adhesive and smoothed it flush.

Step 4: Add Some Color!

I opted for the Caterpillar version of the skid steer to match the Bruder toy that my son loves so much. I found a color that was pretty close and bought a quart in matte finish. For the black I used a matte black and the black duct tape.

I started with the tape. My thought was that it would help make the thinner parts of the machine more sturdy. In hindsight, I could probably have just used paint but I like the contrast of the glossy tape and matte paint in the end and any paint that got on the tape peeled right off.

Yellow was next. I roughed up the faces with some 220 sandpaper and rolled and brushed on 2 good coats of yellow. Everything else, including the bucket got matte black paint.

Again the hydraulic is the old one out. To create the silver I used spray adhesive and carefully rolled on a sheet of aluminum foil before attaching the cylinder to the body with construction adhesive. A little painters tape held it in place until everything was solid.

Step 5: Done!

Loaded up the kiddo and took a spin around the block. Everything worked great! I added some tape in areas that were rubbing on the stroller frame to get rid of the squeaky foam sound and added a couple spacers to help keep everything aligned!

I'd glad that I added a little height to the cab, it makes it easier to lift the kiddo in and out.

Hindsight:
I wasn't sure if the foam would be rigid enough to make the bucket operable. I think that it could probably work, especially if the pivot point was a decent diameter tube or dowel.

The design of the project meant that I had to lift him in and out every time. This isn't ideal and I'm not sure the best way to fix it.

Conclusion:
He absolutely loves it. I have a feeling we'll be taking a lot of Bobcat walks and every time we're out we get a lot of people slowing down and waving. A great little project, an impressive result and a very happy little boy.

Bonus: I also made a little ID card for him (his vest had a little clear id window) also attached below and his outfit - - http://www.amazon.com/gp/product/B002F9NH4A/ref=oh_details_o03_s00_i00?ie=UTF8&psc=1