Mechanic Crawler - Slider - Roller

The project is for a mechanics lay down crawler to get under cars and do oil changes, repairs etc. I also use this slider when I buff and polish the car on the lower panels.
It can be used as a seat for anything your working on that is close to the ground.

Upgrades

You can do a few upgrades to this project - by doing a 3rd layer of wood supporting the wheels - just use the holesaw to cut through the extra thickness. This will recess the wheels further and get you even closer to the floor. Also some black vinyl would have been great to finish off things as it is easier to keep clean.

Materials

1. Piece of ply/chip board approx 105cm x 34cm - you can make your own custom size to suit.
2. Pivot wheels that rotate 360 degrees , they will need to be strong enough to support your weight. I used 4 x 25kg castors with 4 screw plate system.
3. Screws of various lengths 25mm, 35mm and 55mm depending of your wood thickness.
4. Staples of various lengths 6mm, 8mm and 10mm.
5. Scraps of foam, upholstery foam, packing foam and old wadding pillow.
6. Finish material of your choice - a large piece vinyl / fake leather or in my case I recycled a pair of jeans and a t-shirt.
7. Packing Tape to get
8. Shoe glue - be careful that it does not react with your foam - do a test on scrap.

Tools.

1. Circular Saw to cut the panel.
2. Hole saw to countersink wheels.
3. Drill with screw driver tip.
4. Jigsaw to round off panel.
5. Electric staple gun for upholstery.
6. Scissors
7. Stanley knife/blades
8. Hammer to drive home staples if needed.
9. Small flat head screwdriver and pliers to remove staples as needed.
10. Router to round off edges - optional

Get a comfortable position

You can do a dry run to custom size your board just lay down on the main board and mark out where your body will be positioned.

Tip - If your unsure can where to do the holesaw cuts just lay your panel on the ground and position your supports at either end. I had the head end of the board positioned like a pillow and the butt end support should be clear of the lowest part of your back and butt. To get into position I sit on the lower support and lower myself down till my head rests on the head end wheel support. Then you can get off the board , leaving the supports in place and position the wheels to suit - trace your final wheel position and use a small drill bit through the center of the position to mark the main board for the holesaw.

I use the lower support just under my butt which helps my back anchor between the headrest and lower supports.

Cut down your wood - I made the main piece about 105cm x 34cm , and the wheel supports out of scrap cut down to the same width. then use your holesaw to cut through the base and set your wheels on the support. You can get your wheels cutouts pretty close to the edge because the wheel support panels will reinforce the piece. Use a holesaw that will give you enough clearance as your castor wheels will turn 360° The holes can also be 45° routed to give a little extra clearance.

Tip - make the support boards with an angle transition this will make it more comfortable. I used a 45° router bit on the edge of the support as shown. Remember as you later build your foam to not make the lower butt end padding to high but with plenty of soft padding this will make it much more comfortable to get into position.

Screw it - Screw the base and supports together then screw in your wheels making sure they are free to rotate 360°

Foam padding - I used some hard foam for the head rest and lower support. This can be glued into place with shoe glue - be careful that the foam does not react or melt with the glue chemicals - double sided tape would also work. Try to bevel the harder foam edges with a Stanley blade to get them more comfortable.

Tip - Test as you go - as you add layers of padding.

Tip - Hole for hanging vertically - the hole you see between the wheels is to hang the trolley up on a nail or large screw. This can also be done at the end of the project

Keep building Layers - with my thinner recycled foam scraps I start to build layers of padding. Just staple as you go to the underside of the board, if needed you can also staple on the topside as the successive layers will cover those staples and you won't feel them. Trim the underside excess foam as you go.

Keep layer and testing the comfort of your crawler. If you have some good soft upholstery foam or a few layers of yoga mat you can bypass most if not all of the foam scrap layering I had to do. Use tape if needed to hold scraps in place. Finish the final layer with a complete piece of foam and staple in position on the underside - keep the staples close to the edge as you can cover them over with the finish materiel.

Trim the underside excess foam as you go.

Use your recycled pillow wadding to pad out the whole board. Extra wadding can be added to to the head cushion and lower end transition to your back. The wadding if large enough can be stapled on the underside in place. You can also separate out the wadding to fill holes and low spots or build up areas - when you compress and staple the finish fabric it will hold it all in place. Once your happy with the support cushioning then you position and staple the finish fabric. S

Tip - Fabric Tension - Start by stapling the foot end of the base on the underside with 6 staples across, making sure the wadding stays in position the the panel can now be flipped so that the wheels are showing. Tension fabric at the head rest end. The type and stretch and resistance of the fabric will dictate how much tension you can apply. Remember that the because of the head and lower cushions you will need to pull in the sides and adapt to those shapes - so just take your time and check the tension and alignment as you staple. I recommend pulling and stapling at the head / back transition then doing the same at the lower transition then work on the middle area. Finish at each end and corners. Finalise all the staples and trim any excess.

Project Finished

For me I had some type of spongy table underlay - in off white which was where I would have stopped but the idea of grease marks made me go for an extra step of finish fabric.

Using what was left of another upholstery project I decided to finish off the mechanics crawler with a jean leg and a t-shirt. I cut the heavier seam of the leg and used leftover pillow wadding to get even more padding. The length of the leg was to short to finish in one piece so I just trimmed and folded the transition.

Tip - Jean Part - The jean material is pretty strong so you ca do a fairly taught finish. Start by centering the seam if possible and anchoring at the base. You need to keep an eye on the tension as you will only be able to staple on 3 sides. Leave the last 10cm to 15cm on the transition end with just one or 2 staples and don't use to many staples on the jean piece as you may need to adjust.

Tip -T-shirt Part - Position the t-shirt and start to staple that in place. I used the whole t-shirt front and back and stapled it as a double layer without even cutting. The T-shirt will go under the jean material at the transition point so trim any excess bulkiness to make that joint as smooth as possible. You can now finalize all the T-shirt stapling to get it tight and in position.

Tip - Transition - Any bulkiness can also be removed from the jean material - be sure to leave enough so that it can be folded under itself. Remove any staples that prevent you from working the material. This fold should be stretched tightly and stapled so that it holds well and does not pucker. The jean material will also anchor in the t-shirt or hide the staples if need on the t-shirt transition. If you have tension or puckering problems remove staples with your small screwdriver and pliers and adjust bit by bit.

Once your happy with the tension on the finish fabric you can continue securing with a final run of staples on the underside.

Tip - Handle - I added a piece of wood to act as a handle to make the trolley more portable.