I have a Neewer 80cm slider for shooting videos with my DSLR. The tripod head I use with it has damping to help with smooth shots, but the slider doesn't have any damping.

This is a fairly simple way of adding a damping mechanism to a slider.

Supplies

Video slider

2x 0.2Nm rotary dampers (ACE FRT-G2-101 available from RS components)

2x 12mm plastic model pulleys

2mm polyurethane belt x 1m

4x M2 8mm screws

2x M4 or M5 12mm screws

2x M4 or M5 shakeproof washers

2x Aluminium blocks approx 25x14x6.5mm (or 14mm cut off a 1"x1/4" bar)

Cable tidy wrap (optional)

Black paint (optional)

1.6mm drill bit

3.5mm drill bit

3.3mm or 4.3mm drill bit

4mm or 5mm drill bit

M2 bottom tap

M4 or M5 taper tap

Superglue

Drill (preferably a pillar- or bench-mounted drill)

4mm Allen key

Screwdrivers

Step 1: Mount the Dampers

Remove the ends of the slider by undoing the bolts with a 4mm allen key.

Slide the trolley off. Removing the wheels is optional, but might make marking it out easier.

Mark where to drill 4 1.6mm holes according to the photo.

I chose not to drill all the way through, although the holes will come out through the rubber on the top, so shouldn't show.

Cut an M2 thread in these holes with the appropriate tap.

*Top tip* Use a small drop of oil on the end of the tap to help cut it. If the tap starts to bind, back it off a bit and try again.

The pulleys will probably come with a boss on one side which I chose to cut off, although it doesn't really matter.

Drill the holes in the pulleys with a 3.5mm drill bit, which will be just enough for an interference fit on the rotary dampers.

Apply a small drop of superglue in the hole of a pulley, push it onto a damper and turn it to make sure you don't glue the damper mechanism!

Screw the dampers onto the trolley.

(You might notice one of mine doesn't look quite straight - I broke a drill bit in the intended hole. Doh!)

Step 2: Create the Belt Anchor

If you're using an M4 screw for the anchor, drill 3.3mm holes in your aluminium blocks as per the diagram.

Line these up at the ends of the track, with the top of the block in the photo flush with one of the rails.

Drill through the block and the track.

Cut threads in the holes in the track.

Drill the holes in the blocks out to 4mm.

I chose to spray the blocks with black paint at this point.

Step 3: Attach the Belt

Wrap one end of the belt around the M4 screw, underneath a shakeproof washer. Tighten the screw enough so it grips the belt.

Step 4: Replace the Trolley

Slide two of the wheels over the rails and feed the belt around the pulleys as shown.

Keeping a slight tension on the belt, roll the trolley onto the track.

Turn the whole thing over. Wrap the belt around the other screw and tighten it. Check how well the slider operates and adjust the tension accordingly.

The belt is somewhat more elastic than I would ideally like it to be, so it needs to be quite taut.

Trim off the excess belt, leaving enough to get hold of if you need to adjust the tension at a later date.

I tidied the ends of the belt with a short piece of cable wrap.

Bolt the legs back on the ends of the track and you're good to go!

I haven't actually used the slider with this modification yet, so it could be a colossal waste of time, but I think it will be an improvement!