Further to some excellent comprehensive reviews of this vintage set, I thought I'd add that this set, as well as the 8837 Pneumatic Excavator, can come with variant clear tubing instead of light grey tubes as well.

I own both vintage sets bought from eBay by sellers who owned each set from New - one 8042 came from Germany. I recall seeing both sets on eBay when I was looking to purchase them with either the black/dark grey and light grey Pneumatic tubing or with black/dark grey and clear tubes.

It appears that Lego initially issued both sets with light grey tubing then switched to clear tubes...

Hope that helps ????

Edit: Weds 2/9/20 Seems some ones found this unhelpful - I fail to see how informing everyone of variants in Lego "unhelpful?" Some folk can be rather cruel indeed...

8042 Universal Pneumatic Set

Perhaps my favorite subtheme of Lego Technic is pneumatics. My favorite set from my childhood is the 8460 Pneumatic Crane Truck, but set that perhaps got me started on that path was the 8042 Universal Pneumatic set. Back in the day, TLC used to release a number of Technic products called "Universal Sets". These sets would usually come with a number of pieces and an instruction booklet to construct a number, usually four or more, of different models. These sets were rather economic, but also somewhat dissatisfying looking back, as every model had at least some parts left over. The Universal product line was also often, but not always, used to showcase a certain construction element. Usually it was motors (8035, 8050, 8054, 8055, 8064), but pneumatic also got a couple of sets with 8040, 8042 and 8044. Even the humble flex system got one with 8074.

The one I'm talking about was unfortunately the last of this line. The 8042 set is a pneumatic set from 1993 and featured about 226 pieces for $38.50 . The set came with an instruction booklet that described on 68 pages how to construct each of the four vehicles that could be built from it: A car, a forklift, a cherry picker and a claw rig. Additionally, it gave instructions how to enhance the claw rig with the 8720 9V Motor pack in order to motorize the claw rig. As such, the instructions are much faster than today's standard in my opinion, as nowadays almost every minute step gets its own page.

The Parts

Click the image for a larger version.
The set comes with a decent number of diverse parts, though only a few gears. Two 8-tooth, two 16-tooth gears which are only used in a single model, two flat 14-tooth gears used for switching the axle on the steering, and a rack gear is all you get. Of course, the focus of this set isn't gears, but the pneumatic components. This set comes with a pump, a big piston, a small piston, two switches, a T-connector as well as a lot of tubing. There is enough tubing (which I had already cut previously), so you won't have to cut down a log tube used in one of the models to create shorter tubes for a different model. Unfortunately, I lost my 15 cm gray tube, and I forgot to include a 7 cm black tube in the picture. The first page of the instruction booklet has a ruler and 1:1 scale examples of how many tubes you need of each length in order to build all four models.

However, the most striking thing about the parts is the prevalence of the color blue. Blue is rather seldom used Technic, where black, gray and yellow dominate the landscape. Seeing that most of the models are also some sort of construction vehicle, they could have easily used the common yellow as the primary color, but it is nice that blue was chosen instead. Though in recent years blue has been used widely as an accent color for liftarms mimicking the seats in various vehicles, it is almost never used as the primary for a model, this being a nice exception. Grey is of course the primary accent color. This set is also a studded construction set, so naturally the set only uses parts that are an even number of studs in length. Of course, this set was released before odd-length gray axles were even in production. What I also forgot to include in the picture above are the wheels, though you will see enough of them later on. Unfortunately, they're a little bit dirty.

Car

The car is perhaps the most basic of the models. It only features a single piston of pneumatic function to open and close the hatch on the single-seat cockpit. This model is the only one in the set that has a seat at all. While this model is the weakest in terms of functionality, in terms of design it is quite nice by hiding away the pneumatic switch and pump, though I think having the switch on the other side and pointing down would have been even better. The pump also doubles as a form of shock absorber for the rear axle of the car. The rotary light is a bit misplaced though.

Forklift

The forklift is the second model in the manual and has the pneumatic functions of raising and lowering the fork, as well as tilting it. It's quite a steep tilt actually, and it's good that they used some 8L axles as the fork rather than any studded bricks which I've seen used for the fork in some older sets. Like all four models (and many, many other Technic sets), this one features steering by turning the rotary light on top of the cabin, though this is the only one where the back axis is used for steering.

The forklift comes with one big design flaw though:

When the big air piston is retracted completely, the fork actually lifts the front axle off the ground.

Cherry Picker

The cherry picker is the model in this set that uses the most parts. It uses up all of the bushes that the set comes with. The pneumatic functions included in the set is of course raising the basket, but also lowering some small outriggers at the back of it to give it more stability. I personally like how the pneumatic switches have been hidden quite nicely on the back of the vehicle.

Claw Rig

The claw rig is my personal favorite of the models, perhaps indicative of me missing out on the 8868 Air Tech Claw Rig, which is definitely something I have to get some time. This one is perhaps its predecessor, coming out two years earlier and also features a small pneumatic piston to open and close a claw at the end of a crane arm. The big piston is of course used to lower and raise said arm. I would have liked it more had they found a way to hide the pneumatic switches a bit better, but they're doing their job nicely.

Final Thoughts

This set has a ton of playability with four different models to build, and perhaps some innovation to be used for it as well. The rare, blue color on the Technic pieces also makes it a nice set to look for. Though it is nothing really extraordinary, it is a very good product, particularly to start someone out on pneumatics.