Helge Palmcrantz, Swedish inventor and industrialist, was born in Hammerdal, in the province of Jämtland, the son of a captain in the Jämtland Ranger Regiment. He was enlisted as a cadet in his father's regiment. After a couple of years he left the regiment to study at the Technological Institute of Stockholm. In partnership with his brother-in-law, Theodor Winborg, Palmcrantz founded a small workshop on Vollmar Yxkullsgatan 25, Södermalm, Stockholm; as number of employees increased along with the production volume, he moved to a new factory on Kungsholmen, where they manufactured firearms, reaping machines and other agricultural equipment of their own design. On there would be Palmcrantz & Co factory on Lövholmen, Stockholm as well. In 1868, the first version of his machine-gun was finished and a demonstration of its capacity was held on Ladugårdsgärdet, Stockholm in front of the Swedish Defense Minister. R. Abel. After a couple of modifications and improvements, he patented the multi-barrel, lever-actuated, machine gun and it was bought into the Swedish army as Kulspruta m/1873.

Same year, the machine-gun was shown on the 1873 Vienna World's Fair. To reach international success, Palmcrantz met Nordenfelt in 1875 and the latter's company became his British agent, they agreed to market the machine-gun under the well known Nordenfelt brand and his second model kulspruta m/1875 would be known as the Nordenfelt machine-gun after his financial backer, Thorsten Nordenfelt. It was Nordenfelt who convinced Palmcrantz to increase the caliber of his gun to one inch, making it a suitable weapon for use against the growing threat of torpedo boats. After Palmcrantz succumbed to an early death from a bleeding ulcer and Nordenfelt continued to develop and manufacture his guns in Sweden and Spain. Helge Palmcrantz has a former school named after him; the block names "Kulsprutan" and "Lavetten" on Kungsholmen is named after his factories at Hantverkargatan

HNLMS Wassenaar, was a unique ship built for the Royal Netherlands Navy. The Admiraal van Wassenaar was part of the 1852 program which started the introduction of screw propelled warships to the Dutch navy; the first phase of the plan consisted of the Wassenaar, two steam corvettes of the Medusa class, the steam schooner Montrado. The Wassenaar was laid down in Amsterdam on 12 February 1853; when she was commissioned in July 1857, she was the first steam frigate of the Dutch Navy. The Wassenaar was designed and built as a sailing frigate; this meant that her dimensions were the same as those of a sailing frigate laid down decades earlier, except that she was about 6.5 m longer. That she was only 6.5 m longer was due to the fact that she was meant to be a frigate with auxiliary power. Therefore, her engine was small, could be fitted with small adjustments; the first captain of the Wassenaar would arrange his own quarters to include a comfortable sleeping place, a small saloon, an anteroom or as he called it'church'.

In the anteroom there was place for two quadrilles of eight pairs each. He spent a lot of money to lavishly decorate these rooms, he noted that he did not regret this, as there were 25-30 ladies in these rooms. The Wassenaar had machines of 300 nominal horse power made by Fijenoord in Rotterdam; these were to make about 50 turns On the first trial run the Wassenaar attained a speed of over 8 miles. The machinery made 56 turns with a vacuum of 25.5-26 cm, the screw slipping 20%. Of course this trial was not with full load, nor sails, so it was not that precise for the speed she would attain later. On her first trip from Nieuwediep to Plymouth she reached 6.5 knots at full speed, the screw making 52 turns a minute. As a frigate with auxiliary power the Wassenaar was foremost a sailing frigate, she had the sail plan of a Full-rigged ship, allowing her to make over 10 knots under advantageous conditions. Of her first 13 month trip to the Mediterranean the mode of travel per day is known, she used sails only on 95 days and sails on 21 days, steam only on 2 days.

In this respect the cost of coal was significant. Her first captain would note that the Wassenaar could consume 1000 guilders a day in coal; the Dutch navy used smooth bore muzzle loading of a uniform caliber of 30 pounds, just like the French and English navies did. The basic policy of these navies was that 1st class frigates mounted heavy 30-pounders on their lower deck, shorter versions on the upper deck. For the Wassenaar this meant 22 long 30-pdr No 4 on the main gun deck and 12 long 30-pdr No 3 on the upper deck; as shell guns were required, 8 shell guns 20 cm No 2 were added on the main deck, 2 shell guns 20 cm No 3 were added on the upper deck. To fight faster steamers a Long 60-pounder guns on pivot and sled was placed on the bow; this resulted in an armament comparable to foreign steam frigates, e.g. the English frigate HMS Arrogant. The Arrogant had a 32-pounder 56 cwt gun comparable to the Dutch long 30-pounder No 4 and the French long 30-pounder; the same can be said of Arrogant's 32-pounder, the Dutch long 30-pounder No 3 and the French 30-pounder short gun The Dutch shell gun 20cm No 2 weighed 3,100 kg and was comparable to the English ML 8-inch shell gun of 3,300 kg.

A comparison with other ships in the Dutch navy shows that the Wassenaar did add significant power to the Dutch navy. The previous sailing frigates 1st class had 30 long 30 pounders No 1,2 or 3 and 22 medium 30 pounders, they did not mount a gun comparable to the heaviest foreign 30-pounders and had a weak battery on the upper deck. The Medusa-class, built with the Wassenaar, mounted 12-15 long 30-pounder No 3, resulting in a total weight of artillery, only about one-third of that of the Wassenaar. In summary: the Wassenaar introduced a 30-pounder comparable to the heaviest foreign 30-pounders as main armament on Dutch frigates, provided the main fire power of the Dutch steam fleet. By 1869 the Wassenaar had been re-armed, it retained the 60-pounder and had 24 Long 30-pounders No 4, 8 16 cm RML, 12 light grenade guns of 20 cm. The exact distribution over the decks was not indicated; when the Wassenaar became a training ship a limited number of guns was retained for the students to practice with.

Her first captain was enthusiastic about the Wassenaar. His only doubt was the amount of ballast on board, he noted. He noted that in a storm the ballast had caused so many shocks that amongst other damage the main yard fell down. In January 1858 the Wassenaar was allowed to dump 40 tons of Ballast near Mahon. After dumping another 40 tons of ballast at Malta, making an alteration that allowed her to lift the screw out of the water, the captain declared the Wassenaar to have been the best sailer that he had set foot on, she made 10-10.5 knots on a close reach course. During the 1862 parliamentary investigation Captain-lt J. A. H. Schreuder would state that the Wassenaar was the best of the 5 steam frigates that the Netherlands had. In the media there were doubts about the fine lines and size of the Wassenaar; when it was getting coppered for its first trip in Vlissingen, the media wrote that the visually perfect ship would make a good steam frigate according to some, but raised a lot of mixed feelings with others.

The Wassenaar was built using many parts of the Piet Hein. The Piet Hein had been laid down as a ship of the line of 74 guns. On 1 January 1834 she was under construction in Amsterdam. In 1844 the Piet Hein was mentioned. In 1850, the Wassenaar was mentioned as