Froment electric motor prototype circa 1845
This description should be read in conjunction with the description of the slightly earlier prototype Froment electric motor c.1844 (with the wood frame on this web site), which was sold in 2006. Search: froment.
Description Very early prototype Froment electric motor with iron frame base 16” (41 cm) x 7” (18 cm) in which are inserted large black painted wood panels on both sides (specifically as an insulator on the commutator side). The large armature, diameter 14” (35.5 cm), has eighteen horizontal solid iron bars matching the same number of copper contacts on the wood commutator. Effectively this armature has no core just being mounted on a simple iron shaft which revolves on brass mountings with oiling holes on top. Behind the revolving wheel is a large cast iron wheel 15½” (39 cm) with a “V” groove for a belt to drive another machine. Mounted under the armature are four large electromagnets wound with heavy duty silk covered copper wires, two each side mounted at an angle of 45º. One pair are round in cross section the other oval and the iron cores of these magnets are different. The two on the left hand side (as viewed from the commutator side) have round cores whilst those on the right hand side have rectangular cores corresponding to their cross sections. The overall height is 21” (53 cm). The motor weighs 54 lbs (24.5 kg). The “brushes” are revolving copper wheels – the earliest (and crudest) method used on only the earliest Froment motors. This motor is entirely original apart from the small rectangular ceramic junction box under the commutator. Presumably the two copper wires that connected the brushes to the electromagnets directly were broken at some stage and this was later inserted to provide continuity. The motor was run using a transformer with a maximum output of 19 volts. See video. http://youtu.be/_WOE4qTr-Zg This is a very important 'survivor' and may well be the world's earliest electric motor designed specifically to have sufficient power to drive other machinery – I realise that is a bold claim but unless someone can point to an earlier and presumably more primitive Froment motor I believe this claim is justified. It may also be the reason why someone bothered to keep and preserve this electric motor long after it was made redundant by further technological development.
Comparison The comparison with the slightly earlier Froment prototype on this site is fascinating. It shows clearly the next stage of the development of this critically important piece of technology. The Froment was the first electric motor invented that could be scaled up to provide an independent power source i.e to do more than simply rotate itself! The most obvious change in this slightly later model is the use of an iron frame with wood inserts instead of an all wood frame. The present example still uses the highly inefficient wheels as brushes for the commutator. The magnets are still placed at an angle to the armature but they are all wound 'continuously' unlike the 'bunches' on the right hand side of the earlier motor. Gone is the wood core of the earlier motor to be replaced with nothing! The main improvement is on the commutator with eighteen contacts compared to four on the earlier prototype with a similar numbers of bars on each of the armatures. The motor self-starts. The really striking part is the large drive wheel at the rear with a V groove on the circumference which shows convincingly that this motor was designed and capable of working other machinery.
Date I put the date of my first prototype Froment as circa 1844 or early 1845. There is little doubt that the present example was manufactured shortly afterwards, probably within weeks, so I would date the manufacture of this example just a few weeks later.
Historical importance Invented in circa 1844, the Froment motor was the first electric motor to have a power output that could do much more than drive itself, in other words it was an “power source” independent of location (c.f water wheels) marking it as amongst the major examples of applied technology in the nineteenth century. The only other source of power at the time to drive machinery independent of location, was steam power fuelled by coal. There were no dynamos at the time capable of being scaled up so Froment motors had to be powered by zinc and carbon batteries which were extremely expensive. It has been estimated that the cost of using a Froment powered by batteries was about seventy times more expensive than powering a steam engine with a similar work output by coal. Thus for several decades Froment motors were few in number and restricted to the laboratories where they were developed.
The invention of the Gramme Dynamo in 1872, (see example and description on this web site Search: gramme) was critical. At last there was a dynamo that could be scaled up to industrial proportions to provide a power output sufficient to replace batteries. The Gramme dynamo was developed throughout the 1870s just in time for Edison to build his first power stations (putting out direct current electricity) around 1880 using the latest Gramme dymamos, thereby allowing him to move his newly invented electric lights out of the laboratory and into homes and industrial plants. Finally after a gap of nearly four decades after its invention industry was finally able to make use of the Froment motor and the manufacture of commercial numbers of electric motors followed. Froment motors manufactured before this date were few in number and surviving examples are extremely rare and individually historically important. In 2006 when I offered my only previous early example I wrote at the end of my description,“I think I can state with a fair degree of confidence that this is a 'one-off' opportunity. I think it is exceedingly unlikely that I will ever be able to offer another electric motor of this importance or age again”. I am delighted and thrilled to be proved wrong ten years later! It was an extraordinary moment when I finally had this motor, for sure manufactured over 170 years ago, running in my workshop. I wondered when it was last powered up and working.Price £18500
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