Arden Super Atom


Name Super Atom Designer Thomas Raymond Arden
Bore 0.750" Stroke 0.625"
Type Gas Ignition Capacity .098 cuin
Production run Large! Country of Origin USA
Photo by RonC, Ken K Year of manufacture 1939-41



This little engine is considered by some to be one of the ten finest ignition engines ever made. Its design was commissioned in 1939 by the Polk Brothers—then and for years to come, one of the bigest names in model aviation supplies and promotion—and executed by one Ray Arden (who would later father the glow plug). Manufactured by "Microdyne Engines" NY, the engine was unusual for it's small size at the time of its inception.

A patent application for the design (115,974) was lodged on May 13, 1939. A more descriptive patent (2,274,644) was filed on June 12, 1939; granted March 3, 1942. Among the original idead covered by the later patent, and present in the "Mighty Atom" were front rotary intake from a fixed fuel jet combined with a variable air supply; bypass via a piston valve; ball and socket little end, and the nicest snap-action timer you've ever seen. All this at a weight equal to the coil it would need to run it! It's worth noting that the second patent also covers a number of other rather wild ideas, thankfully never seen in any production engine!

Details of the engine, it's history and variants have appeared in Engine Collectors Journal, Issue #84 [1] (with additional info in issue #83). In 2003, the late Roger Schroeder wrote a series commencing in ECJ #158 detailing his efforts to build a "new" Atom from a set of aparently original magnesium castings he had obtained [2]. Roger's series spanned five issues and brought to light additional detail about post-war Atoms. Back in the late 1970's, Ted Crouss obtained about 10,000 sets of original castings left from production of the last Atom. He made extensive drawings (17 sheets, labeled "SKA") making measurements from examples of the engines—ie, no original drawings were used. Ted advertised and sold sets of castings, plans, and a fuel tank for $15.50 (read it and weep) under the name TAC Aero. Some time after he first offered these, he accepted an offer to sell his remaining inventory to a firm intending to build the engines overseas at low cost.

Enter Morrill-ADC. In 1984, new production Atoms were advertised at $69.95 and advance orders taken. ADC never delivered any engines. In early 1986, they wrote to notify their patient customers who had placed advance orders of delays, offering a full refund. This offer was repeated later the same year, but as far as is known, no refunds were actually issued. Roger noted that while his good name was used in the venture, John Morrill was neither an owner nor partner, simply an unpaid technical consultant

But there is more to tell and a definitive article for ECJ is being prepared by Roger Schroeder for publication in 2003. Roger has uncovered an Atom based scam in the US, and how some of the fruits of that operation made their way to the UK in the form of original, magnesium castings.

Aeromodeller of June 1994 carried an article by Ron Prentice describing his adventures building a Super Atom from castings and plans he obtained from Kieth Harris of SAM35 in the UK (presumably, one of Ted's TAC Aero kits). This was only the second engine he had made and he reported that his reproduction ran well. This effort is all the more creditible when we consider the difficulty he, as a relative beginner and self-taught machinist, must have encountered with the work-holding problems posed by the castings. Ken Croft also acquired three sets of castings and has been making slow progress over the years, saying:

I started on three Atoms. I machined all the mag parts, and that was a pain. There is no excess metal and no way to hold the parts easily. You end up making pot chucks to hold the head and the rear cover. I then made press tooling to press out the tank tops, and the tank top covers. I made the fuel/air barrels and arms and the fuel jets with their 0.006" dameter hole. Then I got fed up and put the project away. I will finish it one day, but I absolutely detest any repetition. See pictures. And that really is the tooling, with a spare throttle barrel, tank top and tank top cover also included in the picture if you can spot them.


[1] Ehticknap, Ted, The Atom Revisited, The Engine Collectors' Journal, Volume 15, Number 6, Issue 84, The Model Museum, Buena Vista CO USA, 2009.
[2] Schroeder, Roger, An Atom Restoration, The Engine Collectors' Journal, Volume 28, Number 2, Issue 158, June 2003, The Model Museum, Buena Vista CO USA.




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