No. 13 in a series compiled by David R. Janson,
SAM #273, AMA #78416 and MECA #210-04.


Thirty years had passed from the time that Glen Morton, Omaha, Neb. had brought out his Morton 5 cylinder, radial, spark ignition, four-cycle model airplane engine until the hobby world learned of the new PM-5 and 7 cylinder radial, four-cycle model engines by Englishman Glen K. Hargrave in 1975. Hargrave had been designing model engines for some years before this but had never gone commercial. In partnership with John D. Stokes, an English chartered surveyor, they interested the large English "power-Max" brand company, adopting the PM designation for their engine. The Brown Hobby store in NYC took on the modestly advertised engines, first the PM-7 In October, 1976 at $1,300 and then the PM-5 in may, 1977, noting it was "in stock" at $999.00!

Apparently the previous ads meant that one could order only through Brown Hobby. Briefly during this time the company left England to manufacture in Ireland. No more ads appeared in 1977 and apparently a "falling out" of sorts with Power-Max caused production to cease shortly after losing the PM logo, and the Irish manufacturing plant was closed. (A short-lived rumor in MECA noted that a PM-5 could be purchased for around $400 after the closedown at that time.) An interested American, Wally Warner, owner of a large photo processing lab in the Chicago area, purchased the entire operation, name, good will and all from Mr. Hargrave, who fortunately had seen the need to modify certain components of his engines and thus Mr. Warner got the new MkII drawings. But there is much more to this story as the engines, much modified are still in production in the USA.

Originally when Mr. Warner purchased all the rights to the engine, he didn't utilize the "Technopower" name but instead began a series of colorful and attractive ads in American model magazines under the name Executive Engines, Co, 16650 S. 104th Ave., Orland Park, Ill. 60642. The ads touted "The Running Radials Have Arrived," and pictured a black 7 cylinder and an unanodised aluminum 5 cylinder with introductory prices of $785 and $685, and the possibility of purchasing "gold collector's editions" at premium cost, and further going into detail on engine specs, performance etc. Available monthly quotas were noted to the dealers with a deposit of $50 with each order.

Shortly after the introduction of the engines Warner changed the company name to Technopower-II, Inc. same address. During the first year of production a serious "flaw" was identified, ie the molded, reinforced nylon rocker covers tended to warp when hot changing the tappet clearances. This was changed to aluminum rocker boxes. Engines available were black anodized, all aluminum finish, spark ignition, and glows, all serialized and then in late 1983 the new "Big Bore 5" radial was introduced with much more power.

No attempt will be made here to technically describe these magnificent engines except to say...the engines are four-stroke-cycles, with pushrod-operated overhead valves and glow plug ignition. They have twin ball bearing supported crankshafts, twin ball bearing supported cam carriers with needle bearing master connecting-rod and small OS 10 FSR throttle type carburetors. Swanson glow plugs were used. At .96 and 1.18 cid they are in the 3/4-1 horsepower range and are subject to the same dangers of hydraulic lock (oil draining into the lower cylinders) as full size engines. Mr. Warner sold out and moved on to full size airplane engines and a number of new and innovative engines by the new owners includea magnificent 9-cylinder radial currently manufactured.

All engine collectors desire the 1st model PM-5 and 7s of which only a dozen or so were actually sold. The first models under the Technopower-II name are almost as desirable to find especially in the spark ignition configuration. While this beautiful engine was the first in many years, three new and very expensive radials have appeared on the market, as well as the smaller G-Mark .30 5 cylinder, two cycle, which was the subject in this series months earlier.

† P.G.F. Chinn's analysis in the Mar. 1982 and Dec. 1983 MAN are chock full of the technical information you need.


This page reprinted from "Model Engine Designer and Manufacturing Profiles" by permission of the author, Mr David R. Janson.



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