OT: Auto radio motor generators Was:Mechanical inverters

An article in RadioCraft in 1934 intimates that there MAY have been motor-generator recievers built, but provides no examples.

" The auto radio of a few years ago was a crude affair, in comparison with present models. Whereas the old model consisted of numerous boxes to hold the receiver chassis, speaker and "B" batteries, and the tubes were such that very little amplification of the meager signal (generally obtained from most auto antennas) fed to them was derived; the new sets are practically just the opposite in that every imperfection has been eliminated. The latest in auto-radio receivers is a single unit with just one or two bolts, at the most, necessary to anchor it to the car. Today "B" batteries have been done away with, a "B" supply unit that obtains its power from the car battery being employed to furnish the necessary plate voltages. This unit may be either of the motor-generator type, or a vibrator which chops the 6 V. D.C. (from the storage battery) into pulsating D.C., stepped up by a transformer to approximately 225 V., A.C. and then rectified and filtered by a special rectifying tube and filter arrangement. Some receivers employ a mechanical rectifier, operated "in step" with the vibrator "chopper," to eliminate the necessity for an extra tube. "

There is also reference made to a 6 tube motor-generator set along with 110 volt DC sets, not in an automotive context. 110VDC radios would have been used on an edison system - and since DC cannot be transformed an M/G set would be required to produce voltages other than 110.

In 1926, W.M. Heina got a patent for the Heinaphone - a "travel radio" which could be installed in a car and used both "A" (1.5 to 2 volt) and "B" -(90-120 volt) batteries. These radios could not be used with the engine running. The first radios that could be used with the engine running came in

1927 with what was known as "damp resistance".

In 1932 "B" battery eliminators using both vibrators and motor/generators became available for use with older sets. No mention made of a dedicated auto radio with a motor/generator.

In a National Radio Institute publication ( #32 - How to Service Auto Recievers) of the time it states "police cars and other special applications sometimes used small motor-generators instead but these are rarely found in private cars" It appears to be produced about

1937?

I also found a vague reference to an aftermarket radio for a '32 ford

- Motorla 300 - that MAY have had a motor-genreator power supply as one of the three parts. However, since Motorola was definitely using vibrator power supplies on earlier radios, I doubt they actually used an M/G on this radio.

That's allI found googling "AUTO RADIO" AND "GENERATOR" OR "MOTOR" OR "MOTOR GENERATOR"

I think the 1936 Cadillac Coupe my boss had in 1961 had a motor generator. Could have been one of his Packards, but fairly sure was the Cad. Was a grey box on the firewall.

my 49 Packard Hearse had a motor generator to run the radio. Took about

30 seconds from the time you turned it on, to when the sound started come on. But there was a "whirling" sound the instand you turned it on IRRC

I had a 10 meter military radio mounted in it that would receive the local police department (circa 1970) with multiple pushbuttons for channels. I think its still in my dads place along with my RTTY gear.

It had a big MG on it.

Gunner

"Not so old as to need virgins to excite him, nor old enough to have the patience to teach one."

MANY tube radios of that era did; I used to fix them.

But not even the antiques the boss's customers owned had dynamotors for receiver supply; just transmit. Some were vibrator RX supply, others transistor-driven invertor. I strongly doubt dynamotor use for receivers, two way or broadcast, was common at all.

a) Dynamotors have a limited lifetime. A police car might get maybe

10-15 minutes of transmit time per day; but 24 hours of receive time if all 3 shifts use the car.

b) Dynamotors draw LOTS of current. Your average 1960 MOPAR had a ~30 Amp generator; it made zero amps at idle and its rated power at good speed. It wasn't AC that had cops always idling the car. There were fast-idle solonoids [ie mash the mike button and the engine sped up...] as well.

We used to suggest 100A Leece-Neville alternators, originally with the selenium rectifier stack on the firewall, for many customers.

I cannot say they were common, but as a kid I had a Ray Jefferson marine radio that had two dynamotors; one for transmit and one for receive. Key the microphone and it went from noisy to really noisy.

Kevin Gallimore

Me too, but not as a kid. IIRC the station was WZX4854

JC

Well unless you can document it, I'm not believing it, from my research. ALL dedicated automobile recievers I have been able to track down from that period used multi-vibrator power supplies - and wuite a few of them were syncronous, meaning no rectifier was required - just a good filter cap bank. The only M/G power supplies I have been able to document, and/or have seen, was for 2 way radio apps. (police radio, aircraft, military, HAM, etc)

You gotta admit, gunner, that radio was NOT an automotive radio. It was a "10 meter military radio"

As for the 30 seconds before sound, with a whir from the getgo - it took about 30 seconds to warm up the tubes, and the 115cps vibrator started as soon as the switch was turned on. MG power supplies kinda "wound up" from an initial "growl" to a high pitched whine or howl usually with lots of overtones. The vibrator started up immediately and held a constant frequency from startup to shutdown. An MG "wound down" when the switch was shut off.

Nobodies arguing that. A Ray Jeffrerson Marine tranciever hardly qualifies as an automobile radio reciever.

Didn't say it did. I was commenting on the statement above about two way radios.

Kevin Gallimore

Can not document as Rodger is not available anymore to talk with.

A few more references found by Googling including an article in July 1932 Popular Science on page 63. Probably about a dozen total references found referring to dynamotor (motor generator) power supply for early automobile broadcast receivers.

Don Young

If it works, this link has photos of early dynamotorrs and a little text:

Don Young

Fascinating site, Don, Thanks.

If it works, this link has photos of early dynamotorrs and a little text:

Don Young

I'm interested - please post the link.

I found a link to an article by automotive writer Michael Lamm on American Heritage.com that references dynamotors but does not give an example of a single actual model that used them. Most of the reference seams to be to those radios that did not work with the engine running.

I wouldn't call it a technical reference nor would I accept it, necessarily as fact.

ALL the information I have had access to indicates radios prior to

1931 or the introduction of the "motorola" were battery sets - most of them adaptations of domestic recievers. Aftermarket "battery eliminators" of 3 types became common to replace those batteries somewhere around the same time. These were "interuptor vibratror", Syncronous vibrator" and "dynamotor" types.

There is no record that I have been able to uncover of an automotive specific radio reciever for general broadcast use that came from its manufacturer with a dynamotor type power supply. Particularly none that were capable of being used successfully with the car in motion.

If someone can find a specific reference to a specific model, with believable specs showing it came with a dynamotor supply, I'm all ears.

Antique cars and antique radios have both been hobbies of mine over the years.

Thanks for the link, Don. It indicates, as I suspected, that the very few dynamotor auto radios were battery sets with an optional dynamotor. The only one sold with the dynamotor as "standard" was the Grisby-Grunow built "Majestic Model B" for the 1932 Ford V8 - and it was their battery set provided with an AE (Automotive Electric) Dynamotor battery eliminator as standard equipment. Packard Electric supplied an optional dynamotor for use on Packard cars also as a one year? option. The 1932 Boasch 920 was also a battery set with an OPTIONAL dynamotor battery eliminator called the Magmotor.

It appears the dynamotors were not available before 1932, and were virtually dead by 1933 due to the superiority and lower cost of the vibrator supply. By 1934 car radios had started to resemble those we are familiar with, with the high voltage supplies totally integrated into the radio set. One peice radios with integrated speakers were very common, and "remote head" radios were available to fit the controls into tight places and free up the glove box.(without mechanical drive cables as used previously)

A "battery eliminator" dynamotor needed supply only10- 20ma at 90-180 vdc, (about 3.6 watts MAXIMUM) and drew in the neighbourhood of 6 amps from the 6 volt battery (36 watts) for a 10% efficiency - on a GOOD model. Many were even more dismal in performance, while a syncronous vibrator was well over 65% efficient.Dynamotors were also relatively shortlived - wearing out brushes and bearings quite quickly while vibrators lasted for many years without service or repair.

I couldn't figure out how to post a link to the Popular Science article. I found it thru Google Books. I don't think it specifically says that a radio was supplied by the manufacturer as a package with a dynamotor, only that they were used that way. The old Rider, Supreme, or similar service manuals might provide more information.

Don Young

I think I've got the link. you may have to scroll to find page 63 or 64. The article seems to treat the dynamotor as a battery replacement, not original equipment.

Don Young

Found it - yes they were referring to "battery eliminators."