Very early 'travelling arm' gramophones - Question

[poodling around]

This is a very 'basic' question ...........

I notice that very early Victor / Zonophone / Columbia gramophones have wood or metail 'travelling arms' - which lead from the horn to the reproducer.

Like this columbia on Youtube for example:

[urlhttps://www.youtube.com/watch?v=HDVgFH2DfLY][/url]

My question is, what is the purpose of the travelling arm ? Is it to ensure that the reproducer / sound-box remains correctly aligned to the record ?

Thanks for clarifying this for me.

[An Balores]

It is to allow the reproducer and horn to track the grooves, pivoted on the back bracket so that the whole lot, horn and all, moves on the swivel. There is no tone-arm, its just a soundbox fixed to a horn. Later machines, of course, dispensed with this method and a tone-arm swung across the record (less weight and wear) with the horns were fixed separately. How well it tracks, the experts will know. I would imagine the weight of that horn would be quite brutal on a record.

[zipcord]

balance the weight of the reproducer on one side and horn on the other

[An Balores]

balance the weight of the reproducer on one side and horn on the other

But the weight of both reproducer and horn rest on the arm, which swivels at the back. There is no fulcrum in the middle to allow balance between the two components.

[poodling around]

It is to allow the reproducer and horn to track the grooves, pivoted on the back bracket so that the whole lot, horn and all, moves on the swivel. There is no tone-arm, its just a soundbox fixed to a horn. Later machines, of course, dispensed with this method and a tone-arm swung across the record (less weight and wear) with the horns were fixed separately. How well it tracks, the experts will know. I would imagine the weight of that horn would be quite brutal on a record.

Thank you An Balores.

The horn moves as well ?

The wood allows the sound-box then to remain at the correct angle for the record groves and allows free movement 'across' the record ?

I have never actually seen one of these gramophones / phonographs but will see one soon which needs the wood 'bar' repairing / replacing. I have seen photographs of 'Berliners' and guess they are the closest designs.

I just can't seem to understand how it works but hopefully will within the next few days.

[CarlosV]

The horn moves as well ?

The wood allows the sound-box then to remain at the correct angle for the record groves and allows free movement 'across' the record ?

The horn bell moves as the needle travels on the record, redirecting the sound over an arc depending on how far from the spin axis the bell is located. The wood arm keeps the soundbox perpendicular to the record groove, and moves only around the vertical axis, like a clock hand. The tracking of these machines is quite horrible, and the high momentum of the combination soundbox-arm-horn makes it a record eater. There was some progress when the back bracket replaced the travelling arm, especially in reducing the dynamic pressure on the grooves, but the tracking only improved about two decades later, with better designed arms and better alignment of the soundbox (and needle) with the record groove .

[An Balores]

Carlos has described the movement of the arm very well as being similar to how a clock hand moves around the face of the dial. You can see that the arm pivots vertically, at the end of the arm, to allow the operator to lift the needle, soundbox, horn and all, from the record and replace the needle again on the next record. Then you can also see the pivot lower down on the upright attached to the back bracket, which allows the arm to swivel horizontally and so track the record grooves, as well as allowing the operator to swing the whole thing back from the centre and thus play another record. As Carlos has confirmed, the arrangement puts a lot of weight and pressure where the needle sits in the record groove.

[Hoodoo]

I think these machines get a worse reputation than they deserve.
I have weighed the tracking force of my front mount machines and they were all around 140 to 160 grams, about the same as my VV machines and Columbia BI. I have made counterweight systems for the front mounts, and keep the weight between 60 and 80 grams at the needle tip.
As for tracking, the longish pivot-to-needle tip distance, along with the inch or so offset of the soundbox to the outside of the arm pivot point gives better tracking than my VV-X, which has the needle pretty much lined up with the pivot point. Not good.
My longest traveling arm machine has a tracking error of just 6 degrees at the worst point in its travel, compared to my VV-X, which is about 20 degrees to the bad. yikes!
I will try to attach a photo of a counter-spring setup I have on the long one.

[CarlosV]

I think these machines get a worse reputation than they deserve.
I have weighed the tracking force of my front mount machines and they were all around 140 to 160 grams, about the same as my VV machines and Columbia BI. I have made counterweight systems for the front mounts, and keep the weight between 60 and 80 grams at the needle tip.

The main drawback of the travelling arm design is not really the weight, which as you correctly stated is not much different from the other later designs, and can be reduced with counterweights like yours. The problem is the momentum of the composite arm-horn, creating a dynamic counterpressure (drag) that is much higher than that of a design with only the arm. This cannot be corrected, as is inherent to the design. There is a design of the 20s, made at HMV and called Lumière, that attaches a big 12-inch paper diaphragm to the needle, and although it is very light, it also eats records like the older travelling arms due to the same issue.

As to the tracking, all machines up to the 20s (as far as I know) had poor tracking as they had soundboxes that were not parallel to the groove, but to the arm, creating a misalignment. This was only corrected with the more modern designs in the 20s.

[Hoodoo]

The main drawback of the travelling arm design is not really the weight, which as you correctly stated is not much different from the other later designs, and can be reduced with counterweights like yours. The problem is the momentum of the composite arm-horn, creating a dynamic counterpressure (drag) that is much higher than that of a design with only the arm. This cannot be corrected, as is inherent to the design. There is a design of the 20s, made at HMV and called Lumière, that attaches a big 12-inch paper diaphragm to the needle, and although it is very light, it also eats records like the older travelling arms due to the same issue.

I guess you are referring to the side load on the record groove due to the mass of the horn and traveling arm. I agree that could be a problem, especially if the arm does not pivot smoothly. I am going to measure the side loading of my various machines and will report my results.
The side of the grove pushes the needle toward the centre of the record at a rate of less than one inch per minute (typical 78s have 80 to 100 groove walls per inch), so I think the side load will not be so much.
I may be wrong though. I will do some measurements on my next days off.