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 Post subject: The different HMV brakes/autobrakes
PostPosted: Mon Sep 21, 2020 3:01 pm 
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Victor III
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Joined: Thu Jun 13, 2019 1:58 am
Posts: 730
Location: My gramophone repair room
This may sound VERY newbie like, but I would like to talk about the HMV (auto)brakes, my absolute nightmarish part of the HMV gramophone - when it comes to fully understand how they work, and when they are not working, what is wrong. I right now have a problem with a brake on a HMV model 109, and I am still not able to understand what is wrong with it,after looking at it and testing it for hours. Since it is in my repair room, I will take som photos and ask for some guidance in a day or two, BUT to start already now I upload a photo of the brake on my HMV 157. Sooo many different components put together to make the turntable stop !

Feel of course welcome to upload photos of any of the different brakes from your gramophones, so we can inspect the different brakes more closely and discuss the differences, advantages, disadvantages and functions/weaknesses.

I here start with what is known as autobrake no 3 that came into existence in late 1927. (according to the HMG book by Proudfoot and Oakley)

I admit the autobrakes give me often headaches, and since it all happen under the turntable, I am always wondering what is going on under there, and what is not going on, when the brake is not working.

I believe I am not the only one striving with these brakes, so I thought it could be a good idea to talk about them, and even give some comfort to new (and old) collectors who bravely start servicing or repairing on their machines !

Because I of course believe...I am not the only one striving with understanding these brakes !!


Attachments:
HMV autobrake No. 3.jpg
HMV autobrake No. 3.jpg [ 314.77 KiB | Viewed 565 times ]
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 Post subject: Re: The different HMV brakes/autobrakes
PostPosted: Tue Sep 22, 2020 7:59 am 
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Victor IV
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F. Depero, "Grammofono", 1923.
Joined: Thu Feb 24, 2011 4:19 am
Posts: 1065
Location: Italy
You completely forgot to mention what's wrong with your unit.

Generally speaking, to engage this autobrake the arm has to be pulled all the way to the right, then brought back left to the beginning of the record without ever pulling it right again. When it's pulled back right, unintentionally or by the locked end groove, the auto-brake is triggered and the turntable is halted.

What activates the brake is the anchor tooth visible at the extreme left, which engages over the half-moon adjustable with two screws below it, which triggers the leather pad. The half-moon is in turn finely machined as to have small "teeths".

The key point of the whole gear is the three-arms spider washer visible on center-top. The whole thing is friction-driven, and the spider washer shall provide the correct friction in order for the anchor/teeth mechanism to engage. If you move the top arm fork slightly right and left, you should see the tooth anchor go up and down and engage over the half-moon. If it doesn't do so, the spider washer and everything below has to be disassembled and very carefully cleaned with gasoline until everything moves absolutely freely with almost no resistance.

As a final note, this was a late attempt by HMV to craft a very generic auto-brake that would operate without the need of specific turntables or specific spindles or any extra gears. The aftermath of all this is its lack of sensitivity: it needs a *huge* ondulation of the arm in the locked end groove in order to be triggered. Many records, including *many* made by HMV itself, just don't trigger it, whatever you do. Useless to say, records with a centered locked end groove will never engage it.


Last edited by Marco Gilardetti on Wed Sep 23, 2020 3:13 am, edited 1 time in total.

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 Post subject: Re: The different HMV brakes/autobrakes
PostPosted: Tue Sep 22, 2020 8:22 am 
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Victor IV
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Keep'em well oiled
Joined: Mon Dec 18, 2017 2:51 am
Posts: 1085
Location: Madrid, Spain
Besides that, this brake (also fitted in my 194) I've found that produces a very light, but noticeable, drag in the tonearm during its travel to the center of the record. You simply try the free movement of the tonearm with the fork engaged or disengaged from the tonearm pin, and you'll notice the slight difference.
As I usually play this machine with self made bamboo needless, and these are sensitive to any lateral drag, I decided to temporarily substitute this brake for the older type that you must set up in the trigger position at the end of a record. This older model doesn't produce any contact with the tonearm until the point where you set it, then triggers. Thus there is no continuous drag on the tonearm until the very end.
Attachment:
Vintage-Victor-Victrola-Talking-Phonograph-automatic-BRAKE-CONTROL.jpg
Vintage-Victor-Victrola-Talking-Phonograph-automatic-BRAKE-CONTROL.jpg [ 13.58 KiB | Viewed 533 times ]
Inigo


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 Post subject: Re: The different HMV brakes/autobrakes
PostPosted: Tue Sep 22, 2020 1:59 pm 
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Victor III
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Joined: Thu Jun 13, 2019 1:58 am
Posts: 730
Location: My gramophone repair room
Thanks for your comments, I will read them closely, trying to finally be able to grasp the different parts of the later HMV autobrakes.
I feel it is of importance to talk about them in a thread like this, because they have made me scratch my head many times during the last year, since I re started a hobby that now has become close to an obsession:;)

During last summer, I simply removed the autobrakes when servicing each gramophone, cleaned it oiled it and reinstalled it, not at all understanding how they were working. Luckily they were mostly intact, but the problem started of course when I came across some that were not working properly. Then I had to really start dive into them properly, and I admit that they are the components that have given me the biggest headache. Main springs, governor springs, motor parts in general, they have become more and more familiar, but the autobrakes !

A general talk about the HMV autobrakes, pitfalls and challenges, can hopefully be of help to future collectors too.

I did not forget the problem with my HM;V 109 this morning, I just did not have any photos taken, and decided to start with uploading a photo of number 3, where they really started to become intricate, at least to my eyes. I guess the main challenge is that they work under the turntable, so it is impossible to see what really happens, and how every part of the autobrake come into function.

But let us return to the HMV 109, and the attached autobrake, that I understand must be the first autobrake from HMV, even if it is not numbered as no. 1 in the HMG book. It is simly called Automatic Brake, (Hand set, 1912-1926). I realized when having another look at the gramophone today, the problem seemed more obvious than it did last autumn, when I was not able to realize how it was working, and also was afraid to destroy anything when removing it from the gramophone.

I actually think this is an important aspect, as a beginner one easily have too much respect for everything, and even unscrewing a component like an autobrake, feels terrifying. When I today had another look at it, the problem with this autobrake now seemed very obvious. The last months have given me confidence in restoring and servicing the machines, and this autobrake is pretty easy to understand when looking at how it is working.

The problem with this autobrake ( on my gramophone)is that the brake goes on while the record is playing. I have diagnosed it myself, and can not see another reason for it happening, than that the groove on the photo has become to wide, or the small part entering the groove has become rounded and will not stay in the groove while playing a record.


Attachments:
Automatic brake (hand set) 2.jpg
Automatic brake (hand set) 2.jpg [ 420.19 KiB | Viewed 511 times ]
Automatic brake (hand set).jpg
Automatic brake (hand set).jpg [ 795.46 KiB | Viewed 511 times ]
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 Post subject: Re: The different HMV brakes/autobrakes
PostPosted: Tue Sep 22, 2020 2:12 pm 
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Victor IV
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Keep'em well oiled
Joined: Mon Dec 18, 2017 2:51 am
Posts: 1085
Location: Madrid, Spain
Nostalgia, I've suffered this problem with the preset brake as you! In my case it was what you say... The rounded or worn out parts that engage one another. I solved that by carefully filing out the rounded parts. The side of the finger that engages into the indent must be made rough again, as the side of the indent that holds it in place against the strength of the spring. This I roughened by careful filing with a very fine triangular hand file which ends in an acute point. The thing is so small... Besides that, you must try to make them match plane one against the other, for gaining retaining force. I don't know if I'm explaining clearly. If you examine carefully the areas that must be in contact to retain the brake opened, you'll arrive to this same conclusion. They must keep narrow contact and retain the brake until you touch the triggering fork. This little reshaping and filing solved my problem!
Another advice, be careful when oiling the brake... Less is better. The oil never must touch the retaining washers, as they work by friction. You should clean it with solvent or alcohol. If these washers slide too much, the brake will not work, as the fork moves the other parts thru these washers pressed all together by means of the top steel spring washer. You should oil very little the bearing of the main handle, far from the other bearing and the pressed together washers ... This is for all auto brakes!
Inigo


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 Post subject: Re: The different HMV brakes/autobrakes
PostPosted: Tue Sep 22, 2020 2:42 pm 
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Victor III
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Joined: Thu Jun 13, 2019 1:58 am
Posts: 730
Location: My gramophone repair room
Thank you Inigo, for all advice on this autobrake, another step forward in understanding this particular autobrake! This problem was actually the main reason for storing this HMV 109 last autumn, since it just was not ready for use !
And yes, I today when finally having another look at this gramophone, also felt it now was necessary to file these parts etc. Shared knowledge also for other restorers of gramophones with this autobrake!
I understand what you mean with being careful with oil, and keeping the parts of the brake at the same level, so they match each other, it all makes sense, but it also is very important information to take notice of, and write down here on the forum, as you did now.

Understanding and mastering the autobrakes, is a vital part of servicing the HMV gramophones, for sure.


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 Post subject: Re: The different HMV brakes/autobrakes
PostPosted: Sat Sep 26, 2020 10:37 am 
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Victor IV
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F. Depero, "Grammofono", 1923.
Joined: Thu Feb 24, 2011 4:19 am
Posts: 1065
Location: Italy
I made a short clip about the type 3 autobrake. Absolutely nothing to write home about (no understantement...) but since this model was addressed in this topic and I happen to own a unit, I thought that perhaps someone might find interesting few comments about it.

https://www.youtube.com/watch?v=m-M5JYfAsQE


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 Post subject: Re: The different HMV brakes/autobrakes
PostPosted: Sat Sep 26, 2020 12:01 pm 
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Victor III
Keep winding up
Joined: Thu Jun 13, 2019 1:58 am
Posts: 730
Location: My gramophone repair room
Marco, thank you so much for making and linking to this important video. I of course would not ask anyone to make a video, but since the beginning of this thread felt video(s) showing the functions and parts of the more complex autobrake(s), would be the best, and maybe even only way, to describe and understand how they are operating.
I also say thank you to both you and Inigo for trying to explain in words their operation in earlier posts, but a video like this is exactly what was needed, as I see it!
I hope it will be used in the weeks/months/years to come by collectors and restorers, since it is truly a wonderful way to remove the mysteries around how the HMV autobrakes operate, and what may be wrong if they not work. There are many videos online showing how to service main springs and motors, and servicing a motor is also much about keeping track of what you are doing, and then do it all in reverse when you are re assembling the motor. Understanding autobrakes, is however a very different thing, since they are more delicate, and far more detailed, and as earlier said..it all happen under the turntable.
Thank you again, and actually my unsaid wish was met with this video, that someone with the knowledge and technical understanding would create a video to show how they work ! For the first time I myself now completey understand what is going on when the autobrake no 3 is in operation! :clover: :)

PS. Also great to see and listen to your beautiful HMV 163 playing!


Last edited by nostalgia on Sat Sep 26, 2020 3:19 pm, edited 1 time in total.

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 Post subject: Re: The different HMV brakes/autobrakes
PostPosted: Sat Sep 26, 2020 2:09 pm 
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Victor III
Joined: Sun May 27, 2012 2:38 pm
Posts: 943
Location: United Kingdom
I also enjoyed the video, but with great respect, Marco, I don't think the gramophone is a 156? According to the gramophone "bible", the 156 has a completely different cabinet and a No.4 soundbox. Can you enlighten us, please?

Barry


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 Post subject: Re: The different HMV brakes/autobrakes
PostPosted: Sat Sep 26, 2020 3:06 pm 
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Victor IV
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F. Depero, "Grammofono", 1923.
Joined: Thu Feb 24, 2011 4:19 am
Posts: 1065
Location: Italy
Good grief, yes, of course it's an HMV 163... :| Oh Lord, what an annoyance... Does anyone know if that part can be dubbed without having to re-upload the clip again?


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