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Old 21st Sep 2017, 6:09 pm   #1
AndyGilham
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Default AVO & Megger technical drawing scans

As I previously posted, I work for Megger (Formerly Avo) in Dover, where I have found cabinets of technical drawing microfilms.
Well, the good news is, all 38566 of them have been scanned into PDF. I have them indexed and in a spreadsheet. The oldest I have currently found is from 1919 (Evershed & Vignoles Megger tester) and those run upto and include the mid to late 70's.
The earliest AVO drawings seem to be around 1945. However, I have a lot to go through.
Some of the scans are fantastic quality, others not so much, due to the deterioration of the films.
Found some very interesting document. And for a little teaser, please see attached the original technical drawing for the AVOmeter Model 7 & 40 front panel released on the 4th May 1951 (Notice the reduced quality)

Andy
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Old 21st Sep 2017, 6:17 pm   #2
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Default Re: AVO & Megger technical drawing scans

Doh! Obviously I meant the AVOmeter Model 7 Mark 2 and Model 40 Mark 2!
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Old 21st Sep 2017, 6:21 pm   #3
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Default Re: AVO & Megger technical drawing scans

Are all, or even some, going to be available to us mere mortals? One could easily lose a few days browsing all of them!
 
Old 21st Sep 2017, 6:45 pm   #4
The Philpott
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Default Re: AVO & Megger technical drawing scans

I think that by 1951 they were starting to get some uniformity and repeatability. Before this it must have been frustrating to go to this amount of effort and precision at the design stage only to have perhaps 1 in 10 of the finished articles distort beyond acceptable limits while cooling down!

Thankyou again Andy, it's unusual to find a company that pays attention to it's heritage.

Microfilms have been around for an incredibly long time (in one form or another.) I was astonished to pick up a small victorian propelling pencil with a 1/8" diameter lens set across the top- peering through it there were 6 reasonable definition monochromes of Dawlish in Devon. All very James Bond.
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Old 21st Sep 2017, 6:48 pm   #5
AndyGilham
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Default Re: AVO & Megger technical drawing scans

The company intends to create a heritage centre (museum) on site, here in our Dover factory, and a PC containing the searchable drawings should be available with it.
However, I am not sure the plans with regards to uploading to the internet. Only time will tell.
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Old 21st Sep 2017, 7:06 pm   #6
Lloyd 1985
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Default Re: AVO & Megger technical drawing scans

Hi,
Its great to see the technical drawing of the model 7, I picked one up in an antiques shop last weekend, in lovely condition with some leads and a nice leather case. Unfortunately the pointer gets stuck part way across the scale, so it's probably not going to work I would open it up and see if I could do anything with it, but it's still got a wax seal over one of the screw heads, and I don't want to disturb it! It's a lovely piece of kit, even just to have on display!

Regards,
Lloyd
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Old 21st Sep 2017, 7:56 pm   #7
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Default Re: AVO & Megger technical drawing scans

Lloyd it could be a piece of ferrous swarf obstructing the movement. (Sucked towards the magnet and can't escape without help)

From my own perspective if there's something wrong inside the factory seal has to go! It's generally quite a gritty consistency so it's easy to chew the screw head up unless all the black stuff has been diligently removed from the slot. Your choice of course!
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Old 21st Sep 2017, 8:34 pm   #8
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Default Re: AVO & Megger technical drawing scans

The drawing is a reminder to the cad-cam generation that manufacturing was even more hands-on than it is today.
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Old 21st Sep 2017, 8:50 pm   #9
AndyGilham
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Default Re: AVO & Megger technical drawing scans

When I started working at avo's in 1994 there was still a drawing board in the office. Even at time I would say that 15% of our products manufactured were still on hand drawn documentation. I would spend my Friday morning die line printing A0 drawings for tool manufactures and assembly drawings for production!
And PCB artwork tape masters were a thing of beauty!

It's a lot easier with the CAD software we use now, because detailed technical drawings are uneccessary when you can output a 3D model of the design. The skill of producing an injection mould tool from a drawing is quite impressive! Not only thinking in 3 dimensions, but also in negative!
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Old 4th Oct 2017, 10:32 am   #10
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Default Re: AVO & Megger technical drawing scans

Hi Andy,

Proper drawings - things of beauty indeed. Happy memories of Technical Drawing at school all those years ago!

A resounding chorus of 'three cheers' to your company for deciding to preserve these records.

I'd be interested to learn how such a large number of records (especially the microfiche ones) have been scanned into PDF format - ?

Best wishes
Guy
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Old 4th Oct 2017, 6:00 pm   #11
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Default Re: AVO & Megger technical drawing scans

Hi Andy,

I think I may have spoken with you when I worked up in Aberdeen.

I have a question but will send a PM

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Old 6th Oct 2017, 2:20 pm   #12
AndyGilham
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Default Re: AVO & Megger technical drawing scans

Nymrod121
It's great that my company have shown this interesting, and are essentially funding my own interest in the history. So, yes I can see years of data collection ahead of me and it's already beginning with some interesting finds.
I managed to find a company whose business is scanning, and they took all 38,000 films and scanned them one by one, checked the quality, and indexed them I a spreadsheet with part Humber, revision and description. They use high end desktop microfilm scanners. It's an impressive set-up.

See_Mos
Thank you for the PM. Read and responded!
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Old 6th Oct 2017, 3:30 pm   #13
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Default Re: AVO & Megger technical drawing scans

Is it possible to get a diagram for my 1943 Megger?
All I have is a serial number and a date for the movement.
It is a non generator model.
It works well with a 7.2V to 500V inverter that fits without modifying the case.
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Old 13th Dec 2017, 3:57 pm   #14
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Default Re: AVO & Megger technical drawing scans

Andy a work of art! I wonder how long it took to draw??
What size paper is the original on?
Surely it would have been a nightmare to draw that at 1:1
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Old 16th Dec 2017, 11:28 pm   #15
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Default Re: AVO & Megger technical drawing scans

Andy, can you get drawings of the coil assemblies?
I have an Avo7 here in which the movment is in need of tlc and it seems rather complicated.
It appears as if the actual needle attaches to a plate which has provision for a degree of rotational freedom about the upper pivot pin.
It would seem that in a clockwise sense the needle butts up against a stop that is part of a plate (P1) that is glued? to the underside of the top of the coil. This stop would represent the clockwise-most position ( and the normal? position) of the needle relative to the coil.
A very fine leaf spring, attached to the coil and perhaps a conductor?, presses against the anticlockwise side of the needle via a tab carried on a plate (P2) which in turn freely pivots about a point on P1. This spring applies a clockwise force to the needle which in normal circumstances, I assume, is meant to hold the needle against the stop mentioned earlier. However the arrangement would allow the needle to move temporarily anticlockwise wrt the coil if the coil were subject to a clockwise directed acceleration or anticlockwise directed decceleration before returning the needle to its rest position wrt the coil i.e. it acts as a bit of a shock absorber.
To complicate matters, on the opposite end of P2 from the 'needle tab' is another tab which whilst typing this I have come to suspect might engage in the saw toothed edge of dish shaped plate that from memory sits on the stationary core of the coil and might engage with the cut out trips.
Perhaps this latter part of the mechanism is intended to trip the cut out irrespective of the coil's position
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Old 17th Dec 2017, 12:24 am   #16
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Default Re: AVO & Megger technical drawing scans

i think the assembly you refer to towards the end of your post, is the acceleration cut-out. This is not fitted to all meters but i think it is fitted to the model 7. The biggest problem with rectifying a dodgy movement is ascertaining what exactly the problem is; i have won some and lost some in this respect. I haven't delved as deeply into an individual mechanism as you are doing, it would be interesting to know what the problem is and whether you are able to solve.
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Old 17th Dec 2017, 2:41 am   #17
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Default Re: AVO & Megger technical drawing scans

Part of the problem is that I am not sure what the problem is but I'd also like to know if I have correctly imagined what the mechanisms are supposed to do.
The needle some times doesn't zero after taking a measurement but stops before it gets back to zero as if it hit something solid and it's not behaving as if it were a piece of trapped debris occasionally catching.
I half suspect the movement has been played with, as the plate which 'covers' the pivots of the cut out levers seemed askew and its screw was loose. Also the point of contact between the 'needle tab' and the very fine leaf spring is VERY close to the end of the spring and I wonder how much needle movement would be required for the spring to slip out of place.
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