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Old 6th Aug 2020, 9:53 pm   #1
Dennis M
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Default Octopus test bench (For Dynamos and Magnetos)

Here's another odd machine I have got working recently, has a strange motor that can go from 6000rpm clockwise to 6000rpm without turning it off.
The brush carrier is rotated by bowden cables from a hand wheel on the front to change speed and direction.
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Old 6th Aug 2020, 11:35 pm   #2
MotorBikeLes
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Default Re: Octopus test bench (For Dynamos and Magnetos)

Dennis, it makes my dynamo tester look quite trivial. But mine is just a few components on an 18" square board. Fwd, rev,, dynamo output test, CVC adjust capability, contact breaker function and coil and plug checking.
Still not done my little demo video. - actually I did one, but volume too low, so need to repeat it.
Les.
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Old 7th Aug 2020, 10:25 am   #3
boxdoctor
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Default Re: Octopus test bench (For Dynamos and Magnetos)

In the early '50s, I had a short period of working in the electrician's shop of of a large local garage.
We had a Octopus machine, it did similar tasks, but was as far as I recall, a much larger model, and floor-standing. Also it had a grey finish.
There was a fearsome attachment for testing starter motor torque, consisting of a tool reminiscent of an adjustable spanner which one would attach to the motor under test's drive pinion, with a spring-loaded gauge at the other end. This measured the torque of the motor directly.
I hate to think what the consequences might have been it this assembly was not properly attached and checked before the test was carried out! No guards, as I recall.
Quite dangerous, I think. Tony.
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Old 7th Aug 2020, 10:36 am   #4
Dennis M
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Default Re: Octopus test bench (For Dynamos and Magnetos)

Mine has the spring balance rod and clamp for testing starter motors, when I get to use it I will make sure I stand back.
Might just make up a guard just to make sure I don’t hurt anyone.
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Old 7th Aug 2020, 11:19 am   #5
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Default Re: Octopus test bench (For Dynamos and Magnetos)

I think the one with the red case could also run up distributors to verify advance/revs curves as well as scatter.

An electro-mechanical swiss army knife!

Always wanted one.

David
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Old 7th Aug 2020, 11:19 am   #6
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Default Re: Octopus test bench (For Dynamos and Magnetos)

I remember seeing something similar but which was nicknamed "the growler" and had an AC-energized V-shaped coil onto which you put a motor armature then slowly rotated it. If there were shorted turns in the armature then the current induced in these would cause the armature to vibrate on the ends of the V-shaped coil and make a growling sound, hence the name.
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Old 7th Aug 2020, 12:15 pm   #7
Dennis M
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Default Re: Octopus test bench (For Dynamos and Magnetos)

I want to be able to rewind and recon my own magneto's and dynamo's, so I have been collecting kit.

Have
Octopus test bench ( Has got a rotating spark gap with a scale on it for checking advance curves)
Armature mica undecutter
Growlers
Home made ignition coil tester
Basic Avo coil winder
Vacuum / Pressure chamber for impregnating the coils

Am making a capacitor discharge magnetiser, capacitors charged up to 440V will give me a 175A pulse through the magnetiser coil.
That gives me 86000 amp turns so should recharge any of my magneto magnets nicely.

Only things that I need to find next is a good automatic coil winder and a stroboscope to check the point with.
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Old 7th Aug 2020, 3:30 pm   #8
pmmunro
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Default Re: Octopus test bench (For Dynamos and Magnetos)

Quote:
Originally Posted by Dennis M View Post
Here's another odd machine I have got working recently, has a strange motor that can go from 6000rpm clockwise to 6000rpm without turning it off.
The brush carrier is rotated by bowden cables from a hand wheel on the front to change speed and direction.
Dennis,

I think what you are describing is a repulsion motor. https://en.wikipedia.org/wiki/Repulsion_motor

I first met this type on a Bosch auto electrical test bench which I used betwen 1977 and 1979. Unfortunately I lost possession of it due to the recession of 1979 following the change of Government. It was considerably larger than the Octopus and arguably more sophisticated; similar to this https://www.gtautoelectrix.co.nz/sta...tor-alternator (ours did not have the ignition system testing adaptation shown on this one). The repulsion motor is the grey machine below the operator's left hand and the hand wheel on the vertical panel at the left of the bench moved the bowden cables to rotate the motor brushes and control speed and direction. The alternator, very occassionally a dynamo, under test was simply connected to the repulsion motor spindle through a rubber drive coupling and a half-inch square drive socket.

The great advantage of a test bench is the ability to test rotating machines under controlled conditions before refitting them to a vehicle, especially important when testing/repairing them for a thitd party. It must be more important now since so many modern cars have alternators or starter motors deeply hidden, needing long times to access. It's not unknown for factory exchange units to be faulty.

It's quite impressive to see a high output alternator start giving a substantial charging current (second meter from the left) at a few hundred rpm (centre meter) then winding it up to full output.

One type of alternator made by SEV often needed just 3 1N4007 doides to repair a fault. The exchange price charged by one of our trade customer's, a Volvo dealership, was around £90 which at the time was a lot of money. To give the retail customer better value for money we usually fitted new bearings and brushes at the same time knowing they would be charged for a reconditioned unit anyway.

PMM
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Old 7th Aug 2020, 8:33 pm   #9
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Default Re: Octopus test bench (For Dynamos and Magnetos)

Hi Dennis, good basic electrical engineering there that only starts to get a bit complicated with compound winding on dynamos and the later 3 bobbin regulators.
I may have a DAWE stroboscope here if you are interested.

Ed
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Old 7th Aug 2020, 11:07 pm   #10
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Default Re: Octopus test bench (For Dynamos and Magnetos)

At autojumbles of the 80's there was often a stand occupied by Bolton Magnetos who often had their test rig on the go. Looked rather archaic compared to yours, more frankenstein
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