Author Topic: 775 Motor based Dynamo  (Read 999 times)

Offline Jasonb

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775 Motor based Dynamo
« on: December 21, 2024, 07:00:24 PM »
A quick little project that was prompted by a couple of threads on ME Forum where a member was having problems with a Stuart Dynamo where the field blocks were not cast centrally and the magnet a bit weak.

I decided to see if I could make something similar. So it's about the same size as the Stuart offering, looks a bit more like the PMR one at least from the brush end and also has the look of an old Motor/Dynamo with the radial slots at the other. It uses the rotor, magnets, bearings and brushes from an ebay sourced 775 DC Motor with a new body and end caps plus a few insulators and thumb nuts. Depending on what you have in the way of metal stock it would cost between £40 -50GBP including the motor which compares well to over £300 for the Stuart kit.

My old Stuart 10V was used as most people can relate to that. Air at around 30psi. I used the a bit of scrap with a couple of O rings stretched over it as the pulley and ran that against the 10V’s flywheel and a couple of calculations show the dynamo is running around the 3000rpm mark for the light, probably a bit less on the other items and you can certainly hear the engine working under load when it is driving the smaller DC motor. It would be better set up with a belt at say 1:5 reduction then the 10V could be run a bit slower, currently it is about 1:3. It can also still be run as a period looking motor.

<a href="https://www.youtube.com/watch?v=hP-bW8Y4_iU" target="_blank">http://www.youtube.com/watch?v=hP-bW8Y4_iU</a>


Offline Michael S.

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Re: 775 Motor based Dynamo
« Reply #1 on: December 21, 2024, 09:46:45 PM »
The new Dynamo looks very good. Very close to Stuart's original.
I'm thinking about giving my little Stuart a dynamo.

Michael

Offline redhouseluv

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Re: 775 Motor based Dynamo
« Reply #2 on: December 22, 2024, 02:34:18 AM »
I had to get a new permanent magnet for my Stuart Dynamo; that came to £61.50 including the tax and shipping! If you need a new armature, well......

Thats a great looking piece, I espeacially like the radial slots and would be superb driven with a belt
« Last Edit: December 22, 2024, 02:04:54 PM by redhouseluv »
Best regards

Sanjay

Offline Jasonb

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Re: 775 Motor based Dynamo
« Reply #3 on: December 22, 2024, 07:16:56 AM »
Thanks

The end plates can really be anything the builder wants them to be from just the top to bottom bar like the Stuart to any representation of an old motor or dynamo.

Even the casing could have been made from a piece of square stock and just the two top corners rounded and feet added then you have even more of a Stuart/PMR look

A few options

Offline mikehinz

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Re: 775 Motor based Dynamo
« Reply #4 on: December 22, 2024, 03:39:57 PM »
Jason, I really like your dynamo!  I've been thinking about building one from a casting kit, but your approach might be better for my needs.  Do you intend to make your plans available or should I just take inspiration from your video and do my own?? 

Again, great work!

Mike
MIke
Wichita, KS, USA

Offline Jasonb

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Re: 775 Motor based Dynamo
« Reply #5 on: December 22, 2024, 06:47:28 PM »
The intension was to write it up for Model Engineer Mag, but as there have been a few changes there I will have to see if it goes there or just on the web.

I'll try and remember you when the 2D drawings are done.

Offline mikehinz

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Re: 775 Motor based Dynamo
« Reply #6 on: December 22, 2024, 08:27:21 PM »
Jason, thanks very much!  if your build is published, let me know when.  And of course if you do make the drawings available, I'd very much appreciate them!

Mike
MIke
Wichita, KS, USA

Offline kuhncw

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Re: 775 Motor based Dynamo
« Reply #7 on: December 22, 2024, 11:34:00 PM »
Jason,

That is a very nice looking motor to dynamo conversion.

What was the overall length of the motor you used?

Chuck

Offline Jasonb

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Re: 775 Motor based Dynamo
« Reply #8 on: December 23, 2024, 07:14:44 AM »
Sizes below which seem fairly standard but best to pull your chosen motor apart and check before making parts.

Couple of sectional views which should show what is going on. The pockets either end take the bearings stripped from the motor but not drawn. Brushes are in their "relaxed" position hence they are not resting on the comutor. The notches in the square insulators stop the brushes from rotating when they are put under spring pressure.

Offline kuhncw

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Re: 775 Motor based Dynamo
« Reply #9 on: December 23, 2024, 02:39:09 PM »
Jason,

Thank you for sharing the section views and motor specs. 

Your dynamo makes a great project. Let us know when it is published.



Chuck

 

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