Author Topic: Retlas "Manchester" Dynamo  (Read 15686 times)

Online steam guy willy

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Re: Retlas "Manchester" Dynamo
« Reply #105 on: January 02, 2021, 02:05:33 AM »
Hi Willy.

I'm absolutely clueless, all I remember is that it was built in 1959, oh and a knuckle whitening ride in the chair....

The funniest moment was when Martin rolled onto a Petrol station forecourt with the sidecar literally covered in ice up to its waistline. He discovered that the bottle of Propane he was carrying had, had the valve knocked open and the liquid gas froze everything. The whole station was immediately in panic and the local Fire brigade called to deal with the emergency. Those were the days lol....

Hi, this is my BMW outfit and yes left hand bends are deadly  this was a few years ago and so the excitement is still happening !!!

Offline Alyn Foundry

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Re: Retlas "Manchester" Dynamo
« Reply #106 on: January 02, 2021, 12:13:06 PM »
Good morning Willy.

That's a lovely photograph.

You asked if it was an Earls fork, would there have been a largish Black plastic handwheel between the top fork clamps? This is one of the few things I remember about Martin's BMW. The only other thing I remember was that he had fitted an hydraulic brake lever just where your left foot is resting in the photo.
This was for " emergency " stops with a probably seriously overloaded sidecar. As time progressed he fitted a tow hitch and pulled a small, homemade trailer.

The BMW was his main transport having never passed his car driving test. He also ran a Yamaha RD 400 for fun. When his children came along the BMW was changed for a Reliant three wheeler and like all of Martin's vehicles got heavily modified to suit his tastes. The White one turned from a car to a pile of ash in just 20 minutes due to a carb " spit back " despite our valiant efforts with a couple of fire extinguishers.

Cheers Graham.

Offline Chipmaster

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Re: Retlas "Manchester" Dynamo
« Reply #107 on: January 30, 2021, 05:11:15 PM »
I haven't been able to spend much time on model engineering lately and my projects are rather delayed.
However, here are some recent pictures of the dynamo mounted on a temporary wooden base. It now has six home made brass terminal posts mounted on the hardwood top, a two inch aluminium pulley and is paired up with the Retlas engine. 

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Here's a video of the dynamo being driven by the engine.

<a href="https://www.youtube.com/watch?v=FN4ARGutcls" target="_blank">http://www.youtube.com/watch?v=FN4ARGutcls</a>

The first part of the video shows the dynamo generating approximately six volts when driven by a flat belt on the engine's eleven inch flywheel. My multimeter was set to fifteen volts full scale deflection which can be seen on the video at times - unfortunately the quality of the video is poor. With this set up the engine didn't run well and struggled to pick up speed. The dynamo was running at approximately 575 to 600 rpm when it produced 6 volts, I couldn’t measure current because the fuse in my multimeter had blown.
The engine handled the load with ease when I used it's three and a quarter inch diameter pulley to drive the dynamo. At the reduced speed of 400rpm the dynamo produced approximately two volts / one amp and can be seen powering five 2.2V bulbs wired in parallel.
I didn't know how the dynamo should perform at these low speeds but I found this video of a C40 dynamo being bench tested interesting (same armature that I used). Half way through the video he appears to get 1.39 volts at about 600 rpm and 13 volts at 1,179 rpm. My dynamo appears to doing well by generating 2 volts.

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

Occasionally the engine runs away and things get rather hairy as it violently jumps and shakes whatever it’s clamped on. When it runs away the bulbs become much brighter as expected but it’s like a white knuckle ride and I had to kill the engine without noting the meter readings. I haven’t worked out why the Retlas occasionally runs away when it is driving the dynamo. Anyway it’s a good job I fitted a kill button in the ignition circuit. The Retlas engine runs very nicely at speeds of up to 600 rpm so I want to try a larger pulley. A cast iron Mini brake drum will be the basis of a larger pulley attached to the flywheel because there there isn’t much crankshaft projecting beyond the flywheel hub.

Here are two views of the current 3.25" diameter pulley that I machined from cast iron bar followed by the 7" diameter Mini brake drum which cost only £14.75 including post on eBay. Hope this will be an easier way to machine a larger diameter crowned pulley but waiting for delivery of a 125 x 6mm disc to machine a flange that will fit in the centre of the drum.









Andy

Offline Roger B

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Re: Retlas "Manchester" Dynamo
« Reply #108 on: January 30, 2021, 05:32:07 PM »
Good stuff  :praise2:  :praise2:  :wine1:

I hope you can sort out why the engine runs away on load  :headscratch: Something in the governor sticking when it is running in a different range  :thinking:

When you get things settled it will be interesting to see the effect of having the field coils in series and parallel  :)
Best regards

Roger

Offline Chipmaster

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Re: Retlas "Manchester" Dynamo
« Reply #109 on: January 30, 2021, 07:05:54 PM »
Hello Roger, thanks for your post. There are a few areas both mechanical and electrical that can be tuned so it may take a while for me to achieve optimum results, warmer weather and more time is required.
I prefer to have the engine gently chugging in the range up to 600 rpm so I hope it will cope with the seven inch diameter pulley. I’m happy to have an unstressed engine/dynamo set up powering a string of low voltage light bulbs but I would prefer an output closer to six volts if possible.
The ‘running away’ phenomenon is perplexing, the engine has been a docile runner since I built it a few years ago. I’ll try to focus my handycam on the governor if it runs away again and perhaps watching the video in slow motion will enable me to sort it out. The engine gets much hotter now it’s doing some work, could that be a factor?
Andy

Offline Alyn Foundry

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Re: Retlas "Manchester" Dynamo
« Reply #110 on: January 30, 2021, 07:23:44 PM »
Hi Andy.

Absolutely stunning display, that should turn a few heads at any function, very well done.   :cheers:

I'm surprised to read that your Retlas is running so fast but if it's happy at that speed then it's probably OK. So some simple mathematics should get you at the 2000 RPM required at the Dynamo pulley.

You might recall our recent telephone conversation when I asked you about ignition advance and retard? You said it didn't make much difference, that was also a surprise to me. However, you're using an electronic ignition system, could the magnet be too strong so as you can't make adjustments? Just a thought....

Cheers Graham.


Offline Chipmaster

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Re: Retlas "Manchester" Dynamo
« Reply #111 on: January 30, 2021, 09:13:27 PM »
Hi Graham, thanks for the posting, nice of you to say that  :ThumbsUp:
It has also become quite a heavy display, not far off taking a small engine to a stationary engine rally thank goodness it won’t need a trailer.

I hope I’m reading my rev counter correctly, I’ll check it tomorrow. Without driving something the engine normally runs at between 350 to 400 rpm if it goes past 600 rpm it becomes too lively. What speed do Retlas’s run at in your experience?

If the man testing his C40 dynamo in the YouTube video generated 13 volts at 1179 rpm I’m hopeful the engine will have the power to run the new seven inch pulley at 400 rpm and drive the two inch dynamo pulley at 1400 rpm ... in theory.

My set up permits adjustment of the ignition timing up to 90° BTDC and about 30°After TDC . While the engine is running I can adjust it to the extent that the engine stops running,  It surprises me the range of ignition timing that the engine will run with. The setting does affect whether you get the knocking/pinking sound or a very docile tick over. I’ll try to stage a video to demonstrate.
Cheers
Andy

Online Twizseven

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Re: Retlas "Manchester" Dynamo
« Reply #112 on: January 30, 2021, 09:39:47 PM »
Andy,

You have made a fantastic job of that dynamo.  It looks stunning with the engine belted up.  Hope you sort your overspeed issues.

Regards,

Colin

Offline Chipmaster

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Re: Retlas "Manchester" Dynamo
« Reply #113 on: January 30, 2021, 10:21:22 PM »
Thanks for the compliment Colin.
I'm pleased that it generates, even if it's only a couple of volts at a low speed.

Andy

Offline Alyn Foundry

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Re: Retlas "Manchester" Dynamo
« Reply #114 on: January 31, 2021, 11:48:35 AM »
Hi Andy.

Don't worry about a demo, it seems I misunderstood your remarks. The timing is adjustable but doesn't seem to have much effect, correct?

The 350/400 RPM range is good even slower would be better as the crankshaft doesn't have any counterbalance weights.

Cheers Graham.

Offline Chipmaster

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Re: Retlas "Manchester" Dynamo
« Reply #115 on: March 05, 2021, 10:19:39 PM »
During the current cold weather it's impractical to use the Retlas gas engine to drive this dynamo in my garage with the doors closed so I decided to test drive the dynamo using a spare single phase electric motor from my Meddings pillar drill. The motor runs at 1500 rpm which seems a reasonable speed for the dynamo. A two inch diameter crowned aluminium pulley was machined and held on the motor shaft by two 1/4" whit grub screws spaced at 120 degrees. The dynamo pulley is also two inches in diameter.

Here's a YouTube video of the dynamo this afternoon March 5th.

<a href="https://www.youtube.com/watch?v=bjpAj8K0wtk" target="_blank">http://www.youtube.com/watch?v=bjpAj8K0wtk</a>

The dynamo is turning at 1500 rpm, the old analoge multimeter recorded 10 volts and the LCD multimeter recorded a high of 4.7 amps with the Armature Reaction Compensator adjusted for the optimum output. It was interesting to hear the effect of changing the load on the dynamo by adding and removing bulbs - the whine increased with the load. It was good to see the ring oilers doing their job and not flinging oil out of the chambers which happened when I 'motored' the dynamo and it reached about 2000 rpm - covers for the oil chambers required.

I was impressed with the brightness of the bulbs, only after the test did I find I had been using six instead of twelve volt bulbs, no wonder they heated up so quickly.

The dynamo seems to be performing very well nothing gets warm - windings or bearings and I haven't seen any sparks from the copper braid brushes so I must tidy the model up finish the details and paint it. I also need to devise a suitable base for mounting the model, wood is probably the easiest.

Andy

 
« Last Edit: March 05, 2021, 10:54:24 PM by Chipmaster »

Offline Chipmaster

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Re: Retlas "Manchester" Dynamo
« Reply #116 on: May 19, 2023, 09:36:23 PM »
Pictures of the dynamo in its finished state. I should have posted these last year.

 IMG_E3762 by Andy, on Flickr

Clipboard01 by Andy, on Flickr

Clipboard02 by Andy, on Flickr

Clipboard04 by Andy, on Flickr

Online Kim

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Re: Retlas "Manchester" Dynamo
« Reply #117 on: May 19, 2023, 11:12:41 PM »
That's beautiful!  I love the wood, brass, and black that you've used.  It looks great together like that!  :ThumbsUp: :popcorn:
 
Kim

Offline Alyn Foundry

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Re: Retlas "Manchester" Dynamo
« Reply #118 on: May 20, 2023, 01:04:21 PM »
Many thanks for the pictures Andy.  :ThumbsUp:

It’s great to see the final results. How many have been “ fooled “ with regards to its age I wonder?

 :cheers:  Graham.

Offline Roger B

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Re: Retlas "Manchester" Dynamo
« Reply #119 on: May 21, 2023, 07:02:20 AM »
Looks magnificent   :praise2:  :praise2:  :wine1:

Have you driven it with the engine yet?
Best regards

Roger

 

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