Author Topic: Bicycle Dynamo powered by model I.C. engine  (Read 13886 times)

Offline Brian Rupnow

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Bicycle Dynamo powered by model I.C. engine
« on: November 25, 2014, 05:22:33 PM »
Today I tested the bicycle generator (dynamo) that was sent to me by a fellow member. Not knowing what voltage this thing produces, and not having a voltmeter, I robbed a 2.9 volt rated battery out of a flashlight and jerry rigged a pigtail and alligator clamp to the bulb and the output terminal of the dynamo. I have a small cogged drive belt that I salvaged off something, and holding a 1" pulley in the milling machine chuck and pulling the belt tight I was able to light the flashlight bulb.  This satisfies me that the dynamo does indeed produce electricity. It did need to be rotating at a pretty respectable rpm to light the bulb, but I don't have actual figures on the rpm.  I intend to machine a 0.8" diameter flat pulley with side flanges on it to press fit onto the knurled end of the dynamo, and use the same belt that is in the picture to drive the dynamo from the 2" diameter starter hub on my side valve engine. This will give me a ratio of 2.5:1, so if the engine is rotating at 1500 rpm, the dynamo will be revolving at 3750 rpm. I have to design and fabricate a mounting base for the dynamo and a belt tightening mechanism, as I want the dynamo and its base to be a "composite unit" separate from the engine.--Stay Tuned!!!


Offline Brian Rupnow

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Re: Bicycle Dynamo powered by model I.C. engine
« Reply #1 on: November 25, 2014, 07:45:07 PM »
I think I have most of this sussed out now. I have a short length of 24DP rack left over from when I built the sawmill, and I will build the mounting plates from 3/4" aluminum. The sprag will be a bit of 1/4" square steel key stock. I want to be able to start the engine with the belt loose under "no load" conditions, then tighten the belt gradually until the revs come up on the dynamo. The sprag will hold the belt tight. I haven't modeled the release mechanism yet. I have to go out and buy a bulb and holder yet.


Online Roger B

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Re: Bicycle Dynamo powered by model I.C. engine
« Reply #2 on: November 25, 2014, 07:53:04 PM »
That's a much more sophisticated system than I used (a piece of wood pivoted on a woodscrew)  ::)

Having tried this with a much smaller capacity engine (2.5cc) many years ago I am following with interest  :ThumbsUp:  :ThumbsUp:
Best regards

Roger

Offline Steam Haulage

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Re: Bicycle Dynamo powered by model I.C. engine
« Reply #3 on: November 25, 2014, 08:39:12 PM »
Hi Brian,

These dynamos were designed to be powered by the bicycle rider, the faster you (or me whilst I was at school) pedalled the brighter the light. The power is transmitted to the dynamo by the serrated rotor pressing on the sidewall of the tyre by means of a spring mounting. The mounting for the dynamo would have facilities to hold the rotor away from the wheel in daylight hours. In the winter months the police would be enforcing the lighting regulations. For getting to school battery lamps were beyond the average schoolboy's funding capabilities and these units were very common. Tyres were available with a track moulded into the side wall, without this you could go through a tyre in a couple of winters. There are still some in use for their original purpose.

To find the necessary speed think of the serrated drive rotor against a 24 inch diameter bike wheel with the bike moving at a maximum of 30 mph, ( UK speed limit in built-up areas) to get the speed in sfm and work from there. :(

I'm afraid the sums are beyond me at this time in the evening.

Jerry :old:
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Offline Nerdz

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Re: Bicycle Dynamo powered by model I.C. engine
« Reply #4 on: November 25, 2014, 10:36:24 PM »
For what its worth, why not use a 1/4-20 "lead screw" to adjust tension?
-Chris

Offline mklotz

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Re: Bicycle Dynamo powered by model I.C. engine
« Reply #5 on: November 25, 2014, 11:23:38 PM »
Quote
I'm afraid the sums are beyond me at this time in the evening.

circumference of wheel = pi *24 in = 2*pi feet

30 mile/hr * 5280 feet/mile * 1/60 hr/min * 1/(2*pi) revolutions/foot = 420 rpm
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Offline Allen Smithee

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Re: Bicycle Dynamo powered by model I.C. engine
« Reply #6 on: November 26, 2014, 12:02:02 AM »
I've made several on-board generator systems for large model aeroplanes simply using a cheap brushless outrunner motor and three diodes connected to a regulator circuit. The idea was to enhance safety by making the on-board batteries a back-up system rather than the primary flight control power supply. It's very easy to do, and you can simply select a motor which produces the required voltage at (say) 20% engine rpm. The biggest one I did could deliver 30A at 6v (one on each engine of a 170" span, 90lb AUW B26 being built by a friend as a commercial order for a wealthy colonial customer) to drive a total of 29 servos, an electro-hydraulic retractable undercarriage system, landing/nav lights and the ignition systems of the two engines via four isolated DC power busses. These were simply driven with tothed belts from a ring-sprocket behind the prop driver of each engine. We did consider trying tio make them starter/generator units, but that would have needed a much chunkier belt system and we were tight for space, so we didn't bother.

The model has been flying reliably for five years now, and the customer reports that the onboard generators have made it much less sensitive to battery health (which has been an issue on several of his other large models).

AS
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Offline Brian Rupnow

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Re: Bicycle Dynamo powered by model I.C. engine
« Reply #7 on: November 26, 2014, 12:06:16 AM »
I made the pulley and pressed it on. That went well, but the pulley was so smooth the belt slipped badly. Next trick was to go all around the pulley with my automatic punch and "upset" the metal to give a little something for the belt to grip. If I was smart instead of good looking, I would have knurled it while it was still in the lathe.---Nah, that wouldn't have worked. I just checked and the knurling tool is too wide to fit between the flanges.

Offline Brian Rupnow

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Re: Bicycle Dynamo powered by model I.C. engine
« Reply #8 on: November 26, 2014, 03:14:38 PM »
There was a bit of method to my madness!!! By building and installing the pulley first, I was able to start the engine this morning and drive the dynamo via drive belt from my engine itself. Remember, the only test done previous to this was to drive the dynamo from my milling machine arbor. At any rate, even at half throttle the engine doesn't even grunt, and the lightbulb lights up like the lighthouse at Rhodes!!!---A very positive result!!! I needed to check this out before I wasted time building any of the other parts. Now that I know the engine drives the dynamo with no problem, I can proceed.
« Last Edit: November 26, 2014, 03:27:17 PM by Brian Rupnow »

Online Roger B

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Re: Bicycle Dynamo powered by model I.C. engine
« Reply #9 on: November 26, 2014, 03:49:26 PM »
 :ThumbsUp:  :ThumbsUp:
Best regards

Roger

Offline Nerdz

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Re: Bicycle Dynamo powered by model I.C. engine
« Reply #10 on: November 26, 2014, 05:28:14 PM »
Im curious to know how much current/voltage it produces under different loads. You pretty much have a small back up generator.
-Chris

Offline Brian Rupnow

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Re: Bicycle Dynamo powered by model I.C. engine
« Reply #11 on: November 26, 2014, 08:17:33 PM »
I believe everything that has been said about the effort to pedal a bicycle with one of these installed on it. I used to own one many years ago. Fortunately, the engine seems to run it with no problem.

Offline Brian Rupnow

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Re: Bicycle Dynamo powered by model I.C. engine
« Reply #12 on: November 27, 2014, 10:15:36 PM »
I am always pleased when whatever I build looks like the 3D model. The only change I made is that I didn't but the large radius on the bracket holding the dynamo, because I may need it to have a flat top for mounting the bulb. I haven't totally worked that out yet, but I will tomorrow. So far--So good!!!


Offline ths

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Re: Bicycle Dynamo powered by model I.C. engine
« Reply #13 on: November 28, 2014, 12:22:21 PM »
I like that belt tensioning system Brian, very neat indeed. Hugh.

Offline Brian Rupnow

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Re: Bicycle Dynamo powered by model I.C. engine
« Reply #14 on: November 28, 2014, 02:35:30 PM »
Thanks Hugh---Of course there is more to this than just mounting the dynamo itself. The squeeze bolt is going to morph into a handle, and I have added a bulb, bulb socket, and bulb socket support. The only remaining unknown is the release handle for the sprag.

Offline Brian Rupnow

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Re: Bicycle Dynamo powered by model I.C. engine
« Reply #15 on: November 28, 2014, 05:22:00 PM »
The bulb holder is just a bit tricky. It has to contact the outer shell of the bulb, but not the center contact. Since I don't have any Corian, I will fall back on the "hillbilly" insulator and turn one from a piece of hardwood. The insulator will epoxy into the end opposite to the bulb and have a 3/32" hole through the center for the contactor wire which gets the electricity from the dynamo up to the end of the bulb.


Offline Brian Rupnow

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Re: Bicycle Dynamo powered by model I.C. engine
« Reply #16 on: November 28, 2014, 06:12:10 PM »
The engine has a throttle on it so I can run it at a reasonably low rpm. The bulb I have is out of a flashlight with two D cells in it, so is basically a 3 volt bulb. The dynamo probably puts out 6 volts at peak rpm. Now in a perfect world, I would be able to get a 6 volt bulb with the same diameter base as the 3 volt bulb, but the world is seldom perfect. There is a blizzard going on outside at the moment, but I think perhaps I will mush my Huskies down to Ideal Supply and see what sizes (if any) their 6 volt bulbs are before I go any farther.---Brian

Offline Brian Rupnow

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Re: Bicycle Dynamo powered by model I.C. engine
« Reply #17 on: November 28, 2014, 06:46:03 PM »
Well I'll be----Sometimes ya just get lucky. The hardware store had 6 volt bulbs with the same sized base as the 3 volt flashlight bulb I based my bulb holder on. I must have done something right in a previous life----I have absolutely no idea why the package says 6 volt lanterns at the top of the package and 4.8 volts at the bottom of the package.

Online Roger B

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Re: Bicycle Dynamo powered by model I.C. engine
« Reply #18 on: November 28, 2014, 07:13:36 PM »
I would guess that these are for the  hand lanterns that take the big square 6V battery with the springs on top. Although the voltage is nominally 6 it will drop under load hence the 4.8V to give good brightness even as the battery ages.
Best regards

Roger

Offline Brian Rupnow

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Re: Bicycle Dynamo powered by model I.C. engine
« Reply #19 on: November 28, 2014, 08:44:17 PM »
So---If I just had a handle to disengage the sprag when I want to loosen the belt, I think I would almost be done.  I have spent the day playing and have grandchildren coming to visit overnight, so I won't get back to this today. I also got a "good news" phone call from a customer who wants me to design a packaging machine for one of his products, so I will be gainfully employed for a week or so.

Offline philjoe5

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Re: Bicycle Dynamo powered by model I.C. engine
« Reply #20 on: November 28, 2014, 09:38:30 PM »
Brian,

This is all very much interesting to me as I'm fascinated by generators.

I'm interested in what the "guts" of the sprag look like.  Any chance you'll be posting drawings for them?


Cheers,
Phil
If you pick up a starving dog and make him prosperous, he will not bite you. This is the principal difference between a dog and a man.  - Mark Twain

Offline Brian Rupnow

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Re: Bicycle Dynamo powered by model I.C. engine
« Reply #21 on: November 28, 2014, 10:50:13 PM »
Philjoe--I can do that. The sprag isn't very exciting--It's just a piece of 1/4" square steel bar with a 1/8" pivot hole thru one end and a taper on the other end. It is the sprag that engages with the teeth on the rack to hold the belt tight. --Is that what you meant?

Offline philjoe5

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Re: Bicycle Dynamo powered by model I.C. engine
« Reply #22 on: November 29, 2014, 02:47:56 AM »
Brian,
I get the steel bar engaging the rack but what puts tension on the belt?  Is it just a matter of moving the lever to tighten the belt, then engaging the bar in a tooth on the rack?

Cheers,
Phil
If you pick up a starving dog and make him prosperous, he will not bite you. This is the principal difference between a dog and a man.  - Mark Twain

Offline Ian S C

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Re: Bicycle Dynamo powered by model I.C. engine
« Reply #23 on: November 29, 2014, 10:49:00 AM »
With my hot air engines I started off using 3V bulbs on the generator, when the motor became freer, and I'd burned out all the 3v bulbs, I went to 6V, then to 12V, and although the 12V ones don't quite get to full brilliance, they at least last a little longer.  With your bike dynamo you should exceed 6 V, the thing is to get a low wattage bulb, then the motor won't have to work so hard,  you could use a number of bulbs with switching so you can load the motor.  Using amps, and volts, and rpm you have some idea of the power out put as the generator is working in place of a Prony Brake.  The generator will only be about 50% efficient, so if you get 50 Watts, the motor is nearer 100 Watts.
                                           Ian S C

Offline Brian Rupnow

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Re: Bicycle Dynamo powered by model I.C. engine
« Reply #24 on: November 29, 2014, 02:04:24 PM »
Brian,
I get the steel bar engaging the rack but what puts tension on the belt?  Is it just a matter of moving the lever to tighten the belt, then engaging the bar in a tooth on the rack?

Cheers,
Phil

You are correct Philjoe. I put tension on the belt by pulling back on the handle to rotate the mount holding the generator. The belt gets tight and gravity pulls the sprag down to engage with a tooth on the rack, holding the belt tight. I still have to make a release handle to disengage the sprag for when I loosen the belt.

Offline Brian Rupnow

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Re: Bicycle Dynamo powered by model I.C. engine
« Reply #25 on: November 29, 2014, 03:02:52 PM »
Yes!!! We have a sprag release handle. Nothing too scientific here--just something to disengage the sprag from the rack so I can loosen the belt off when I want to.

Offline Brian Rupnow

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Re: Bicycle Dynamo powered by model I.C. engine
« Reply #26 on: November 29, 2014, 08:23:32 PM »
So, here we have a view from the rear, with everything wired up. I just tested it on the mill spindle, and it seems to work the way I intended it to (the bulb does indeed light up). One of the things you see from this side is the tapped #5-40 hole in the side of the socket which holds the bulb in place. It has a set screw in there with a very light pressure against the base of the bulb, just to ensure that I have a good path for the electricity to flow.  What you don't see is the wooden insulator that sets inside the bulb socket to keep the electricity from shorting out and finding a path to ground through the aluminum holder. The bulb holder is press fitted into the 1" x 3/16" flatbar which bolts to the top of the dynamo bracket. At this point all that is left to do is make a video of the engine driving the dynamo and lighting the light.

Offline Brian Rupnow

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Re: Bicycle Dynamo powered by model I.C. engine
« Reply #27 on: November 29, 2014, 09:57:22 PM »
And away we go!! Everything went very well on this project, except for one surprise. If the dynamo turns one direction, it runs fine and freely. If it turns in the opposite direction, it tightens up inside and becomes very stiff to turn. My original plan was to have the engine setting on the left hand side of the engine with the pulley facing out. The result was that the dynamo would tighten up to the point where it stalled the engine. So---I turned the dynamo 180 degrees and put it on the right side of the engine. That reversed the rotation and fixed the problem, and it works like a charm. The bulb I have in there is only rated at 2.9 volts, so I bought two "back-up" bulbs for a 6 volt light in case I need them.
<a href="https://www.youtube.com/watch?v=xP1bOhvse8Q" target="_blank">http://www.youtube.com/watch?v=xP1bOhvse8Q</a>

Offline b.lindsey

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Re: Bicycle Dynamo powered by model I.C. engine
« Reply #28 on: November 29, 2014, 10:32:56 PM »
Nicely done Brian!!  Its nice when things work just as you expect them to :)

Bill

Offline Brian Rupnow

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Re: Bicycle Dynamo powered by model I.C. engine
« Reply #29 on: November 30, 2014, 01:29:15 AM »
I may have learned something here about the Chuck Fellows carburetor which I built and installed on this engine. The carb works great, and I recommend it to anyone looking for a simple, easy to build carburetor with a "throttle" on it. The carb I built is from one of Chuck's early designs, with a #8-32 screw acting as the throttle. By turning the screw in, it closes off the 1/8" diameter main air passage, and by unscrewing it, the air passage is opened, thus letting more air (and venturi induced fuel flow) into the engine. I took matters a step farther, and made up a little handle to clamp on the head of the #8-32 socket head cap screw, so that with an arc of about 180 degrees swing I can go from idle speed up to a much higher engine speed.---And that works fine, as long as there is NO LOAD on the engine. However, when the engine is under a load, it doesn't want to rev very high. I thought about this for a while, and come up with the following theory---An 8-32 thread only advances (or retracts) 1/32" for a full 360 degrees of turn. The 180 degrees of arc I am limited to with my "throttle handle" only advances (or retracts) the screw 1/64". Now on an engine running under "no load" conditions, that 1/64" is enough to go from idle to quite a respectable "high" rpm. However, in an engine running under a load, that 1/64" simply isn't enough to feed the fuel and air the engine requires to overcome the "load" and rev higher. The main air passage on the carburetor I built is 1/8" diameter. To really feed the engine the fuel and air it needs to rev higher under a load would require that the screw be unwound possibly a full turn or even 2 or 3 turns. This is all just theory at the moment, but tomorrow I will do a practical test and remove my "throttle handle" and see what happens when the engine is running under the load of the generator and I unwind the screw more than the 1/2 turn I am currently limited to. In the video I posted, the engine is running with the throttle "wide open" within the limits imposed by the swing of my throttle handle.

Offline Stilldrillin

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Re: Bicycle Dynamo powered by model I.C. engine
« Reply #30 on: November 30, 2014, 09:05:12 AM »
Very well done, and shown, Brian! 

I've enjoyed following this whole, generator saga.  :praise2:

David D

David.
Still modifying bits of metal... Occasionally, making an improvement!
Still drilling holes... Sometimes, in the right place!

Offline Brian Rupnow

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Re: Bicycle Dynamo powered by model I.C. engine
« Reply #31 on: November 30, 2014, 05:57:37 PM »
For what it's worth--after spending some time adjusting the carburetor, I ended up with the following results. The top engine rpm with no load on it is 1900 rpm. When the slack belt is in place, it puts enough frictional load on the engine that the rpm drops to 1780 rpm. When the belt is fully tightened and the generator is lighting the light very brightly (2.9 Volt bulb), the rpm drops off to 1467 rpm. The finished diameter of the driving and driven pulleys is 2.0" and 0.845", giving a ratio of 2.367:1----So, the dynamo is turning at 3472 rpm. That is without factoring in any belt slippage. If we allow 5% for belt slippage then the dynamo is turning at 3300 rpm, and that gets pretty darn close to the "best guess" calculation I had made originally, that based on a 28" diameter bicycle tire, with the "rub contact" diameter at 26" , the dynamo with a 1" friction wheel on it would be turning 3000 rpm. when the bicycle was going 10 miles per hour.

Offline Brian Rupnow

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Re: Bicycle Dynamo powered by model I.C. engine
« Reply #32 on: November 30, 2014, 11:47:48 PM »
--Back when I was a kid, a neighbor had a "wind charger" mounted on his garage. As I remember, it had 4 or 6 "blades" made out of old car license plates, and was about 30" overall diameter. The "blades" were attached to a center hub that was mounted on a car generator, and he must have had a voltage regulator wired into it somewhere. He used it to keep a spare battery charged up. That would have been in the 1950's. Then in the 1960's when they ran the hydro line into Kaminiskeg Lake near Barrys Bay I was in high school in Bancroft. I got a part time job with Ernie Byers, a local electrician, wiring and doing some plumbing in cottages in on the Lake. One place sticks in my mind, because it had a fast flowing stream coming down the hill from the northwest side, right beside his cottage. He must have been a pretty resourceful guy, because he had a Pelton wheel in the stream, hooked up to a car alternator and had the whole cottage wired for 12 volt electric lights. One of the funny/crazy memories I have from that time---Ernie had a little wee car, I think it was a Mini Cooper or an Austin Mini. We went to the hardware store in Bancroft and picked up six 10 foot lengths of 1/2" copper pipe to take up to Kaminiskeg. He didn't have any roof racks, so he had me roll down the passenger window and stick my arm out the window and hang onto the pipes. They didn't weigh very much, and he taped the ends together so they wouldn't all come apart while we were driving. About half way up to the lake, we ran into an absolutely ferocious thunder and lightning storm. i was scared right to death that I was going to become a human lightning rod, hanging onto all that copper pipe, but Ernie said "Don't worry Brian, we are up on 4 rubber tires, the lightning won't bother us!!!" I don't know if he was right or not, but I didn't get struck by lightning. I was awful damn glad to get to the end of that trip, anyways.

Online Roger B

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Re: Bicycle Dynamo powered by model I.C. engine
« Reply #33 on: December 01, 2014, 07:23:23 AM »
Very nicely done  :praise2:  :praise2: and some more useful information and numbers to store for future use  :ThumbsUp:  :ThumbsUp:
Best regards

Roger

Offline Ian S C

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Re: Bicycle Dynamo powered by model I.C. engine
« Reply #34 on: December 01, 2014, 12:11:45 PM »
You might be better using a small DC motor for a generator, I use the ones in old HP ink jet printers(as I upgrade my computer, the old printer becomes obsolete), the motors rang from about 1 1/2" to 2" long, and 1" to 1 1/2" diameter, 12volt, and not very high revs, and they give quite good power at lower revs.
                                                          Ian S C

Offline Bruno Mueller

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Re: Bicycle Dynamo powered by model I.C. engine
« Reply #35 on: March 26, 2023, 12:44:33 PM »
The above contributions
are already almost 10 years old.
Nevertheless, I would like to show you my version of a dynamo made from bicycle parts.
I have disassembled the inner workings of such a dynamo. I knocked the existing axle out of the permanent magnet and glued in a new axle with Araldite.
There are two different arrangements of the coil.
In older dynamo models, the coil sits directly around the magnet core. These devices are wider in diameter. In another version, the coil sits behind the magnet core and the pole tongues grip around the magnet core. These dynamos are narrower in diameter, but the overall length is somewhat greater.
I have built and tested both versions.
For clarification, I have also made a dynamo with a transparent polycarbonate body.
Have a look at the different pictures.

In the first and third pictures, the coil sits around the magnetic core. All other dynamos are constructed like the transparent dynamo. The current connections are insulated in the housing.

« Last Edit: March 26, 2023, 12:54:50 PM by Bruno Mueller »
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