Monday, July 22, 2013

1953 GH6 Dynohub Rebuild

The last post covered rebuilding the rear hub from the 1953 Raleigh Sports.  This post will look at the front hub for this bike a Sturmey Archer Dynohub model GH6 (Generator  Hub 6 volts).  It has a date stamp of 9 53 (Sep. 1953).



This bike originally had two lights mounted, one for the Dynohub, the other was connected to a tire driven bottle generator.  The wires to the Dynohub were not connected  so I assumed the Dynohub may not be working.



I mounted the rim in the truing stand, connected a multimeter to the Dynohub terminals and gave the rim a spin.  Amazingly; after 60 years, and sitting unprotected in the weather the Dyno still produced a current.







Knowing the  hub still has some life, I was ready to start disassembly.  I removed the hub from the rim and gave it an initial cleaning and degreasing.


Note the lack of a Spacing Cup (HSD 301) on the left side against the Dyno.  Instead, two thick washers were being used.  I'm assuming it did not come from the factory this way?

The internals of the Dynohub are not that different than a normal front hub with the exception of the Armature and Magnet, basically just cones, races, and bearings.




The Dyno is on the right.  The black center portion is the Armature which is stationary, the outer ring is the Magnet which revolves around the Armature producing current.  

An important word of caution, never separate the Armature and Magnet.  Separation even for a fraction of a second will cause loss of magnetism.

This bike appears to have seen many miles, the rear AW hub cones/races were very worn, these are equally bad.  The bike did have an old District of Columbia bike registration sticker, that plus the additional lights, and all of the reflective tape suggests a well used DC commuter bike.







Finding replacement parts in the USA for a Dynohub is much more difficult then obtaining parts for a AW rear hub.  The bearing races are part of the hub shell and cannot be replaced without replacing the entire shell.  The cones are also hard to find, unless you can cannibalized another Dynohub.  The caged ball bearings and dust caps are interchangeable with those of the AW rear hub.

The cones on the left are from the 1953 hub, the cones on the right are from a 1947 hub and will be used as replacements.


As noted before, this hub appears to be missing the Spacing Cup (HSD 301), these are also difficult to find.  I was able to make an replacement on the lathe from aluminum, hopefully it will work OK.  I think the only purpose of the Spacing Cup is to fix the terminal plate in place, preventing it from rotating with the wheel, and set the "over-the-locknut-distance (O.L.D.) to fit within the front dropouts.

This picture show the original two spacers used in lieu of a Spacing Cup on this hub in the background. The Spacing Cup on the left is from the Dynohub used on the 1949 Comrade, the one on the right is what I made on the lathe to replace the two washers in the background.
 


Original configuration with two washers


This is with homemade Spacing Cup

This is the hub rebuilt with replacement parts, new grease, and shell buffed.  I'm measuring the "over-the-locknut-distance" (O.L.D.) to make any final adjustments with spacers, washers, etc.  The front fork dropout spacing on Raleigh Sports is approximately 90 mm, so the O.L.D. should be equivalent.


 Please share your thoughts and experiences.

6 comments:

  1. Hi 73emgee

    Found your blog via the Toggle Chain Tour Forum. Like what you have done with the GH6 Dyno-hub. Can I ask what methods you used to get the chrome looking so good - I have recently re-built a 1949 Dyno-3 Hub and just need to buff up the shell.

    Thanks in advance
    Jimmy

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  2. I use a 2 step process, the first removes surface rust and light scratching. for the step 1, I use a 8" cotton Spiral Sewn wheel mounted on a bench-top grinder, and Tripoli buffing compound. Step 2 is final polishing, 6" Loose Muslin wheel with Red Rouge compound. I got the products from Grizzly.com. Sturmey-Archer seems to have used quality plating, I'm always amazed that it can still look good after 60-70 years.

    Did your 1949 Dynohub have a Spacing Cup?

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  3. The 49 Dynohub does have a spacer but it different to what is used on the GH6, it is cross shaped to allow you to adjust the cone. If you want a parts list/assembly drawing for a 49 Dynohub, send me a private message at the toggle chain tour forum (I use the same name) and i'll be glad to send it on to you.

    Thanks for the tip on the chrome cleaning. I do use drill mounted buffers and have had good success with stainless steel wheel rims. I will have to look at the red compounds, I have just purchased a chrome cleaning kit which uses a white compound (http://www.shesto.co.uk/p1092/Policraft-Chrome-&-Plated-Material-Polishing-Kit/product_info.html) - I am in England by the way.

    Thanks again

    Jimmy

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  4. Hello,

    one of the two wiring bolts on my '52 GH6 has broken off. I have disassembled the hub but did not know how to take off the face plate through which the bolts protrude. I'd appreciate your help

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    Replies
    1. Hi,

      I've never removed the magnet from the shell (not recommended), not sure how the face place is attached to the shell. Sorry.

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  5. Hello Robert, I'm in the process of re-building one of these hubs too. The one I have does not even have a spacing cup. Without it, the axel spins freely and does not engage the armature/magnet assembly. Is the friction/pressure of the spacing cup against the armature/magnet assembly the only thing that connects these and drives the electric current?

    Also, I'm happy to use a couple washers, but do you ever fabricate a part like the spacing cup for sale? I have no access or skills on a metal lathe...

    Thanks-
    charles

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