Dynamo Chain Alignment

[DJinCA]

It's been quite a while since I've posted anything on my project 51-52 A10GF.  Between Covid, my daughter's family moving in with us for 5 months during a house sale/purchase, and such set backs as a bent craink progress has been slow, but I am at it again.  As a reminder, this is a low-budget build up of a rat bike from from a pile of parts.

Among other tasks, I am about to install the dynamo drive.  It looks fairly straight forward and everything fits, but when I look to align the chain run, the dynamo with cork gasket doesn't seal up against the case.  There is a small gap.  I've seen much discussion of aligning the primary chain (admittedly, it carries a much heavier load) but don't seem to find anything about alignment of the dynamo chain.

I realize that it shouldn't leak as badly as if there were oil in there rather than grease, but leaving a gap doesn't seem sound.  Am I missing something?  Is there a generally accepted fix for this?  Should I follow my instinct and pack out the cork with additional gasket material?

Your collective wisdom and assitance is appreciated.

DJinCA

[bsa-bill]

my option - fit a belt-drive, that, however, may not be your choice, so how about think a little more about the idler sprocket than the dynamo, the idler gear is a press fit onto it's shaft and does have some tolerance sideways, you may well get the alignment you need there

[berger]

when I converted to v belt drive the dynamo pully was out of line so I just used more packing to fill the gap you mention

[chaterlea25]

Hi,
Are you saying that when the sprockets are aligned the dynamo is not seated against the engine case?
If so would a thicker cork gasket work?
I just went through several gasket sets but there were no dynamo cork gaskets in them to measure for comparison
Quite often the driving sprockets do not run true which would give you false alignment ??

John

[DJinCA]

Thank you all for your quick responses.  As mentioned, this is a low-budget build, and an effort to just get this bike back on the road.  As such, I discarded the idea of a belt drive for the time being.  This is my first plunger and my first A10.  I have an RGS project that gets most of the money, but not as much time currently (I seem to have more time than money right now) 

Responding in somewhat reverse order:

John, I had only one cork gasket for the dynamo (but three or four different for the breather) and didn't see different thicknesses offered.  I have another on order and will compare when it arrives.  I will double check runout on the sprocket, especially after readind another recent dynamo thread.

Berger, currently no belt drive for me, but I'm inclined to do as you did and pack it out.

Bill, I didn't even think about moving the gear on the other end of the drive sprocket shaft.  My pile of parts had a gear and shaft, as well as a set still pressed together through the inner timing cover.  Taking that apart proved difficult, as the sprocket had spun and welded itself to the taper on the shaft.  It became a somewhat destructive disassembly.   I ended up using the shaft from the other gear, along with the gear from the fully assembled one and purchased another sprocket.  I don't have a press, and had .a local shop remove the shaft from the unused gear and put the other gear on it.  I had him use ~the same dimensions they had been.   Your approach looks like the "right way" to address the problem, but in the absence of a press, I will have to think about it.  If another gasket is thicker and fills the gap, I will take that route for the time being knowing that I may need to pull the timing side apart again in the future.

Again, thanks to all.

DJinCA

[chaterlea25]

Hi DJinCA,
I would just get some cork gasket from a motor factors , its easy to laminate up to the thickness needed

John

[Swarfcut]

 DJ There should be a cork washer fitted under the dynamo drive sprocket, 67 708 "Idler Pinion Oilseal"  This acts a crude oilseal, but more importantly removes float from the idler shaft, and will position the sprocket further outboard and with it the dynamo chain run. This could account for the gap in alignment.

 For a seized or otherwise problem idler pulley, one option is to remove the inner cover complete, and pull the idler gear off the shaft with a standard two or 3 jaw puller. The shaft will then pass through the bush, ready for the sprocket to await any violence you think fit.

 Junkyard build.... yup, that's my kinda bike.

 Swarfy

[DJinCA]

Hello Swarfy,

Good idea, but that seal, 67-0708 tends to compound my problem as it moves the drive sprocket inboard towards the crank and keeping the dynamo aligned opens the gap between the body of the dynamo and the case.  The shaft would need to move outboard in the idler gear to move the taper and mounted sprocket outboard as well and close up the gap.

When I was disassembling, I tried to pull the gear off the shaft and remove the sprocket/shaft assembly from the outside of the inner timing cover, but could not get it to budge with what I thought was a reasonable amount of force.  The sprocket wasn't very pretty, so I went ahead and cut it off.  As it turns out, nothing lost in doing that.

She is a junkyard build.  I stilll need a few things, especially a used set of exhaust head pipes (I have silencers) and will likely place a wanted posting on this board pretty soon.  I can't put shiney new pipes on a bike like this one.  I have asked both the Northern California and Southern California BSA Clubs as well as Britbike.com (thinking that there are more North Americans there than here) for a servicable set, but no hits.  Someone must have a set leftover from a restoration, but I haven't found them yet.  I will try to post a photo when I get a little farther along in all her light rust and dull paint flaking glory.

Thanks,
DJinCA

[Swarfcut]

DJ, Just measured an idler gear chosen at random. From the rear face of the gear central boss to the end of the plain shaft is 21.5mm. Going the other way from front face to top of the thread is 43mm.

   The cork washer fits on the outside of the inner cover, under the dynamo sprocket, and this keeps the idler gear spindle drawn outboard. Can't see how its moving things towards the crank. If the assembly is correct, misalignment would indicate a problem with the dynamo drive sprocket, assuming the dynamo has the right drive sprocket correctly fitted.

 Swarfy.

[DJinCA]

Swarfy,

You are of course quite correct about the cork washer.  While I know better than to speak from memory without confirming, I still fall prey to it.  I went back a looked last night and discovered my error about where it goes.  I came here to post this morning, but was too late.  Humble pie for dessert, thank you.

As both sprockets sit on tapers, assuming that all is straight and true (perhaps a leap) the only places for adjustment seem to be the press fit of the gear on the drive sprocket shaft and movement of the dynamo.  As the adjustment appears to be small and I have no access to a press, I believe that I will look at packing out the ocrk on the dynamo.

Thanks again to all.
DJinCA

[berger]

packing the cork out on the dynamo is what I did because the taper on the new dynamo pully or both  pulley tapers were a bit out