Full Width Hubs and Sprockets

[RichardL]

Hi guys,

At the recent huge vintage motorcycle swap meet in Davenport, Iowa, I stumbled on a bolt-on 42T sprocket that I thought would work for my '57 A7. I did not have the old sprocket or a photo of it with me at the time. New to the A7, and ignorant of other models with bolt-on sprockets, I snapped up the subject sprocket at a cheap price. Today, I went to see how it would go together with my full-width aluminum hub, I was surprised, and p**sed (at myself, not at the seller), that the bolt circle on the "new" sprocket is smaller than the bolt circle on the hub. I was also surprised when I counted the teeth on the old sprocket to find 41 and not 42. I soon realized that some P.O. had adapted a sprocket ring to the original (I suppose) sprocket disc. That explains the difference in the number of teeth, but not the difference in the bolt circle. Does anyone know what bike the sprocket with the smaller bolt circle would fit on? Except for the bolt circle, the new sprocket fits my hub just fine. If I knew what it came off of I could properly advertise it on eBay or, maybe, buy a hub that works with it, since the hub has its own problems.

Regarding the hub. Some previous owner (probably the same guy) drilled two of the stud threads out for 1/2 bolts. One other hole is completely messed up with something stuck in it (maybe JB Weld). The fourth hole appears to have a good 7/16-14 BSW thread, however, the bolt that was in it seems to be UNC (American) 7/16-14. Because there is a very limited selection of inserts for oversized holes and, also, because the studs that mount  the sprockets are kind'a special, it would be great if I knew I could use 7/16-14 UNC inserts with 7/16-14 BSW studs. Of course, one way to know is to just by the BSW studs and test them in a UNC hole, but I'm impatient for the knowledge. 

Thanks for any help you might have to offer.

Richard L.

Edit: I meant to attach these pictures. Also, allow me to be the first to make a joke about "No Hot Ashes". There, consider it made.

[WozzA]

Richard... these are availiable on you know where & where their from.. 
dont know about quality?   
http://www.ebay.com.au/itm/271983891657?_trksid=p2060353.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT

[RichardL]

Wozza,

Thanks. I have seen a lot of those on you-know-where (the world-wide marketplace who shall not be named?) and I am about certain that is what I need. Though, I would like to know what I've got. Having looked a bit further, it seems my "new" sprocket may be for the cast-iron hub ('58 and later, I think), but I have no way of verifying that, as yet.

Richard L.

[RichardL]

Well, this isn't going anywhere yet. I wonder if anyone has a '58 or later, iron, full-width hub from which they can measure the sprocket bolt circle? Much appreciated, in advance.

Richard L.

[groily]

Dunno about the hub/sprocket thing Richard, but the difference between the BSW and UNC thread is in the thread angle. 55° vs 60° respectively. If an insert could take the strain, a BSW tap run down it when fitted would remove the little bit of extra and probably give you a serviceable result; or, if the bolt is worn it might just screw in anyway. Or, you can get 7/16 x 14 BSW inserts from http://www.tracytools.com/helicoil-thread-repair-kits/bw-thread-repair-kits if they supply the USA. If they don't, happy to get a set for you and pass it on from Yrup.
Cheers, Bill

[beezermacc]

The differences between the Ariel sprocket and the cast iron hub sprocket are....1) the Ariel sprocket has bolt hoes which are less recessed - i.e the bolts travel further in on the iron hub sprocket and 2) the flange which prevents the bearing passing all the way through is much thicker on the Ariel sprocket.

What do you mean by 'bolt circle'?

[muskrat]

Yep the pcd of the holes are different. DAMHIK. Did the same thing back in '91.
Now when the teeth are worn out I turn them off in a lathe and bore out the center of a blank sprocket and weld (4 tacks each side is enough) it on. I use alloy blanks and scotch keys on the cafe.
Cheers

[RichardL]

Groily,

I can get 7/16"-14 BSW helicoils over here, the problem is that the PO didn't bother (pre-internet). Instead, he drilled two of the holes out for 1/2" bolts, so I need oversized inserts, which, as far as I can see, don't come in BSW.

Beezermac,

Bolt circle, in the case of four bolts = center-to-center distance between bolt holes that are 180 degrees apart around the center of a circle. I know you already knew this but figured you should check what I was thinking. (Not a bad idea most of the time.)

Muskrat,

What you described for worn out teeth is basically what the PO did but with a shouldered sprocket and over 20 rivets. To use what I have, I was thinking of just drilling four new holes to the correct bolt circle and filling the unused holes with dummy nuts.  (No reference to Charley McCarthy or Jerry Mahoney intended.)

Richard L.

[muskrat]

You could do that Richard.
In my original alloy hubs the PO drilled out the stud holes and tapped 1/2" BSW. I made stepped studs.
The nuts are different to the BSA full width hub as well.
$185 for a repro from India or $40 for a blank and 30 minutes work. I have short arms and deep pockets.
Cheers

[KiwiGF]

I have an Ariel Hubbed bike and the rear had a couple of messed up sprocket stud holes, I made a stepped stud like Muscrat as a repair for the one stud hole which was only partially stripped, the stud needed to be just a fraction over standard diameter size one end to grip well enough in the hole in the hub, but for a repair to the other stud hole which was stripped much worse I'm embarrassed to say I simply "glued" in a stud in with jb weld.....but it's all held together for quite a while now.

A proper repair I guess would be to fill the stud holes with weld and drill and tap new stud holes.....maybe one day I'll get around to that.

I don't undo the sprocket studs when removing the rear wheel to avoid further damage to the hub, Id rather split the chain and take the wheel out complete.

It does seem the Ariel hubs have a tendency for the stud holes to get wrecked, maybe when the 4 sprocket nuts work loose?

[RichardL]

Well, there is a question of how much effort to put into this hub versus just buying one with smaller issues.

I'm sort'a confident I can deal with the two oversized holes and the third one appears to be in decent shape and original. The tricky one is at the lower right in the second photo. It now looks like the stud broke off while a PO was trying to remove it. He must have then tried to drill it for an extractor or just to see if it would fall out. Might have worked except he drilled off-center. My extractor is just trying to work itself toward the softer aluminum.

I've got some other ideas but my writing them and you guys trying to read them would be more tedious than trying them. I'll let you know what happens.

Richard L.

[bikerbob]

As far as I am aware the swinging  arm models during their production years had 4 different rear sprockets  and they are not interchangeable from 1954/55 part no. 67-6149  1956/7 part no, 42-6069. 1958/59 part no. 42-6333 and 1960 onwards part no. 426331

[chaterlea25]

Hi All,
Richard,
If you can find a better hub then thats the way I would go
If you want to repair your existing hub, where the stud is broken inside the alloy
I would grind away one side of the alloy boss and knock the offending piece out sideways 
If you go about welding up the damaged bosses then welding from the side is a better proposition than trying to fill an existing "hole" with weld
I have been working on a 37 Rudge engine where there was a lot of damaged thread bosses
I have a friend Don Cronin who is quite skilled at alloy welding, and he made a great job of the repairs
His very different Guzzi won the AMD custom bike competition in Germany in 2013
http://www.medaza.com/index.php/recent-projects/rondine
Dons Sculptures are equally impressive
Some images here
https://www.google.ie/search?q=don+cronin+sculptor&biw=1120&bih=820&tbm=isch&tbo=u&source=univ&sa=X&sqi=2&ved=0CD4QsARqFQoTCJHnsMrGpMgCFYcPGgod5LYImg

Ok I know I have gone very OT 

John

[KiwiGF]

I've never tried it but maybe the right carbide tool bit and a Dremel could be used to remove the broken stud? It would take a fair while I suspect though