Points housing

mdt-son

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Hi all,

Some time ago I purchased a contact breaker housing which features a needle roller bearing and a plain bush bearing. I believe the p/n is 033066. It also came with a 10CA points plate which carries no. 47651A and date of mfg. what seems to be 4772 (apparantly made in W47-1972) - stamping is a little garbled thus hard to decipher).

Recently I discovered that Andover Norton sells spare parts for the points housing. However, the version they support is a later points housing featuring two needle roller bearings. I guess that's p/n 034049, although listed as having a bearing and a bush - which is probably wrong. The other day I read a story of Mike Patrick (development tester and Californian desert racer) in which a story is told of staff of ZDS Motors forcing NV-Matchless to fit double needle bearings in the points housing. The later points housing supported by Andover Norton indicates the story may be true. If so, that is a fascinating detail in the P11 development saga. The second needle roller bearing carries p/n 034052 and there is also a rubber seal, p/n 034053 which is missing in the earalier version (033066). All these numbers (034049, 034052 & 034053 and a new drive shaft 034051) belong together, indicating a circular development effort.

Back to mechanics. I wonder if a conversion of my points housing to the later type is possible? Mine came without a drive shaft and conversion to the later type would simplify completion. I suppose the later type is a better design as well. What OD and counterbore depth for the inner bearing and seal is required?

The populated 6CA points plate for P11A and Ranger models is listed as Lucas 54419097. The populated 4CA points plate for the P11 model - listed as p/n 033045 - carries Lucas p/n 425379.

Lucas 47651A is actually a 10CA unit used by the british m/c industry 1973--78. Thus, the stamping 4772 is correct. 10CA and 6CA appear to be interchangeable. They are very similar, the 10CA has a better guide design for moving the points plate though. The 6CA relied on a raised guide in the base plate while 10CA features pins in slots.

Contact sets for 4CA carry Lucas p/n 54415823; for 6CA Lucas p/n 54419827, and for 10CA Lucas p/n 60600271 (one off in each case). Contact set 60600271 was used on all Commando models after 1971.

The later c/b housing, cover, shaft, AAU and contact breaker plate (6CA) lacking condensers on the plate is listed as p/n 034086. I guess it was listed as a retrofit for P11 models.

Incidentally, I found for the first time a Commando part number used for the P11A and P11A Ranger models! It's the condenser pack 060573 which AMC fitted between the coils. This prompted relocation of the ignition key lock - a welcome change it seems.
The P11A Ranger probably had a few other Commando parts, such as the silver painted barrel. Unfortunately this is not covered in the latest parts book.

-Knut
 
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Good work Knut. I have seen both types and when I get back from the INOA rally I'll see what I have on hand.
 
Back to mechanics. I wonder if a conversion of my points housing to the later type is possible? Mine came without a drive shaft and conversion to the later type would simplify completion. I suppose the later type is a better design as well. What OD and counterbore depth for the inner bearing and seal is required?

I checked my spare points housings, and they are all two needle bearing models. I know I had at least one bush/needle bearing unit, but it must be in a 20M3 Commando or a P11 that is already together. The small needle bearing measures 0.500 ID x 0.700 OD X 0.25 depth. The larger bearing is 0.625 ID x ? OD x .500 depth. I can't get an accurate ID measurement with the caliper I have. The seal is the same as the points seal for a 20M3S Commando so is 0.625 ID x 0.938 OD X 0.187 Depth (thick). If you get the large needle bearing you should be able to measure the OD. It should be a simple job to machine the housing for the bearing and seal.
 
<..> The larger bearing is 0.625 ID x ? OD x .500 depth. I can't get an accurate ID measurement with the caliper I have. The seal is the same as the points seal for a 20M3S Commando so is 0.625 ID x 0.938 OD X 0.187 Depth (thick).

Thank you Ron. The larger needle bearing p/n 034052 is a standard bearing and from photographic analysis I deducted 5/8" x 13/16" x 0.5" (IDxODxW). They are available from many sources, e.g., Koyo J-108. Triumph/BSA used them as layshaft needle bearing on their small unit singles (TR25, B25, B44 etc), p/n 70-8005.
As the needle bearing and the seal have different ODs, a stepped counterbore with additional depth is required. A fairly simple milling job, but I need to get this right in the first run.
I will inquire with AN as to proposed depths and tolerance. Will post a conversion sketch once done.

Thanks,
Knut
 
Since the seal thickness is 0.187" the depth of the counterbore would match that (or perhaps slightly deeper). It would certainly be helpful to have a later unit in hand while milling. I would lend you one of mine, but the shipping costs from the US and back would be expensive.
 
Ron,

that's a very generous offer but prohibitive in terms of shipping costs. I will inquire with AN and/or try to obtain a later version.

Thanks,
Knut
 
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