Rivet Counters Club

1. Like most manufacturers Ariel changed the design of parts from time to time for either technical or aesthetic reasons. Usually the new part was given a new number, even if the two parts were interchangeable or one superseded or replaced the earlier part, so that everyone involved could be sure that they were talking about the same part. Sometimes the part was changed but the number was not and rivet counters love spotting these undocumented changes.The steering damper knob is one such item that exists in no fewer than four variants between 1938 and 1958 but all use the same number. The original one, 4901-38 is made of a black plastic with ribbing around the outside and small writing around the circumference of the top that reads “ARIEL Selly Oak Birmingham“. It is prevented from rattling by a small spring inserted into the threaded hole on top of the damper rod and the lower edge is flat where it sits on the top yoke. In 1946 telescopic forks were introduced and the anti rattle spring was changed for one of a much larger diameter that fitted into a groove in the base of the damper knob; the external appearance did not change. We call this one 4901-46 (see what we did there!)In 1951 the design of the top was altered so that there was a ridge around the edge and a logo with “ARIEL” written in it was positioned in the centre. We call this one 4901-51. (I think there might be a pattern forming here)The rarest, and one that every self respecting collector of Ariel damper knobs should have, is the one made sometime after 1951 for girder fork models that has the later design of top but with the earlier flat base. We call this one 4901-? (We had to fall flat somewhere)

   Currently only the 4901-51 type is available but it works with all fork types with either anti-rattle spring.

   Now we would love to see you pictures of the changes of the knobs so send them in and we can attach them to this Rivet Counters article.

2. BSA A50 and A65 inner timing covers and their differences (at last, I hear you cry, a BSA piece). This is very interesting if you happen to have a large collection of them and are puzzling over which one is which, as he was. He has listed all of the differences, year of use and the all important part numbers. Would you believe that there are 9 timing cases for 11 years.BSA A50 and A65 inner timing covers and their differences. Apologies for the size of the table.
   

   		Supersede	Casting number	Dipstick	Tacho drive	2nd dowel	idler bush changed from flanged to plain	clutch mechanism + 6 outer screws	7 outer cover screws	Defining feature
   1962	68-212									No tacho+no dip see 68-529, difference unknown
   1963	68-212									No tacho+no dip see 68-529, difference unknown
   1964	68-529	68-534								No tacho+no dip see 68-212, difference unknown
   	68-534				y					Tacho+no dip see 68-774, difference unknown
   1965	68-534				y					Tacho+no dip see 68-774, difference unknown
   1966	68-774		68-775/68-869		y					Tacho+no dip see 68-534, difference unknown
   1967	68-868		68-775/68-869	y	y					Dipstick+.6″ CB/idler bush no 2nd dowel
   1968	68-868B		68-775/68-869	y	y	y				Dipstick+.6″ CB/idler bush+2nd dowel
   1969	70-9482	68-868	70-9480	y	y	y	y			CB/idler bush .9 long, late .6 but 3 outer case screws
   1970	71-1118			y	y	y	y	y		1 anchor peg but without 7th outer case screw
   1971	71-2277			y	y	y	y		y	Extra outer case screw hole between g/c & k/s
   1972	71-2277			y	y	y	y		y	Extra outer case screw hole between g/c & k/s

3. There are 5 con rods for the D1, D3, D5 and D7 listed, 3 different small end bushes, (2 bushes & 1 bearing) however there is only 1 part number for the assembly. This being 90-497. For this article I will be focusing on the small end bushes, because they make my brain hurt less. These vary in sizes with 90-130 (9/16 x 7/16(D1 & D3), 90-1385 (21/32 x 9/16(D5 & D7(1959-62))) and 90-1458 (bearing 3/4 x 9/16(D7 1962-65)). Now why BSA decided to do this I am afraid to say I have no idea. I can only suspect it is due to lack of anything more important to do. Where as in the last years of this setup they introduced a needle roller bearing with a different OD they failed to introduce a new part number for the con-rod. So now you have the facts about sizes of small end eye, you can properly identify the year of your rod. Oh, by the way, Draganfly have made new part numbers (yes it does happen) 90-497AF, 90-497BF, 90-497CF. See what we did there. Now the next installment of the RCC is “Why are Draganfly exchange items listed with an F and not an E” get your thoughts in now and see if you win a prize.
4. A common subject for discussion amongst Arielists is “where does the chamfer on the girder top link go?” The top link is basically a square bar with a hole at each end that attaches the fork blade to the top yoke and has a chamfer along one edge. A common misconception is that it should face upwards on the inside edge to prevent the control cables from chafing on the sharp corner. However when the bike hits a large bump and the forks move to their fullest extent it will be found that the lower inside corner will hit the lug at the top of the fork blade. I think that someone at the factory discovered this mistake and rather than modify the fork casting they decided to put a chamfer on the link to prevent it hitting the fork. So the chamfer should be on the lower inside edge.