G80s '54 - dynamo chain/ primary chain clearances

Information relating to the Matchless G80 or AJS Model 18 500cc Heavyweight.
Member
Posts: 125
Joined: Sun Apr 30, 2017 9:42 pm
Location: ARGYLL UK

Re: G80s '54 - dynamo chain/ primary chain clearances

Postby Stephen G80 » Sun Sep 03, 2017 11:55 am

Thanks Triumph -Legend - that spacer is in place ie part 010629.

Member
Posts: 1562
Joined: Wed Oct 12, 2005 9:45 pm
Location: N YORKS UK

Re: G80s '54 - dynamo chain/ primary chain clearances

Postby 56G80S » Sun Sep 03, 2017 1:10 pm

That nut should be done up as tight as you can get it and make sure you have the proper dished retaining cap not the rubbish pressed steel one that was about many years ago - a Club one will be fine (000831 ENG.SHOCK ABSORBER CAP) The nut will tighten up the cap hard against the crank axle and with the correct square section spring there is no chance of overdoing this as the amount of pre tension on the spring is set by the amount of "dish" in the cap. If underdone it will either chatter and fail or the nut could unwind. I know from experience (back in the 1970's) all four forms of failure in this area - broken spring, failed cap (split or chattered to bits) and undone nut.

Johnny B

Member
Posts: 125
Joined: Sun Apr 30, 2017 9:42 pm
Location: ARGYLL UK

Re: G80s '54 - dynamo chain/ primary chain clearances

Postby Stephen G80 » Sun Sep 03, 2017 1:36 pm

thanks Johnny.

Member
Posts: 125
Joined: Sun Apr 30, 2017 9:42 pm
Location: ARGYLL UK

Re: G80s '54 - dynamo chain/ primary chain clearances

Postby Stephen G80 » Sun Sep 03, 2017 3:40 pm

Update:

As I was replacing the primary sprocket from 21 to 22 tooth, I just went and measured the distance between the old chains on the old sprocket and it is 3mmplus between the end of the rivets between the two chains - so seeing as things will have been designed for the chains to run true off the sprockets it figures they should have 3mm plus at cross over - so I am pretty confident its all spot on now. Thanks for all the advise folks. :beer:

Member
User avatar
Posts: 54
Joined: Tue Nov 29, 2005 8:51 pm
Location: Herts UK

Re: G80s '54 - dynamo chain/ primary chain clearances

Postby Group Leader » Sun Sep 03, 2017 6:52 pm

After I'd re-conditioned my dynamo recently I was faced with position of the dynamo / chain clearance issue.

To my way of thinking there are 2 critical factors for the dynamo chain:

1) The two sprockets must lie on the same plane (that is they must both point in the same direction and they must be aligned)
2) The tension must be correct and definitely not too slack to prevent chain whip (is that the right word?) i.e. lateral movement particularly with worn chains

I'd seen the method of sprocket aligninment by calculation using various measurements to conveinent reference points but to me it seems to be a method that all too easily can introduce errors due to the possible accumulation of the inevitable measurement errors. As the fundamental point is to ensure that the sprockets are in line I found that the easiest way to achive this for me (having previously confirmed that the two sprockets had identical thickness) was to clamp a straight edge to the face of one sprocket (the driving one seemed like the best idea) and then to position the dynamo so that there was the smallest, parallel gap (literally a "fag paper") between the straight edge and the driven dynamo sprocket. The alignment of the two must then be correct.

I described this approach more fully here http://www.jampot.com/forum/viewtopic.php?f=12&t=21316&p=180066&hilit=E3N#p180066. It worked for me but I too was still concerned by the relatively small clearance between the two chains hence the importance of point 2 above.

I hope that is useful.

Alan
Last edited by Group Leader on Mon Sep 04, 2017 2:44 pm, edited 1 time in total.
1953 AJS 16MS and a 1/3 scale Sopwith Triplane but that's another story ..... :lol:

Member
Posts: 239
Joined: Thu Mar 31, 2005 12:00 am
Location: BERKS UK

Re: G80s '54 - dynamo chain/ primary chain clearances

Postby Andy51 » Sun Sep 03, 2017 7:27 pm

Stephen, this reply may be too late, but alas I cannot post a link. Stuff that has appeared in the Jampot does not get added to the Tech Articles list on the website - I don't know why. If you PM me I can send the article direct. Andy

Member
Posts: 125
Joined: Sun Apr 30, 2017 9:42 pm
Location: ARGYLL UK

Re: G80s '54 - dynamo chain/ primary chain clearances

Postby Stephen G80 » Sun Sep 03, 2017 8:47 pm

Hi Alan - that interesting approach re the straight edge, I suppose by using the measurement of the space between the two chains on the sprocket (3mmplus) and ensuring the same clearance at the cross over point, and doing so with correctly tensioned chains I was in effect using the primary drive chain as my straight edge - so we used the same principle but different tools.

Hi Andy - thanks for offer of PMing me the article -see PM.

Previous

Return to G80 / Model 18

Who is online

Users browsing this forum: No registered users and 4 guests