Author Topic: lucas mystery to me (points)  (Read 304 times)

Online berger

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lucas mystery to me (points)
« on: 11.03. 2021 12:48 »
the two sets of points on the left have come off magnetos I have used on the bsa over the years. I have just found a set in a box that are  opposite in respect to the arm position . what are these for? excuse the old phone picture again but I have a plan. I am going to ask my youngish neighbour to show me how to operate the other phone  *help*

Offline Topdad

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Re: lucas mystery to me (points)
« Reply #1 on: 11.03. 2021 14:05 »
Could it be a reversed rotation  set ?
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Online bsa-bill

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Re: lucas mystery to me (points)
« Reply #2 on: 11.03. 2021 17:09 »
I think there are anti clockwise sets for different bikes and also do I recall sets that did both ?
All the best - Bill
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Online groily

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Re: lucas mystery to me (points)
« Reply #3 on: 11.03. 2021 18:01 »
First 2 sets are for anti-clock drive mags.
3rd set is for a clockwise drive one - so is good for Vincents (singles or twins), some early Oilfield twins, some other rarer older machines - and any number of 4 cyl mags for cars.
Of course, ones for 'Vincents' are worth more as a matter of principle - and in fact they may actually be, if they have platinum points, which are worth a few £$€.

Brass backplates are all handed according to rotation, and so are BTH and Bosch and most others - but the later steel backplate Lucas type can go either way if there is a contact on the second 'wing' of the fixed point carrier. Most replica sets don't have 2, all Lucas originals did. But the opening point can be fitted either way up / round. A drawback with the later type is that they can't take an auxiliary earth brush - and for older Lucas mags with no earth bar a brush on the back of the cb unit, 'tis a problem.

At the moment, new parts are getting harder and harder and we should all - I mean this seriously - hang on to any contact breaker parts, even well-knackered ones. It's always possible to graft new tungsten tits on, and worn pivot posts and oval holes in the spring point can be sorted if they really have to be.
The supply of replica steel ones has dried up - although the rights and the tooling are now in the hands of Grove Classics apparently. Nothing has been forthcoming for several months afaik.

It is worth bearing in mind, though, that most cb backplates have standard dimensions. Which means that in cases of despair, a BTH or Bosch unit (or various others come to that) can serve. It may - probably will - mean having to 'adjust' the position of the integral keyway on the male taper to get the points to open at the correct time relative to the armature/magnet position, but there are some advantages to the design of, particularly, BTH parts compared to Lucas.

Adventurous folk may want to have a crack at making their own backplates  . . . all I can say, having made a few (and not very satisfactorily), is I found it darn hard and not a good use of time. However, people with better skills and tooling more suited to repetition work than mine could actually make a useful contribution to their beer funds I reckon, looking at what tired units sell for on e-bay.  New proper quality cb units complete, for face cam mags like N1 and magdynos, go for around £75 - no reason why 'ours' aren't worth similar, if there's quality  . . .

Bill

Online berger

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Re: lucas mystery to me (points)
« Reply #4 on: 11.03. 2021 18:29 »
thanks groily I stumbled upon a set of platinum tipped ones about 12 years ago which are now in my maggy on the bike. the brass backed ones are the ones I have had for many years it was just that I found the steel ones today and now remember a mate gave them to me years ago.  I was a bit confused because I now remember he said they would do for my maggy. so I know what i'm looking at now and will have to investigate the tips on them, cheers

Offline Swarfcut

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Re: lucas mystery to me (points)
« Reply #5 on: 13.03. 2021 09:27 »
   Steel backed points carrier uses a different length retaining bolt to the brass type, which also has a taper under the bolt head. Using the wrong bolt risks theoretical damage to the armature windings....

 Swarfy.

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Re: lucas mystery to me (points)
« Reply #6 on: 13.03. 2021 12:35 »
yes swarfy I have the bits for both cheers