Author Topic: No spark  (Read 2363 times)

Offline Triton Thrasher

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Re: No spark
« Reply #30 on: 19.04. 2015 17:56 »
If the auto advance has moved on the shaft, the tapered faces may be a bit chewed up.  The pinion should stick readily to the shaft, when you press it on with your fingers.

I've had success grinding them in together with fine valve grinding paste.

I can't see what's up with the bent thing.  It looks like you may have bent the moving point plate, by forcing it to move, with a screwdriver, when one of the two screws was not loose enough. Straighten it. 

It's common to have to bend it so the points meet squarely.


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Re: No spark
« Reply #31 on: 19.04. 2015 18:13 »
Lucas called the later steel backplate assembly "low inertia". Low cost more like. Don't know about the inertia either, as the force required to open the steel ones can be considerable even if the weight of the rotating mass is less than the earlier type. The advantage is they work for anti-clock and clockwise mags by fitting the moving point one way round or t'other - provided the fixed contact point is on the correct side. Original ones, some of, had a fixed point on BOTH sides of the butterfly, but most sets are anti-clockwise rotation only, with just a rivet (one of the bits that broke on Wilko's) where there could be a second contact for a clockwise mag like on a Vincent, Douglas, loads of cars etc. And that's a fiddly mod too - swapping a rivet for a decent tungsten point in a very confined space. Been there, done that and didn't like.

The worst of the later sets, in my view, is that the opening point is low tension 'live'. So if the spring blade, or the 6BA screw that retains it, kisses the camring on the way round, bye-bye sparks. The brass sets were arranged the other way, so there couldn't be a low tension short circuit (for that reason at any rate).

If the adjustable plate is bent, it might be because the insulator - a small figure of eight-like bit of nylon, usually white-ish, wasn't seated properly. Easy enough to get askew, what with the little register sleeves that go up and down and around. When the plate was tightened up by the two screws, being so flimsy, it could have buckled. It should straighten out with a bit of force.

You'll really curse, Marqs, when you take off the moving point and the spring washer that holds the plot together busts one of its little tangs  . . . .

It would be really GOOD if new cb backplates were available. TT refers to the loose pivot syndrome - which happens to brass sets too and is never good. But there are only e-bay solutions it appears, and who knows what you'll get from there. Last year, I started making a few new backplates for my own purposes, but (like for ATD parts, see other posts) it's a labour of love . . .  and is more complicated than it looks when it comes to broaching keyways and so on. The dimensions are mission-critical for the maintenance of correct internal timing on any mag, and the pain of getting it wrong after spending ages on the tools is hard to describe but I know it well  . . . What we need is a small production turning operation - or better still a small foundry operation with accompanying finishing skills - to get into production with new units of a quality comparable to the brass type. They are a hell of a time-consuming thing to make as a one-off on a lathe and milling machine, although it can be done and I proudly possess one or two (which actually work fine).
 
It's the old thing: - who is willing to pay what it costs to make these things in pitifully small quantities? For 'cooking' everyday bikes like mine, not me, and I doubt if most classic owners would either. It requires scale Scale SCALE, which we just don't have as far as I can see, or folk like Wassell would have got there it already.

Cheers, Bill
Bill

Offline Butch (cb)

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Re: No spark
« Reply #32 on: 20.04. 2015 17:20 »
Or a cheap manually skilled resource pool?
Warning - observations made by this member have a 93% unreliability rating.

Of Bikes; various, including ...
'58 Iron Head Flash Bitza


Offline Marqs1979

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Re: No spark
« Reply #33 on: 20.04. 2015 17:46 »
http://forumbilder.se/EB1F1/20150420-183628.jpg

I have access to this machine, and believe me without much difficulty can manufacture copies of the brass plates. The only thing I do not know how I'm going to do is the wedge that prevents the plate from rotating in the hole ??


Today I grinded with fine valve grinding paste  up the advanceunit to the shaft and now it seems the machine start and go without interruption

Offline Triton Thrasher

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Re: No spark
« Reply #34 on: 20.04. 2015 19:07 »
I suspect the key is formed with something like a crimper, or jodler.

A key could be soldered on too, I guess.

Offline Angus

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Re: No spark
« Reply #35 on: 20.04. 2015 20:33 »
I have no skill or knowledge of fabricating parts but I have been reading about 3d printing and was starting to wondered which parts could be produced using this method. It seams ideal for small runs of specialised parts but not sure of which material would be best and what the wear and stress requirements would be. The process once scanning or obtaining a drawing of the required part appears to be RELATIVELY cheap.
1961 A7 since 1976
1960 A10 Gold Flash Super Profile Bike
1958 Matchless G80 Project
1952 Norton Model 7 Plunger
1950 T100

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Re: No spark
« Reply #36 on: 21.04. 2015 07:56 »
Depends how many you fancy making Marqs, I guess, with that nice bit of kit you show there. (Drool drool.)
One-offs can be done with a bit of time, see pic - the later type being easier to replicate on non-computerised tools etc. Some design mods could be incorporated - screw-in pillars for the pivot being a useful one in my view.
As for the keyway, a little broach will do it as a simple whacking weapon, but a production job would need a careful degree-controlled set up so you could put the key wherever you wanted it for use on different mags - of all makes using ringcams of the same basic dimensions - eg Lucas, Bosch, BTH, some Magn├ęto France, ML etc - for either anti-clockwise or clockwise drive. And as TT says, a blob of solder and a file will do the job to reclaim a damaged one or put something on a blank taper, as long as it's put on in the exact right place to get the optimal internal timing.
The brass type present the additional problem (for a non-professional production environment) of makinjg up the fixed point mounting block, but can also be done if time is no object.
The one here is made in bronze (because I had some the right dia, for no other or good reason) and works fine. The pivot is screw-in and uses a screw to retain the moving point. The worst thing? Making the winged plate for the tail screw for the moving point screw. A dead easy production stamping process, sure, but a pain in the proverbial without.
(The insulator was in fact made on a 3D printer. Not sure what materials can actually be used with them, but plastics won't do it for the main parts angus. However, if it's true that someone made a pistol capable of firing using one  . . . anything's possible!!)
Cheers, Bill
Bill