Not exotic, just cheaper for Lucas to produce, it's what almost all post mid 30ish single Magdynos have.
Misc: Ignition Lucas KVF Rebuild - UK Recommendations?
I had a look at the wrecked Lucas cam ring, does not seem to be a complicated job. They did not have CNC at that time and I say you don´t need today, just a mill with DRO for easier life - plus a dividing head certainly for milling the larger inner diameter. This is 42 mm on my part, the smaller diameter is 40 mm when the breaker heel slips over it in open position. The 42 mm i.d. does not matter at all as it never gets contact with the breaker heel. My idea would be to have the cam ring clamped in the dividing head in a ring for milling the 42mm circumference, the 40mm diameter was turned before already. So then the end mill will do the 42mm face and by leaving the circumference down from top end mill position, the black circle left top in my photo, and reaching same 42mm diameter at the bottom position, the other black circle. That way you will mill a bit of a flat face opening ramp down from top position and same at bottom position forming the closing ramp too. After this do a bit of handle swirling for more of the 42mm diameter then position the dividing head for the second angular position required for the 50 deg v-twin.
For fabricating new cam rings I´d have some through hardening tool steel , not a lot of distortion to be expected then and not a real effect on timing form this even with a bit of distortion.
I cannot tell how they positioned the cam ring in the mag end cap for correct internal timing. It is glued in in the old part I got. There is a milled gap down below but no indication how this engages anywhere.
Anyway, I believe old and worn cam rings could be reconditioned by having a special carbide end mill suitable for hardened steel and lick up the worn opening ramps for exact timing, no need for milling the rest of faces. Then a jig might be useful for pressing in the cam ring at the wanted position - or maybe glue that, cannot tell what was original.
But really I do not want to start a business at 70 plus of age, just saying . . . .
Vic
P.S. never seen face cam types, would think to be awkward to machine ??
For fabricating new cam rings I´d have some through hardening tool steel , not a lot of distortion to be expected then and not a real effect on timing form this even with a bit of distortion.
I cannot tell how they positioned the cam ring in the mag end cap for correct internal timing. It is glued in in the old part I got. There is a milled gap down below but no indication how this engages anywhere.
Anyway, I believe old and worn cam rings could be reconditioned by having a special carbide end mill suitable for hardened steel and lick up the worn opening ramps for exact timing, no need for milling the rest of faces. Then a jig might be useful for pressing in the cam ring at the wanted position - or maybe glue that, cannot tell what was original.
But really I do not want to start a business at 70 plus of age, just saying . . . .
Vic
P.S. never seen face cam types, would think to be awkward to machine ??
Vic, you have the same ideas about how to make one, but I too, at 76, can't raise my skills enough to do it !. The big issue to me is the ramps up and ramps down. I tried to make one (as an experiment ) out of Delrin, but could'nt master the ramps.
I'll just hope that a specialist engineer eventually creates some. In the meantime, Boyer provides the sparks. If only I could get the Lucas Rita stuff that was on my first twin.
Regards all,, Terry.
I'll just hope that a specialist engineer eventually creates some. In the meantime, Boyer provides the sparks. If only I could get the Lucas Rita stuff that was on my first twin.
Regards all,, Terry.
Both ramps (up/down) have a radius of .630” +/- .0005” I think an off the shelf end mill with a diameter of 1.250” would get you close and then you could finish it with a stone dressed to a diameter of 1.260” I explored the idea of making one, but it made my head hurt. It would be nice to be able to tell myself I made one, but the time required (at least in my shop) means that I’m way better off to find a new one if needed.
In the later edition of that cam housing, instead of those 2 screws, there was a single eccentric grub screw that could be used to fine tune the internal timing. It’s still a bit of a mystery to me why they went that route. It might have some value on a V twin mag so you could get #1 as close to the flip point as possible which in turn would get #2 closer and provide it (#2) with a fatter spark. But… why would they use the eccentric grub screw on a parallel twin mag. It’s a fine adjustment and I don’t think a parallel twin or single mag is really that fussy about where the points open in relation to the flip point (flux reversal). as long as the points open shortly afterwards, all is good.
Last night I had another look into my modded Vertex mags, seems I tried a few positions of pole flip points for having nearly same strength sparks at both wires. So one point is a bit early and the other quite late for optimum power but it is quite allright for me like it is.
As to these radii on the Lucas mag cam rings I do not think they matter much: As you can see in my photo above the two diameters are 40 and 42 mm , so only 1 mm step. There cannot remain much of radius there and remember you set the breaker gap at around 0.4mm so the breaker heel will be 0.6mm above the 42mm face and will hit that radius quite high up and never touch the radius at its lower section. So my idea , get an end mill with 8 or 10 mm , and see what that does for a bit of a flat remaining instead of a certain radius. You get better accuracy with a bit of flat milled than forcing an end mill into a corner position. So you would have the end mill at first position at the black circle top left in my photo for milling the 42mm diameter and stop at that leftmost position. Then feed straight down in line away from upper radius towards the bottom position of lower black circle and do a length of 42mm diameter in the bottom part of cam ring. That would produce the opening and closing ramp with a bit of flat slope I guess.
For the two positions at left side you´d mark the 360 degrees scale on the dividing head with a "zero" arrow with felt pen so for second operation you will use that arrow for rotating the 205 degrees position for the v-twin timing and do same milling like you did at the zero first position. But this is just my idea while sleepless in bed at night, real life at the mill may present some more challenges to think about.
When supply of good cam rings looks poor it might be worthwhile to try reconditioning worn camrings and getting end mills suitable for 60 HRC just for licking up the opening ramp, the rest will do with Dremel polishing a bit. It was amazing to see how the special carbide end mill survived my two welded up ESA cams , 6 cams for 2 bikes, milled in hundreds of little steps. Still that 12 mm end mill shows no wear at all, so this may be worth a try .
I was posting sizes of diameters and breaker gaps and all in metric units, for metric sparks certainly. So for engines requiring imperial sparks you´d have to convert to imperial sizes of course , so on the mill the DRO needs to be put in imperial mode ?? . . . . .
Vic
As to these radii on the Lucas mag cam rings I do not think they matter much: As you can see in my photo above the two diameters are 40 and 42 mm , so only 1 mm step. There cannot remain much of radius there and remember you set the breaker gap at around 0.4mm so the breaker heel will be 0.6mm above the 42mm face and will hit that radius quite high up and never touch the radius at its lower section. So my idea , get an end mill with 8 or 10 mm , and see what that does for a bit of a flat remaining instead of a certain radius. You get better accuracy with a bit of flat milled than forcing an end mill into a corner position. So you would have the end mill at first position at the black circle top left in my photo for milling the 42mm diameter and stop at that leftmost position. Then feed straight down in line away from upper radius towards the bottom position of lower black circle and do a length of 42mm diameter in the bottom part of cam ring. That would produce the opening and closing ramp with a bit of flat slope I guess.
For the two positions at left side you´d mark the 360 degrees scale on the dividing head with a "zero" arrow with felt pen so for second operation you will use that arrow for rotating the 205 degrees position for the v-twin timing and do same milling like you did at the zero first position. But this is just my idea while sleepless in bed at night, real life at the mill may present some more challenges to think about.
When supply of good cam rings looks poor it might be worthwhile to try reconditioning worn camrings and getting end mills suitable for 60 HRC just for licking up the opening ramp, the rest will do with Dremel polishing a bit. It was amazing to see how the special carbide end mill survived my two welded up ESA cams , 6 cams for 2 bikes, milled in hundreds of little steps. Still that 12 mm end mill shows no wear at all, so this may be worth a try .
I was posting sizes of diameters and breaker gaps and all in metric units, for metric sparks certainly. So for engines requiring imperial sparks you´d have to convert to imperial sizes of course , so on the mill the DRO needs to be put in imperial mode ?? . . . . .
Vic
My thoughts were that using a milling cutter would leave an abrupt edge where the cutting stopped. That would surely rip the contact breaker pad away ? To create a smooth transition off and on the 'lift' point would make it difficult to have an exact 'lift' point . It's a very difficult compromise methinks - an interesting challenge for someone , certainly beyond my abilities.
Terry.
Terry.
You mean that transition point of my bit of straight milled face and the i.d. of 40mm ? That point is NOT the ignition point, you set 0.4 mm breaker gap - 15 thou - so the breaker heel will hit that obscure radius at some inclined spot anyway. It never goes down to the base /big i.d. of 42mm as this would be 1mm away and you only got 0.4mm gap. Hope this is some logic to follow ? So then after milling the proposed bit of flat you´d get a rubber polisher for the Dremel and put on a nice top rounding so no sharp edges will stay. Thisis not critical as no timing is made by that rounded edge. And anyway, there will be just some mild variation of curve between that new flat and the 40mm diameter, not harmful to the plastic heel.
Vic
Vic
Thanks Vic, I had not spotted that difference between running clearance and the points gap which makes the trigger point in a different place on the ramp area.
I don't have a Dremel , but clearly this shows the need for one. !
Maybe time to re-assess the 3 cam rings and see if there's enough potential to correct the errors.
I don't have a Dremel , but clearly this shows the need for one. !
Maybe time to re-assess the 3 cam rings and see if there's enough potential to correct the errors.