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DD Ignition for Twins
Posted: Fri Jun 18, 2021 8:00 am
by daxman
HI DD
I spotted an old thread about using and aftermarket Fiat 500 ignition by DD. Looks cool. One question though.. Are those backplates you have home made? look prety precise to me. I reckon I could knock something up stitch drilling and filing but could it be made from acrylic?
Re: DD Ignition for Twins
Posted: Fri Jun 18, 2021 8:36 am
by daxman
PS any idea why the Newtronic systems need another black box? Some kind of boost amplifier or more than that (e.g. advance retard provision)
Re: DD Ignition for Twins
Posted: Fri Jun 18, 2021 11:01 am
by jabcb
Newtronic uses optical pickups. All the switching logic is in that black box. Timing is fixed — same as with the original points.
Re: DD Ignition for Twins
Posted: Sun Jun 20, 2021 3:49 am
by daxman
Ah right, thanks. In that case the magnetic systems seem a lot simpler.
Re: DD Ignition for Twins
Posted: Sun Jun 20, 2021 5:22 am
by jabcb
The dwell angle for the original points is around 180 degrees. The points are closed for about 1/2 of a crank rotation.
The Netronics optical pickup can easily be designed to get about the same dwell. See:
Per their documentation, the Accent ignition is also designed to get an appropriate dwell angle.
Some of the magnetic systems provide much higher dwell angles. The coil is charged for more degrees of rotation, which is great for a good spark but taxes the battery+alternator more.
The twins have a barely adequate alternator & tiny battery. So some of those magnetic systems may overtax the battery+alternator.
Re: DD Ignition for Twins
Posted: Wed Jun 30, 2021 5:42 am
by dollydog
hi dax, sorry i missed this post somehow. my mate round the corner made half a dozen backplates for me from some solid round brass bar. drilled them, did the slots, then pared them off. i suppose you could use acrylic, but it would have to be fairly thick, due to the 2 tiny holes - m2.5 - that hold the pickup on have to be threaded. probably a lot easier to machine brass, as acrylic has a tendency to crack when you file it, unless you're VERY careful. i'm sure i sent you the dimensions for the backplate a couple of years ago. have a look through your old pm's. if it isn't there, give me a shout and i'll measure one up for you
cheers, dd.
Re: DD Ignition for Twins
Posted: Wed Jun 30, 2021 7:19 am
by daxman
dollydog wrote: ↑Wed Jun 30, 2021 5:42 am
hi dax, sorry i missed this post somehow. my mate round the corner made half a dozen backplates for me from some solid round brass bar. drilled them, did the slots, then pared them off. i suppose you could use acrylic, but it would have to be fairly thick, due to the 2 tiny holes - m2.5 - that hold the pickup on have to be threaded. probably a lot easier to machine brass, as acrylic has a tendency to crack when you file it, unless you're VERY careful. i'm sure i sent you the dimensions for the backplate a couple of years ago. have a look through your old pm's. if it isn't there, give me a shout and i'll measure one up for you
cheers, dd.
Hi DD
The dims are in the original post/thread I pinched the photo from, so no problem.
