6hp JAP ignition

[TONY REGAN]

First many thanks to all on site who put me right on valve timing the 1909 JAP 6hp V-twin. Now I have a couple of questions about how the contact breakers etc are wired as this is a coil model. I assume this cyclecar might have been 6volt originally,though for practical purposes I think I'll stay with 12volts. One contact per cylinder and there are 2 connections on each outside the breaker unit as in attatched pic and I was intending to use 2 coils and condensors mounted in a box. Anyone any thoughts on this ? Thanks

[cardan]

Hi Tony,
The role of the points is to make and break the current in the primary circuit of the coil.
From your photo, it looks like the blades that bear on the cam (and carry one side of the points) are grounded (by the two screws that screw into the block at the top of the photo). The cam rotates anti-clockwise, so in your photo the points on cylinder No. 1 (rear) are about to close.
Now it gets tricky because you don't yet have the coils. (By the way, I'd use 6V motorcycle coils and battery... but by all means try 12V if you wish.) Old-fashioned coils had four contacts (+/- for the primary and +/- for the secondary/HT), but a modern one might have the - of the HT connected to the can/metal frame of the coil.
One side of the primary windings of the coil is designed to be grounded - maybe labelled "-" and the other goes to the battery "+". Connect the "-" side of the coil to the isolated terminal of the points, and the "+" to the "+" side of the battery. The "-" side of the battery can be connected to the frame/motor of the bike (i.e. ground) through a switch and (if you like) a fuse.
The HT side of the secondary coil goes to the spark plug, and the case/frame of the coil will probably need to be grounded (to the frame/motor), depending on your HT coil.
The condenser goes across the points, which is equivalent to fitting it from the "-" of the primary coil to ground.
Bingo!?
By the way, the spark you want will occur when the blade falls off the trailing edge of the cam: when the current STOPS flowing in the primary. In modern systems, the current in the primary coil has a long time to build up before the circuit is broken as the points open. In this early system the primary current only has a short time to start flowing in the coil (when the points close) before the points open again. If the resistance of the primary side of the coil is too high the current may not build up to a high enough level before the points open, and this would give a feeble spark. I've never compared the resistance of the primary coil in an early (four terminal) coil and a modern coil, but it might be interesting.
Good luck,
Leon
Still interested in details of the cycle car!

[TONY REGAN]

Thanks again,yes I felt that 6volts would be more period,just the conveince of possible battery swap from anyone as this a total loss system presently made me think 12 volts. I don't think I've ever seen one of the early coils and had imagined I'd start with small Lucas coils mounted with condensers on a plate and in a box.As the chassis is Ash timber it will be earthed back to the engine .
The car itself carries the engine inline behind the radiator and an all metal clutch is mounted on the mainshaft running a chain back to the 2-speed Chater-Lea gearbox which is hand-cranked handle through side of chassis. Then a 3/4"x1/2" chain runs to countershaft which turns two belts outside the chassis with a tension control like a large handbrake lever. Beaded edged 26" wheelsand rear brakedrums only.
Lots to do as this it's centenary,but enjoyable,thanks again, Tony

[chaterlea25]

Hi Tony,
I will have to disagree a bit with Leon's diagnosis 
I believe the setup shown is for trembler coil ignition
With trembler coils the spark occurs when the contacts close, then the trembler does its thing
(similar to a buzzing doorbell coil) this provides a series of sparks while the contact is closed

I recently set up such a device on a veteran De Dion engine
On another veteran engine I made a new cam to operate conventional contact points
Set the timing at TDC or a 32second after at full retard on the lever

HTH
John

[cardan]

Hi John,
In a trembler coil system, the trembler is part of the coil itself, as are the "points" that control the "trembling". The "timer" on the motor is then a "wiper" (make and break) rather than a set of points: when the circuit is closed, the trembler starts trembling and continues to produce a series of sparks until the circuit is broken again (maybe 20-30-or more degrees later) as the contact is broken in the timer. A trembler coil is self-sustaining i.e. if you power it with a battery the plug will spark continually even if no motor is in sight.
The De Dion Bouton system is a bit of a half-way house. It doesn't use a trembler coil - just a high voltage induction coil like the ones we're discussing here. But you are right, there is a "trembler" element to it, because the blade that holds a "point" in the middle and a contact on the cam at the far end (just like Tony's) is very springy. It is closed for about 90% of the cam rotation, but instead of a "blip" (a ramp to close the points, followed a little later by a sharper drop-off to close them and produce a spark, see Tony's photo) the DDB cam has a notch cut into it. The leading edge of the notch is sharp (think cliff) to give a fast break of the points to produce a spark. The subsequent "boing" of the blade produces more sparks (with less intensity) until smooth ramp on the tail edge of the notch brings the blade back up to the full diameter of the cam, closing the points.
The DDB system is like the modern points system. (OK, there's nothing modern about points ignition...) The DDB points are closed for most of the time, allowing the current to build up in the primary coil before the points are broken. I would guess that a DDB coil would be similar to a "modern coil".
The potential problem with Tony's system - essentially the system used by Minerva on its very successful early motors - is that the points are only closed for a short time before they open again to produce a spark. During this time, both the DC resistance and the inductance of the primary coil oppose the flow of current, but it must build up for long enough so that the abrupt cessation of the current (at the opening of the points) produces a spark.
Will this work with modern coils? That's what Tony will have to try.

Tony,
If the car is celebrating it's centenary, it was built in 1914. A trouble-free solution to your ignition problems would be to fit - even temporarily - a 50 degree magneto?
I assume the car was a one-off?
Leon

[TONY REGAN]

I'm finding this fascinating;this forgotten technology,as you say I'll have to discover how to adapt what I have into making a running vehicle. As for the idea of a 50 degree mag;well the space infront of the motor is restricted by the crossmember supporting the engine mounting ,I don't want to change too much so the idea of a "modern cam" seems a good one if there are problems with the existing one. This week I'm away from the car so I'm gathering bits and pieces necessary. I like your exchange of views and ideas on this site,thanks again,really helpful, tony

[cardan]

Three systems to contemplate: de Dion, Minerva and Bradbury all of about 1903. As mentioned above, de Dion and Minerva systems use an induction coil, while the Bradbury uses a trembler coil. The system on the JAP looks to be an "improved Minerva" system, with the points closed for a while before they break to give the spark. The wiper + trembler coil system was not much used after about 1903 because performance was poor as engine speeds increased.

Leon

[TONY REGAN]

I agree the Minerva system is similar. I happened across some what I believe to be trembler coils at week-end at an Oil Engine swapmeet nearby,some were labelled Pontiac made in nicely dovetailled cases,rather pricey and could be sure they still worked. The DDB system I came across on a website also this week-end,fascinating that items are being re-created for earliest machines. The breaker units had a similar shape to them even if cam as you say carries a notch rather than ramp. This is first time I've seen Bradbury system and seems like early ringcam...am I correct?
I hope the enormous dwell on JAP will assist a good spark once I restart the work. thanks for the images and ideas,tony