Tinbasherdan
Bodger in chief
- Messages
- 7,236
- Location
- Bolton, England
thanks, thats great. not too sure i understand it but i suppose it just wont work if i get it wrong!
- Thread starter Tinbasherdan
- Start date
Farside
Badly Welded Man
- Messages
- 5,733
- Location
- Ireland
I suggest an HEI module. Dirt cheap and reliable, especially the OEM ones.
Tinbasherdan
Bodger in chief
- Messages
- 7,236
- Location
- Bolton, England
the question is now who would be willing to build me the driver as shown by eddie 49 for some beer tokens? my electrical ability is not up to it i fear, and id rather have a plug and play driver that i know will work!
Tinbasherdan
Bodger in chief
- Messages
- 7,236
- Location
- Bolton, England
any volunteers?
Tinbasherdan
Bodger in chief
- Messages
- 7,236
- Location
- Bolton, England
possibly, although space is quite tight and a solid state setup would be more reliable
ajlelectronics
Forum Supporter
- Messages
- 9,528
- Location
- Gloucester, England
Possibly, if I can find time.
HughF
Member
- Messages
- 6,468
- Location
- Work: Dorchester, Workshop: Corfe Castle, Wife's place: Frome
I might be able to spare the time to lay this out as a circuit board for you, but don't hold me to that.... I've got a 4hr flight to get through on Saturday and I could probably smash it out then. It would be cheap to get a small run of boards made in China
What is the point of tremblers? Unless I am missing something you still need to time the spark, as too early and it will just backfire. Also, if you don't have a two plug per cylinder engine, you are firing the magneto voltage back through the coil, and the coil HT voltage back through the magneto. Making a trembler isn't the problem, model Ts simply used an electric buzzer type electro/magnetic relay in place of the contact breakers of conventional systems, it is timing the spark(s) and whether two HT leads per plug will work without destroying the mag.
Tinbasherdan
Bodger in chief
- Messages
- 7,236
- Location
- Bolton, England
the distributor has a secondary set of contacts that bypass the coil etc, and also retard the timing. im not 100% on these systems, im a diesel man myself and every time i touch the ignition side of an engine build i get a belt off it, so i stay away!
Wallace
Member
- Messages
- 7,705
- Location
- Staines, Middlesex, England.
I’m quite happy to be corrected on this, these engines have big cylinders to fill and are being asked to run with different fuel to what they were designed for so starting may be quite different. A burst of sparks gives a better chance of ignition, nothing new these days on modified engines pushing for power, on an old maybe tired out of service engine every little helps.
Tinbasherdan
Bodger in chief
- Messages
- 7,236
- Location
- Bolton, England
i wouldnt get caught calling peoples engines tired!! they required them when new, in fact almost all, if not all piston engined aircraft with mags have booster coils of some description
Tinbasherdan
Bodger in chief
- Messages
- 7,236
- Location
- Bolton, England
Since the booster will only be used for a few seconds when starting, a simple relay wired as a buzzer or vibrator ( as suggested by 500e ) will be sufficient:
Use a 12v car-type relay ( e.g. headlight/foglight relay ). Wire the primary of an ignition coil ( T1 ), and the relay coil ( RY1 ), through the normally-closed contact. When power is applied, the relay pulls in, opening the contacts and spiking the coil. With the contacts now open, the relay loses power and drops out, the NC contacts close again, the sequence repeats. Capacitor C1 is from a standard points-type car distributor ( "condenser" ). Wire the HT output of the ignition coil to your distributor from the top of the coil and the negative end of the primary.
As merryman said, you DO need to time this HT spark to the crank position ( especially as aero engines can apparently be timed for 25 deg. BTDC ), else you will get a serious backfire. The "vibrator" circuit above should be powered through the second set of points on your distributor, which will be retarded to TDC or later. Joining the magneto and the ignition coil outputs together should be OK. The secondary of an ignition coil has a resistance of about 10K Ohms, and the magneto HT would rather run to ground at the spark plug.
The links provided by 500e in Posts 6 and 7 show circuits for "vibrating" the magneto primaries, without the need for an extra ignition coil.
Use a 12v car-type relay ( e.g. headlight/foglight relay ). Wire the primary of an ignition coil ( T1 ), and the relay coil ( RY1 ), through the normally-closed contact. When power is applied, the relay pulls in, opening the contacts and spiking the coil. With the contacts now open, the relay loses power and drops out, the NC contacts close again, the sequence repeats. Capacitor C1 is from a standard points-type car distributor ( "condenser" ). Wire the HT output of the ignition coil to your distributor from the top of the coil and the negative end of the primary.
As merryman said, you DO need to time this HT spark to the crank position ( especially as aero engines can apparently be timed for 25 deg. BTDC ), else you will get a serious backfire. The "vibrator" circuit above should be powered through the second set of points on your distributor, which will be retarded to TDC or later. Joining the magneto and the ignition coil outputs together should be OK. The secondary of an ignition coil has a resistance of about 10K Ohms, and the magneto HT would rather run to ground at the spark plug.
The links provided by 500e in Posts 6 and 7 show circuits for "vibrating" the magneto primaries, without the need for an extra ignition coil.
