NB Electronic ignition for a twin cyl bike

[Heckler]

My buddy goes racing with his classic Weslake. The ignition is an expensive box with an internal battery and a spark "generator" Basically a Halls effect sensor and the box reacts to this to produce the spark. Now, if I was to get a halls sensor, a lost spark twin coil, a thyristor, and a battery I could make a spark BUT it would be a fixed advance spark, ie for the twin it needs to be 28deg BTDC at about 4000 revs. So how could I generate the spark to fire at TDC at start up,and advance it slowly as the revs build through electronics means?
Stu

 

[lw395]

Either some sort of magnetic system where a shaped rotor causes a pickup coil to reach a certain voltage earlier at higher rpm (that's how the aftermarket ign on my guzzi worked), or a digital system with multiple sensing pulses per rev, often a gear with a few teeth missing.
Google 'megasquirt' for diy systems.

 

[rotrax]

Why bother?

There are many race proven self generating motorcycle ignition systems around.

If carrying a small battery is not a problem the range becomes greater and the price lower.

On most the advance comes as a direct result of the steeper flank of the triggering sine wave tripping the thyristor earlier as the revs rise.

With digital programing this can be arranged to be whatever you want I imagine.

To develop and test to the standards required in modern classic racing will require a lot of time and effort and will only reproduce what is available.

For a Weslake-single, vee twin or parallel twin-my preference would be for a simple coil ignition system with a battery big enough to last all day.

Spare parts can be carried, and in the case of condensers, fitted on the bike ready to be switched to should there be a fault in this area.

I have some experience in this field, and self generating sets are expensive to purchase, and expensive to carry spares for.

My youngest son had a Weslake speedway bike untill he decided to pack it up. When I got the engine the " Magic Box " was a bit iffy so I converted it to coil ignition using a battery from an electric start 50cc scooter.

It would run all day at a Speedway training day-as long as it was switched off after every session...............................

If this was forgotten, flat battery!

 

[Heckler]

Why bother?

There are many race proven self generating motorcycle ignition systems around.

If carrying a small battery is not a problem the range becomes greater and the price lower.

On most the advance comes as a direct result of the steeper flank of the triggering sine wave tripping the thyristor earlier as the revs rise.

With digital programing this can be arranged to be whatever you want I imagine.

To develop and test to the standards required in modern classic racing will require a lot of time and effort and will only reproduce what is available.

For a Weslake-single, vee twin or parallel twin-my preference would be for a simple coil ignition system with a battery big enough to last all day.

Spare parts can be carried, and in the case of condensers, fitted on the bike ready to be switched to should there be a fault in this area.

I have some experience in this field, and self generating sets are expensive to purchase, and expensive to carry spares for.

My youngest son had a Weslake speedway bike untill he decided to pack it up. When I got the engine the " Magic Box " was a bit iffy so I converted it to coil ignition using a battery from an electric start 50cc scooter.

It would run all day at a Speedway training day-as long as it was switched off after every session...............................

If this was forgotten, flat battery!

Ta for the info. He uses an Interspan, works ok but expensive. £600? I got to looking at it and thought, hall effect sensor, thyristor, coil and lithium battery. But was wondering did any one have the expertise to point in the direction of how to do programmeable advance. I know all about simple ignition systems, think angola, american ford pick me up with a very basic early electronic ign system. It went tits up, the shade tree mechanic was treating the little dist pickup coil as a set of points! I found a ford wrecker with a points setup on it. The base plate was exactly the same size, a landy coil and some bits of wire soon got it runing. The shade tree mechy was amazed!
Stu
PS Hope to give Guy Martin a bit of a run for his money!

 

[rotrax]

Stu
PS Hope to give Guy Martin a bit of a run for his money!

With the spanners or on the track?

First Mate and I are planning to visit the IOM for the Classic TT in August, sailing from Belfast.

My old mate Steve Linsdell's boy Oliver won on a Paton last year, beating all the top guys.

Couple of years back he was nearly killed there after a REALLY high speed crash.

Getting back to your friends bike, a coil ignition system with a switching box-Boyer Bransden ID unit-a good high output coil and a high capacity battery would be my preffered route.

The Interspan "Magic Box" was made to deal with the very high compression speedway engines af the seventies and eighties. The guts inside are quite old tech and very simple.

The internal Ni-Cads dont last long in other disiplines in my experience, causing missfires and poor starting and even total failure when in the lead.

Ask me how I know..............................

 

[William_H]

Advance with engine RPM. Cars used to use vacuum advance along with I think centrifugal weights that rotated the points plate.
Modern cars use a computer to sense the engine speed then use a look up table to decide on spark advance.
A microprocessor could be used to put in a variable delay from the Hall sensor to get just the right advance at various speeds.
You could aslo make a steam driven advance by fitting a series of Hall effect sensors around the inside of the flywheel with an angine RPM detector that would select the correct Hall sensor. just a thought olewill

 

[rotrax]

Advance with engine RPM. Cars used to use vacuum advance along with I think centrifugal weights that rotated the points plate.
Modern cars use a computer to sense the engine speed then use a look up table to decide on spark advance.
A microprocessor could be used to put in a variable delay from the Hall sensor to get just the right advance at various speeds.
You could aslo make a steam driven advance by fitting a series of Hall effect sensors around the inside of the flywheel with an angine RPM detector that would select the correct Hall sensor. just a thought olewill

The vacuum advance on cars was purely an economy device-the ignition advanced at periods of high vacuum, ie small throttle openings, so is of no use on a race engine-unless fuel consumption and not speed is a requirement. Hot and tuned cars would have a special distributor without the vac advance.

The OP's friends bike will only require advance once it is started. Trying to start a Weslake-of any type-with petrol as a fuel will be tricky without starting rollers, hence the need to retard it a little for reliable starting.

Speedway bikes have Methanol as a fuel. If the throttle is kept closed a bump start is easy, as is pulling the rear wheel by hand. The much slower burn speed of Methanol accounts for this, even though the timing is required to be set further advanced to compensate for the slower burn to allow full power.

I like the OP's enthusiasm, but what he is suggesting can be purchased readily from a number of specialists and is proven in the heat of top competition.

In my experience, starting from scratch when the technology has existed for many years in a constantly improving and dynamic sport is unlikely to be fruitful.

Come up with a totally new type of ignition that is foolproof, reliable at the highest level and inexpensive to buy-I'll put money in that!

 

[nortonmotors]

May I suggest a 'black box' controller, made by www.minimagneto.co.uk for 12 volt coil systems on Norton rotaries, but will adapt to virtually any engine. It has a programmable chip that can include any advance/retard curve and rev limit. Not expensive, 100% reliable, and usually available programmed in ten days. If you need a different retard curve, simply fit an exchange chip. Driven by an automotive Hall-effect sensor, either Honeywell or Cherry.
I have one on my own bike, and have fitted more than 20 to customers' machines.

 

[Heckler]

With the spanners or on the track?

First Mate and I are planning to visit the IOM for the Classic TT in August, sailing from Belfast.

My old mate Steve Linsdell's boy Oliver won on a Paton last year, beating all the top guys.

Couple of years back he was nearly killed there after a REALLY high speed crash.

Getting back to your friends bike, a coil ignition system with a switching box-Boyer Bransden ID unit-a good high output coil and a high capacity battery would be my preffered route.

The Interspan "Magic Box" was made to deal with the very high compression speedway engines af the seventies and eighties. The guts inside are quite old tech and very simple.

The internal Ni-Cads dont last long in other disiplines in my experience, causing missfires and poor starting and even total failure when in the lead.

Ask me how I know..............................[

On track! The Weslake is small, nimble, weighs about 120 kilo and is putting out well over 100 bhp at the back wheel. The rider is v good, the only issue is that the XR69 Suzy can be a bit of a "ringer"!
Your mates boy done well! The Weslake did much the same when they beat Rutter in the Battle of the Twins, Ducati werent happy! Then one if his won the Japanese BoT. He knows how to put them together!
He is running 13.5 to 1 on Avgas so I see why he uses the Interspan now!
I am doing this as an idea thing, I like fiddling and as you say, a reliable hi output device at the right price?
Stu
PS The Minimagneto thing looks interesting as a start. Ta v much

 

[Heckler]

The vacuum advance on cars was purely an economy device-the ignition advanced at periods of high vacuum, ie small throttle openings, so is of no use on a race engine-unless fuel consumption and not speed is a requirement. Hot and tuned cars would have a special distributor without the vac advance.

The OP's friends bike will only require advance once it is started. Trying to start a Weslake-of any type-with petrol as a fuel will be tricky without starting rollers, hence the need to retard it a little for reliable starting.

Speedway bikes have Methanol as a fuel. If the throttle is kept closed a bump start is easy, as is pulling the rear wheel by hand. The much slower burn speed of Methanol accounts for this, even though the timing is required to be set further advanced to compensate for the slower burn to allow full power.

I like the OP's enthusiasm, but what he is suggesting can be purchased readily from a number of specialists and is proven in the heat of top competition.

In my experience, starting from scratch when the technology has existed for many years in a constantly improving and dynamic sport is unlikely to be fruitful.

Come up with a totally new type of ignition that is foolproof, reliable at the highest level and inexpensive to buy-I'll put money in that!

This looks exciting! http://www.fmsh.com/xqitadmin/uploadFiles/20120306035007.pdf
What I need now is one of the YAPP boys to build it for me!
Stu

 

[rotrax]

This looks exciting! http://www.fmsh.com/xqitadmin/uploadFiles/20120306035007.pdf
What I need now is one of the YAPP boys to build it for me!
Stu

Looks like a modern capacitor discharge system.

Well worth following up.

Might be worth talking to Rex Caunt who makes a self contained self generating ignition set popular in classic racing for replacing old worn out low efficiency flywheel magneto systems.

He might be a source of help with it.

I rode a 400cc Kawasaki sidecar outfit in the Welsh Two Day Enduro in the seventies-76 IIRC.

We camped by the Park Ferme near the lake at the start in Llandrindod Wells.

There was a rider and passenger with a pretty rough looking Norton Wasp outfit, powered by an 850 Commando donk.

They were towing it behind a long wheelbase Land Rover but could not get it to go.

I had a look and did not recognise the ignition equipment fitted.

I asked the owner/rider what ignition set it was, and was amazed at the answer. He said " Its Crowbar ignition mate-supposed to be the best there is. "

Later that evening he pulled the rotor and stator and found they had been rubbing together due to not being fitted correctly.

He asked me to look at it to see if it could be fixed.

With the bits in my hand I saw it was a modified set up from a Yamaha TZ 350, made in Germany, and at the time it was as good as you could get.

It was not, as he kept telling me "Crowbar " ignition but Krober............................