Challenge to you CNC guys

[rodekyll]

If I sent you a phonic wheel (looks kinda like a sprocket), could you duplicate it in ~1/2 size, using a simple disk (no contours) and a simple center hole?

[Matt Story]

Well, I hesitated to respond, but since no one else has...

I don't have the resources to make the item you're asking about.  I do have a load of experience designing parts for manufacturing using modern processes.  From your description, the part you're asking about could easily be made with a 2 axis water jet, wire EDM, CNC mill, possibly even a 2 axis CNC plasma cutter - depending on the specifics of the bore fit and operation.  This assuming it needs to be metal.  If plastic could be used, 3D printing may work and I could produce it in ABS plastic.

All that aside, before it can be produced by any of those methods, you need either a 2D vector drawing (Acad *.dxf, *.dwg) and/or a 3D solid model, and and specs for the fit on the bore.  By the sounds of it, creating the model should take little effort.  If you can provide the basic dimensions, I'll volunteer to produce models so you can have it produced by others.... 

Matt

[rodekyll]

I thought this would have been a lively topic.


I can give the dimensions and provide an actual phonic wheel, but I'm not a CADD jockey by any stretch.  I have no idea how to do the math for something like this.  I'll get serious about the dimensions this PM and try to have some figures tonight.

[Hymes Inc.]

Depends on how soon you want it. My older brother has all the tools needed to make this happen. The latest version of Bobcad and HAAS VF3's to do it in. What type of material are you wanting it out of?

[swooshdave]

Depending on what you are using it for it could be 3D printed.

[rodekyll]

It will be used as a phonic wheel.  It will mount in a dual-point distributor and be read from the side rather than the edge.  It should imitate a cam position pickup and sensor.  If it works it will make fuel injecting older carbbed big blocks (that don't have the sensor hole in the block) possible.  In fact, at that point it should make it a bolt-on.

Right now Matt is helping make up the model and the expression for the model.  The final product will be ferrous, unless there is an alternative sensor that would let a 3-D printed wheel be read and synched to the ecu.

There's not a time line on this, although I lose the house in a few weeks and it would be nice to tinker with it while all my tools are still accessible.  I've been collecting parts and found a NIB ducati 15M ecu the other day.  That and the success of guzzidiag is getting me hot on the experiment again. 

[swooshdave]

Although there are metal filaments (metal powder infused in the plastic) I'm not sure if that's the best use for 3D printing. Laser cutting would probably be the most accurate.

[rodekyll]

Depends on how soon you want it. My older brother has all the tools needed to make this happen. The latest version of Bobcad and HAAS VF3's to do it in. What type of material are you wanting it out of?

I'm thinking mild steel at this point, although if I can find an optical sensor that works with the ecu I might be able to go with a non-ferrous material.  Does 3D lend itself to spinning that fast?

Matt Story has generated some drawings and computer files in a variety of formats.  I can forward them to you.  They'll explain it to your brother better than I can -- Matt did a good job.  At this point it's a one-off proto design, and like I said, although it would be nice to have something in the next three weeks, there is really no timeline on the project.  It will come together as it comes together.

Thanks for your interest!

[Triple Jim]

You could use a photointerrupter at the edge.  In fact, you can buy inexpensive encoder wheels made just for things like this.  The photointerrupter has an IR transmitting LED, a gap, and a phototransistor sensor to provide the signal.  The encoder wheel's edge goes in the gap.  If you do a Google search for "photointerrupter wheel" you'll see some examples.

Personally, I'm a fan of Hall effect sensors, but those would require at least a ferrous encoder wheel like you posted about, or magnets in a rotating wheel.  Hall effect is nice because it's pretty much immune to dirt and grease, where optical systems are not.

[rodekyll]

Do you think such a sensor would hold up to the duty and environment?  I've seen them but on things like printers and scanners where they're counting slow speed turns for a few seconds. 

[Demar]

Fineline Protootyping will 3D print in metal. Matt can provide an STL file from his cad data. I'm sure it's not cheap but might be worth exploring.

Materials
We offer numerous material options through our three additive processes that are constantly updated to meet prototyping and master fabrication needs. DMLS offers parts built from five different metal materials:
�Aluminum
�Cobalt Chrome
�Inconel
�Stainless Steel
�Titanium

https://www.protolabs.com/3d-printing/direct-metal-laser-sintering/

[Triple Jim]

Do you think such a sensor would hold up to the duty and environment?  I've seen them but on things like printers and scanners where they're counting slow speed turns for a few seconds.

I've been producing a CDI system for motorcycles that uses hall effect sensors, and they've been in the field for several years now.  I put an LED on each Hall effect sensor board so you can see exactly when it triggers.  That lets you static time the engine without the need to use a timing light on it later.  The Hall sensors trigger at the same point, whether the shaft is stationary or turning 10,000 RPM.

C5 Performance (I think that's the name) is another company that sells ignition systems for motorcycles.   They use the optical encoder method of sensing.  You should be able to look up C5 and see some photos of their stuff.

But yes, either type is fully capable of sensing high speed rotation while standing up to vibration and heat, assuming the right electronics is behind them. 

[Hymes Inc.]

I'm thinking mild steel at this point, although if I can find an optical sensor that works with the ecu I might be able to go with a non-ferrous material.  Does 3D lend itself to spinning that fast?

Matt Story has generated some drawings and computer files in a variety of formats.  I can forward them to you.  They'll explain it to your brother better than I can -- Matt did a good job.  At this point it's a one-off proto design, and like I said, although it would be nice to have something in the next three weeks, there is really no timeline on the project.  It will come together as it comes together.

Thanks for your interest!

Bobcad will allow Mark to open the file and do the CAM tool passes right off your drawing. Best thing about Bobcad really.

[swooshdave]

Couldn't you use the signal from an electronic ignition to fire the fuel injection?

[n3303j]

C5 Performance (I think that's the name) is another company that sells ignition systems for motorcycles.   They use the optical encoder method of sensing.

http://www.powerarc.com
PowerArc is the company making the electronic ignitions triggered by an optical encoder. C5 is a distributor of theirs. Been running one of their ignitions in my Ural.

They use two IR photosensors. One counts a group of equally spaced slots around the disk to determine amount of rotation. The other senses a single slot that is used to establish TDC and a starting point for the ignition program.

PowerArc does sell a unit for the Moto Guzzi. They also sell a programmable module that let's you alter the parameters of ignition. Can't see why this same device couldn't be set up to trigger fuel injection timing.

They do sell their optical sensor wheels separately.

[rodekyll]

I took a look at the powerarc folks.  They do have an impressive setup.  Much more than I need.  The wheel has about 120 teeth, and the guzzi phonic wheel has 48 -2.  I don't see how the wheel would work without modification.  From their website I do get a sense of the size it needs to be in order to accommodate the sensor.  That is good.

[swooshdave]

I took a look at the powerarc folks.  They do have an impressive setup.  Much more than I need.  The wheel has about 120 teeth, and the guzzi phonic wheel has 48 -2.  I don't see how the wheel would work without modification.  From their website I do get a sense of the size it needs to be in order to accommodate the sensor.  That is good.

Can you tap into the tach signal to get the data you need?

[rodekyll]

Can you tap into the tach signal to get the data you need?

No, this is the mother of the tach signal, and the beauty of the 15M injection.  In the 15M injection it's the only engine mechanical sensor.  So it gives rpm and position info to the ecu and the ecu shares it out to whatever cares about it.  Kinda like facebook except it has to report in all the time.  Tach and injector timing/pulse are some of those things the ecu shares to.

But it's also been the obstacle in injecting legacy big blocks.  The older blocks don't have a casting for the sensor.  So for lack of a cam position sensor location, we can't throw the otherwise bolt-on 15M injection onto a pre-injected engine.

 The answer I'm pursuing (perusing?) is to use a dual-point distributor instead of the cam to house the phonic wheel and sensor.  Then you've got a "factory" bolt-on injection system just by collecting the parts from your favorite wreck.

The problem is that a phonic wheel is about the same size speed and grit as a tile blade in a cheap Makita angle grinder, and attached to a distributor shaft it spins really close to other stuff -- like the rider. 

So the answer is to make the wheel tiny and stick it inside the distributor where as long as you leave the lid on, nobody gets hurt.  How tiny depends on how big the sensor is. 

That's where I'm at now -- how tiny is one of those slotted optical sensors, does it involve a lot of circuit boards if it's not also the encoder (I think the ecu is the encoder in this model), and can the ecu read it? 

[tris]

IMO you should mosey on down to your local laser cutting company.
Water jet would probably be OK too, but it wont hold as tight tolerance as laser but at the thickness you be looking at (1/4" or less ?) it wont make a great deal of difference

The ones that I use generally have CAD capability and we're talking about a simple component in CAD terms so it shouldn't take their draftsman more than an half an hour to draw up from your sketch - heck I could draw it in 30 minutes and I'm PANTS with CAD

Then about 10 minutes to burn ten off for you 

[swooshdave]

This is the optical sensor from a GM OptiSpark used on the LT-1 engine in the 90s. In the upper right the larger disk is the one with the little holes. It's really thin steel (less than .025in) that has probably been laser cut. With an optical sensor you want as thin of a disc as you can get.

Can you post pictures of the phonic disk you have?

If you put it in the distributor what will you do with the distributor parts?

I still don't understand why you can't use an electronic ignition as the source for cam position. There are some open source electronic systems you could hack and get whatever data you need.

If I understand correctly you are looking to put the later FI from a V11 on the early big blocks? I assume they have the phonic wheel on the cam?

[rodekyll]

The efi big blocks have the phonic wheel on the cam. 

If I put it in the distributor you can have the old parts.  I'll be keeping the body, advance weights base plate, primary shaft, points plate and cap.

I'm not using the electronic ignition because they are 'encoders', which means they have logic associated with the sensing (look at a pic of the C5 pickup -- it sits on a circuit board with LEDs and other stuff soldered on) to do things like choose which pot to spark. The 15M ecu acts as the encoder for fuel injection and makes all the choices.  I have no idea what kind of signal an ignition encoder would send to the ecu.

The wheels have different tooth counts than the oem phonic wheel, and the oem wheel has a gap that I don't see with the ignition units.  I believe the tooth count and the degree sweep of the gap where teeth are missing is significant.

If I can make this work the cost will be the sensor and having a wheel made v $500 or so for a made-up version that will need wheel modifications and may or may not communicate with the ecu.

I've packed the actual phonic wheel, but here's the drawing:





It's been astutely pointed out to me that the flaw in the drawing is that an optical reader reads the opposite of what a magnetic sensor reads, that is, where the magnetic sensor reads the teeth, the optical sensor reads the gaps.  So the mistake is the missing 'teeth' need to be a missing 'gap'.

Also, the actual scale of the wheel will depend on the actual size of the sensor.

[Matt Story]

It's been astutely pointed out to me that the flaw in the drawing is that an optical reader reads the opposite of what a magnetic sensor reads, that is, where the magnetic sensor reads the teeth, the optical sensor reads the gaps.  So the mistake is the missing 'teeth' need to be a missing 'gap'.

I would take issue with this as it is sometimes, but not necessarily true.  Sensors are available with different output modes.  See this page of 'photointerupters' at Digikey.  http://www.digikey.com/product-search/en/sensors-transducers/optical-sensors-photointerrupters-slot-type-logic-output/1967053  The key would be to study the sensor in advance to know you have the one with the output you desire, and match it to the wheel.  You could invert the signal by reversing the spokes/gaps, selecting a sensor for the opposite output signal, or (sloppy) by inverting the signal with a small addition to the circuit.

Of course, I'd be happy to update the model with inverted spokes if asked.

I think the question is; What is the state of the stock sensor output when a target is present and when its not?  What are the electrical parameters of the stock sensor; supply voltage, output level?  I might assume 12V, but its possible to be something else.  I'm getting to the boundaries of my electrical knowledge.

[normzone]

IMO you should mosey on down to your local laser cutting company.
Water jet would probably be OK too, but it wont hold as tight tolerance as laser but at the thickness you be looking at (1/4" or less ?) it wont make a great deal of difference

Not my circus, not my monkeys, and I don't know your tolerance targets.

I also don't know what thicknesses laser is capable of these days, but worst case scenario, your guy should know the tolerance range he can keep the water jet machine in. If you don't like the numbers, you could design it to cut to the upper end of what he knows he can reliably hit, then fine finish it by hand as required.

[swooshdave]

As I'm not familiar with the distributor I didn't know there was ample room to add the phonic wheel and sensor, hence the suggestion to use an electronic ignition.

Are the V11 parts inexpensive enough to make this worth while? How do they compare to something like a MicroSquirt system?

[rodekyll]

I've estimated the cost of a conversion based on purchases I've made from ebay and figure without this part, it's in the ballpark of $650.  That includes throttle control stuff.

I have no idea how the microsquirt works.  This would work exactly like oem because it uses all oem parts except the mod to the dizzy.

Matt- I'm in no position to disagree with anyone about optical sensors.  I want to go simple and direct with as little cost as possible, still making a reliable position sensor.  It matters naught if it's a positive or negative sensing, as long as it send a simple signal the ecu can read.

Roy is finding some examples for me.  I'm still trying to find out what the ecu is listening for.  Which of our guzzidiag guys knows that?

[charlie b]

FWIW, laser cutting vs water jet vs machining.

Laser cutters for metal are high power and expensive (the one I use for wood cutting was $30k).  Especially if you want to gut anything close to 1mm.  Prices have come down but most shops can't afford them, and those that do 'book' them for production.

Water jet is more common.  Not quite as accurate, but, it doesn't warp thin steel and is fairly inexpensive.  Most shops with water jets will do custom work without much of a markup.  I would go this route.

Machine cutting is easier to find and cheaper, but, works better with thicker/stiffer material.

Plasma will work, but, you have the heat issues to deal with.  Maybe not a problem for this application.

I'd not use plastic for this application.

But, carbon fiber is a possibility.

PS don't forget that the 'hub' portion of the wheel is as important as the teeth, especially when fitting a thin disk to a shaft.

[Chuck in Indiana]

No offence intended, but that drawing is either not drawn to scale, or it's dimensioned incorrectly. That said, you wouldn't need a CNC to make that, just a knee mill, a dividing head, and some patience. 

[Matt Story]

None taken.  No attempt was made to make the pdf to scale. It was not intended to feed the cnc, only to be human readable.  The native CAD formats provided are however to scale.  At this point the wheel will most likely need to be scaled down from the indicated dimensions so the current models are likely moot.

Waterjet is more precise than the part needs and steel is the way to go.  A hub can be easily tack welded or silver soldered to it.

[Howard R]

I've never looked at a Guzzi system on an oscilloscope, but AFIK they are all variable reluctance type pickups.  The following is purely theoretical, results not guaranteed, your motorcycle may vary, etc. 

A coil of wire is wound on an iron core, and a small permanent magnet is placed on one end of the core with the other end close to the "phonic wheel" or whatever is used.  (The permanent magnet is why some of them have a tendency to catch steel "swarf" necessitating the occasional cleanup.  Cheap and simple, no external power required.)  As a tooth on the wheel approaches the pickup, the magnetic flux density changes due to the proximity of the metal tooth to the pickup core, thus inducing a voltage in the pickup coil.  The voltage will  rise as the tooth approaches and suddenly switch polarity and decay away as the tooth departs.  Output voltage will change as RPM rises, voltage is proportional to d-phi/d-t, the time rate of change of magnetic flux density, for those of you following at home on your Jr. Wizard physics set.  Voltage could be fractions of a volt at low RPM to a few/several volts approaching red line.  The tooth flying by the pickup faster makes more voltage.  Presumably the ECU input is set up to deal with this.  Questions which determine whether it will work or not in your application include output pulse width and frequency.  If the wheel (and thus the tooth) is too small, output signal will be small and fast so the ECU detection circuit might not see it.  Similarly if the frequency gets too high the detection circuit might be overwhelmed and can't figure out the individual pulses.  The reason for one missing tooth is to make one piece of the waveform look "different" so the ECU can use that to figure out where TDC is. 

For example on the Digiplex system (at least as implemented on a '96 Sport 1100) there are four lumps sticking out from the edge of the flywheel.  One lump is actually two close together, to make that one look different.  This system will fire the plug every time TDC comes around, since it has no way to know which one is compression.  Theoretically, having a spark blown out the exhaust wont hurt anything, other than inconveniencing a few more electrons.  The more complex ECU system uses the cam phase with more teeth so it can divide one rotation into smaller chunks, to more closely figure out when to do what.  (Squirt the injector, fire the plug, whatever.)

Hope this helps.

Howard

PS
I found a pretty good write up on the Megasquirt site, it starts off with a generic description of pickup operation.
http://www.megamanual.com/ms2/pickups.htm

[swooshdave]

So scaling down the wheel to fit inside the distributor may not work because it will change the size of the teeth and thus the signals to the ECU? I was wondering about that.