How to set up a Distributor

[scooby]

Before I spin the crank around to set the valve clearance, I think I should install the distributor cap while the #1 piston is at TDC (I know my cylinder numbers are labeled wrong, but I had other parts/pics referenced to it before I realized it, so kept it to avoid confusion)

My question is, how do I set the distributor up? There is a gap between the outer rivets and contact arm, so with cap installed I can't check for continuity with mutimeter.

What is the step by step process to set up a distributor? (magnet disk w/hall sensor ( what leads on hall sensor I connect multimeter to test) and the cap?

Thanks

 

[mayhugh1]

The rotor and the trigger positions are independent and set separately. First, set the trigger position. Rotate the Hall mount and/or the distributor rotation so the Hall device triggers at your desired initial timing setting for cylinder #1 which may be, say, 10 deg BTDC for cylinder #1. Use a dial indicator in combination with a probe extension inside the #1 plug hole to locate this point. You'll need to hash together a trigger wheel with an external pointer and temporarily attach it to your crankshaft so you can keep track of this TDC and also know where your 10 deg (or whatever) point is. Alternatively, you can put a reference mark on your flywheel at TDC for cylinder #1 and then compute the angular location of the 10 deg mark. Just be aware that the flywheel marks are only valid so long as you don't remove and re-install the flywheel. After the trigger position is determined and the Hall mount and distributor location locked down, you can then set the rotor position. So long as your rotor contact is wide enough, eyeballing it to the center of a tower electrode should be sufficient. The rotor contact should be pointing directly at one of the tower electrodes when the cap (hopefully keyed for consistency) is replaced. This tower then becomes the tower for your #1 plug wire. Install the other plug wires consistent with your rotor rotation direction and engine firing order. Lock down the rotor setscrew and you should be good to go. - Terry

 

[scooby]

If I understand you correctly,

To set #1 10 deg BTDC like you said I attach the degree wheel and use it to move 10degrees BTDC.

To test when the Hall Sensor is being triggered I send 5v to pin 1 , ground to pin 2, and put multimeter leads on pin 2 and 3

I rotate magnet disk so that I see it (#1) is being triggered

I then tighten screw that holds mag disk, then eyeball the contact strip to center of tower electrode (rivet in the distributor cap)

In the plans, Jerry Howell says "I set the distributor timing up so that spark is at TDC with the throttle about a 1/3 the way open"

So could I leave piston #1 at TDC like it is now, set up the hall sensor and distributor cap, then I attach the throttle linkage to distributor while the throttle is 1/3 open? Or is it better to do 10 degrees BTDC?

Thanks so much for your help

 

[mayhugh1]

I'd forgotten that Jerry provided for a mechanical linkage between the throttle and distributor to provide mechanical advice. Therefore, I'd set it up as he suggests with 0 deg BTDC and then get the advance from the linkage when running. - Terry

 

[scooby]

For the throttle linkage, the holes in the throttle arm are .035 and the ones in the distributor spark advance arm are .050

I was thinking of threading one side of both the end pieces 2-56, then turning ends to .035 and .050 and bending them.
Then use some hex stock to make the green pieces and tap 2-56 through.
Then make a nut (orange) to lock

Is there a better way to make a linkage or will this method work?

 

[mayhugh1]

For the throttle linkage, the holes in the throttle arm are .035 and the ones in the distributor spark advance arm are .050

I was thinking of threading one side of both the end pieces 2-56, then turning ends to .035 and .050 and bending them.
Then use some hex stock to make the green pieces and tap 2-56 through.
Then make a nut (orange) to lock

Is there a better way to make a linkage or will this method work?


View attachment 135479

You might think about LH threading the rod on one and RH threading it on the other. That way you can adjust its length and therefore the initial advance setting insitu. - Terry

 

[scooby]

Does that mean I have to get a left handed tap?

 

[mayhugh1]

Does that mean I have to get a left handed tap?

It would ... Terry

 

[petertha]

You could check some RC suppliers. Reverse threaded turnbuckles & pushrods are quite commonly used on heli's & cars. Probably have some nice ball ends & clevises too if that's of interest. Now whether they add up to more $ than a tap or a die I can't say. Note that the airplane guys use something quite similar but both ends are same RH thread, so not what you want. Might be called couplers or pushrods, can't recall.

 

[scooby]

Currently working on assembling the throttle body, and the way it is right now, the lever arm for throttle moves to the right (CCW) when going from idle to full throttle, so it would pull the distributor lever arm in the same direction (to the right).

This next pic is top view of distributor. Is this correct in regards to the direction the throttle lever it is pulling on the distributor lever?

 

[Bentwings]

Currently working on assembling the throttle body, and the way it is right now, the lever arm for throttle moves to the right (CCW) when going from idle to full throttle, so it would pull the distributor lever arm in the same direction (to the right).

View attachment 135503


This next pic is top view of distributor. Is this correct in regards to the direction the throttle lever it is pulling on the distributor lever?
View attachment 135507

i had a couple of gas engines with variable timing as you are showing . They retarded the timing at idle for easier starting . I think the modern electronic ones do it internally . The ones I had were disconnected eventually . Magneto starting was a matter of flipping the prop fast enough to get a good solid spark at the correct timing point there was rarely a kick back unless you “ weak flipped” it the engines did idle down better but it realy was not necessary it was harder to get them back up to speed. Ultimately testing showed about 28 deg advance was good for about all speeds generally idle was about 2,000 give or take. A well used engine often could idle below that with a heavy prop or spinner. With 8,000 about max for most Rc engines. It seemed like there was enough compression that at lower speeds there just was not enough inertia to have the prop coast through top center I still have one mechanical advance that operates as you show . I don’t remember the exact amounts. It’s a very strong running engine even with modified ports. I didn’t do that part . I have a couple electronic ignitions but they run pretty well set at 28 deg total. I’m not sure why this number works. I think it has to do with how fast the flame front burns on gas . Nitro and alcohol are different . I just made adjustable fixed advance and ran the engines at full throttle then slowed them down adjusting the carb as required. I YHINK most yard small engines run about the same. It’s been a long time since I put a timing light on one


Byron

 

[scooby]

I got a PICTIM ignition Module from Howell, it says that its programable, but I can't find how to do it or what I need to do it for. Does a ignition module that's programable take the place of having the linkage connecting throttle body do distributor?

 

[Bentwings]

I got a PICTIM ignition Module from Howell, it says that its programable, but I can't find how to do it or what I need to do it for. Does a ignition module that's programable take the place of having the linkage connecting throttle body do distributor?

I think that’s what they are trying to do . I just question it
Look at weed eaters they idle ar very low rpm then come alive the same with chain saws if you have a timing light that works with either magneto or electronic it would be interesting to see what goes on I just don’t remember when I tried this . But it was the basis for getting rid of a mechanical system , that was problematic at best . My Rc lanes idle was about 2k give or take as the engines got more miles on them the idles became more consistent . Carb adjustment seemed more important most yard stuff has pretty heavy flywheels where Rc have relatively light spinners or heavier props a 3 blade carbon fiber prop is still pretty heavy even a 22” wood prop is beefy.

Byron

 

[mayhugh1]

I got a PICTIM ignition Module from Howell, it says that its programable, but I can't find how to do it or what I need to do it for. Does a ignition module that's programable take the place of having the linkage connecting throttle body do distributor?

I just checked out the PICTIM (hadn't before heard of it before your comment) on their website. There's no automatic timing advance, but they claim it's a possible future addition. I think the only programmable feature is a jumper to convert between a single spark firing mode and a multi-spark (buzz box) firing mode. You'll want the single spark firing mode. - Terry

 

[Bentwings]

You might think about LH threading the rod on one and RH threading it on the other. That way you can adjust its length and therefore the initial advance setting insitu. - Terry

I had a number of mechanical advance ignitions and probably had issues with every one . About all they did was allow a bit slower idle. And maybe a little easier starting. Almost all of the Rc model engines I’ve checked had about 28 deg total advance . More or less reduced power one with advance might idle slower but after a while you adjusted the needle valves and they idled fine I seen a lot of mech advance backfire and quit when throttle was applied resulting in dead stick landings. If you look at today’s lawn equipment they all idle down nicely . If they have built in electronics , we’ll great but I’ve gone through many two stroke an 4 stroke magneto engines that ran fine all their life .
Byron

 

[scooby]

Need some help understanding something...

In the V4 plans, on sheet #63 it shows this:

The rotor viewed from top rotates clockwise. I rotated engine CCW from flywheel end of engine and the magnet disk rotates clockwise just like plans say.

It also says firing order is 1-4-3-2.

If the hall sensor( in pic where wires are) is being triggered by #1 magnet and magnet disk is rotating clockwise, wouldn't the next magnet to be triggered be magnet #2 according to sheet #63?

On the magnet disk, should 4 change to 1, 1 change to 4, 2 change to 3, and 3 change to 2? That would make firing order 1-4-3-2?

 

[bluejets]

Dissy distributes the high tension, not normally to do with any hall effect.......think you've something misunderstood there.

 

[Bentwings]

Dissy distributes the high tension, not normally to do with any hall effect.......think you've something misunderstood there.

I have to agree. I’m confused. Normally one magnet is on the crankshaft or crank pulley . The sensor is mounted on an adjustable mount . It is usually set some amount before top dead center. Say 5 deg. Then the distributor is wired in firing order. It’s pickup is set by rotating the dizzy to trigger the electronics so it triggers just as the crank mag and sensor trigger . Thus creating a slight advance timing this is in turn adjustable by rotating the dizzy. The crank trigger is left alone. It sometimes is positioned at TDC thus leaving all advance up to the dizzy position. If I’m understanding the pictured setup this is completely reversed. Thus the confusion . If I’m incorrect please feel fr to advise me an automotive dizzy has the initial advance built in by adjusting the electronic pickup. Generally this is not done as mount holes are fixed. In automotive the pickup plate could be hooked up to a vacuum advance thus providing an operating condition adjustment these occasionally were adjustable too but really just forget that complication for now. Some dizzy use optical sensors so a window device called reluctor is used this is timed as an on off switch just as a hall switch .


It may be best to look at the dizzy as a points style the points being replaced by more modern electronic switching

Byron

 

[bluejets]

I don't have any copy of what you are referring to so cannot comment.

Yes, in a single coil system, there would normally be just one hall effect to switch the spark.
Dissy is used to distribute that spark from the centre pin to the surrounding pins at the right time, and in the right order.
This order is dependant on the way the cam is ground (valve timing) and in the direction the engine runs.
Any electronic advance would have the distributor locked in some predetermined position, perhaps maximum advance, and the delay the spark a certain time after the hall is detected depending on the rpm via a lookup table in the programming.
While electronic advance is possible there are actually very few that work all that well, and the programming is complex if at all successful.
Better, I think, to stick with your manual advance.
While that may not be as "ideal" for changes in environmental properties, it's just a model engine after all and not a drag car with Nth degree of precision required.

 

[Bentwings]

I don't have any copy of what you are referring to so cannot comment.

Yes, in a single coil system, there would normally be just one hall effect to switch the spark.
Dissy is used to distribute that spark from the centre pin to the surrounding pins at the right time, and in the right order.
This order is dependant on the way the cam is ground (valve timing) and in the direction the engine runs.
Any electronic advance would have the distributor locked in some predetermined position, perhaps maximum advance, and the delay the spark a certain time after the hall is detected depending on the rpm via a lookup table in the programming.
While electronic advance is possible there are actually very few that work all that well, and the programming is complex if at all successful.
Better, I think, to stick with your manual advance.
While that may not be as "ideal" for changes in environmental properties, it's just a model engine after all and not a drag car with Nth degree of precision required.

Sorry I must have missed a key or something when I posted.

Byron