I must have checked the runout on mine 20 times during the process of making the twin crank...

But it was worth it. Mine runs so smooth you can't see a jiggle in the fuel in the tank when it's running, nor feel any vibration at all in the test stand.

Hang in there,
AV8TOR

We checked the balance on the crank it was right on the money and by looking I could not see any deflection.
even when it was installed in the block it looked good.

Only then the Prop Hub was installed could I detect that it was not true

It is bent fron the crank's counter weight to the tip. actually from the front bearing out.

It must of took one heck of hit before we got it.

From your picture I would check the runout at the end of the taper near the first thread. I bet you will have less there. Did you check the prop hub for runout? If the lathe is off center the slightest amount it will turn a taper. Also remember that when you check the runout and you indicate .012 TIR you are really measuring only half that or .006 each side of center. Not as bad as you think.

What type of electronic ignition are you guys using on these twins ?

I use the original CH ignitions. May try the new imported ones they have at some point. The original ones cost a bit more but they are repairable. The imported ones are potted in epoxy so if you crash it or something goes wrong internally you toss it.

Sounds good, but the CH ignition only have up to twins. What if someone were to make more than just twin cylinder ? :P

Uh oh... You tease. What have you got in mind there?



AV8TOR

A flat 4 Boxer is easy just use two ignitions or make a distributor

In a pinch you could also use two single ignitions for a twin.

V-4 engine ...

Can't wait to see it!!

Actually, I did consider putting two of the BME 23.6cc twin crankcases together....

AV8TOR

Keith at BME just told me he sold all the twin 23.6cc crankcases he had to someone in California who was going to save a couple for me. Could that person please contact me??

Thanks,
AV8TOR

I have ran 2 4500ma "D" cell batterys for a couple of years for my glow stick.

I was sure it would light both glow plugs ... WRONG.

I'm not sure why it won't, but 1 battery really lights up one glow plug.
So why won't 2 batterys light up 2 glow plugs ?????

Try hooking them (both the batteries and the glow plugs) up in series.

That way the voltage requirement doubles, and it will have double the voltage with the batteries in series, but the amp draw drops in half. Two plugs wired in parallel can draw over 6 amps, which is quite a bit. My power panel won't deliver it unless the 12 volt field box battery is full charge.

AV8TOR

a two stroke V4 will take 4 single ignitions...And be very long, each crankcase must be isolated.....

The case of the glow plug is a ground.

So how can I wire that in series?
It would have to be in center out case in center out case to be in series.

Or am I missing something?

Yes but if you put two of these cases together you could have a power stroke twice an revolution.

The trick would be putting the 2nd set of cranks together with the 1st set.

Sure you can wire a twin cylinder engine's glow plugs in series.

Battery positive to one plug center terminal. Current flows from there, through the glow plug to the engine. From there it flows through the engine and the shell of the other plug, through the other glow plug to the other glow plug center terminal. That terminal is then connected to battery negative. Bingo, a series circuit.

The engine itself is NOT connected to battery negative.

AV8TOR

I don't know how I missed that one.

But I had the answer fall into my lap this morning. A different battery.

It has 3 cells each cell 2 volts, not the regular 1 1/2 volts.
I'm able to use each cell separately, the 2 screws on top are the post for the center cell.
Each cell is 4" tall and a diameter of 1 3/4"

It lights one plug brighter than I ever saw a plug glow before and
when it lights the 2nd plug they are still very bright.

There are no markings on the battery only the + and the -

It came as 6 cell hooked together but was cut apart because one of the cells went bad.

If someone could ID this battery it would be helpful when it came time to charging it

2 volts per cell sounds like a sealed lead-acid battery. One of the nice things about lead-acid batteries, is that they like to be kept charged and not go through discharge/charge cycles. We used to keep them on trickle chargers continuously. John

It looks like a miniture Optima battery.
I understand they are different than a lead acid battery.

Do you think I can charge it with my Hobbico Field Charger MkII ?

The Optima battery is a lead-acid battery. The main differences are the configuration of the electrode and the way in which the electrolyte is retained using a glass mat.

See: http://www.dcbattery.com/wetdry.html
http://www.optimabatteries.com/publi...eep_cycle.html

From what I read, they can be used as drop-in replacements for conventional car batteries. That would imply they can be charged with the same charging system as is used for a conventional lead-acid battery.

I have no experience with the Hobbico charger and don't know if it has settings for automatically charging lead-acid batteries.

John

How does one charge a 2 volt lead acid battery?

I use the Triton charger. It charges as few as one cell of various types, including lead-acid. Before that, I had a charger that had a higher minimun number. I just made a charging tube out of PVC with brass srews in each cap for connections to charge 3 or 4 cells as the needed. However, you have a 3-cell pack. I would just connect them in series and charge them as a 6V lead-acid pack. John

Here are some pictures of a welded crank.