Finding TDC the easy way

[ndutton]

A while back we had a tool concept for finding the compression stroke in a cylinder, critical when setting timing from scratch, without peering or inserting anything into the spark plug hole. Remember this?

Well it struck me as a pretty cool idea so I finally got around to making one and testing it out. I sacrificed an old spark plug by breaking off the porcelain, drilling out the electrode and grinding off the arm on the bottom, added a balloon to the top, threaded it into the #1 spark plug hole finger tight only and turned the engine over by hand. Once you know you're on the compression stroke you view the crankshaft roll pin for vertical alignment.

Way cool.

[roadnsky]

Neil-
IF you decide to mass produce...
can we have a variety of color choices on the balloons?

[ndutton]

Neil-
IF you decide to mass produce...
can we have a variety of color choices on the balloons?

Yes, you may . . .

[roadnsky]

Yes, you may . . .

I'm ALL IN!

[Sam]

Very cool. Only thing I can add is that on this site you will either "learn" or get "entertained".

[GregH]

Very cool. Only thing I can add is that on this site you will either "learn" or get "entertained".

And that is why they call it enterlearnment!

[CajunSpike]

You must also consider the oxygen permability of the rubber as to the accuracy of the device. More or less rubber thickness may distort the results.









:-)

Yes I'm kidding.

[ALMA]

TDC

If a Vee drive prevents a visual of TDC there is a notch in the Accessory Drive that tells TDC too-

[Administrator]

I hope that forum members will appreciate the engineering complexities at work with Neil's device.

1. The size of the balloon at various inflated pressures/volumes. A weather balloon won't work.
2. The elasticity of the balloon. A stainless steel balloon won't work.
3. The influence of color. Beyond my bachelor's degree in engineering.
4. The influence of atmospheric pressure. Ditto.
5. The influence of oxygen permeability, as pointed out by Spike. Way beyond.

All this stuff makes my head hurt, but kudos once again to Neil.

Bill

[ndutton]

On your last two considerations:

4. There is zero atmospheric influence on the indicator short of being in a perfect vacuum. It reads only the pressure delta above ambient created by the moving piston in a closed cylinder.

5. Nitrogen permeability would be a 4X greater concern considering the chemical composition of air.

[Surcouf]

for durability we would probably need to develop a balloon resistance test to Marvel Mistery Oil vapors too!

[Al Schober]

Since the air in the balloon has come thru the carb, it just might be flammable. Gives me all sorts of thoughts...

[thatch]

Probably shouldn't go there

Al, Have you ever heard of an acetylene bomb?
Tom

[Dave Neptune]

Tom, my dad made acetylene balloons for parties. Only he knew which ones were which on the patio. Mom would get mad so he'd blow one up near her and the laughs would start.

I did some torch silver soldering for a while. we had coffee cans on the bench with water for keeping our "prods" clean of flux. If someone was bothering me I would fill a can upside-down and when they'd come back to annoy me I'd wave the torch past a hole. After the second time I moved the fluorescent lights a foot or so. Lots of can dents over my bench!

Dave Neptune

[thatch]

Dave, I was pretty sure that you would have played with them.
Tom