Poor quality condensers

[Dean]

2 weeks to find a faulty condenser........... geeeezzzzzzzzz - it should take 2 minutes!

It would take me weeks.... because I don't have one. Even if I empty out all my old bits and bobs, I'd struggle to find a faulty condenser.

[bmcecosse]

Oh everyone should have a faulty condenser in their spares bag........

[katy]

2 weeks to find a faulty condenser........... geeeezzzzzzzzz - it should take 2 minutes!

I'll second that!!

[dp]

A condenser is just a capacitor isn't it? In which case does anyone know the properties of the minor condensor? It's probably possible to get an equivalent for pence at Maplins or RS.

Further, I wonder how precise the condensor has to be since, with old motorbikes there's a trick of adding a big capacitor to get a better spark and a bike that'll kick start on a flat battery.

[bmcecosse]

Which is exactly what a radio suppressor does - added on the outside of the dizzy as a get-home measure. I think std is ~ 0.2 uf

[katy]

The BMC manual lists the value at .2mf (.2uf), what it doesn't list is the voltage requirement which is probably up in the hundreds if not thousands of volts, which is due to the "kick" from the colapsing field of the coil.

[Alec]

Hello Katy,

no, I think you are over estimating the effect, if there is any rise in voltage on the l.t. side it is minimal and very short duration. It is not measurable with a voltmeter anyway?

Alec

[Dryad]

Hello Katy,

no, I think you are over estimating the effect, if there is any rise in voltage on the l.t. side it is minimal and very short duration. It is not measurable with a voltmeter anyway?

Alec

You would see it on an oscilloscope - probably up to a couple of hundred volts. Enough to give you a shock, and it would seem enough to break down the insulation inside the condenser. The one that failed on my car still measured 0.2uF on my capacitor meter but was shorting out under load.

[katy]

I don't know what voltage is produced but I know that it's a pretty good one as that's what they used to use for the spark to fire the fuel mixture in the old "hit and miss" engines.

[dp]

I don't know what voltage is produced but I know that it's a pretty good one as that's what they used to use for the spark to fire the fuel mixture in the old "hit and miss" engines.

What's a "hit & miss" engine?

[daveyl]

Coinsidentally, a chap knocked my door this evening asking advise on his mis-behaving Moggy (starts and runs but breaks down after half an hour). He'd only recently had it serviced. I suggested the condensor might be at fault. As you say, maybe dodgy batch.

DP, Can I ask what wheels/axle you're using on your motor? And how did you fit the wheel caps?

[bmcecosse]

'Hit and Miss' - usually in a far corner (thankfully) at shows - dazed looking people sitting around a single cylinder engine attached to a largish flywheel and going 'chuff chuff chuff bang chuff chuff chuff bang' - over and over again. Search me where the fun is!

[katy]

http://en.wikipedia.org/wiki/Hit-and-miss_engine