All Alloy Cup progress

[wild_willy]

Technical Query 

I am beginning the wiring on the Cup.
Although I have a later coil engine my chassis
No is fairly low 10xxx and would like to use the
Earlier Magneto switch panel.

It has an IGN post on the back of the panel
which I THINK in the OFF position actually “grounds”
The relevant part of the Magneto. Can someone confirm this point?

Should I therefore take a live feed from somewhere else and separately 
Switch the Power to the low tension of the coil?
This would make the OFF position of the switch redundant?

Also see the photo of my Cut Out which has two posts
To connect to D and A posts of the switch panel.
From looking at my photo, which post is A and which is D?

Also does anyone sell the flate plate fuses fitted
To the other posts within the cut out?

I’ve been granted permission to have my soldering iron
In the spare room as the garage is now too cold!

Merry Christmas to all the folks on the Forum

Bill G

Aka AllAlloyCup

Try here:
https://www.autoelectricsupplies.co.uk/p...tegory/245

[Tony Press]

Technical Query 

Also does anyone sell the flate plate fuses fitted
To the other posts within the cut out?

Bill G

Aka AllAlloyCup

Try here:
https://www.autoelectricsupplies.co.uk/p...tegory/245

Looks good but- too big in both ways- the Lucas posts are 1 inch apart (these are 1 1/2" between posts ) and the smallest rating is 30 amp- don't we need 15 amp fuses ?

[AllAlloyCup]

My physics should be better really but
If you had a rectangular flat fuse rated at 30 amp
And you cut it in half, along its length would that then give you a
2 x 15 amp fuses?

Presumably any fuse wire needs to be rated at 6v?
As it’s the power = V x A that would determine the energy
needed to melt the fuse material.

Someone smarter than me will know?

Regards

Bill G

[AustinWood]

I think it's the current and resistance that rates it. I^2 x R is the formula.

[Steve Jones]

Yes, the voltage isn't relevant. If it was, your domestic fuse wire for 240v would be 1/4" diameter.

Steve

[jansens]

Fuse wire doesn't have a voltage rating. Glass fuses do but that's there to indicate what voltage a BLOWN fuse will with stand without arcing over.

If it's not seen I would just solder some solid core copper wire to the legs of a standard automotive blade fuse of the right amperage from a modern car and wrap the wires around the posts.

Simon

[AllAlloyCup]

Thanks Simon

That’s a good plan as the posts are enclosed
Under a metal cover.

Regards

Bill G

[Tony Press]

My physics should be better really but
If you had a rectangular flat fuse rated at 30 amp
And you cut it in half, along its length would that then give you a
2 x 15 amp fuses?

Presumably any fuse wire needs to be rated at 6v?
As it’s the power = V x A that would determine the energy
needed to melt the fuse material.

Someone smarter than me will know?

Regards

Bill G

No - see the discussion (s) in earlier forum posts.

[jansens]

I'd wrap the wire around the pins a few times before soldering to give a good mechanical connection then just flow a bit of solder over to make it all tight.

Simon

[andrew34ruby]

My physics should be better really but
If you had a rectangular flat fuse rated at 30 amp
And you cut it in half, along its length would that then give you a
2 x 15 amp fuses?

Presumably any fuse wire needs to be rated at 6v?
As it’s the power = V x A that would determine the energy
needed to melt the fuse material.

Someone smarter than me will know?

Regards

Bill G

Bill, the power V x A is the total power that creates heat or magnetism anywhere in the circuit. Most of this is at the headlight/horn/motor and not at the fuse. To calculate the heat produced at the fuse you use the formula    Amps squared x resistance in ohms. So voltage doesn't come into it.
And yes, slicing your 30 amp fuse would make two 15 amp fuses. You would be doubling the resistance, but also halving the power required to 'blow' the fuse.

Hope I got this right! I was very good at O level physics, but that was 48 years ago.