Author Topic: By Jupiter  (Read 75273 times)

ChuckKey

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Re: By Jupiter
« Reply #420 on: July 19, 2019, 03:54:07 PM »
A split pin may be a cotter pin because it is used to retain a cotter? BTW, you also get 'split cotters': taper pins with a slit up the small end so they can be spread to ensure they stay put.

Offline Vixen

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Re: By Jupiter
« Reply #421 on: July 19, 2019, 04:03:37 PM »

 in 1943 the SAE standards (USA) called them cotter pins

Jo

Interesting. The little box definitely calls them cotter pins, a name we do not use in Britain, Given the date, 1944, could these pins have originated in the USA and supplied to us under the lease/lend arrangements?


You like potato and I like potahto
You like tomato and I like tomahto
Potato, potahto, tomato, tomahto
Let's call the whole thing off

Mike
« Last Edit: July 19, 2019, 04:11:25 PM by Vixen »
It is the journey that matters, not the destination

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Online steamer

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Re: By Jupiter
« Reply #422 on: July 19, 2019, 06:27:03 PM »
They are called cotter pins here.

Dave
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Online sco

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Re: By Jupiter
« Reply #423 on: July 19, 2019, 06:49:05 PM »
In the UK (for me at least) a cotter pin is a wedge type pin typically used to hold bicycle cranks on in the old days.

https://en.wikipedia.org/wiki/Cotter_(pin)

Simon.
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Re: By Jupiter
« Reply #424 on: July 19, 2019, 07:17:44 PM »
In the UK (for me at least) a cotter pin is a wedge type pin typically used to hold bicycle cranks on in the old days.

https://en.wikipedia.org/wiki/Cotter_(pin)

Simon.

Around here anyway, we call those just cotters

Cotter pins are the bendable wire things

Dave
"Mister M'Andrew, don't you think steam spoils romance at sea?"
Damned ijjit!

Offline Vixen

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Re: By Jupiter
« Reply #425 on: July 25, 2019, 07:13:13 PM »
Now that we have established that split pins and cotter pins are one and the same thing, we can get on with the Jupiter build and tick some more items off the seemingly endless 'still to do' list.

If the engine is to run, then I will need spark plugs and lots of them. The Jupiter has nine cylinders and there are two plugs per cylinder, that makes a minimum of 18 spark plugs. Some spare replacement plugs would be a good idea especially if the engine has a tendency to oil up the plugs before it has been fully bedded-in. An additional half set of nine would be a reasonable insurance policy. That now brings the required number of plugs to 27. An added complication was the non standard 5/16" x 32 TPI thread.

Even if I were to locate plugs with the correct thread, they would each cost something like £15 (Pound/Euro/ Dollar). I never bothered to multiply £15 x 27; I knew it would be unaffordable. So the decision to manufacture special spark plugs for the Jupiter was an easy decision. Besides it allowed me to make the new model plugs resemble the full size plugs and plug caps as closely as possible.

This is an illustration of a typical mica insulated aircraft spark plug from the 1920's. Note the two part screwed together construction and the double, side-on, spark gaps. Theoretically, these spark plugs could be dismantled for servicing and cleaning.




Here is an illustration of the spring loaded plug cap used on the Bristol Jupiter engines. Note, the ball terminal on the spark plug and the metal braided, screened ignition cables, intended to reduce radio interference.





Well that was the plan, so I started with sufficient 10mm Hex mild steel bar to produce a batch of 30 plug bodies, that's 18 for the engine, plus 9 replacements, plus 3 more incase of an unexpected failure during manufacture.
The hex bar was cut to size and the external features machined on my small EMCO Compact 5 CNC Lathe. The 5/16" X 32 TPI thread was cut in three incremental passes followed by two spring cuts. A die nut was then run down the threads to clean them up, before they were offered up to the cylinder heads.




The internal details were machined on my EMCO F1 CNC mill. The special 8mm x 32 TPI (I said it was a special) internal thread was thread milled in a single pass,using a single point cutter made from a broken tap. All the teeth of the tap, except one,  were ground away to make the single point thread mill cutter




The embryo plug bodies were then screwed upwards through a simple jig plate so that the two spark gap earth contacts could be formed by milling. The 3mm centre hole had be pre-drilled coaxial with the internal details of the plug body.




Al collection of thirty 5/16 " x 32 TPI spark plug bodies awaiting the next stage




The tubular sealing nuts were turned and parted off on the CNC lathe. The special 8mm x 32 TPI male thread was machined to be a perfect fit into the thread on the previously made plug body. A quick visit to the mill was required to machine the 8mm hex spanner flats.






I made a pair of storage blocks by coordinate drilling and tapping some 10 mm thick white perspex, in which to store and protect this growing collection of spark plug parts






In the next installment, from Vixen's den, I will describe the construction and manufacture of the central conductor and the all important insulators. Together with their assembly and testing

Stay tuned

MIke
It is the journey that matters, not the destination

Sometimes, it can be a long and winding road

Offline Jim Nic

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Re: By Jupiter
« Reply #426 on: July 25, 2019, 08:06:23 PM »
Stay tuned???  Wouldn't miss it for all the tea in China.
Jim
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Online Jasonb

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Re: By Jupiter
« Reply #427 on: July 25, 2019, 08:17:34 PM »
They are looking good Mike, maybe not the best time to say 8mm spark plugs can be had for about $5

Offline Vixen

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Re: By Jupiter
« Reply #428 on: July 25, 2019, 08:29:12 PM »
Hello Jason,

Ha ha, now he tells me.

However, the 5/16" x 32 TPI thread already existed in the cylinder heads. So, the 8 mm x 1mm pitch plugs are close, but not close enough; so no cigar.

Besides $5 x 27 is still a lot to take out of the kids inheritance. I made the lot for about £30 in materials, that's about £1 each.

Mike
« Last Edit: July 25, 2019, 10:10:10 PM by Vixen »
It is the journey that matters, not the destination

Sometimes, it can be a long and winding road

Offline Vixen

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Re: By Jupiter
« Reply #429 on: July 25, 2019, 08:55:33 PM »
Stay tuned???  Wouldn't miss it for all the tea in China.
Jim

Thanks Jim  :ThumbsUp: :ThumbsUp: :ThumbsUp:
It is the journey that matters, not the destination

Sometimes, it can be a long and winding road

Offline deltatango

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Re: By Jupiter
« Reply #430 on: July 25, 2019, 10:54:38 PM »
Definitely an inspiration!
My own attempts at making plugs for Mastiff had a 50% failure rate and I ended up buying plugs, but only four of them. The cost of as few as nine is enough to put me off any multi-cylinder engine. I'm following with a lot of interest.
David
Don't die wondering!

Offline Craig DeShong

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Re: By Jupiter
« Reply #431 on: July 25, 2019, 11:33:05 PM »
After making EVERYTHING ELSE on this engine I'm not surprised at all that you're taking on making the spark plugs also  :o

Following this build has been ...just ... fantastic.   :cartwheel:\\can't wait to see it run.

Craig
The destination motivates us toward excellence, the journey entertains us, and along the way we meet so many interesting people.

Offline Art K

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Re: By Jupiter
« Reply #432 on: July 26, 2019, 03:22:28 AM »
Mike,
I'm with Craig on this one. I like to say I pick my battles BUT 18 plus spark plugs would cause me to revisit that idea as well. Looks good.
Art
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Re: By Jupiter
« Reply #433 on: July 26, 2019, 03:45:19 AM »
Very Nice Mike!

Dave
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Damned ijjit!

Offline mike mott

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Re: By Jupiter
« Reply #434 on: July 26, 2019, 04:57:19 AM »
On my little buffalo marine engine I used Corian as the insulator, What are you planning on using Mike?

Mike
If you can imagine it you can build it

 

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