Camchain and tensioner seen up close in a cutaway bike engine

Home Repair And Restoration

A DIY Bullet Connector

Post Received 29 August 2020

By Mark Noel

Wiring loom connectors on most motorcycles are either of the spade or bullet type, presumably because they are cheap for manufacturers to fit. However, they are not foolproof, and if these parts had been used in Apollo 11 then it is unlikely that Neil Armstrong would ever have set foot on the Moon.

Anyway, as usual I digress! For reasons to be explained in a later article I need to break into the lighting circuit of my Honley 125 and found that the best way is for me to intercept a joint made by a pair of 3.5mm gauge bullet connectors. To insert my extra wiring would obviously need one bullet and one receptacle and the easy solution would have been to buy a pack of 100 units from a retailer on the interweb, leading to the waste of 99. But hey, one likes a challenge, doesn't one? Lets try to make one's own.

An exact replica of a 3.5mm OD bullet was turned up in brass on the lathe - easy! Not so easy is making the socket, which to be authentic must be is split and notched to grab and click over the bullet's groove, and yet be of thin enough wall to provide springyness.

The solution was as follows: take a piece of 4mm brass rod and bore out to 3.45mm for a length of about 20mm. A close-fitting aluminium mandrel was then glued into this tube with epoxy to provide support for the next stage of machining which involved cutting a narrow slot along the tube with a 1mm diameter ball mill. This slot was just deep enough to pierce the brass and enter the ally. A 2mm diameter end mill was then used to mill the flat that would become the solder tab.

A tiny rod of aluminium within a tiny sleeve of brass is being machined into shape

A hot air gun was next used to melt the epoxy and release the brass from the mandrel. The last 15mm of the machined tube was cut from the stock, and dressed with a file to nearly complete the socket. The bullet was inserted into this receptacle which was placed on a V block and a narrow bladed screwdriver tapped onto the slot to provide the required locking dimples.

The final result can be seen in the photograph. Ideally the connector parts should be gold or silver plated to ensure reliable conduction. Unfortunately at present I am out of gold, silver and rubies since I am awaiting another consignment of contraband from Ecuador.

In close up we see the intricate detail and the machining marks on the tiny brass connector

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Reader's Comments

Upt'North said :-
Nigel, if you were that desperate for a connector I'd have sent you one, or maybe even two free gratis. First class stamp as well.
03/09/2020 09:10:16 UTC
Ren - The Ed¹ said :-
It's not Nigel it's Mark. I suspect Mark was simply exercising his engineering muscles, keeping his eye in and much in the same way people climb mountains - "because he can". Also bear in mind Mark lives on that islet in the Irish Sea which at present is Covid free. He can't risk random packets from the plague infested mainland! Bolton's just been returned to a higher level of restrictions. FFS.

I am going to be lambasted for this... but I actually could afford to buy proper hand guards. Regrettably for my motorcycle though I get a strange, odd, peculiar satisfaction in building things like this for myself. I even get a weird sense of surreal pleasure when people gawk at my bodged creations. I suppose if I'm honest it's a kind of reverse snobbery. Do I have issues?

A gentleman such as yourself Upt' can't be going around handing out bullet connectors! Because if you send some to Mark then where will it end? I mean I could do with some for myself, oh and a new soldering iron if you have one begging?
03/09/2020 09:36:50 UTC
Upt'North said :-
So now I've got to send connectors to Nigel,Mark and Ed and then make an appointment at the surgery for memory loss, what was the first thing?
I'm fully aware that strange things happen on that windy Isle, I've done a few myself.
Now, did I put my pants on.
03/09/2020 09:57:39 UTC
Upt'North said :-
Yes you do.
Now what was the question?
03/09/2020 09:59:07 UTC
Ren - The Ed¹ said :-
Does anyone reading know if Covid impairs mental function? Asking for Upt'
03/09/2020 10:00:28 UTC
Upt'North said :-
Reminds me of a thread I recently encountered on the "other" forum about drain plug washers. It was obviously over 200 posts long, aren't they all, many stated they annealed(?) there old washers by heating and quenching them in magic potions so they could be reused.
Why in the name of the man above would you spend £1.00 fixing a £0.10 washer. But yes, it passes an afternoon and what else is there to do?
Now where are my under crackers, and is it OK to answer the door without them.
03/09/2020 10:07:01 UTC
Ren - The Ed¹ said :-
It's OK to answer the door without undergarment as long as you have overgarments on - aka "commando".

Where, prey tell, are you getting copper washers from of the correct size for 10p? It's one of them. 0900 you suddenly decide to service the bike. You drop the oil and rather than waiting 4 days for a pack of new washers or having to drive/bus/train to the local hardware store it's easier to stick the washer in the flame of the cooker then lob it back on the bike.

Anyhow even at 10p so long as you also heat up your soup while annealing the washer then that's 10p saved!
03/09/2020 11:34:16 UTC
Ian Soady said :-
Of course you don't need any special potion to anneal copper. Get it cherry red and then either let it cool naturally or quench in water. Both work but quenching cleans off any oil scale.

I always anneal new copper washers as they have often age hardened. It's amazing how much softer they get.

But of course the real answer is to use Dowty washers with a rubber / nitrile seal. Leaks stopped magically!

As to the other comments no idea what you're talking about, and where pray is this "other forum" so I can steer well clear?
03/09/2020 12:29:05 UTC
Upt'North said :-
Just checked, they worked out at 14.5p each including delivery. I love fleabay.
I apologise for all 4.5p of my inaccuracy.
03/09/2020 18:32:55 UTC
Mark Noel said :-
Hi Upt'North,

I have checked my birth certificate and I was indeed christened 'Mark', although my parents tell me that they seriously considered 'Nigel' for the screaming brat that had recently been spawned.

It's a nice name but for the time being I'll settle for 'Mark' and don't ask what nickname I was given at school.

Wot was yours?
03/09/2020 18:45:22 UTC
Upt'North said :-
There's nothing wrong with an apostles name. Was it Mark The Evangelist?
I've only ever had two nicknames, none really stuck, one was Toby and the other is Big Lad, although I'm not bragging, it's just a fact.
Big Lad still gets used by some.
So, go on, prey tell?
03/09/2020 18:55:44 UTC
Ren - The Ed¹ said :-
They called Upt' Big Lad for the same reason Little John was called Little John.

With an unusual name like Ren there was no reason for me to require a nickname as I've never met anyone else called Ren. Most of the other names I've been called were, well, unpleasant I'd say. Sharon's pet name for me is often "d***head", I'm sure it's a term of endearment but she says it with such vim and vigour.
04/09/2020 08:26:36 UTC
Mark Noel said :-
OK, I own up.

At school it was 'Fuzzy', while at home she calls me 'Silly Old Man', undoubtedly with great affection I am sure. Thankfully the dog cannot speak else there would be more profanities.

Mark a.k.a. Nigel
04/09/2020 10:05:18 UTC
Borsuk said :-

You don't make your own tooth picks by cutting down 200 year old trees and turning each one down to 2mm by any chance?
05/09/2020 00:25:34 UTC
Ren - The Ed¹ said :-
That's why he's banned from America Borsuk. He cut down a Giant Redwood and spent 4 years whittling it down with a blunt penknife because he'd got a piece of jerky stuck in his teeth.

Thanks Borsuk, that was another cup of tea over the keyboard. That made me laugh.
05/09/2020 10:59:35 UTC
Borsuk said :-
My job here is done then Ren.
05/09/2020 23:33:00 UTC
nab301 said :-
All my Japanese bikes and my Bimmer use alloy washers , can they be annealed.. or is there any metallurgical reason I shouldn't use copper washers? I have used dowty washers in the past on my Enfield but they don't seem right on modern bikes!
Did someone mention free stuff...
The other Nigel
06/09/2020 18:07:57 UTC
Ian Soady said :-
You can anneal aluminium alloys but it's harder to do than copper as there is no visual clue. Allegedly if you smear the metal with soap and heat till it goes black that's the right temperature but you're more likely to end up with a puddle.

No reason why you can't use copper instead provided it's dimensionally correct. Or Dowties for that matter.
07/09/2020 10:22:12 UTC

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