Author Topic: Douglas 2 3/4hp (and 4 hp?) Petrol Taps and Amac Fittings  (Read 226 times)

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Offline pvn06

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Hi Folks, hope you and your families all well,

Douglas Type Petrol Taps (1185d)
Since My last post, I have been working on CNC programs for the distinctively styled petrol tap and filter unit fitted to many Douglas models from 1914-24 (Part No 1185d).  The starting point was a good quality 1/8 BSP brass (taper) lever cock tap with tank filter, which I obtain from one of my other manufacturer/suppliers.  These are very well made, but I then do a bit of work on them to give them a more correct shape - before polishing (ready for nickel plating).
But then, as per the accompanying photographs, you can see I have manufactured two additional components in stainless steel (which looks like nickel plating when polished) - to provide the distinctive filter unit.  The bottom union is lipped as per the original and fits to the top barrel piece with a red fibre washer imbetween and a small conical filter internally.  In truth, I do not think the small filter is required - as the tap itself has a nice fine copper gauze filter, but as that was the original intention - I have included one!  The bottom thread takes standard 1/4 BSP ferrule nut and ferrule (which I have also manufactured separately), for soldering onto 1/4" bore copper fuel pipe.

As always, they ended up taking much longer than expected (and cost a rather nice thru-coolant drill on the CNC. . . my mistake on feeds!), but think they have come out looking quite nice.  I did not have an original pattern to work from - but have looked closely at original photographs and pictures, so hopefully you will agree they look quite close to the original items.

I did these as I wanted one for my own Douglas 2 3/4 hp build, but have also made a small batch for sale on our Douglas section of our www.RacingNorton.co.uk online catalog.  However, the last job still to do is to confirm with my Plater, that he can nickel plate the brass taps (as they will need to be supplied assembled, to ensure tap tapers remain undisturbed).   I wanted to check with anyone interested who might be interested in one of these - do they prefer the main tap left in polished brass , before I send them away . . . I have to say, for myself I was intending to get the tap of my own nickel plated . . . but having polished the brass taps, I now think they look nice themselves on an old bike.  I will continue with the plated option - but if anyone does want a brass finish one, I will hold a couple back.

Amac Fittings:
And then, as part of making up the petrol pipe fittings for my project, as well as the tap I knew I needed to make up a period copper petrol pipe and a petrol pipe Union Nut to fit the base of the distinctive Amac floatchamber fitted at this period (Part No 1673d).  My own Douglas build has an original Amac being fitted (see my previous posting showing this), but I did not have the original floatchamber union nut for it.  Luckily I have a second spare Amac (for my other project bike) and this did have an original nut still fitted.  Surprisingly, its shape and thread was quite different to the standard BSP fittings found fitted to later Amal carbs - it being a larger hex, and a very fine thread, with a slight counterbore to the nut.  I was also surprised to find the taper at the bottom of the floatchamber was steeper than that fitted to most BSP - so ended up making a batch of those as well - in brass.
The nut is CNC'd in imperial hex stainless steel (linished before machining), and again look quite pretty.  In the last photo the two nuts on the right are the new ones, with the original nickel plated Amac nut on the right.

Final step for my own bike was to form the fuel pipe from annealed 1/4" external bore copper pipe (same pipe as the oil pipe fittings I recently did).  For this, I have tried to follow the general shape and form from original photographs.  when I list these fittings on the catalog - I will offer lengths of copper pipe slightly longer than the length I used . . . but does not seem much point pre-bending them, as every restored bike I have seen looks slightly different!

So that about covers it for this area - let me know if you are interested in a tap (before I send the small batch off for plating) - paul.norman@racingvincent.co.uk

Next parts I will probably make small batch's of are the exhaust valve lifter spring holder that screws into the crankcase (part no 543d), and maybe a couple of round headed engine bolts - the type that locate to the lugs with small pins, as there is no hex on the head.  I have to say though . . . I am pretty much having to do Douggie parts outside my normal hours now (and weekends) - as my daughter is shouting at me for the backlog of CNC Norton single parts!

Keep well all,
Paul
www.RacingVincent.co.uk and www.RacingNorton.co.uk
« Last Edit: 22 Nov 2020 at 17:10 by pvn06 »

Offline pvn06

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Re: Douglas 2 3/4hp (and 4 hp?) Petrol Taps and Amac Fittings
« Reply #1 on: 22 Nov 2020 at 19:18 »
Sorry, meant to publish one of the pictures of original taps I used as reference for these taps:

 

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