Bayonet Fuel cap

[Oyster 49]

I'm in for a couple.

[headdownarseup]

That shows quite nicely what i've been looking at H-A.

Plain and simple, but with no breather.
The problem will be in making a correct looking breather.
They look good though and for the price, a good place to start.

If you're going to make some i'll place an order for 5 (probably a few more in the future as well)

jon

[jerseydave69]

Does anyone have some photo's of the stripped down fuel cap ,that they can post!
I would like to try and remanufacture it ,if I can . If not I will get a price from an engineer ,so a few can be made .

Dave

[Adrian Dale]

When I get a chance Ill strip one down, and as Charles suggested, make a drawing . From the interest there could be a number required, at least 20 by this string alone. But lets not get ahead of ourselves. price will defiantly come in to this.

AJ

[THCL500J8]

Ok what price would you pay for a replica Bayonet fuel cap?

[Charles uk]

It's not just the air bleed valve that will be required, the fuel cap will need a spring a "cork" seal washer, the 2 pressed brass discs/washers that the air bleed valve fastens to, & the whole lot needs chrome plating & assembling.

In fact for the register I went to Candess in Wolverhampton looking for info on these fuel caps about 6 or 7 years ago, I was given a tour around their production facility by one of their Bigwigs with one of the chromed Marston caps in my hand after listening to him explaining how it didn't look like one of their caps until I showed him their stamping on the splash washer, though we did find 11 unfinished brass Q50 caps that I bought 10 of & was given one on the promise that I would return it to them when finished for their display cabinet.

The whole project died a death after I'd made a fixture to hold the pressing for drilling the air bleed vent hole, I then drilled & deburred the hole & had the cap outer polished & chrome plated, at this point I sat down & started on the costings,

10 caps, springs & cork washers @ £10.00 each £100
Chrome plating £55

The final figure was looking like they were going to cost in excess of £70 ignoring my time & petrol.

Taking £700 out of my bank in exchange for some shiny bits on my spares shelf, didn't seem wise when caps cost less than £35 on ebay & don't look like sequins on a turd!

[Hugz]

Hadn't realised we can drag photos in now....

Brass ones seem to be a tad rare

[Charles uk]

Thanks Hugo that paints a much clearer picture.

At Candess no traces of the press tooling could be found for the splash washers & it was the tooling & fixtures for these 2 components that caused demise of my plans, as the new caps were for Marstons & at those costs you would expect a perfect clone.

[Adrian Dale]

I did say it was a bit dodgy to think.... but I was not proposing to make the caps from scratch but to modify standard caps to be fitted with a vent valve. Obviously unless you went to China and ordered a million, the price for individual caps would be extraordinary high but to manufacture a couple of dozen vent valves suitable to be fitted into a standard bayonet cap may be practical.

AJ

[headdownarseup]

Modifying an existing design that is readily available was more my thinking as well.

Unless someone has a better idea, i think this might be a more sensible option for now...

(i'm not too worried about what it looks like on the inside, it's the outside that matters more)

jon

[jerseydave69]

Agreed ! A modification of the underside "gubbings" is a good idea , and by far an easier way of replicating the original design to as close as possible.
I'm sure by turning a male and female blank on a lathe , Then pressing a plate of brass between them would get the desired effect, then turning the centre part with a thread and thumb screw . The spring and washer should be the easy bit .
But bare in mind ,I haven't actually seen the build up of one of these caps in the flesh .

Dave

[Keith.P]

I have had one apart a long time ago, But I think the basic gist of it is something like this, sorry for the very basic picture, but I think you can work it out.
It maybe totally wrong, so say if it is.

[Charles uk]

This seems like a lot of work to make a new fuel cap look like something it isn't,
if you need a tempory cap why not use a flat topped one until the real thing turns up.

Every month there are one or two on Ebay.

No one will laugh if your SD has a screw cap fuel tank, because nobody really cares as it's not the least bit important.

[headdownarseup]

I would rather have something that looks right instead of fitting something that is completely wrong! (sd or otherwise)
Some of us go to great lengths in getting their motors looking spot on as for spec.
It would appear that some of these parts are becoming increasingly difficult to source nowadays. Most of these motors are going to be well over 70 years old now so it only stands to reason that after 70 years of use, an ever increasing amount of these motors are being literally thrown away with a valuable source of spare parts going the same way. To the scrap yard...

True, there are the odd one or two that pop up now and again, the trouble is they're usually attached to an engine that the seller seems to think is worth hundreds of pounds... and i cannot justify paying over the odds for yet another motor that has all the bits i need. I might as well just restore THAT motor and still end up having to wait for another fuel cap to turn up on it's own which leaves me in the same position as before? Stuck without a fuel cap...


From just this very brief discussion on this post alone, i think there is a big demand for these fuel caps. (and perhaps some of the tanks as well)

If i had a lathe i'd have a go at making a small run of these, but i havn't so i can't!
I'm sure Keith could get up a better drawing of these (he seems quite good at this these days )

Who's going to take the plunge i wonder?

Ever hopeful

jon

[Keith.P]

According to what I know (which ain't much) the fuel cap is a lot more technical than I first thought and a better picture is not going to help.
I myself have not seen any about for sale for a long time, So you have two options, a full reproduction, with a high price tag, or something not original that looks the part.
So you could have a standard fuel cap, drill out the top and screw or rivet on a one piece lookalike bleed screw, Maybe.
The only problem, whichever way you go, is that it will look and is brand new, so technically may look like a diamond on a turd.