This slotted cap bnr arrangement is something that has crossed my mind on more than one occasion. The prospect of drilling all those holes in a home made silent cap is seriously daunting to me. Given a suitable clamp or rest for the cap which would enable the radial spacing of the slots to be easily set, I think that a bog standard angle grinder might well be ok for the job; with a 0.8mm cutting disc fitted and set up in one of these;
I love grinders. The longer you have one the more ideas you get for using them. I started wanting one after watching a season of American Choppers. They use them for all kinds of things.
My intuitive setup would be for the angle grinder to be clamped static. Then have the cap mounted on a jig that can be slid back and forth towards it, and can be rotated in measurable increments. Yonadav
It's just one of those lousy burners off a British military MkII (revised) stoves. Not worth wasting money on. Gary (Bernie Dawg) did a biopsy on one in a CCS post somewhere, highlighting the fact that the burner specs are dreadful, so mightn't be the best candidate to experiment on unless you're willing to go to the lengths that Gary did to get it working. You'd also need to find a MkII tank, or fabricate an adaptor for another tank, to set it up too. Ok, I'll agree I'm not a fan of those ... No.2's John
Screwfix have 'em, |imgRemoved| and they're sweet to cut with - like using a knife - but you can break them just by thinking about it. The stand would be ideal for keeping them straight to avoid breakages.
Well I've learned something there, concerning those 0.8mm discs. Pays to seek further than just B&Q I suppose. John
I found that post by Gary. It's in the 'Frankies, Mods, and Hybrids' section, so comes with the obligatory warning not to fiddle and endanger life and limb in so doing ... Hot-rodding a MkII burner John
Yessir. Happy to oblige. The slots in the British Military #2 vehicle stove cap are 22mm long and range in width from 0.405mm (0.016") to 0.457mm (0.018"). I used a feeler gauge to measure them - they tend to narrow where they turn over the top of the cap. There are 40 of the slots in 20 "pairs". The pairs are angled slightly. The holes I drill in my BD caps are most always drilled with a #57 drill which is 1.0922mm (0.043"). I used the numbered drill set as feeler gauges (or go-no go gauges) on actual silent production caps from Optimus and Primus and found that was the size commonly used by these companies. I use #55 drills which are 1.3208mm (0.052") on minicaps and some of the specialty caps. I've not been able to drill holes larger than #54 (1.397mm or 0.055") without the caps suffering from underburn at simmer levels. There are other stoves that use slotted burners such as the Coleman Heat Plants and certain American suitcase stoves. After I finish coffee and breakfast, I'll pull one or two out and report the slot thicknesses on those. Cheers, Gary
OK. So the slits in this stove:https://classiccampstoves.com/posts/135433 are the same width as in the British Military #2. There's a bit more variation, but on average, the same. Also, I have a Montgomery Ward three burner cabin stove (in pieces in the "to fettle" pile) that has round burners with slits. Same measurements again. I wonder if this is a "standard" size dictated by physics like those silent cap holes? Cheers, Gary
Another twist may be an open top like the Prentiss-Waber(Preway) 401, 4521. These have a screen opening at the top of the burner assembly. Reminds me of the burner head on a lantern. Just enough barrier to keep fire on one side and air/fuel on the other. https://classiccampstoves.com/posts/102537 https://classiccampstoves.com/posts/116823 There would still need to be a few select holes in the sides to heat the burner assembly just to maintain proper vaporization. You could probably save a whole bunch of time and reduce drilling significantly. Six or eight well sized holes in the top, half dozen or so on the sides and slide a piece of stainless screen inside. If necessary jam the screen inside with a retaining ring. AR
0.45mm is a mighty skinny slot. I wonder if the originals were made from a disc of metal with wedges chopped out and then die-punched into the cap shape?
Interesting postulate. A big piece of flat stock with pie wedges cut out around the perimeter then dropped into a press?? That would work o.k. at the top and sides but how would it form back together at the bottom after being pressed? As a DIY cap you could sil-brave the bottom to maintain the shape. AR AR
I really like that Preway burner you have turned up there. Its better than the slot idea as long as you can keep the mesh in place.
How about horizontal slots in the side wall of the cap rather than vertical. Short alternating cuts. Positioned with every second one lined up (like bricks in a wall). These cuts should be fairly easy to make.
Dremel does a .023" thick diamond wheel which is skinny, but still larger than the slots Bernie has measured. http://www.dremel.com/en-us/AttachmentsAndAccessories/Pages/AttachmentsDetail.aspx?pid=545
I remembered I've a Lilor gassie with a slotted brass burner outer cap. It simmers well ... ... and goes well on full power It's about the same diameter as the outer cap of a 'No.5' type silent burner, but isn't so tall The slots are nicely machined, around 8mm in length and 0.5mm in width Curious, I picked that No.5 burner off the shelf and noticed the outer cap has a split personality. Is it an Optimus product? A Primus product maybe? Neither probably, more likely labelled as a Primus/Optimus pattern from another source Here's my post in the Stove Ref Gallery on the Lilor gassie Lilor John
Just for the record, in case it's of use to anybody... Hermes make thin grinder discs a well (I know they do 1mm, think they do 0.8mm as well but not sure now!). The 1mm jobbies are fairly strong, obviously weaker than a standard disc but don't fall apart at the slightest load. The Hermes discs are fantastic, their standard cutting and grinding discs last much longer than anything from machine mart or DIY shops. They are very good value too, at a fraction of the price of DIY shops before you account for the greater service life. Wish I'd discovered them earlier... the stack of worn out grinder discs in my garage is 2ft 4 inches high but grows more slowly these days. As to cutting slots in burner caps, a razor saw would be a successful but slow bet- 40tpi or more, 0.008" thick upwards, but anything harder than brass would blunt it quickly.
