Optimus 324 Rider ridden hard

I like the concept of this stove and it's well made, but with a couple of 'O'-rings in the quicklighter priming device and just a rubber 'pip' in the non-return valve (as opposed to Coleman's admirable check-valve and safety screw arrangement) there was no way that as its new custodian I was going to touch a match to it without first checking it wasn't going to leak fuel.

I suspected the packing in the control spindle was shot and ominously, no needle tip appeared when the valve was closed (jet cleaning position). The generator clamp was absent, so I'd have to make one of those and if I was being a purist, I should make a clip-on windshield too (original also absent).

So, a thorough strip-down session was in order, which would also enable me to get to understand the unconventional design better




"... ominously, no needle tip appeared" I said. Here's why - no needle




That fast screw on the spindle obviously matches up with female threads in the generator. Beautifully made




I discovered the stub of a cleaning needle in the spindle end. It wasn't threaded or silbrazed, so relied on an interference fit




Solution, a used Petromax lantern cleaning needle ...




... suitably machined and silbrazed in place - very delicately so's not to liquefy the spindle or any part of those lovely threads




The fast thread on the spindle ensures it's just a half-turn or so from valve fully open to closed




Cleaning needle tip now makes an appearance when it should




Now, a special mention of thanks to the first of two CCS stalwarts for their contribution to this repair project. First, Terry (Trojandog) for the excellent graphite sheet he sells to make up spindle packing.

I said at the start of this post that I suspected the packing was shot. Read 'absent' - but at least that washer was still in there




Terry's graphite sheet, a width cut to roll around the spindle and to compress in the packing nut ...




... like so, once the spindle nut has been tightened down to do the compressing. A perfect seal. Lovely stuff, Terry, thanks




Set aside, repaired now, for assembly some time soon




The second CCS member for a special mention is Stu (loco7stove). He kitted me out with those beautifully machined (in brass) non-return valve pip holders. That and a quality 'pip' will replace that abomination of a 'one-piece' device that we all despise when we come across the damned things in a non-return valve from a more modern era. It was rock-hard of course and wouldn't have done its job. Hopefully, if someone else had got hold of this stove they would have noticed the fuel pouring out of the pump tube on pressurising before they actually lit the stove




Thanks Stu!


The quicklighter pre-heater intrigued me ...




... not least because of this item of stove bling (the lever off it)




A couple of 'O'-rings in the quicklighter to check. One's this (just visible) in the nozzle. The generator pushes past it to make the seal. It checked out as in good shape. I guess Optimus used top-spec material to cope with the moderate heat at that end of the generator - well, it'll get no hotter than the spindle seals get in an MSR Firefly (which get hot)




The other seal on the quicklighter is the one that the nozzle turns on when the control lever is shifted from off to on




The outer jet orifice is fed by the air above the fuel level in the tank. The smaller, central jet hole is fed purely with fuel from the pick-up tube




TO BE CONTINUED


John

 

Now let me work this out

The pressurised fuel comes out of the central jet hole, pressurised air out of the larger hole ...




... here's looking inside the quicklighter nozzle




When the nozzle (operated by the 'Sweden' lever) is screwed down clockwise on the quicklighter body the conical tip of the quicklighter is driven into a close fit with the matching chamfer in the nozzle tip and although the pressurised air is shut off, there's an outlet for the fuel (hole in the end of the nozzle).

However, the control spindle at the other end of the generator - if shut - prevents the fuel flowing.

Pre-heat phase - 'Sweden' lever swung open, releasing air as well as fuel, but mixture can't reach burner until control spindle is twisted open. When it is, mixture is lit and the quicklighter does its stuff.

Generator is hot enough to end pre-heat - 'Sweden' lever swung to left to shut off air feed. Just fuel is injected into the generator tube to reach the control valve and gas tip.

Quicklighter-to-fuel tank lead sealing washer




Configuration of quicklighter, generator, control valve




Combustion chamber at burner is lacking the 'wicks' (2 X Part No. 5127) that don't act as a wick so much as a damper for fuel mixture surging (I reckon). I'm testing various loft insulation rock wool possibilities at the moment for flame resistance




Burner rose is a beauty - I seem to be referring to a number of parts of this stove in such endearing terms - I said I liked it but I've probably gone OTT




A component in the burner combustion chamber that Optimus refer to in their parts list for the stove as a 'restrictor' (Part No. 5215)




When I'm ready to fire the stove up I'll check on combustion with ...




... and without




... the 'restrictor'. It's not a stove that's meant to take alternative fuels, so it's not a component relevant to that context for use. Maybe Optimus made the burner combustion chamber inlet too large and created the restrictor as a design correction.

Whatever, here's how it mates up with the generator tip




Next job will be to make one of these clamps to hold the generator in place




TO BE CONTINUED

John

 

I have a 324 and I hate it! It's the one stove I could not put together right. Can't figure out how the graphite packing assembly was meant to work.

Yonadav

 

I suppose the quicklighter is similar to what is found on most kero pressure lanterns, except for the flip-valve and burner tube.
And here all these years I believed the 324 was just an oversimplified Coleman 502....

 

John,
That is an excellent write up. The detailed photos are wonderful. Thank you for sharing them.

 

Do you have the small 'washer' that goes inside before the graphite? .... Link AND Link .... That was missing on mine, and was, I suspect, why it leaked there.

Very nice post John.

Ken in NC

 

Great pics, explanations and presentation (as always), thanks.

 

Thanks for the kind words all.

Yonadav said,

Hopefully this diagram, crudely drawn though it is, will make the arrangement more understandable




Optimus's decision to incorporate a cleaning needle on the end of the control spindle and a fast-threaded screw on the spindle to minimise the number of rotations from open to close/clean determined the use of graphite packing 'outboard' of the spindle housing.

On the Optimus the compression loading of the graphite seal when the packing nut is tightened up is carried by the shoulder of the spindle housing (with the washer between the housing and the graphite of course).

John

 

Excellent work as always John , very nice job on the new pricker assembly 8) , now really looking forward to seeing the stove working

Best regards Stu

 

Last instalment, I'd still to make this bracket, or an equivalent




I decided to go for a more 'bling' alternative, in keeping with the 'Sweden' lever I've already enthused about.

Just after silbrazing a half-inch BSP nut onto some scrap brass strip and with a couple of brass rod offcuts pre-drilled with pilot holes it doesn't look so 'bling' here




Cleaned up and with the brass rod spacers brazed on it looks better




Here's how it mates up with the generator and control valve




I found some 'bling' screws in my oddments box - I think they came off an Audi speedo/tachometer assembly if I remember right - I needed two longer ones to fit the bracket and the shorter ones (cut down from longer lengths) will replace the stock screws holding on the burner mixing chamber to the stove tank superstructure




The bracket design lends itself to fixing the control valve key to it - probably a better arrangement than attached to the generator tube




Before I could fire up the stove I'd to make up some 'wick' to go in the burner mixing chamber. I relied on a couple of strips of heatproof fibreglass material cut from a soldering mat ...




... then folded up and bound with brass wire before installing




Fuelled up and ready to go








Works fine




Earlier in the topic I pondered on whether this 'restrictor' was better installed ...




... or removed




Turns out the stove performs better without it, from a very controllable simmer right through to maximum output




Tried it on a test bench brew first ...




... then out on a hike




Works great and it's very easy to fit in a pack.

John

 

Excellent handiwork and IMHO you were correct to make the missing bracket out of brass. The stove looks more balanced with the brass lever on the other side.
Keep up the good work.
Regards
John

 

I've discovered a significant weak link with this stove and it relates to the quicklighter




Although the stove's equipped with a jet cleaning needle that operates when the control valve is closed, the pressurised fuel to supply the burner jet emerges from this jet orifice in the quicklighter, which of course has no pricker wire arrangment




Although the enlarged photo makes that quicklighter jet orifice seem quite large, it's not. It's a very fine jet, less than a Primus 96's jet, so finer than 0.23mm and more like a jet on a small butane stove.

No problem in itself, but combined with a strainer gauze with a mesh that it's possible to feed a 0.23mm pricker through without too much difficulty, that's as bad as there being no filter in the fuel pickup at all




Inevitably, if a particle in the fuel that's smaller than the gauze mesh gauge finds its way into the fuel pickup tube then it will clog the quicklighter jet orifice and the stove won't work.

Straining the fuel helps, no doubt, but what a dumb design, to install a burner jet pricker capability and leave that obvious weak link in the set-up.

My example of the stove reeked of pump petrol when I bought it and the tank isn't thoroughly clear yet of a sediment of additives that had formed around the quicklighter inlet screw threads. Sure enough, the quicklighter has clogged once and I'd to dismantle the stove and blow through the jet with an airline, then have another go at getting the stove tank interior even closer to clinical cleanliness (impossible).

I'm not going to rely on the gauze and next chance I get I'll remove it and replace it with a Primus Omnifuel pump filter or something of the sort.

John

 

Great post John. Have looked for one of these for a while. Looks like you found the achilles tendon. This is saved to favorites just in case...

 

This & the 323 never had a good reputation. I think you've managed to make a silk purse out of a sows ear!

 

Saved this to my Favorites, too.
Thanks,
Ken

 

Cheers, John (Jeopardy) Rick, Ken and Ross.

I've resolved that problem with the quicklighter and have tested the new filter arrangement to my satisfaction with a succession of firings after jiggling the stove about (as it would be in a pack) to get any bits of dirt into suspension in the fuel and put the new filter through its paces. The stove lit first time and ran reliably throughout.

I got rid of the gauze, which made a pretty useless filter since as I'd said the gauge of the mesh is coarser than the size of the jet orifice in the quicklighter




I then machined out the cavity in the filter mount to create a better housing for the new filter ...




... which was a piece cut from the end of the fuel filter off this Chinese stove pump - rarely used and just happened to be handy. Something similar out of a bottle stove spares kit would have served equally well







Installed in the quicklighter pickup tube filter housing




Running well



John

 

Thanks John. Looks like a very good fix.

 

The filter modification is holding up fine. It ensures the quickligher is always ready to deliver a fine jet of pressurised fuel to the generator




Reliable at last!

Optimus 324 Rider ridden hard and hasn't collapsed yet | Classic Camp Stoves

John

 

Yes, I have it. Even with it in place, the spindle stem leaks fuel.

Having studied all of John's wonderful dissertation of how he managed to take a lemon and turn it into a beautiful stove (above and beyond the original designer's intentions), I came to a decision. Even after all of this heroic effort, I consider the 324 to be less safe than any Coleman or other pressurized white gas stove, with too many weak points that could become a "single point of failure". Thus, my 324 is hereby declared to remain an eternal shelf queen.

Yonadav

 

Nicely described fettle!
I will still have to dare starting up mine...

Br,
Anders