Kovea Spider Stove – Weight Reduction

[Brad B]

I’m a newer member here and also tweaking gear to suit my needs.   I’ve used the Kovea Spider for a past year and it’s been a great stove.  The stove is great for summer/winter use, wind screen use and baking, etc.   But the weight was always something I thought was a little high and wanted to trial a few things.

I picked up some Grade 4 1/8″ Titanium Rod and spend a few hours machining, bending and prototyping.  I liked the functionality, and versatility of the OEM stove so I didn’t want to loose this features or permanently modify.

Went from 172 grams to 121 grams, (30% weight reduction).   Still folds a fits in a MSR Titan Kettle.  And still will fit a various diameter of pots on the stand.

CHANGES:
– Removed Steel legs.  Replaced with custom Titanium, legs cold formed to approximately the same same.
– Removed legs stamped assembly, lock springs and bottom brass cap.  Replaced with a custom Aluminum bottom housing that supports the legs.  Legs are pinned in placed with roll pins so they still rotate for storage, but they do not detent into place.  Lower housing was Brass and was changed to Aluminum for weight and function.  Heat transfer is better but function and long term effect will need to be monitored.
– Removed control valve.  Identified that a older Fire Maple Valve was 7 grams lighter.  It was modded to fit.  Every gram counts.

PROS:
– 30% weight reduction

CONS:
– Legs are still stiff, but not quite the same as the steel legs.  They have the typically Titanium Springy-ness to them.   Still supports the pot fine but you just have to be aware.
– Legs do not lock in extended position, but they are reamed to fit the holes so they are ‘wiggle’ free.

NEXT STEPS:
– A slight additional weight reduction could be gained by customizing the legs for a particular pot sized being used.  You would loose pot versatility.
– Roll pins riding in grooves on the legs ends were used to hold the legs in place.  This has to be custom fit.  A change to snap rings or E-Clips would be easier but the leg rod grooves need to cut before bending of the legs.

Just some ideas and food for thought…… -b

[Jon Fong / Flat Cat Gear]

Cool idea, I wish Kovea would look into cutting the weight down.

The only concern that I would have is if the valve is compatible in the inverted mode (maybe Roger can chime in on this).  My understanding is that remote canister stoves that can be inverted have a fine pitch thread on the needle valve.  In the inverted mode (with liquid running through the line)  a fine pitch allows for better flow control.  I may be incorrect, but try it and see.

[Alex H]

Nice work, I have considered a Spider but for weight as well.

[Brad B]

Great question on the valves.   I thought similar things, but when I disassembled both valves, I found that they had similar numbers of turns from fully seated to open.  However, in this case the Fire Maple version had a 0.75 pitch thread and the Kovea had a 1.0 pitch valve needle thread.   They also had similar needle/hose profiles/sizes.  So if anything by the crude observation and numbers, the Fire Maple has a finer control but does not give as much volume in a full wide open position.   Further testing will tell, but I’ve have not typically ran the OEM valve and the Spider with the valve wide open.

[Roger Caffin]

Interesting experiment. My compliments!

While the pitch on the needle valve does affect the fineness of the control a bit, it is not really the dominant factor. What really matters is the profile on the tip of the needle. It would be nice to have a full 360 degree turn between off and full-on, but in practice I find I can regulate a stove quite happily with only 15 degrees effective travel. 45 degrees travel feels easy. 90 degrees even gets to feeling a bit slow!

As for peak flow rates – HA! You are valving liquid fuel when running inverted, and peak flow of a liquid fuel is a shade more than any sane person would want.

Go for it – and let us all know how well it works in the field.

Cheers

[Brad B]

Thanks Roger,

I’ve just started following your experiments in stoves and there is a lot of info to absorbed.  I’d like to proto something in the future.  You have quite a bit of trail/error and knowledge wrapped up there.

Interesting on the two control valves I looked at for this experiment.   The needle geometry profiles and tip diameters were within a couple thousands of each other and they both had about 1 3/8 turns closed to open.   I haven’t seen any issues yet but more field testing time is needed, and that’s the fun  part :-)

If you don’t mind me asking, have you found a good source for fuel line hose that you use for prototyping?  I was looking to make a custom section and it looked like most OEM stoves use 5mm or so.   I haven’t tracked down a good source, but I was looking at auto and./or the RC hobby side of things.  – Brad

[Roger Caffin]

Hi Brad

I think I make some detailed comments about the fuel line in the two series of articles. But to summarise: you have several choices:

• Race car fuel line: this is twice the diameter of what I use and very stiff and clumsy. The braid is tough and the hose material itself is also reliable. I think a number of stove mfrs have used it as it is commercially available. But it is like using 1/4″ steel stakes instead of the 1/8″ Ti wires.
• Cheap (Asian) substitute for race car fuel line: similar diameter and stiffness, but the rubber hose is prone to disintegrating after a quite short time. This stuff has been used commercially and the results discussed here at BPL. The stuff was a dangerous disaster.
• Lawn mower fuel line (no braid): this is compatible with butane and propane and comes in smaller diameter and is very flexible. However, it can not take the heat and when warm can not take the pressure. It can be reinforced with braid but it still deforms into the braid when it gets hot. It will eventually fail – with a fireball.
• MYOG fuel line, as I use.

To make my own fuel line I buy PFA hose in a size half what is used for the commercial race car fuel lines. This is far more flexible and is fully rated and spec’d. However, it is sold in 50 foot coils. And I buy custom-made stainless steel braid to suit – in a 50 metre spool. You cannot buy either in shorter lengths.

Cheers

 

[Stuart R]

You cannot buy either in shorter lengths.

True, but I wrote a polite email to a UK company to enquire about purchasing small quantities and they kindly sent me some free samples of PFA and PTFE tube in the requested diameter. Likewise for some stainless hypodermic tube for the vapouriser tube.

[Roger Caffin]

Gotta love those free samples!

Cheers

 

[Terry G]

Your bends look fantastic. How much weight did the ti legs save? I have thought about doing this, but the burner seems so heavy that I don’t know how much I wold appreciate the savings.

[Hikin’ Jim]

Brilliant work, Brad.  What kind of machine did you use to create the base in aluminum?  Something sophisticated, surely?  I mean this is really nice work.  Were I not already familiar with the stove, I might well have assumed that it came from the factory that way.

HJ

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