Optimus No 9

Today I managed to have a better look at the stove I bought at the weekend, on closer inspection it seems to be in pretty good shape considering it’s age, I can’t see any obvious visible fractures on the fuel tank, the nickel plating seems to be good and should clean up ok, the pump valve needs reconditioned with new seals etc.
Unfortunately the end cap is missing and I now know after some research finding a genuine replacement is next to impossible, so I will probably have a go at making a new one, the tools are also missing but I’ll cross that bridge when I get to it.
So I was wondering if anyone would be interested if I was to document my intended rebuild with photos as it progresses ?
Here are a few photos of its present condition being exactly how I received it.

 

Hello, yes please! Keep us updated on the progress, that would be a pleasure!

Nicola

 

Hi Nicola
Ok it will be a pleasure to do that, I’m starting to fully understand how lucky I am to have found such a rare and collectible stove and feeling rather guilty knowing how much i paid for it and the seller not have a clue what they were selling, but at the time I didn’t know what I was buying.
However I’m looking forward to reconditioning it, the end cap will be my biggest challenge, I think I’ll invest in a small sheet metal roller and have a go at making a new one myself, I love a challenge and fabrication is right up my street.
If anyone can tell me the exact length of a genuine end cap that would be very helpful, I can work out the thickness of the brass needed easily enough, but length not so.
Once I’ve made my cup of tea it will be added to my collection of other collectible bits and bobs and every now and then get used as it should be.
Joe

 

Very good Joe. Unfortunately I can’t help about the end cap size, let’s hope that some other owners of the Optimus 9 will jump in to share some measurements.

Nicola

 

Good evening @Car Boot Treasure Hunter . Congratulations on your lucky find.
I'll be eagerly watching this thread and wish you the best of luck in the work of getting this gem up and running.
Greetings
Stanisław

 

@Car Boot Treasure Hunter I would like to see your rebuild progress as well. I've got an Optimus 9 and can provide you with photos and measurements to help you along. Just let me know what you need.

Ben

 

I wouldn't worry too much, the seller didn't do their research and you didn't go out of your way to deceive them.

Rare stove. Nice stove. But I prefer the MG2! Got to love Nacton Blue.

 

Hi Ben
Thanks for the offer of help regarding photos and measurements, would you prefer to share the information on here ? or through private message ?
As the end cap in missing all dimensions are going to be very useful when it comes to fabricating a replacement, I’m not sure wether they are rolled from a flat sheet and brazed/soldered or indeed as I probably suspect they were formed from the process of metal spinning, I very much doubt they were pressed.
So a few close up photos of the inside should clarify how they are made, I’m hoping they are rolled because I then stand a chance of fabricating one myself, if they are formed from spinning then I would need to find a metal spinner to do the job for me.
Joe

 

@Car Boot Treasure Hunter
Congrats. Real treasure. I will await lucky solution of the problem.
Regards
Stanisław

 

Personally I would like stove details public, but, up to you all.

 

@Car Boot Treasure Hunter Here you go. All measurements are in inches.

First of all the cup fits very snugly onto the end of the stove so the inside diameter of the cup is the same as the outside diameter where it fits. It's a pain in the ass to get it on and off...it's that tight.

Here's a close up of the inside of the cup.


Here's the inside bottom of the cup.


The cup is 1.626 in. tall and the wall is .034 in. thick. There is a single hole in the cup that is .341 in. down from the lip. The hole is .069 in. in diameter or index drill size 53.


The cup has a rounded edge to it but I don't know the diameter.


The bottom of the cup has the Optimus logo etched into it.


Hope this helps.

Ben

 

It looks deep drawn rather than spun to me.

 

Thanks Ben you’re a star ⭐️
I think Blackdog is probably right in saying it was fabricated by the deep drawn process, something that is going to cause fabricating a new one quite a challenge, but as I’ve mentioned before I like a challenge and I have an idea already how I might be able to overcome this, also need to put the feelers out amongst friends for engravers.
Exciting times ahead, just one project to finish that I currently have on the go and I can then put some time and effort into the stove.

 

What an amazing find! well done i hope you enjoy your new stove. it go s to show they are still out there hiding.

 

So today I’ve managed to make a start on the No 9 and stripped it down for checking and fettling, getting the little pin out of the clam shell hinge pin was a bit of a tense moment, little bit of heat needed and small taps of the hammer, I do have a pin removal tool but it wouldn’t fit.
Fuel tank looks ok and I can’t see any visible damage apart from a couple of small chips where the plating has come off and various scratches here and there, but mainly scratched on the underside, clam shells have a couple of dents and it’s a bit squiffy around the latch, but I think with a bit of careful tapping with dollies I should be able to straighten it out ok.
The burner is still in one piece and I’ll tackle that once the rest is done.
If anyone can tell me wether the primer pump is the same as another model that would be very helpful as I need new seals and leather cup, I think I might of read somewhere in the forum the the Optimus 96 has the same size cup ?
So I’ll start cleaning it all up and fixing damage as i find it.
I’ll add some more photos as things progress.
Joe

 

I bet you breathed a sigh of relief on getting it all apart without damage! Measure the pump tube for leather cup size- the smaller type for the 96 etc are approx 14mm diameter, the larger sort are approx 18mm.

 

Thanks for sharing, I'm trying to improve the flame on a Borde.
Duane

 

@Blackdog yes it was a tense moment, the bottom bracket that the little pin goes through looks as though it is probably made of mazack and that’s about as strong as cheese, so great care was taken, but there is always a chance it will go tits up.
Spent a bit more time on the fuel tank and discovered quite a serious issue, I’ve tried to show it in the photos, I did notice originally that the clam shells never really closed that well and I’ve found the problem.
It seems the inner end of the tank has expanded out, now I’m not sure if this was caused by heavy handling or perhaps even a to higher pressure in the tank.
This is not a great design for a pressurised cylinder as it will always want to pop that end out when under pressure, I haven’t noticed as yet any kind of pressure release valve, in fact I don’t know what kind of pressure is attainable from the pump, anyway I have managed to fettle it back down where it should be, but it’s possible it will pop out again under pressure, or on the other hand if it was caused by heavy handling or perhaps someone dropped it etc etc I’ve now fixed it, we’ll have to wait and see what happens when it gets fired up.
Once I had sorted that out I managed to dig the filter out, a rolled up piece of of brass gauze, that made me chuckle, I then stuck the airline in it a blew all sorts of dust and crap out, next I gave the whole thing a polish up on the spindle trying to get the worst of the scratches out without going right through the chrome.
All in all I think the tank is in pretty good shape now.
Busy tomorrow so I’ll start on the clam shells next week.
Joe

 

Hi Joe, the roll of brass mesh may well be there to act more as an anti-surge device to prevent pulsing than purely as a filter, some stoves with piped connections between burner and tank are prone to this.

I'm not sure I agree with you about the design of the pressure vessel, it is pretty textbook in terms of shape. Hemispherical ends would be ideal but flat end caps are often used in many applications.

I think more of an issue is the gauge of brass used in construction- this issue you raise, plus the other major fault of stress cracking show that the abalance between light weight and durability was woefully wrong with the No.9.

It is interesting to ponder what would have happened if a world war had not occurred just as this desgin was being launched on the world. Would Optimus have withdrawn the stove from production, or would they have made the required changes as stoves began to fail in use? Thicker gauge tank material or a redesign of tank? Would the model ever have gained popularity, or was it just too radical, too unusual looking, too flimsy?

As the editor of 'The Motor Cycle' magazine pointed out several times through the later half of the 1930's: 'The public cry out for innovation, but buy the tried and tested model'.

 

@Blackdog thanks for the informative reply, yes I hadn’t thought about surge protection so I’m sure you are correct about it’s application.

I certainly agree about the gauge of brass used for construction as it is extremely thin and flimsy, so the damage was probably caused accidentally so hopefully now it’s fixed I will be able to get it to close properly.

I wonder how many tanks actually failed and split whilst in use, as this could easily end quite catastrophically with fire and injury, think I’ll make sure I fire it up outdoors.

I must admit I do love the design as it was certainly ahead of its time.
Is it published anywhere to give an idea of how many were manufactured and what the failure rate was.
Joe