The bricks are “vermiculite insulation fire bricks” by Vitcas. From the blurb: A vermiculite refractory brick is built primarily to withstand high temperature, but will also usually have a low thermal conductivity for greater energy efficiency. To be honest, all I really used the bricks for was to put hot clamps down on. I held the rod in one hand and the large clamp in the other and played it around in front of the torch. Probably not the best technique, but I appear to be missing a third hand. I managed to get a ~1 inch circle of the piece red hot at any one time, doing the two tears in turn then the centre. I will have a think about how to make better use of the bricks but it is going to be a challenge to do so, heat from the outside and have reasonable access to the area. Would it be viable to pre-position a length of filler along each tear and heat from the other side until it melts? -R
Absolutely. If you are heating from the other side, you won't have the usual problem of the filler being blown away by the flame! The vermiculite bricks are ideal for this kind of work, good choice. As far as possible when trying to heat something larger, always aim to have the part in a flame-filled 'cave' of insulation. If you can possibly have the workpiece holding itself in position, surrounded by insulation, you'll then have one hand for the torch and one for the filler. Sadly, the world isn't always ideal though!
I took the plunge this morning. It went reasonably well - apart from the moment where I thought I’d joined a clamp to the case as I took things apart. A quick tap with another clamp sorted that. The results are below. Greater use of bricks with snippets of silverflo 38 pre-positioned: The pre-positioning worked a treat - all three flowed well. I was unable to get anything to do the same along the outer edge however and ended up scraping off great gobs of filler. After a quick clean: The rust hole I drilled out worked well - there is a good join at the top half above. It looks however like the lack of a third clamp in the middle left too large a gap, perhaps due to warping as the case was heated. Drilling another ‘feeder’ hole might have helped the lower half. Is this something to revisit with a lower temperature filler or maybe soft solder? -R
@IRM Looking great. The reinforcing plate, with rounded edges, really blends in well with the rest of the Optimus case shape, not jarring to the eye at all. You could always try heating the area with the gap back to brazing heat, and see if you can clamp the gap closed. Be sure to clean and reflux everywhere if you do this though. ....But understand completely if you want to leave it well alone now! In which case you could fill the gap with soft solder, which should take ok. It's trying to braze areas which were once soft soldered which is difficult or impossible! Regardless, it looks like you have put a lot of strength back into the case, without any nasty surprises! Fantastic work, hope you are plesaed with yourself, I'll enjoy seeing further progress.
Are there any reasons not to have another go? Is it going to be possible to get flux into the crack or is this more about a fillet along the outside? -R
@IRM Only a slight risk of further distortion, but not the repair piece is in place that's less likely. Just do the best you can to work flux in everywhere. It's best to assume that some other areas will melt and re-fuse too, so they should be fluxed in case this happens, to ensure no strength is lost.
I tried a re-run on the test piece I made on Saturday - sanded the area, cleaned, fluxed - pushing a little into the gap - clamped and re-heated with silverflo 55. The filler has joined at one corner and hasn’t flown into the gap. I suspect this is down to the surfaces inside the gap being too oxidised from the first run. How should I be approaching cleaning the gap on the real piece or is this more about forming a join along the outer edge? -R
@IRM Tricky, anything which will dissolve the oxides like phosphoric acid ('Jenolite' brand name, form example) May remain in there even after a thorough neutralising, and cause problems in the future. To me it looks like you have put a lot of strength back into the 'real thing', if you agree, it may be best just to flux up, plenty of heat, try and clamp up any further while heated, and whether successful or not, add some more filler along the outer edge to seal thing up. It looks smart and strong, this is really about refinements to certain areas if you deem it worthwhile. You've done really well, pitted areas are often troublesome to braze cleanly.
After a filing down the glob of filler, some gently persuasion with the hammer and a bit of sanding it looks a little better than yesterday. I think I will leave well enough alone, learn to use more clamps in future, and see how the paint stopper works out. Before I reach for the etch primer, any tips on surface preparation, or is just sand, sand, sand? -R
@IRM It looks just fine. On thin steel like this, it will never be an easy job to achieve perfection with the distortion which is inevitably involved. A good bet for surface preparation would be a rotary wire brush spun by an electric drill. The flat type are good for flat surfaces and outside corners, the cup type handy for inside corners. The stainless steel bristled versions are more expensive than the brass coated mild steel, but last longer before the bristles start flying off. If you go down this route, eye, ear, mouth and nose protection, plus sleeves and gloves for when the brush wears and bits start flying off. Sounds a lot of faff, but the bristles will work their way into the rust pits and clean things up properly, it all helps make the finished job last longer, if you want to invest more time and money. They are exceedingly useful things to have around the place for a million other jobs, just keep them away from soft metals like brass. Rotary wire brushes can polish the surface to an extent, making the surface less ideal for paint to adhere to. A sand afterwards with something like 800-grade wet & dry will provide a good key for primer. Then degrease thoroughly with naptha before paint. I hope you're enjoying yourself, I admire your willingness to dive in and aquire new experience!
Wire brushes… I had completely forgotten I have a box of those! That’s saved me a lot of tedious scrubbing and scraping… and turned up a few more pinholes. I’ll give it a sand tomorrow and get some primer on it. Thoroughly - it’s a welcome change from the day job. I am very grateful for all the guidance you (and others) have freely offered. I’d be fumbling and bodging along without it. -R
@IRM You're most welcome, it's great to see the progress. While I'm a 'rusty but running' fan, there was never a better 8r on which to do the full works! It's looking grand- nothing like a wire brush for digging out the pitting. Electrolysis works too of course, but a light wire brushing is still usually needed afterwards to deal with the flash rusting which occurs on drying out.
Is this the stuff? The safety data sheet has lots of mention about keeping away from sources of ignition, but I suspect that’s when ‘wet’. If not, this is not for use on a stove case… -R
@IRM That's the sort of thing. Both nitrocellulose and alkyd resins are used in automotive paints, so the paint stopper will be as suitable for a stove case as the car body paints which are commonly used. The warnings will be in relation to vapours when wet. The fact the composition of this stuff is more like a paint than a body filler is what makes it blend more seamlessly with paint layers.
I have given the case a few coats of Cosmos Blue, but am running into problems with paint sticking at touch points and flaking off when dry. Is suspending with a wire as shown the best way to approach this? Should I be doing one side at a time (drying before doing the other) rather the whole case in one go? -R
If you're struggling, try doing it in parts. Just sand back any areas you're not happy with and have another go, it should blend together well enough. What a difference!
I have painted and lacquered the case. This turned out to be trickier than the metalwork. More of a challenge than the simple RM320 or one piece Turm stoves I have done to date. Results are below. For convenience, before: And after Hopefully fixed up for another generation, but I’m not convinced the paint - ‘double acrylic’ and a petrol resistant lacquer will stand the test of time. I have used high temperature paint on other stoves which I feel a lot more confident in. What have other people used for cases like this? -R
Hi @IRM . I think you have reason to be happy. The juxtaposition of before and after photos, show a wonderful restoration. As for the durability of the paint, I would be tempted to bake it at about 180°C. I usually do, this several times. After each layer of paint and after varnishing. It should be taken into account that the paint tends to yellow after such an operation, so it is good to choose a color a tone darker, which after the whole process will be close to the desired color.
@IRM Fantastic finish, slight orange peel effct just like the factory paint job. The repair looks unobtrustive too. The difficulty with paints is that most available over the counter from high street/retail park outlets are far from ideal, legislation regarding VOC content and user safety mean most modern formulas are not great. ( Beware high temperature paint too- even if you could find a good match for an 8R, much 'high temp' paint is either not very good at resisting corrosion or abrasion, or requires baking at a higher temperature than most people will be able to achieve. Probably the ideal would be 2-pack epoxy primer for corrosion protection, then having a spray can of old-fashioned cellulose car body paint mixed up (expensive), folowed by a good quality fuel resistant laquer. But I reckon you'll get a lot of use out of what you've used, it should be easy enough to touch in any repairs. Remember the stuff applied at the factory certainly wasn't invincible! Brilliant first big metalwork/repaint job!
