Hi there, I have been reading this wonderful forum for quite some time now, but I need a bit of guidance... Beware of long story from complete novice/noob (But who just realised he loves working with metal, bikes and his hands)

So I had the idea to build a bike. I have been working on a drawing for the perfect Long Travel HardTail 29er for 3 years and after losing my job as architect decided this would be the time to build my own bike. :-)
At first I bought this tiny brazing set with cannisters of O2 and Propane/butane. Even built myself a racebike using some plain gauge tubing and Sif101. However, I fiddled so much with this frame that I decided it would be best scrapped and that my next attempt would be better.
So, I went to Bart Veuger from Windcycleworks for a morning's crash course using his Oxi/Ace setup and did a quite nice testbraze and got fairly confident I could go on myself. With his setup I could easily heat up a small spot on the tubes, apply some molten bronze and get out. Then moving the heat around the edges to thin the bronze and finally adding layers to create a nice fillet.
Yesterday I bought myself a oxi-propane setup (10l oxi, 5kg propane, Gloor handle with nr2 tip) Acetylene was way too expensive, and I read here that propane might be just as good, although requiring a slightly different technique. So now I am practising my ass off but I keep on running into the same issue.....
The initial heating of the tubes and spotheating the tubes to apply a dab of bronze works fine. (slightly slower than with OA, but not a lot). The thinning already gets a bit more tricky because I need to add quite a bit of heat to let the bronze flow around the tube. Here the tubes are getting redhot already. But in the end I do have a thin seam between the tubes, so it works.

However, when I then continue to make a small "dam" of bronze (while the piece is under 45 angle) I first need to apply a lot of heat to get the bronze on top of the thinned seam to flow. Tubes next to the bronze are now redhot and the bronze only just melts very locally. If I add more heat (to start to move the fillet around the tube) the bigger tube seems to reject the bronze, almost like a droplet of water on a leaf. The bronze sticks to the smaller tube but doesn't go everywhere to the other tube. I tried gravity, heat, pushing with the rod, but with no or little effect. Sometimes, when the tube is almost yellow hot, it runs a little, but then small holes don't close or it stops running a bit further.
I realise I need to practise a lot more, but I feel I am overlooking something here or using the wrong technique, and it's pissing me off. I tried different tubes, different pressures in both tanks, different flames and intensities, I degrease the tubes, sand them thoroughly inside and out and apply a thin even coat of Cycledesign flux.
Here is picture of my last failed attempt, which looks even worse since I tried to heat it way too much and bronze started dripping. But still not attaching to the damn tube! You can see the rounded edges of the bronze, this where it stopped flowing onto the tube. (like the water droplet)



TL:DR > How do get the bronze to flow nicely and attach to both tubes instead of getting rejected by parts of the tube. I would be so happy if someone could have some advice on this, I really want to continue building my bike. :-)