Curved motorcycle radiators like this Yamaha R1 model are very expensive to replicate. Manufacturing an aluminium motorcycle radiator from scratch is no mean feat in itself. I usually buy in the cores cut to size with end plates already welded.
The problem with this is that the actual core channels (the tubes where the water travels through to cool) are extremely thin material and takes considerable skill and specialist welding equipment to successfully complete.
When it comes to replicating curved motorcycle radiators in aluminium the failure rate of the cores can be over 30%. This is because the cores literally have to be curved by gentle rolling pressure in something like “pinch rolls”. This is typically a very “hit” and “miss” affair, often leading to core channels splitting during this shaping process.
The customers requirements with this radiator was to chop off the end cans and manufacture custom made larger end cans with a specific pressed pattern to match up with the pattern machined into the ends of his fork clamps .
So first things first, take some measurements, look at how this rad has been made. Its a factory standard item and hence has cast aluminium end cans (in this case) which have been “clamped” and “sealed” in place. The idea with this is to fabricate new end cans from 1.5mm thick aluminium sheet, I will for ease, re-use the fittings, filler neck and pressure cap. I will have to spin up a couple of threaded bosses to weld to the cans to pick up the third fan mounting point. These will be machined from 16mm diameter HE30 bar on my lovely Myford ML10 lathe, with an M6 thread through.
Here we go then no turning back now, 4.5 inch grinder with a 0.8mm thick cutting disk. Cuts through most general metals like butter. Shown above then is the first end can sliced off, revealing the ends of the core channels and the end plate. Now what I have done is cut the end can off approximately 10mm from the sealed flange. I have made the new back plate with a slot cut out to neatly slip over the small “stub” left. This means I can weld around the inside of the can back plate to the stub – as shown below.
So to weld all the way around the inside of this back plate to stub, I need to make sure that I cover the ends of the core channels as if my TIG welding arc “wanders” and catches the ends of these anywhere then potentially the material could be “blown away” by the wandering arc and leave me with a slight “pinhole” allowing water to leak out. To overcome this I covered the ends with a cut piece of steel.
Sp once each end can back plate was welded on, I will need to level this as the welding will distort it. This is a relatively simple job with a Planishing Hammer and a block of aluminium.
The rest of the panels to make up the end cans were cut to size and pressed up as required. The main outside face that needs “press marks” in needs to be set up and pressed to make the pattern in required. The first thing I need to do is to make up a pressing tool to achieve the desired result in the aluminium panel.
The best way I have of doing this and controlling the amount of pressure on the actual press tool is to use my hydraulic press. So firstly I cut up some heavy duty plate that I have in the workshop.
Above shows the first “test”piece that I set up using 10mm plate and small “slices” of steel and 3mm round diameter bar. Trial and error with this using some scrap aluminium gave me the definitive design and dimensions I needed. I then proceeded to make the “actual press tool”. The result is shown below.
The above 2 images show the tooling laid out and also in the hydraulic press with the aluminium panel in position.
The image above shows the first end can panel work positioned and tacked up to the back panel. Its important for a good weld that all these panels are tacked up in what we call an “Outside Corner joint”. Shown below.
Image taken from – http://www.twi-global.com/technical-knowledge/job-knowledge/fillet-welded-joints-a-review-of-the-practicalities-066/
Using an AC TIG welding plant with a Gold Tipped Lanthianated tungsten I was able to weld the panels together. When aluminium welding thin material it can be very difficult for the inexperienced welder to be able to see when to add filler material. This can be because the oxide layer will float on top of the weld pool and sometimes masks the molten weld pool. Other issues with welding aluminium that can be a problem to inexperienced welders is the fact that aluminium dissipates heat so quickly, this is different for mild steel for example in that the heat stays more local, whereas aluminium needs lots of heat input to achieve a weld pool as its a very good heat conductor. Even on thin material. Thin aluminium like this end can (1.5mm thick) leaves less window of opportunity between a weld pool being produced and the weld pool becoming so hot that it drops through and you end up with a molten blob on the bench.
So above we can see the first end can zipped up. Now the “new” material was easy to weld up, the not so easy bit was to weld the end can to the end of the original flange left on the rad. Issues around this are caused through contamination from the sealer and material coating the sits between the 2 material thicknesses on the original end plate. When trying to weld the new end can onto this, due to the heat input and the nature of the aluminium weld pool, contamination (sealer / paint / coating etc) gets dragged through the weld pool and bubbles up on top of the weld pool. If this is not “burnt” out properly we end up with pin holes in the weld, called “porosity” causing leaks through the weld material – not what we want.
Above you can see both end cans fully welded to the original core, with the pre-drilled holes ready for the pipe fittings to be fitted and welded in place. Why the cardboard? I needed to ensure that whilst cutting and sanding, laying the radiator over and on the bench and handling it that the cores were not damaged. Obviously as soon as it got hot enough the cardboard wanted to burn. During welding whilst it was being under the shielding gas it wouldn’t burn but, the minute the shielding gas stopped the cardboard would start to burn. This is because the shielding gas I was using was stops oxygen in the atmosphere from contaminating the weld pool. And hence also stops air getting to the red hot cardboard.
Pipe fittings welded in place complete with new mounting bosses to pick up on the third fan bracket.
Fans Mounted back on to check fit.
And after testing – pressure tested to 15 psi (just over 1 bar) and a bit of cleaning up, this was the end result. Hopefully it will look as good painted and on the bike?
Pictured below is the laser cut stone guard I drew up with the R1 logo in. This needed to be rolled to suit the radius of the core of the radiator and then bolted to 4 small welded bosses.
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