Thursday 17 July 2014

Ner-a-Car Update 6


The Ner-a-Car doesn't have anything so conventional as footpegs, it has sheet metal footboards.
Well, most of them do. Mine had only one, in a rather poor state; cracked almost in two, repaired with a strip of metal that had cracked in turn, and then welded. The only good thing to be said for the one I had was that it was a lot more useful than the one I didn't have. 

A chap from the Ner-a-Car list offered to sell me his spare pair, which was nice of him, but perhaps I should have checked more carefully. When they arrived they were, as described, in good solid condition, but were from the US model, and very different. 

Here we have my old one (at the bottom), and one of the new ones. 

It is very strange how the US and UK models are similar, while at the same time having almost no parts in common. 

It probably comes as no surprise to you that I then decided to try to make some. The first thing I did was to accurately measure all the hole positions using the Renishaw probe in my milling machine (another marvellous eBay bargain. A "Renshaw" probe reaches a much lower auction price than a "Renishaw" probe it seems :-)

You may see that I have cut off the weld holding the upright section on to gain access. I didn't like doing it, but it was only the second gash repair that was destroyed, not any original material. 
The footboard is actually held down by three rare-earth magnets left over from a scratch-built brushless motor project. 
Having got the hole positions as references I then modelled the footboard in 3D CAD, and got the CAD to convert it to a flat sheet metal pattern. 
I dithered a bit, and then decided to have the flat patterns laser cut. It isn't a lot more expensive than buying the metal sheet, because they buy full-size sheets and I can't handle them. I decided it would be sheer bravado to have all the mounting holes cut at the same time by the laser, but did it anyway. Await the hubris. 

I had previously realised that I could make a pair of double-sided press tools that could make left and right-handed versions of the footboards, and that all the blanks would be identical.  So all that remained was some machining. Actually a lot of machining, 2 full days and an evening of it. 

Here is one side of one part. The little holes match holes in the blanks, to keep everything aligned during pressing. The big holes were references to probe, the parts are about 50% longer than the travel of my mill, so I had to mill each side of each part in two bites. At least the probe makes re-setting easy. 

I tried to buy some rolled channel to convert my pipe-bending press (never actually used) into a conventional press, but the local company I asked never came back with a quote. So once I had the blanks I lost patience and decided to see if my bench vice could do the job. It seemed that it could. 

After squeezing the foot-pad shape in, the press tools are designed for the edges to be beaten up round with a hammer. The rear outer corner is quite a deep flange, and quite a tight bend, so heat was needed (in fact that area was more forged than panel-beaten. 

This picture shows the press-tools, some finished parts, and the old tired original:

And here is one of the boards fitted:

The holes all lined up adequately, much to my surprise :-)

It seemed pointless to make press tooling and only make two, so I made enough to satisfy worldwide demand for the next century.

Fuel Tank

The rear of the fuel tank is protected from road muck by the mudguard. I can only presume that the mudguard from my bike rusted away. Perhaps that is why I don't have one. (yet). 

The back of the tank has a large hole in it, and some other rust on the seams, and pinholes in various places:

I was originally planning to just patch the holes, but it looked like it would be hard to weld, and that the results would not be good, so I decided to make a whole new centre section. 

I first needed to find some 22-gauge steel, and I eventually found some in the back of my dad's workshop covered in red leatherette. It was actually the retired top-armour of our Technogames robot, Sprocket. (A thinly disguised variant on the Robotwars robot SMIDSY. )
So, a bit of work with the blowtorch had the soft-soldered ends and fittings off of the original tank:

I then wrapped the rolled ring tightly round the end-pieces, trimmed it to exact circumference, and welded the seam. 

The original seam was rolled, but I don't even know how that is done, so I cheated and used TIG.

The tank supports the full weight of the rider, as the seat sits on top of the filler cap (not ones to do anything in a conventional way, the Ner-a-Car boys). This means that the rolled rings are not purely decorative.  I don't have a swaging machine, and all the people on eBay with them seemed to want money in return. So I decided to improvise. I turned up two rollers on the CNC lathe, made a clevis, and used the milling machine in horizontal mode:

I had previously wondered what the 45rpm lowest speed range was for (other than possibly playing records) but for this job it came in very handy. In fact I had spindle over-ride at 10%, so the rolls were running 4.5rpm, slow enough to steer the marked line through the roll gap.
If you are wondering why the bottom roller axle is so long, it is my archetypical Yorkshire tight-fistedness, I didn't want to cut up a perfectly good length of silver-steel for a one-off job. 

And here is the finished ring with the end caps fitted:

I now need some Bakers Fluid (a product that looks to be in exactly the same packaging since 1921) or maybe some Fluxite (of which the same thing can be said).  And some tinmans' solder, none of which I currently own and the tank can be re-assembled and will hopefully hold fuel. 
I still need to source a petrol tap. I can see I might end up making one of those too, as it's a peculiar design. 

I made two hoops, not expecting the first one to turn out right. So if any other owners out there need a new tank-band, I might be willing to make you one too. 


  1. "The footboard is actually held down by three rare-earth magnets left over from a scratch-built brushless motor project."
    As you do…

  2. The problem with opening Blogger to write my own long overdue blog, is that I see yours...which doesn't help with my capitulation! :) A welcome distraction .. :)