For the curves where the Field Stand clips in I made a small ‘V Block’, cut from the corner of a piece of cast angle iron, and a piece of bar to press the shape using an upright hydraulic press. It can however also be done by hand.
Once you are happy with the shape make a second clip using the first as a pattern to get them the same. It is then a case of offering them up to the bracket on the frame and, using the Field Stand to align them, mark out the holes for the bolts and then drill the holes. Any fine adjustment of the bends in the clips and elongation of the mounting holes can then be carried out. Finally, without the stand clipped in, adjust the bend adjacent to the mounting point so that when the clips are bolted in place they touch each other (i.e. no gap between them) as this will ensure the stand is clamped in place tightly.
When you are happy with the clips it is time to harden them. So it is back to the heath and heating them up to the ‘critical temperature’ where a magnet will not stick to them. Wrap a length of steel wire through one of the mounting holes so you can easily lift it out of the hearth for quenching. Once you are up to heat, which will be a bright cherry red, you need to quickly fully immerse the clip in a container of oil. I use old engine oil as it is cheap and readily available. Once fully cooled down the clip will now be very hard and VERY brittle. If you run a round file across the edge it should just skate off and not dig in at all (see the video). Do not try to bend or manipulate the clip at this stage as it will break (see video!!).
To turn the hardened clip into a spring we now need to temper it. Tempering draws back the hardness so that the metal is still strong but has some give to it. The process involves slowly heating the clip evenly to a temperature of about 700 degrees F / 350C and then quenching it in water to ‘lock’ the temper at that point.
First you need to polish the clip to remove all the build up which occurred when it was hardened it. This is best done on a bench grinder fitted with a scotchbrite wheel but can be done by hand with scotchbrite or wet and dry. The surface needs to be clean and uniformly shiny.
I placed the spring on a piece of thin steel plate and initially heated the steel plate and then played the cool part of the propane flame over the clip (the cool part being the feathery part right at the end of the burning stream of gas). I had the gas turned down so the flame was no fierce. It is important to heat the clip up evenly and keep the flame moving, You will see the metal start to change colour, when this happens take the flame away and wait until the colour stabilises, then re-apply. This colour is a product of the oxide layer building up on the surface. As you get the surface hotter the oxide layer gets thicker and it absorbs the light waves falling on it differently, hence the change in colour. Tempering in daylight (but not direct sunlight) gives the best results.
The surface will initially turn a straw colour, then move through a darker browny colour to a purple then a dark blue and then a light grey blue. This grey blue is the temperature we are looking for which is about 700F/350C.. As each colour change is reached remove the heat and wait until it stabilises, any areas that do not change colour need a bit more heat, but remember a little heat can make a large change in temperature so just go gently. The video shows the whole process, so it is worth watching it to see the colours actually change in real time.
Once you have reached the light blue/grey stage put the clip into a bath of water which will ‘arrest’ the temper at the correct point. Once cooled, the clip will still have the oxide layer attached so you can compare it with the image above.
You should now have a clip with a strong spring to it. Try holding it in the vice and bending it with a pair of pliers, it should distort but spring back to its original shape.
It is then just a case of fitting both clips to the bike and trying them out. Mine were ‘very’ strong and needed a positive push on the field stand to locate, but they will definitely hold it in place. If they do fail (and I do not expect they will as I have given them both some ‘welly’ in the vice and they show no signs of fracturing) then they only cost £2 a pair and an afternoons pleasant tinkering.
Have a look at the video. A picture is worth a thousand words and my allocation for today is up.