The two pictures show the boring process. A pilot hole, followed by my largest drill, which
was a blacksmith's type, 25mm in diameter and lastly boring out the remaining bit using a
boring head.I then fitted the boxes in their respective guides. There was some variation because the welding introduced slight warping in a few places. The boring had been straight forward, although I did come across some small pits which wont be a problem; they do say they hold the oil! However, there were some hard spots and these caused the boring tool to deflect, leaving high spots. So when fitting axles I had to scrape and hone these before the axle fitted properly. The axle material should have been 1-1/4" diameter but, unless I wanted to buy a 12 foot length I had to make do with what was in the suppliers' offcut bin, which was 30mm! The drawing gives two types of axle, one with and one without enlarged centre diameter. This meant the axle could have been 1-1/8" thick (the axle box bore) but there was none in the offcuts.
AXLES & WATER PUMPS
The material in the offcuts was EN1A which is a free cutting mild steel and gives a very nice finish for the bearing surface. An even better steel might have been the leaded EN1A (magenta) which gives a mirror finish, but they didn't have any at the time. A straight forward job which I completed quite quickly.
Some fitting was required with the axle boxes to make sure there was clearance between the box and the rear of a wheel and also to be sure the side tongues touched the frame both sides simultaneously. As can be seen in this picture, I have fitted eccentics. These are for the twin axle pumps. The water tanks cannot all be linked together as they are at different heights, so I decided to make the well tank feed via pumps and the side tanks with injectors. There is not a lot of space between axles to fit the pumps, so the eccentrics are a bit small giving a stroke of just half an inch. To make up for this, I've made the pump 5/8 diameter which theoretically will pump 2.8cc's each cycle. Hopefully this will be enough. The next mistake I made was to put the pump support too close to the rear axle and to overcome this I'll mount the pumps on the other side, thereby gaining 3/8" plus the thickness of the pump block. I wish I'd thought of this before, then I could have had bigger eccentrics and throw.
It's a pain but I have to stop and make the waterpumps now because once the wheels are on
and the engine is the right way up, I don't want to have to turn it over to get to the
underside.
I found some 3/4" thick walled, drawn, brass tubing which will do nicely for
the pump bodies although the bore is a little over 5/8" so I'll use 16mm stainless and an
'O' ring. The pictures show the hard soldering. Because of the thickness of the base, to
avoid the silver solder migrating up the tubes instead of down into the block, I've ringed
them with 'typex' and as can be seen the before and after shots show how well it works.
(sorry about the quality of pic 1, unfortunately I can't go back and repeat it.)The third
picture shows after pickling. Note the copper effect; I use citric acid for these small
jobs but if it gets contaminated with iron, then it plates with copper. I learnt this error
years ago when working with silver and ended up plating a complex casting! I used hot alum
solution in a copper dish then - very quick.
Goling up in diameter has provoked some discussion between friends; short stroke big diameter versus long stoke narrow diameter, and which introduces the most load against boiler pressure. One even suggested it might stall the engine! We shall see. I've no choice anyway.
The tubes, although thick walled were not thick enough to take a thread, so I sleeved them and fitted nuts. Afterwards, I thought I have always used notched rings rather than nuts as they are easier to do up in a tight spot. Too late now. As the distance between eccentrics and pumps is so close, I had some problems coming up with a design for the clevis and in the end settled for a mig welded fabrication. I've still got four clacks to make and pipe up.
It looks like the next stage will have to be the six wheels!