Mc Donald Model tractor

Today I cast ,in aluminium ,the two rear axle supports for the tractor. These bolt onto the side of the gearbox and carry the split axles on two ball races on each side. The photo show the pattern, core box and the casings - one cleaned up and the other complete with runner.i have modified the gearbox pattern to avoid holes and will have a go at casting one of them next week.

Fred.

The weather conditions here have stopped casting for a while but there is still plenty to work to do in the workshop. The photograph shows a jig that I made up for silver soldering the rings inside the rear wheels. It was well worth the time and effort as I was able to use gravity to help the solder to flow as the wheel can be rotated when being soldered. By making the jig it gave the set up stability and didn’t fall over also I was able to do both sides in one heat.

They

Very neat.

A probably daft question on the castings with holes - have you ever tried patching small defects? Perhaps prepare the edges of the missing bits under a flux of some sort and then pour in some new molten metal? From what I can see you have formed all the important bits so just a question of stopping the oil falling out.

Good Day Adrian,

After all that effort I did consider blocking up the holes by either welding or liquid steel from a tube but decided there was only one way and that was to repeat the process with a modified pattern and core box. The fault was mine ( in the design) and not the actual casting process and all should be OK next time. As we cast outside and the weather was not good it was back in the workshop and I have now made up the rear wheel rims to the point of etch primer.

Fred

The weather last week allowed casting to take place in the open air foundry and this time there were no unwanted holes in the casting of the first half of the gearbox. The photo shows the casting in the milling machine having the faces cleaned up. The lugs on the side are for holding purposes only and will be later machined off. I hope to cast the second half next week.
Fred.

The weather last week allowed casting to take place in the open air foundry and this time there were no unwanted holes in the casting of the first half of the gearbox. The photo shows the casting in the milling machine having the faces cleaned up. The lugs on the side are for holding purposes only and will be later machined off. I hope to cast the second half next week.
Fred.

The photographs show the two parts of the gearbox casting bolted together and the set up for the boring of the ball race position for the differential shaft. The model suddenly seems to take on volume and has now become quite a big lump of material to man handle and set up on the mailing machine. Next step is to machine the gears that make up the differential and rear wheel drive. It will be a case of shut the shed door and concentrate on the job in hand.

I'm trying to imagine the gear setup here - presumably the two black marked bosses at the front are cross shafts for the actual gear change, then the blue one is an idler and the differential goes under one of the humps? If so what's the second, a transmission brake perhaps?

Good Day Adrian,

Thanks for your enquiry in relating to the arrangement of the gears on the Mc Donald. I have tried to follow the original tractor design as far as possible but my selector system is different. The part diagram shows some of the gear ststem. On the right is the large gear wheel (Mod2) that is attached to the rear wheel axle. There are two of these. The central gear is the differential and in the left hand side are the gears for 3 forward and one reverse. The shaft I on the far left carries the reverse idle gear. The gear box is connected to the engine by chain. The diagram to follow.

Ah, I see now. I'd assume differential between the axles but clearly not. Coming on well, keep at it.

The photographs show the process of cutting the gears. The large gears that drive the rear wheels are Mod 2 and the small gears in the differential are Mod 1.5. All gears are in mild steel and the blanks are mounted in a 4 jaw chuck on a square mandrill ( to prevent rotation in the jaws) that has been turned down to suit the centre of the gears. A pin that passes through the blank and into the mandrill is an extra safety factor to prevent any rotation. There are still many gears to cut and then assemble in the gearbox- just hope there are none of the half tooth variety!

Gear cutting continues with now 14 of the 19 gears cut and only 5 more to go. Cutting gears is an interesting operation but requires concentration and no interruptions! At least half of the time is used in setting up but the reward is the finished product. Having cut the gears they then have to set up in the gear case and have the selector mechanism added. More photographs next time.

Still following with interest Fred and enjoying the great work you are doing! a great idea to put a magnet to catch the swarf but I wondered why you changed the support at the "free" end of the mandrel?

Great work Fred,

Good Day Henry,

Thanks for your comments The reason I use I different support in some of the gear cutting is that my four chuck does not allow the Myford end support to be used. If I make the mandrel in the smaller 3 jaw chuck the support arm can then be fitted. The magnet also holds the splash plates in place and keeps the coolant in the work space. More gear cutting today.

Fred