Mc Donald Model tractor

The photograph shows the 18 gears that have been cut for the tractor gear box. They are either Module 1.5 orM 2.0 and are made from steel or bronze. The next task is to cut the key ways in the sliding gears and add the splines to the shaft. I had hoped to use 3 mm key steel for these and then cut 1/8” (3.2 mm) key way slots as this would give sufficient clearance for the gears to slide on the shaft but our local supplier only stock 1/8” so I will have to make some adjustments. The shafts will then be fitted into the gear case and the selector mechanism made.

Fred.

Amazing! Keep it coming!

Dom

The photograph show today’s effort as I made the splined input shaft for the sliding gears. The splines were made by cutting the grooves with a Woodruff key cutter as this gives clean sides and grooves of the correct width. The splines are made from 1/8”” key steel and are spaced at 120 degrees and are held in place by Loctite. A jig was made for cutting the internal grooves in the bronze gears/ bushes and a broach was pushed through. At present the fit of the gears on the shaft needs to be freed up as they have to slide freely on the shaft but that’s tomorrow’s job. Summer is here and the shed temperature today was 32 C but I can’t wait to get back in there tomorrow and press on with the project.

Fred.

What make is your mill? You seem to get very good results from it, having that many gears mesh properly must be satisfying.

Good Day Adrian,

The mill I use was purchased from an Australian company ( Hare and Forbes) a few years ago and is of Asian origin. It is both horizontal and vertical and I have now fitted a good quality DRO and find this a valuable asset. When cutting gears the dividing head needs to be very secure and it take just as much time to set up as to cut the gears.I used “ buttons” and a dial test indicator to set up the gears.

Fred.

Having now cut all the gears it is time to work on the selector system. There are two selector forks mounted in a 6 mm shaft with the gear handle at the rear of the tractor. Before making these parts in metal I decided to 3D print them to check there was sufficient room in the gearbox. The photo shows these parts in prototype stage - there will be some minor changes to be made before they are translated into metal.The gear shaft has a pin that locates in side the selector bodies and when the gear lever is moved forwards or back and the side to side to match the “H” gate at the rear of the tractor the appropriate gear should be engaged! An indent will hold the gears in place. The task for the next week is to have all of this system working

Fred.

p.s. Is there any one else out there building model I.C. Powered tractors?

Very impressive work on the gearbox

There seem to be very few people building land vehicles powered by self built engines. There are a lot of ETW Wallabies out there but very few 1831s. I have seen a number of Lanz Bulldog derivatives. I think someone makes casting sets.

I am working (very slowly) on a couple of models. One will be powered by a 12cc four stroke twin. I have almost got the engine running to my satisfaction with a constatnt depression carb. The simple carbs tended to struggle when a load was applied. This will be a freelance design.

The engine on it's test bed

The second one is based on the Field Marshall horizontal single cylinder two stroke diesel. I am slill learning/experimenting with the injection system. I have acheived some firing but not sustained running.

Hi Roger,

Your engines look very good and I am particularly interested in the single cylinder unit as I will know doubt encounter the same type of problems when I make the engine for this tractor. It’s a single cylinder two stroke “semi” diesel with hot bulb ignition and reed valve induction. Many problems to solve but that is what makes life interesting. Keep up the good work.

Fred.

Thank you This is my first go at a two stroke and bought a number of challenges. The prototype has angled ports, drawing these and the susequent maching was interesting. I strarted with an aluminium piece with the same dimensions as the cylinder but much shorter. This gave me a chance to see what was going on and reduced the amount of scrap. Using small long series milling cutters results in some deflection.

I cheated with the reed valves and bought a comercial set (spare part for a scooter, less than £2) which fitted in the space that I had.

I initially ran the engine as a spark ignition petrol engine to confirm that the red valves and ports actually worked.

Lots of fun

The last couple of weeks has been spent making the gearbox internals and now the white 3D printed parts have been replaced by metal items. I did change the selector mechanism as it was becoming over crowded at the front end. Working out all the movements of the selectors and mating them to both the gears and the “gate” at the rear was quite a fiddle. As designed the gears would not match the “gate” on the full sized tractor and that would never do!
Fred.

Hello Fred - How fares the McDonald project? Is the gearbox assembled yet?

they look great Tony, good fun!

Good Day fellow modellers,

Lovely to see your work and read your comments. I have spent the last two weeks tidying up my shed and as a result
tractor building has come to a halt but I am about to restart as I have now made some work space. The gearbox is now working and is ready for assembly but before I do that I have to cast and fit two small covers and the steering box. In the clearing up I did find a worm and worm wheel just the right size and right direction for the steering. The mudguards have been rolled to shape and material for the wheels spokes purchased. I am looking forward to making and fitting the rear wheels as this will then give an idea of the the size of the model.

Fred.

Thanks Fred, looking forward to seeing some more pictures in due course.

This week I have designed and made the patterns for the steering gearbox and also the two small side covers for the left hand side of the gearbox. The photo shows the complete 3D printed steering box in the top left, the four start worm and worm wheel and the other small patterns ready for casting.I have been using the metal from hard drive cases as these have been die cast and when melted down seem to flow well. The next stage will be machining up and then fitting the parts.

Yesterday they were patterns and today they are castings and tomorrow I hope to machine them up and fit them to the gearbox. These castings still need some cleaning up but appear to be ok. With the air temperature in the 30Cs and the furnace going full blast it was a hot job.

Fred.