Mc Donald Model tractor

Fred, I am looking forward to trying this process.

Lee

Great work Fred !!!

.

No this is not a repeat of a previous photo but the new casting set up and having the end of the bore faced off. The lower part of the crankcase has already been machined and has had the bearing plate and injector fitted (not shown in the photo.)The process is slow due to the fact that setting up an article of this shape and size just takes time. Drilling four holes took half an hour ( 25 minute setting up and 5 minute drilling). Due to the set up in the lathe the process of facing the end of the cylinder is slow and it takes 10 minutes for every pass, any faster and centrifugal forces come in to play with disastrous consequences! I hope by the end of the week to have the bore machined to the 50mm diameter ready for the cast iron liner. I will probably make a dummy aluminium liner that is a sliding fit so the I can mark out the ports before making the working liner in cast iron.The photographs that I have taken with the previous two efforts have been very useful for reference when setting up this casting for machining. Last weekend I went to the local car, truck and motorcycle show and took my 125cc OHC twin Benelli (1982) - a great day out.

Fred.

A “ model” motorcycle - makes a change from tractors!

Fred

The casting proved to be satisfactory and has been machined as can be seen in the photographs. This week I started the process of assembling some of the parts of the engine to make sure they all line up with where they are supposed to go and made a stand to hold the unit making life a little easier.The assembly includes the crankshaft /piston as I have now made a temporary liner which will later be used to check the port positions before making the real one from cast iron. The top photo shows the method used to machine the exhaust manifold - tricky but satisfying when finished. I have made the exhaust pipe a sliding fit and it will be held in place by a small grub screw as this will enable the pipe to be removed for ease of transportation and a reduction of volume should I every go the UK (MEX). I now have to make the fuel tank supports, fit the lubrication system ( the arms shown are 3D prints but will later be cast in aluminium) and add the water inlet and outlet holes. This tractor has a chain drive from engine to gearbox and is tensioned ( on the full size machine) by raising the front engine mount but as this is carried out the air and exhaust pipes are no longer vertical! I may tension the chain on the model by using a slipper tensioner but have to wait until the chain is fitted before I come to a decision. There are still problems to solve but life in the workshop is never dull.
Fred.

This weekends workshop time was spent on the injector set up ( but not the timing). These small parts take longer than expected to both make and then set up and there seems very little to show for the hours it has taken, but it’s all to do with the vision of the end product. Each division on the throttle “gate” is 5 degrees and equates to half a mm of movement on the injector plunger via all the levers. If this amount of movement is excessive there is provision for the leverage to be changed but experimenting will determine if that is required.The crankshaft has yet to have the flywheel keyway cut but as this keyway may also drive the eccentric for the injector I have held off the process.

Fred.

Still following with interest having spent several years playing with small fuel injection systems

Last night I watched a video of a slow running model hot bulb engine made in Holland (I think).It was beautifully made and ran like a Swiss watch. The builder had aimed for a slow running engine and certainty achieved that.The compression ratio was 8:1, a heavy flywheel was used and the injection was fairly early on in the compression stroke, all points that I am hoping to transfer to the Mc Donald. The photographs shows the advance/ retard mechanism with the two grub screws that are use to set the position of the eccentric that works the injector pump. When the final position has been made a keyway will be cut in the eccentric to give it a permanent position - the keyway has already been cut in the shaft. The oil tank has been set up and appears to work OK and the right hand side of crankshaft has been pressed together and scotch keyed in place.

Fred.

Your excellent work continues!

It won't be too long before you hear it running!

Howard

Today more 3D printing and casting. These are the saddle’s for the fuel tank and when cleaned up will be bolted to the top of the engine.

Fred

This week it was a case of one step back and two steps forward. On assembling the air intake I discovered that the air pipe was obstructing the water pipe on the header tank of the radiator. The cause of the problem was the casting that joins the air box to the back of the engine. I had made the casting on the centre line when actually a part of it was offset from the centre line - this can be seen with the two castings in front of the tractor. The one on the right was the first attempt and the one on the left shows the amount of offset require. This was not easily seen on the full size tractor and only another visit and more photographs resolved the problem. After making a new pattern and core box it took me 4 attempts to make the new casting with the cause of the problem being the placement of the in gate. As they say if at first you don’t succeed try ,try and try again! The fuel line and filter have been fitted and the holes in the bonnet cut. There are still plenty of small jobs to do and that includes machining the cast iron liner from a 60mm diameter bar - boring.

Fred.

You are making good progress!

Looks really good!

Howard

Boring, that was the order of the day - boring the cylinder liner that is. The bar of iron was 60mm diameter and had to reduced to 55 mm and bored out to 45mm diameter. Waste was high but that was the only material I had in stock. I still have to finish the bore, outside diameter and then machine the ports.The fuel tank is now in its final position and has now been fitted with a filler and cap. The bonnet has had the holes cut for the exhaust ,inlet and fuel filler and the support stays added. The fuel lines and lubrication pipes have also been added. The list of jobs that still require attention is now shorter but it’s all the small jobs that seem to consume vast quantities of time. Beware this hobby of model engineering is addictive!

Fred.

The list of jobs continues to reduce. This weeks work included the connecting up of all the water inlets and outlet pipes but the main effort went into machining and fitting the cast iron liner. Machining the bore was a long task as the final cuts were very small and lathe speed very slow ( about 20 minutes per pass )Having machined it to the required size both inside and out I was ready to press the liner into the cylinder. Guide lines were marked to line up the ports with the port holes in the liner. All went well with the fit being just right and in line with the top of the cylinder but a check revealed that the liner had rotated slightly as it went down the bore - oh bother! Next job was to make an extractor jig to remove the said liner. Double checks we’re made and this time all was well with all ports in the liner matching up with the ports in the casting. The piston complete with rings can now move up and down the cylinder. The next major job is working on the cylinder head. I also have to make and fit the rod that connects the clutch lever to the clutch and make and fit the chain drive to the gearbox. Photo to follow.

Fred.

..still following with interest and looking forward to the next instalment..

..that must be most of the main assemblies for the motor 'done' now?

..good stuff!

Absolutely brilliant and like DiogenesII I look forward to your postings on this EPIC project. It will be great to see the final build and the engine running, hopefully, at a slow tick over. What are you going to do after this build is finished? Another similar build or take a well earned break and reflect on this project's highs and lows and how problems were solved. I wish I had the skills and dedication to even contemplate undertaking something much less demanding.

Martin

Thanks for the comments Martin and Diogenes it’s good to receive feed back. I started this as log of the tractor construction to keep as a record for myself but it just grew and grew! It has been useful as there have been times when I have had to repeat a process and I have been able to check back in the log to see how I did a process or set up the first time round. I think it’s also good for other model engineers to see what is normally hidden on a model like this and perhaps get ideas or may be even inspiration. I remember my first visit to the MEX back in the early 1960s and how that inspired me and set a standard that some day I may achieve. A model such as this is a challenge and the problem solving stimulates the brain and at my age you need to keep that active! You asked what will be the next model and the answer is that I do have several model to finish. One is a 67cc V8 and the second is a working scale model of a 250cc. single cylinder racing motor cycle. I have the frame already made but at the time I had neither the ability or equipment to complete the model - like wise the V8 has already had the parts cast and partly machined and it about time it was finished. Also there is a 5” gauge Terrier class loco and a 3 1/2” gauge Tich that needs attention but as my interest in steam has diminished they will have to wait. I will just have to live longer or find a 28 hour days! The shed / workshop is a wonderful place to be and when I am in there any aches and pains just disappear. Having a hobby like this has given me new circle friends who share the trials and tribulations of the journey and the learning curve continues to grow. I have reached the stage with this model where it appears to be nearly finished but some of the small tasks and problems do take time to resolve. Structurally the end is in sight but then there is the interesting stage of experimentation with all the settings and hopefully it will go. There is no guarantee that “Go” will happen as there is no instruction book but it doesn’t stop one from trying. Perhaps at some time in the future I may bring the finished model to a MEX but that depends on many factors some beyond my control. If it does happen I look forward to meeting you all face to face. The photo shows the tractor at a local club day display last Saturday.

Fred.