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Mc Donald Model tractor

Single cylinder semi diesel

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lee webster30/06/2022 08:39:29
116 forum posts
10 photos

Fred, I am looking forward to trying this process.

Lee

PatJ30/06/2022 08:54:10
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502 forum posts
769 photos

Great work Fred !!!

.

Four stroke Fred11/07/2022 10:09:37
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291 forum posts
284 photos

1b50a9c6-76d3-46cc-8764-daa92b644958.jpegNo 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.


Four stroke Fred11/07/2022 10:27:13
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291 forum posts
284 photos

d2086397-a6e7-4e0b-bb0b-3e83bde96bf1.jpeg1368084b-7e6e-41b5-8446-135a2b22be8f.jpegA “ model” motorcycle - makes a change from tractors!

Fred

Four stroke Fred19/07/2022 07:32:34
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291 forum posts
284 photos

d0a7d505-140e-4e09-981f-f0b499932266.jpeg64d5cbe7-ccd7-4d90-8bdb-19329083ba71.jpeg80eba4d3-f323-4f5d-bad8-4925a246a1d2.jpegThe 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.

Four stroke Fred25/07/2022 09:10:38
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291 forum posts
284 photos

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.

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Four stroke Fred25/07/2022 09:11:15
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291 forum posts
284 photos

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Roger B25/07/2022 09:42:11
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192 forum posts
82 photos

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

Four stroke Fred29/07/2022 08:50:56
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291 forum posts
284 photos

2890d5e0-5deb-49e9-a5af-3eba074d6cbd.jpegLast 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.

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Howard Lewis29/07/2022 17:16:04
6314 forum posts
15 photos

Your excellent work continues!

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

Howard

Four stroke Fred31/07/2022 05:37:18
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291 forum posts
284 photos

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.

Fredd393f4ab-1d41-4180-987c-f4670c82885a.jpeg

Four stroke Fred11/08/2022 03:50:09
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291 forum posts
284 photos

b29d5fd8-d92b-43ca-ba18-cc02077eddff.jpegThis 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.

Howard Lewis11/08/2022 07:49:58
6314 forum posts
15 photos

You are making good progress!

Looks really good!

Howard

Four stroke Fred14/08/2022 09:43:25
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291 forum posts
284 photos

67889d81-a9b4-4743-aea4-8c38e6ef18cd.jpeg541b9fe9-ccee-4411-bb00-fef901766cee.jpegBoring, 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.

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