Single cylinder air blast injection diesel engine

[weir-smith]

The building of any form of model diesel is no mean feat for anyone. However, I have started on a new project to build a 1:6 scale of the DM 104 single cylinder diesel. It is a vertical engine with an auxiliary compressor running off the main shaft. See attached photograph taken in the Danish diesel museum. I have also included a photograph of a similar but smaller engine located in Munich. I have located about 12 of these engines still in running condition, so there are not many of them.

I have spent the last two years building a experimental diesel with a 40mm bore to experience the problems of building such an engine. The lessons gained so far is more of what not to do and upping the accuracy required. So far, I have made 11 injectors and several fuel pumps all with varying degrees of success. However, I now have what I believe is a working injector. Obtaining sufficient compression was another problem now over come.

In respect to the new engine, I have all but completed the flywheel (see photos taken a a friends workshop where I used his large lathe) and I am well on the way to putting the drawings into CAD. My intention with this build, is to construct it to the highest standard within my capabilities. There are considerable problems with building this engine and using air-blast injection. The main one is the compressor which has to work at 800 psi as well as requiring intercoolers. The problem with diesels is that you can't scale the physics and therefore you need to make the components to withstand those conditions. I have now collected a considerable amount of information and drawings of this engine. If anyone has an interest in the progress etc I am happy to provide updates.


Bruce W-S

 

[gunna]

Will be following with interest, Bruce. I don't know what details you may have been able to locate, but here are the internals of a full size air-blast injector for info.
Ian.

 

[weir-smith]

Ian

Thanks for the photos. Everything helps with the understanding. I have a question, where did the injector come from. To my knowledge, there is only one similar engine in Aust. which originally came from a brewery in Victoria.

I have also tracked down a copy of a book called "Diesel Engines for land and Marine Work" by Chalkey and published in 1916. The book covers these engines in great detail.

I did have the opportunity to have a good look at one partly stripped down for maintenance while in Denmark. Ended up taking several hundred photos of the two engines. They also had a working example of a double acting diesel of some 22,000 HP which they generously cranked up for me. Some engine!

To my knowledge, there hasn't been a successfully built air blast model diesel. A Dutch fellow had a good try and built a successful model however, he had to revert to use solid injection to get it going. As I understand, his compressor failed and I think that was because he didn't use inter-coolers. However still a fine model he can be proud of.

Bruce W-S

Perth WA

 

[weir-smith]

Hi Ian

I didn't appreciate that you were restoring the real thing. I saw the photos that you posted showing the rebuild so I am a little jealous.

In all of the information, books and photos etc that I have, I have been unable to determine the gear ratio between the crankshaft and the counter shaft. I appreciate that overall the gear ratio between the crankshaft and the camshaft must be 2:1. The question is, is the crankshaft to the counter shaft 1:1 and the counter shaft to the camshaft 2:1 or is it the other way around?

On all of the engines that I have seen, it has been impossible to determine the crankshaft ratio. The gear on the crankshaft appears to be cut into the shaft which would allow for the minimum distance between the centres.

I now have the majority of the required material including all of the valves, bearings, rings and cast-iron for the head and cylinder. The drawings are also about 50% complete. I had the flywheel flame cut out of 30mm plate and now the weight is around 8 kg. The engine will have a bore of 47mm by 80mm stroke. The head will incorporate the two main valves plus the air-blast injector and a compressed air start valve. The head will also be made in two halves to allow for machining the cooling water passages and the fitting of the valve cages.

thanks

Bruce

 

[gunna]

You were right Bruce, this is the 3 cylinder Willans from the old Carlton & United brewery. I will try and check the gear ratios on thursday when I am next on site. I do know that the vertical shaft runs faster than the crankshaft, possibly by 3:1. If this is correct, I assume it is to do with a single fuel pump feeding 3 cylinders but I may be wrong. I will check for you.
Ian.

 

[johanvanzanten]

Hi Bruce,

As far as I know the kingshaft on the single cylinder MAN and Deutz engines run on crankshaft speed. This also gives a more sensitive governour. I will follow your project with interest and I like pictures! They tell me more than 1000 words. Succes with your project.

Best regards, Johan. ( the Dutch fellow )

 

[weir-smith]

Hi Johan and Ian

Firstly, Johan your model was the initial inspiration to have a go at building a similar model. I did try to track you down without any success to obtain a better feel for the problems associated with building such a model. The finish on your model was superb. I collected all of the available information on these engines that included spending three weeks in Germany and going the the science museums. The Munich Museum was a disappointment in that the original diesel had been removed and the people there were not helpful.

I found an example in Berlin but the best was in Denmark as I have said previously. I also went to Sweden and found a three cylinder "Polar" engine that used a single fuel pump for the three cylinders. It wasn't until some time later that individual fuel pumps were introduced.

If either of you are interested, you can down load a copy of the book "Diesel Engines for land and Marine Work" by A.P. Chalky. Ref to the following site. The book is out of copyright so no problems there. I have collected a lot of information on these engines and this book has the most comprehensive description of these engines as well as a considerable number of diagrams etc.


Diesel engines for land and marine work : Chalkley, Alfred Philip ...
https://archive.org/details/dieselenginesfor00chal
Appendix: Lloyd's rules for internal combustion marine engines--Diesel's original patent (p. 345-364)

In respect to the engine camshaft gears, as I have said previously I haven't been able to determine the crankshaft end gearing. On the original Rudolf diesel, the governor rotated at crankshaft speed and the cams and fuel pump at half crankshaft speed. On the later (e.g. the DM series 1904 vintage) the governor and fuel pump are on the intermediate shaft. This would mean that there are two fuel injection strokes per cycle. I know the fuel injection was not very efficient but it would be nice to know how it worked.

The compressor will not be easy to make and run safely because the lube oil can cause it to work as a diesel and fail in a spectacular way. I have studied them closely and I think the solution is in keeping the air temperature down with coolers as well as cooling the compressor cylinder jacket.

I have just purchased a quantity of thick walled SS tubing for the compressed air lines.

Johan, could you advise what type of paint you used on your model. I was very impressed with the final outcome.

Thanks

Bruce

 

[gunna]

Hi Johan and Ian

....... This would mean that there are two fuel injection strokes per cycle. I know the fuel injection was not very efficient but it would be nice to know how it worked.......

Bruce

Don't forget Bruce, the fuel pump does not cause injection. It only supplies fuel at a pressure higher than the blast air so that when the air-blast cam operates, fuel is then blown into the cylinder.
If we want to be picky, we shouldn't say "injector". Willans, for example, called it an "atomiser", I don't know what the other makers may have used.
Ian.

 

[johanvanzanten]

Hi Bruce,

Thanks for the kind words! The bigger parts of my engine are sand blasted and painted satin black with paint from the DIY store. The small parts are tumbled and treated with Steel Black, a chemical blacking stuff. This works fine and is long lasting. No dimensional changes !
See your personal maibox.

Best regards, Johan.

 

[gunna]

....... I do know that the vertical shaft runs faster than the crankshaft, possibly by 3:1.......
Ian.

Hi Bruce, they say a little knowledge is a dangerous thing, so I should be avoided at all costs!!!
My previous statement was based on the fact that I knew that the gears on the crankshaft and the vertical shaft were different diameters, (13" and 9.5" as it turns out). However, closer examination reveals odd angle helical cut forms which still give a 1:1 ratio. The gears at the top and the camshaft are at 45 degree helix, have a 1:2 tooth count ratio, and therefore give the required 2:1 ratio for the camshaft.
Ian.

 

[Mechanicboy]

Hi Bruce, they say a little knowledge is a dangerous thing, so I should be avoided at all costs!!!
My previous statement was based on the fact that I knew that the gears on the crankshaft and the vertical shaft were different diameters, (13" and 9.5" as it turns out). However, closer examination reveals odd angle helical cut forms which still give a 1:1 ratio. The gears at the top and the camshaft are at 45 degree helix, have a 1:2 tooth count ratio, and therefore give the required 2:1 ratio for the camshaft.
Ian.

Fine Hansen ownmade dieselengine has king shaft (koenigswelle) is rotating double
fast than crankshaft due better regulating the regulator for dieselpump. Then
Gearing down to 2:1 ratio for camshaft.

 

[weir-smith]

Hi Johan and Ian

Its been a great two days without power as our meter board caught fire with all of the rain we had and they have only just repaired it.

Firstly, Johan thanks for the information re painting. I would never have thought to use steel blacking. The overall effect is most impressive.

Ian, again thanks for taking the trouble to have a look at the gearing. It appears that I have made the correct choice of gearing. In the original engines there are two types where the very early engines used the camshaft to operate the fuel pump which makes sense as you need one injection per cycle. I appreciate that the pump only supplies the metered amount of fuel at the injection pressure.

The next series of engines operated the pump from the intermediate shaft which we now know runs at the crankshaft speed (see photo). This means that the fuel pump operates twice for each cycle and one would think half the amount. I do not think that the fuel metering was all that critical and in some of the marine engines that used these early diesels didn't use a governor. Basically set and forget until you reach port.

I find it all very interesting working out how it was all achieved. Note, Johan was correct in that the original engines put the governor on the intermediate shaft as it provided greater control. The governor operated / controlled the fuel input valve by holding it open for part of the fuel stroke.

I have been playing around with an experimental diesel engine for two years working out what works and what doesn't. It will go in the bin when I am finished however it has been a good learning experience.

Along the journey, last year preparing for this build, I built a CNC metal router which I can machine up to 6mm steel plate. Great fun getting it all working. I have also built a small surface grinder based on the Stent Castings which works well on small parts. As they say, its the journey that provides the pleasure not the destination.

So finally, I appreciate the input you both have provided.

Bruce