20cc Four Stroke Diesel

[Roger B]

Thank you for your interest and support   

I decided to use the larger radiator and used a mixture of already existing and new fittings. This engine is a bit of a 'Bitza'. The radiator support frame may seem a bit over the top but vibration is always a problem. With the cooling set up I took it back into the welding bay for further trials. After some more timing adjustments it would start immediately when warm with a good response to the fuel rack. It has the usual diesel problem that as the revs drop the injection quantity drops until it stalls, this is why all diesels have governors. I don't think that the atomisation from my injector is so good, I have a delightful term I learned from the Smokestack Forum of a wet pipe engine 

<a href="https://www.youtube.com/watch?v=I0Yqmevrq50" target="_blank">http://www.youtube.com/watch?v=I0Yqmevrq50</a>

<a href="https://www.youtube.com/watch?v=I0Yqmevrq50" target="_blank">http://www.youtube.com/watch?v=I0Yqmevrq50</a>

Bringing the engine back to the workshop there were, as expected, a few problems. In less than five minutes run time I had emptied the oil reservoir. As this was not in the crankcase it has been blown out somewhere. The two M2 nuts had fallen off the injection pump tappet roller but due to the construction the pivot remained in place. One of the soft soldered oil pipes had also cracked. Vibration is a problem.

I need to make a few more tests on injection quantity and timing as well as some more development on the injectors. It's getting there   

[Vixen]

Hello Roger

Well done   
That's a nice reward for all your hard work and dedication.  Some minor changes and adjustments and you will be there.
 
Mike

[RReid]

Congratulations Roger! You took on a real challenge and have good reason to be happy and proud to get to this point.

[Zephyrin]

all this thread is very fascinating...
the amount of tests and changes to get successful run are really impressive, congratulations Roger and thanks to share !

[Admiral_dk]

Oil-Pipes - why not have a few strategicly placed 'Rubber-Hose Joints' in the places (or close to) where the Pipe usually cracks    It certainly works fine on my Suzuki DR350 - admittedly for Lubrication Oil.

The other possibility is a number of strategicly placed rubber grommed holders to 'Fix the Piping' to the Engine - as this should prevent the Pipe to 'Shake to a different Pattern' than the Engine. I remember seeing this on the First Golf GTI and it's mechanical Fuel-Injection - between the Pump and the Injectors, there where a number off combs, holding the Pipes.

I thought that the Guv'nor on a Diesel was to prevent Run-Aways .... but I can see it be useful in all RPM ranges.

Per

[Roger B]

Thank you all 

This was just a soft soldered joint in a lubricating oil pipe union that cracked. The injection pipe is silver soldered and has survived all the trials so far.

I need to decide what to do with the lubrication system  The oil pump delivers a small quantity of oil at very low/zero pressure to both main bearings. The big end is fed via drillings in the crankshaft and the resultant spray hopefully lubricates the cylinder and little end. The oil remaining in the crankcase was planned to be blown out by the crankcase compression as in the prototype Field Marshall.

In these trials the surplus oil was thrown out of the top of the crankcase via the original inlet port (the reed valve was removed) hence the rag on top of the engine.

I could machine out the bottom of the crankcase to make sump or I could put the reed valve back in place and blow the oil back to a tank. Needs some thought 

[Roger B]

The next step was to finish the new camshaft. The one fitted is a reject from my horizontal petrol engine which has negative overlap. The new one will have the same timing as the one now fitted to the petrol engine. The lobe assembly is made from 16mm diameter silver steel and hardened, the shaft is 6mm silver steel not hardened.

The keyways in the shaft were cut with a 2mm Woodruf key cutter. As before the lobes were milled in 6° steps using a DTI to set the depth of cut with each cut being ticked off on the table when completed. For this operation the lobe assembly was held to the shaft with an M3 grubscrew. The lobes were then polished, hardened and polished again. Next the lobes were (hopefully) correctly aligned with the keyways and the shaft was spotted through the grubscrew hole. I then filled a small flat on the shaft and the two pieces were assembled with some medium strength Loctite and the grub screw.

Finally a sanity check on the timing, with the drive side keyway on top the valves should be on the overlap (remembering that it is a horizontal engine) with the exhaust valve closing.

[Admiral_dk]

Great looking Camshaft Roger 

One option for the Crankcase is to install the Reed in such a fashion that the pressure can get out, but not back in. This princip has been used on some racing engines to lower pumping losses, but also to avoid Oil-spillage - that might also prevent it from (partly) running on the Lubrication Oil ....

Per                 

[Roger B]

Thank you Per  I'm still pondering the oil system 

I fitted the new camshaft. There is definitely overlap now and the inlet valve closes significantly earlier. I had to set the camshaft timing very carefully to avoid the valves hitting the piston and at the first test the compression pressure is 40 bar plus, probably too much  The starter dog was slipping on the crankshaft. I may need to make some shims to increase the thickness of the head gasket. That is always reversible, machining things isn't.

<a href="https://www.youtube.com/watch?v=-P4Dor2e-B0" target="_blank">http://www.youtube.com/watch?v=-P4Dor2e-B0</a>

<a href="https://www.youtube.com/watch?v=-P4Dor2e-B0" target="_blank">http://www.youtube.com/watch?v=-P4Dor2e-B0</a>

<a href="https://www.youtube.com/watch?v=g8y0zJQFtUU" target="_blank">http://www.youtube.com/watch?v=g8y0zJQFtUU</a>

<a href="https://www.youtube.com/watch?v=g8y0zJQFtUU" target="_blank">http://www.youtube.com/watch?v=g8y0zJQFtUU</a>

[Admiral_dk]

Don't forget that most starters are geared down - so maybe you aren't in the right gear 

Per

[Roger B]

I had a look at the starter dog to see why it was slipping on the crankshaft. This was a problem in the past when the clamp was only slit on one side but having slit it right across it seemed better. At the time I turned the end of the crankshaft down to 11.5 mm and sleeved it back to 12 mm. Removing the starter dog showed that the sleeve had given way under the load  I decided to remove it completely and modify the dog to 11.5 mm bore. A quick shot through with an 11.5 mm reamer plus some filling of the faces seems to have solved the problem 

I need to do some more work on the injectors (in the Fuel Injection 2 thread) before the next trials. I will keep the compression where it is for the moment.

There is a problem with the links to my videos  I have repaired the recent ones but to fix it all will take some time 

[Roger B]

I had a quick trial with the new needle style injector. There are some problems with the design but it ran. The biggest problem is still un atomised fuel blowing out of the exhaust. It was running 3-4000 rpm.

<a href="https://www.youtube.com/watch?v=NncOlT-Vfxw" target="_blank">http://www.youtube.com/watch?v=NncOlT-Vfxw</a>

[RReid]

There are some problems with the design but it ran.

Still a very positive result. Having recognized the problems, do you see a pathway to addressing them? (edit) Sorry, posted this before reading your latest on the FI thread!

[Kim]

You have the coolest experiments, Roger!

Looks like it blew a lot of oil around there.  Is that the atomized fuel you're referring to?  (Asks a very non-IC person  )

Kim

[vtsteam]

Roger, still following and enjoying your working through this engine and injector!