20 cc Horizontal 2 Stroke Diesel

[fumopuc]

Good to see you back in your cellar.
Out side the window the first fine snow is dancing around.

[Roger B]

Thank you  We have around 3cm of snow outside so I think the R&D department will be closed now.

[Roger B]

I then needed to modify the cam I used to operate the contact breaker to operate the injection pump. As it will have roller follower the flanks can be flat. My first thought was to use my cam jig as with precious camshafts but in the end it was easier to use the rotary table. The RT was centred and then offset 19mm (half the base circle 24mm + half the milling cutter 14mm). The two flanks were cut at the planned angles and then the RT was recentred to cut the base circle. This worked well, when installed the base circle was concentric with the crankshaft to around 0.08mm TIR 

Next step mount the injection pump on the engine 

[Roger B]

I tapped two holes in the side of the crankcase to mount the pump and cut down the mounting plate to give access to the unions. I left the piece along the bottom so I can refit it to the horizontal engine for further trials with petrol if required. Two 12mm diameter 12mm high spacers keep it in place.

As expected/hoped the cam gives a short injection time.

<a href="https://www.youtube.com/watch?v=KaU6CJTsWZs" target="_blank">http://www.youtube.com/watch?v=KaU6CJTsWZs</a>

On the horizontal engine with the excentric drive the injection period is nearly 180° (crankshaft). I need to fit the pump union to the injector pipe and arrange a fuel tank then it is smelly diesel time 

[Admiral_dk]

So next test run is just around the corner, so to speak .... 

Hope that you get closer to a constant runner soon.

[Roger B]

As diesels at generally hard to start trying this one in sub zero (°C) temps is not sensible  I silver soldered the nipple onto the injection pipe and then moved onto the governor. The 40mm diameter blank means I have to use the outside jaws on the chuck and am working inside a risky space 
Using a variety of tools I cut the cone and the central stub. The bearing bush was turned from bearing bronze. As I don't have 14mm reamer I bored the bush to 14.1 mm and the pressed it into the cone unit which bought it down to 14.02 mm. The finishing work was done on a taper mandrel.

[Brendon M]

Hello Roger, I have finally caught up again. You are making great progress.

I noted in this post your use a rotary table. Have you explained how you attach the three jaw chuck to it elsewhere on this forum?

Thank you

[Roger B]

Thank you Brendon 
This thread (hopefully) explains how the chuck fits:

http://www.modelenginemaker.com/index.php/topic,6646.0.html

[Brendon M]

Thank you Roger, that thread was very informative.

I do have one more question. Part of the reason I asked was I reckon I have the same rotary table. How do you find it's accuracy? Good enough to just bolt the adapter on, or do you do some sort of adjustment to true it up?

[Roger B]

Hello Brendon,

The adaptor plate (from RC Machines) has a stub that fits fairly closely into the larger hole in the table top. It is sufficiently accurate for my current use. I have carried out some improvements on my rotary table:

http://www.modelenginemaker.com/index.php/topic,5444.0.html

Good quality small RTs are difficult to find, the Sherline one is a possibility or the maybe the Proxxon offerings 

[Roger B]

The centre piece also had to be held in the outside jaws so most of the metal removal was by facing cuts. The keyway was cut in the lathe, a bit of a push with a lever tailstock  It was then held in a collet to face to thickness. This would have been much easier with a larger lathe, but you use what you have (or what will fit the space you have).
I then made a couple of trials with the assembly held on a tapered mandrel in the bench drill. I rapidly found that I required a spacer to stop the cone rising too far and allowing the balls to escape 
It sought of works, but there is a fundamental problem that the balls turn at half speed so that the force is reduced  The 6mm balls were better than the 5mm ones. I may try a new cone with a 30° angel instead of 45°.
Once again I have embedded the video and just pasted in the link. I can only see the link.

<a href="https://www.youtube.com/watch?v=TQuso5qq2xA" target="_blank">http://www.youtube.com/watch?v=TQuso5qq2xA</a>

<a href="https://www.youtube.com/watch?v=TQuso5qq2xA" target="_blank">http://www.youtube.com/watch?v=TQuso5qq2xA</a>

[Roger B]

I had used up my slices of 40mm free cutting steel and had to start using a length of bar. I had hoped that I could cut the 30° cone directly on the end but there wasn't enough space so I parted off a slice. It's difficult to swivel the Hobbymat topslide to get the required angle but I was able to hold it in place with a toolmakers clamp.
The test results were not much different to the 45° cone. It tends to stick in the closed condition and then suddenly spring open  It seemed to work better if it all rotated together so time for a rethink 

[Roger B]

I found a picture of a Junkers governor which appeared to have a similar ball and cone arrangement and used a small ball race running on the face as a thrust bearing. I decided to try this arrangement. By increasing the thickness of the bronze bush I could make space for a 2mm keyway to keep the parts rotating together. The cone was made in the same way as before and I had to make a 14mm bush for the keyway broach.

[Roger B]

I made a trial shaft and a couple of collars for the next tests rather than using the tapered mandrel. The governor disk has a reduced height keyway which required a stepped 3mm key and I filed the rounded ends on the 2mm key for the cone. I was able to put together with only few donations of 5mm SS balls to the swarf gnomes  and gave it a try using a 6mm diameter ball race held on an M3 bolt.
This seemed to work quite well but I will need to make a bell crank and a spring support to test it properly.

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

[Brian Rupnow]

That is interesting, Roger. I have never seen a governor like that before. I have made and experimented a bit with the old "fly ball style" steam engine governors, but that style is a new one on me.---Brian