20 cc Horizontal 2 Stroke Diesel

[Roger B]

I then went back to milling mode to bore out the big end and round the little end. After centering the rod to the scribed lines I opened out the hole with a 10mm endmill and finished with the boring head. Both were fed using the quill rather than the Z axis feed screw.

The little end was rounded using the RT and then cleaned up by filing. Once again I went a little too far round with the RT and ended up with a couple of marks that were too deep to remove. I need to check my geometry on this 

[Admiral_dk]

Nice to see you back on track     

[Roger B]

The next step was to machine the cylinder mounting face on the crankcase as well as an access hole on the opposite side to allow the big end to be assembled. This hole has a recess for a cover plate which I may also use as a mounting point for the initial reed type inlet valve.

The fixing holes were drilled to the appropriate tapping size and the main hole was opened out with a 15.5mm drill before being bored to size. It may have been quicker to have removed the bulk of the metal with a hole saw as I have done with some cylinders an liners.

The cover plate recess was cut using a 10mm endmill in 1mm steps. As it was centered over the fixing holes center cutting was not a problem.

[Roger B]

The fixing holes for the crankcase sideplates were drilled next. I have a small 4 jaw chuck with an M14 x 1 thread which will fit my RT as well as the lathe. The RT was fixed to the table, centered and then offset 34mm. The chuck was mounted on the lathe and the first sideplate was centered and the transferred to the RT for a round of center drilling at 60° intervals and then drilling through 3mm. The first plate has an additional center hole due to me thinking that 240 + 60 = 320  . The second plate doesn't have any unique features (yet).

[Roger B]

Finally for today I drilled the fixing holes in the cylinder mounting plate and milled the transfer passage in it.

The next step will be to mill the clearance for the connecting rod in the crankcase and the cylinder/cylinder mounting plate.

[Roger B]

The crankcase and the cylinder were clamped to the angle plate at the appropriate angle (14°) and the clearance slots were cut with a 12mm end mill. I plunged the end mill using the quill feed, moved another 0.3mm and plunged again. As the finish was not so important it was quicker than using the Z feed screw.

A quick check with the conrod looks ok. The little end is below the center of the cylinder.

Back to lathe mode to make the big and little end bearings and to lap the cylinder. I have an 80mm offcut of stainless steel that will be suitable for a flywheel if I can turn it (I had problems with a piece of P20 mould steel that I used to make my ER25 collet chuck ), scrap bin stuff can be good but you sometimes need to know more than is it magnetic or not 

Luckily it seems ok, I faced it at 500 rpm (as the lathe was set to this) with SS insert and got a good finish without bright blue swarf 

[Roger B]

On with the flywheel. I turned away part of the center to reduce the weight a bit. This required three different tools, a straight tool to start and to finally face the inside, a RH tool to turn the boss and a boring tool to turn the inside of the rim. I had planned some radiuses inside, but my TC radius tools were not happy to cut this SS. The normal inserts that come with the tools were also not happy, the only tips that would not break and gave a good finish were some Mitsubishi ones I got from CTC.

With the first side completed I turned the tapered bush from a piece of (not so) mild steel. I got the best finish with an aluminium tip. The taper is 6° inclusive. The compound will stay at this setting so I can bore the flywheel to the same angle and by making the bush first I can check the fit/depth of the hole in the flywheel.

[Roger B]

The flywheel was put back in the lathe and faced. A quick skim on the rim showed that it was almost concentric with the first side. The final finish on the rim will be done with the flywheel mounted on a mandrel.

A 12mm hole was drill through the center and the taper was bored with frequent trial fittings of the bush. With this shallow angle it is very easy to go too deep  This side will then be recessed to match the other one.

[Brendon M]

Hello Roger, I am still following along. 

[Roger B]

Thank you Brendomn 

I finished machining the recess in the flywheel and then inserted the tapered bush with a couple of light taps with a plastic hammer so I could index the holes for the clamping/removal system. I still haven't made any form of indexer for the headstock, but the center height above the base is 120mm, the chuck jaws are 10mm thick so a depth gauge set to 125mm allowed me to index 6 holes at 60° using the chuck jaws.

This engine requires a reed valve inlet and as this is new to me (other than a brief mention in Malcolm Stride's book) I started searching the Internet for more information. I rapidly came across a UK firm (Petrol Scooters) selling complete unused reed valve assemblies for £1.99 that looked like they would fit    I splashed out and ordered 2 sets as well as a set of carbon fibre reeds (might be better, might not    ) These arrived today and look hopeful   

[Admiral_dk]

Nice to see that you're still on this project.

Looks like you got the orientation of the reeds right in the last picture - you should remove enough material so you get a straight flow from the reed to the transfer port 

[Roger B]

Thank you Per. I am also selecting the direction of rotation (anticlockwise in that picture) so the rotation aids the flow.

The next step on the flywheel was to finish the holes for the taper bush alterately M3 10mm deep and 3mm diameter 5mm deep. When the tapered bush is turned 60° this allows alternate hole sets to clamp the bush onto the shaft or to push the flywheel off the bush. The bush was then slit along one of the threaded holes with a 1mm wide slitting saw.

After some deburring the flywheel was mounted an a 12mm silver steel mandrel to allow the final skim of the rim. Finally I tried it on the crankshaft to check for any visible run out. Looked ok 

[fumopuc]

Hi Roger good to see some more bits and pieces. I think your country also has a bank holiday tomorrow, which may be gives some extra shop time.

[Roger B]

Thank you Achim  , unfortunately our day is the 1st August.

The next step was to make the big end bearing using the split and soldered bronze offcut from my horizontal engine. This already had a reamed 12mm bore so I mounted it on a 12mm mandrel and turned the outside to 16mm. It then went into a 16mm collet to be faced to length. Next it went back on the mandrel to machine the center down to 14mm. When it was almost 14mm (~14.2) it split along the soldered joint     I tried to resolder it but couldn't get a good enough alignment to allow me to turn down the last 0.2mm and keep it concentric 

I will start again using the same technique as on the horizontal engine so that the two halves are held together by the 4 jaw chuck as well as the solder until the final parting off.

[Roger B]

I had to go to milling mode to split another piece of bronze for the big end and while it was cooling after being sweated together I decided to fit the reed valve assembly. This time I decided to remove the bulk of the material with a 29mm hole saw. The recess for the valve was cut with an 8mm end mill.