Hemingway 1/12 Ransomes and May horizontal engine

[samc88]

I got the valve rod finished this evening, the plans call for the threaded end that goes in the fork to be 9BA but I cant see the reason for that as the fork has plenty of metal to accomodate a larger thread so Ive threaded it 7BA instead.

With that done I made up the valve nut which was a simple job from some 1/8" steel. I will look at the fork and the slide valve itself next

[Minh Thanh]

Interesting project 

[samc88]

Next up was the slide valve. In the kit Hemingway supply a great big chunk of gunmetal which is meant for you to carve bits out of to make various gunmetal parts in the model, I had a bit of square bronze however that was just a shade over 1/2" so I used this instead since the valve is 1/2" across.

I started on the recessed side, I milled the end, then the sides to size and finally the top face. I first cut the slot using an 8mm diameter slot drill before switching to a 1.5mm cutter to bring the corner radii down.

With that done I flipped it over in the vice and milled the height down to 9/32" before milling down the sides to 1/8" thickness. Next I milled the 1/8" slots using a 3mm slot drill. Before cutting from the bar I did run a file on the edges of the castellations as the draeing shows these as angled for clearance.

I then cut the valve off the bar and milled to length before hitting the ends with a file to make the angled surface shown in the drawing. I did have to open up the steam chest slightly with a smooth file but it all fits together quite nicely and smoothly moves up and down over the port face. Very satisfying part to make

[Charles Lamont]

Nice. A bronze valve should wear better than gunmetal on gunmetal anyway.

[Michael S.]

Well done.
Looks good!

Michael

[samc88]

Back to it today and made the valve fork. This started off as 1/4" square bar which was milled down to size and then drilled and reamed through before machining the slot. I then put this in the self centering 4 jaw and with a grooving tool the diameter was machined. In this setup I then drilled and tapped the 7Ba thread for the valve rod. Whilst it was attached to the bar I filed the radius at the top and then cut the fork off and faced to length.

I did make a start on the piston too, made the rod and started on the piston itself, I will post that up tomorrow when its finished

[samc88]

Got the piston finished thus evening. The way I machined this was to rough turn the piston, machine the end of the piston rod that goes into the crosshead and then machine the end the piston goes on. Once that is machined I fit the piston to the rod without taking it out of the lathe and then finish the machining to make sure its all concentric. I machined the groove to take a silicon o ring, this approach worked really well with my S50. The oiston is a nice fit in the bore, sealing the inlet and exhaust and blowing down the bore moves the piston which is a promising sign!

I then moved my attention to the cylinder covers, first clocking the previously machined casting in the 4 jaw and machining the recess for the gland and the 1/4" hole through. This was then parted off. I will do the register a little later on, I think I will make a jig so I can hold it true in the lathe so its concentric to the bore  With that done I faced the upper cover to just shy of final thickness to let me skim the other side. The chucking stub I will use to make the neck ring.

Im not sure I see the point of the neck ring, why not ream the cylinder cover to fit the rod rather than have the seperate piece, is it a wear item on full size engines?

With that

[samc88]

Back into the shed and made some progress on the upper cover by machining the register. Next step will be move it to the mill and drill the fixing holes

[modelsteam]

Excellent progress, keep up the good work.
            Chris   

[samc88]

Finishing off the upper cover, drilled the holes and the recess in the centre and then machined the clearance for the passages and cylinder drain. Then I made a fixture to hold the cover in place for facing the upper side

[samc88]

Found a bit of time to skim the upper cover and finish it off tonight. Next Ill finish the lower cover whilst the fixture is in the lathe

[crueby]

How does the fixture grip, glue?

[samc88]

How does the fixture grip, glue?

Turned it to a good push fit and then a little bit of super glue

[samc88]

I got some time in the shed and finished the turning of the lower cylinder cover. I just need to mill two recesses on this and then it os finished. I just need the neck ring and then I can test the valve and piston assembly with air

[samc88]

Cylinder cover is finished along with the neck ring and the gland. Just need to make some studs and nuts to hold everything together and then it can be tested before moving onto the next part of the engine. The gland body was slightly too large for the bore in the cover so made a quick mandrel and skimmed it down. Its looking promising, the piston is nice and free with a bit oil to lubricate the o-ring