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1/2 Size KyKo Hot Air Engines

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vtsteam:
Photography is first class.  :praise2: really good lighting. Like Jason, I was wondering if the cylinders were die-cast together?

Alyn Foundry:
You certainly like your hot air engines Dave….  :ThumbsUp:

Do you have one of my Robinson’s, he asks cheekily.  :lolb:

I too have been looking at the pictures, I would guess at the “ lost foam “ process? There’s strange looking slumps in the fin detail but they have come out really well otherwise.

 :cheers:  Graham.

Dave Otto:
Thanks for the comments guys, they are appreciated.

The cylinder casting is one piece, what looks like a split line is just a height difference in in the raw casting. This step gets further machined to accommodate the cover, you can see this in the 4th photo above.
The cover needs to sit below the boss for the displacer flange.

Graham I was thinking that these were lost wax but I suppose they could be lost foam. Certainly not as nice as the castings from Morrison and Marvin but I think they will work out ok.
I do like hot air engines, and have a few other kits on the shelf but the Robinson is not one that I have.  ;)

Dave

Dave Otto:
Hi Everyone

There is one more operation that is required on the cylinder and that is to drill the transfer port that connects the two cylinders. The process that I used to do this will be detailed below. But first there are a couple parts to make.
First up to is to make the upper displacer cover and bushing.


The brass stock was clamped to a sacrificial plate in the mill. The hole pattern was drilled and tapped into that plate. Then the brass was clearance drilled for the screws.



The screws were installed and the clamps removed.



The CNC was used to mill the profile and hole for the bushing.



The bushings were turned from 660 bronze stock and parted off.



Then the bushings get soldered into the cover plate. The bushing also serves to center the cover in the displacer bore.



Here is a shot of the covers setting on the cylinders.



Onto the ports, a bushing was turned to be a nice slip fit in the power cylinder bore. The bushing was also reamed for slip fit on a tooling ball shank.



Here is a test fit of the tooling ball, this one was purchased from McMaster Carr.



Getting setup to mill the hole, my precision vise was set at a 21 degree angle using angle blocks and a dial indictor.



Now with the cylinder mounted in the vise the bushing and tooling ball are inserted into the bore. Using a test indicator the ball was indicated in. This gives me 0,0 in both X and Y. Z does not matter in this operation because it is a through hole.



I didn’t do any fancy trig to find the hole location, I just sketched it up in Alibre. It was a simple matter of moving over in x to the hole location. The hole needed to be 1/8” so I used a 1/8” end mill to put the hole in.



The next part to make was the bottom covers for the power cylinders. I did not take many pictures but it was a pretty simple turning job. After parting off, the cover was flipped around and held in a 1” collet and faced to thickness.



For the next operation, I milled a pair of soft jaws to hold onto the 1” spigot of the cover. The holes were drilled, countersunk and the flat machined.



Here is a shot of the covers installed on the cylinders.



Looking down the bore you can see how the transfer port is just touching the cover. I probably could have just winged it but I thought the tooling ball approach would be a fun exercise with some added precision.


Thinks for stopping by, more to come.
Dave

steamer:
that's a pretty cool looking engine Dave,    I would love to see a picture of the original engine as well somewhere along the build.     :popcorn:

Dave

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