1/2 Size KyKo Hot Air Engines

[Dave Otto]

Hi Everyone
Well I guess I’m off onto another fill in project. I purchased two sets of ˝ sized KyKo, hot air fan castings a few years back. They were obtained at different times from eBay; the second set was cheap enough I couldn’t pass it up. They came with the castings, materials and hardware. I won’t be using the hardware for two reasons, 1st I don’t have any BA taps or dies and 2nd my plan is to recreate at least some of the hardware to better match what was used on the original engines. I do have two full sized engines that I can use as a sample to go by. Also I won’t be using the materials supplied as it is easier to use my own materials than to try to deal with all the little unknown chunks of mystery metal in the kit.


There was a copy of the ME build series from 1997 so this engine kit has been around for a while.


My plan is to build both of them at the same time, one will be built as a ventilating fan and the other will be built as a stationary power source as some of originals were. Back in 2016 Andy (Chipmaster) was kind enough to supply me with photos and dimensions from some engines that a friend of his owns. Someday I would like to turn my full size incomplete engine into a stationary engine; my other KyKo is a fan. This information was very helpful in creating the model of the stationary engine.


I will also be adding some details to make my models more like the original full sized engines. This will be items like grease cups on all the bearings and cast in oil cups on the connecting rod, more on that and other changes later.



I have the stationary engine pretty much complete in Alibre with only a few small details to work out.
I have been working on this in my spare time for a while now. I will probably also model the fan parts. The basic engine is the same for both.


Here are the cylinder castings with some work complete. The flange on of them had been sawed off of the sprue and was too thin to clean up to print. The flange is not very thick at best and needs to be drilled and tapped for the A frames. I decided to face it until it cleaned up and then bonded on another piece of aluminum with JB Weld epoxy. Then it was faced to the proper thickness.
If you look close you can see the joint on the left hand one in the photo. The new plate was also over sized and milled back to proper size when set up in the mill.


An expanding mandrel was made to fit in the cored displacer bore. The cylinder was faced on both ends to the proper overall length.


The cylinder was mounted and squared up on a fixture plate. Both bores were finished using a boring head. The power cylinder flange was faced to the proper height which could not be done in the lathe. Lastly the screw holes were put in for both cylinders. I added 2 holes in the pattern for the displacer which is the way the original engines were


Then over to the UPT to tap all the holes, I really love this tool.


To machine the hole pattern on the top it needed to be indexed with the bottom. A simple fixture was made so the cylinder could be mounted in alignment with the face between the two cylinder bores. Hard to see but there is a raised portion at the rear of the fixture.


That was a lot of work to align eight holes but at least they are in the correct location. Four holes are for the A frames and the other for are used to mount the fan shroud on the stationary engine; and for the carrying handle on the fan.


More to come.
Thanks for stopping by.
Dave

[vtsteam]

 

[RReid]

I'll be following your progress with interest, Dave.

[Kim]

Looks like you're off to a great start, Dave!

Always love following along with your builds   

Kim

[Jasonb]

Dave, are the two cylinders separate castings that are joined together, if so how? From the photos it looks like there is a joint line even after facing the ends.

[vtsteam]

Photography is first class.  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…. 

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

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.

   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.     

Dave

[Kim]

Beautiful work, Dave! 

Kim

[Jasonb]

I've not seen those tooling balls before, I assume the ctr of the ball is a set height above the flange on it's shank. Also how are you locating teh ball, it looks like you are finding the high point with a Dti (or is it being rotated) rather than locating front, back and right hand side

And did you bead blast the soldered parts to clean them up as nice as they look?

[Dave Otto]

Thanks for the comments guys, always appreciated.

Dave, I will upload some photos of original engines in a future post.
Jason, you are correct the center of the ball is a known distance from the flange. When indicating the ball the indicator is swept around above the centerline (or equator) of the ball, you need to be high enough to clear the shank with the tip of the indicator. You need to align the center the ball with the spindle axis. If you need to establish a precision depth you can also touch off your tool on the top of the ball and figure your depth from there. The balls come in lots of different sizes; this one is ˝” in diameter and ˝” from the center of the ball to the base of the flange.



To start with I modeled the bushing and tooling ball in the cylinder.



Then the 3d body was cut in half, and using the cut face a sketch was created and the profile extracted.



Here is the result of that, and then it was a simple matter of measuring the distance from the center of the ball to the center of the transfer port.

Yes the cylinder cover was bead blasted; I have a small cabinet in my shop that I built years ago. I keep 170-325 Mesh glass bead in it which is quite fine, I do like the finish that it leaves.

Dave

[Jasonb]

Thanks for all the details.

[Dave Otto]

Hi Everyone
The next parts to be worked on are the A-frame bearing stands. They are brass investment castings, and like the other castings the quality is good but not great.


There was one side of each casting (same side on each one) that was pretty flat and with a few strokes with a file they could be mounted on a tooling block. A cleanup pass was taken across the bottom of the feet.


Then using a height gauge, it could be determined how much more material needed to be removed from the feet to bring the bearing boss to the proper center height.


After the height was established a temporary hole was drilled and reamed centered on the boss.


The full sized original engine had bosses on the tops of the A-frames for grease cups. In this photo you can see that these grease cup bosses have been machined and silver soldered in place. Later on these bosses get faced off, drilled through and tapped for the grease cup.


Next while working in pairs the A-frames were mounted to a fixture plate and indicated to be level. A drill blank was inserted through to keep the castings aligned and also used to pick up the center line for the crankshaft.
Working from center the mounting holes were drilled and the outside edges machined to proper width. The screw holes were spot faced on the top side in the drill press using a standard piloted #4 counter boring tool.


I needed a way to hold the frame so the bearing bore could be machined perpendicular to feet. Holes were drilled and tapped into a soft jaw then mounted in the vise. The A-frame was screwed to the soft jaw and then the vise lightly tightened.

In this photo the bore has been machined using a boring head to fit the 8mm ball bearings. Also the square boss for the pinch clamp is machined to proper length. The as cast part had the gate here and was also too long.


Using the same fixture as earlier the bearing pinch clamp feature can be machined. Here the 2-26 hole is being drilled and tapped. In this setup the grease cup boss is also drilled and tapped.


After the clamp is drilled and tapped it is split.


Enough screws were made for the A-frames and the other holes that will be used to mount the fan shroud on the stationary engine; and the carrying handle on the fan. These screws are patterned after the originals, they are kind of like a cheese head but have flat tops.


Here is a shot of the A-frames mounted on the engine I still need to make the matching screws for the bearing clamps.

Thanks for checking in,
Dave