CHUKY - Build One Yourself

[Jasonb]

I remember seeing the CHUK range of engines when Graham first posted them on the Alyn Foundry website and quite liked the look of them but as I was engrossed in building my Fowler traction engine at the time did not have the need for more engines.

With the demise of Alyn Foundry I had put the engines out of my mind until Andy started a build thread on his set of castings which got me thinking about building a flame licker. There are a few designs about but they do all look as though they were made from bar stock which in fact they are! I still liked the look of the CHUK and was able to borrow the build notes that came with the engines, these combined with looking at Andy's engine photos and a bit of artistic license allowed me to come up with the design shown below. Despite what some people said in Andy's build thread if you want to make an engine enough you don't need dimensions on every feature to copy



I have made a few engines recently with a 24mm bore which I find quite a nice size as they are not too big to handle or display and there are no large bits of metal needed that will break the bank. So this engine also has a 24mm bore which makes it about 2/3rds the size of the original CHUK, stroke is 32mm and the flywheel is 102mm dia and also the only casting used but at that size could be fabricated quite easily. I have tried to add a bit of shape to the parts so that they look like they were made from castings rather than make just another barstock engine.

The work is mostly milling or turning from solid although there are two items that will require silver soldering, even then one could probably be done with some small CSK screws if you don't fancy soldering. There are also several parts that need lapping, the flat ones can be done easily enough on a flat surface with fine wet and dry but the cylinder also needs lapping as does the piston.

A big thanks to Andy for posting his original build and help with the build notes and also to Graham Corry for coming up with the engine in the first place and also giving me permission to share my design drawings with the membership so lets start making swarf.

I have also attached the 3D pdf which should allow you to look around the engine design in detail

[Jasonb]

BASE

Drawing #1

This can be made from a slice of 75mm or 3" dia aluminium or could even be done from some 12mm plate. I started with a slice of round bar, held in the 3-jaw to face off and then bore the 28.5mm hole right through. I also removed some of the waste by turning a 60mm dia spigot.



The spigot also made it easy to hold the base the other way around to face off the bottom.



The base can then be mounted on the rotary table and clocked in true to the spindle to start shaping the raised area. I used an old 10mm dia milling cutter with the corners ground off to a small 1mm or so radius so that it left a fillet as you tend to see on castings but it could be left square if you prefer. Start by cutting in from one side until the face is 21mm from centre.



Next cut the two sides, I have shown the point where the 10mm cutter should stop at 22mm in the Y axis and 13.86 in the X axis.



The table can now be rotated to reduce the rest to 42mm dia



Next add the decorative moulding to the edge, an old 6mm dia cutter can be ground by hand either on the corner of the bench grinders wheel or with a dremel which will give an acceptable shape.



While held like this the Hole for the chimney can be drilled 9mm and then tapped M10x1, if you don't have fine pitch metric taps then 3/8" ME threads would do.

The base can now be held upside down in thevice with teh flat edge against the fixed jaw, clocked central to teh spindle and the four M3 clearance holes drilled, I tend to use 3.0mm drills for this as teh socket head CSK screws tend to come in at about 2.8mm OD. I won't keep mentioning it but ease the edges of all holes either with a CSK bit or a lathe tool ground at 45degrees, you will often see these tools in the photos as it it the last op before taking the pic.



To mill the exhaust passage I dusted off the swivel base for my vice which was the first time I have used it in the 10yrs since I bought it, set the vice to 45degrees and then with an 8mm cutter cut the slot 3mm deep . If you don't have a swivel vice base then the base can be clamped directly to the mill table and the angle is not critical.



Thats the first part out of the way

If anyone spots any errors on the drawings please let me know and I will update them, also feel free to ask any questions.

[Gas_mantle]

Thanks for taking the time to upload this build, it's the kind of thing I may be interested in having a go at making 

[crueby]

Excellent start, going to be following this one. Thanks for posting it!


 

[10KPete]

 

I like this one. There's something about the exhaust note and it will also run pretty slowly. Not too big and not too small.

Yep, gotta do this one!!

Thanks for bringing this to us.

Pete

[Jasonb]

Sub Base

Drawing #2

Start by cutting a piece of 6mm aluminium a little larger than the 110mm required, locate the middle and dot punch. Mark out a 110mm circle with a pair of dividers, roughly mark 45degree lines and saw off the corners.



Clamp the plate to the mill table with some packing underneath then proceed to drill the four M3 clearance holes and the four 4.0mm holes which will be used to mount the engine to a wooden display base. Then with an 8.0mm dia milling cutter counterbore the 4.0mm holes 3mm deep and also cut a flat bottomed hole 2.0mm deep in the middle of the plate to locate the valve spring into. If you have a larger spring then make the hole to suit. Once removed from the mill table the underside can have the M3 clearance holes countersunk so your screw heads sit just below the surface.



Screw a piece of ply or MDF to the lathe faceplate of if you have a large enough 4jaw then the board can be held in that, use the tailstock centre in the dot punch mark to hold the plate to the board and then screw it on through the 4.0mm holes and turn the outside down to 110mm diamater.



Blue the plate in a couple of places and then offer up the base using a couple of screws in the M3 holes to line things up and scribe on its diameter.



Swing the topslide right round and set to about 4degrees then taper the edge of the plate until the cut runs out where the scribe marks are.



The last turning job is to add the decorative moulding to the edge which can be done by grinding up a small HSS form tool.



Finally back to the mill, pop two drill bits into the 4.0mm holes and locate them against one of the tee slots then locate the middle of the plate. Using the 8.0mm cutter again cut the other half of the exhaust passage 3.0mm deep



And a quick picture of the two parts together, I will give details of the spring later.



J

[crueby]

Great step by step - nice work!

 

[NickG]

Watching with interest, nice looking engines they are, and your CAD model looks good.

I have to say I've made 3 flame lickers now and the pistons and cylinders do require a good fit. I tried lapping at first but was unsuccessful, what worked for me was just focussing on making sure the bore and pistons were parallel. So I used an adjustable reamer with plenty of oil for the bore and just a finely turned finish cast iron piston to keep things nice and square. So it can be done without lapping - my lapping failure was probably due to my poor technique, tools and lack of patience though.


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[crueby]

Can they work with a viton o-ring as a seal? How much friction can they take and still run?

[awJCKDup]

Looking good, I'm following along, and downloading plans. Keep up the good work, and thanks.

John

[wagnmkr]

Jafa Cakes and coffee in hand for this one. Just LOVE the sound ... we have Harleys around here that don't sound that good.

Tom

[Jasonb]

Thanks Chaps, good to know you are enjoying the build.

I think using O rings would add too much drag on such a small engine, you may get away with it on a larger version where there is a bigger volume of gas to cool and more momentum from the flywheel. Also not an adeal combination of flame and vitron. As you will see later it is not to hard to lap the piston into the bore so worth having a go.

Maybe Graham could comment on the use of o rings if he is looking in.

[Alyn Foundry]

Maybe Graham could comment on the use of o rings if he is looking in.

Hi Jason.

Indeed, reading with great interest. I wish we'd have had this form of communication back in my heyday!!

http://www.modelenginemaker.com/index.php/topic,7187.msg150758.html#msg150758

The engine mentioned above was made from some of the last Iron to leave the Rhuddlan foundry.

The grade was about 17 , meaning it could be brought to a mirror finish, literally you could see your face in it! Martin and I both had the Delapena system of honing and were able to get both finish and parallel cylinder bores.

CHUK 2 being an inverted vertical meant that two forces were working, gravity and atmospheric pressure. That's the reason why out of the three styles CHUK 2 ran the best.

Patience is the key word, as Andy pointed out, a lot of lapping involved. I too found that music aided the process immensly.

Kind regards, Graham.

[NickG]

Yes, the lower the friction the better so I would say any kind of piston ring would be a no no. The power output is tiny by comparison with a steam, ic or even Stirling engine, relying only on the difference between atmospheric pressure and the under pressure caused by cooling of hot gas in the cylinder.

I used graphite for the pistons on both poppin engines to good effect, was very easy to obtain a good fit and self lubricating.


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[Jasonb]

Cylinder

Drawing #3

This is probably the most involved part of the engine but if you take it one stage at a time it should not present too many difficulties.

It is just possible to squeeze the cylinder out of a piece of 50mm dia cast iron bar, anyone in the States thinking of making this will have a little more to play with by using 2" stock.

Start by sawing off a piece a few millimeters longer than needed and then lightly face to clean up the ends. Blue the end of the bar and then lay it  onto a flat surface and scribe a line at centre height, roll it 1/4 of a turn and mart a cross line 3.5mm below ctr height. Accurately punch where the two lines cross.



Set the punch mark to run true by holding the bar in the 4-jaw chuck.



Then spot drill followed by drilling out most of the material with several drills of increasing size until you get to about 18mm when the rest can be bored out.



I like to do the last couple of cuts with a HSS boring bar as I find that springs less but even so take a few passes at the final setting to let any spring work its way out and hopefully you will get a parallel bore. Aim for something like 23.90mm which will allow for honing and lapping but as the piston will be made to fit the bore the turned finish is what to aim for not the exact size.

Talking of sizes I did not use a micrometer once on this engine all measurement was with a digital calliper.



Take a finishing cut across the bar and then take another 0.5mm deep cut to leave the small raised area 28.5mm dia, this raised area will make it easier to lap the end of the cylinder later.




The work can now be reversed in the 4-jaw and the bore set to run true, make sure you can machine down to the top of the valve face which will probably mean the work is away from the chuck face. You may just be able to see that I have a piece of 1" material between chuck and work so it can't get pushed back by teh tailstock. NOTE this must be prevented from flying out for which I have used hot melt glue. Bring up the tailstock ctr for support and rough out to about 43mm dia.



Then with a tool that can get into a corner turn to 42mm finished dia and to leave 16mm for the port area.



Now form the spigot on the top of the cylinder to leave the 42mm dia section 50mm long.



Continued in next post.