Ky-ko Fan modification— help!!

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Pmcguire

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Hello all,

Been a big fan of this site for about a year now, but this is the first time I’m turning to the community for help....and I need it!

I have been building a modified version of the ky-ko fan using Julius de Waal’s plans (here: http://www.vapeuretmodelesavapeur.com/telechargements4/kyko-fan-stirling-jdw-complet.pdf ). Basically, the only bits taken from the plans are the dimensions for the cylinders and the width/length of the power piston and displacer. Everything else I’ve been designing as I go (which may not have been a good idea).

I’ve posted a few pics below. With the air valve removed (3rd picture below, knurled brass knob on underside of base plate), the motor turns over quite easily and smoothly. I’m trying to figure out how to post a video of this....it will turn over easily 15-20 times and then gently rocks back and forth to a stop. I’ve used ball bearings everywhere except for the connection of the power piston rod to the power piston itself.

The problem is, I can’t get the thing to run on it’s own...even with a blow torch.

I’ve checked the displacer side for air tightness using a rubber hose and a bucket of water. Seemed ok.

I’m wondering if my problem is one of the following:

A. Too much weight on the yoke for the displacer rod. The original plans called for some crafty milling of an aluminum yoke, which I don’t think I can do. I thus milled the brass/3mm stainless rod yoke combo shown in the pictures. It’s likely to be heavier than what the plans call for. I’m Not sure if this is the problem, however, since I also built another de Waal engine (http://www.vapeuretmodelesavapeur.com/telechargements4/s-stirling-vertical-05-01-02.pdf and picture 6 below), and it runs great despite the smaller dimensions of the power and displacer pistons and the relatively heavy (brass) yoke on the displacer rod in that machine.

B. Too much weight on the spinning axis (crankshaft). I have removed the counterweights on the crankshaft in photos 1 and 2 and replaced them with simple brass arms (5th picture), but I think this step actually made the problem worse.

C. Not enough weight on the spinning axis (crankshaft). In Photo 4 below, I’ve added four long spokes to the flywheel, each with weights on the end. The flywheel itself is solid steel. It turns true. With the longer spokes, it will turn over at least 30 times with a good spin by hand (and air plug removed). (Again, trying to figure out video...)

D. Too much heat getting to the power piston. I added 0.4mm gaskets under both pistons and the base plate, and a 1mm gasket between the displacer cylinder and (under) the base plate. The base plate is 12mm thick Aluminium, which can hold a lot of heat, while the de Waal plans called for a 4mm thick piece. I really hope this is not the problem because replacing the base plate will not be easy...and will mess with the overall design since the shaft for the flywheel assembly bolts into both the baseplate and the top plate (also 12mm Alu).

E. Not enough air getting to the top of the power piston. In the original plans, the top of the power piston is open. I added the brass top with the small slit cut in for the power piston rod (photo 2) since I thought it would look better. I can,t imagine why this could cause a problem, but....what do I know?

F. Dead space in the displacer cylinder. Yeah, there is a out 8-9 mm of dead space, the result of my modifications from the plans. I made the displacer piston relatively early, and it is a bit short.

G, Demons. The machine is simply possessed and I need the services of a wizard to exorcise the evil that lives inside it.

Any thoughts on this project would be greatly appreciated!

Q: Are there any guidelines on “balance”? For example, should the counterweights on the crankshaft be heavy enough so that, when at rest, the displacer piston is actually raised (ie pulled up by the weight of the counterweights)? In the other vertical Stirling I built (link above and pic 6 below), the displacer is still heavier than the counterweight, so at rest the displacer is at its lowest position.

Q: the plans in the kyko have the same diameter for both the displacer and the power piston cylinders. The moriya fan does not. Is this a problem for the kyko? Most other plans I’ve seen for vertical Stirling have smaller diameter power pistons.

Q: To address the dead space in the displacer piston (point F above), I am thinking about making the crankshaft arms longer. Plans call for a 28mm travel for the power piston, and a 38mm travel for the displacer. What if this were 28mm power piston travel and 46mm displacer piston travel? This would solve the dead space problem, but I’m not sure if the travel distances should be that different.

Thanks in advance for your time!
PMM

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minh-thanh

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Hi Pmcguire !
" F. Dead space in the displacer cylinder. Yeah, there is a out 8-9 mm of dead space, the result of my modifications from the plans. I made the displacer piston relatively early, and it is a bit short. "

Clearance of displacer, front and rear, about 1 mm

" Q: the plans in the kyko have the same diameter for both the displacer and the power piston cylinders. The moriya fan does not. Is this a problem for the kyko? Most other plans I’ve seen for vertical Stirling have smaller diameter power pistons."

With Gamma stirling
Same diameter for both the displacer and the power piston cylinders : BUT the stroke of power piston will be much shorter

" Q: To address the dead space in the displacer piston (point F above), I am thinking about making the crankshaft arms longer. Plans call for a 28mm travel for the power piston, and a 38mm travel for the displacer. What if this were 28mm power piston travel and 46mm displacer piston travel? This would solve the dead space problem, but I’m not sure if the travel distances should be that different."

Increasing the stroke 4 mm will increase the volume of gas that the diaplacer converts (I'm not an expert so I don't know how much it is, just my experience) Why not make a new displacer ?

I have a question : your engine , how much is the diameter of the power piston?
 
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Pmcguire

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Minh-Thanh,

Thanks for your reply, and for your tips.

On your questions:

1. Why not make a new displacer?

Answer: I will probably end up doing just that. But I found the aluminum soldering to be quite difficult so was trying to avoid that. I would also need to order some more aluminum tube. Before I go down that route, I thought I might try to put a brass filler piece inside the displacer cylinder at the top. It need not touch the displacer piston rod, and it would occupy the dead space. I think I can turn it to the exact diameter of the displacer cylinder but with a small lip on the top. I Would then need to cut a small rim around the top of the displacer cylinder from which it will “hang”. Views on this?

2. What is the diameter of the displacer and power pistons?

Answer: 38mm.

Thanks again for your time on this. Any other thoughts are much appreciated!

PMM
 

fcheslop

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Dead space is very bad for these engines as is friction and air leaks
What is the hot cap made from ?
Calculate the ratio
Jan Ridders site has a good write up on basic design
Iv looked at those drawings many times but find them hard to follow so never got round to building it
cheers
 

minh-thanh

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1. Why not make a new displacer?

Answer: I will probably end up doing just that. But I found the aluminum soldering to be quite difficult so was trying to avoid that. I would also need to order some more aluminum tube. Before I go down that route, I thought I might try to put a brass filler piece inside the displacer cylinder at the top. It need not touch the displacer piston rod, and it would occupy the dead space. I think I can turn it to the exact diameter of the displacer cylinder but with a small lip on the top. I Would then need to cut a small rim around the top of the displacer cylinder from which it will “hang”. Views on this?

PMM
My opinion, keep the proportions according to the drawing board !
 

Pmcguire

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Dead space is very bad for these engines as is friction and air leaks
What is the hot cap made from ?
Calculate the ratio
Jan Ridders site has a good write up on basic design
Iv looked at those drawings many times but find them hard to follow so never got round to building it
cheers
Thanks for the tip. I’ll check out the Jan Ridders site for the ratios. To answer your question, the hot cap and the displacer cylinder are both made from brass.

Thanks,
PMM
 

Pmcguire

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My opinion, keep the proportions according to the drawing board !
Indeed, probably good advice.

My only worry is that I’ve never seen a video or pics online of someone that actually built this engine. There are many videos of the Moriya Stirling Fan, but not of the Kyko fan. If you or others have seen any, please let me know. I would love to see a build log.

Thanks again,
PMM
 

fcheslop

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Hi , Brass is a poor choice for the hot cap as it will conduct a lot of the heat into the engines frame .Stainless or glass is far better
When I make the hot caps they are machined from stainless tube to about 25 thou thick and then hard solder a copper or bronze cap again around 25 thou thick.
A heat dam can be machined at or near the mounting flange its just a simple thinner section a few mm wide the idea is that the air cools better and helps reduce the heat going further up and into the engines frame
The displacors are made from alloy and the end press fitted or glued with loctite and some times a very small air hole drilled to prevent pressure building up in them usually if they are also made from glass. Stainless is another good choice and brass would be my last
Iv not seen any engines built from those drawings and as already mentioned I find all his drawings confusing. My first step would be to calc the ratio just to see if its a goer or not if not then adjust the power piston or displacor size to bring it into spec.
Moriya was my first Stirling engine and was a great runner from the very start and ran for 20 plus years and is still going with a new owner
The first engine you show was not designed by Mr Dewaal and a proven design before he did his drawings from the originals the gentlemans name escapes me at the moment.
I like the look of the Kyko and will probably build it oneday just not yet to many other builds on the go and just finishing a long term build of the 2inch bore Rider Ericsson that now runs from one 8mm wick fired by meths
cheers
frazer
 

fcheslop

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To calc the ratio
Vp= bore x stroke Power Piston
Vd=bore x stroke of displacer
Vs=Vp +Vd this is system volume
to calc ratio
R=Vs/Vp
Vp=38x14=532
Vd=36x19=684
R=532+684/532=2.28
So if my poor maths is correct the ratio should work but again this simple formula does not take into account dead space and passage way losses
Iv used this simple calc and not had a non runner yet
The gentleman's name of the first engine I think is Jos de Vink a very imaginative builder and Iv attached a link to his you tube thingy ma bob
Hope that helps
 
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minh-thanh

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fcheslop !
Thanks for the simple formula and great video !

Pmcguire !
Unfortunately I don't know much about it
Hope you will get it run
And your engine is very beautiful.
 

fcheslop

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MinhThanh, you are most welcome
This fan has got my interest just need a rummage to see what materials I have well after another Cracker is finished
Keep well
regards
frazer
 

Pmcguire

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All,

Many thanks to all above for the comments and suggestions. I’m happy to inform you that today, I got the machine to run! I re-made the power piston, for a better fit. Once I put the new one in, it worked! Still required a blowtorch, but at least I know I’m on the right track.

Will post some pics once I do some cleanup work.
PMM
 

Pmcguire

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To calc the ratio
Vp= bore x stroke Power Piston
Vd=bore x stroke of displacer
Vs=Vp +Vd this is system volume
to calc ratio
R=Vs/Vp
Vp=38x14=532
Vd=36x19=684
R=532+684/532=2.28
So if my poor maths is correct the ratio should work but again this simple formula does not take into account dead space and passage way losses
Iv used this simple calc and not had a non runner yet
The gentleman's name of the first engine I think is Jos de Vink a very imaginative builder and Iv attached a link to his you tube thingy ma bob
Hope that helps

Many thanks for this! I got the machine to run.
 

Pmcguire

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All, some photos below of the polished engine. Runs on butane. Thanks again for all the advice above. Only step left is to make a thick walnut base (currently just a scrap board painted blue).
PMM
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davidyat

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A subject close to my heart. I "learned" that I'm not good at hot air engines. Tried the Meyers 1/4 scale Hot Air Engine. Absolutely couldn't get it to run and now I have a fantastic paper weight for my office desk.
Grasshopper
 

ShopShoe

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Fantastic.

I'm getting sympathetically tired just thinking about all the time it must have taken to polish all those parts. But I think it was well worth it in the result.

Thank You for Posting

--ShopShoe
 
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