There are many reasons....but in my case I had to return the tool to standard settings - and a sharp cutting tool. At least when the tool is set up correctly and when it doesn't solve the problem then I look for another cause
And here :
Mastiff lc mason engine REDO .
- Thread starter minh-thanh
- Start date
Help Support Home Model Engine Machinist Forum:
And here :
Hi All !
An update :
I'm making pistons
One thing I hate the most is centering and drilling the hole for the shaft, so I made a part to do that, as well as making a part to clamp the piston for internal machining.
With a test..., Everything went according to plan
An update :
I'm making pistons
One thing I hate the most is centering and drilling the hole for the shaft, so I made a part to do that, as well as making a part to clamp the piston for internal machining.
With a test..., Everything went according to plan
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Hi All !
An update :
Pistons : done
Next: Making connecting rods
An update :
Pistons : done
Next: Making connecting rods
Jens Eirik Skogstad
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Minh-Thanh
Make pistons a bit tapered. The diameter on the piston crown need to be less than main diameter of the piston measured from mid of the piston.
I had the piston stuck in the cylinder due heat of expansion. Then I took a bit less material from piston crown (ring zone) calculated by heat of expansion coefficient for aluminium in 200-250 degree maximum.
The taper shape compensates for thermal expansion and thermal growth. Thermal growth is the increase in size of a material when heated, with little or no change back to original dimensions. The taper design allows the piston to move freely in the cylinder bore regardless of the heat applied to the piston head.
Make pistons a bit tapered. The diameter on the piston crown need to be less than main diameter of the piston measured from mid of the piston.
I had the piston stuck in the cylinder due heat of expansion. Then I took a bit less material from piston crown (ring zone) calculated by heat of expansion coefficient for aluminium in 200-250 degree maximum.
The taper shape compensates for thermal expansion and thermal growth. Thermal growth is the increase in size of a material when heated, with little or no change back to original dimensions. The taper design allows the piston to move freely in the cylinder bore regardless of the heat applied to the piston head.
Don't advise me to make pistons like that !!!
I did: straight cylinder + straight piston (not 100% accurate but It good enough). Taper cylinder, straight piston, straight cylinder + taper piston: and they always have good compression and run well
About thermal expansion: I will calculate like him
, or I will do it my way
I did: straight cylinder + straight piston (not 100% accurate but It good enough). Taper cylinder, straight piston, straight cylinder + taper piston: and they always have good compression and run well
About thermal expansion: I will calculate like him
, or I will do it my way
Hi All !
An update :
The connecting rods are finished, they will need to be made beautiful, assembled to check the length .... : ok
Next : Rings
An update :
The connecting rods are finished, they will need to be made beautiful, assembled to check the length .... : ok
Next : Rings
Hi All !
An update :
Two of my friends suggested I make oil rings
I took a faulty piston for testing
I made 4 oil rings for testing
Maybe I'll sharpen a cutter 0.6mm thickness and drill a 0.5mm hole
And perhaps make a part for more precise drilling for pistons and rings
....
Thinking....
An update :
Two of my friends suggested I make oil rings
I took a faulty piston for testing
I made 4 oil rings for testing
Maybe I'll sharpen a cutter 0.6mm thickness and drill a 0.5mm hole
And perhaps make a part for more precise drilling for pistons and rings
....
Thinking....
Well done Minh Thanh!
Of course, one of the problems of Home-made rings is simply the precision possible with limited costs, tooling, etc.
Commercially made rings have a top part of the oil control ring slightly tapered, to present a sharp edge to the down-ward stroke of the piston, and similar but opposite taper of the lower scraping land to permit oil to pass the ring on the downward stroke and be wiped through the drain holes. But that taper is probably only 1~3 microns deep across the wiping face. In fact the bottom wiping face may be just a couple of microns smaller diameter that the top wiping face to aid oil collection and wiping.
These shapes are impossible to replicate on "regular hobby lathes", etc.
Also for compression rings, there are tapers, curved surfaces, etc. and fewer microns of clearance to ring grooves than we can achieve with Hobby tooling. - Never mind making rings out-of-round, to adjust the "end effect" of the change of tangential load to achieve a constant tangential load where there are the ring gaps... (the last 30 degrees or so of ring act like a bending cantilever beam, whereas the "middle" 300 degrees acts like a beam stiffly supported at both ends).
Can you buy rings from someone like "Perfect Circle" of USA?
I realise that it is sometimes a bit like cheating to buy precision components, but in the interest of a better engine, it may be the practical solution?
K2
Of course, one of the problems of Home-made rings is simply the precision possible with limited costs, tooling, etc.
Commercially made rings have a top part of the oil control ring slightly tapered, to present a sharp edge to the down-ward stroke of the piston, and similar but opposite taper of the lower scraping land to permit oil to pass the ring on the downward stroke and be wiped through the drain holes. But that taper is probably only 1~3 microns deep across the wiping face. In fact the bottom wiping face may be just a couple of microns smaller diameter that the top wiping face to aid oil collection and wiping.
These shapes are impossible to replicate on "regular hobby lathes", etc.
Also for compression rings, there are tapers, curved surfaces, etc. and fewer microns of clearance to ring grooves than we can achieve with Hobby tooling. - Never mind making rings out-of-round, to adjust the "end effect" of the change of tangential load to achieve a constant tangential load where there are the ring gaps... (the last 30 degrees or so of ring act like a bending cantilever beam, whereas the "middle" 300 degrees acts like a beam stiffly supported at both ends).
Can you buy rings from someone like "Perfect Circle" of USA?
I realise that it is sometimes a bit like cheating to buy precision components, but in the interest of a better engine, it may be the practical solution?
K2
Jens Eirik Skogstad
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As Steamchick mentioned how the oil scraper ring has these forms of oil scraper to keep oil back to crankcase. See this link.. https://www.anglo-agriparts.com/tractor-tech-articles/piston-ring-types-oil-control-rings
The purpose of my oil ring:
I just tried to remove the vacuum area created between : piston + cylinder + rings - as shown in the picture
Once that is resolved, the oil sucked up by that vacuum is removed
2 - The oil ring has the effect of removing remaining oil and giving the oil a way to escape
Preliminary conclusion: I don't know how effective it is.
Just a suggestion from two friend on Facebook, and I think it's interesting to try, but there's a lot to do
K2 !
"Can you buy rings from someone like "Perfect Circle" of USA?"
Do they sell rings with 19.5mm diameter?
I just tried to remove the vacuum area created between : piston + cylinder + rings - as shown in the picture
Once that is resolved, the oil sucked up by that vacuum is removed
2 - The oil ring has the effect of removing remaining oil and giving the oil a way to escape
Preliminary conclusion: I don't know how effective it is.
Just a suggestion from two friend on Facebook, and I think it's interesting to try, but there's a lot to do
K2 !
"Can you buy rings from someone like "Perfect Circle" of USA?"
Do they sell rings with 19.5mm diameter?
Jens Eirik Skogstad
Member
- Joined
- May 27, 2023
- Messages
- 24
- Reaction score
- 25
Translate to your language and read here, he had trouble with oil leakage before he added oil ring in his Cirrus engine..
Worth to know..
http://modelicengine.la.coocan.jp/c06041.htm
Worth to know..
http://modelicengine.la.coocan.jp/c06041.htm
Jens Eirik Skogstad
Member
- Joined
- May 27, 2023
- Messages
- 24
- Reaction score
- 25
Sorry, I last dealt in pistons (including with Mahle) and rings (Hepworth and Grandage) back in 1990... so I am out-of-date. And technology will have moved-on from my knowledge as well.
I was really trying to emphasize what a difficult task you have set yourself, and if oil is a real problem maybe it needs a radical solution if even home-made rings fail to achieve the task.
When the H & G Chief Engineer told me the most technical ring makers were Perfect Circle... - so everyone followed their lead - I thought it may be a suggestion worth following-up.
Sorry if no use to you. I was simply offering advice from "my knowledge".
K2
I was really trying to emphasize what a difficult task you have set yourself, and if oil is a real problem maybe it needs a radical solution if even home-made rings fail to achieve the task.
When the H & G Chief Engineer told me the most technical ring makers were Perfect Circle... - so everyone followed their lead - I thought it may be a suggestion worth following-up.
Sorry if no use to you. I was simply offering advice from "my knowledge".
K2
Minh Thanh,
I also believe you are truing to compensate for "scale" as well as manufacturing capability.
As diameter changes, the area changes as a square factor, yet the volume of oil per mm of stroke changes as the linear diameter (you can't get thinner than a molecule of oil so volume of oil relates to length of circumference). So relatively, the 1cc engine is trying to cope with 10 x the oil of the 100cc engine... of the same stroke. (If my maths is right?).
I suggest a ring of holes at the top of the skirt, just below the oil scraper ring, may also be advantageous to your oil clearing issue?
One other "whim" of technology... the Tangential load of the ring does 2 things. It provides the pressure to press metal against the oil film, in order to minimise the film and remove excess. It also can penetrate the oil film to a metal-to-metal contact - which is disastrous and to be avoided. Higher Tan load = higher friction, so to develop the correct pressure of ring on oil film the area of ring metal at the surface is reduced so rings work effectively at lower Tan loads. That's (partly) how scraper rings try to work, because the gas pressure from combustion chamber is not assisting the Tan load, (which it does on the compression rings). The ends of the rings towards the gap have less tan load than opposite the gap, so there are compromises. That's as far as my brief training of rings went, so you'll have to research ring free oversizes to develop appropriate tan loads on the contact widths you are achieving.
Simple scaling doesn't always work as not everything is linear with scale...
The photos appear to show some chipping of edges, as maybe you are using cast iron to make rings? - Or it may be just the photographic appearance? Have you considered steel rings? - Or bronze?
K2
I also believe you are truing to compensate for "scale" as well as manufacturing capability.
As diameter changes, the area changes as a square factor, yet the volume of oil per mm of stroke changes as the linear diameter (you can't get thinner than a molecule of oil so volume of oil relates to length of circumference). So relatively, the 1cc engine is trying to cope with 10 x the oil of the 100cc engine... of the same stroke. (If my maths is right?).
I suggest a ring of holes at the top of the skirt, just below the oil scraper ring, may also be advantageous to your oil clearing issue?
One other "whim" of technology... the Tangential load of the ring does 2 things. It provides the pressure to press metal against the oil film, in order to minimise the film and remove excess. It also can penetrate the oil film to a metal-to-metal contact - which is disastrous and to be avoided. Higher Tan load = higher friction, so to develop the correct pressure of ring on oil film the area of ring metal at the surface is reduced so rings work effectively at lower Tan loads. That's (partly) how scraper rings try to work, because the gas pressure from combustion chamber is not assisting the Tan load, (which it does on the compression rings). The ends of the rings towards the gap have less tan load than opposite the gap, so there are compromises. That's as far as my brief training of rings went, so you'll have to research ring free oversizes to develop appropriate tan loads on the contact widths you are achieving.
Simple scaling doesn't always work as not everything is linear with scale...
The photos appear to show some chipping of edges, as maybe you are using cast iron to make rings? - Or it may be just the photographic appearance? Have you considered steel rings? - Or bronze?
K2
Minh: Have you asked anyone like this about supplying rings of your sizes? (The offer "10mm plus"... and "custom parts"?)
https://www.thn.nl/en/product-line/...CpLKQeXxWwwS0VCMXiAtJlYdQq_XCrKxoCvHMQAvD_BwE
I am sure you will find the solution, but sometimes the technical task is simply beyond "home machining" capability.
- Or so I find...
K2
https://www.thn.nl/en/product-line/...CpLKQeXxWwwS0VCMXiAtJlYdQq_XCrKxoCvHMQAvD_BwE
I am sure you will find the solution, but sometimes the technical task is simply beyond "home machining" capability.
- Or so I find...
K2
Hi K2
About the piston and rings: The piston is defective, the ring is just a test to see what I can do so I don't care about its surface...
find a way to cut it, drill holes.....
Actually this engine only has one ring as designed, I try to make 2 rings, and maybe a 3rd ring : oil ring
Commercial rings: I would buy and measure it before I design a engine
Custom rings: I don't think a company will only produce a few dozen or a few hundred rings for me, and even if they did, the price would be very high - and that's not my choice.
Personally, I like to do everything. Even if the effectiveness is only a few dozen percent compared to a commercial ring, that's still a success.
About the piston and rings: The piston is defective, the ring is just a test to see what I can do so I don't care about its surface...
find a way to cut it, drill holes.....
Actually this engine only has one ring as designed, I try to make 2 rings, and maybe a 3rd ring : oil ring
Commercial rings: I would buy and measure it before I design a engine
Custom rings: I don't think a company will only produce a few dozen or a few hundred rings for me, and even if they did, the price would be very high - and that's not my choice.
Personally, I like to do everything. Even if the effectiveness is only a few dozen percent compared to a commercial ring, that's still a success.
I understand why you are doing it your way. Not a problem...
What I don't understand is the calculations for piston ring Tan load, how to select steel, or cast iron, etc. per ring application, ring contact pressure versus expanded/compressed diameter, and a host of other things, and you are a better machinist than I as well?
I do have a notion (from the little training I had!). that compression rings need relatively low contact pressure from the spring (compression) of the rings, as the main forces come from the compression and firing gas pressures that are seen on the inner diameter of the rings. The "larger" surface area of ring contact (I.E. ring thickness) - compared to oil control rings - is designed to ensure the rings do not break the oil film at max ring tan load at max cylinder pressure.
Oil rings are designed with a higher contact pressure to actually break the oil film while scaping, and all from spring forces, not gas forces. Hence the very narrow contact width.
But you know all that I think?
K2
What I don't understand is the calculations for piston ring Tan load, how to select steel, or cast iron, etc. per ring application, ring contact pressure versus expanded/compressed diameter, and a host of other things, and you are a better machinist than I as well?
I do have a notion (from the little training I had!). that compression rings need relatively low contact pressure from the spring (compression) of the rings, as the main forces come from the compression and firing gas pressures that are seen on the inner diameter of the rings. The "larger" surface area of ring contact (I.E. ring thickness) - compared to oil control rings - is designed to ensure the rings do not break the oil film at max ring tan load at max cylinder pressure.
Oil rings are designed with a higher contact pressure to actually break the oil film while scaping, and all from spring forces, not gas forces. Hence the very narrow contact width.
But you know all that I think?
K2
Hi K2.
When I design and build an engine it's usually from my experience
With 1 ring I have a lot of space, less with 2 rings and an additional oil ring so I will have to make it according to the remaining size.
Calculating material strength, thermal expansion, torsional load, inertia, stress....and...it's beyond my ability.
Furthermore, assuming I can calculate all of the above, there will be a big problem that I probably cannot solve: where can I find the materials according to the calculated results !!??
NO !
No !
Sorry, I didn't do the math. I use only proven materials for model engines and full-size engines as well: Cast iron. But the cast iron that I use is not good enough as professional full size motor manufacturers but it is good enough for my needs.
Actually when I made engine rings I didn't consider that.
When I design and build an engine it's usually from my experience
With 1 ring I have a lot of space, less with 2 rings and an additional oil ring so I will have to make it according to the remaining size.
Calculating material strength, thermal expansion, torsional load, inertia, stress....and...it's beyond my ability.
Furthermore, assuming I can calculate all of the above, there will be a big problem that I probably cannot solve: where can I find the materials according to the calculated results !!??
OK, we disagree on some things.
I hope I have not upset you, as I admire the way you challenge yourself and achieve results. You DO do a lot of work better than I do, believe me! - I know my failures!
That's why I enjoy your work. I just hope some of what I present is of use? - if not you can tell me to shut-up.
Keep it up.
K2
I hope I have not upset you, as I admire the way you challenge yourself and achieve results. You DO do a lot of work better than I do, believe me! - I know my failures!
That's why I enjoy your work. I just hope some of what I present is of use? - if not you can tell me to shut-up.
Keep it up.
K2
Hi K2....
As I said "I always welcome, like everyone to comment"
I will consider and choose which ideas suit the actual needs and are most suitable for a project...or simply suit what I have on hand.
Sometimes the best opinion and information but it is not suitable for the present with what I have, knowledge, machines, tools... I will note it, maybe in the future I will.. ...
Or those opinions and information will help other members who want to learn
Like your opinion : " I suggest a ring of holes at the top of the skirt, just below the oil scraper ring, may also be advantageous to your oil clearing issue? "
I am considering and thinking...
And thank you !
As you know, with this project, I just complet the unfinished engine. I had to change a few sizes to be able to make another ring and now there will probably be a 3rd ring - an oil ring - and it is much thicker than the other 2 rings. I have to make it the right size for the rest of the piston: I have no other choice
If you have information...about the ring...I'd like to know more, maybe in the future...but not with this project
As I said "I always welcome, like everyone to comment"
I will consider and choose which ideas suit the actual needs and are most suitable for a project...or simply suit what I have on hand.
Sometimes the best opinion and information but it is not suitable for the present with what I have, knowledge, machines, tools... I will note it, maybe in the future I will.. ...
Or those opinions and information will help other members who want to learn
Like your opinion : " I suggest a ring of holes at the top of the skirt, just below the oil scraper ring, may also be advantageous to your oil clearing issue? "
I am considering and thinking...
And thank you !
As you know, with this project, I just complet the unfinished engine. I had to change a few sizes to be able to make another ring and now there will probably be a 3rd ring - an oil ring - and it is much thicker than the other 2 rings. I have to make it the right size for the rest of the piston: I have no other choice
If you have information...about the ring...I'd like to know more, maybe in the future...but not with this project
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