584,866 active members*
5,036 visitors online*
Register for free
Login
IndustryArena Forum > Hobby Projects > I.C. Engines > 2-stroke ported OPOC engine (125cc x 2)
Page 2 of 3 123
Results 21 to 40 of 57
  1. #21
    Join Date
    Dec 2005
    Posts
    591
    If you're talking ringed pistons, the bore is straight. Non-ringed 2 stroke engines, like the R/C engines mentioned above, do have tapered cylinders.

    Mark

  2. #22
    Join Date
    Jan 2007
    Posts
    76
    Yes, agree.
    To be fair though, he did not say ringed, just he never encounted a tapered bore.

  3. #23
    Join Date
    Jan 2010
    Posts
    485
    Quote Originally Posted by bluejets View Post
    Yes, agree.
    To be fair though, he did not say ringed, just he never encounted a tapered bore.
    If you mean me, I was responding to the OPs engine. Don't think a 125cc cylinder would count as a RC engine. And it has been stated that it has rings.

  4. #24
    Join Date
    Jan 2007
    Posts
    76
    Quote Originally Posted by packrat View Post
    If you mean me, I was responding to the OPs engine. Don't think a 125cc cylinder would count as a RC engine. And it has been stated that it has rings.

    Some of the first drone aircraft used 250cc engines and they were R/C.

  5. #25
    Join Date
    Dec 2005
    Posts
    591
    Quote Originally Posted by packrat View Post
    If you mean me, I was responding to the OPs engine. Don't think a 125cc cylinder would count as a RC engine. And it has been stated that it has rings.
    Wanna bet?

    TowerHobbies.com | DLEDLE-170 DLE-170 DLE Engines DLE-170cc Twin Gas Engine

    TowerHobbies.com | DLEDLE-222 DLE-222 DLE Engines DLE-222cc 4-Cylinder Gas Engine



    Mark

  6. #26
    Join Date
    Mar 2006
    Posts
    2712
    The replacement parts list for the 170 lists piston rings. I didn't see a replacement parts list for the 220.

    Dick Z
    DZASTR

  7. #27
    Join Date
    Dec 2005
    Posts
    591
    Yep, it has rings. I was responding to your statement that you didn't think a 125 cc cylinder would count as an RC engine. ;-)

    Mark

  8. #28
    Join Date
    Mar 2006
    Posts
    2712
    That was packrat, not me.LOL

    Dick Z
    DZASTR

  9. #29
    Join Date
    Dec 2005
    Posts
    591
    Crap. I need to keep my reply-to's under a little closer observation.

    Mark

  10. #30
    Join Date
    Jan 2010
    Posts
    485
    And the examples aren't the same. The OP is making a 250cc motor - 125cc per cylinder. Thats dirt bike territory! Definitely needs rings for the compression he wants too.

  11. #31
    Join Date
    Jul 2012
    Posts
    0
    Quote Originally Posted by UUU View Post
    Glands where a piston rod passes through the end of a cylider are not common in IC engine designs - but they are well used in steam engines. If you can look up pictures for designs for these you'll see they often have an o-ring seal or some twists of graphited yarn as the packing.

    Thor detail of piston road and gland | Flickr - Photo Sharing!

    http://www.co2.pwp.blueyonder.co.uk/...ics/glands.jpg

    Pump Packing Installation
    oo, that's really valuable advice, saves me some searching and research for options. thank you.

    You'll see in the picures there's a clamp to tighten up the packing. Some designs have a threaded ring to do the job. Your pressures are quite low so you may get away with the shaft just passing through a cloesly fitting tube.
    sleeve bearing. yes. although, i heard recently that up until 20 years ago jaguar were still using oil-impregnated leather as bearings (just like bourke did). in this case you actually _want_ a drip-feed of oil through the bearing.

    Although you're really inviting suggestions for making your design, and not on the design itself, I'd have to say that the cam arrangement is not going to be at all easy. Perhaps you could look at this side rod steam engine, and imagine an extra cylinder on the right.

    'SIDE ROD' TABLE ENGINE - Brunell Steam Model Engineering

    The two cylinders would be connected by a common piston rod, and the side-rods take the back-and-forth motion off to a crank and flywheels. This would be a lot easier to make.
    yees, but although the cam itself is tricky as hell and will need very accurate CNC machining, the cam arrangement is essential to the simplicity of the _rest_ of the design, as well as the long life, etc. etc. and the cams *are* the flywheel. cranks have been done before: i want to try something that hasn't!

    thanks uuu.

  12. #32
    Join Date
    Jul 2012
    Posts
    0
    Quote Originally Posted by packrat View Post
    And the examples aren't the same. The OP is making a 250cc motor - 125cc per cylinder. Thats dirt bike territory! Definitely needs rings for the compression he wants too.
    allo mr packrat,

    apologies first, to you (and all!) - i didn't realise this was an ongoing discussion, cnczone hadn't sent me a message in a while!

    ok, i've been doing a bit more research and a bit more thinking: i'm still going to go with the 250cc total, but.... as a 6-cylinder arrangement (!) in 3 double-opposed pairs, each offset at 60 degrees, all on the same cams. i will however start with only two! the reason for 6 is because a) they'll fit b) 3 sets are perrrfectly counter-balanced: absolutely zero vibration.

    so ho hum, 250 divided by 6 is 42 (ish), that comes out at about a 37mm bore (or so) and a 40mm stroke (or so). approximately this, in fact: TowerHobbies.com | DLEDLE-55 DLE-55 DLE Engines DLE-55cc Gas Engine

    hmm, that's aluminium. i wonnderrrrr... if i could get away with re-using those cylinder heads - and pistons, save me some machining, hmmmm....

    and hell yes definitely rings. higher compression, much *much* leaner mixture to compensate.

  13. #33
    Join Date
    Jul 2012
    Posts
    0
    oo good find, mark. that lead me to some 55cc DLE engines which are close to what i need, i could consider buying those off-the-shelf instead and their pistons, save me making them. do you - or anyone else for that matter - happen to know of any other model RC engines, preferably 2-stroke with glow-plugs, in the 30 to 55 cc range, that use rings? using ready-machined matching parts like these would make the remainder of the engine a much easier proposition that i would be much more comfortable with.

    /peace.

    l.

  14. #34
    Join Date
    Jul 2012
    Posts
    0
    Quote Originally Posted by wendtmk View Post
    If you're talking ringed pistons, the bore is straight. Non-ringed 2 stroke engines, like the R/C engines mentioned above, do have tapered cylinders.

    Mark
    i'd heard about piston rings that are angled so that when it all goes "bang" the pressures push them harder against the side-wall. the tapered cylinders (no rings) had me pause for a second though. don't believe i need that (whew).

    l.

  15. #35
    Join Date
    Mar 2006
    Posts
    2712
    ikcl, you might "google" Dykes rings. They have an "L" cross section and do an excellent job of sealing. They are placed near the top of the piston reducing the area of "blow by".

    Dykes rings were regularly used in the rotary valved Rotax engines. Some use a single 1mm ring for higher rpm, less ring "flutter".

    Dick Z
    DZASTR

  16. #36
    Join Date
    Jul 2012
    Posts
    0
    Quote Originally Posted by RICHARD ZASTROW View Post
    ikcl, you might "google" Dykes rings. They have an "L" cross section and do an excellent job of sealing. They are placed near the top of the piston reducing the area of "blow by".
    Dick Z
    star, richard. really appreciate the pointer.

  17. #37
    Join Date
    Jul 2012
    Posts
    0
    ok, uuu: i liked the idea of finding a pre-existing motorbike engine so much that i went "hmm, what about 50cc scooter 2-stroke engines?" and well that led me to look on ebay and i accidentally wandered across a polish company that makes "big bore cylinder kits" for £32 + £15 shipping, each.

    well, now, i don't know about you, but i think i would be a bit of a jack-ass to go doing all the work of making something that's near-identical to what i can get from poland for £47, don't you?

    although it feels like cheating, i'm all for tackling one thing at a time. so i found a CNC shop that's happy to make the cams for me, he found it hilarious that i sent him a kid's-style picture originally. also i think he thought i must be mad, or something, and i could tell he was thinking "this is money for old rope, here, i ain't complaining if this guy pays me to do something nuts!". i've since beefed up operations and written the computer program that generated this:

    http://lkcl.net/engine/trilobe.png

    surprisingly it only took me a couple of hours. it's a horrible algorithm, order n-cubed, because i couldn't work out the maths. the bearings that roll along the surface of the cam, you can't just use a sine-wave cam surface because the point at which the bearings meet the surface as it's going up and down is *not* on the line between the centres of rotation. argh. so rather than do some maths equations i just tested all possible rotational combinations, hence the truly dreadful algorithm.

    eyy, it only took about 2 minutes to run, what am i complaining about?

  18. #38
    Join Date
    Jul 2012
    Posts
    0
    btw, i thought this might be worth sharing, for sheer mind-boggling hilarity. i can't quite get over the numbers, here.

    even assuming there's no performance gain from this rather strange design: if i use 6 of these big-bore 70cc kits to create a 420cc engine, there are people out there who have done race-tuned versions of *single*-cylinder 70cc setups that are getting 23HP and above:

    70cc sport vs full race

    some straightfoward maths: six times 23 is 138HP. off of a 420cc engine! mind you that's at 15,000 RPM but even so that's just hilarious. and completely insane.

  19. #39
    Join Date
    Jan 2010
    Posts
    485
    Do you know about this site? Welcome To BourkeEngine.Com Or this one? BOURKE ENGINE

    A lot of detail stuff in them if you study what their saying and showing.

  20. #40
    Join Date
    Jul 2012
    Posts
    0
    Quote Originally Posted by packrat View Post
    Do you know about this site? Welcome To BourkeEngine.Com Or this one? BOURKE ENGINE

    A lot of detail stuff in them if you study what their saying and showing.
    yes i do. i found that stuff about... 8 months ago, and have moved on from there

    word of warning: the guy behind the bourkeengine.com web site has some psychiatric problems, as you can probably tell from the over-abundance of exclamation-marks, but i didn't take note of that tell-tale sign at the time. his interactions with me were incredibly rude: he was overjoyed to capitalise on a misunderstanding, such that he concluded that i must be some sort of fraudulent scammer wishing to defraud him. every apology i gave he continued to use as evidence of "continued fraudulent activity" and his responses became ever-more frantically jubilant and down-right nasty. i could tell he was "having fun hurting the scammer, let's treat him like s**t har har, oh yesss, i made this stupid f*****g scammer look like the total fool he is, har har, what a stupid thief he must be to think he can use apologies to get me to believe him", whereas in fact he was only hurting himself. and letting down the enormous responsibility of bringing the bourke engine design out of obscurity.

    bottom line: stay the f*** away from him. he wants to be in control, and he has paranoid behavioural disorders. and he's incredibly rude. i got so alarmed by his behaviour that i've had to place a block on his email address.

    by contrast, roger richards however looks to be a very genuine, interesting and skilled guy, albeit also probably very busy as well as reclusive. he hasn't responded to emails, and i am reluctant to call him over an international phone call "hi you don't know me from jack or adam, but i'm interested in your work on the bourke engine"...

    also, you may be aware of someone who worked with Bourke: he went on to make something called the "Vaux" Engine. bourke's opinion of Martin Vaux's work was that it was a step in the wrong direction, and that it actually introduced flaws and inefficiencies. however, i tracked down a guy who has made it his responsibility to bring the Vaux Engine out of obscurity. i had an initial discussion with him, then i made him an offer to present his design to some investment opportunities i knew of, and i didn't hear from him again.

    so this is why i'm here, because i've been through the options, on these kinds of innovative "non-otto, non-wankel, non-sterling" engine designs, and all the people working on them have some extremely weird s**t going on. and so, as i've run out of options, i'm tackling it myself.

    so what i did was get a copy of "The Bourke Documentary" (there are a few copies available on amazon), studied it, and updated the wikipedia page on the bourke engine. naturally, people wanted to argue the s**t out of how the design could not possible work, including trying to tell me that a crank must have a longer dwell time at TDC than a sine wave, because some morons on wikipedia had done a "thorough engineering review" at some point a few years ago without access to Bourke's notes, and consequently made dozens of basic chemistry and mechanical design mistakes. exactly as everyone else in the world who, out of very sad ignorance, truly believes that the Otto Cycle Engine is The One True Path.

    after reading the book comprehensively enough to deal with the antagonistic approach of the morons on wikipedia, a switch went off in my head one morning and i went, "i know how this engine works now: i don't have to put up with this s**t!" - so i just terminated editing the page and haven't really looked at it since (because i don't need to).

    so, yes: i've been studying this design for some considerable time, and am aware that as-is, the bourke design has some design flaws. not as many as in an otto cycle engine, it has to be said, but that doesn't help when there's been so much research and development been put into otto cycle engines to try and compensate for those flaws, whereas there has been virtually zero development of the bourke design since it was first released.

    for example, a scotch yoke, although it provides lateral motion, doesn't completely eliminate side-loading (esp. at 90 degrees to TDC and BDC). in 1974 someone submitted a U.S. patent to cater for both wear in the yoke and the hole in the chamber that the piston rod goes through. but that patent is really just a band-aid, hence the reason why i want to try something different.

    also there are problems just as in any 2-stroke ported engine which relies on the piston skirts being spring-loaded against the cylinder side-wall in order for them to act as effective port gates. the problem is: the piston skirts are spring-loaded against the cylinder side-wall! duh. so i am looking at ways to deal with that, given that the entire piston and rod assembly can be effectively a single piece. but i'll get to that in good time. first thing is to get at least some semblance of a working engine.

    /peace.

    l.

Page 2 of 3 123

Similar Threads

  1. Two Stroke Engine Design
    By PVO in forum Mechanical Calculations/Engineering Design
    Replies: 9
    Last Post: 05-22-2012, 05:05 PM
  2. two stroke engine
    By PoWaKiD42 in forum I.C. Engines
    Replies: 50
    Last Post: 10-03-2007, 06:59 AM
  3. 2 stroke engine
    By superrotary in forum I.C. Engines
    Replies: 2
    Last Post: 09-27-2007, 09:03 PM
  4. Anyone build a 4-stroke I.C engine?
    By cncadmin in forum I.C. Engines
    Replies: 6
    Last Post: 03-14-2004, 09:55 PM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •