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
:D
Mark
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The replacement parts list for the 170 lists piston rings. I didn't see a replacement parts list for the 220.
Dick Z
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
That was packrat, not me.LOL
Dick Z
Crap. I need to keep my reply-to's under a little closer observation. :D
Mark
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.
oo, that's really valuable advice, saves me some searching and research for options. thank you.
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.Quote:
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.
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!Quote:
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.
thanks uuu.
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.
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.
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