#robotics Logs

Mar 10 2014

00:00 rue_more your just being silly
00:00 GargantuaSauce whaaat
00:00 GargantuaSauce why would a mecha NOT have lasers
00:00 GargantuaSauce jeez
00:01 rue_more its called sparrow1
00:03 rue_more :( I didn't put the project mockup images on the webserver
00:04 rue_more wow, lots happened in 2013
00:10 rue_more oh damn, its been 2 years since I put the scotch-tape patch over the hole in the cab of my truck, I really need to fix that
00:11 rue_more aha
00:11 Jak_o_Shadows Misumi has a $150 discount for companies
00:11 Jak_o_Shadows Can I pretend to be a company?
00:12 rue_more oooh
00:12 rue_more its under robots, not projects, duh
00:12 rue_more http://eds.dyndns.org/~ircjunk/robots/sparrow1/p1040018.jpg
00:12 rue_more thats how big a 12' robot is
00:13 rue_more http://eds.dyndns.org/~ircjunk/robots/sparrow1/dollar.png
00:13 rue_more http://eds.dyndns.org/~ircjunk/robots/sparrow1/p1030340.jpg <-- hehe
00:13 rue_more http://eds.dyndns.org/~ircjunk/robots/sparrow1/p1030901.jpg
00:14 rue_more http://eds.dyndns.org/~ircjunk/robots/sparrow1/p1040015.jpg
00:14 Jak_o_Shadows How was it to move?
00:18 rue_more thats just a mockup duh
00:18 rue_more :) I wanted to see just how big it would be
00:18 rue_more its smaller laying down
00:21 GargantuaSauce i think hydraulics might be the only real approach at that scale
00:27 rue_more hell no
00:27 rue_more this is a $240 project!
00:27 GargantuaSauce lol
00:27 rue_more it'll be pneumatic muscle
00:27 GargantuaSauce like air muscles?
00:27 GargantuaSauce ie not cylinders
00:27 rue_more then something is that big, you NEED compliance!
00:27 GargantuaSauce you can achieve compliance with hydraulics, just needs fancy control
00:28 rue_more no, passive compliance
00:28 rue_more active isn't fast enough
00:28 rue_more https://www.youtube.com/watch?v=z2xWgEdiTwc
00:29 rue_more I think I'm fatther than anyone other non-company person on this
00:29 GargantuaSauce have you tried scaling that?
00:29 GargantuaSauce gonna take a lot of force to push a 6 foot leg
00:29 rue_more I have to get the dual acting working
00:29 rue_more yea, I'm confident so far
00:30 rue_more I dont know how to deal with an alg to handle the two muscles
00:30 rue_more yet
00:30 rue_more its trickey, cause the damping factor becomes extremely variable
00:31 rue_more if I was abel to control a muscle that small with a valve that big, I shouldn't have any problems with muscles 40x the volume
17:40 GuShH_ rue_more: is the crank bearing on most small 2 stroke engines held with clips like the piston is?
17:41 GuShH_ there's about 3mm side play on the chainsaw crank (took the top end out, suspected it was scorred but it's in perfect condition) I'm not sure if it's normal for the crank to have that much sideway play
17:41 GuShH_ the top bearing seems fine
17:45 GuShH_ I'm down to a vacuum leak problem, already rebuilt the carb and I'm still seeing the same problem (starts first pull after choke is off, idles perfectly but once it heats up, it stops.. but it's not siezing, no scorring marks anywhere, it looks brand new inside. in fact no carbon deposits, the oil I use doesn't allow that.
17:46 GuShH_ anyway since the top is off I might as well replace the ring, or get a new piston with double rings (alas with the loss in power and cylinder life that comes with)
17:47 GuShH_ afaik the extra ring causes more drag, so that's a loss in power, and that's where the life of the cylinder is decreased since it's performing double duty
17:47 GuShH_ otoh a thicker film of oil remains in between the two rings, which should help a lot with compression.
17:48 GuShH_ now if it's a leak problem, it could be the seals on the crankshaft bearings... I've never replaced them in any engine I own, it takes a full strip down and removing the flywheel, which I suck at.
17:49 GuShH_ in case it helps, it would turn off after a lean condition (it would race first and bog on it's own) this is why I suspect leak.
17:49 GuShH_ I even removed the fuel check valve
17:49 GuShH_ replaced all hoses.
17:49 Tom_itx check all the gaskets etc including the case
17:50 Tom_itx no air leaks
17:50 GuShH_ the head gasket with the case looks fine
17:51 GuShH_ the two halves are joined together with goop
17:53 GuShH_ Tom_itx: it had poor-ish compression which is why I took the head apart anyway, I want a new ring or new piston with double rings, but aside from that there has to be a leak somewhere! ... I couldn't remove the flywheel, so I'm stuck.
17:54 GuShH_ removing the clutch is fine, although I've only done it with the piston on (using a rope inside the cylinder)
17:55 GuShH_ if there's a crank leak there should be a sign of oil I guess? it's funny how there's no scorring anywhere though since it kept running lean
17:55 GuShH_ in case it helps I was getting "vapor lock" after it would turn off, I wasn't able to restart the engine for a while until it was cold again (still think it's got a crack somewhere and it gets worse with the heat)
17:56 Tom_itx maybe maybe not, it pulls a vaccuum
17:56 GuShH_ could be the case or the seals on the bearings, otherwise I'm clueless.
17:57 ShH_ even got new hoses for the carb
17:58 Tom_itx how's the carb diaphram?
17:58 Tom_itx or the carb itself
17:58 GuShH_ I rebuilt it, new kit
17:59 GuShH_ although the float remains untouched
17:59 GuShH_ it was just a gasket kit, but I cleaned up the mesh and let it soak in diesel, then in gasoline... then compressed air!
17:59 Tom_itx does it have one?
17:59 Tom_itx alot of 2stroke don't
17:59 GuShH_ it's a needle float
17:59 GuShH_ I don't know the correct term
17:59 GuShH_ it's a tiny lever with a spring and a conical shaped, often rubber tipped, needle
17:59 Tom_itx no float bowl on a 2 stroke
18:00 GuShH_ the lever is pushed by the pump diaphram
18:00 Tom_itx yeah
18:00 Tom_itx same idea
18:00 GuShH_ right, but there's a reservoir nontheless!
18:00 GuShH_ it's tiny though
18:00 Tom_itx just about enough for one stroke
18:01 GuShH_ speaking of tiny, rue_house, got one of those 2W 220VAC "submersible pump" it's cute, it even comes with a tiny shutter to control the flow.
18:01 GuShH_ however it can only lift 40CM of water
18:02 GuShH_ I wanted a 10 or 18W one but this is all they had :(
18:03 GuShH_ Tom_itx: since it looked like a fuel issue I rebuilt the carb and replaced all hoses, but like I said that wasn't the culprit unless I need to replace the needle inside and everything else that didn't come with my kit (I would need one of those W shaped Walbro tools I guess to set the height)
18:04 GuShH_ it needed a kit anyway it was idling rough and that took care of that.
18:05 GuShH_ I'll get a new cylinder gasket and intake gasket anyway, not sure the exhaust gasket is as important, seems fine... but maybe it all comes in a single kit. It also wasn't an impulse issue, no blockage. Heat related failure, could also be it's missing spark (the coil goes open with the heat?)
18:07 Tom_itx i doubt it
18:07 GuShH_ well, it's nothing obvious, that much I know.
18:08 Tom_itx it doesn't take much of an air leak to make it run bad
18:18 GuShH_ but it just stops once it heats up (leans and dies)
18:18 GuShH_ I wouldn't consider that "running bad" it's not running at all!
18:19 ShH_ throws the old fuel lines at rue_h
18:19 Tom_itx maybe a worn cylinder
18:19 GuShH_ looks fine, it's a bit tight to slide the piston in as well
18:20 GuShH_ I'll take it to the store and see if they can measure it, I don't have the tools nor the data
18:20 GuShH_ a new set is not terribly expensive, but I don't like throwing things in until it works or I give up
18:20 Tom_itx i'm just guessing on past experience too
18:35 GuShH_ alright 2W is not enough for anything really... and it doesn't get near close the 40CM claim, stupid chinese pump!
18:35 GuShH_ there's a reason I was looking for close to 20W power
18:36 Tom_itx what's it pumping?
18:38 GuShH_ right now just water, it's meant to pump cutting oil
18:38 GuShH_ a real pump costs a small fortune compared to these
18:39 GuShH_ I just need to find a bigger one..
18:42 GuShH_ sorry let me rephase, it's meant to pump water but I want it for cutting oil heh
18:43 GuShH_ looked at motorcycle and car pumps already, not a single one is as cheap plus it would require machining of a plate, coupling, etc
18:44 GuShH_ I thought these would have seals that could deteriorate with the oil but I've read on the machinist forum that they work just fine
18:44 GuShH_ now, why is the flexible hose more expensive than the pumps, I don't know.
18:46 Tom_itx neoprene tubing?
18:46 Tom_itx or those snap together ones...
18:46 Tom_itx i remember that conversation now..
18:47 GuShH_ I made a mockup of a screw pump, it does pump but it requires a lot of work to get it into a usable pump... so I'm looking at cheap commercial pumps for aquariums
18:50 GargantuaSauce reciprocating pump!
18:51 GuShH_ GargantuaSauce: I even thought about using an old 26cc engine I have, just for that purpose.
18:52 GuShH_ add a couple valves and it should work if ports and stroke are limited, in theory
19:07 GargantuaSauce https://www.youtube.com/watch?v=khlfTYkkLOk want
19:15 GargantuaSauce it's pretty sweet that serial arms are showing up with the capability to do precision machining
23:06 rue_more oooo I should add effective load ohms to the digitial display!
23:09 GuShH_ bleh, I had to make a flywheel puller for the chainsaw... just a bit of square stock (mild steel) two through holes for M5 (so 6mm) and two long M5 allen bolts, then a brass spacer and boom, flywheel pops off in seconds! no need to hammer the hell out of those poor bearings. Of course my drill press sucks and I had to oversize the holes to 7mm otherwise they wouldn't line up
23:09 GuShH_ thankfully the flywheel already had the M5 tapped holes
23:45 GuShH_ can't see any signs of bad seals on either side, the crank case was a bit sweaty but near the exhaust, could just be migration from regular exhaust... I need to make some rubber seals to close up both ports and add 10-15psi with the air compressor through the sparkplug hole and spray some soapy water around to see if there are any leaks I guess...
23:45 GuShH_ I'm not sure any more pressure would be a good idea
23:47 GuShH_ Tom_itx: thoughts?
23:48 GuShH_ the design is a lot nicer than what you'd find on some higher end saws, at least you can take one side cover off the engine to remove the crank, on a lot of saws it has two equal halves that are press-fit together and it's a pain in the arse to deal with
23:52 GuShH_ flywheel says "http://www.xinyadj.com/" on the back