RFguy

"Better to be quiet and thought a fool, than open your mouth and dispel all doubt." love it. hangar is gettign closer.

I have never seen roos on haul roads on any of those sort of mines. Maybe it's just where I go. nevertheless, a good effort by the pilot to get it onto some unoccupied ground .

Kangaroos on a mine haul road ?????? What ? sorry I dont buy it. Kangaroos generally stay right away from such places.

Hi Bob ..Jab mixture was about right before LCH, now rich. I am led to beleive that all 912 engines have problems with the intake manifold at low gas velocities (idle etc) and that they all tend to foul / rich the front two cylinders with extended low idle , due to intake manifold arrangement. But I dunno, that's what I have heard and read

Bob, all over rich Bings powered engines I have seen are all problems with float bowl vent location OR enrichment not getting fully off, or accidental carb heat. However there is another interesting one I am partially troubleshooting right now, Jabiru engine that was about right, now rich after LCH. Heads instead of 150C , now 100 C, which would have an effect on vapourization/ atomization and combustion. I have bought a Oxygen mixture sensor so I can get a benchmark to understand what's going on- (IE to figure out if its really rich or just low EGT, or a combination thereof) since there would be an effect of both perhaps lower head temps (change to behaviour in the chamber) and also there would be some cooling of the EGTs due to the much cooler heads and headers. -glen

depends if we are talking about Bing carbs, or something else with a genuine restriction.

"When a coolant temperature sensor decides that no choke is needed , the magnet releases and a spring returns the cable to the off position " ha ha like when just airborne ?

Vso 26-30 kts ? and Vne 124 kts wow ! you can get in and out of short strips AND chase the Germans in a vertical dive

I think many of the problems come from seeing the two modules stacked on top of each other. They cook each other .. 10mm of separation would do it.... but airflow is king !

The starting carburettor is quite clever ,Bob. the sytem permits a big gob of fuel first breath and then uses the starting jet. It is an impressive and ingenious piece of engineering.

skippy are you sure that pulling choke closes the throttle? I have never seen any aircraft do that. I learned quite a but abotu them after doing the Dunstone Bing Masterclass. read about it here : http://www.bingpower.de/download/datenblaetter/type94e.pdf

While Bing DO call it a choke, yes I will accept that, The Bing cold start assist is not a choke like the traditional restriction of old automotive carbs. Actually the reference manual calls it a starting jet- but - It's really a completely independent carburettor. Opening the enrichment path allows vaccuum on the engine side of the throttle to pull fuel via the enrichment jet into the engine. This is why Bing carbs enrichment does not work without the throttle closed- it needs vaccuum to suck fuel.

you only need the ENRICHMENT (since it is not actually a choke) briefly. Skippy, how about a magnetic solenoid that just pulls against the spring in the engine bay. you either want it on or off.... since the throttle being closed is what activates it. (or allows it to activate, more truly) . certainly yes does need a spring. enrichment shafts and the shaft o rings can get sticky due to fuel products that solidify.

Jab are iron. (I thought) . or a stainless type I am not familiar with.

mmmmmm what does the street advice say on sensor location with a turbocharger ?

agreed Nev. There is a tenuous relationship between piston expansion and barrel expansion.... I did run some numbers for another when considering scenarios of go around and say, top of climb WOT >> flight idle. ************************************************************** Jab cromo 4140bores : 175deg C rise (25C >> 200C) (12.2ppm/mK up to 400 deg C) assumes unifrom temp , Though I would expect the bore to go non circular because the undersides are far hotter than the top sides (40 deg difference haphazardly measured) . IE pear shaped however, if uniform, is about 0.2mm growth. so...say start at 97.6mm >> 97.8mm 4032... I know pistons have irregular expansion (due to lots of things.) worst it would be 19.4ppm/m/K . pretty steady rise in CTE with temperature. linear to 300C... 20ppm at 100C, 21ppm at 250C we'll call it 20.5 ppm . so 97.5mm room temperature piston worst case assuming uniform temperature (is NOT- bad assumption !!) would be 97.85mm - a 0.34mm growth at 200C (175degC rise) --------------- Now, 2618. that has quite a different CTE curve CTE 22.3ppm 25-100C, 23.2ppm 20-200C, 24ppm 20-300C. We'll use 23.2ppm. so above numbers for 2618 is ---- 97.89 or 0.39mm growth. Therm conductivity for 2618 is 146. for 4032, is 138 (lower due to Si).

Hi Carbon. your insight is useful. yes glass like indeed. " Is the assumption that the rings are seized onto the piston at operating temperature as well ?" you basturd (french accent) you just introduced another unknown ! 🙂 it would be useful to measure BMP etc on each cylinder eh instead of in a lab. I would have thought spark plugs could have done that . well you can of course with measuring breakdown voltage of the plug etc, and various breakdown emission corona modes..

So ! oxygen sensors.... They seem to be located on the headers where the cylinders combine. some are exhaust heated (must get to min 350C, pref 500C) most with more than 2 wires are internal heater type (a couple of amps at 12V) . and wideband are 5 wire usually. has a current output and requires 2-5 V depending on the sensor + heater. I bought a wideband sensor from ebay. we'll see what it does eh ? But if you want simple : use a narrow band sensor. IE you just get a "above stoich" and "below stoich" output. VERY simple to use with just a multimeter reading voltage. and a 12V source for the heater. wideband sensor provides more 'linear' output from rich to lean- but most cars just want to know if they need to go one way or the other. Titanium sensors (rather than zirconia) more tolerant of crap in the gas.

so, if the ring becomes stuck - (and the stuck rings are all the way in against the inner radius) IE flush with the piston outer- then it would stop effectively conducting (its share of the ) heat to the barrel on that side of the piston , and just get hotter.

new Jabiru rocket engine ? what ?

diamonds are made under super temperature and pressure , I guess we have the right conditions.... (yeah I know its not real diamond- but has glass appearance.)

spacecraft ?

yeah , UHF. BNC is fine . make sure you buy 50 ohm connectors, not 75 ohm BNCs.... Be aware, when you talk on UHF from 1000' above the ground, you'll be heard 150km + .... you might find it easier to place the whole run, instead of a join... https://www.minikits.com.au/BNP01 and https://www.minikits.com.au/BNS02 https://www.minikits.com.au/HT336 and https://www.minikits.com.au/JAW336D2 https://www.ebay.com.au/itm/321637603591

Hi jetboy, thanks for the input. Jabiru have used 'various' pistons. Interesting on your thoughts of the heat narrowed lands hypo. When I cleaned out the lands of the last engine , the middle ring lands had what looked like black glass in them... it was tough like diamond. took a month of sundays of scraping with the end of a ring to clean all the lands pristine.

for small ground planes, like these, being a solid or approximated with thin elements wont make any difference in this application. the only time this is important is if, for example, you have some sensitive electronics underneath the antenna- the solid plane will be an electrostatic shield and prevent possible interactions. also, noise from the cockpit can get on the coax cable outer and be brought into the antenna pickup field. The complete ground plane (solid) reduces the pickup from garbage on the cable. in this application, the minimum you need in thin elements is two wires in opposite directions to acheive symmetry. The coax cable should come away at 90 deg to the antenna, ideally, in the two wire scenario.