Michael, When I wrote 'prolonged flight situation', I guess what I was trying to say was: falling faul of that *CAUTION *Avoid RPM during cruise below 2300 min –1! found in Dimona Flight Manual.
I will keep in mind what you said about windmill-starting the engine. Regards Jarek pon., 22 paź 2018 o 21:34 Michael Stockhill <[email protected]> napisał(a): > I am not sure what the definition of prolonged operation might be. In my > soaring environment, thermals are generally strong,showing 5 to 8 knots, > but they are quite far apart. I frequently need a relight, and I sometimes > dodder along with the prop in cruise pitch at what I sense is zero > thrust--somewhere around 1500 to 1800 rpm. I would be surprised if this > translates to more than 15-20% of available power. That may be the least of > my concerns when I break the surly bonds. > > But the recent FAA AD note on Hoffman wood props brings up another > potential concern. I now realize that with lag screws holding the blades to > the hub, overspeeding could potentially lead to shedding a blade due to > high centrifugal force. I have occasionally windmill-started the engine by > diving to accelerate to 70 knots or so. (Once for real when a wire on the > starter came free due to using spade connectors rather than real aircraft > design.) After the engine starts the rpm really wraps up. Recovery must be > aggressive to keep from overspeeding. Something to watch in the future. > > On Mon, Oct 22, 2018, 1:07 PM Jarek Steliga <[email protected]> > wrote: > >> Nick and Nigel, >> >> I am suddenly wondering how relevant these considerations are to your >> average, daily flying. In other words why would anybody fly their Dimona at >> RPMs below 2300? As I experienced it myself in my first tentative flights, >> you want to maintain your RPM at 2300 or more for cruise, to keep the IAS >> at somewhere around 130 km/h. If on the other hand you want to circle in >> thermals which are too weak for soaring, then you set the propeller to >> START pitch and also maintain 2300 RPM to keep the IAS near 100 km/h (and >> the sink rate at zero to utilize even the weakest updrafts). Other than >> that you just idle the engine for 2 minutes or so prior to switching it >> off. >> >> Could you please shine light on what I am missing? Can you think of >> prolonged flight situations when you would like the propeller to turn at a >> slower rate? >> >> >> Regards >> Jarek >> >> pon., 22 paź 2018 o 15:22 Nigel Baker <[email protected]> >> napisał(a): >> >>> Idle power is not the problem. >>> >>> The harmonic happens under load. It is influenced by the acceleration of >>> the crankshaft every time the engine fires. Low power = low acceleration >>> levels. >>> >>> Looking for more info but from memory it was a band of 200RPM. >>> >>> Yes it is important to use a prop known to match the engine re harmonics >>> thus you will find a list of props approved for the Limbach Engines under >>> its Type Certificate. >>> >>> Note this is also true of the aircraft manufacturer as well. Type >>> certification must match between the engine the aircraft and the prop. >>> >>> The harmonics are completely different to prop balance which is another >>> complete issue. >>> >>> I once asked Peter Limbach how could it be possible to operate at full >>> power at 2100-2300 RPM. I get more than that static on ground test. >>> >>> Ah but we found an issue on the Dyno which sort of implies a different >>> issue again. >>> >>> Nige. >>> >>> >>> >>> >>> >>> *From:* [email protected] <[email protected]> *On >>> Behalf Of *Ric Sutton >>> *Sent:* Monday, October 22, 2018 10:39 PM >>> *To:* [email protected] >>> *Subject:* RE: [DOG mailing list] Zenith 150 CD 3 - oil >>> >>> >>> >>> Sorry Nige, it was my imaginary lower limit to the range of revs that a >>> bad harmonic was present, Not the lower limit of operational revs. though i >>> guess why does the lower rev range of a bad harmonic matter if you are to >>> avoid prolonged operation below 2300. This being the case what is the >>> official standpoint of limbach on thermalling with the engine ticking over >>> below this 2300 limit? >>> >>> Cheers >>> >>> Ric >>> >>> >>> >>> *From:* [email protected] [mailto:[email protected] >>> <[email protected]>] *On Behalf Of *Nigel Baker >>> *Sent:* Monday, 22 October 2018 2:54 PM >>> *To:* [email protected] >>> *Subject:* RE: [DOG mailing list] Zenith 150 CD 3 - oil >>> >>> >>> >>> You have seen it Rick and not at the pub over a beer.. >>> >>> Look in brackets below. >>> >>> 2300RPM >>> >>> Nige. >>> >>> >>> >>> 9 >>> >>> >>> >>> Hoffmann >>> 2 >>> H 36 >>> DIMONA >>> Limitations >>> >>> >>> >>> >>> >>> 2.4 *Engine Limitations* >>> >>> >>> >>> Engine >>> Type: Limbach >>> L 2000 EB 1C >>> >>> >>> >>> RPM Limitations >>> (Indicator Markings) >>> >>> >>> >>> Maximum take off RPM >>> (maximum 5 minutes) 59 KW (So hp.) 3,400 RPM >>> >>> >>> >>> Maximum ambient atmospheric temperature + 380 C (+100 F) >>> >>> >>> >>> Maximum RPM (METO) 53 KW (72 >>> hp.) 3,000 RPM >>> >>> >>> >>> Red Line >>> 3,400 >>> RPM >>> >>> >>> >>> Caution Range - >>> Yellow Arc 3,000 – 3,400 RPM >>> >>> >>> >>> Operating RPM - >>> Green Arc 700 – 3,000 RPM >>> >>> >>> >>> *CAUTION* >>> >>> >>> >>> Avoid RPM during cruise below 2300 min –1! >>> >>> >>> >>> >>> >>> 2.5 *Oil Pressure:* >>> >>> >>> >>> Maximum Oil Pressure (red line) 4 bar (55.8 psi) >>> >>> >>> >>> Minimum Oil Pressure (red line) 1 bar (13.9 psi) >>> >>> >>> >>> Operating Range (green arc) 1 - 4 bar (13.9 — 55.8 psi) >>> >>> >>> >>> 2.6 *Oil Temperature*: >>> >>> >>> >>> Maximum Oil Temperature (red line) 120 C (248 F) >>> >>> >>> >>> Operating Range (green arc) 50 - 120 C (122 — >>> 248 F) >>> >>> >>> >>> Minimum Temperature (red line) 50 C (122 F) >>> >>> >>> >>> 2.7 *Cylinder Head Temperature:* >>> >>> >>> >>> Maximum Cylinder head temperature (red line) 250 C. (482 F) >>> >>> >>> >>> >>> >>> 2.8 *Voltmete*r: >>> >>> >>> >>> Maximum voltage with engine running: (red line) 14 VDC >>> >>> >>> >>> 2—3 >>> >>> >>> >>> >>> >>> >>> >>> *From:* [email protected] <[email protected]> *On >>> Behalf Of *Ric Sutton >>> *Sent:* Monday, October 22, 2018 4:39 PM >>> *To:* [email protected] >>> *Subject:* RE: [DOG mailing list] Zenith 150 CD 3 - oil >>> >>> >>> >>> Hi Jarek >>> >>> I’m sorry but i have had a look and can’t seem to find a reference to my >>> second imaginary number. I don’t know whether it was obtained through >>> conversations with Hoffman people or limbach people or dimona people or >>> people from a random encounter at a pub. It may have been obtained from >>> what felt about right ie. the bottle of beer in my cup holder didn’t froth >>> over or go prematurely flat below those revs( just kidding, though if >>> anybody here has a clever idea on where and how to mount a cup holder that >>> would be great). All jokes aside i do recall a conversation with a >>> propeller service agent that told me of an aluminium based air frame that >>> was financially written off after cracks were found due to the bad >>> harmonics of an “alternate” propeller so from that i took it as being a >>> serious thing. i also found some you tube videos of propeller blades self >>> destructing.( propeller resonance >>> <https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=video&cd=1&cad=rja&uact=8&ved=0ahUKEwiLtIzSsJneAhVLMI8KHY8YAUEQtwIIJzAA&url=https%3A%2F%2Fwww.youtube.com%2Fwatch%3Fv%3DPQjmDmcWJn8&usg=AOvVaw048W5y_0kGNdO0WaB0eUdi> >>> ) >>> >>> What you have done now though is inspired me to finish my home made >>> accelerometer/balancer and gather some actual real data to see if i can >>> establish some numbers for my own curiosity J >>> >>> Welcome aboard and may you enjoy your dimona as much as many of us do >>> >>> Cheers >>> >>> Ric >>> >>> >>> >>> >>> >>> *From:* [email protected] [mailto:[email protected] >>> <[email protected]>] *On Behalf Of *Jarek Steliga >>> *Sent:* Friday, 19 October 2018 3:31 AM >>> *To:* [email protected] >>> *Subject:* Re: [DOG mailing list] Zenith 150 CD 3 - oil >>> >>> >>> >>> Michael, Ric thank you. >>> >>> >>> >>> >>> >>> Ric, where did you find the "range" of unrecommended RPMs as opposed to >>> just a lower limit of 2300? I leafed through both attached documents and >>> didn't come accross the second number. I also tried to google "Limbach L >>> 2000 harmonics" and got nothing. If it isn't harmonics (wchich I hope it >>> isn't) then the RPMs lower limit would suggest excessive load torque with >>> prop in just the cruise position. >>> >>> >>> >>> Regards >>> >>> Jarek >>> >>> >>> >>> >>> >>> >>> >>> >>> >>> Regards >>> >>> Jarek >>> >>> >>> >>> czw., 18 paź 2018 o 15:53 Michael Stockhill <[email protected]> >>> napisał(a): >>> >>> In the States, dashpot oil is readily available from vintage British car >>> parts suppliers such as Moss Motors for $10-12 for a squeeze bottle. >>> Claimed to have appropriate preservatives and conditioners. As little as is >>> consumed, I have found no incentive to look for alternatives. >>> >>> >>> >>> On Thu, Oct 18, 2018, 5:09 AM Ric Sutton <[email protected]> >>> wrote: >>> >>> Hi Jarek >>> >>> Here’s my two cents worth- i use automatic transmission/power steering >>> fluid in my cd150’s. seems to work fine and haven’t had any compatibility >>> issues with rubber diaphragms etc as yet. The oil and plunger act as a >>> damper for the piston to which the needle that alters your fuel air mixture >>> is attached. Over the years i have heard various stories from people that >>> use these carbies n race cars that actually snip the damper off(similarly >>> people that don’t put any oil in there), to stories from people that use >>> them in multi carb set ups (ie 12 cylinder jaguar engines) that can’t get >>> them to tune properly without the correct oil (though after some discussion >>> i believe that spindle wear was more their issue). In an automotive >>> situation there will be some minor noticeable throttle response differences >>> but in the dimona application i suspect the differences will be minimal >>> particularly as instantaneous dramatic throttle changes should be rare. >>> >>> The rev issue >>> >>> The reason the book states that *prolonged* operation in that rev range >>> is to be avoided during cruise is indeed because of a bad harmonic >>> (potential for cracked crankshafts etc) Thus, i believe that it is a >>> problem whether the blades are in fine or course pitch it is just operating >>> in that rev range with a moderate load on. In saying that, these are a >>> reasonably robust little engine, don’t be scared. Note the emphasis on the >>> word prolonged. >>> >>> Please someone jump in if they have info to the contrary this is just >>> what i have learnt over the years and am always willing to learn something >>> new. >>> >>> >>> >>> *From:* [email protected] [mailto:[email protected]] *On >>> Behalf Of *Jarek Steliga >>> *Sent:* Thursday, 18 October 2018 5:47 PM >>> *To:* [email protected] >>> *Subject:* Re: [DOG mailing list] Zenith 150 CD 3 - oil >>> >>> >>> >>> Hello again, >>> >>> >>> >>> If my oil "mixture" is too thick (or too thin) what are the symptoms? >>> Does the carburator respond with a delay or too fast to the throttle >>> inputs? Is that dangerous or just annoying and easily noticed? >>> >>> >>> >>> >>> >>> Regards >>> >>> Jarek >>> >>> >>> >>> >>> >>> >>> >>> czw., 18 paź 2018 o 08:43 Jarek Steliga <[email protected]> >>> napisał(a): >>> >>> Thank you >>> >>> >>> >>> śr., 17 paź 2018 o 23:28 Rob Thompson <[email protected]> >>> napisał(a): >>> >>> Part number 10 on the diagram. >>> >>> regards >>> >>> Rob >>> >>> >>> >>> Rob Thompson >>> >>> 0429 493 828 >>> >>> (Please note that my new email address is [email protected]) >>> >>> >>> >>> >>> >>> On Thu, Oct 18, 2018 at 7:50 AM Jarek Steliga <[email protected]> >>> wrote: >>> >>> >>> >>> >>> >>> Hello Rob, >>> >>> >>> >>> >>> >>> The oil seems to disappear too fast as you say. Could you help me to >>> identify which particular o-ring on the attached drawing needs to be >>> replaced? >>> >>> >>> >>> When you mention 5/xx multigrade, do you mean 5W/xx? >>> >>> >>> >>> >>> >>> Best regards >>> >>> Jarek >>> >>> >>> >>> >>> >>> >>> >>> >>> >>> >>> >>> >>> >>> >>> >>> >>> >>> >>> ---------- Forwarded message --------- >>> >>> From: *Rob Thompson* <[email protected]> >>> >>> Date: wt., 16 paź 2018 o 22:23 >>> >>> Subject: Re: [DOG mailing list] Zenith 150 CD 3 - oil >>> >>> To: <[email protected]> >>> >>> >>> >>> >>> >>> Hi again Jarek, >>> >>> You can use straight engine oil but even a 5/xx multigrade is a bit >>> thick and tends to dampen the piston too much. >>> >>> We mix 50/50 light machine oil and engine oil. >>> >>> If it keeps disappearing it means that the rubber O-ring which seals the >>> needle inside the piston is perished. >>> >>> regards >>> >>> Rob >>> >>> >>> >>> Rob Thompson >>> >>> 0429 493 828 >>> >>> (Please note that my new email address is [email protected]) >>> >>> >>> >>> >>> >>> >>> >>> >>> >>> >>> >>> >>> >>> >>> >>> >>> >>> >>> >>> Hello, >>> >>> >>> >>> As per Limbach Maintenance Instruction, only a specific oil p / n: >>> 170.210.005 can be used to fill up the carburator. Since this seems to me >>> pretty pricey, can other, readily available oils be used in its place? What >>> is its recommended viscosity? >>> >>> >>> >>> Best regards >>> >>> Jarek >>> >>> >>> >>> >>> >>> >>> >>> >>> --------------------------------------------------------------------- >>> You are subscribed to the Dimona Owners Group mailing list. >>> To unsubscribe, send email to: [email protected] >>> >>>
