Hi all-

Anyone have experience operating larger diesels (like 40-49 size)?

It occurred to me that the torque capability and running characteristics of the diesels might be 'reasonably' similar to a 4 stroke of the similar size - with the benefit of fewer moving parts etc etc. (just from a vague concept of more torque available in both types)

PAW makes some large diesels these days (when I was a kid running Olivers and PAWs the biggest was a 19 and the whole concept of a large diesel seemed absurd) and I know the Eifflanders ran them in full size stunters -

but I havent read/heard any reports on vibration, torque, fuel consumption, appropriate propellors, running characteristics, noise etc.

Any one out there know anything? Im thinking of trying one as a power plant to a semiscale aerobatic biplane - a fun project more than a 'serious' stunter, and was thinking about 4 stroke as a power plant then wondered 'why not a big diesel'?

Anyone know why it shouldnt work??

Thanks in advance

Peter

Thanks Lou-

I actually like the smell of diesel - its a heritage thing.....

Any written engine tests available? I guess theres some 90's issues of Aeromodeller but I dont know how to get hold of these....

Any sense for how a 40 diesel will stack up against a 40 4-stroke?

Cheers

Peter

   Hi Peter,
 I have been chasing info on large Deisels myself and have found out the following...

 A Paw .40 should pull a typical .49 -.60 size glow powered model with out too many problems. 

 I got in contact with Eric Clutton (aka Dr.Deisel) and he is flying a Veco Chief powered by a Paw .35. He reckons it nearly pulls his arm off on 70' lines!

 I just purchased a NIB Paw .49 that I will put into a large .60 size stunter. 

Mr Clutton stated that from his tests the .60 Deisel is on par with a .90 4-stroke and that the .49 is not too far behind. The .49 will happily pull a 14x5 prop at about 9000 rpm, so I figure it isn't too far off the pace of perhaps a saito .72 or similar.

 I am only guessing, but I imagine that the .40 deisel may have a similar amount of torque to .52 ish size 4-stroke.

 In addition to the big Deisel i wish to try out a mid size (.40-.53) 4- stroke in the not too distant future. It would be interesting to compare "apples to oranges".

 Hope that some of this helps,

 Cheers, Rob.

Thanks gents -

How much wind up in manoevers have folks observed with large props, slow revs and moderate pitch on these diesels?

Kind Regards

Peter

    Hi Peter,

  I don't know for sure as I haven't played with any big Deisels (yet) but, I think that any windup would be less pronounced as the Deisels should be running much closer to their peak torque rpm than a glow engine that has comparable output.

 Cheers, Rob.

  Hi Peter,

 I'm not sure that there will be much engine test data from the "good old days" that relates to large Deisels, as the bigger Deisel engines seem to be a reasonably recent phenomena. (I think most big deisels were used in boats?)

 If you find anything of interest please share it with the forum as I (and others I presume) would be keen to see it.

 I have been looking for big Deisel info myself and will post any findings as they come to hand.

 Cheers, Rob.

Peter,
To  your Post#9:

In Derek Pickard's test of the PAW 40TBR, in Stunt News several years ago, he said much the same as is repeated here. They can be set to an RPM and it doesn't seem to matter uphill, downhill or lingering up top. (In my experience, you can hear a subtle increase in "stress" in prolonged figures up top, but well within the engine's compass.)

A factor explaining both the economy and rev limiting in medium-large sport diesels is that their port passages are quite small. They don't flush vast amounts of air through, as is needed to burn methanol-based fuels. The diesel's power comes more from a higher heat energy basic fuel component - kerosene, than from a higher quantity of a lower heat energy fuel component - methanol. Setting a diesel is trickier than setting a glow, because of methanol's tolerance to a slightly 'off' needle since you're still going to burn quite a bit of it.

For the deodorized among us Yank fliers, the objectionable times are starting and launching, unless you use a really rank kerosene in the fuel. With a clean kerosene, the exhaust is nearly odorless, or more like the steam smell of an old-fashioned neighborhood hand laundry - if you're old enough to recall that...

But, for starting, launching and recovery, we have to impose upon other greasy-rag types if available, or beg the indulgence of one of our white-shoes/pants/airplanes buddies... 

The only negative I've heard, once you get past the smell matter, anyway: A British flier who was discussing diesels in stunt answered a simple question: "How do you tank to get a consistent stopping time?"  He answered, "You can't, really. You just do as best you can on that."

A 'click' on the needle could mean an extra 30 seconds of power, I guess. It's not so bad in the USA with the 8-minute flight limit, but I can see that would be of concern for FAI's 7-minute limit.

Also, I think on on RC Universe's CL forum, there's a thread on a modeller starting out with diesel. Good first steps stuff, and he sounds quite pleased, now. ...After a frustrating beginning...

One of the guys in our club, old Ollie, since passed away bless his soul, had a PAW49, I think.  Anyway, a big diesel.  It flew a big plane just fine.  But he did manage to kill a lot of grass starting it.  Diesel fuel is a lot harder on the grass than glow fuel.

OHMIGOD!  The term Greasy Pete is about to take on an entirely new ... um, er ... aroma!  Our poor field will never be the same. 

Ted "Holding his nose" Fancher

Be afraid, Ted, be very afraid........Ill be passing round the ether to keep all you Nats Champs sedated while I fly.....

It does sound an interesting experiment to me (diesels that is, though watching you and Brett staggering around from too much ether might be entertaining). From old engine reports the torque curve of the diesels is a bit steeper and they are unable to achieve the revs that modern glows allow so I think they might actually do quite well for stunt with less potential for windup - a different approach to stabilizing the power run perhaps? I think I need to try it and see.

Im also seriously considering driving PTG apoplectic by building an old british diesel combat model. Replica Oliver Tiger III powered no less. Why not upset everyone at once??

You think he'd teach me how to fly it? As long as someone else launched it he might be game.....the sheer nostalgia of it all might encourage him to grow his happenin afro 'do' back. (remember the 80's??)

GP

I've run some diesels and was of the same mind a few years ago. There are some issues with diesels, but especially if you are trying to use it in a contest situation. You gotta warm it up before your flight. You'll be unpopular in the pits, if you do that. Next problem is run time...likely to be much less consistent than a glow, with more adjustments and much less fuel consumed. If you're off a 1/4 oz with a diesel, you under/over run. AMA rules have always allowed engine shutoffs, but FAI didn't, for quite awhile. Shutoffs are now allowed again in FAI, and there are several ways to make them work, tho not all are allowed by FAI rulz. I also have some information on a fuel tank that automatically shuts off the engine after too many level laps. Ideal for a multi-engined stunter, OBTW.
Steve

Steve - thanks - I knew someone must have tried this - warm-up I can handle - even now the big shots burp their firebreathing take-your-finger-off-in-a-nanosecond motors to remove accumulated oil from the pipe headers.

Consistent engine run is something that I was thinking about simply because there are more variables - compression/timing as well as needle setting and humidity/density altitude. But it strikes me that this variablity could also be an advantage if its well understood.

Run timing is another matter - im VERY interested in finding out more about these options - the FF power guys have used these timers for years - all we'd have is a longer time.... if AMA and FAI allow shutoffs now seems like this would be the 'sledgehammer' answer. Any details on how these work??

Sounds like an excellent idea for separate post....

Cheers!

Peter

Personally, from my experience with Diesels, I don't care for them, especially one particular brand.   

The one's I've had the best results with have been Webra and MVVS. 

BUT, for anyone concerned with Diesel vs 4-stroke, there is now a 4S Diesel - the ENYA .41 4S-D. Looks like a regular 4S but with a strange gadget in a place formerly occupied by the glow plug.

No info on price or availability. 

Bob Z.

I am getting ready to try to fly a PAW .29DS in my Barnstormer. I'm concerned with the high placement of the NVA in the venturi when the plane is upside down. I hope the engine isn't too fussy about mixture.