Large Diesel Engines

[Garf]

I just finished resorting my pages of large diesel engines. It got me to thinking. The largest purpose made diesel I have seen is a 60, or 10cc engine. Since there is seemingly no limit to glow engine size, Is there any reason there are no diesels over 60 size? or am I just missing something?

[exrafbod]

Nope, you are certainly not missing anything Phil.

It occurs to me too that the big diesel potential is there for anyone who cares to pursue the idea but bear in mind that the power equivalent of, say a 60 or 61 diesel woiuld be 'up there' in terms of glow equivalence. It is possible to swing a very large prop on a Dieselised 60 or 61 more than on a 60 or 61 powered Glow engine for wich the accepted standard is 12x6 or a load factor of 29 or 30.

To my mind there has not been enough industry experimentation into large capacity diesels for aeromodelling purposes except for one local aeromodeller who has tried it an has met with some success. I believe the application was for non hobby related commercial survey/photography purposes.
(If you like I can try to put you in touch with him.) I suspect that the cost of fuel would perhaps be the prime discouragement here, as it is by comparison to standard 2 Stroke Gasolene for large engines, prohibitively expensive.

More or less any motor including large capacity IC engines not having a lapped piston can be modified to run as a diesel. Davi* Diesel Head Conversions certainly seem to think so.

Anyhow most people seem to be put off by the smell of diesel alone so there could be another reason for its lack of popularity right there. Not me. I brew the stuff and even manage to sell some of it occasionally.

Thirdly, because diesels require some effort in the cranking
to turn over it would be a brave and really strong man who could whip let's say a 1.50 cu inch diesel over by hand to get it to run. The compression required may well be out of the range of Joe Average's flicking power. (The model would be pretty huge too I would think.)

....just some thoughts on the subject... as nobody else seemed interested enough to chip in on this one. Maybe now we'll get some rebuttals now. Let's see.

[exrafbod]

....p.s.

Diesels have no future in aeromodelling. See above.

Pack up your collection and send it to me and I will mothball it and look after it for you forever - no charge.

(this'll stir something up)

[jet]

IC engines of any type have little future in aeromodelling,;the few diesels out there leading the way. So far as sending them to you , I'll have to think about it. My favorite diesel is the ST G20-15D; but, as Bob Davis said, they are getting too valuable to fly. ;D

Jim

[Garf]

I understand the Enya 15D is a good runner.

[exrafbod]

Everybody else's Enyas appear to be very well produced, start easy and produce bags of power. The two I had were not. They have a good reputation but I never had much luck
with them not that they were the 15 you mention. One was a .35 glow and the other a .29. To each his own

[loucrane]

As exRAFbod mentioned in his longer post, DDD does offer conversion heads for several large glow engines. Bob D is a businessman, and is not likely to keep items in production unless there's a market.

But, true, I haven't seen much mention of these particular heads, except in his ads or catalogs.

The hi-power electric starters now available should be able to handle the starting torque.

The slight reduction in noise, better 'economy' and significant increase in torque diesels usually offer may overcome some of the ether-stink problem. Good quality campstove kerosene is pretty low- to no-odor, and has about the same power (BTU/weight) as any grade available.

BTW, diesels - and converted-to-diesel glows - idle and throttle very nicely, given slightly lean and slightly higher compression WOT settings.

[jimthomerson]

there is considerable discussion of larger diesels, etc. here.

www.rcuniverse.com/forum/Everything_Diesel/forumid_87/tt.htm

Jim

[exrafbod]

Lou,

to appreciate the nature of the diesel engine and its characteristics is also to understand what can happen when you slap a high torque starter on a compression ignition motor. Not only is it damaging to the engine in terms of snapped conrods through hydraulic locks but it can be injurious to health in that starters can slip off the spinner leading to all sorts of possible injuries due to the high torque stresses incurred etc. My advice is DO NOT use an electric starter on a diesel at any time.

Where diesel head conversions have their place I do not argue only to point out that a true diesel engine i.e. one built solely for the purpose is a much better and more efficient route to go than a head conversion. BTW I have a converted OS 25FP dieselised with Mr. Davis's product.

The Ether Stink is all part of the mystique of diesels. You e(i)ther love it or hate it. I do not hate it.

Jim,

I thought rather than switching traffic to other boards the idea was to populate this one with intelligent, inciteful knowledge and comment so that other aeromodellers will use this one as a reference too. Not trying to raise a ruckus and not trying to duplicate information either.

[jimthomerson]

I think this is all about becoming informed, and knowing where information can be had is the largest part of being informed. Actually, I just found out how to copy and paste a URL and I am so excited that I havn't yet come down enough to consider the morality of it.

The largest diesel I have run is a dieselized Tower 40, and I routinely used a starter on it because I did not wish to change the compression from running compression. Of course I have four broken cranks, none while starting, and the engine now has several hundred runs on it converted back to glow with no problem. I am running a 2 oz heavy hub and I think that contributed to the diesel broken crank problem, as others have run dieselized Tower 40's with good success. There is a grinding relief groove just in front of the crank web and that is where the cranks break.

I've also been flying a ST G20-15 diesel. It has many, many flights on it and will no longer hand start reliably at running compression, therefore I have been using a starter on it for probably several hundred flights.

Because I and others have run glow engines on diesel fuel with good results, I don't think diesel runnig compression is all that different from glow running compression. So if one is careful, as you should be with any engine, I see no reason not to use a starter on a diesel.

Jim

[loucrane]

ExRAFbod...

Fully agree that starters and 'diesels' are ordinarily a bad combination. Someone mentioned the FEAR of handcranking a monster diesel(or dieselized) engine, thus the comment on using them.

As Jim reminds us, a WELL-built, preferably 2BB, diesel, native or naturalized, AT A KNOWN AND DEPENDABLE SETTING, is more likely to survive a starter. ...unless we get sloppy and flood them...

Jim, btw, I recently noted something new for hot starts on run setting for some of my PAW 19BRs... Seems to go best with a hint of choke forward - just a touch into rising compression/case intake, NOT thru TDC - and a sharp back flick of the prop.


Much nicer - and quicker - than backing compression, fiddling with forward flippping, then trying to find the setting again.

[downunder]

Jim
From the lack of comments it seems maybe no one picked up on the implications of your last para

I've been thinking about trying this ever since I first heard it can work. I've heard there's a South African guy who's been flying stunt like this for some time. Maybe you could give us some more details on it? I believe you have to leave the plug connected for about 30 seconds after the engine starts to give it time to heat up the cylinder head? Do some engines respond better than others (I'm thinking maybe European higher compression would be better than something like OS)? What about plug life? Obviously the plug goes out when you disconnect the battery but does the much higher (almost detonation) cylinder pressure damage the coil?

[jimthomerson]

I havn't done enough fooling around running diesel fuel in glows to make many guru-like observations. I first found out about it in an Aeromodeller annual ('52, I think). They did a bunch of fuel consumption tests on 2.5 cc engines. Two glow engines running on diesel fuel gave the best results. On one they had to leave the glow plug connected.

I have run two different K&B 40's on diesel. One would run fine after leaving the glow plug conected for maybe 30 sec or less. The other would undercompress when the battery came off. I suspect the latter engine has a thicker head gasket, but have not checked. The interesting thing is that the one engine I tached turned an APC 11 x 5 at 9,700 glow and 9,700 diesel, with the ST needle turned in about 1 1/2 turns. I've also run a glow Tower 40 on diesel but didn't tach it.

I am getting the bug to try a Fox stunt 35 on diesel fuel just to see if it will run. Will report back.

cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=34055&item=5956880255&rd=1

This is an interesting diesel on ebay. It is a Russian Poliot (Polot?) 5.6 cc. The Poliot, according to March '68 Aeromodeller was the first Russian glowplug Fox 35. I just got two of them, both pretty junky, from a guy in Australia. The diesel on ebay looks like a converison of an early example, judging by the crankcase casting. I would bid on it, but I have just bought a couple of engines from the seller and am awaiting their arrival before doing more business with him.

Jim

[downunder]

This could be your chance to be a guru

I'm not sure though how much success you'll have with the Fox because I believe their compression is only 6:1 even for the later ones. I've never checked mine so I can't say for sure though. But I've always had the urge to try out my Irvine 40RLS on diesel fuel because it feels like it's got massive compression even though it checks out at only around 11.5:1 (get it a bit wet and it'll try to take your finger off ).

[loucrane]

Downunder,

g'Day...

The South African modeler flying diesels is Keith Renecle. He was on the U So Afr F2B team last Summer (Northern Hemisphere reference -- enjoy YOUR Summer now.)

He's generated a fantastic animated F2B shedule simulation - not interactive, but by the book. Amazing!

Keith uses a quite special engine. I don't see a recognizable alias for him in here, but he has come up on the **W site. He's also active on Igor Burger's site from Slovakia.

[jimthomerson]

Lou, in response to your comment on hot restarting your PAW. My ST G20-15 will occasionally die while trying to get organized to run . Choke it once, flip it forward and it instantly restarts. This is part of my instruction to the mechanic holding the airplane.

Jim